Systems and methods for controlling the growth of silicon carbide crystals

Abstract

A system for growing silicon carbide (SiC) single crystals by physical vapor transport is provided that overcomes the problems inherent in such systems. The growth system may include a crucible at least partially surrounded by a thermal insulating layer, a growth region located within the crucible and configured to hold a SiC seed crystal, and a source material region located within the crucible and configured to hold a SiC source material. The growth system may further include a barrier located within the crucible and configured to separate the source material region from the growth region. Additionally, the growth system may include a heating element located around the crucible and configured, together with an opening in the thermal insulating layer, to provide a temperature gradient that decreases in temperature in a direction from the source material region toward the growth region. The growth system may also include a vent extending through the barrier from the source material region to the growth region.

Description

[Technical Field]

[0001] The present disclosure relates generally to growing silicon carbide (SiC) crystals, and more particularly to growing SiC crystals in a physical vapor transport system. [Background technology]

[0002] Silicon carbide (SiC) is a semiconductor material that can be used in certain applications due to its physical and electrical properties. SiC wafers are used to fabricate SiC devices, such as SiC-based metal-oxide semiconductor field-effect transistors (MOSFETs). SiC wafers can be manufactured by cutting a disk-shaped SiC substrate from a SiC single crystal. Such SiC single crystals can be grown by the physical vapor transport (PVT) process.

[0003] In a conventional PVT process, a SiC source powder can be heated to provide a vapor by sublimation. The vapor can then be deposited on a SiC seed crystal to grow a SiC single crystal. In a conventional PVT process, the SiC source powder can be encapsulated by a porous graphite film. The inventors of embodiments of the present disclosure have recognized that such porous graphite materials are brittle and therefore can present challenges in a manufacturing environment. The inventors of embodiments of the present disclosure have also recognized that the conventional PVT process can be time-consuming and that controlling the growth rate of the SiC single crystal can be beneficial to production capacity. Embodiments of the present disclosure may address one or more of these challenges. [Brief explanation of the drawings]

[0004] A more complete understanding of the present embodiments can be obtained by reference to the following description in conjunction with the accompanying drawings, in which like reference numerals indicate like features and in which: [Figure 1A] FIG. 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present disclosure. [Figure 1B] FIG. 1 shows a top view of a crystal growth system according to some embodiments of the present disclosure. [Figure 1C] FIG. 1 shows a top view of a crystal growth system according to some embodiments of the present disclosure. [Figure 2] 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present invention. [Figure 3] 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present invention. [Figure 4] FIG. 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present disclosure. [Figure 5] 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present invention. [Figure 6] 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present invention. [Figure 7] 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present invention. [Figure 8] 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present invention. [Figure 9] 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present invention. [Figure 10A] FIG. 1 shows a cross-sectional side view of a crystal growth system according to some embodiments of the present disclosure. [Figure 10B] FIG. 1 shows a top view of a crystal growth system according to some embodiments of the present disclosure. [Figure 10C] FIG. 1 shows a top view of a crystal growth system according to some embodiments of the present disclosure. [Figure 10D] FIG. 1 shows a top view of a crystal growth system according to some embodiments of the present disclosure. [Figure 10E] FIG. 1 shows a top view of a crystal growth system according to some embodiments of the present disclosure. [Figure 11] 1 illustrates a method for growing SiC crystals according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0005] The details of one or more embodiments are set forth in the following description and the accompanying drawings. Other features will be apparent from the description and drawings, and from the claims.

[0006] 1A shows a cross-sectional side view of a crystal growth system 100 according to some embodiments of the present disclosure. The crystal growth system 100 may include a crucible 110, a growth region 112, a source material region 114, a barrier 118, an insulating layer 120, a heating element 122, an opening 124, and a vent 130.

[0007] In some embodiments, the crucible 110 may have a cylindrical shape. The crucible 110 may be at least partially surrounded by an insulating layer 120. For example, the insulating layer 120 may surround the crucible 110 except for an opening 124, which may be located on the upper side of the crucible 110. In some embodiments, the opening 124 may serve as a viewport for a pyrometer (not shown in FIG. 1A ) located at the top of the growth furnace to monitor the temperature of the crucible 110. The opening 124, in conjunction with the heating element 122, may provide a temperature gradient in which the temperature decreases from the source material region 114 toward the opening 124. For example, the heating element 122 may be configured to heat the contents of the crucible 110, such as the SiC source material 116 in the source material region 114. In some embodiments, the heating element 122 may be implemented by an RF heating coil. The opening 124 can provide a cooling path through the insulating layer 120 and, together with the heating element 122, can create a temperature gradient within the crucible 110 in which the temperature decreases in a direction from the source material region 114 toward the growth region 112, the top of which can be adjacent to the opening 124.

[0008] The growth region 112 may be located within the crucible 110. For example, the growth region 112 may be located within an upper portion of the crucible 110 adjacent the opening 124. Additionally, the growth region 112 may be configured to hold a silicon carbide (SiC) seed crystal 160. As described in further detail below, a SiC single crystal may be grown using the SiC seed crystal 160 as a seed for the growth of the single crystal in a PVT process.

[0009] The source material region 114 may be located within the crucible 110. For example, the source material region may be located within a lower portion of the crucible 110 opposite the opening 124. The source material region 114 may be configured to hold a SiC source material 116. In some embodiments, the SiC source material 116 may be a SiC source powder. When heated by the heating element 122, the SiC source material 116 may be transformed into a vapor that can be deposited onto a SiC seed crystal 160 to grow a SiC single crystal.

[0010] A barrier 118 may be located within the crucible 110 and configured to separate the source material region 114 from the growth region 112. For example, the barrier 118, together with the sidewalls of the crucible 110, may enclose the SiC source material 116 located within the source material region 114. The barrier 118 may be implemented in any suitable manner consistent with the operations described herein. For example, in some embodiments, the barrier 118 may include a layer of porous graphite. Also, in some embodiments, the barrier 118 may alternatively or additionally include a layer of isotropic graphite or other suitable material.

[0011] 1B shows a top view of a crystal growth system 100 according to some embodiments of the present disclosure. Specifically, FIG. 1B shows a top view of the crystal growth system 100 from the perspective of section line A shown in FIG. 1A.

[0012] 1A and 1B, the crystal growth system 100 may also include a vent 130. The vent 130 may be implemented in any suitable manner consistent with the operation described herein. The vent 130 may have an interior space 133 defined between an outer sidewall 131 and an inner sidewall 132. The inner sidewall 132 may have a first cylindrical shape centered on a central axis 180 of the crucible 110. The outer sidewall 131 may have a second cylindrical shape centered on the central axis 180 of the crucible 110. As shown by the side cross-sectional view of FIG. 1A together with the top view of FIG. 1B, the first cylindrical shape of the inner sidewall 132 may have a first diameter that is smaller than a second diameter of the second cylindrical shape of the outer sidewall 131.

[0013] During crystal growth, the heating element 122 can heat the contents of the crucible 110, including the SiC source material 116 contained within the source material region 114. Upon heating, sublimation can occur, causing the SiC source material 116 to transition from a solid form to a vapor. As described above, the heating element 122, in conjunction with the cooling paths formed by the openings 124 in the thermal insulation layer 120, can establish a temperature gradient that decreases in temperature in a direction from the source material region 114 to the growth region 112. Vapor can migrate from a hotter region to a cooler region, for example, from the source material region 114 toward the SiC seed crystal 160.

[0014] As mentioned above, in some embodiments, barrier 118 may be implemented with a layer of porous graphite material. In such embodiments, vaporized source material may traverse the pores of the porous graphite material of barrier 118 and enter growth region 112. The inventors of embodiments of the present disclosure recognized that increasing the rate at which vaporized source material may reach growth region 112, and specifically SiC seed crystal 160, may increase the growth rate of the SiC crystal.

[0015] 1A , the vent 130 can serve as an alternative or additional pathway for vapor to travel from the source material region 114 to the growth region 112 and ultimately to the SiC seed crystal 160. Specifically, the vent 130 can serve as an exhaust pathway for vaporized source material to exit the source material region 114 on its way to the SiC seed crystal 160 in the growth region 112. As described above, the heating element 122, in conjunction with the cooling pathway formed by the openings 124 in the thermal insulation layer 120, can create a temperature gradient that decreases in temperature in the direction from the source material region 114 to the growth region 112. Thus, the interior space 133 within the vent 130 can also include a temperature gradient from a first end of the vent 130 located within the source material region 114 to a second end located within (or adjacent to) the growth region 112. Thus, the temperature gradient within the vent 130 can provide a driving force for transporting vapor from the source material region 114 to the growth region 112.

[0016] The size and number of vents, such as vent 130, can be used to control the growth rate of the SiC crystal. For example, increasing the vent area, whether by increasing the number of vents or by increasing the size of the interior space 133 of vent 130, can increase the amount of vapor flowing through such vents toward the SiC seed crystal 160. As another example, increasing the length of one or more vents, such as vent 130, can result in a greater total temperature gradient from a first end of the vent located within source material region 114 to an opposite end located within (or adjacent to) growth region 112. The greater total temperature gradient can then increase the rate at which vapor exits the vent toward the SiC seed crystal 160. Increasing the amount of vapor flowing through one or more vents, such as vent 130, and alternatively or additionally by increasing the vapor velocity, can increase the growth rate of the SiC crystal.

[0017] The configuration of vent 130 can be utilized to further increase the growth rate of SiC crystals. In some embodiments, vent 130 can include graphite sidewalls. For example, one or more of the sidewalls of vent 130 can include a graphite material, such as isotropic graphite. Specifically, one or both of inner sidewall 132 and outer sidewall 131 of vent 130 can be implemented with a graphite material, such as isotropic graphite. As vaporized source material travels through vent 130 from source material region 114 to growth region 112, the vapor can react with carbon in the graphite material forming one or both of the sidewalls of vent 130. Thus, vent 130 can be configured to enrich vapor from source material region 114 with carbon as the vapor passes through vent 130 from source material region 114 to growth region 112. Enriching the vapor with carbon can further increase the growth rate of SiC crystals.

[0018] In some embodiments, the barrier 118 may be implemented with isotropic graphite, which may be less brittle than porous graphite. Therefore, using isotropic graphite to implement one or both of the barrier 118 and the sidewalls of the vent 130 may improve both the manufacturability and reliability of the crystal growth system 100.

[0019] Furthermore, in embodiments in which non-porous isotropic graphite is used to implement barrier 118, vaporized source material can travel from source material region 114 to growth region 112 exclusively through an exhaust path formed by one or more vents, such as vent 130. Thus, in such embodiments, the growth rate can be more tightly controlled by the number and dimensions of one or more vents, such as vent 130, that extend from source material region 114 to growth region 112. As discussed above and below with reference to FIGS. 2-9, the number and dimensions of one or more vents, such as vent 130, can be configured according to the desired release of vaporized source material toward SiC seed crystal 160 and the corresponding growth rate of the SiC crystal.

[0020] 1C shows a top view of a crystal growth system 150 according to some embodiments of the present disclosure. The crystal growth system 150 may include a plurality of vents 135, which may be circular or any other suitable shape, arranged symmetrically about a central axis 180. Collectively, the plurality of vents 135 may function as alternative embodiments of the vent 130 and may share similar configurations and characteristics as the vent 130. In some embodiments, the plurality of vents 135 may share a similar side cross-sectional profile to the profile shown for the vent 130 in FIG. 1A. However, as shown in FIG. 1C, the plurality of vents 135 may be arranged symmetrically along a circle centered on the central axis 180. The multiple vents 135 may also collectively function as alternative embodiments of any of vents 230, 330, 430, 440, or 930 described below with reference to Figures 2, 3, 4, and 9, and may share a similar side cross-sectional profile as any of vents 230, 330, 430, 440, or 930 shown in Figures 2, 3, 4, and 9, respectively.

[0021] 2 shows a cross-sectional side view of a crystal growth system 200 according to some embodiments of the present disclosure. As shown in FIG. 2, the crystal growth system 200 may include a vent 230. The vent 230 may have an interior space 233 defined between an outer sidewall 231 and an inner sidewall 232. The vent 230 may be an alternative embodiment of the vent 130 shown in FIGS. 1A-1B and may share similar configurations, structures, and characteristics as the vent 130.

[0022] The location of the vent 230 can be used to direct the vapor flow toward specific regions of the SiC seed crystal 160 as desired. For example, in the exemplary embodiment of the crystal growth system 100 of FIG. 1A , the vent 130 can be located closer to the central axis 180 of the crucible 110 than to the sidewalls of the crucible 110. In such an embodiment, the vaporized source material can be emitted by the vent 130 toward the central portion of the SiC seed crystal 160. In the exemplary embodiment of the crystal growth system 200 of FIG. 2 , the vent 230 can be located closer to the sidewalls of the crucible 110 than to the central axis 180 of the crucible 110. In such an embodiment, the vaporized source material can be emitted by the vent 130 toward the outer portions of the SiC seed crystal 160.

[0023] 3 shows a cross-sectional side view of a crystal growth system 300 according to some embodiments of the present disclosure. As shown in FIG. 3, the crystal growth system 300 may include a vent 330. The vent 330 may have an interior space 333 defined between an outer sidewall 331 and an inner sidewall 332. The vent 330 may be an alternative embodiment of the vent 130 and may share similar configurations, structures, and characteristics as the vent 130.

[0024] The height of vent 330 can be used to determine the location within source material region 114 where vaporized source material enters vent 130. For example, in the exemplary embodiment of crystal growth system 100 of FIG. 1A, vent 130 can extend into source material region 114 such that a first end of vent 130 can be located within a lower portion of source material region 114. In the exemplary embodiment of crystal growth system 300 of FIG. 3, vent 330 can extend into source material region 114 such that a first end of vent 330 can be located within an upper portion of source material region 114. In either of these embodiments, the first end of the vent, whether vent 130 or vent 330, can be located above or adjacent to the vertical heating center of crucible 110 within source material region 114.

[0025] As described above, the opening 124 can provide a cooling path through the insulating layer 120 and, therefore, together with the heating element 122, can create a temperature gradient within the crucible 110 that decreases in temperature in a direction from the source material region 114 toward the opening 124 adjacent the top of the growth region 112. The configuration and arrangement of the coils of the heating element 122 around the crucible 110 can determine the location of the hottest vertical point within the source material region 114, also referred to herein as the vertical heating center. In some embodiments, the vent 330 can extend into the source material region 114 to a depth such that a first end of the vent 330 within the source material region 114 is located above or adjacent to the vertical heating center. Such placement of the first end of the vent 330 can ensure that the temperature gradient within the interior space 133 of the vent 330 consistently exhibits a decreasing absolute temperature over the entire distance from the first end of the vent 330 located in the source material region 114 to the opposite end of the vent 330 located in (or adjacent to) the growth region 112. Thus, the driving force provided by the temperature gradient within the interior space 333 of the vent 330 can consistently eject vaporized source material from the source material region 114 toward the SiC seed crystal 160 in the growth region 112.

[0026] 4 shows a cross-sectional side view of a crystal growth system 400 according to some embodiments of the present disclosure. In some embodiments, crystal growth system 400 may include multiple vents, such as vent 430 and vent 440. Vent 430 may have an interior space 433 defined between an inner sidewall 432 and an outer sidewall 431. Vent 440 may have an interior space 443 defined between an inner sidewall 442 and an outer sidewall 441. Vents 430 and 440 may be alternative embodiments of vent 130 and may share similar configurations, structures, and characteristics as vent 130.

[0027] Each of multiple vents, such as vent 430 and vent 440, may extend through barrier 118 from source material region 114 to growth region 112. For example, as shown in Figure 4, vent 430 may extend through barrier 118 from source material region 114 to growth region 112. Also shown in Figure 4, vent 440 may also extend through barrier 118 from source material region 114 to growth region 112.

[0028] Vent 440 may have a thickness, as measured by the distance between inner sidewall 442 and outer sidewall 441, that is greater than, less than, or the same as the thickness of vent 430, as measured by the distance between inner sidewall 432 and outer sidewall 431. In some embodiments, vent 430 may be disposed farther from central axis 180 than vent 440.

[0029] 4 shows the first ends of each of the vents 430 and 440 extending into the source material region 114 at the same depth, in some embodiments, the first ends of the vents 430 and 440 may extend into the source material region 114 at different depths. For both types of embodiments, the first end of each of the multiple vents may be located above or near the vertical heating center of the crucible 110. For example, both the vents 430 and 440 may extend into the source material region 114 at a depth that may position the first ends of each of the vents 430 and 440 either above or near the vertical heating center of the crucible 110 within the source material region 114.

[0030] Including two or more vents in the crystal growth system 400 can increase the amount of vaporized source material that travels through the entire vent space to the SiC seed crystal 160. Therefore, including two or more vents in the crystal growth system 400 can increase the growth rate of the SiC crystal. Including two or more vents in the crystal growth system 400 can also provide a more uniform diffusion of the vapor emitted by the vents 430 and 440 across different regions of the SiC seed crystal 160. Therefore, including two or more vents in the crystal growth system 400 can provide a more uniform growth rate across the inner and outer portions of the SiC seed crystal 160. In some embodiments, the crystal growth system 400 can include three or more vents. Also, in some embodiments, the vents can be spaced consistently relative to one another to further provide a uniform growth rate across different portions of the SiC seed crystal 160.

[0031] 5 shows a cross-sectional side view of a crystal growth system 500 according to some embodiments of the present disclosure. As shown in FIG. 5, the crystal growth system 500 may include a source material region 514 along the bottom of the crucible 110, which may abut the sidewall of the crucible 110. The crystal growth system 500 may also include a growth region 512, which may occupy the space above the crucible 110, as well as a central space below the crucible 110 that is not occupied by the source material region 514.

[0032] The crystal growth system 500 may also include a barrier 518. The barrier 518 may be located within the crucible 110 and configured to separate the source material region 514 and the growth region 512. The barrier 518 may be an alternative embodiment of the barrier 118 and may share similar configurations, structures, and properties as the barrier 118. For example, similar to what was described above for the barrier 118 shown in FIG. 1A, the barrier 518 may include either a porous graphite layer or a non-porous isotropic graphite layer. In embodiments in which the barrier 518 is implemented by a non-porous isotropic graphite layer, the flow of vaporized source material from the source material region 514 toward the SiC seed crystal 160 in the growth region 512 may be directed solely by the vent 530.

[0033] 5, the crystal growth system 500 may also include a drainage aid 519. The drainage aid may include either a porous graphite layer or a non-porous isotropic graphite layer. In some embodiments, the drainage aid 519 may be implemented with a different material than the barrier 518. In other embodiments, the drainage aid 519 may be implemented with the same material as the barrier 518 and may be considered part of the barrier 518. For example, in some embodiments, both the barrier 518 and the drainage aid 519 may be implemented with isotropic graphite.

[0034] 5, the vent 530 may be located within the exhaust auxiliary portion 519 and may extend through the exhaust auxiliary portion 519 of the barrier 518 from the source material region 514 to the growth region 512. The vent 530 may have an interior space 533 defined between an outer sidewall 531 and an inner sidewall 532. Also, as shown in the cross-sectional view of FIG. 5, the vent 530 may have an L-shaped cross-sectional shape extending from the source material region 514 to the growth region 512. For example, the vent 530 may have a first portion extending horizontally from a first end adjacent the source material region 514 to an L-curve and a second portion extending vertically from the L-curve to a second end adjacent the growth region 512.

[0035] During crystal growth, heating element 122 can heat the contents of crucible 110, including SiC source material 116 contained within source material region 514. Upon heating, sublimation can occur, causing SiC source material 116 to transition from a solid form to a vapor. Similar to the method described above for FIG. 1A , heating element 122, in conjunction with the cooling path formed by opening 124 in thermal insulation layer 120, can establish a temperature gradient with decreasing temperature in a direction toward opening 124. Thus, vaporized source material can travel vertically through vent 530 and then through growth region 512 toward opening 124 and the SiC seed crystal 160 located at the top of crucible 110 adjacent opening 124.

[0036] The configuration of the exhaust aid 519 and the vent 530 can be utilized to further increase the growth rate of the SiC crystal. In some embodiments, the vent 530 can include graphite sidewalls. For example, the portions of the exhaust aid 519 that form the outer sidewall 531 and inner sidewall 532 of the vent 530 can include a graphite material, such as isotropic graphite. As vaporized source material travels through the vent 530 from the source material region 514 to the growth region 512, the vapor can react with carbon in the graphite material that forms one or both of the sidewalls of the vent 530. Thus, the vent 530 can be configured to enrich the vapor from the source material region 514 with carbon as the vapor passes through the vent 530 from the source material region 514 to the growth region 512. Enriching the vapor with carbon can further increase the growth rate of the SiC crystal.

[0037] 6-9, the number and size of one or more vents, such as vent 530, can determine the amount and rate at which vaporized source material is released toward SiC seed crystal 160. Thus, the number and size of one or more vents, such as vent 530, can be configured according to the desired release of vaporized source material toward SiC seed crystal 160 and the corresponding growth rate of the SiC crystal.

[0038] FIG. 6 shows a cross-sectional side view of a crystal growth system 600 according to some embodiments of the present disclosure. As shown in FIG. 6 , the crystal growth system 600 may include a barrier 618, a drainage auxiliary portion 619, and a vent 630. The vent 630 may have an interior space 633 defined between an outer sidewall 631 and an inner sidewall 632. The vent 630 may be an alternative embodiment of the vent 530 and may share similar configurations, structures, and characteristics as the vent 530. Furthermore, the barrier 618 and the drainage auxiliary portion 619 may be alternative embodiments of the barrier 518 and the drainage auxiliary portion 519, respectively, and may share similar configurations, structures, and characteristics as the barrier 518 and the drainage auxiliary portion 519, respectively.

[0039] The vertical position of the vent 630 can be used to determine the vertical location within the source material region 514 where the vaporized source material enters the vent 630. For example, in the exemplary embodiment of the crystal growth system 500 of FIG. 5, the vent 530 can be located adjacent to the bottom of the source material region 514. In the exemplary embodiment of the crystal growth system 600 of FIG. 6, the vent 630 can be located adjacent to the middle of the source material region 514. In other embodiments, the vent 630 can be located adjacent to the source material region 514 at any vertical location along the side of the source material region 514 suitable for providing an exhaust path for the vaporized source material to exit the source material region 514 and enter the growth region 512. In some embodiments, the vent 630 can be adjacent to the source material region 514 at a vertical location where the vent 630 is located above or near the vertical heating center of the crucible 110.

[0040] FIG. 7 shows a cross-sectional side view of a crystal growth system 700 according to some embodiments of the present disclosure. As shown in FIG. 7 , the crystal growth system 700 may include a barrier 718, a drainage auxiliary portion 719, and a vent 730. The vent 730 may have an interior space 733 defined between an outer sidewall 731 and an inner sidewall 732. The vent 730 may be an alternative embodiment of the vent 530 and may share similar configurations, structures, and characteristics as the vent 730. Furthermore, the barrier 718 and the drainage auxiliary portion 719 may be alternative embodiments of the barrier 518 and the drainage auxiliary portion 519, respectively, and may share similar configurations, structures, and characteristics as the barrier 518 and the drainage auxiliary portion 519, respectively.

[0041] The vertical length of the vent 730 can be used to determine the rate at which vaporized source material from the source material region 514 exits the vent 730 toward the SiC seed crystal 160. Similar to that described above for FIG. 1A , the opening 124 can provide a cooling path through the insulating layer 120 and, thus, in conjunction with the heating element 122, can create a temperature gradient within the crucible 110 that decreases in temperature in a direction from the source material region 514 toward the opening 124 adjacent the top of the growth region 112. For example, by increasing the vertical length of the vent 730 shown in FIG. 7 compared to the vertical length of the vent 530 shown in FIG. 5 , the vertical length of the vent 730 can encompass a greater total temperature gradient. The greater total temperature gradient can then increase the rate at which vapor exits the vent 730 toward the SiC seed crystal 160. By increasing the vapor velocity, the rate of SiC crystal growth can likewise be increased.

[0042] FIG. 8 shows a cross-sectional side view of a crystal growth system 800 according to some embodiments of the present disclosure. As shown in FIG. 8 , the crystal growth system 800 may include a barrier 818, a drainage auxiliary portion 819, and multiple vents, such as vent 830 and vent 840. Vent 830 may have an interior space 833 defined between an inner sidewall 832 and an outer sidewall 831. Vent 840 may have an interior space 843 defined between an inner sidewall 842 and an outer sidewall 841. Vent 830 and vent 840 may be alternative embodiments of vent 530 and may share similar configurations, structures, and characteristics as vent 530. Furthermore, barrier 818 and drainage auxiliary portion 819 may be alternative embodiments of barrier 518 and drainage auxiliary portion 519, respectively, and may share similar configurations, structures, and characteristics as barrier 518 and drainage auxiliary portion 519, respectively.

[0043] Each of the multiple vents, such as vent 830 and vent 840, can extend from the source material region 514 to the growth region 512 through an exhaust auxiliary portion 819 of the barrier 818. For example, as shown in Figure 8, vent 830 can extend from the source material region 514 to the growth region 512 through an L-shaped exhaust auxiliary portion 819. Also shown in Figure 8, vent 840 can extend from the source material region 514 to the growth region 512 through an L-shaped exhaust auxiliary portion 819.

[0044] The inclusion of two or more vents in crystal growth system 800 can increase the amount of vaporized source material that travels through the entire vent space to SiC seed crystal 160. Therefore, the inclusion of two or more vents in crystal growth system 800 can increase the growth rate of the SiC crystal. Furthermore, in embodiments having multiple vents, such as vents 830 and 840 of crystal growth system 800, each of the multiple vents can be adjacent to source material region 514 at a vertical position such that each of the multiple vents is located above or adjacent to the vertical heating center of crucible 110. The inclusion of two or more vents in crystal growth system 800 can also result in more uniform diffusion of the vapor emitted by vents 830 and 840 across different regions of SiC seed crystal 160. Therefore, the inclusion of two or more vents in crystal growth system 800 can result in more uniform growth rates across different portions of SiC seed crystal 160.

[0045] FIG. 9 shows a cross-sectional side view of a crystal growth system 900 according to some embodiments of the present disclosure. As shown in FIG. 9 , the crystal growth system 900 may include a barrier 918, a drainage aid 919, and multiple vents, such as vent 930 and vent 940. The vent 930 may have an interior space 933 defined between an inner sidewall 932 and an outer sidewall 931. The vent 940 may have an interior space 943 defined between an inner sidewall 942 and an outer sidewall 941. As shown in FIG. 9 , the vent 930 may have a linear cross-sectional shape extending from the source material region 514 to the growth region 512. Additionally, the vent 940 may have an L-shaped cross-sectional shape extending from the source material region 514 to the growth region 512. The vent 930 may be an alternative embodiment of the vent 130 and may share similar configurations, structures, and characteristics as the vent 130. Additionally, vent 940 may be an alternative embodiment of vent 530 and may share similar configurations, structures, and characteristics as vent 530. Additionally, barrier 918 and drainage support portion 919 may be alternative embodiments of barrier 518 and drainage support portion 519, respectively, and may share similar configurations, structures, and characteristics as barrier 518 and drainage support portion 519, respectively.

[0046] 9, the vents may have different shapes. For example, a first vent of the plurality of vents, such as vent 930, may have a linear cross-sectional shape extending from the source material region 514 to the growth region 512. Further, a second vent of the plurality of vents, such as vent 940, may have an L-shaped cross-sectional shape extending from the source material region 514 to the growth region 512.

[0047] The inclusion of two or more vents in crystal growth system 900 can increase the amount of vaporized source material that travels through the entire vent space to SiC seed crystal 160. Therefore, the inclusion of two or more vents in crystal growth system 900 can increase the growth rate of SiC crystals. For example, the inclusion of multiple vents, such as a first vent, such as vent 930, having a linear cross-sectional shape and a second vent, such as vent 940, having an L-shaped cross-sectional shape, can result in growth rates that are approximately three times greater than the growth rate of a crystal growth system that does not have a porous graphite barrier and vents separating the source material region and the growth region.

[0048] 10A illustrates a cross-sectional side view of a crystal growth system 1000 according to some embodiments of the present disclosure. Similar to the exemplary embodiment of crystal growth system 100 shown in FIG. 1A, the exemplary embodiment of crystal growth system 1000 in FIG. 10A may include a crucible 110 formed around a central axis 180, a source material region 114, a growth region 112, an insulating layer 120, a heating element 122, an opening 124, a SiC source material 116 located within source material region 114, and a SiC seed crystal 160 located within growth region 112.

[0049] The crystal growth system 1000 may also include a barrier 1018. The barrier 1018 may be configured to separate the source material region 114 and the growth region 112. In some embodiments, the barrier 1018 may be formed of isotropic graphite. Additionally, the barrier 1018 may include a plurality of holes 1030 extending from the source material region 114 on one side of the barrier 1018 to the growth region 112 on the other side of the barrier 1018. Each hole 1030 may be formed in the barrier 1018 by a suitable machining process (physical drilling, milling, cutting) or any other process suitable for forming holes in the barrier 1018. In some embodiments, the holes 1030 may be utilized in combination with one or more vents, such as the vent 130 shown in FIG. 1A , extending from the source material region 114 on one side of the barrier 1018 to the growth region 112 on the other side of the barrier 1018.

[0050] During crystal growth, the heating element 122 can heat the contents of the crucible 110, including the SiC source material 116 contained within the source material region 114. Upon heating, sublimation can occur, causing the SiC source material 116 to transition from a solid form to a vapor. Thus, vaporized source material can flow from the source material region 114 through the plurality of holes 1030 into the growth region 112. As described above, the heating element 122, in conjunction with the cooling path formed by the openings 124 in the thermal insulation layer 120, can establish a temperature gradient that decreases in temperature from the source material region 114 toward the upper region of the growth region 112 adjacent the openings 124. Thus, vaporized source material can migrate toward the SiC seed crystal 160 in the direction of the thermal gradient.

[0051] The size and number of holes 1030 can be used to control the growth rate of the SiC crystal. For example, increasing the total area of ​​the holes 1030, whether by increasing the number of holes 1030 or by increasing the size of individual instances of holes 1030, can increase the amount of vapor that flows through the holes 1030 toward the SiC seed crystal 160.

[0052] 10B shows a top view of a crystal growth system 1000 according to some embodiments of the present disclosure. Specifically, FIG. 10B shows a top view of the crystal growth system 1000 from the perspective of section line B shown in FIG. 10A. As shown in FIGS. 10A and 10B, a plurality of pores 1030 can be distributed across the barrier 1018 in a plane perpendicular to the central axis 180.

[0053] The diffusion of holes 1030 across the barrier 1018 can diffuse vapor released from the holes 1030 into the growth region 112, thus controlling the growth rate across different regions of the SiC seed crystal 160. In some embodiments, the holes 1030 can be uniformly diffused across the barrier 1018 to uniformly diffuse vaporized source material released from the holes 1030 into the growth region 112 and toward the SiC seed crystal 160. In other embodiments, the concentration of holes 1030 can be varied across different regions of the barrier 1018 to separately control the amount of vaporized source material released from the holes 1030 into different regions of the growth region 112 and toward different regions of the SiC seed crystal 160, thereby separately controlling the growth rate across different regions of the SiC seed crystal 160.

[0054] 10C shows a top view of a crystal growth system 1002 according to some embodiments of the present disclosure. The crystal growth system 1002 may include a plurality of holes 1032. The holes 1032 may function as an alternative embodiment of the holes 1030 described above with reference to FIGS. 10A-10B and may be formed in the barrier 1018 in a manner similar to that described above for the holes 1030. As shown in FIG. 10C, each of the plurality of holes 1032 may have a slit shape and may be uniformly distributed throughout the area of ​​the barrier 1018.

[0055] 10D shows a top view of a crystal growth system 1004 according to some embodiments of the present disclosure. The crystal growth system 1004 may include a plurality of holes 1034. The holes 1034 may function as an alternative embodiment of the holes 1030 described above with reference to FIGS. 10A-10B and may be formed in the barrier 1018 in a manner similar to that described above for the holes 1030. As shown in FIG. 10D , each of the plurality of holes 1034 may have a slit shape extending inward toward the central axis 180 and outward toward the inner wall of the crucible 110. In some embodiments, the plurality of holes 1034 may be spaced radially symmetrically about the central axis 180.

[0056] FIG. 10E shows a top view of a crystal growth system 1006 according to some embodiments of the present disclosure. The crystal growth system 1006 may include a plurality of holes 1036. The holes 1036 may function as an alternative embodiment of the holes 1030 described above with reference to FIGS. 10A-10B and may be formed in the barrier 1018 in a manner similar to that described above for the holes 1030. As shown in FIG. 10E, each of the plurality of holes 1036 may have a slit shape extending inward toward the central axis 180 and outward toward the inner wall of the crucible 110. Also shown in FIG. 10E, a group of the plurality of holes 1036, e.g., three instances of holes 1036, may be arranged along a linear path facing inward toward the central axis 180 and outward toward the inner wall of the crucible 110. Furthermore, different groups of the plurality of holes 1036 may be spaced radially symmetrically about the central axis 180.

[0057] FIG. 11 illustrates a method 1100 for growing SiC crystals according to some embodiments of the present invention. Method 1100 may be performed by any suitable mechanism, such as a component of crystal growth system 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1002, 1004, or 1006. Method 1100 may be performed with fewer or more steps than shown in FIG. 11. Furthermore, steps of method 1100 may be omitted, repeated, performed in parallel, performed in a different order than shown in FIG. 11, or performed recursively. One or more steps of method 1100, while shown sequentially, may be performed simultaneously or reordered.

[0058] Step 1102 may include placing a SiC seed crystal in a growth region within the crucible. For example, SiC seed crystal 160 may be placed in growth region 112.

[0059] Step 1104 may include providing a SiC source material to a source material region within the crucible. For example, SiC source material 116 may be provided to source material region 114 within crucible 110.

[0060] Step 1106 may include providing a barrier between the source material region and the growth region. For example, a barrier 118 may be provided between the source material region 114 and the growth region 112 in the crucible 110.

[0061] Step 1108 may include heating the SiC source material to generate vapor. For example, heating element 122 may heat the contents of crucible 110, including SiC source material 116 in source material region 114. The heating may cause SiC source material 116 to sublimate, thereby generating vapor in the form of vaporized source material.

[0062] Step 1110 may include establishing a temperature gradient that decreases in temperature in a direction from the source material toward the SiC seed crystal. For example, as described above with reference to FIG. 1A , the openings 124 may provide a cooling path through the thermal insulation layer 120. Thus, the heating element 122 and the openings 124 together can create a temperature gradient in the crucible 110 that decreases in temperature in a direction from the SiC source material 116 in the source material region 114 toward the SiC seed crystal 160 located in the portion of the growth region 112 adjacent the openings 124.

[0063] Step 1112 may provide at least one vent extending through the barrier from the source material region to the growth region to define an exhaust path for vapor from the source material region to the growth region. For example, a vent such as vent 130 may be provided. As shown in FIG. 1A , vent 130 may extend through barrier 118 from source material region 114 to growth region 112. As another example, a vent such as vent 530 may be provided. Vent 530 may extend from source material region 514 to growth region 512 through exhaust auxiliary portion 519 of barrier 518.

[0064] Step 1114 may include condensing the vapor with carbon as it passes through at least one vent from the source material region to the growth region. For example, as described above with reference to FIG. 1A , one or more of the sidewalls of vent 130 may include a graphite material, such as isotropic graphite. Specifically, one or both of inner sidewall 132 and outer sidewall 131 of vent 130 may be implemented with a graphite material, such as isotropic graphite. As vaporized source material travels through vent 130 from source material region 114 to growth region 112, the vapor may react with carbon in the graphite material forming one or both of the sidewalls of vent 130. Thus, vent 130 may be configured to condense vapor from source material region 114 with carbon as it passes through vent 130 from source material region 114 to growth region 112.

[0065] Some embodiments herein may include a growth system. The growth system includes a crucible at least partially surrounded by a thermal insulation layer and a growth region located within the crucible and configured to hold a silicon carbide (SiC) seed crystal. The growth system further includes a source material region located within the crucible and configured to hold a SiC source material. In addition, the growth system includes a barrier located within the crucible and configured to separate the source material region and the growth region. The growth system further includes a heating element located around the crucible and configured, together with an opening in the thermal insulation layer, to provide a temperature gradient that decreases in temperature in a direction from the source material region toward the growth region. In addition, the growth system includes a vent extending through the barrier from the source material region to the growth region.

[0066] The growth system may also have one or more of the following additional elements, in any combination: Element 1: The barrier comprises isotropic graphite. Element 2: The growth system further comprises a plurality of holes extending through the barrier from the source material region to the growth region. Element 3: The barrier comprises porous graphite. Element 4: The vent comprises a graphite sidewall configured to condense vapor from the source material region with carbon as the vapor passes through the vent from the source material region to the growth region. Element 5: The vent comprises isotropic graphite. Element 6: The vent has an inner sidewall having a first cylindrical shape centered on the central axis of the crucible and an outer sidewall having a second cylindrical shape centered on the central axis of the crucible, the first cylindrical shape having a first diameter smaller than a second diameter of the second cylindrical shape. Element 7: The first end of the vent is located proximate to a vertical heating center of the crucible within the source material region, and the second end of the vent extends into the growth region. Element 8: The vent has a linear cross-sectional shape extending from the source material region to the growth region. Element 9: The vent has an L-shaped cross-sectional shape extending from the source material region to the growth region. Element 10: The growth system includes a plurality of vents, each of the plurality of vents extending through a barrier from the source material region to the growth region. Element 11: A first vent and a second vent of the plurality of vents each have a linear cross-sectional shape extending from the source material region to the growth region. Element 12: A first vent and a second vent of the plurality of vents each have an L-shaped cross-sectional shape extending from the source material region to the growth region. Element 13: A first vent of the plurality of vents has a linear cross-sectional shape extending from the source material region to the growth region and a second vent of the plurality of vents has an L-shaped cross-sectional shape extending from the source material region to the growth region.

[0067] Some embodiments herein may include a growth system. The growth system includes a crucible at least partially surrounded by an insulating layer and a growth region located within the crucible and configured to hold a silicon carbide (SiC) seed crystal. The growth system further includes a source material region located within the crucible and configured to hold a SiC source material. In addition, the growth system includes a barrier located within the crucible and configured to separate the source material region and the growth region. The growth system further includes a heating element located around the crucible and configured, together with an opening in the insulating layer, to provide a temperature gradient in which the temperature decreases in a direction from the source material region toward the growth region. In addition, the growth system includes a plurality of holes extending through the barrier from the source material region to the growth region. The growth system may further include the following additional elements: Element 1: The barrier includes isotropic graphite.

[0068] Some embodiments herein may include a method for controlling the growth of silicon carbide (SiC) crystals. The method may include: placing a SiC seed crystal in a growth region within a crucible; supplying a SiC source material to a source material region within the crucible; providing a barrier between the source material region and the growth region; heating the SiC source material to generate vapor; providing a temperature gradient that decreases in temperature in a direction from the source material to the SiC seed crystal; and providing at least one vent extending through the barrier from the source material region to the growth region, defining an exhaust path for the vapor from the source material region to the growth region.

[0069] The method may have one or more of the following additional elements in any combination: Element 1: The barrier comprises isotropic graphite; Element 2: The barrier further comprises a plurality of holes extending through the barrier from the source material region to the growth region; Element 3: Concentrating the vapor with carbon as it passes through at least one vent from the source material region to the growth region.

[0070] Although examples have been described herein in terms of vertical positions, depths, or heights where the vertical direction is parallel to the direction of central axis 180, the disclosure is not so limited. For example, in embodiments where the positioning of crucible 110 and the components therein is rotated 90 degrees so that central axis 180 is horizontal rather than vertical, references herein to vertical dimensions or positions may equally apply to horizontal dimensions or positions.

[0071] Although examples have been described above, other modifications and variations may be made from this disclosure without departing from the spirit and scope of these examples. The above description of various embodiments illustrates the principles of the present invention. Numerous variations and modifications will be apparent to those skilled in the art based on the above disclosure. It is intended that the following claims be interpreted to encompass all such variations and modifications.

Claims

1. A growth system, a crucible at least partially surrounded by a thermal insulating layer; a growth region located within the crucible and configured to hold a silicon carbide (SiC) seed crystal; a source material region located within the crucible and configured to hold a SiC source material; a barrier positioned within the crucible and configured to separate the source material region and the growth region; a heating element positioned around the crucible and configured, together with the opening in the thermal insulation layer, to provide a temperature gradient with a decreasing temperature in a direction from the source material towards the growth region; a vent extending through the barrier from the source material region to the growth region.

2. The growth system of claim 1 , wherein the barrier comprises isotropic graphite.

3. 10. The growth system of claim 1, wherein the vent comprises a graphite sidewall configured to enrich vapors from the source material region with carbon as the vapors pass through the vent from the source material region to the growth region.

4. 2. The growth system of claim 1, wherein a first end of the vent is located proximate a vertical heating center of the crucible within the source material region and a second end of the vent extends into the growth region.

5. A growth system, a crucible at least partially surrounded by a thermal insulating layer; a growth region located within the crucible and configured to hold a silicon carbide (SiC) seed crystal; a source material region located within the crucible and configured to hold a SiC source material; a barrier positioned within the crucible and configured to separate the source material region and the growth region; a heating element positioned around the crucible and configured, together with the opening in the thermal insulation layer, to provide a temperature gradient with a decreasing temperature in a direction from the source material towards the growth region; a plurality of holes extending through the barrier from the source material region to the growth region.

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