CRYSTAL GROWTH DEVICE AND METHOD FOR GROWING A SEMICONDUCTOR

Abstract

The invention relates to a crystal growth device for growing a semiconductor from a gas phase, the crystal growth device comprising, a crucible, a heater, and a holding plate. The crucible on a crucible vessel and a crucible lid supported on the crucible vessel, wherein the crucible vessel is configured to receive and hold a source material for the semiconductor during growth of the semiconductor. The heater is configured and arranged to heat the source material in the crucible vessel so that the source material at least partially changes to its gaseous phase and flows toward the crucible lid. The holding plate is configured to hold a seed crystal on a side of the holding plate facing the crucible lid, and to allow deposition of the source material that has changed into its gas phase on the seed crystal for growing the semiconductor. The holding plate is further configured to be spaced from a crucible bottom of the crucible vessel for growing the semiconductor, such that it is located between the source material and the crucible lid.

Claims

1. A crystal growth device for growing a semiconductor from a gas phase, the crystal growth device comprising: a crucible comprising a crucible vessel and a crucible lid arranged on the crucible vessel, the crucible vessel being configured to receive and hold a source material for the semiconductor during growth of the semiconductor, a heater that is configured and arranged to heat the source material in the crucible vessel so that the source material at least partially changes to its gaseous phase and flows toward the crucible lid, and a holding plate configured to hold a seed crystal on a side of the holding plate facing the crucible lid and to allow deposition of the source material that has changed to its gas phase on the seed crystal for growing the semiconductor, wherein the at least one holding plate is further configured to be arranged at a distance from a crucible bottom of the crucible vessel for growing the semiconductor, such that it is located between the source material and the crucible lid.

2. The crystal growth device of claim 1, wherein the holding plate is formed separately from the crucible and is removable from the crucible for introduction of the source material and can be arranged between the source material and the crucible lid for growth of the semiconductor.

3. The crystal growth device of claim 1, wherein the holding plate comprises at least one feedthrough which, when the holding plate is arranged between the source material and the crucible lid, extends from the surface of the holding plate facing the source material to the surface of the holding plate facing away from the bottom of the crucible, so that the source material having changed into its gas phase can pass through the at least one feedthrough.

4. The crystal growth device of claim 1, comprising a crystal growth mold having a mold body with inner side walls that enclose a growth volume in which the semiconductor can be grown, wherein the crystal growth mold is arranged and configured such that a pedestal for holding the seed crystal can be arranged within a bottom mold opening that is located in a bottom side of the mold body.

5. The crystal growth device of claim 1, comprising a pedestal for holding the seed crystal and comprising a crystal growth mold having a mold body with inner side walls that enclose a growth volume in which the semiconductor can grow, wherein the crystal growth mold is arranged on the pedestal and has a bottom mold opening that is located in a bottom side of the mold body such that the seed crystal held by the pedestal can be arranged within the bottom mold opening for growing the semiconductor.

6. A method of growing a semiconductor from a gas phase, the method comprising the steps of: providing a crystal growth device according to claim 1, placing a source material for the semiconductor into the crucible vessel, arranging the holding plate above the source material so that the holding plate is spaced from the crucible bottom of the crucible vessel, arranging at least one seed crystal on the surface of the holding plate facing away from the source material, arranging the crucible lid on the crucible vessel so that the holding plate is located between the source material and the crucible lid, and heating the source material so that the source material at least partly changes into the gas phase and flows towards the crucible lid, so that the source material which has changed into its gas phase can desublimate on the seed crystal.

7. The method of claim 6, wherein a temperature difference of 50 K to 150 K between a nucleation temperature of the seed crystal and a source temperature of the source material occurs during deposition of the source material that has changed to its gaseous phase.

8. The method of claim 6, wherein during the deposition of the source material that has changed to its gas phase on the seed crystal, a ratio of an m-growth rate of the semiconductor on its m-surface and a c-growth rate of the semiconductor on its c-surface is 0.6 or more.

9. The method of claim 6, wherein arranging the holding plate over the source material comprises arranging the holding plate onto the source material during growth of the semiconductor.

10. The method of claim 6, wherein arranging the holding plate over the source material comprises arranging the holding plate on a crucible rim of the crucible vessel.

11. The method of claim 6, wherein arranging the at least one seed crystal comprises arranging the seed crystal on a pedestal on the holding plate having a thermal conductivity of 30 W/(m*K) or less at room temperature and/or at a growth temperature of 2000 C. at least in a direction of that surface of the pedestal on which the seed crystal is arranged.

12. A semiconductor, in particular comprising or being made of AlN or SiC, having substantially no dislocations in at least 90% of its volume that have a Burgers vector with a component along the <0001>-direction, and having a diameter of 10 mm or more in at least one direction.

13. The semiconductor of claim 12, wherein a c-lattice parameter in at least 90% of the volume of the semiconductor varies in a range of 0.00060 or less, and/or an a-lattice parameter in the entire volume of the semiconductor varies in a range of 0.00040 or less.

14. A use of the semiconductor claim 12 for the fabrication of a semiconductor substrate having substantially no dislocations in at least 90% of its volume that have a Burgers vector having a component along the <0001>-direction.

15. The use of claim 14, wherein the semiconductor substrate is fabricated by mechanically and/or chemically processing the semiconductor, or wherein fabricating the semiconductor substrate comprises first fabricating, by mechanically and/or chemically processing the semiconductor, a seed wafer that is used to fabricate the semiconductor substrate by a crystal growth method, the crystal growth method preferably comprising arranging the seed wafer opposite a source material in a crucible so that there is a free viewing axis between the seed wafer and the source material.

16. A semiconductor substrate, in particular comprising or being made of AlN or SiC, having substantially no dislocations in at least 90% of its volume that have a Burgers vector with a component along the <0001>-direction, and having a diameter of 10 mm or more in at least one direction.

17. The semiconductor substrate of claim 16, wherein an asymmetric (10-12) reflex and/or a symmetric (0002) reflex, in particular, of X-ray radiation of a copper K-alpha emission, has a full width at half maximum of 12 arcseconds or less, measured with a spot size of at least 2 mm10 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0110] FIG. 1A: schematically and exemplary shows a crystal growth device for growing a semiconductor by means of physical gas phase transport as known from the prior art;

[0111] FIG. 1B:

[0112] shows the crucible of the crystal growth device described with reference to FIG. 1A separately and at the beginning of growing the semiconductor;

[0113] FIG. 1C: shows the crucible of the crystal growth device described with reference to FIG. 1A separately and at a comparatively later time instance during growth of the semiconductor;

[0114] FIG. 2: shows schematically a cut through a unit cell of a Wurtzite crystal parallel to a c-face;

[0115] FIG. 3A: schematically and exemplary shows in a longitudinal sectional view a crystal growth device for growing a semiconductor according to an embodiment of the present invention in operation and at the beginning of growing the semiconductor;

[0116] FIG. 3B: shows the crystal growth device described with reference to FIG. 3A in a longitudinal sectional view in operation at a comparatively later time instance during growth of a semiconductor;

[0117] FIG. 4A: schematically and exemplary shows in a longitudinal sectional-view, a crystal growth device for growing a semiconductor according to another embodiment of the present invention in operation and at the beginning of growing the semiconductor;

[0118] FIG. 4B shows the crystal growth device described with reference to FIG. 4A in a longitudinal sectional view in operation at a comparatively later time instance during a growth of a semiconductor;

[0119] FIGS. 5A to 5E: shows different schematically and exemplary illustrated holding plates that can be part of a crystal growth device described herein;

[0120] FIG. 6: shows a schematic flowchart illustrating a method of growing a semiconductor;

[0121] FIG. 7A schematically and exemplary shows in a longitudinal sectional view, a crystal growth device for growing a semiconductor according to another embodiment of the present invention in operation and at the beginning of growing the semiconductor;

[0122] FIG. 7B schematically and exemplary shows the crystal growth device described with reference to FIG. 7A in a longitudinal sectional view in operation at a comparatively later time instance during growth of a semiconductor;

[0123] FIG. 8A schematically and exemplary shows in a longitudinal sectional view, a crystal growth device for growing a semiconductor according to another embodiment of the present invention in operation and at the beginning of growing the semiconductor;

[0124] FIG. 8B schematically and exemplary shows the crystal growth device described with reference to FIG. 8A in a longitudinal sectional view in operation at a comparatively later time instance during growth of a semiconductor;

[0125] FIG. 9A schematically and exemplary shows in a longitudinal sectional view, a crystal growth device for growing a semiconductor according to another embodiment of the present invention in operation and at the beginning of growing the semiconductor; and

[0126] FIG. 9B schematically and exemplary shows the crystal growth device described with reference to FIG. 9A in a longitudinal sectional view in operation at a comparatively later time instance during growth of a semiconductor.

DETAILED DESCRIPTION OF EMBODIMENTS

[0127] FIG. 1A shows a crystal growth device 100 for growing a semiconductor using physical gas phase transport as known from the prior art. The crystal growth device 100 comprises a crucible 102 having a crucible vessel 104 and a crucible lid 106. The crucible 102 may be made of W or TaC, for example. A source material 108 is arranged in the crucible vessel 104 for growing a semiconductor. A seed crystal 110 is arranged on the crucible lid 106 and opposite to the source material 108. The seed crystal 110 may be attached to a seed holder (not shown) by means of a ceramic binder, e.g., AlN-based, or by means of mechanical clamping. The seed holder may be attached to, or may be integral with, the crucible lid 106. Thus, there is a free line of sight between the seed crystal 110 and the source material 108. For example, the seed crystal may be made of AlN or SiC and the source material 108 may comprise polycrystalline AlN or SiC, respectively. In this case, the c-surface of the AlN or SiC seed crystal 110 is parallel to the surface of the source material 108 and facing the source material 108 so that sublimated source material 108 can impinge directly on the c-surface of the seed crystal 110 as it flows toward the crucible lid 106 due to a corresponding temperature gradient within the crucible 102. The source material 108 has less than 150 ppm wt. of oxygen. In the crucible 102 there is an atmosphere of 99.999% nitrogen at a pressure of 500 to 800 millibars.

[0128] The crucible 102 is arranged within a susceptor 112, which may be made of graphite, for example. Thermal insulation 114 is arranged around the susceptor 112. The thermal insulation 114 may comprise carbon fibers, for example. The thermal insulation 114 includes a first opening 116 on the side of the crucible lid 106, and a second opening 120 on the side of the crucible bottom 118. The first opening 116 is larger than the second opening 120, such that a temperature gradient is established in the crucible 102 between the crucible lid 106 and the crucible bottom 118 during growth of the semiconductor, which ensures that sublimated source material 108 flows toward the crucible lid 106. In particular, heat radiation is greater at the crucible lid 106 than at the crucible bottom 118, causing sublimated source material 122 to flow toward the crucible lid 106. A heater 126, comprising an induction coil, is arranged around the thermal insulation 114 and is configured to heat the source material 108 arranged in the crucible 102 so that it at least partly sublimates.

[0129] In the crystal growth device 100, the temperatures at the crucible lid 106 and the crucible bottom 118 can each be measured using an infrared pyrometer. Using the measured temperatures and additional simulations of the temperatures within the crucible 102, the temperature gradient within the crucible 102 can be adjusted by tuning the heating power of the heater 126.

[0130] Optionally, the thermal insulation 14 may be enclosed by a housing (not shown), which may be made of quartz, for example. If the crystal growth device 100 includes a housing, the heater 126 is preferably arranged such that an induction coil of the heater 126 circulates around the housing 210.

[0131] FIG. 1B shows the crucible 102 of the crystal growth device 100 separately and at the beginning of the growth of the semiconductor. The crucible vessel 104 holds source material 108, the crucible lid 106 is arranged on the crucible vessel 104, and the seed crystal 110 is arranged at the crucible lid 106 opposite the source material 108. To grow the semiconductor, the source material 108 is heated by the heater 126 in the crucible vessel 104 so that it sublimates. The sublimated gaseous source material 122 flows in the crucible 102 toward the crucible lid 106 and then impinges on the surface of the seed crystal 110 facing the source material 108, that is, in particular, on the c-surface thereof. Since the c-surface of the seed crystal 100 is arranged opposite the source material 108, the semiconductor grows at a comparatively high growth rate on the surface facing the source material, i.e. in particular on the c-surface, whereas the growth rate on the side surface, i.e. in particular on the m-surface, is comparatively lower. Thus, comparatively more iterations are necessary to achieve a certain target diameter of the semiconductor.

[0132] FIG. 1C shows the crucible 102 of the crystal growth device 100 separately at a comparatively later time during the growth of the semiconductor. At this point in time, growth of the semiconductor 124 towards the source material 108, i.e., in particular on the c surface, has already taken place on the seed crystal 110. Accordingly, the source material 108 has already been heated by the heater 126 so that it is sublimed and flows towards the crucible lid 106 due to the temperature gradient. The gaseous source material 122 is desublimated at the seed crystal 110 so that the semiconductor 124 has increased in volume, in particular in the direction of the source material 108, that is, in particular in its c-direction. In particular, an angle of diameter increase in the c-direction is comparatively small. In particular, an angle of diameter increase in the c-direction is the angle included between a lateral outer surface of the grown semiconductor and a normal vector of the c-surface. Since the supply of material at the side surfaces of the seed crystal 110, i.e., particularly at the m surfaces, is comparatively smaller, the diameter of the semiconductor 124 has increased only slightly compared to the growth in the direction of the source material 108. It is therefore generally necessary for the fabrication of a semiconductor substrate to already use a seed crystal or seed wafer that already has a comparatively large diameter, such as two inches or more.

[0133] A semiconductor substrate can be fabricated from a semiconductor grown by the crystal growth device 100 by sawing a slice from the semiconductor with a diamond saw having a grain size of, for example, 1 m, and then chemically and mechanically polishing the slice, e.g., using SiO.sub.2 at pH >10. In particular, the AlN or SiC semiconductor can be processed to fabricate therefrom a {0001} or {10-10} AlN or SiC substrate.

[0134] FIG. 2 schematically shows a cut through a unit cell 200 of a Wurtzite crystal parallel to a c-surface 202. The unit cell 200 may be, for example, the unit cell of an AlN or SiC crystal. The unit cell 200 is spanned by the unit vectors a1 204 and a2 206 and by the unit vector c. The unit vectors a1 204 and a2 206 have an angle of 120 to each other and are identical in magnitude. The unit vector c (not shown) is perpendicular to the unit vectors a1 204 and a2 206.

[0135] Furthermore, the m-surface 208 and the a-surface 210 of the Wurtzite crystal are drawn into the unit cell 200. Here, the unit vectors a1 204 and a2 206 point perpendicular to a-surface 210. Furthermore, a normal vector 212 to m-surface 208 is drawn. The m-surface 208 and the a-surface 210 are inclined to each other by an angle of 30.

[0136] FIG. 3A shows a longitudinal sectional view of a crystal growth device 300 for growing a semiconductor according to an embodiment of the present invention. The crystal growth device 300 is shown, by way of example, in operation at the beginning of growing the semiconductor.

[0137] The crystal growth device 300 has a crucible 302, which may be made of W or TaC, for example. The crucible 302 includes a crucible vessel 304 and a crucible lid 306. Further, the crystal growth device 300 includes a heater 308, which may comprise one or more induction coils, and a holding plate 312.

[0138] A source material 310, preferably comprising polycrystalline AlN or SiC, is arranged in the crucible vessel 304. A holding plate 312 is supported on a crucible rim of the crucible vessel 304 and includes a plurality of feedthroughs 314, 316. The holding plate 312 may be made of W or TaC, for example, and may have a thickness of 0.01 mm to 10 mm, although a thickness of 0.1 mm to 1 mm is preferred. The crucible lid 306 is arranged on the holding plate 312 so that a closed gas space 318 is formed above the source material 310 in the crucible 302. This gas space 318 can be filled with a nitrogen atmosphere, for example.

[0139] On the surface 320 of the holding plate 312 facing the crucible lid 306, a seed crystal 324 is arranged on a pedestal 322. In particular, the pedestal 322 and the seed crystal 324 are arranged loosely on the holding plate 312 and are not fixedly connected thereto. The pedestal 322 preferably has a thickness of 1 mm to 5 mm and may be made of W, WC, TaN or TaC, for example. In particular, the pedestal 322 serves to increase the distance between the seed crystal 324 and the holding plate 312 so that the supply of sublimated source material 326 is increased during growth of the semiconductor. Further, the pedestal 322 serves to thermally isolate the seed crystal from the holding plate so as to realize a comparatively large temperature gradient between the seed temperature of the seed crystal and the source temperature of the source material.

[0140] The heater 308 is used to heat the source material 310 during operation of the crystal growth device 300, such that the source material 310 at least partially sublimates. The sublimated gaseous source material 326 flows toward the crucible lid 306 due to a temperature gradient within the crucible 302 and flows through the feedthroughs 314, 316 of the holding plate 312 on its way to the crucible lid 306. The gaseous source material 326 preferentially desublimates at the side surfaces of the seed crystal 324 that are in the gas flow of the gaseous source material 426. Since the holding plate 312 is arranged between the seed crystal 324 and the source material 308, and the seed crystal 324 has its c-surface facing the crucible lid 306, the material supply of sublimated source material 326 at the c-surface is comparatively less than at the side surfaces of the seed crystal 324. Accordingly, the semiconductor grows comparatively slower on the c-surface and comparatively more on the m-surface of the seed crystal 324, and thus comparatively fewer iterations are required to achieve a desired target diameter of the semiconductor. This may also reduce a likelihood that dislocations will be incorporated into the semiconductor. Additionally, the dislocation density in the semiconductor may be reduced by having the seed crystal 324 loosely and freely supported on the holding plate 312 so that thermal stresses due to different thermal expansion coefficients between the seed crystal and a seed holder, such as those used in the known crystal growth device described with reference to FIGS. 1A to 1C, are avoided.

[0141] The crystal growth device 300 may further comprise a susceptor and thermal insulation and a housing, wherein the susceptor and thermal insulation are preferably arranged between the crucible 302 and the heater 308. For example, the susceptor and thermal insulation may be formed as described with reference to FIGS. 1A to 1C. In particular, the device 300 may have the components of the crystal growth device 100 described with reference to FIG. 1A, except that the crucible 102 is replaced by the crucible 302 with the holding plate 312 arranged between the source material 310 and the crucible lid 306.

[0142] FIG. 3B shows the crystal growth device 300 in a longitudinal sectional view in operation at a later time during a growth of a semiconductor 328. At this time instance, polycrystalline semiconductor material 330, for example made of AlN or SiC, has already been deposited on the crucible lid 306. The polycrystalline semiconductor material 330 may be used, for example, as a source material for growing another semiconductor.

[0143] The semiconductor 328 already fabricated at the later time has a region 331 formed by deposition of source material 326 on the c surface of the seed crystal 324. Schematically indicated, an angle of diameter increase 332 in the c-direction is comparatively large. For example, the angle of diameter increase 332 in the c-direction may be greater than 15, or greater than 20, or greater than 30. In particular, the angle of diameter increase 332 in the c-direction may be from 20 to 60. In particular, the angle of diameter increase 332 is formed between an outer surface 338 of the semiconductor 328 formed by growth on the c surface and a normal vector 340 of the c surface 342 of the semiconductor 328.

[0144] The semiconductor 328 further includes lateral regions 334, 336 formed by lateral growth on the m surface of the semiconductor. Due to the comparatively high growth rate in the m-direction and the comparatively lower growth rate in the c-direction, the desired target diameter of the semiconductor 328 can be achieved with comparatively fewer iterations and a comparatively lower volume increase in the c-direction using the crystal growth device 300.

[0145] FIG. 4A shows a longitudinal sectional view of a crystal growth device 400 for growing a semiconductor 428 according to another embodiment of the present invention. The crystal growth device 400 includes a crucible 402, which may be formed in the same manner as the crucible 302 of the crystal growth device 300 described with reference to FIGS. 3A and 3B. Accordingly, the crucible 402 also has a crucible vessel 404 and a crucible lid 406. A source material 410 is arranged in the crucible vessel 404 during operation of the crystal growth device 400. The crystal growth device 400 further comprises a heater 408, which may be formed by or include one or more induction coils, for example.

[0146] Unlike the crystal growth device 300 described with reference to FIGS. 3A and 3B, the crystal growth device 400 has a multi-part holding plate with two holding plate parts 412, 413 that are arranged on the source material 410 for growing the semiconductor 428. Thus, the holding plate parts 412, 413 are in direct contact with the source material 410. Of the holding plate parts 412, 413, one holding plate part 412 is formed as a disk and is arranged in the center of the crucible 402 on the source material 410. The other holding plate part 413 is formed as a ring so that the disk 412 can be arranged within the ring 413. When the disk 412 and the ring 413 are arranged on the source material 410, free areas 440, 442 or free spaces are formed between the disk 412 and the ring 413 through which sublimated source material 426 can flow toward the crucible lid 406.

[0147] A seed crystal 424 is arranged on the disk 412 and is arranged on a pedestal 422. The seed crystal 424 is preferably made of AlN or of SiC, and the source material 410 is preferably made of polycrystalline AlN or SiC, respectively, so that an AlN or a SiC semiconductor can be grown with the crystal growth device 400.

[0148] FIG. 4B shows the crystal growth device 400 in a longitudinal sectional view in operation at a later time during a growth of a semiconductor 428. At this time instance, the semiconductor 428 has increased in volume both in the direction perpendicular to the holding plate 412, for example in its c-direction, and in the lateral direction, in particular in the m-direction, as sublimated source material 426 is desublimated at the seed crystal 424. Since the side surfaces of the semiconductor 428 are in the gas flow of the sublimated source material 426, the material supply at the side surfaces is comparatively large. This results in comparatively large growth rates in the lateral direction, e.g., in the m-direction. Since the material supply on the surface of the semiconductor 428 facing the crucible lid 406 is comparatively lower, a growth rate in this direction, i.e. in particular in the c-direction, is also comparatively lower. In particular, a ratio of the growth rate lateral with respect to the holding plate 512 to the growth rate perpendicular with respect to the holding plate 512 may be from 0.6 to 2.0, and in particular may be 1.0 or more.

[0149] The semiconductor 428 has a region 431 formed by deposition of gaseous source material 426 on the surface facing the crucible lid 406, i.e., in particular the c surface, of the seed crystal 424. As also described with reference to FIG. 3B, a comparatively large angle of diameter increase 432 in the c-direction can be achieved. The semiconductor 428 further has lateral regions 434, 436 formed by lateral growth along the m-direction of the semiconductor 428.

[0150] FIGS. 5A, 5B, 5C, 5D, and 5E illustrate various exemplary holding plates 500, 510, 520, 530, and 540 that may be part of a crystal growth device described herein. For example, the holding plates 500, 510, 520, 530, and 540, may be used as a holding plate of the crystal growth device 300 described with reference to FIG. 3A or 3B, or as a holding plate of the crystal growth device 400 described with reference to FIG. 4A or 4B or as a holding plate of the crystal growth device 700 described with reference to FIG. 7A or 7B or as a holding plate of the crystal growth device 800 described with reference to FIG. 8A or 8B. In addition to the geometries of the holding plates 500, 510, 520, 530, and 540 shown herein, holding plates having other geometries may also be used. The geometries shown herein are to be considered merely exemplary. However, it is preferred that a holding plate used has a free area of 5% to 75%. The free area can, for example, be formed by feedthroughs. Alternatively or additionally, the free area of 5% to 75% may also be realized by arranging a plurality of holding plate portions of a multi-part holding plate side by side on the source material when growing a semiconductor, so that free spaces are formed between the plurality of holding plate portions. Again alternatively or additionally, the free area of 5% to 75% may also be realized by the holding plate having a smaller outer diameter than the inner diameter of the crucible vessel so that gaseous source material can flow past the holding plate during growth of the semiconductor.

[0151] The two-piece holding plate 500 shown in FIG. 5A includes a disk 502 arranged within a ring 504. An open space 506 is formed between the disk 502 and the ring 504, particularly during growth of a semiconductor, through which gaseous source material can flow. In addition, the holding plate has an outer diameter 507 that is smaller than the inner diameter 508 of a crucible (not shown). This also creates regions 509 around the holding plate 500 where the source material is not covered, i.e., exposed. Gaseous source material can also flow through these regions 509 outside the holding plate 500 toward a crucible lid during growth of the semiconductor. In particular, the disk 502 and the ring 504 may be placed on a source material arranged in a crucible vessel and are then in direct contact with the source material. For example, a seed crystal may be arranged on the disk 502. Further seed crystals may also be arranged on the ring 504.

[0152] The holding plate 510 shown in FIG. 5B is formed in one piece. In particular, the holding plate 510 is formed by an inner disk 511, which is connected to a ring 513 by a plurality of inner webs 512. The ring 513 is in turn connected by outer webs 514 to an outer ring 515. The diameter of the holding plate 510 may be such that the holding plate 510 with the outer ring 515 can be placed on a rim of a crucible. Alternatively, the diameter of the holding plate 510 may be such that the holding plate 510 can be placed directly on a source material located in a crucible vessel. By being connected by inner and outer webs 512, 514, the holding plate 510 has a plurality of feedthroughs 516, 517 formed between the disk 511 and the ring 513 and between the ring 513 and the outer ring 515. For example, a seed crystal may be arranged on the inner disk 511. Additionally, further seed crystals may be arranged on the ring 513.

[0153] The free area at the holding plates 500 and 510 is between 40% and 50%. The other holding plates 520, 530, 540 are each formed in one piece and have a plurality of feedthroughs 522, 532, 542 formed such that the holding plates 520, 530, 540 each have a free area between 10% and 20%.

[0154] The feedthroughs 522 of the holding plate 520 are each circular in shape and arranged along an imaginary circle around the center of the holding plate 520. The feedthroughs 532 are rectangular in shape and point radially away from the center of the holding plate 530. The feedthroughs 542 are arcuate in shape and extend along an imaginary circle around the center of the holding plate 540. In the case of the holding plates 520, 530, and 540, a seed crystal can be arranged in the center, which is then surrounded by the feedthroughs 522, 532, 542. As a result, gaseous source material can flow through the feedthroughs 522, 532, 542 in the direction of the crucible lid and desublimate, in particular, on the side surfaces, i.e., in particular, the m-surfaces, of the seed crystal.

[0155] FIG. 6 shows a schematic flow diagram representing a method of growing a semiconductor.

[0156] In the method, a crystal growth device is first provided (step S1), comprising a crucible, a heater, and a holding plate. The holding plate may be spaced apart from a crucible bottom of the crucible vessel for growing the semiconductor over source material arranged in the crucible vessel, such that it is located between the source material and the crucible lid. In particular, the crystal growth device used in the method may be configured as described with reference to FIGS. 3A and 3B or as described with reference to FIGS. 4A and 4B or as described with reference to FIGS. 7A and 7B or as described with reference to FIGS. 8A and 8B or as described with reference to FIGS. 9A and 9B. By way of example, the method may be carried out using the crystal growth device 300 described with reference to FIGS. 3A and 3B or using the crystal growth device 400 described with reference to FIGS. 4A and 4B or using the crystal growth device 700 described with reference to FIGS. 7A and 7B or using the crystal growth device 800 described with reference to FIGS. 8A and 8B or using the crystal growth device 900 described with reference to FIGS. 9A and 9B.

[0157] For growing the semiconductor, a source material, for example polycrystalline AlN or SiC, is introduced into the crucible vessel of the crucible (step S2). The source material is in particular in powder form and can be pressed for better insertion and heating. The holding plate is then arranged over the source material (step S3), which can be formed, for example, as described with reference to FIGS. 5A to 5E. For example, depending on the crystal growth device, the holding plate may be arranged over the source material by being arranged on a rim of the crucible, as described with reference to FIGS. 3A and 3B. Alternatively, the holding plate may be arranged over the source material by being placed directly on the source material as described with reference to FIGS. 4A and 4B and then being in direct contact with the source material. For example, multiple holding plate parts of a multi-part holding plate may also be arranged directly on the source material.

[0158] When the one-piece holding plate or the multi-piece holding plate is arranged on the source material, a seed crystal is placed on the holding plate or a holding plate part (step S4). If the source material is polycrystalline AlN or SiC, the seed crystal is also made of AlN or SiC accordingly. The crucible vessel is then covered by arranging a crucible lid on the crucible vessel (step S5). If the holding plate is arranged on the crucible rim, the crucible lid is arranged in particular on the holding plate. By arranging the crucible lid, a closed gas space is provided above the source material in which the semiconductor is grown. When the crucible lid is arranged on the crucible vessel, the holding plate is located between the source material and the crucible lid and is spaced apart from the crucible lid and the bottom of the crucible in particular. Subsequently, the source material is heated (step S6) so that the source material arranged in the crucible vessel at least partially and in particular by sublimation changes into the gas phase.

[0159] A temperature gradient is set in the crucible between a nucleation temperature of the seed crystal and a source temperature of the source material, which is from 50 K to 150 K during the growth of the semiconductor. Due to the temperature gradient, the sublimated source material flows toward the colder crucible lid, so that the source material that has changed to its gas phase can desublimate at the seed crystal. Due to the use of the holding plate, the semiconductor grows at a comparatively high growth rate in the lateral direction of the semiconductor by desublimating the source material. Thus, it can be achieved that the semiconductor reaches its target diameter with only fewer iterations of the method described herein. Furthermore, the method can be used to fabricate a semiconductor that has a comparatively high crystal quality. For example, the method can be used to fabricate a semiconductor, in particular of AlN or SiC, that has substantially no dislocations in at least 90% of its volume that have a Burgers vector with a component along the <0001>-direction, and that has a diameter of 10 mm or more in at least one direction. Further, a semiconductor fabricated by the method may have a c-lattice parameter that varies in at least 90% of the volume of the semiconductor in a range of 0.00060 or less, and/or have an a-lattice parameter that varies in the entire volume of the semiconductor in a range of A or less.

[0160] A semiconductor fabricated by the method can be used to produce a semiconductor substrate. For example, the semiconductor may be mechanically and/or chemically processed such that a semiconductor substrate having a diameter of at least 10 mm, e.g., 100 mm, and a thickness of from 0.1 mm to, e.g., from 0.5 mm to 3 mm is directly fabricated from the semiconductor.

[0161] The semiconductor can also be used to first produce a seed wafer, which is then used in a further crystal growth process to produce the semiconductor substrate. For example, the crystal growth device described with reference to FIGS. 1A to 1C may be used to fabricate the semiconductor substrate using the seed wafer. The seed disk would then be arranged in the crucible facing the source material, so that there is a free viewing axis between the source material and the seed disk, and sublimated source material would impinge directly on the surface of the seed crystal facing the source material, that is, in particular, on the c surface thereof. This would have the advantage that the semiconductor substrate on the seed disk would grow in particular in the direction of the source material, i.e. in particular in the c-direction in the case of a Wurtzite crystal, and the semiconductor substrate would increase in thickness comparatively faster.

[0162] FIG. 7A schematically and exemplary shows in a longitudinal sectional view, a crystal growth device 700 for growing a semiconductor according to another embodiment of the present invention in operation and at the beginning of growing the semiconductor. The crystal growth device 700 comprises the same components as the crystal growth device 400 described with reference to FIGS. 4A and 4B. Accordingly, the crystal growth device 700 includes a crucible 702. The crucible 702 also has a crucible vessel 704 and a crucible lid 706. A source material 710 is arranged in the crucible vessel 704 during operation of the crystal growth device 700. The crystal growth device 700 further comprises a heater 708, which may be formed by or include one or more induction coils. A holding plate 712, 713 is arrange directly on the source material 710. For further details and possible variations of these components, it is referred to the description of the crystal growth device 400 provided with reference to FIGS. 4A and 4B. Corresponding reference signs are used in FIGS. 7A and 7B wherein the first number of the respective reference signs used in FIGS. 4A and 4B has been changed from 4 to 7.

[0163] In contrast to the crystal growth device 400 described with reference to FIGS. 4A and 4B, the crystal growth device 700 comprises an additional crystal growth mold 738. The crystal growth mold 738 comprises a mold body 740 having inner side walls 742 that are configured to enclose a growth volume 744 in which the semiconductor can grow. The crystal growth mold 738 is arranged on pedestal 722 that has a larger lateral diameter than a seed crystal 724 that is arranged on the pedestal 722. The mold body 740 comprises a bottom mold opening 746 that is located in a bottom side 748 of the mold body 740. The seed crystal 724 arranged on the larger diameter pedestal 722 sits inside the bottom mold opening 746 and thereby within the growth volume 744 formed by the mold body's inner side walls 742. The inner side walls 742 of the crystal growth mold 738 are inclined such that the semiconductor 728 when growing inside the growth volume 744 increases in diameter to its lateral sides. However, the diameter increase is predefined and limited by the inner side walls 742 of the mold body 740. The crystal growth mold 738 may also be used together with the crystal growth device 300 described with reference to FIGS. 3A and 3B.

[0164] FIG. 7B schematically and exemplary shows the crystal growth device 700 described with reference to FIG. 7A in a longitudinal sectional view in operation at a comparatively later time instance during growth of a semiconductor. At this time instance, the semiconductor 728 has already gained volume. In particular, due to desublimation of the gaseous source material 726, the semiconductor 728 has filled the growth volume 744 of the crystal growth mold 738. As can be seen in FIG. 7B, the lateral sides 750 of the semiconductor 728 extend along the inner side walls 742 of the mold body 740, i.e., they follow the inclination of the inner side walls 742.

[0165] FIG. 8A schematically and exemplary shows in a longitudinal sectional view, a crystal growth device 800 for growing a semiconductor 828 according to another embodiment of the present invention in operation and at the beginning of growing the semiconductor 826. The crystal growth device 800 also comprises the most of the components of the crystal growth device 400 described with reference to FIGS. 4A and 4B. Accordingly, the crystal growth device 800 also includes a crucible 802. The crucible 802 also has a crucible vessel 804 and a crucible lid 806. A source material 810 is arranged in the crucible vessel 804 during operation of the crystal growth device 800. The crystal growth device 800 further comprises a heater 808, which may be formed by or include one or more induction coils. The holding plate 812, 813 is arrange directly on the source material 810. For further details and possible variations of these components, it is referred to the description of the crystal growth device 400 provided with reference to FIGS. 4A and 4B. Corresponding reference signs are used in FIGS. 8A and 8B wherein the first number of the respective reference signs used in FIGS. 4A and 4B has been changed from 4 to 8.

[0166] As the crystal growth device 700 described with reference to FIGS. 7A and 7B, the crystal growth device 800, too, comprises a crystal growth mold 838. The crystal growth mold 838 is configured similar to the crystal growth mold 738 of crystal growth device 700. However, in contrast to the crystal growth mold 738, the crystal growth mold 838 is configured such that the mold body 840 laterally encloses a pedestal 822. Thus, in contrast to the crystal growth device 700, in the crystal growth device 800, the crystal growth mold 838 is not arranged on a pedestal but directly on the holding plate 812.

[0167] The mold body 840 has a bottom mold opening 846 that is located in a bottom side 848 of the mold body 840. The bottom mold opening 846 is sized so that a seed crystal 824 arranged on the pedestal 822 can be arranged fully inside the bottom mold opening. Thus, in contrast to the crystal growth device 700, in the crystal growth device 800, the seed crystal 824 and the pedestal 822, both, are arranged fully within the bottom mold opening 846 of the mold body 840. Accordingly, the seed crystal 824 and the pedestal 822 are arranged within the growth volume 844 formed by the mold body's inner side walls 842. The crystal growth mold 838 may also be used together with the crystal growth device 300 described with reference to FIGS. 3A and 3B.

[0168] FIG. 8B schematically and exemplary shows the crystal growth device 800 described with reference to FIG. 8A in a longitudinal sectional view in operation at a comparatively later time instance during growth of a semiconductor. As can be seen in FIG. 8A, at this later time instance, the semiconductor 828 has gained volume due to desublimation of gaseous source material 826 on the seed crystal 824. During growth, the expansion in volume of the semiconductor 828 was limited to its lateral sides by the inclined inner side walls 842 of the mold body 840.

[0169] FIG. 9A schematically and exemplary shows in a longitudinal sectional view, a crystal growth device for growing a semiconductor according to another embodiment of the present invention in operation and at the beginning of growing the semiconductor. The crystal growth device 900 also comprises the most of the components of the crystal growth device 400 described with reference to FIGS. 4A and 4B. Accordingly, the crystal growth device 900 also includes a crucible 902. The crucible 902 also has a crucible vessel 904 and a crucible lid 906. A source material 910 is arranged in the crucible vessel 904 during operation of the crystal growth device 900. The crystal growth device 900 further comprises a heater 908, which may be formed by or include one or more induction coils. The holding plate 912, 913 is arrange directly on the source material 910. For further details and possible variations of these components, it is again referred to the description of the crystal growth device 400 provided with reference to FIGS. 4A and 4B. Corresponding reference signs are used in FIGS. 9A and 9B wherein the first number of the respective reference signs used in FIGS. 4A and 4B has been changed from 4 to 9.

[0170] The crystal growth device 900 comprises a crystal growth mold 938. The crystal growth mold 938 is configured similar to the crystal growth mold 838 of crystal growth device 800. However, in contrast to the crystal growth mold 838, the crystal growth mold 938 has side walls with a constant lateral thickness.

[0171] As the mold body 840, also the mold body 940 has a bottom mold opening 946 that is located in a bottom side 948 of the mold body 940. The bottom mold opening 946 is sized so that a seed crystal 924 arranged on the pedestal 922 can be arranged fully inside the bottom mold opening. Accordingly, the seed crystal 924 and the pedestal 922 are arranged within the growth volume 944 formed by the mold body's inner side walls 842. The crystal growth mold 938 may also be used together with the crystal growth device 300 described with reference to FIGS. 3A and 3B.

[0172] FIG. 9B schematically and exemplary shows the crystal growth device described with reference to FIG. 9A in a longitudinal sectional view in operation at a comparatively later time instance during growth of a semiconductor. At this later time instance, the semiconductor 928 has already gained volume. In particular, due to desublimation of the gaseous source material 926, the semiconductor 928 has filled the growth volume 944 of the crystal growth mold 938. As can be seen in FIG. 9B, the lateral sides 950 of the semiconductor 928 extend along the inner side walls 942 of the mold body 940.

[0173] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0174] In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality.

[0175] Any reference signs in the claims should not be construed as limiting the scope.

LIST OF REFERENCE SIGNS

[0176] 100 crystal growth device [0177] 102 crucible [0178] 104 crucible vessel [0179] 106 crucible lid [0180] 108 source material [0181] 110 seed crystal [0182] 112 susceptor [0183] 114 thermal insulation [0184] 116 first opening [0185] 118 crucible bottom [0186] 120 second opening [0187] 122 gaseous source material [0188] 124 semiconductor [0189] 126 heater [0190] 200 unit cell [0191] 202 c surface [0192] 204 unit vector a1 [0193] 206 unit vector a2 [0194] 208 m surface [0195] 210 a surface [0196] 212 normal vector tom surface [0197] 300 crystal growth device [0198] 302 crucible [0199] 304 crucible vessel [0200] 306 crucible lid [0201] 308 heater [0202] 310 source material [0203] 312 holding plate [0204] 314, 316 feedthroughs [0205] 318 closed gas space [0206] 320 surface [0207] 322 pedestal [0208] 324 seed crystal [0209] 326 source material [0210] 328 semiconductor [0211] 330 semiconductor material [0212] 331 area [0213] 332 angle of diameter increase [0214] 334, 336 lateral areas [0215] 338 exterior surface [0216] 340 normal vector [0217] 400 crystal growth device [0218] 402 crucible [0219] 404 crucible vessel [0220] 406 crucible lid [0221] 410 source material [0222] 412, 413 holding plate parts (disk, ring) [0223] 422 pedestal [0224] 424 seed crystal [0225] 426 sublimated source material [0226] 428 semiconductor [0227] 431 region formed by deposition of gaseous source material [0228] 432 large angle of diameter increase [0229] 434, 436 lateral areas [0230] 440, 442 free areas [0231] 500, 510, 520, 530, 540 holding plates [0232] 502 disk [0233] 504 ring [0234] 507 outer diameter [0235] 508 inner diameter [0236] 509 regions outside the holding plate [0237] 510 holding plate [0238] 511 disk [0239] 512, 514 inner and outer webs [0240] 513 ring [0241] 515 outer ring [0242] 516, 517 feedthroughs [0243] 520, 530, 540 holding plates [0244] 522, 532, 42 feedthroughs [0245] 700 crystal growth device [0246] 702 crucible 702 [0247] 704 crucible vessel [0248] 706 crucible lid [0249] 708 heater [0250] 710 source material [0251] 712, 713 holding plate [0252] 722 pedestal [0253] 724 seed crystal [0254] 726 sublimated source material [0255] 728 semiconductor [0256] 738 crystal growth mold [0257] 740 mold body [0258] 742 inner side walls [0259] 744 growth volume [0260] 746 bottom mold opening [0261] 748 bottom side [0262] 750 lateral sides of the semiconductor [0263] 800 crystal growth device [0264] 802 crucible 702 [0265] 804 crucible vessel [0266] 806 crucible lid [0267] 808 heater [0268] 810 source material [0269] 812, 813 holding plate [0270] 822 pedestal [0271] 824 seed crystal [0272] 826 sublimated source material [0273] 828 semiconductor [0274] 838 crystal growth mold [0275] 840 mold body [0276] 842 inner side walls [0277] 844 growth volume [0278] 846 bottom mold opening [0279] 848 bottom side [0280] 850 lateral sides of the semiconductor [0281] 900 crystal growth device [0282] 902 crucible 702 [0283] 904 crucible vessel [0284] 906 crucible lid [0285] 908 heater [0286] 910 source material [0287] 912, 913 holding plate [0288] 922 pedestal [0289] 924 seed crystal [0290] 926 sublimated source material [0291] 928 semiconductor [0292] 938 crystal growth mold [0293] 940 mold body [0294] 942 inner side walls [0295] 944 growth volume [0296] 946 bottom mold opening [0297] 948 bottom side [0298] 950 lateral sides of the semiconductor