Method and apparatus for growing silicon carbide crystal

Abstract

The application relates to the technical field of crystal growth, in particular to a silicon carbide crystal growth method and a crystal growth device. The silicon carbide crystal growth method comprises the following steps: setting the temperature of the surface of silicon carbide powder to 2000-2400 DEG C; reducing the temperature at the top of a crystal growth zone to 1800-2300 DEG C; wherein, during the crystal growth process, the temperature is set as follows: in the initial growth stage, the temperature gradient between the temperature of the surface of the silicon carbide powder and the temperature at the top of the crystal growth zone is 50-200 DEG C; in the middle growth stage, the temperature gradient between the temperature of the surface of the silicon carbide powder and the temperature at the top of the crystal growth zone is 50-100 DEG C; and in the late growth stage, the temperature gradient between the temperature of the surface of the silicon carbide powder and the temperature at the top of the crystal growth zone is 0-50 DEG C.

Description

Technical Field

[0001] This invention relates to the field of crystal growth technology, and more specifically, to a method and apparatus for growing silicon carbide crystals. Background Technology

[0002] In existing silicon carbide crystal growth processes, when the sublimated gas phase from the silicon carbide powder reaches the interface with the growth chamber (i.e., the surface of the silicon carbide powder), the interface temperature decreases, resulting in the formation of numerous crystals on the silicon carbide powder surface. This excessive crystal formation on the silicon carbide powder surface not only affects subsequent powder sublimation and the growth of crystals at the top of the crucible, but also renders the surface crystals unsellable as a product, reducing powder utilization and crystal yield.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for growing silicon carbide crystals. Embodiments of this invention provide a crystal growth method that enables the material crystallizing on the surface of silicon carbide powder to grow normally into the desired single or polycrystalline form, thereby improving the utilization rate of the powder and the yield of the crystals.

[0005] This invention is implemented as follows: In a first aspect, the present invention provides a method for growing silicon carbide crystals, comprising: setting the temperature of the surface of silicon carbide powder to 2000-2400℃; The temperature at the top of the crystal growth region is reduced to 1800-2300℃; The temperature settings during the crystal growth process are as follows: In the initial stage of growth, the temperature gradient between the surface temperature of the silicon carbide powder and the top temperature of the crystal growth region is 50-200℃. During the middle stage of growth, the temperature gradient between the surface of the silicon carbide powder and the top of the crystal growth region is 50-100℃. During the later stages of growth, the temperature gradient between the surface of the silicon carbide powder and the top of the crystal growth region is 0-50℃.

[0006] In an optional implementation, the first seed crystal is placed at an angle deviating from the C-axis. <1120> Direction 0-4 o , preferably 1 o .

[0007] In an optional embodiment, the surface temperature of the silicon carbide powder during the middle and later stages of growth is higher than that of the silicon carbide powder during the early stages of growth.

[0008] In a second aspect, the present invention provides a silicon carbide crystal growth apparatus, which is used to implement the silicon carbide crystal growth method described in any of the foregoing embodiments. It includes: a crucible, a seed crystal holder with vents, multiple tantalum carbide backplates, and multiple first seed crystals. The seed crystal holder is disposed inside the crucible and on silicon carbide powder. The multiple tantalum carbide backplates are respectively disposed on the seed crystal holder and connected to the seed crystal holder. The multiple first seed crystals are respectively disposed on one side of the multiple tantalum carbide backplates and connected to the seed crystal holder.

[0009] In an optional embodiment, the distance between two adjacent tantalum carbide backplates is 20-50 mm; Preferably, the plurality of tantalum carbide backplates are arranged in a radial direction.

[0010] In an optional embodiment, the distance between the seed crystal holder and the surface of the silicon carbide powder is 0-0.3 times the crystal diameter.

[0011] In an optional embodiment, the crystal growth apparatus further includes a porous tantalum carbide backplate assembly, which is disposed inside and connected to the crucible, and the porous tantalum carbide backplate is disposed on the side of the tantalum carbide backplate that is relatively far away from the seed crystal holder.

[0012] In an optional embodiment, the porous tantalum carbide backplate assembly includes at least two porous tantalum carbide backplates, which are arranged along the axial direction and are both located on the side of the tantalum carbide backplate that is relatively far away from the seed crystal frame. The pores of the two porous tantalum carbide backplates are staggered.

[0013] In an optional embodiment, the distance between the two porous tantalum carbide backplates is 0.5-0.8 times the crystal diameter; Preferably, tantalum carbide particles are disposed between the two porous tantalum carbide backplates; Preferably, the stacking thickness of the tantalum carbide particles is 2-5 mm.

[0014] In an optional embodiment, a second seed crystal is provided on the top of the crucible.

[0015] The present invention has the following beneficial effects: The embodiments of the present invention provide a crystal growth method, which, by setting a seed crystal frame and a first seed crystal on the surface of existing silicon carbide powder, enables the direct crystal growth of the fumed powder reaching the surface of the silicon carbide powder, thus fully utilizing the fumed powder reaching the surface of the silicon carbide powder and improving the powder utilization rate. Simultaneously, the fumed powder still grows at the top of the crucible to obtain the desired crystal, further improving the crystal yield. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the structure of the silicon carbide crystal growth device provided in an embodiment of the present invention; Figure 2 A schematic diagram showing the positions of the first graphite sheet and the second graphite sheet provided for an embodiment of the present invention; Figure 3 This is a schematic diagram of the crucible provided in Comparative Example 1 of the present invention.

[0018] Icons: 100 - Crystal growth apparatus for silicon carbide crystals; 110 - Crucible; 120 - Silicon carbide powder; 121 - First graphite sheet; 130 - Seed crystal holder; 131 - Pores; 140 - First seed crystal; 150 - Tantalum carbide backplate; 160 - Porous tantalum carbide backplate assembly; 161 - Porous tantalum carbide backplate; 170 - Second graphite sheet; 180 - Second seed crystal. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] This invention provides a method for growing silicon carbide crystals, comprising: setting the temperature of the surface of silicon carbide powder to 2000-2400℃; for example, any value between 2000-2400℃ such as 2000℃, 2100℃, 2200℃, 2300℃ or 2400℃.

[0021] Specifically, the temperature at the lowest part of the crystal growth region inside the crucible is 2000-2400℃, and the temperature at the top of the crystal growth region is 1800-2300℃. Using these temperatures is conducive to crystal growth and obtaining the desired crystal.

[0022] Specifically, the temperature settings during crystal growth are as follows: In the initial stage of growth, the temperature gradient between the surface of the silicon carbide powder and the top of the crystal growth zone is 50-200℃; for example, any value between 50℃, 100℃, 150℃, or 200℃. This promotes the growth of the seed crystal in the vertical direction. However, the overall temperature should be relatively low to avoid excessively rapid temperature changes at the seed crystal support, which could damage the seed crystal structure.

[0023] During the mid-growth stage, the temperature gradient between the surface of the silicon carbide powder and the top of the crystal growth region is 50-100°C; the above temperature gradient is used to ensure stable growth of the seed crystal frame and the top seed crystal.

[0024] During the later stages of growth, the temperature gradient between the surface of the silicon carbide powder and the top of the crystal growth region is 0-50°C. This temperature gradient slows down the horizontal growth of the seed crystal, promotes recrystallization of the crystals on the seed crystal, improves crystal quality, and avoids clogging of the gas channels, which would affect the growth of the top crystal.

[0025] Furthermore, the surface temperature of the silicon carbide powder during the middle and later stages of growth is higher than that during the early stages of growth, thereby increasing the amount of powder sublimation and promoting crystal growth at various locations.

[0026] Furthermore, the first seed crystal is placed at an angle offset from the C-axis. <1120> Direction 0-4 o , preferably 1 o The seed crystal is set up in the seed crystal holder in the manner described above, and a small number of steps are provided to prevent the crystal from growing too fast in the horizontal direction, which would reduce the quality of the wafer and block the airflow channels, thereby reducing defects such as phase transitions and dislocations.

[0027] In summary, the crystal growth method provided by the embodiments of the present invention enables the formation of crystals along the surface of silicon carbide powder from fumed powder, thereby improving the utilization rate of the powder and increasing the yield of crystals.

[0028] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0029] Example 1 See Figure 1 This invention provides a silicon carbide crystal growth apparatus 100, which includes a crucible 110 that provides the necessary space for crystal growth.

[0030] It should be noted that the shape and size of the crucible 110 are not limited. It can be an oval or square crucible, or it can be placed inside a round crucible.

[0031] Furthermore, silicon carbide powder 120 is placed inside the crucible 110, and a seed crystal holder 130 is placed on the silicon carbide powder 120. The seed crystal holder 130 can be placed directly on the silicon carbide powder 120.

[0032] Understandably, the seed crystal holder 130 can maintain a certain distance from the surface of the silicon carbide powder 120, in which case the seed crystal holder 130 is connected to the crucible 110. Furthermore, the distance between the seed crystal holder 130 and the surface of the silicon carbide powder 120 is less than 0.3 times the crystal diameter, which is beneficial for subsequent crystal growth. At the same time, the silicon carbide powder 120 does not necessarily fill the top of the powder area.

[0033] The crucible 110 also includes a plurality of first graphite sheets 121 for testing the surface temperature of the silicon carbide powder 120. Specifically, the plurality of first graphite sheets 121 are all disposed outside the crucible 110 and arranged in a ring around the circumference of the crucible 110. At the same time, the first graphite sheets 121 are located on the silicon carbide powder 120. The surface temperature of the silicon carbide powder 120 can be obtained by testing the temperature of the plurality of first graphite sheets 121 and then taking their average value.

[0034] Furthermore, the seed crystal holder 130 is provided with pores 131 to provide a stable airflow for the growth of the first seed crystal 140. The seed crystal holder 130 is made of graphite.

[0035] Specifically, a first seed crystal 140 is disposed on the seed crystal holder 130, and the first seed crystal 140 is determined according to the crystal to be grown. The angle of the first seed crystal 140 on the seed crystal holder 130 is off-center along the C-axis. <1120> Direction 0-4 o , preferably 1 o A few steps are provided to prevent the product from growing too fast in the horizontal direction, which would reduce the quality of the product and block the airflow channels, thereby reducing defects such as phase transitions and dislocations.

[0036] Furthermore, the system also includes multiple tantalum carbide backplates 150, which are respectively disposed on and connected to the seed crystal holder 130. Multiple first seed crystals 140 are respectively disposed on one side of each of the multiple tantalum carbide backplates 150 and connected to the seed crystal holder 130. In other words, the tantalum carbide backplates 150 are disposed in the non-porosity area of ​​the seed crystal holder 130, while the first seed crystals 140 are adhered to the tantalum carbide backplates, thereby facilitating crystal growth.

[0037] Preferably, first seed crystals 140 are provided on both sides of the tantalum carbide back plate 150 located in the middle of the crucible 110, and then the crystals on both sides of the tantalum carbide back plate 150 in the middle part grow symmetrically, which can further improve the crystal yield.

[0038] Furthermore, the distance between two adjacent tantalum carbide backplates 150 is 20-50 mm; this facilitates gas diffusion, crystallization, and crystal growth, ensuring the quality of the formed crystal. The length of the tantalum carbide backplate 150 is determined according to the specifications of the prepared crystal.

[0039] Furthermore, multiple tantalum carbide backplates 150 are arranged radially. Each tantalum carbide backplate is attached with a first seed crystal 140, thereby further improving the crystal yield.

[0040] Furthermore, the crystal growth apparatus also includes a porous tantalum carbide backplate assembly 160 with pores 131. The porous tantalum carbide backplate assembly 160 is disposed within and connected to the crucible 110, and the porous tantalum carbide backplate 161 is disposed on the side of the tantalum carbide backplate 150 relatively away from the seed crystal holder 130, that is, the porous tantalum carbide backplate assembly 160 is disposed on top of the tantalum carbide backplate 150. Specifically, the distance between the top of the porous tantalum carbide backplate assembly 160 and the top of the tantalum carbide backplate 150 is 0.3-1.2 times the crystal diameter.

[0041] Specifically, the porous tantalum carbide backplate assembly 160 includes at least two porous tantalum carbide backplates 161, with the at least two porous tantalum carbide backplates 161 arranged along the axial direction, and the distance between the two porous tantalum carbide backplates 161 being 0.5-0.8 times the crystal diameter, in order to ensure the diffusion of the gas phase.

[0042] Furthermore, the pores 131 of the two porous tantalum carbide backplates 161 are staggered to redistribute the airflow into a normal distribution state for the normal growth of the top crystal.

[0043] The two vented tantalum carbide backplates 161 are disposed between tantalum carbide particles; and the stacking thickness of the tantalum carbide particles is 2-5mm. The placement of tantalum carbide particles and the stacking thickness are more conducive to the redistribution of airflow to form a normal distribution.

[0044] Further, see Figure 2 The system also includes multiple second graphite sheets 170. The second graphite sheets 170 are disposed outside and connected to the crucible 110, and are arranged in a ring around the crucible 110. Simultaneously, the second graphite sheets 170 are positioned on the side of one of the two porous tantalum carbide backplates 161 that is relatively far from the top of the crucible 110. The temperature of the top of the crystal growth region is then obtained by testing the temperatures of the multiple second graphite sheets 170 and taking the average value. Multiple first graphite sheets 121 and multiple second graphite sheets 170 are arranged at intervals.

[0045] Furthermore, a second seed crystal 180 is provided on the top of the crucible 110, and the crystal on the top can grow normally.

[0046] Example 2 This invention provides a method for growing silicon carbide crystals. The method uses the silicon carbide crystal growth apparatus provided in Example 1. In this method, the seed crystal holder 130 can be 0.1 times the crystal diameter away from the surface of the silicon carbide powder 120. Specifically, the method includes: Specifically, the temperature settings during the crystal growth process are as follows: in the initial stage of growth, the temperature of the surface of the silicon carbide powder is 2080℃; the temperature of the top of the crystal growth region is 1935℃.

[0047] During the middle stage of growth, the surface temperature of the silicon carbide powder is 2176°C; the temperature at the top of the crystal growth region is 2103°C. During the later stages of growth, the surface temperature of the silicon carbide powder is 2245°C; the temperature at the top of the crystal growth region is 2208°C.

[0048] The first seed crystal is placed at an angle offset from the C-axis. <1120> Direction 0.5 o The second seed crystal, positioned at the top of crucible 110, is placed at an angle offset from the C-axis. <1120> Direction 4 o .

[0049] The required mass of silicon carbide crystal formed on the top of crucible 110 is 1948g, the required total mass of crystal formed on the seed crystal holder is 623g, and the mass of polycrystalline material formed on the powder pile is 121g.

[0050] Example 3 This invention provides a method for growing silicon carbide crystals. The method uses the silicon carbide crystal growth apparatus provided in Example 1. In this method, the seed crystal holder 130 is directly placed on the silicon carbide powder 120. Specifically, the method includes: Specifically, the temperature settings during the crystal growth process are as follows: in the initial stage of growth, the temperature of the surface of the silicon carbide powder is 2066℃; the temperature of the top of the crystal growth region is 1938℃. During the middle stage of growth, the surface temperature of the silicon carbide powder is 2191°C; the temperature at the top of the crystal growth region is 2122°C. During the later stages of growth, the surface temperature of the silicon carbide powder is 2220℃; the temperature at the top of the crystal growth region is 2203℃.

[0051] The first seed crystal is placed at an angle offset from the C-axis. <1120> Direction 1 o The second seed crystal, positioned at the top of crucible 110, is placed at an angle offset from the C-axis. <1120> 4 o .

[0052] The required mass of silicon carbide crystal formed on the top of crucible 110 is 1738g, the required total mass of crystal formed on the seed crystal holder is 404g, and the mass of polycrystalline material formed on the powder pile is 86g.

[0053] Example 4 This invention provides a method for growing silicon carbide crystals. The method uses the silicon carbide crystal growth apparatus provided in Example 1. In this method, the seed crystal holder 130 can be 0.2 times the crystal diameter away from the surface of the silicon carbide powder 120. Specifically, the method includes: Specifically, the temperature settings during the crystal growth process are as follows: in the initial stage of growth, the temperature of the surface of the silicon carbide powder is 2086℃; the temperature of the top of the crystal growth region is 1924℃. During the middle stage of growth, the surface temperature of the silicon carbide powder is 2198°C; the temperature at the top of the crystal growth region is 2141°C. During the later stages of growth, the surface temperature of the silicon carbide powder is 2236°C; the temperature at the top of the crystal growth region is 2224°C.

[0054] The first seed crystal is placed at an angle offset from the C-axis. <1120> Direction 0 o The second seed crystal, positioned at the top of crucible 110, is placed at an angle offset from the C-axis. <1120> Direction 4 o .

[0055] The required mass of silicon carbide crystal formed on the top of crucible 110 is 2023g, the required total mass of crystal formed on the seed crystal holder is 434g, and the mass of polycrystalline material formed on the powder pile is 107g.

[0056] Comparative Example 1 Comparative Example 1 provides a method for growing silicon carbide crystals. The equipment used in this method is a conventional crucible, the structure of which is described in [reference needed]. Figure 3 The crucible only has a seed crystal at the top, and it does not have a seed crystal holder with pores, multiple tantalum carbide back plates, or a tantalum carbide back plate assembly with pores.

[0057] The temperature settings in the crystal growth method provided in Comparative Example 1 are as follows: During the initial growth stage, the surface temperature of the silicon carbide powder is 2207℃; the temperature at the top of the crystal growth region is 2051℃. During the middle stage of growth, the surface temperature of the silicon carbide powder is 2210°C; the temperature at the top of the crystal growth region is 2056°C.

[0058] During the later stages of growth, the surface temperature of the silicon carbide powder is 2215°C; the temperature at the top of the crystal growth region is 2061°C.

[0059] The second seed crystal at the top of crucible 110 is placed at an angle of 4° off the C-axis, and no seed crystal is placed on the powder.

[0060] The required mass of silicon carbide crystal formed at the top of crucible 110 is 1992g, and the mass of polycrystalline material formed on the powder pile is 577g.

[0061] Comparing Example 3 and Comparative Example 1, it can be seen that the amount of silicon carbide crystals obtained by using the crystal growth device provided in the embodiments of the present invention is significantly increased, and the amount of polycrystalline material formed on the powder pile is significantly reduced, indicating that it can improve the utilization rate of powder and increase the yield of silicon carbide crystals.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for growing silicon carbide crystals, characterized in that, include: Set the surface temperature of the silicon carbide powder to 2000-2400℃; The temperature at the top of the crystal growth region is reduced to 1800-2300℃; The temperature settings during the crystal growth process are as follows: In the initial stage of growth, the temperature gradient between the surface temperature of the silicon carbide powder and the top temperature of the crystal growth region is 50-200℃. During the middle stage of growth, the temperature gradient between the surface of the silicon carbide powder and the top of the crystal growth region is 50-100℃. During the later stages of growth, the temperature gradient between the surface of the silicon carbide powder and the top of the crystal growth region is 0-50℃. The first seed crystal is placed at an angle offset from the C-axis. <1120> Direction 0-4 o ; The surface temperature of the silicon carbide powder during the mid- and late-stage growth is higher than that during the early-stage growth.

2. The method for growing silicon carbide crystals according to claim 1, characterized in that, The first seed crystal is placed at an angle offset from the C-axis. <1120> Direction 1 o .

3. A crystal growth apparatus for silicon carbide crystals, characterized in that, The silicon carbide crystal growth apparatus is used to implement the silicon carbide crystal growth method according to claim 1 or 2; The device includes: a crucible, a seed crystal holder with vents, multiple tantalum carbide backplates, and multiple first seed crystals. The seed crystal holder is disposed inside the crucible and on silicon carbide powder. The multiple tantalum carbide backplates are respectively disposed on the seed crystal holder and connected to the seed crystal holder. The multiple first seed crystals are respectively disposed on one side of the multiple tantalum carbide backplates and connected to the seed crystal holder. The crystal growth apparatus also includes a porous tantalum carbide backplate assembly, which is disposed inside and connected to the crucible, and the porous tantalum carbide backplate is disposed on the side of the tantalum carbide backplate that is relatively far away from the seed crystal frame. The porous tantalum carbide backplate assembly includes at least two porous tantalum carbide backplates. The at least two porous tantalum carbide backplates are arranged along the axial direction and are both located on the side of the tantalum carbide backplate that is relatively far away from the seed crystal frame. The pores of the two porous tantalum carbide backplates are staggered.

4. The silicon carbide crystal growth apparatus according to claim 3, characterized in that, The distance between two adjacent tantalum carbide backplates is 20-50 mm.

5. The silicon carbide crystal growth apparatus according to claim 3, characterized in that, Multiple tantalum carbide backplates are arranged in the radial direction.

6. The silicon carbide crystal growth apparatus according to claim 4, characterized in that, The distance between the seed crystal holder and the surface of the silicon carbide powder is 0-0.3 times the crystal diameter.

7. The silicon carbide crystal growth apparatus according to claim 4, characterized in that, The distance between the two porous tantalum carbide backplates is 0.5-0.8 times the crystal diameter.

8. The silicon carbide crystal growth apparatus according to claim 4, characterized in that, The two porous tantalum carbide backplates are disposed between tantalum carbide particles.

9. The silicon carbide crystal growth apparatus according to claim 8, characterized in that, The stacking thickness of the tantalum carbide particles is 2-5 mm.

10. The silicon carbide crystal growth apparatus according to claim 4, characterized in that, A second seed crystal is provided on the top of the crucible.

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