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 1700 C.g. 1)

Claims

1. Method for producing a preferably elongated SiC solid, in particular of polytype 3C, at least comprising the steps of: Introducing at least a first source gas into a process chamber, said first source gas comprising Si, introducing at least a second source gas into the process chamber, the second source gas comprising 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, 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 wherein the surface of the deposition element is heated to a temperature in the range between 1300 C. and 1700 C.

2. Method according to claim 1, characterized by the step of Introducing at least one carrier gas into the process chamber, the carrier gas preferably comprising H.

3. Method for producing a preferably elongated SiC solid, in particular of polytype 3C, comprising at least the steps of: introducing at least one source gas, in particular a first source gas, in particular SiCl3(CH3), into a process chamber, the source gas comprising Si and C, introducing at least one carrier gas into the process chamber, the carrier gas preferably comprising H, 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, wherein a pressure of more than 1 bar is generated in the process chamber by the introduction of the source gas and/or the carrier gas, and wherein the surface of the deposition element is heated to a temperature in the range between 1300 C. and 1700 C.

4. Method according to claim 1, characterized in that a pressure in the process chamber of between 2 bar and 10 bar is generated by introducing the first source gas and/or the second source gas, preferably a pressure in the process chamber of between 4 bar and 8 bar is generated by introducing the first source gas and/or the second source gas, particularly preferably a pressure in the process chamber of between 5 bar and 7 bar, in particular of 6 bar, is generated by introducing the first source gas and/or the second source gas.

5. Method according to claim 1, characterized in that the surface of the deposition element is heated to a temperature in the range between 1450 C. and 1700 C., in particular to a temperature in the range between 1500 C. and 1600 C.

6. Method according to claim 1, characterized in that the first source gas is introduced into the process chamber via a first supply means, and the second source gas is introduced into the process chamber via a second supply means, or the first source gas and the second source gas are mixed before being introduced into the process chamber and are introduced into the process chamber via a supply device, wherein the source gases are introduced into the process chamber in a molar ratio Si:C of Si=1 and C=0.8 to 1.1 and/or an atomic ratio Si:C of Si=1 and C=0.8 to 1.1.

7. Method according to claim 6, characterized in that the carrier gas comprises H wherein the source gases and the carrier gas are introduced into the process chamber in a molar ratio Si:C:H of Si=1 and C=0.8 to 1.1 and H=2-10, in particular in a molar ratio Si:C:H of Si=1 and C=0.9 to 1 and H=3-5, and/or an atomic ratio Si:C:H of Si=1 and C=0.8 to 1.1 and H=2-10, in particular in an atomic ratio Si:C:H of Si=1 and C=0.9 to 1 and H=3-5.

8. Method according to claim 1, characterized in that the deposition rate is set in the range between 300 m/h and 2500 m/h, in particular in the range between 350 m/h and 2300 m/h, in particular in the range between 400 m/h and 2000 m/h, in particular in the range between 450 m/h and 1800 m/h.

9. Method according to claim 1, characterized in that the surface temperature of the deposition element is detected by a temperature measuring device, in particular a pyrometer, the temperature measuring device outputting a temperature signal and/or temperature data, and a control device modifies, in particular increases, the electrical loading of the separator element as a function of the temperature signal and/or the temperature data.

10. Method according to claim 9, characterized in that the temperature measuring device carries out temperature measurements at time intervals of less than 5 minutes, in particular less than 3 minutes or less than 2 minutes or less than 1 minute or less than 30 seconds, and outputs temperature signal and/or temperature data, wherein a target temperature is defined, wherein the control device controls an increase in the electrical application as soon as the temperature signal and/or the temperature data re-present a surface temperature which is lower than a defined threshold temperature, wherein the threshold temperature is a temperature which is lower than the set temperature by a defined value, the defined value preferably being less than 10 C. or less than 5 C. or less than 3 C. or less than 2 C. or less than 1.5 C. or less than 1 C.

11. Method according to claim 1, characterized in that more of the source gas, in particular the first source gas and/or the second source gas, is introduced into the process chamber continuously or stepwise, in particular in a defined ratio, per unit time, preferably more of the source gas, in particular the first source gas and/or the second source gas, is introduced into the process chamber as a function of time, and/or more of the source gas, in particular the first source gas and/or the second source gas, is introduced into the process chamber as a function of the electrical loading.

12. Device for producing a preferably elongated SiC solid, in particular of polytype 3C, in particular for carrying out a previously mentioned process, comprising at least a process chamber for receiving an electrically chargeable deposition element, a first source gas, the first source gas comprising Si, a second source gas into the process chamber, the second source gas comprising C, a first supply means and/or a second supply means for supplying the first source gas and/or the second source gas with a pressure of more than 1 bar into the process chamber, a temperature measuring device for measuring the surface temperature of the deposition element, a control device for setting a deposition rate of more than 200 m/h, wherein from the control means the electrical application of the deposition element is adjustable, wherein the electrical application for generating a surface temperature is adjustable from 1300 C. and 1700 C.

13. Device for producing a preferably elongated SiC solid, in particular of polytype 3C, in particular for carrying out a previously mentioned process, comprising at least a process chamber for receiving an electrically chargeable deposition element, at least one source gas, in particular SiCl3(CH3), the source gas comprising Si and C, and a carrier gas into the process chamber, the carrier gas preferably comprising H, a first feeding device and/or a second feeding device for feeding the source gas and/or the carrier gas with a pressure of more than 1 bar into the process chamber, a temperature measuring device for measuring the surface temperature of the deposition element, a control device for setting a deposition rate of more than 200 m/h, wherein from the control means the electrical application to the deposition element is adjustable, wherein the electrical application is adjustable to produce a surface temperature of 1300 C. and 1700 C.

14. SiC solid state material, in particular 3C-SiC solid state material, having a purity excluding at least 99.9999% (ppm wt) of the substances B, Al, P, Ti, V, Fe, Ni and/or a density of less than 3.21 g/cm3, produced by a method according to claim 1.

15. Use of the SiC solid state material according to claim 14 in a PVT reactor for the production of monocrystalline SiC.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0176] FIG. 1 is a schematic example of a device for carrying out a method according to the invention, and

[0177] FIG. 2 is a schematic example of a PVT reactor into which the SiC solid-state material according to the invention is introduced as starting material.

DETAILED DESCRIPTION

[0178] 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.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] 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 2,200-2,400 C. and the temperature of the crystal growth surface is typically in the range of 2,000-2. 200 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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. 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.

[0194] Thus, the present invention may relate to a method or furnace device or apparatus for PVT growth of single crystals, particularly SiC single crystals, having multiples or all of the features or steps listed below:

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] Maintaining the crucible volume at a lower pressure than the furnace volume. Heating and sublimation of the starting material.

[0200] 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.

[0201] Therefore, a PVT furnace is preferably provided for the production of SiC single crystals 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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: [0207] Introducing at least a first source gas into a process chamber, the first source gas comprising Si, [0208] introducing at least a second source gas into the process chamber, the second source gas comprising C, [0209] electrically energizing at least one separator element disposed in the process chamber to heat the separator element, [0210] setting a deposition rate of more than 200 m/h, [0211] 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 [0212] wherein the surface of the deposition element is heated to a temperature in the range between 1300 C. and 1700 C.

LIST OF REFERENCE SIGNS

[0213] 1 PVT reactor [0214] 2 Furnace housing (lower part) [0215] 3 Furnace housing (upper part) [0216] 4 Furnace gas inlet [0217] 5 Crucible gas inlet [0218] 7 Crucible gas inlet connection piece [0219] 8 Bottom insulation [0220] 9 Side insulation [0221] 13 Crucible leg [0222] 17 Crystal [0223] 18 Seed wafer [0224] 20 Seals [0225] 22 Filter grooves or pores [0226] 26 Crucible vacuum outlet [0227] 28 Pyrometer sight line [0228] 50 Source material [0229] 100 Furnace [0230] 102 Hydrogen gas [0231] 104 Furnace volume [0232] 107 Crucible lid [0233] 122 Seed holder [0234] 130 Filter [0235] 152 Crucible base [0236] 158 Filter outer surface coating [0237] 164 Filter outer surface coating [0238] 172 Crucible gas inlet tube [0239] 174 Crucible vacuum outlet tube [0240] 204 Oven vacuum outlet [0241] 212 radial heating element [0242] 214 heating element [0243] 230 growth guide element [0244] 231 top of growth guide element [0245] 850 manufacturing device [0246] 851 first feeding device [0247] 852 second feeding device [0248] 853 third feeding device [0249] 854 mixing device [0250] 855 evaporator device [0251] 856 process chamber [0252] 857 separating element [0253] 858 temperature measuring device [0254] 859 Energy source, especially power supply [0255] 860 Pressure maintaining device