Method and Device for Producing a SiC Solid Material

Abstract

The present invention relates to a method for producing a preferably elongated SiC solid, in particular of polytype 3C. The method according to the invention preferably includes at least the following steps: Introducing at least a first source gas into a process chamber, said first source gas including Si, introducing at least one second source gas into the process chamber, the second source gas including C, electrically energizing at least one separator element disposed in the process chamber to heat the separator element, setting a deposition rate of more than 200 ?m/h, where a pressure in the process chamber of more than 1 bar is generated by the introduction of the first source gas and/or the second source gas, and where the surface of the deposition element is heated to a temperature in the range between 1300? C. and 1800? C.

Claims

1.-42. (canceled)

43. PVT source material (922), wherein the PVT source material (922) consists of SiC particles (920), wherein the average length of the SiC particles (920) is more than 100 ?m, wherein the SiC particles have impurities of less than 10 ppm (weight) of the substance N and of less than 1000 ppb (weight), in particular of less than 500 ppb (weight), of each of the substances B, Al, P, Ti, V, Fe, Ni.

44. PVT source material according to claim 43, the SiC particles have impurities of less than 10 ppm (weight) of the substance N and of less than 1000 ppb (weight), in particular of less than 500 ppb (weight), of the sum of all of the metals Ti, V, Fe, Ni.

45. PVT source material according to claim 44, characterized in that wherein the tapped density of the SiC particles (920) is above 1.6 g/cm3.

46. PVT source material according to claim 45, characterized in that the PVT source material is produced according to a PVT source material production method for the production of PVT source material, wherein the PVT source material production method comprises the steps: Providing a source medium inside a process chamber (856), wherein providing a source medium inside a process chamber (856) comprises the steps: introducing at least a first feed-medium, in particular a first source gas, into a process chamber, said first feed medium comprises Si, in particular according to the general formula SiH.sub.4-y X.sub.y (X=[Cl, F, Br, J] and y=[0 . . . 4], wherein the first-feed medium has a purity which excludes at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, and introducing at least a second feed-medium, in particular a second source gas, into the process chamber, the second feed medium comprises C, in particular natural gas, Methane, Ethan, Propane, Butane and/or Acetylene, wherein the second-feed medium has a purity which excludes at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, introducing a carrier gas, wherein the carrier gas has a purity which excludes at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, or introducing one feed-medium in particular a source gas, into a process chamber, said feed medium comprises Si and C, in particular SiCl3(CH3), wherein the feed medium has a purity which excludes at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, introducing a carrier gas, wherein the carrier gas has a purity which excludes at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, Electrically energizing at least one SiC growth substrate (857) and preferably a plurality if SiC growth substrates (857), disposed in the process chamber to heat the SiC growth substrate/s (857) to a temperature in the range between 1300? C. and 2000? C., Setting a deposition rate, in particular of more than 200 ?m/h, for removing Si and C from the source medium and for depositing the removed Si and C as SiC, in particular as polycrystalline SiC, on the SiC growth substrate/s (857) and thereby forming a SiC solid (921) and Disaggregating the SiC solid (921) into SiC particles (920) having an average length of more than 100 ?m, wherein the PVT source material (922) is SiC of polytype 3C and/or polycrystalline SiC, wherein the average length of the SiC particles (920) is more than 2000 ?m.

47. PVT source material according to claim 46, characterized in that the SiC particles (920) comprises less than 30% (mass) of excess C or preferably less than 20% (mass) of excess C or highly preferably less than 10% (mass) of excess C or most preferably less than 5% (mass) of excess C compared to an ideal stoichiometric ration between Si and C or the SiC particles comprises less than 30% (mass) of excess Si or preferably less than 20% (mass) of excess Si or highly preferably less than 10% (mass) of excess Si or most preferably less than 5% (mass) of excess Si compared to an ideal stoichiometric ration between Si and C.

48. PVT source material lot (924), comprising at least 1 kg PVT source material (922) according to claim 45.

49. PVT source material production method for the production of PVT source material, at least comprising the steps of: Providing a source medium inside a process chamber (856), wherein providing a source medium inside the process chamber (856) comprises the steps: introducing at least a first feed-medium, in particular a first source gas, into the process chamber (856), said first feed medium comprises Si, in particular according to the general formula SiH.sub.4-y X.sub.y (X=[Cl, F, Br, J] and y=[0 . . . 4], wherein the first-feed medium has a purity which excludes at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, and introducing at least a second feed-medium, in particular a second source gas, into the process chamber (856), the second feed medium comprises C, in particular natural gas, Methane, Ethan, Propane, Butane and/or Acetylene, wherein the second-feed medium has a purity which excludes at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, and introducing a carrier gas, wherein the carrier gas has a purity which excludes at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, or introducing one feed-medium in particular a source gas, into the process chamber (856), said feed medium comprises Si and C, in particular SiCl3(CH3), wherein the feed medium has a purity which excludes at least 99.99999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, and introducing a carrier gas, wherein the carrier gas has a purity which excludes at least 99.99999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni, Electrically energizing at least one SiC growth substrate (857) and preferably a plurality if SiC growth substrates (857), disposed in the process chamber (856) to heat the SiC growth substrate/s (857) to a temperature in the range between 1300? C. and 2000? C., wherein each SiC growth substrate (857) comprises a first power connection (859a) and a second power connection (859b), wherein the first power connections (859a) are first metal electrodes (206a) and wherein the second power connections (859b) are second metal electrodes (206b), wherein the first metal electrodes (206a) and the second metal electrodes (206b) are preferably shielded from a reaction space inside the process chamber (856), and Setting a deposition rate, in particular of more than 200 ?m/h, for removing Si and C from the source medium and for depositing the removed Si and C as SiC, in particular as polycrystalline SiC, on the SiC growth substrate/s (857) and thereby forming a SiC solid (921) and Disaggregating the SiC solid (921) into SiC particles (920) having an average length of more than 100 ?m.

50. PVT source material production method according to claim 49, characterized by setting a pressure inside the process chamber (856) above 1 bar by introducing a defined amount of a mixture of the first source gas, which provides Si, and the second source gas, which provides C, into the process chamber, wherein the defined amount is an amount between 0.32 g of the mixture per hour and per cm2 of a SiC growth surface and 10 g of the mixture per hour and per cm2 of the SiC growth surface or setting a pressure inside the process chamber (856) above 1 bar by introducing a defined amount of a Si and C containing source gas into the process chamber, wherein the defined amount is an amount between 0.32 g of the Si and C containing source gas per hour and per cm2 of the SiC growth surface and 10 g of the Si and C containing source gas per hour and per cm2 of the SiC growth surface and/or increasing the electrical energizing of the at least one SiC growth substrate (857) over time, in particular to heat a surface (219, 220, 223, 224) of the deposited SiC to a temperature between 1300? C. and 1800? C. wherein the deposition rate is set to more than 500 ?m/h, in particular to more than 800 ?m/h.

51. PVT source material production method according to claim 49, characterized by depositing Si and C at the set deposition rate for more than 5 hours, in particular for more or up to 8 hours or for more or up to 12 hours or for more or up to 18 hours or preferably for more or up to 24 hours or highly preferably for more or up to 48 hours or most preferably for more or up to 72 hours and by growing the SiC solid during depositing of C and Si to a mass of more than 5 kg, in particular of more or up to 25 kg or preferably of more or up to 50 kg or highly preferably of more or up to 200 kg and most preferably of more or up to 500 kg, and to a thickness of at least 5 cm, in particular of more or up to 7 cm or preferably of more or up to 10 cm or preferably of more or up to 15 cm or highly preferably of more or up to 20 cm or most preferably of more or up to 50 cm.

52. PVT source material production method according to claim 49, characterized by a control unit (926) for setting up a feed medium supply of the one feed-medium or the multiple feed-mediums into the process chamber (956), wherein the control unit (926) is configured to set up the feed medium supply between a minimum amount of feed medium supply [mass] per min. and a maximum amount of feed medium supply [mass] per min., wherein the minimum amount of feed medium supply [mass] per min. corresponds to a deposited minimum amount of Si [mass] and a minimum amount of C [mass] at the defined growth rate, wherein the maximum amount of feed medium supply per min is up to 30% [mass] or to 20% [mass] or up to 10% [mass] or up to 5% [mass] or up to 3% [mass] higher compared to the minimum amount of feed medium supply.

53. PVT source material production method according to claim 49, characterized in that the process chamber (856) is at least surrounded by a base plate (862), a side wall section (864a) and a top wall section (864b), wherein the base plate (862) comprises at least one cooling element (868, 870, 880) for preventing heating the base plate (862) above a defined temperature and/or wherein the side wall section (864a) comprises at least one cooling element (868, 870, 880) for preventing heating the side wall section above a defined temperature and/or wherein the top wall section (864b) comprises at least one cooling element (868, 870, 880) for preventing heating the top wall section (864b) above a defined temperature and by the step preventing heating of the base plate (862) and/or the side wall section (864a) and/or the top wall section (864b) above a defined temperature, in particular 1300? C., wherein more than 50% [mass] of the side wall section (864a) and/or more than 50% [mass] of the top wall section (864b) and/or more than 50% [mass] of the base plate (862) is made of metal, in particular steel.

54. PVT source material production method according to claim 49, characterized in that a base plate and/or side wall section and/or top wall section sensor unit (890) is provided to detect temperature of the base plate (862) and/or side wall section (864a) and/or top wall section (864b) and to output a temperature signal or temperature data and/or a cooling fluid temperature sensor is provided to detect the temperature of the cooling fluid, and a fluid forwarding unit (873) is provided for forwarding the cooling fluid through the fluid guide unit (872, 874, 876), wherein the fluid forwarding unit (873) is configured to be operated in dependency of the temperature signal or temperature data provided by the base plate and/or side wall section and/or top wall section sensor unit (890) and/or cooling fluid temperature sensor (892).

55. PVT source material production method according to claim 49, characterized in that a gas outlet unit for outputting vent gas a vent gas recycling unit, wherein the vent gas recycling unit is connected to the gas outlet unit, wherein the vent gas recycling unit comprises at least a separator unit for separating the vent gas into a first fluid and into a second fluid, wherein the first fluid is a liquid and wherein the second fluid is a gas, wherein a first storage and/or conducting element for storing or conducting the first fluid is part of the separator unit or coupled with the separator unit and wherein a second storage and/or conducting element for storing or conducting the second fluid is part of the separator unit or coupled with the separator unit.

56. PVT source material production method according to claim 55, characterized in that the step of providing a source medium inside a process chamber, comprises feeding the first fluid from the vent gas recycling unit into the process chamber, wherein the first fluid comprises at least a mixture of chlorosilanes.

57. PVT source material production method according to claim 56, characterized in that the vent gas recycling unit separates with a further separator unit the first fluid into at least two parts, wherein the two parts are a mixture of chlorosilanes and a mixture of HCl, H2 and at least one C-bearing molecule, and preferably into at least three parts, wherein the three parts are a mixture of chlorosilanes and HCl and a mixture of H2 and at least one C-bearing molecule, wherein the first storage and/or conducting element connects the separator unit with the further separator unit, wherein the further separator unit is coupled with a mixture or chlorosilanes storage and/or conducting element and with a HCl storage and/or conducting element and with a H2 and C storage and/or conducting element, wherein the mixture of chlorosilanes storage and/or conducting element forms a section of a mixture of chlorosilanes mass flux path for conducting the mixture of chlorosilanes into the process chamber, wherein a Si mass flux measurement unit for measuring an amount of Si of the mixture of chlorosilanes is provided as part of the mass flux path prior to the process chamber, in particular prior to a mixing device (854), and preferably as further Si feed-medium source providing a further Si feed medium.

58. PVT source material production method according to claim 49, characterized in that the SiC growth substrate (857) has an average perimeter of at least 5 cm around a cross-sectional area (218) orthogonal to the length direction of the SiC growth substrate (857) or multiple SiC growth substrates (857) have an average perimeter per SiC growth substrate (857) of at least 5 cm around a cross-sectional area (218) orthogonal to the length direction of the respective SiC growth substrate (857).

59. Method for the production of at least one SiC crystal (17), comprising the steps providing a PVT reactor (100) for the production of at least one SiC crystal (17), wherein the PVT reactor (100) comprises a furnace unit (102), wherein the furnace unit (102) comprises a furnace housing (108) with an outer surface (242) and an inner surface (240), at least one crucible unit (106) wherein the crucible unit (106) is arranged inside the furnace housing (108), wherein the crucible unit (106) comprises a crucible housing (110), wherein the crucible housing (110) has an outer surface (112) and an inner surface (114), wherein the inner surface (114) at least partially defines a crucible volume (116), wherein a receiving space (118) for receiving a source material (120) is arranged or formed inside the crucible volume (116), wherein a seed holder unit (122) for holding a defined seed wafer (18) is arranged inside the crucible volume (116), wherein the seed wafer holder (122) holds a seed wafer (18), wherein the furnace housing inner wall (240) and the crucible housing outer wall (112) define a furnace volume (104), at least one heating unit (124) for heating the source material (120), wherein the receiving space (118) for receiving the source material (120) is at least in parts arranged above the heating unit (124) and below the seed holder unit (122), adding PVT source material (922) according to claim 45 as source material (120) into the receiving space (118), sublimating the added PVT source material (922) and depositing the sublimated SiC on the seed wafer (18) and thereby forming the at least one or exactly one SiC crystal (17).

60. A method for the production of at least one SiC crystal (17) according to claim 59, characterized in that the PVT reactor (100) comprises a crucible gas flow unit (170), wherein the crucible gas flow unit (170) comprises a crucible gas inlet tube (172) for conducting gas into the crucible volume (116), wherein the crucible gas inlet tube (172) is arranged in vertical direction below the receiving space (118) and the step conducting gas via the crucible gas flow unit (170) into the crucible housing.

61. SiC crystal produced according to claim 60. characterized in that the SiC crystal has impurities of less than 1000 ppb (weight), in particular of less than 500 ppb (weight), of the sum of all of the metals Ti, V, Fe, Ni.

62. System for carrying out the method according to claim 49.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0375] FIG. 1 schematically an example of a device for carrying out a method according to the invention, and

[0376] FIG. 2 schematically showing an example of a PVT reactor into which the SiC solid-state material according to the invention is introduced as starting material,

[0377] FIG. 3 shows an example of the CVD SiC apparatus according to the present invention, wherein also a vent gas treatment unit is shown,

[0378] FIG. 4 shows an example of the CVD SiC apparatus according to the present invention, wherein also a vent gas recovery unit is shown,

[0379] FIG. 5 shows an example of a feed gas unit according to the present invention with three gases,

[0380] FIG. 6 shows an example of the feed gas unit according to the present invention with two gases,

[0381] FIG. 7 shows an example of the CVD unit side view cross section according to the present invention,

[0382] FIG. 7a shows an example of the temperature and pressure control method for the CVD unit according to the present invention,

[0383] FIG. 8 shows an example of the CVD unit lower housing top view according to the present invention,

[0384] FIG. 9a shows an example of the deposition substrates according to the present invention,

[0385] FIG. 9b shows an example of the deposition substrates according to the present invention,

[0386] FIG. 9c shows an example of the deposition substrates according to the present invention,

[0387] FIG. 9d shows an example of the deposition substrates according to the present invention,

[0388] FIG. 9e shows an example of the deposition substrates according to the present invention,

[0389] FIG. 9f shows an example of the deposition substrates according to the present invention,

[0390] FIG. 10 shows an example of the vent gas treatment unit according to the present invention,

[0391] FIG. 11 shows an example of the vent gas recovery unit according to the present invention,

[0392] FIG. 12a shows an example of one and multiple SiC particles and a SiC produced by the CVD reactor according to the present invention,

[0393] FIG. 12b shows an example of one and multiple SiC particles and a SiC produced by the CVD reactor according to the present invention,

[0394] FIG. 12c shows an example of one and multiple SiC particles and a SiC produced by the CVD reactor according to the present invention,

[0395] FIG. 13 shows an example of a further example of a PVT reactor according to the invention,

[0396] FIG. 14 shows an example of a photo of the SiC material produced in the CVD reactor according to the invention,

[0397] FIG. 15 shows a further example of a vent gas recovery unit according to the present invention,

[0398] FIG. 16 shows an example of a preferred system setup according to the invention,

[0399] FIG. 17 shows a schematic example of an comminution unit and

[0400] FIG. 18 shows a schematic example of an etching unit.

DETAILED DESCRIPTION

[0401] FIG. 1 shows an example of a manufacturing device 850 for producing SiC material, in particular 3C-SiC material. This device 850 comprises a first feeding device 851, a second feeding device 852 and a third feeding device 853. The first feed device 851 is preferably designed as a first mass flow controller, in particular for controlling the mass flow of a first source fluid, in particular a first source liquid or a first source gas, wherein the first source fluid preferably comprises Si, in particular e.g. silanes/chlorosilanes of the general composition SiH4-mClm or organochlorosilanes of the general composition SiR4-mClm (where R=hydrogen, hydrocarbon or chlorohydrocarbon). The second feed device 852 is preferably designed as a second mass flow controller, in particular for controlling the mass flow of a second source fluid, in particular a second source liquid or a second source gas, wherein the second source fluid preferably comprises C, e.g. hydrocarbons or chlorohydrocarbons, preferably with a boiling point <100? C., particularly preferably methane. The third feed device 853 is preferably designed as a third mass flow controller, in particular for controlling the mass flow of a carrier fluid, in particular a carrier gas, wherein the carrier fluid or carrier gas preferably comprises H or H2, respectively, or mixtures of hydrogen and inert gases.

[0402] The reference sign 854 indicates a mixing device or a mixer by which the source fluids and/or the carrier fluid can be mixed with one another, in particular in predetermined ratios. The reference sign 855 indicates an evaporator device or an evaporator by which the fluid mixture which can be supplied from the mixing device 854 to the evaporator device 855 can be evaporated.

[0403] The evaporated fluid mixture is then fed to a process chamber 856 or a separator vessel, which is designed as a pressure vessel. At least one deposition element 857 and preferably several deposition elements 857 are arranged in the process chamber 856, wherein Si and C are deposited from the vaporized fluid mixture at the deposition element 857 and SiC is formed.

[0404] The reference sign 858 indicates a temperature measuring device, which is preferably provided for determining the surface temperature of the deposition element 857 and is preferably connected to a control device (not shown) by data and/or signal technology.

[0405] The reference sign 859 indicates an energy source, in particular for introducing electrical energy into the separating element 857 for heating the separating element. The energy source 859 is thereby preferably also connected to the control device in terms of signals and/or data. Preferably, the control device controls the energy supply, in particular power supply, through the deposition element 857 depending on the measurement signals and/or measurement data output by the temperature measurement device 858.

[0406] Furthermore, a pressure holding device is indicated by the reference sign 860. The pressure holding device 860 can preferably be implemented by a pressure-regulated valve or the working pressure of a downstream exhaust gas treatment system.

[0407] FIG. 2 shows an embodiment of a furnace or a furnace apparatus 100 or a PVT furnace or a PVT reactor according to the principles of the present invention, wherein the SiC solid-state material produced according to the invention, in particular 3C-SiC is introduced into this PVT furnace or PVT reactor as starting material for the production of preferably single-crystalline SiC solid-state material. The furnace 100 has a cylindrical shape and comprises a lower furnace unit or lower furnace housing 2 and an upper furnace unit or upper furnace housing 3, both typically of double-walled, water-cooled stainless steel construction, defining a furnace volume 104. The lower furnace housing 2 has a furnace gas inlet 4 and the upper furnace housing 3 has a furnace vacuum outlet or furnace vacuum outlet 204. Inside the furnace volume 104 is a crucible unit supported by crucible legs 13. Below the crucible unit is an axial heating element 214 and around the sides of the crucible unit is a radial heating element 212. Below the axial heating element 214 is a bottom insulation 8 and around the radial heating element 212 is a side insulation 9. The lower crucible housing 152 has a solid central portion surrounded by an annular trench into which the feedstock material 50 is loaded. A crucible gas inlet tube 172 seals against the lower central portion of the lower crucible housing 152, and process gases such as argon and nitrogen flow through a well in the solid central portion and are distributed into the crucible volume by a gas distribution plate 190. The crucible gas inlet tube or crucible gas inlet pipe 172 is connected to an adjustable crucible gas inlet 5 that extends through the furnace lower housing 2.

[0408] The crucible lower housing 152 also includes a growth directing element 230 used to tune the heat field and vapor flow around the sides of the crystal 17. The crystal 17 grows on a seed wafer 18 that is attached to a seed holder 122. The seed holder 122 seals against the lower inner edge of a thick-walled tubular filter or filter unit 130. The lower crucible housing 152 seals against the lower outer edge of this filter 130. The filter includes filter grooves 22 to increase surface area for removal of excess SiC2 and Si2C sublimation vapors. The filter 130 also includes a filter outer surface coating 158, 164 on its inner and outer walls to minimize permeability to Si vapor.

[0409] The upper outer edge of the filter 130 seals against a crucible lid or filter cover 107 or a crucible upper housing 154, which in turn seals against a crucible vacuum outlet tube 174. The crucible vacuum outlet tube 174 is connected to an adjustable crucible vacuum outlet 26 which extends through the furnace upper housing 3. All sealing surfaces are provided with seals 20.

[0410] The crucible gas inlet tube 172, the crucible unit, the seed holder unit 122, the filter 130, the filter cover 107, and the crucible vacuum outlet tube 174 define a crucible volume 116. The temperature of the bottom of the gas distribution plate 190 is measured by a pyrometer along the lower pyrometer sight line 7. The temperature of the top of the seed holder 122 is measured with a pyrometer along the upper pyrometer sight line 28.

[0411] The oven 100 is operated under conditions of high temperature and low pressure. First, the oven volume 104 and crucible volume 116 are purged of air with an inert gas such as argon to prevent oxidation. Then, axial heating element 214 and radial heating element 212 are used to create a thermal field inside crucible volume 116 such that the temperature of the bottom of gas distribution plate 190 is typically in the range of 2200-2400? C. and the temperature of the crystal growth surface is typically in the range of 2000-2200? C., with flat radial isotherms throughout crystal 17. The lower temperature of crystal 17 is achieved by having little or no insulation above seed crystal holder 122, allowing heat to pass through crystal 17 and seed crystal holder 122 and radiate to the water-cooled inner wall of upper furnace housing 3.

[0412] The pressure inside the crucible volume 116 during crystal growth is typically in the range of 0.1-50 Torr and is slightly lower than the pressure inside the furnace volume 104. This negative relative pressure inside the crucible volume 116 minimizes the leakage of sublimation vapors into the furnace volume 104.

[0413] Under the temperature and pressure conditions described, the starting material sublimates, releasing Si, SiC2, and Si2C vapors. The temperature gradient between the starting material 50 and the cooler crystal 17 drives these sublimation vapors toward the crystal 17, where the SiC2 and Si2C vapors become incorporated into the crystal 17 and lead to its growth. Excess SiC2 and Si2C vapors form polycrystalline deposits on the sides of the seed holder unit 122, the lower surfaces of the filter 130, and the upper inner walls of the crucible unit. In one embodiment, a low flow rate of Argon and/or nitrogen convectively assists in the thermally driven diffusion of the sublimation vapors to the crystal 17. In another embodiment, a low flow rate of nitrogen is added to dope the crystal 17 and modify its electrical properties. The gas flows radially outward from the gas distribution plate 190 and mixes with the sublimation vapors rising from the starting material 50.

[0414] All components within the furnace volume 104 are made of materials that are compatible with the operating temperatures and pressures and that do not contaminate the crystal 17. In one embodiment, the bottom insulation 8 and side insulation 9 may be made of graphite felt or graphite foam. The axial heating element 214 and the radial heating element 212 may be made of graphite, as may the crucible legs 13 and the crucible gas inlet tube 172.

[0415] The crucible base 152, the gas distribution plate or gas distribution plate 190, the wax-tumor conducting element 230, and the seed holder or seed holder 122 can be made of materials that also minimize permeation of the Si vapor. These materials include glassy infiltrated graphite, glassy carbon, pyrocarbon coated graphite, and tan-talkarbide ceramics and coatings. While graphite has a permeability of 10-1 cm/s, glassy infiltrated graphite has a permeability of 10-3 cm/s, glassy carbon has a permeability of 10-11 cm/s, and pyrocarbon coated graphite has a permeability of 10-12 cm/s. The Si vapor generated from the sublimating feedstock 50, which does not significantly permeate these components or is embedded in the crystal 17, passes between the growth guide element 230 and the crystal 17 or the growing crystal and enters the filter 130.

[0416] The filter 130 comprises a porous material having a large surface area. In one embodiment, this material is activated carbon powder with a unit surface area of about 2,000 m2/g bonded with a high temperature binder such as carbonized starch. The inner and outer walls of the filter 130 have filter outer surface coatings 158, 164 made of a material that minimizes permeation of Si vapor. In one embodiment, this material is a glassy carbon coating.

[0417] Since the Si vapor does not substantially permeate the outer surface coatings 158, 164 of the filter, the Si vapor rises further into the filter 130 and eventually condenses in the upper portion of the filter 130 due to the lower temperatures.

[0418] Thus, the present invention may relate to a method or furnace device or apparatus for PVT growth of single crystal/s, particularly SiC single crystal/s, having multiples or all of the features or steps listed below:

[0419] Providing a furnace housing capable of housing a crucible unit, heating elements and insulation, the furnace housing also having an adjustable lower crucible gas inlet tube and an adjustable upper crucible vacuum outlet tube. Providing a crucible unit and a growth guide, both of which are substantially impermeable to Si vapor. Loading the crucible unit with SiC source material.

[0420] Providing a lid assembly for the crucible unit, comprising: A large surface area annular porous filter for trapping Si sublimation vapors, having outer and inner vertical tubular surfaces coated with a coating that is substantially impermeable to Si vapor and having upper and lower outer circumferential sealing shoulders; a seed holder. A filter comprising: a plurality of filter elements coated with a coating that is substantially impermeable to Si-vapor and that has upper and lower outer circumferential sealing shoulders; a seed holder that is also substantially impermeable to Si-vapor and that is attached to and seals the lower inner opening of the filter; a SiC single crystal seed attached to the seed holder; a filter cap that seals against the upper outer circumferential sealing shoulder of the filter and that also seals against the vacuum outlet tube of the crucible.

[0421] Raising the crucible gas inlet tube and lowering the crucible vacuum outlet tube so that the crucible gas inlet tube presses and seals against the crucible unit, the crucible unit presses and seals against the lower outer circumferential sealing shoulder of the filter, the upper outer circumferential sealing shoulder of the filter presses and seals against the filter cap, and the filter cap presses and seals against the crucible vacuum outlet tube. Providing seals at all seal interfaces to improve the gas tightness of the seal interfaces.

[0422] Creating an inert vacuum in the crucible volume defined by the crucible unit and filter assembly. Creating an inert vacuum in the furnace volume via a separate furnace gas inlet and a separate furnace vacuum outlet.

[0423] Maintaining the crucible volume at a lower pressure than the furnace volume. Heating and sublimation of the starting material.

[0424] Activating the flow of carrier and dopant gases, if required, into the crucible unit. Grow the crystal while confining the Si vapor in the filter, preventing the Si vapor from penetrating and coating the crucible unit, heating elements, insulation, and any other components in the furnace volume.

[0425] Therefore, a PVT furnace is preferably provided for the production of SiC single crystal/s in which the sublimating Si vapors are prevented from penetrating the crucible housing wall, heating elements, and insulation. First, the penetration of Si vapor into these components changes their thermal properties, making it difficult to grow a good crystal because the thermal field is not stable. Second, the physical structure of these components is eventually destroyed by the Si. Therefore, the present PVT furnace avoids such infiltration.

[0426] This is preferably achieved by making the walls, in particular the inner walls of the crucible housing, impermeable to Si vapor and/or by removing the Si vapor from the gas mixture inside the crucible volume, in particular by adsorption and condensation or by deposition on a surface, which surface may be a fil-ter. This surface may be located, for example, inside the crucible unit or outside the crucible unit, but inside the furnace or even outside the entire furnace unit. In case this surface is located outside the crucible unit, fluid communication is preferably provided by means of at least one pipe or pipe system to functionally connect this surface to the crucible volume.

[0427] In this way, heating elements can be introduced into the furnace volume and generate the thermal field necessary for the growth of large diameter boules without worrying about the heating elements being destroyed by the Si vapor. In this way, the life of the insulation and the crucible housing can be drastically extended. In addition, since all of these materials have stable thermal properties, a higher yield of boules meeting specifications is possible.

[0428] In principle, the present invention also relates to the introduction of SiC solid-state material produced in accordance with the invention, in particular 3C-SiC, into a furnace apparatus 100, in particular a furnace apparatus 100 for growing crystals, in particular for growing SiC crystals, in particular monocrystalline crystals. The furnace apparatus comprises a furnace unit 104, wherein the furnace unit 102 comprises a furnace housing 108, at least one crucible unit, wherein the crucible unit is arranged within the furnace housing 108, wherein the crucible unit comprises a crucible housing 110, wherein the housing 110 comprises an outer surface 112 and an inner surface 114, wherein the inner surface 114 at least partially defines a crucible volume 116, wherein a receiving space 118 for receiving a starting material 50 is disposed or formed within the crucible volume 116, wherein a seed holder unit 122 for holding a defined seed wafer 18 is disposed within the crucible volume 116, and at least one heating unit 124 for heating the starting material 50, wherein the receiving space 118 for receiving the starting material 50 is disposed at least partially between the heating unit 124 and the seed holder unit 122.

[0429] Further, the present invention relates to a reactor 100, and more particularly to a reactor 100 for crystal growth, and more particularly for SiC crystal growth. The reactor comprises a furnace 102, the furnace 102 comprising a furnace chamber 104, at least one crucible, the crucible being arranged within the furnace chamber 104, the crucible comprising a frame structure 108, the frame structure 108 comprising a housing 110, the housing 110 comprising an outer surface 112 and an inner surface 114, the inner surface 114 at least partially forming a crucible chamber 116, wherein a receiving space 118 for receiving a source material 50 is disposed or formed within the crucible chamber 116, wherein a seed holder unit 122 for holding a defined seed wafer is disposed within the crucible chamber 116, and at least one heating unit 124 for heating the source material 50, wherein the receiving space 118 for receiving the source material 50 is disposed at least partially between the heating unit 124 and the seed holder unit 122.

[0430] Thus, the present invention relates to a method for producing a preferably elongated SiC solid, in particular of poly-type 3C. The method according to the invention preferably comprises at least the following steps: [0431] Introducing at least a first source gas into a process chamber, the first source gas comprising Si, [0432] introducing at least a second source gas into the process chamber, the second source gas comprising C, [0433] electrically energizing at least one separator element disposed in the process chamber to heat the separator element, [0434] setting a deposition rate of more than 200 ?m/h, [0435] wherein a pressure in the process chamber of more than 1 bar is generated by the introduction of the first source gas and/or the second source gas, and [0436] wherein the surface of the deposition element is heated to a temperature in the range between 1300? C. and 1700? C.

[0437] In one preferred embodiment of the present invention, FIG. 3 shows preferred main units of the SiC, in particular UPSiC, production reactor 850, in particular for the production of SiC, wherein the SiC production reactor 850 comprises according to this embodiment a SiC vent gas treatment. The separate feed gases 98 are pumped from their respective storage units to the feed gas unit 1000 where there are mixed in the required mass ratios to form the feed gas mixture 198. The feed gas mixture 198 is the fed to the CVD unit respectively CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor, 850 where the deposition reaction occurs resulting in the production of SiC rods 298 and vent gas 296. The vent gas 296 is routed to the vent gas treatment unit 500 where preferably scrubber inlet water 496 is used to remove Si-bearing compounds and HCl from the vent gas 296. The scrubber outlet water 598 containing the absorbed Si-bearing compounds and HCl is discharged and the scrubbed vent gas is preferably sent to a flare for combustion. The flare can use flare combustion gas 497 such as natural gas to achieve the combustion of the scrubbed vent gas and the resulting flare exhaust gas is discharged.

[0438] The SiC rods 298 are preferably conveyed to the comminution unit 300 where they are reduced to the required form factor, e.g., granules. Also, any heterogenous material, e.g., graphite seed rods, are preferably separated from the SiC material in such a manner as to minimize any residual contamination from this material, e.g., by heating the SiC to at least 1500? C. to burn off any residual graphite. The SiC, in particular UPSiC, granules 398 are preferably conveyed to the acid etching unit 400 where they preferably undergo an additional or alternative surface cleaning step of acid etching in an acid bath. Finally, the SiC, in particular UPSiC, etched granules 498 which have been washed and dried after the acid bath are ready for packaging and shipment.

[0439] In another preferred embodiment of the present invention, FIG. 4 shows the main units of the entire CVD SiC, in particular UPSiC, apparatus 850 in this case with vent gas recycling. Here the vent gas 296 exits the CVD unit respectively CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor, 850 and is routed to the vent gas recycling unit 600. HCl is preferably separated from the vent gas 296 and exits the vent gas recycling unit 600 as the HCl discharge 696. The recycled vent gas 698 is then fed back to the CVD unit respectively CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor, 850 thus reducing the amount of fresh feed gas mixture 198 required and reducing production costs.

[0440] Since product purity is highly beneficial, in the apparatuses described in FIGS. 3 and 2, preferably extreme care is taken not to introduce any contaminants, particularly trace metals and nitrogen or oxygen into the feed gases or any intermediate and final products. Virtually all equipment and piping is fabricated from metals, particularly various steel alloys, but they are highly preferably kept at temperatures where the entrainment of metal particles into the feed gases and products is minimized. The feed gases and products are preferably further isolated from any moisture or air that could result in nitrogen and or oxygen contamination. Nitrogen could be used as a blanket and purge gas in tanks, pipes and vessels, but it is preferably removed from any liquid feedstocks with degassing equipment and any nitrogen purge gases are preferably chased with hydrogen to minimize the possibility of nitrogen contamination.

[0441] FIG. 5 shows an example of the preparation of three separate feed gases into the feed gas mixture 1160 in the feed gas unit 1000. First, a preferably industrial C-bearing gas 1040 preferably natural gas needs to be purified of excess nitrogen to result in a C-bearing gas 111 pure enough for use in the manufacture of SiC, in particular UPSiC. Thus, the industrial C-bearing gas 1040 is highly preferably routed to a cryogenic distillation unit 105 where the low temperatures cause the industrial C-bearing gas 1040 to condense into its liquid state. Any contaminating nitrogen remains in its gaseous state and exits as N gas discharge 1070 from the top of the cryogenic distillation unit 105. Meanwhile the C-bearing liquid 1130 preferably exits from the bottom of the cryogenic distillation unit 105 and preferably pumped to a C-bearing liquid evaporator 1090 where it is evaporated into C-bearing gas 111. The C-bearing gas 111 mass flow rate is adjusted by the mass flow meter 1120 and the correct flowrate of C-bearing gas is preferably routed to the mixer respectively mixing device 854.

[0442] Already purified hydrogen gas 102 is preferably also passed through a mass flow meter 1120 and fed to the mixer respectively mixing device 854 in the correct ratio respectively a defined ratio with the C-bearing gas 111. Finally, an already purified Si-bearing liquid 106 preferably silicon tetrachloride (STC) is fed to a Si-bearing liquid evaporator 1080 and evaporated into Si-bearing gas 110. This Si-bearing gas 110 is preferably also fed to a mass flow meter 1120 and preferably sent to the mixer 114 in the correct respectively in a defined mass flow ratio to the hydrogen gas 102 and/or the C-bearing gas 111. The mixer 114 ensures that the three gases are homogenously mixed and outputs the feed gas mixture 1160.

[0443] In another preferred embodiment of the present invention shown in FIG. 6, a single C/Si-bearing liquid 1180 is evaporated in Si-bearing liquid evaporator 1080 to become C/Si-bearing gas 1200. This C/Si-bearing gas 1200 is preferably sent to mass flow meter 1120 where its mass flowrate is preferably adjusted to create the required or defined mass ratio with hydrogen gas 102 which preferably has also passed through a mass flow meter 1120. The two gases are preferably mixed into a homogenous mixture in the mixer respectively mixing device 854 and exit as the feed gas mixture 1160.

[0444] FIG. 7 shows the CVD unit respectively CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor, 850 of one preferred embodiment of the present invention. The CVD unit respectively CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor, 850 preferably comprises a fluid, in particular oil or water, cooled steel upper housing 202 or bell jar which seals, in particular by means of one or multiple gaskets, against a preferably fluid, in particular oil or water, cooled lower housing 2040 or base plate creating a deposition chamber respectively process chamber 856 which can be pressurized preferably to at least 6 bar, in particular to a pressure between 2 bar and 15 bar. The feed gas mixture 1160 preferably enters the deposition chamber respectively process chamber 856 through a plurality of feed gas inlets 2140 and the vent gas 2120 preferably exists through the gas outlet unit respectively vent gas outlet 216. Inside the deposition chamber preferably a plurality of resistively self-heated deposition substrates respectively SiC growth substrate 857 preferably made of graphite or silicon carbide or metal are provided which are connected to chucks 208 which are preferably made of graphite. The chucks 208 are in turn connected to water cooled electrodes 206 preferably made of copper which pass through the baseplate so that they can be connected to an external source of electrical power. The deposition substrates respectively SiC growth substrate 857 are preferably arranged as pairs via cross members 203 to complete an electrical circuit for resistive heating.

[0445] The purpose of the chucks 208 is to create a temperature gradient between the electrodes 206 which are in a temperature range of preferably between 850 and 400? C. and the deposition substrate respectively SiC growth substrate 857 which is preferably in temperature range of 1300 and 1600? C. The chuck 208 preferably achieves this by having a continuously reducing current flow cross section area resulting in higher and higher resistive heating. Thus, the chuck 208 preferably has a conical shape. In this manner the starting point for the deposition of CVD SiC crust 211 can be controlled preferably to a point for example midway up the chuck 208 such that the final deposition substrate respectively SiC growth substrate 857 with the deposited CVD SiC crust 211 has a structurally strong connection at the bottom and will not break or fall over.

[0446] The plurality of feed gas inlets 2140 is preferably designed to create a turbulent gas flow pattern inside the deposition chamber respectively process chamber 856 so as to maximize the contact of fresh feed gas with the surface of the CVD SiC crust 211 being deposited on the deposition substrates respectively SiC growth substrate 857. Additionally or alternatively it is possible to provide a gas turbulence generating apparatus, in particular inside the process chamber. The gas turbulence generating apparatus can be a ventilator or circulator pump. This ensures that a minimum excess of feed gas mixture 1160 is used to produce a given quantity of CVD SiC crust 211. The vent gas 2120 which contains unreacted feed gas mixture as well as altered Si-bearing gas and HCl gas is forced out of the deposition chamber respectively process chamber 856 through the vent gas outlet by the incoming feed gas mixture 1160.

[0447] FIG. 7a. shows examples of the temperature and pressure control methods for the CVD unit. A temperature control unit respectively temperature measuring device 858 is positioned such that to measure the temperature of the CVD SiC crust 211 along the temperature measurement path 209 preferably through the sight glass 213 which is preferably fluid, in particular oil or water, cooled. The temperature control unit respectively temperature measuring device 858 preferably measures the temperature of the surface of the CVD SiC crust and sends a signal to the power supply unit respectively energy source 859 to increase or decrease power to the deposition substrates respectively SiC growth substrate 857 depending on whether the temperature is below or above the desired temperature respectively. The power supply unit respectively energy source 859 is wired to the fluid, in particular oil or water cooled electrodes 206 and adjusts voltage and/or current to the fluid, in particular oil or water, cooled electrodes 206 accordingly. The deposition substrates respectively SiC growth substrate 857 are wired in pairs and have connecting cross members at the top so as to form a complete electrical circuit for the flow of current.

[0448] Pressure inside the deposition chamber respectively process chamber 856 is adjusted by means of a pressure control unit respectively pressure maintaining device 860 which senses the pressure and decreases or increases the flowrate of vent gas 2120 from the deposition chamber respectively process chamber 856.

[0449] Thus, as shown in FIGS. 7 and 7a the SiC production reactor 850 according to the present invention preferably comprises at least a process chamber 856, wherein the process chamber 856 is at least surrounded by a base plate 862, a side wall section 864a and a top wall section 864b. the reactor 850 preferably comprises a gas inlet unit 866 for feeding one feed-medium or multiple feed-mediums into a reaction space of the process chamber 856 for generating a source medium inside the process chamber 856. The base plate 862 preferably comprises at least one cooling element 868, 870, 880, in particular a base cooling element, for preventing heating the base plate 862 above a defined temperature and/or wherein the side wall section 864a preferably comprises at least one cooling element 868, 870, 880, in particular a bell jar cooling element, for preventing heating the side wall section 864a above a defined temperature and/or wherein the top wall section 864b preferably comprises at least one cooling element 868, 870, 880, in particular a bell jar cooling element, for preventing heating the top wall section 864b above a defined temperature. The cooling element 868 can be an active cooling element 870, thus the base plate 862 and/or side wall section 864a and/or top wall section 864b preferably comprises a cooling fluid guide unit 872, 874, 876 for guiding a cooling fluid, wherein the cooling fluid guide unit 872, 874, 876 is configured limit heating of the base plate 862 and/or side wall section 864a and/or top wall section 864b to a temperature below 1000? C. It is additionally possible that a base plate and/or side wall section and/or top wall section sensor unit 890 is provided to detect the temperature of the base plate 862 and/or side wall section 864a and/or top wall section 864b and to output a temperature signal or temperature data. The at least one base plate and/or side wall section and/or top wall section sensor unit 890 can be arranged as part of a surface or on a surface inside the process chamber, in particular on a surface of the base plate 862 or the side wall section 864a or the top wall section 864b. Additionally or alternatively it is possible to provide one or more base plate and/or side wall section and/or top wall section sensor unit/s 890 inside the base plate 862 or inside the side wall section 864a or inside the top wall section 864b. Additionally or alternatively it is possible to provide a cooling fluid temperature sensor 820 to detect the temperature of the cooling fluid guided through the cooling fluid guide unit 870. A fluid forwarding unit 873 can be provided for forwarding the cooling fluid through the fluid guide unit 872, 874, 876, wherein the fluid forwarding unit 873 is preferably configured to be operated in dependency of the temperature signal or temperature data provided by the base plate and/or side wall section and/or top wall section sensor unit 890 and/or cooling fluid temperature sensor 892. The cooling fluid can be oil or preferably water, wherein the water preferably comprises at least one additive, in particular corrosion inhibiter/s and/or antifouling agent/s (biocides).

[0450] Additionally or alternatively the cooling element 868 is a passive cooling element 880. Thus, the cooling element 868 can be at least partially formed by a polished steel surface 865 of the base plate 862, the side wall section 864a and/or the top wall section 864b, preferably by a polished steel surface 865 of the base plate 862, the side wall section 864a and the top wall section 864b. The passive cooling element 868 can be a coating 867, wherein the coating 867 is preferably formed above the polished steel surface 865 and wherein the coating 867 is configured to reflect heat. The coating 867 can be a metal coating or a comprises metal, in particular silver or gold or chrome, or can be an alloy coating, in particular a CuNi alloy. The emissivity of the polished steel surface 865 and/or of the coating 867 is 0.3, in particular below 0.1 and highly preferably below 0.03.

[0451] The base plate 862 can comprise at least one active cooling element 870 and one passive cooling element 880 for preventing heating the base plate 862 above a defined temperature and/or the side wall section 864a can comprise at least one active cooling element 870 and one passive cooling element 880 for preventing heating the side wall section 864a above a defined temperature and/or the top wall section 864b can comprises at least one active cooling element 870 and one passive cooling element 880 for preventing heating the top wall section 864b above a defined temperature.

[0452] The side wall section 864a and the top wall section 864b are preferably formed by a bell jar 864, wherein the bell jar 864. The bell jar 864 is preferably movable with respect to the base plate 862.

[0453] FIG. 8 shows the top view of one preferred embodiment of the lower housing 2040 or baseplate of the CVD unit respectively CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor, 850. In this case, there are a total of 24 fluid, in particular oil or water, cooled electrodes 206 arranged in two concentric rings with 8 electrodes 206 in the inner ring and 16 electrodes 206 in the outer ring. Between the two rings, a plurality of feed gas inlets 2140 is disposed. In this case there are 8 feed gas inlets 2140. The arrangement of the feed gas inlets 2140 at equal intervals between the two rings provides a maximized contacting of fresh feed gas with the deposition substrates respectively SiC growth substrate 857. The cross members 203 form an electrical connection between the two deposition substrates respectively SiC growth substrate 857 of each pair. Vent gas 2120 formed during the deposition reaction is removed from the deposition chamber respectively process chamber 856 through one or more gas outlet unit or vent gas outlets 216. This arrangement is beneficial since a plurality of deposition substrates respectively SiC growth substrate 857 matched with a plurality of feed gas inlets 2140 allows for a high volumetric deposition rate of CVD SiC crust 211 with a minimized usage of feed gas mixture 1160.

[0454] FIG. 9 demonstrates how volumetric deposition rate can be increased even further beyond just having a plurality of deposition substrates respectively SiC growth substrate 857 by increasing the starting surface area of the deposition substrates respectively SiC growth substrate 857. FIG. 9a shows a low surface area deposition substrate 857 which is typically rod shaped with a diameter of approximately 1 cm. Thus, at the begin of a run the standard surface area 219 for deposition per cm of height of the rod is 3.14 cm.sup.2/cm. Assuming a perpendicular deposition rate of 0.1 cm/hr and a run time of 70 hours, a 7 cm thick CVD SiC crust 211 deposits on the substrate 857 and the end run standard surface area 220 is therefore 47.1 cm.sup.2/cm. With this geometry the ratio of begin run to end run standard surface area is low at just 6.67%. Consequently, the average volumetric deposition rate is also low at 2.51 cm.sup.3/hr. The total volume of CVD SiC, in particular UPSiC, deposited is just 175.84 cm.sup.3.

[0455] By contrast, the high surface area substrate 222 utilized in a preferred embodiment of the present invention has a perimeter of preferably more than 5 cm and is preferably plate shaped. If a substrate 222 with width of 14 cm and thickness of 0.2 cm is utilized, it provides a begin run high surface area 223 of 28.40 cm.sup.2/cm. Again, assuming a perpendicular deposition rate of 0.1 cm/hr and a run time of 70 hrs, a 7 cm thick CVD SiC crust 211 deposits on the substrate 222 and the end run high surface area 224 is 72.36 cm.sup.2/cm. The ratio of begin run to end run high surface area is much improved to 39.25% as is the average volumetric deposition rate at 5.04. The total volume of CVD SiC, in particular UPSiC, deposited is twice as high at 352.66 cm.sup.3. Thus, it is a finding of the present invention that changing the shape of the deposition substrate the production capacity of the apparatus can be increased, in particular doubled, with relative low capital expenditure.

[0456] As a further aspect of the present invention, it has been discovered that use of high surface area resistively self-heated graphite substrates provides the benefits of cost effective heating while still allowing for sufficient separation of the substrates from the deposited CVD SiC crust 211 such that any remaining carbon contamination is within the limits required for the material to perform properly as an preferably ultrapure source material for PVT production of single crystal SiC boules. In a further preferred embodiment of the present invention, such graphite high surface area substrates are coated with a SiC, in particular UPSiC, powder via painting on and drying of an aqueous or solvent based slurry. This creates a separation layer between the substrate and the deposited CVD SiC crust 211 that allows the CVD SiC crust 211 to be easily separated from the substrate by simply cracking it off with a suitable non-contaminating tool such as a silicon carbide hammer.

[0457] In summary, in one preferred embodiment of the present invention the CVD unit respectively CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor, 850 is equipped with a plurality of high surface area substrates 222. This is beneficial because the volumetric deposition rate is maximized.

[0458] Thus, a preferred SiC production reactor 850, in particular for the production of UPSiC, in particular for the use as PVT source material comprises a process chamber 856, wherein the process chamber 856 is at least surrounded by a base plate 862, a side wall section 864a and a top wall section 864b, in particular the side wall section 864a and the top wall section 864b are parts of one bell jar 864. The preferred SiC production reactor 850 also comprises a gas inlet unit 866 for feeding one feed-medium or multiple feed-mediums into a reaction space 966 of the process chamber 856 for generating a source medium, one or multiple SiC growth substrates 857 are arranged inside the process chamber 856 for depositing SiC. Thus, the Si and C provided by means of the feed gases forms a source medium and deposits on the SiC growth substrates 857. Each SiC growth substrate 857 comprises a first power connection 859a and a second power connection 859b, wherein the first power connections 859a are first metal electrodes 206a and wherein the second power connections 859b are second metal electrodes 206b, wherein the first metal electrodes 206a and the second metal electrodes 206b are preferably shielded from a reaction space of the process chamber 856. Each SiC growth substrate 857 is coupled between at least one first metal electrode 206a and at least one second metal electrode 206b for heating the outer surface of the SiC growth substrates 857 or the surface of the deposited SiC to temperatures between 1300? C. and 1800? C., in particular by means of resistive heating and preferably by internal resistive heating. The SiC growth substrate 857 highly preferably has an average perimeter 970 of at least 5 cm and preferably of at least 7 cm and highly preferably of at least 10 cm around a cross-sectional area 218 orthogonal to the length direction of the SiC growth substrate 857 or multiple SiC growth substrates 857 have an average perimeter per SiC growth substrate 857 of at least 5 cm and preferably of at least 7 cm and highly preferably of at least 10 cm around a cross-sectional area 218 orthogonal to the length direction of the respective SiC growth substrate 857. In case of a cylindrical SiC growth substrate 857 having a circular cross section the perimeter 970 (cf. FIG. 9c) is calculated according to the following formula: perimeter=diameter??. In case of a rectangular SiC growth substrate 857 a perimeter is calculated according to the formula: perimeter=2a plus 2b. The SiC growth substrate 857 comprises or consists of SiC or C, in particular graphite, or wherein multiple SiC growth substrates 857 comprise or consist of SiC or C, in particular graphite.

[0459] The preferred shape of the cross-sectional area 218 orthogonal to the length direction of the SiC growth substrate 857 differs at least is sections and preferably along more than 50% of the length of the SiC growth substrate 857 and highly preferably along more than 90% of the length of the SiC growth substrate 857 from a circular shape. A ratio U/A between the cross-sectional area A 218 and the perimeter U 226 around the cross-sectional area 218 is higher than 1.2 1/cm and preferably higher than 1.5 1/cm and highly preferably higher than 2 1/cm and most preferably higher than 2.5 1/cm.

[0460] FIG. 9d shows an example of a SiC growth substrate 857, which is preferably formed by at least one carbon ribbon 882, in particular graphite ribbon, wherein the at least one carbon ribbon 882 comprises a first ribbon end 884 and a second ribbon end 886, wherein the first ribbon end 882 is coupled with the first metal electrode 206a and wherein the second ribbon end 886 is coupled with the second metal electrode 206b or wherein each of multiple the SiC growth substrates 857 is formed by at least one carbon ribbon 882, in particular graphite ribbon, wherein the at least one carbon ribbon 882 per SiC growth substrate 857 comprises a first ribbon end 884 and a second ribbon end 886, wherein the first ribbon end 884 is coupled with the first metal electrode 206a of the respective SiC growth substrate 857 and wherein the second ribbon end 886 is coupled with the second metal electrode 206b of the respective SiC growth substrate 857.

[0461] The carbon ribbon 882, in particular graphite ribbon, preferably comprises a curing agent.

[0462] As shown in FIG. 9e one SiC growth substrate 857 is formed by multiple rods 894, 896, 898, wherein each rod 894, 896, 898 has a first rod end 899 and a second rod end 900, wherein all first rod ends 899 are coupled with the same first metal electrode 206a and wherein all second rod ends 900 are coupled with the same second metal electrode 206b. According to the present disclosure one SiC growth substrate 857 can be made of multiple rods 894, 896, 898 as long as said rods 894, 896, 898 are connected to the same first metal electrode 206a and the second metal electrode 206b. It results from a combination of FIG. 9e and wherein each of multiple SiC growth substrates 857 is formed by multiple rods 894, 896, 898, wherein each rod 894, 896, 898 has a first rod end 899 and a second rod end 900, wherein all first rod ends 899 are coupled with the same first metal electrode 206a of the respective SiC growth substrate 857 and wherein all second rod ends 900 are coupled with the same second metal electrode 206b of the respective SiC growth substrate 857. The rods 894, 896, 898 of the SiC growth substrate 857 are preferably contacting each other or are arranged in a distance to each other. The SiC growth substrate 857 comprises three or more than three rods 894, 896, 898 or each of multiple SiC growth substrates 857 comprises three or more than three rods 894, 896, 898.

[0463] FIG. 9f shows a further preferred embodiment, wherein the SiC growth substrate 857 is formed by at least one metal rod 902, wherein the metal rod 902 has a first metal rod end 904 and a second metal rod end 906, wherein the first metal rod end 904 is coupled with the first metal electrode 206a and wherein the second metal rod end 906 is coupled with the second metal electrode 206b. Alternatively each of multiple SiC growth substrates 857 is formed by at least one metal rod 902, wherein each metal rod 902 has a first metal rod end 904 and a second metal rod end 906, wherein the first metal rod end 904 is coupled with the first metal electrode 206a of the respective SiC growth substrate 857 and wherein the second metal rod end 906 is coupled with the second metal electrode 206b of the respective SiC growth substrate 857.

[0464] The metal rod 902 preferably comprises a coating 903, wherein the coating 903 preferably comprises SiC and/or wherein the coating 903 preferably has a thickness of more than 2 ?m or preferably of more than 100 ?m or highly preferably of more than 500 ?m or between 2 ?m and 5 mm, in particular between 100 ?m and 1 mm, or of less than 500 ?m.

[0465] FIG. 10 shows the vent gas treatment unit 500 of the CVD SiC, in particular UPSiC, apparatus 850 in one preferred embodiment of the present invention where the vent gas 296 is treated and discharged rather than recycled. The vent gas 296 is routed from the CVD unit respectively CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor, 850 to the filter unit 502 of the vent gas treatment unit 500 where any particulates that may have formed in the gas are removed. The filtered vent gas 504 is then preferably sent to the scrubber unit 506 where it is preferably absorbed into scrubber inlet fluid, in particular water 496. Scrubber outlet water 598 preferably containing any Si-bearing compounds and HCl then exits the scrubber, in particular to be processed for disposal. The scrubbed vent gas 512 is then preferably sent to the flare unit 514 where it is combusted with flare combustion gas 497, preferably natural gas, and the resulting flare exhaust gas 596 is suitable for discharge.

[0466] FIG. 11 shows an example of a vent gas recycling unit 600 of the CVD SiC, in particular UPSiC, apparatus 850 in another preferred embodiment of the present invention where the vent gas 296 is recycled rather than treated and discharged. The vent gas 296 is routed from the CVD unit respectively CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor 850 to the cold distillation unit 602 which preferably operates in a temperature range of ?30? C. to ?196? C. In this temperature range any Si-bearing gases condense and exit the bottom of the distillation unit 602 as an Si-bearing liquid mixture 604. This Si-bearing liquid mixture 604 is periodically routed to a HMW distillation unit 606 which operates in a temperature range that evaporates the Si-bearing liquid 604 while any heavy-molecular-weight compounds remain liquid and exit the bottom of the HMW distillation unit 606 as the HMW liquids discharge 608.

[0467] Meanwhile, the Si-bearing gas mixture 620 is exiting the top of the HMW distillation unit 606 and passing through an Si detector unit 622 which determines the mass of Si present. The Si detector unit 622 communicates this information to the central process control unit of the CVD SiC, in particular UPSiC, apparatus 850 which then adjusts the mass flow meter 1120 on the Si-bearing gas 110 line such that the total mass of Si coming from the Si-bearing gas mixture 620 and the Si-bearing gas 110 is in the desired ratio with the total mass of C coming from the H/C-bearing gas mixture 616 and the C-bearing gas 111. Meanwhile, cold distillation gas 610 is exiting the top of the top of the cold distillation unit 602 and is sent to the cryogenic distillation unit which preferably operates in a temperature range between ?140? C. and ?40? C. in this temperature range, the H/C-bearing gas mixture 616 remains in the gaseous form but the HCl condenses and is removed from the bottom of the Cryogenic distillation unit 612 as the HCl liquid discharge 696 to be further processed for disposal.

[0468] The H/C-bearing gas mixture 616 is passed through an H/C detector unit which determines the masses of H and C present. The H/C detector unit communicates this information to the central process control unit of the CVD SiC, in particular UPSiC, apparatus 850 which then adjusts the mass flow meters 1120 on the hydrogen gas 102 line and the C-bearing gas 111 line such that the mass ratios of H, C, and Si are all in the desired range.

[0469] FIG. 12a shows the length of a SiC particle 920 which is defined in analogous manner to Fmax according to ISO 13322-2. The SiC particle 920 is produced in a SiC production reactor 850 according to the present invention and disaggregated afterwards. The term average length defines that the length of multiple particles is added and divided through the number of particles, the result is the average length of said multiple particles.

[0470] FIG. 12b shows a plurality of SiC particles 920 of PVT source material produced according to the present invention. The plurality of SiC particles 920 is provided as batch and preferably has an apparent density above 1.4 g/cm.sup.3, in particular above 1.6 g/cm.sup.3.

[0471] FIG. 12c shows a SiC solid 921. The SiC solid 921 forms a boundary surface 930 in a defined distance to a central axis of the SiC solid 921, and wherein the SiC solid 921 forms an outer surface 224, wherein the outer surface 224 and the boundary surface 930 are formed in a distance to each other. The distance preferably extends orthogonal to the central axis, wherein an average distance between the outer surface 224 and boundary surface 930 is preferably larger compared to an average distance between the boundary surface 930 and the central axis. The average distance between the outer surface 224 and boundary surface 930 is preferably calculated in the following manner: (shortest distance (in radial direction) plus longest distance (in radial direction))/2.

[0472] FIG. 13 shows a further example of a PVT reactor 100 used according to the present invention. It has to be understood that the PVT reactor 100 shown in FIG. 2 is based on the same technological principle, thus features from one of said PVT reactors 100 (FIG. 2 or FIG. 13) can be exchanged or added to the other PVT reactor 100. It has also to be understood that the CVD reactors 850 shown in FIGS. 1, 7 and 8 are based on the same technological principle, thus features from one of said CVD reactors 850 (FIG. 1 or FIG. 6 or FIG. 7) can be exchanged or added to the other CVD reactor 850.

[0473] Furthermore, the system according to the present invention preferably comprises a CVD reactor according to any of FIG. 1, 7 or 8 and a PVT reactor according to FIG. 2 or 13.

[0474] the furnace apparatus 100 preferably comprises a crucible gas flow unit 170. The crucible gas flow unit 170 preferably comprises a crucible gas inlet tube 172 for conducting gas into the crucible volume 116, wherein the crucible gas inlet tube 172 is highly preferably arranged in vertical direction below the receiving space 118. The receiving space 118 is located between the crucible gas inlet tube 172 and the seed holder unit 122 for conducting gas flow around the receiving space 118 and/or through the receiving space 118.

[0475] A source-material-holding-plate 278 can be provided, wherein the source-material-holding-plate 278 comprises an upper surface 370 preferably forming a bottom section of the receiving space 118 and a lower surface 372 preferably forming a source-material-holding-plate-gas-flow-path-boundary-section. The source-material-holding-plate 278 preferably comprises multiple through holes 282, in particular more than 10 or preferably more than 50 or highly preferably up to 100 or most preferably up to or more than 1000, wherein the multiple through holes 282 extend from the upper surface 370 of the source-material-holding-plate 278 through a main body of the source-material-holding-plate 278 to the lower surface 372 of source-material-holding-plate 278. At least the majority of the multiple through holes 282 has a diameter of less than 12 mm, in particular less than 10 mm and preferably less than 6 mm and highly preferably less than 2 mm and most preferably of 1 mm or less than 1 mm. The number of through holes 282 through the main body of the source-material-holding-plate 278, preferably depends on the surface size of the upper surface 370 of the source-material-holding-plate 278, wherein at least one though hole 282 is provided per 10 cm.sup.2 surface size of the upper surface 370. The number of through holes 282 per 10 cm.sup.2 is preferably higher in a radially outer section of the source-material-holding-plate 278 compared to a radially inner section of the source-material-holding-plate, wherein the radially inner section extends up to 20% or 30% or 40% or 50% of the radial extension of the source-material-holding-plate 278, wherein the radially outer section of the source-material-holding-plate 278 extends between the radially inner section and the radial end of the source-material-holding-plate 278. The lower surface 372 of the source-material-holding-plate 278 preferably forms together with a bottom wall section 207 of the crucible housing 110 a gas-guide-gap 280 or gas-guide-channel for guiding gas from the crucible gas inlet tube 172 to the receiving space 118 or around the receiving space 118, in particular to the through holes 282 of the source-material-holding-plate 278. Additionally or alternatively a pressure unit 132 for setting up a crucible volume pressure P1 inside the crucible volume 116 is provided, wherein the pressure unit 132 is configured to cause crucible volume pressure P1 above 2666.45 Pa and preferably above 5000 Pa or in a range between 2666.45 Pa and 50000.00 Pa. A crucible gas outlet tube 174 for removing gas from the crucible volume 116 is preferably provided, wherein the crucible gas inlet tube 172 is arranged in gas flow direction preferably before a filter unit 130 and wherein the crucible gas outlet tube 174 is arranged in gas flow preferably direction after a filter unit 130. The filter unit 130 can be arranged inside the crucible volume 116 between the crucible gas inlet tube 172 and the crucible gas outlet tube 174 for capturing at least Si.sub.2C sublimation vapor, SiC.sub.2 sublimation vapor and Si sublimation vapor. The filter unit 130 preferably forms a filter-unit-gas-flow-path 147 from the filter input surface 140 to the filter output surface 142, wherein the filter gas flow path is part of the gas flow path between the crucible gas inlet tube 172 and the crucible gas outlet tube 174, wherein the filter unit 130 preferably has a height S1 and wherein the filter-unit-gas-flow-path 147 through the filter unit 130 preferably has a length S2, wherein S2 is at least 2 times, in particular 10 times, longer compared to S1. The filter unit 130 forms preferably a filter outer surface 156, wherein the filter outer surface 156 comprises a filter outer surface covering element 158, wherein the filter outer surface covering element 158 is a sealing element, wherein the sealing element is preferably a filter coating 135, wherein the filter coating 135 is generated at the filter outer surface 156 or attached to the filter outer surface 156 or forms the filter outer surface 156. The filter coating 135 of the filter outer surface 156 is preferably formed by a layer of pyrocarbon which has a thickness of more than 10 ?m, in particular of more than or of up to 20 ?m or of more than or of up to 50 ?m or of more than or of up to 100 ?m of more than or of up to 200 ?m of more than or of up to 500 ?m, and/or wherein the filter coating 135 of the filter outer surface 156 is formed by a layer of glassy carbon which has a thickness of more than 10 ?m, in particular of more than or of up to 20 ?m or of more than or of up to 50 ?m or of more than or of up to 100 ?m of more than or of up to 200 ?m of more than or of up to 500 ?m.

[0476] FIG. 14 shows a microscopic image of PVT source material produced according to the present invention. It can be seen from the figure that the produces PVT source material is preferably a polycrystalline SiC material.

[0477] The PVT source material can be provided as SiC particles 920, wherein the average length of the SiC particles is more than 100 ?m, wherein the SiC particles have impurities of less than 10 ppm (weight) of the substance N and of less than 1000 ppb (weight), in particular of less than 500 ppb (weight), of each of the substances B, Al, P, Ti, V, Fe, Ni.

[0478] Alternatively, the PVT source material can be provided as SiC solid 921 having a mass of more than 1 kg, a thickness of at least 1 cm and preferably of more than 5 cm or highly preferably of more than 10 cm or most preferably of more than 15 cm, and a length of more than 25 cm or preferably of more than 50 cm. The SiC solid 921 has impurities of less than 10 ppm (weight) of the substance N and of less than 1000 ppb (weight), in particular of less than 500 ppb (weight), of each of the substances B, Al, P, Ti, V, Fe, Ni.

[0479] FIG. 15 shows a further example of a vent gas recycling unit 600. According to this example the vent gas recycling unit 600 is attached or coupled to at least von gas outlet unit for outputting vent gas 216 of at least one SiC production reactor 850.

[0480] The vent gas recycling unit 600 preferably comprises at least a separator unit 602 for separating the vent gas 216 into a first fluid 962 and into a second fluid 964. The first fluid 962 is preferably a liquid and the second fluid 964 is preferably a gas. A first storage and/or conducting element for storing or conducting the first fluid 624 is part of the separator unit 602 or coupled with the separator unit 602 and a second storage and/or conducting element 626 for storing or conducting the second fluid 964 is part of the separator unit 602 or coupled with the separator unit 602.

[0481] The vent gas recycling unit 600 preferably comprises a further separator unit 612 for separating the first fluid into at least two parts, wherein the two parts are a (a) mixture of chlorosilanes and (b) a mixture of HCl, H2 and at least one C-bearing molecule. Alternatively the further separator unit 612 separates the first fluid into at least three parts, wherein the three parts are (a) a mixture of chlorosilanes and (b) HCl and (c) a mixture of H2 and at least one C-bearing molecule. The first storage and/or conducting element 624 preferably connects the separator unit 602 with the further separator unit 612. The further separator unit 612 is preferably coupled with a mixture of chlorosilanes storage and/or conducting element 628 and with a HCl storage and/or conducting element 630 and with a H2 and C storage and/or conducting element 632. The mixture of chlorosilanes storage and/or conducting element 628 preferably forms a section of a mixture of chlorosilanes mass flux path for conducting the mixture of chlorosilanes into the process chamber 856, in particular to a mixing device 854.

[0482] A Si mass flux measurement unit 622 for measuring an amount of Si of the mixture of chlorosilanes can be provided as part of the mass flux path prior to the process chamber 856, in particular prior to a mixing device 854. The Si mass flux preferably serves as further Si feed-medium source providing a further Si feed medium. It has to be noted that the mixture of chlorosilanes preferably can be a random mixture respectively can have a random composition of different chlorosilanes. The mixture of chlorosilanes storage and/or conducting element 628 alternatively forms a section of a mixture of chlorosilanes mass flux path for conducting the mixture of chlorosilanes into a further process chamber 952 of a further SiC production reactor 950, in particular via fluid path 948.

[0483] The H2 an C storage and/or conducting element 632 preferably forms a section of a H2 and C mass flux path for conducting the H2 and the at least one C-bearing molecule into the process chamber 850. A C mass flux measurement unit 618 for measuring an amount of C of the mixture of H2 and the at least one C-bearing molecule is preferably provided as part of the H2 and C mass flux path prior to the process chamber 856, in particular prior to a mixing device 854, and preferably as further C feed-medium source providing a further C feed medium. The H2 an C storage and/or conducting element 632 alternatively forms a section of a H2 and C mass flux path for conducting the H2 and the at least one C-bearing molecule into a further process chamber 952 of a further SiC production reactor 950, in particular via fluid path 949.

[0484] The second storage and/or conducting element 626 preferably forms a section of the H2 and C mass flux path for conducting the second fluid, which comprises H2 and at least one C-bearing molecule, into the process chamber 856, wherein the second storage and/or conducting element 626 and the H2 an C storage and/or conducting element 632 are preferably fluidly coupled.

[0485] The second storage and/or conducting element 626 preferably forms a section of a further H2 and C mass flux path for conducting the second fluid, which comprises H2 and C, into the process chamber 856. A further C mass flux measurement unit for measuring an amount of C of the second fluid is preferably provided as part of the further H2 and C mass flux path prior to the process chamber 856, in particular prior to a mixing device 854. The mixing device 854 can be part of the gas inlet unit 866 or can belong to the gas inlet unit 866 or can be a sub unit of the gas inlet unit 866. The second storage and/or conducting element 626 can be coupled with a flare unit for burning the second fluid.

[0486] The separator unit 602 is highly preferably configured to operate at a pressure above 5 bar and a temperature below ?30? C.

[0487] A first compressor 634 for compressing the vent gas to a pressure above 5 bar can be provided as part of the separator unit 602 or in a gas flow path between the gas outlet unit 216 and the separator unit 602. The further separator unit 612 is highly preferably configured to operate at a pressure above 5 bar and a temperature below ?30? C. and/or a temperature above 100? C. A further compressor 636 for compressing the first fluid to a pressure above 5 bar can be provided as part of the further separator unit 612 or in a gas flow path between the separator unit 602 and the further separator unit 612. The further separator unit 612 highly preferably comprises a cryogenic distillation unit, wherein the cryogenic distillation unit is preferably configured to be operated at temperatures between ?180C? and ?40C?.

[0488] A control unit 929 for controlling fluid flow of a feed-medium or multiple feed-mediums is preferably part of the SiC production reactor 850, wherein the multiple feed-mediums comprise the first medium, the second medium, the third medium and the further Si feed medium and/or the further C feed medium via the gas inlet unit into the process chamber 856. The further Si feed medium highly preferably consists of at least 95% [mass] or at least 98% [mass] or at least 99% [mass] or at least 99.9% [mass] or at least 99.99% [mass] or at least 99,999% [mass] of a mixture of chlorosilanes. Additionally or alternatively the further C feed medium preferably comprises the at least one C-bearing molecule, H2, HCl and a mixture of chlorosilanes. The further C feed medium highly comprises the at least one C-bearing molecule, HCl, H2 and a mixture of chlorosilanes, wherein the further C feed medium comprises of at least 3% [mass] or preferably at least 5% [mass] or highly preferably at least 10% [mass] of C respectively the at least one C-bearing molecule and wherein the further C feed medium comprises up to 10% [mass] or preferably between 0.001% [mass] and 10%[mass], highly preferably between 1% [mass] and 5%[mass], of HCl, and wherein the further C feed medium comprises more than 5% [mass] or preferably more than 10% [mass] or highly preferably more than 25% [mass] of H2 and wherein the further C feed medium comprises more than 0.01% [mass] and preferably more than 1% [mass] and highly preferably between 0.001% [mass] and 10%[mass] of the mixture of chlorosilanes.

[0489] Additionally, a heating unit 954 can be arranged in fluid flow direction between the further separator unit and the gas inlet unit, in particular as part of the further separator unit 612, for heating the mixture of chlorosilanes to transform the mixture of chlorosilanes from a liquid form into a gaseous form.

[0490] FIG. 16 show an example of a system 999 according to the present invention. The inventive system 999 comprises at least one SiC production reactor 850 and one PVT reactor 100, wherein the SiC production reactor 850 produces SiC source material which is used in the PVT reactor 100 to produce monocrystalline SiC.

[0491] According to FIG. 16 it is additionally or alternatively possible that multiple SiC production reactors 850, 950 are provided. It is additionally or alternatively possible that multiple PVT reactors 100 are provided. Furthermore, it is possible that a SiC production reactor 850 comprises a vent gas recycling unit 600. It is alternatively possible that multiple SiC production reactors 850, 950 are connected through a vent gas recycling unit 600. Thus, the vent gas of a first SiC production reactor 850 can be recycled and used as source material for the other SiC production reactor 950. Thus, at least some output of the vent gas recycling unit 600, in particular the Si, C and H2 components, can be used as feed gas for the same or another SiC production reactor 850. Arrow 972 alternatively indicates that the output of the vent gas recycling unit 600 can be used for the CVD reactor 850 which emitted the vent gas.

[0492] Thus, due to the before mentioned system the present invention provides a method for the production of at least one SiC crystal. Said method preferably comprises the steps: Providing a CVD reactor 850 for the production of SiC of a first type, introducing at least one source gas, in particular a first source gas, in particular SiCl3(CH3), into a process chamber 856 for generating a source medium, wherein the source medium comprises Si and C, introducing at least one carrier gas into the process chamber 856, the carrier gas preferably comprising H, electrically energizing at least one SiC growth substrate 857 disposed in the process chamber 856 to heat the SiC growth substrate 857, wherein the surface of the SiC growth substrate 857 is heated to a temperature in the range between 1300? C. and 1800? C., depositing SiC of the first type onto the SiC growth substrate 857, in particular at a deposition rate of more than 200 ?m/h, wherein the deposited SiC is preferably polycrystalline SiC, removing the deposited SiC of the first type from the CVD reactor 850, preferably transforming the removed SiC into fragmented SiC of the first type or into one or multiple solid bodies SiC of the first type, providing a PVT reactor 100 for the production of SiC of a second type, adding the preferably fragmented SiC of the first type or adding one or multiple solid bodies of SiC of the first type as source material 120 into a receiving space 118 of the PVT reactor 100, sublimating the SiC of the first type inside the PVT reactor 100 and depositing the sublimated SiC on a seed wafer 18 as SiC of the second type.

[0493] The PVT reactor 100 hereby preferably comprises a furnace unit 102, wherein the furnace unit 102 comprises a furnace housing 108 with an outer surface 242 and an inner surface 240, at least one crucible unit 106, wherein the crucible unit 106 is arranged inside the furnace housing 108, wherein the crucible unit 106 comprises a crucible housing 110, wherein the crucible housing 110 has an outer surface 112 and an inner surface 114, wherein the inner surface 114 at least partially defines a crucible volume 116, wherein a receiving space 118 for receiving a source material 120 is arranged or formed inside the crucible volume 116, wherein a seed holder unit 122 for holding a defined seed wafer 18 is arranged inside the crucible volume 116, wherein the seed wafer holder 122 holds a seed wafer 18, wherein the furnace housing inner wall 240 and the crucible housing outer wall 112 define a furnace volume 104, at least one heating unit 124 for heating the source material 120, wherein the receiving space 118 for receiving the source material 120 is at least in parts arranged above the heating unit 124 and below the seed holder unit 122.

[0494] FIG. 17 shows a comminution unit 699.

[0495] At the end of the deposition process, after purging the reactor and rendering inert, the bell jar can be lifted and the thick rods removed from the CVD reactor. This process is widely known as harvesting.

[0496] The harvested rods have to be transferred into a shape suitable for PVT processing. This can either be a cut rod segment or broken chips and chunks of various sizes.

[0497] Different methods to comminute hard and brittle solids like silicon carbide into smaller pieces are known. Most common is the mechanical approach. SiC rods or larger fragments thereof are fed into a crusher, which is preferably a jaw crusher or a roll crusher. Adjustable machine parameters as gap distance, rotational speed or swing amplitude are determining the final particle size distribution. To avoid large amounts of fines and/or high contamination level, a multiple stage application of crusher machines is possible. Crushing machines are ordered in series, where the outlet of one crusher is connected, either directly or indirectly via a transportation device like belt conveyor or vibrating chutes, with the feed opening of a subsequent crusher with differing machine parameters. Finally, the comminuted pieces have to be classified to remove undersize material and to return oversize material to the comminution process.

[0498] Alternative crushing methods are also applicable. A known method is thermal cracking. A rod of hard, brittle material is heated and cooled down with a high temperature gradient, e.g. by rapid dipping into a cold fluid.

[0499] Typically, mechanically driven screening machines are used to classify irregular pieces of solid material into size classes. A summary of used screening machines is described in US2018169704. The mechanical approach to classify pieces of solid material can be extended by a more flexible optoelectronic method, which was disclosed in US 2009/120848.

[0500] The comminution process excavates the starting substrate, if graphite is used as starting material, because the interface between starting substrate and silicon carbide growth layer acts as a predetermined breaking point. This fact can be used to easily remove the graphite substrate from the product by annealing/heating to at least 900? C. to 1400? C. in the presence of air or any gas mixture enriched with oxygen. The surface color changes from grey to blueish-brownish, caused by thin layers (100-300 nm) of silicon oxides. This can easily be removed by an acid treatment.

[0501] FIG. 18 shows an etching unit 799. The etching unit preferably comprises the following units:

[0502] An etching basin 800, water basins (water cascade) 801, a drying unit 802, a packaging unit 803. Reference number 810 indicates etched SiC and reference number 811 indicates acid-free SiC and reference number 812 indicates dried SiC and reference number 813 indicates packed SiC, in particular according to a specification.

[0503] Thus, the present invention relates to a method for producing a preferably elongated SiC solid, in particular of polytype 3C. The method according to the invention preferably comprises at least the following steps: [0504] Introducing at least a first source gas into a process chamber, said first source gas comprising Si, [0505] introducing at least one second source gas into the process chamber, the second source gas comprising C, [0506] electrically energizing at least one separator element disposed in the process chamber to heat the separator element, [0507] setting a deposition rate of more than 200 ?m/h, [0508] wherein a pressure in the process chamber of more than 1 bar is generated by the introduction of the first source gas and/or the second source gas, and [0509] wherein the surface of the deposition element is heated to a temperature in the range between 1300? C. and 1800? C.

TABLE-US-00003 List of reference signs 2 Furnace housing (lower part) 3 Furnace housing (upper part) 4 Furnace gas inlet 5 Crucible gas inlet 7 Crucible gas inlet connection piece 8 Bottom insulation 9 Side insulation 13 Crucible leg 17 Crystal 18 Seed wafer 20 Seals 22 Filter grooves or pores 26 Crucible vacuum outlet 28 Pyrometer sight line 50 Source material 100 Furnace respectively furnace apparatus respectively PVT reactor 102 Hydrogen gas 104 Furnace volume 105 Cryogenic distillation unit 106 Si-bearing liquid 107 Crucible lid respectively filter cover 108 furnace housing 110 crucible housing 112 outer surface 116 crucible volume 118 receiving space 120 PVT source material 122 Seed holder 130 Filter 132 pressure unit 135 filter coating 140 filter input surface 142 filter output surface 147 filter-unit-gas-flow-path 152 Crucible base 156 filter outer surface 158 Filter outer surface coating 164 Filter outer surface coating 170 crucible gas flow unit 172 Crucible gas inlet tube 174 Crucible vacuum outlet tube 198 Feed gas mixture 202 Upper housing 203 Cross member 204 Oven vacuum outlet 206a first electrode 206b second electrode 208 Chuck 209 Temperature measurement path 212 radial heating element 211 CVD SiC crust or SiC solid 213 Sight glass 214 heating element 216 Vent gas outlet respectively gas outlet unit 218 cross-sectional area 219 Begin run standard surface area 220 End run standard surface area 222 High surface area substrate 223 Begin run high surface area 224 End run high surface area 226 perimeter 230 growth guide element 231 top of growth guide element 278 source-material-holding-plate 280 gas-guide-gap 282 through holes 296 Vent gas 298 UPSIC rods 300 Comminution unit 370 upper surface of source-material- holding-plate 372 lower surface of source-material- holding-plate 398 UPSiC granules 400 Acid etching unit 496 Scrubber inlet water 497 Flare combustion gas 498 UPSiC etched granules 500 Vent gas treatment unit 502 Vent gas filter unit 504 Filtered vent gas 506 Scrubber unit 512 Scrubbed vent gas 514 Flare unit 596 Flare exhaust gas 598 Scrubber outlet water 600 Vent gas recycling unit 602 Cold distillation unit respectively separator unit 604 Si-bearing liquid mixture 606 HMW distillation unit 608 HMW liquids discharge 610 Cold distillation gas 612 Cryogenic distillation unit or further separator unit 616 H/C-bearing gas mixture 618 H/C detector unit respectively C mass flux measurement unit 620 Si-bearing gas mixture 622 Si detector unit respectively Si mass flux measurement unit 624 first storage and/or conducting element 626 second storage and/or conducting element 628 mixture of chlorosilanes storage and/or conducting element 630 HCl storage and/or conducting element 632 H2 and C storage and/or conducting element 634 first compressor 636 further compressor 696 HCl liquid discharge 698 Recycled vent gas 699 Comminution Unit 700 Precrusher 701 Crusher 702 Screening machine (undersize removal) 703 Screening machine (oversize removal) 704 Annealing furnace 710 precrushed SiC 711 crushed SiC (all particle sizes) 712 crushed SiC w/o undersized particles (1 . . . 30 mm) 713 undersized SiC (0 . . . 1 mm) 714 oversized SiC, return to crushing (>12 mm) 715 SiC product (1 . . . 12 mm) 716 annealed SiC (graphite free; 1 . . . 12 mm) 799 etching unit 800 etching basin 801 water basins (water cascade) 802 drying unit 803 packaging unit 810 etched SiC 811 acid-free SiC 812 dried SiC 813 packed SiC according to specification 850 manufacturing device or CVD unit or CVD reactor respectively SiC production reactor, in particular SiC PVT source material production reactor 851 first feeding device respectively first feed-medium source 852 second feeding device respectively second feed-medium source 853 third feeding device respectively third feed-medium source respectively carrier gas feed-medium source 854 mixing device 855 evaporator device 856 process chamber 857 separating element or SiC growth substrate or deposition substrate 858 temperature measuring device or temperature control unit 859 Energy source, especially power supply 859a first power connection 859b second power connection 860 Pressure maintaining device or pressure control unit 861 outer surface of SiC growth substrate or SiC growth surface 862 base plate 864 bell jar 864a side wall section 864b top wall section 865 metal surface 866 gas inlet unit 867 reflective coating 868 cooling element 870 active cooling element 872 cooling fluid guide unit 873 fluid forwarding unit 874 pipe 876 hollow space between an inner and an outer wall 880 passive cooling element 882 ribbon 884 first ribbon end 886 second ribbon end 890 base plate and/or side wall section and/or top wall section sensor unit 892 cooling fluid temperature sensor 894 first rod 896 second rod 898 third rod 899 first rod end 900 second rod end 902 metal rod 903 coating of the SiC growth substrate 904 first metal rod end 906 second metal rod end 920 SiC particle 921 SiC solid 922 PVT source material 924 PVT source material lot 926 control device or control unit 930 boundary surface 932 cross-sectional area 934 core member 948 additional or alternative path to further SiC production reactor 950 949 additional or alternative further path to further SiC production reactor 950 950 further SiC production reactor respectively CVD reactor for the production of SiC 952 further process chamber of further SiC production reactor 954 heating unit 956 mixture of chlorosilanes 958 HCl 959 further processing step to convert HCl to chlorosilanes 960 mixture of H2 and at least one C-bearing molecule 962 first fluid 964 second fluid 966 reaction space 968 forwarding of PVT source material produced in SiC production reactor to PVT reactor 970 perimeter 972 arrow 999 System 1000 feed gas unit 1040 industrial C-bearing gas 1070 N gas discharge 1080 Si-bearing liquid evaporator 1090 C-bearing liquid evaporator 1120 Mass flow meter 1130 C-bearing liquid 1160 Feed gas mixture 1180 C/Si-bearing liquid 1200 C/Si-bearing gas 2040 Lower housing 2120 Vent gas 2140 Feed gas inlet CA central axis PL particle length