Growth device of silicon carbide crystal and application of growth device

Abstract

The invention provides a silicon carbide crystal growth device and application thereof, the growth device at least comprises: a crucible comprising a side part and a bottom, the side part surrounding one side of the bottom; the cover body is arranged on one side, far away from the bottom, of the side part; the first heater is arranged outside the crucible in a surrounding manner and is arranged close to one side of the cover body; the second heater is arranged outside the crucible in a surrounding manner and is close to one side of the bottom, and a preset distance is kept between the second heater and the first heater; the third heaters are arranged on the side, away from the crucible, of the cover body at intervals; the silicon carbide powder is filled on one side, close to the side part, of the bottom part; and the silicon carbide seed crystal is hung on one side, close to the crucible, of the cover body. According to the growth device of the silicon carbide crystal and the application of the growth device, the high-quality large-diameter silicon carbide crystal can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal preparation, and in particular to a growth device for silicon carbide crystals and its application. Background Art

[0002] With the development of semiconductor technology, 12-inch silicon carbide substrates have the advantages of low cost and high utilization rate compared with 8-inch and 6-inch silicon carbide substrates, and are attracting more and more attention from downstream manufacturers. Among them, due to the large size of 12-inch silicon carbide substrates, a larger growth device is required to accommodate silicon carbide powder during the crystal growth process. However, in current large-scale growth devices, it is difficult to accurately control the radial and axial temperature gradients, resulting in a large number of defects such as microtubes, grain boundaries, and dislocations in the crystal, and even a large number of cracks and cracking in the crystal, which affects the preparation of large-diameter silicon carbide crystals. Moreover, due to the temperature gradient, the temperature of the silicon carbide powder in the central region of the growth device is low and cannot be fully sublimated, resulting in low utilization rate of the silicon carbide powder, waste of resources, and increased preparation cost. Summary of the Invention

[0003] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a growth device for silicon carbide crystals and its application, which can regulate the radial and axial temperature gradients in the growth device, obtain high-quality large-diameter silicon carbide crystals, and can also improve the utilization rate of silicon carbide powder in the growth device, avoid waste of resources, and reduce the preparation cost.

[0004] To solve the above technical problems, the present invention is realized through the following technical solutions.

[0005] The present invention provides a growth device for silicon carbide crystals, which at least includes:

[0006] A crucible, including a side portion and a bottom portion, and the side portion is disposed around one side of the bottom portion;

[0007] A cover body, disposed on the side of the side portion away from the bottom portion;

[0008] A first heater, disposed around the crucible and close to the side of the cover body;

[0009] A second heater, disposed around the crucible and close to the side of the bottom portion, and a preset distance is maintained between the second heater and the first heater;

[0010] A third heater, spacedly disposed on the side of the cover body away from the crucible;

[0011] Silicon carbide powder, filled on the side of the bottom portion close to the side portion; and

[0012] A silicon carbide seed crystal is suspended on one side of the cover body close to the crucible.

[0013] In an embodiment of the present invention, the growth device further includes a convex portion, which protrudes from the center of the bottom towards the cover body side.

[0014] In an embodiment of the present invention, the growth device further includes a fourth heater, which is arranged inside the convex portion.

[0015] In an embodiment of the present invention, one side of the first heater close to the bottom is higher than the plane where the surface of the silicon carbide powder material is located, and one side of the second heater close to the cover body is lower than the plane where the surface of the silicon carbide powder material is located.

[0016] In an embodiment of the present invention, the growth device further includes an expanding ring, which is arranged between the cover body and the side portion around the first part and extends towards the direction of the bottom.

[0017] In an embodiment of the present invention, in the direction from the cover body towards the bottom, the inner diameter of the expanding ring becomes larger.

[0018] In an embodiment of the present invention, one side of the expanding ring away from the cover body is in contact with the silicon carbide powder material.

[0019] The present invention also provides a method for growing a silicon carbide crystal, which at least includes the following steps

[0020] Provide the above-mentioned growth device for silicon carbide crystals;

[0021] Place the growth device in a cavity, and after the first vacuum pumping of the cavity, heat the cavity to a first temperature;

[0022] After introducing a protective gas into the cavity to a first pressure, perform a second vacuum pumping on the cavity, and repeat the steps of introducing the protective gas and the second vacuum pumping for a preset number of times;

[0023] After introducing nitrogen into the cavity to a second pressure, reduce the pressure in the cavity to a third pressure and maintain it for a first period of time;

[0024] Raise the temperature of the cavity from the first temperature to a second temperature and maintain it for a second period of time; and

[0025] After introducing the protective gas into the cavity to a fourth pressure, cool the cavity, take out the growth device, and obtain a silicon carbide crystal.

[0026] In an embodiment of the present invention, the first temperature is 1700°C - 1900°C, the protective gas includes at least one of argon and helium, the first pressure is 500 mbar - 700 mbar, the flow rate of nitrogen introduced is 6 mL / min - 50 mL / min, the second pressure is 400 mbar - 800 mbar, the third pressure is 0.8 mbar - 3 mbar, the rate of decrease of the second pressure to the third pressure is 0.5 mbar / h - 10 mbar / h, and the second temperature is 2200°C - 2300°C.

[0027] The present invention also provides a silicon carbide seed crystal obtained by the above growth method.

[0028] In summary, the present invention provides a growth apparatus and application of a silicon carbide crystal. By improving the growth apparatus and growth method of the silicon carbide crystal, it is possible to regulate the radial and axial temperature gradients during crystal growth, reduce the thermal stress during crystal growth, and obtain high-quality large-diameter silicon carbide crystals. Moreover, the growth apparatus and application of the silicon carbide crystal provided by the present invention can improve the utilization rate of silicon carbide powder in the growth apparatus, avoid waste of resources, reduce the preparation cost, and are suitable for large-scale popularization and application.

[0029] Of course, it is not necessary to achieve all the above advantages simultaneously when implementing any aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0031] Figure 1 It is a structural diagram of the growth apparatus of the silicon carbide crystal provided by the present invention.

[0032] Reference Numerals:

[0033] 11, crucible; 111, bottom; 112, side; 12, cover body; 121, first part; 122, second part; 123, protrusion; 13, first heater; 14, second heater; 15, third heater; 16, silicon carbide powder; 17, raised part; 18, fourth heater; 19, diameter expansion ring; 20, first group of temperature measurement sensors; 201, first thermometer; 202, second thermometer; 203, third thermometer; 21, second group of temperature measurement sensors; 211, fourth thermometer; 212, fifth thermometer; 213, sixth thermometer; 22, temperature measurement through hole. Detailed implementation mode

[0034] The following specific examples are used to illustrate the implementation mode of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0035] It should be understood that the present invention can be implemented in different forms and should not be construed as being limited to the embodiments presented here. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

[0036] The technical solution of the present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the scope of protection of the present invention.

[0037] Please refer to Figure 1 As shown, the present invention provides a growth device for silicon carbide crystals, which at least includes a crucible 11, a cover 12, a first heater 13, a second heater 14, a third heater 15, silicon carbide powder 16, and a silicon carbide seed crystal (not shown in the figure), etc. Among them, the crucible 11 includes a bottom 111 and a side 112. The side 112 is disposed around one side of the bottom 111. The cover 12 is disposed on the side of the side 112 away from the bottom 111. The first heater 13 is disposed around the crucible 11 and is close to the side of the cover 12. The second heater 14 is disposed around the crucible 11 and is disposed on the side close to the bottom 111, and a preset distance is maintained between the second heater 14 and the first heater 13. The third heater 15 is disposed at intervals on the side of the cover 12 away from the crucible 11. The silicon carbide powder 16 is filled on the bottom 111 inside the crucible 11. The silicon carbide seed crystal is suspended on the side of the cover 12 close to the crucible 11. In the growth device provided by the present invention, through the first heater 13, the second heater 14, and the third heater 15, the radial and axial temperature gradients during crystal growth can be accurately regulated, the thermal stress during crystal growth can be reduced, and high-quality large-diameter silicon carbide crystals can be obtained.

[0038] Please refer to Figure 1As shown, in an embodiment of the present invention, the crucible 11 includes a bottom 111 and a side portion 112, and the side portion 112 is disposed around one side of the bottom 111. Among them, the present invention does not limit the specific shape of the crucible 11, and it can be selected according to actual needs. In this embodiment, taking the crucible 11 as a cylindrical shape as an example, the growth device will be described. Among them, the inner diameter of the crucible 11 is, for example, 400 mm - 1000 mm to prepare large-diameter silicon carbide crystals.

[0039] Please refer to Figure 1 As shown, in an embodiment of the present invention, the cover 12 is disposed on the side of the side portion 112 away from the bottom 111 to seal the crucible 11 and prevent the crystal growth process in the crucible 11 from being contaminated by impurities outside the crucible 11, thereby improving the quality of the silicon carbide crystal. Among them, the cover 12 includes, for example, a first part 121, a second part 122, a protrusion 123, etc. The first part 121 is disposed opposite to the bottom 111 on the side of the side portion 112 away from the bottom 111, and the diameter of the first part 121 is smaller than the inner diameter of the side portion 112. Further, one side of the first part 121 close to the bottom 111 is located inside the crucible 11, and the side of the first part 121 away from the bottom 111 is aligned with the side of the side portion 112 away from the bottom 111. The second part 122 extends from the first part 121 to the outside of the crucible 11, and the diameter of the second part 122 is equal to the diameter of the first part 121.

[0040] Please refer to Figure 1 As shown, in an embodiment of the present invention, the protrusion 123 extends from the side wall of the second part 122 to the side portion 112 along a direction parallel to the bottom 111. Among them, the protrusion 123, the second part 122, and the first part 121 are, for example, integrally provided. The combined diameter of the protrusion 123 and the second part 122 is equal to the outer diameter of the side portion 112, so that the protrusion 123 and the second part 122 can completely seal the crucible 11 and prevent impurities from contaminating the crystal growth process in the crucible 11.

[0041] Please refer to Figure 1As shown, in an embodiment of the present invention, silicon carbide powder 16 is filled on the bottom 111 inside the crucible 11, and the silicon carbide seed crystal is suspended on the side of the cover 12 close to the crucible 11. Specifically, the silicon carbide seed crystal is suspended on the side of the first part 121 away from the second part 122. The silicon carbide powder is sublimated and decomposed into gas by heating. The gas rises to the silicon carbide seed crystal and crystallizes on the surface of the silicon carbide seed crystal, thereby preparing a silicon carbide crystal. Among them, inside the crucible 11, the volume ratio of the target volume of the silicon carbide crystal to the volume of the silicon carbide powder 16 is, for example, 1:(4.5 - 6.5), so as to provide sufficient silicon carbide powder for obtaining a silicon carbide crystal with a target volume. The distance between the silicon carbide seed crystal and the silicon carbide powder 16 is, for example, 50 mm - 120 mm, which provides enough space for the crystallization growth of the gas on the silicon carbide seed crystal, can maintain an effective crystal growth gradient, control the crystal growth rate, and helps to improve the crystal quality.

[0042] Please refer to Figure 1 As shown, in an embodiment of the present invention, an expanding ring 19 is provided between the first part 121 and the side part 112. Specifically, the expanding ring 19 is arranged around the side wall of the first part 121 between the first part 121 and the side part 112 and extends in the direction of the bottom 111. The material of the expanding ring 19 includes, for example, graphite, etc. Further, in the direction of the cover 12 pointing to the bottom 111, the outer diameter of the expanding ring 19 remains unchanged while the inner diameter becomes larger, so as to limit the diameter of the silicon carbide crystal during the generation process, making the diameter of the silicon carbide crystal gradually increase in the direction of the cover 12 pointing to the bottom 111. Even when defects appear at the edge of the silicon carbide crystal, the edge of the silicon carbide crystal can be cut off to obtain a large-diameter silicon carbide crystal. Moreover, on the side of the expanding ring 19 away from the cover 12, the expanding ring 19 is in contact with the silicon carbide powder 16, so that the expanding ring 19 can completely cover the side part 112 inside the crucible 11 that is not covered by the silicon carbide powder 16, avoiding the atmosphere corrosion of the side part 112 during the crystal growth process and prolonging the service life of the crucible 11 and the growth device.

[0043] Please refer to Figure 1 As shown, in an embodiment of the present invention, the first heater 13 is arranged around the outside of the crucible 11 and is arranged close to the side of the cover 12. Specifically, in this embodiment, the side of the first heater 13 close to the bottom 111, that is, the lower surface, is higher than the plane where the surface of the silicon carbide powder 16 is located, and the side of the first heater 13 away from the bottom 111, that is, the upper surface, protrudes from the plane where the second part 122 is located.

[0044] Please refer to Figure 1As shown, in an embodiment of the present invention, the second heater 14 is disposed around the crucible 11 and is disposed close to the bottom 111 side. Specifically, in this embodiment, the side of the second heater 14 close to the cover body 12, that is, the upper surface, is lower than the plane where the surface of the silicon carbide powder 16 is located. The side of the second heater 14 close to the bottom 111, that is, the lower surface, protrudes from the plane where the bottom 111 is located, and a preset distance is maintained between the upper surface of the second heater 14 and the lower surface of the first heater 13. Among them, the present invention does not limit the length ratio of the second heater 14 and the first heater 13, and can be selected according to the needs of crystal growth. By providing the first heater 13 and the second heater 14 as the main heaters, heat is provided for the crucible 11 to ensure the smooth progress of the crystal growth process, and the axial temperature gradient in the crucible 11 can be controlled and adjusted to control the quality of the crystal. Moreover, by changing the preset distance, the axial temperature gradient in the crucible 11 can also be adjusted, thereby controlling factors such as the sublimation amount of the silicon carbide powder 16 and the crystal growth rate, and optimizing the crystal growth. Moreover, by disposing the plane where the surface of the silicon carbide powder 16 is located between the lower surface of the first heater 13 and the upper surface of the second heater 14, the charging amount of the silicon carbide powder 16 can be dynamically adjusted according to the change in the distance between the first heater 13 and the second heater 14, so as to adjust the growth distance between the silicon carbide powder 16 and the silicon carbide seed crystal and the temperature distribution in the growth powder, and then control the sublimation amount and growth rate of the powder.

[0045] Please refer to Figure 1 As shown, in an embodiment of the present invention, the third heater 15 is disposed at intervals on the side of the cover body 12 away from the crucible 11. Among them, the third heater 15 is, for example, a flat heater, etc. The present invention does not limit the shape and size of the third heater 15 and can be selected according to actual needs. In this embodiment, the third heater 15 is described by taking the shape of the third heater 15 as a cylinder as an example. Specifically, the center of the third heater 15 is, for example, on the axis of the crucible 11, and the diameter of the third heater 15 is, for example, smaller than the diameter of the first part 121. By providing the third heater 15, it is used to assist in heating the silicon carbide seed crystal, reduce the radial temperature gradient of the growth interface during the seed crystal growth process, and reduce the occurrence of cracks and cracking of the crystal caused by the residual thermal stress due to the excessive radial temperature gradient, thereby improving the quality of the crystal.

[0046] Please refer to Figure 1As shown, in an embodiment of the present invention, the growth device further includes a convex portion 17, which protrudes from the center of the bottom 111 towards the cover 12. The shape of the protrusion can be selected according to actual needs. In this embodiment, taking the shape of the protrusion as a hemispherical shape as an example, the growth device will be described. Due to the thermal field design, in the crucible 11, the temperature of the silicon carbide powder 16 near the side portion 112 is higher than the temperature of the silicon carbide powder 16 at the center of the crucible 11. The temperature of the silicon carbide powder 16 near the cover 12 side, that is, the temperature of the upper silicon carbide powder 16, is lower than the temperature of the silicon carbide powder 16 near the bottom 111 side, that is, the temperature of the lower silicon carbide powder 16. Therefore, in the central region of the crucible 11, the temperature of the upper silicon carbide powder 16 is relatively low and it is difficult to completely sublime, resulting in low utilization rate of the silicon carbide powder 16 and waste of some silicon carbide powder 16. By providing the convex portion 17, the filling amount of the silicon carbide powder 16 in the central region of the crucible 11 can be saved, thereby reducing the waste amount of the silicon carbide powder 16.

[0047] Please refer to Figure 1 As shown, in an embodiment of the present invention, a fourth heater 18 is provided in the convex portion 17. The fourth heater 18 is, for example, a spherical heater or the like. By providing the fourth heater 18, the silicon carbide powder 16 in the central region of the crucible 11 is assisted in heating, the temperature uniformity of the silicon carbide powder 16 is increased, which helps the sublimation of the upper silicon carbide powder 16 in the crucible 11 and improves the utilization rate of the silicon carbide powder 16.

[0048] Please refer to Figure 1As shown, in an embodiment of the present invention, a temperature measuring sensor is further provided outside the crucible 11 to monitor the axial temperature gradient and the radial temperature gradient inside the crucible 11, so that according to the monitoring results, the heating power of the four heaters can be changed to adjust the temperature distribution inside the crucible 11. Among them, the temperature measuring sensor is, for example, at least two groups, and each group of temperature measuring sensors includes, for example, a plurality of thermometers arranged in parallel. In this embodiment, the temperature measuring sensor is, for example, two groups, and the two groups of temperature measuring sensors are, for example, the first group of temperature measuring sensors 20 and the second group of temperature measuring sensors 21, etc. The first group of temperature measuring sensors 20 is, for example, arranged on the side of the cover 12 away from the crucible 11, and the second group of temperature measuring sensors 21 is symmetrically arranged with the first group of temperature measuring sensors 20 on the side of the bottom 111 away from the side 112. Among them, each group of temperature measuring sensors includes, for example, three thermometers arranged in parallel. Specifically, in the first group of temperature measuring sensors 20, the three thermometers are, for example, the first thermometer 201, the second thermometer 202, and the third thermometer 203, etc. The first thermometer 201 is arranged on the side of the third heater 15 away from the cover 12 and extends towards the center of the third heater 15. The second thermometer 202 and the third thermometer 203 are symmetrically arranged on both sides of the first thermometer 201. In the second group of temperature measuring sensors 21, the three thermometers are, for example, the fourth thermometer 211, the fifth thermometer 212, and the sixth thermometer 213, etc. The fourth thermometer 211 and the first thermometer 201, the fifth thermometer 212 and the second thermometer 202, and the sixth thermometer 213 and the third thermometer 203 are symmetrically arranged on both sides of the crucible 11 respectively, and the vertical distance between the end of each thermometer close to the crucible 11 and the crucible 11 is equal. By observing the temperature changes of the three thermometers in each group of temperature measuring sensors, the radial temperature gradient inside the crucible 11 can be monitored in real time. By observing the temperature changes of the two symmetrically arranged thermometers in different groups of temperature measuring sensors, the axial temperature gradient inside the crucible 11 can be monitored in real time, so that according to the monitoring results, the temperature gradient can be precisely adjusted, the growth of the crystal can be optimized, and the quality of the crystal can be improved.

[0049] Please refer to Figure 1 As shown, in an embodiment of the present invention, a temperature measuring through hole 22 is further provided outside each thermometer to accommodate the thermometer. Specifically, the thermometer extends from inside the temperature measuring through hole 22 to outside the temperature measuring through hole 22 and protrudes from the temperature measuring through hole 22, so that the operator can determine the temperature measurement result of each thermometer according to the thermometer exposed outside the temperature measuring through hole 22, improving the convenience of temperature monitoring.

[0050] Please refer to Figure 1 As shown, based on the above-mentioned silicon carbide crystal growth device, the present invention provides a method for growing a silicon carbide crystal, which at least includes steps S11 - S16.

[0051] Step S11: Provide a silicon carbide crystal growth device.

[0052] Step S12: Place the growth device in the cavity. After the first evacuation of the cavity, heat the cavity to the first temperature.

[0053] Step S13: After introducing a protective gas into the cavity to the first pressure, evacuate the cavity for the second time, and repeat the steps of introducing the protective gas and the second evacuation for a preset number of times.

[0054] Step S14: After introducing nitrogen into the cavity to the second pressure, reduce the pressure in the cavity to the third pressure and maintain it for the first period of time.

[0055] Step S15: Raise the temperature of the cavity from the first temperature to the second temperature and maintain it for the second period of time.

[0056] Step S16: After introducing a protective gas into the cavity to the fourth pressure, cool the cavity, take out the growth device, and obtain a silicon carbide crystal.

[0057] Please refer to Figure 1 As shown, in an embodiment of the present invention, in step S11, the growth device is the same as the growth device of the above silicon carbide crystal, and no further elaboration will be made here.

[0058] Please refer to Figure 1 As shown, in an embodiment of the present invention, in step S12, place the growth device in the cavity. After the first evacuation of the cavity, start the first heater 13, the second heater 14, the third heater 15, and the fourth heater 18, and heat the cavity to the first temperature. Among them, the cavity is, for example, the heating cavity of a growth furnace, etc. The pressure in the cavity after the first evacuation is, for example, 0 Pa - 1 Pa, the first temperature is, for example, 1700 °C - 1900 °C, and the heating time is, for example, 6 h - 12 h. Through the first evacuation treatment, air impurities in the cavity can be removed to avoid the influence of air impurities on the subsequent crystal growth.

[0059] Please refer to Figure 1 As shown, in an embodiment of the present invention, in step S13, the protective gas includes, for example, at least one of argon and helium, etc. The first pressure is, for example, 500 mbar - 700 mbar, the pressure in the cavity after the second evacuation is, for example, 0 Pa - 1 Pa, and the preset number of times is, for example, at least two times. By repeating the steps of introducing the protective gas into the cavity and the second evacuation, the removal effect of air impurities in the cavity can be enhanced, avoiding the incorporation of air impurities into the crystal growth and resulting in defects in the crystal, thereby improving the quality of the crystal.

[0060] Please refer to Figure 1As shown, in an embodiment of the present invention, after removing air impurities in the cavity, in step S14, nitrogen is introduced into the cavity to a second pressure, and then the cavity is communicated with the external atmosphere to release the nitrogen in the cavity into the external atmosphere. The pressure in the cavity naturally drops to a third pressure, and the cavity is maintained at the first temperature and the third pressure for a first period of time. Among them, the flow rate of nitrogen introduced is, for example, 6 mL / min - 50 mL / min, the second pressure is, for example, 400 mbar - 800 mbar, the third pressure is, for example, 0.8 mbar - 3 mbar, the speed of the second pressure dropping to the third pressure is, for example, 0.5 mbar / h - 10 mbar / h, and the first period of time is, for example, 2 h - 5 h. In step S14, before crystal growth, nitrogen is introduced into the cavity in advance to a higher pressure, and the pressure in the cavity is reduced to the pressure required during crystal growth by releasing nitrogen, which can make nitrogen evenly distributed in the cavity, fundamentally reduce the risk of polytype growth from the nucleation stage, effectively inhibit the generation of polytype silicon carbide crystals such as 3C and 6H, and is conducive to the growth of 4H silicon carbide crystals.

[0061] Please refer to Figure 1 As shown, in an embodiment of the present invention, after the cavity is maintained at the third pressure, in step S15, the first heater 13, the second heater 14, the third heater 15, and the fourth heater 18 are adjusted to heat the cavity, so that the cavity is heated from the first temperature to the second temperature and maintained for a second period of time. At the second temperature, the crystal growth process is carried out in the crucible 11. Among them, the second temperature is, for example, 2200 °C - 2300 °C, the heating rate is, for example, 4 °C / h - 12 °C / h, and the second period of time is, for example, 50 - 150 h.

[0062] Please refer to Figure 1 As shown, in an embodiment of the present invention, after crystal growth is completed, in step S16, a protective gas is introduced into the cavity to a fourth pressure, then the first heater 13, the second heater 14, the third heater 15, and the fourth heater 18 are turned off to stop heating the cavity, and then the protective gas is continuously introduced. After the cavity is cooled to room temperature, the growth device is taken out to obtain silicon carbide crystals. Among them, the fourth pressure is, for example, 500 mbar - 800 mbar.

[0063] Please refer to Figure 1As shown, in an embodiment of the present invention, during the growth of the crystal, increasing the temperature is conducive to the stable sublimation of the silicon carbide powder 16 in the crucible 11, and reducing the pressure is conducive to the growth and crystallization in the crucible 11. However, when the temperature and pressure change simultaneously, it will cause a large disturbance to the crystal growth environment in the crucible 11, which is not conducive to obtaining high-quality crystals. Therefore, in the crystal growth method provided by the present invention, in step S14, the temperature of the cavity is not changed, only the pressure of the cavity is reduced, and the pressure in the cavity is set at the third pressure. In step S15, the pressure of the cavity is not changed, only the temperature of the cavity is changed, and the temperature in the cavity is increased to the second temperature. By adopting the strategy of staggered changes in pressure reduction and temperature increase, it is possible to avoid the drastic disturbance of the crystal growth environment in the crucible 11 caused by the simultaneous change of pressure and temperature, reduce the probability of generating other polytype silicon carbide crystals, and ensure the dynamic stability of the crystal growth rate in the crucible 11, maintaining the stable progress of the crystal growth process.

[0064] Please refer to Figure 1 As shown, based on the above-mentioned silicon carbide crystal growth method, the present invention also provides a silicon carbide crystal. The silicon carbide crystal includes a first end and a second end arranged oppositely. In the direction from the first end to the second end, the size of the silicon carbide crystal increases, and at the growth interface, that is, at the boundary where the crystal reaches dynamic equilibrium with the sublimated gas phase of the silicon carbide powder, the interface is, for example, a smooth arc-shaped convex interface that gradually transitions from the center to the edge. Among them, the effective thickness, that is, the minimum thickness, of the silicon carbide crystal is, for example, 17 mm - 20 mm, there is no polycrystalline growth at the edge position, and there are no macroscopic microcracks extending inward at the edge. The effective diameter of the crystal is, for example, 300 mm - 350 mm, leaving enough machining allowance for subsequent processing of the silicon carbide crystal to prepare the silicon carbide substrate and improving the yield of the silicon carbide substrate. Among them, the effective diameter is, for example, the diameter of the available part of the silicon carbide crystal that meets the quality requirements, and the quality requirements include, for example, properties such as low defect density, uniform polytype, and controllable resistivity.

[0065] The technical solution of the present invention will be described in detail below through a specific embodiment and a comparative example. Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the examples can all be purchased commercially.

[0066] Example 1

[0067] Provide the silicon carbide crystal growth device provided in the present invention as Figure 1 shown, and control the density of the silicon carbide powder through an oscillation platform to maintain a uniform distribution of the pores in the silicon carbide powder and keep the surface of the silicon carbide powder flat. Among them, the inner diameter of the crucible is 440 mm, the distance between the silicon carbide powder and the seed crystal is 80 mm, and the volume ratio of the target volume of the silicon carbide crystal to the volume of the silicon carbide powder is 1:5.

[0068] Place the growth device in the heating chamber of the growth furnace, evacuate the heating chamber of the growth furnace and maintain it at 0 Pa, start the first heater, the second heater, the third heater and the fourth heater, and raise the temperature of the heating chamber to 1800 °C in 8 h. After the temperature rises to 1800 °C, introduce argon into the heating chamber to increase the pressure of the heating chamber of the growth furnace to 600 mbar, then evacuate the heating chamber to 0 Pa, and repeat the operations of introducing argon and evacuating 3 times.

[0069] Introduce nitrogen into the heating chamber to 600 mbar, then connect the chamber to the external atmosphere to release the nitrogen in the chamber to the external atmosphere, and the pressure in the chamber naturally drops to 3 mbar, and maintain the chamber at 3 mbar and 1800 °C for 3 h. Adjust the first heater, the second heater, the third heater and the fourth heater to raise the temperature of the heating chamber to 2200 °C and stably grow crystals for 150 h.

[0070] After the crystal growth is completed, introduce argon into the heating chamber to 600 mbar, then turn off the first heater, the second heater, the third heater and the fourth heater to stop heating, and then continue to introduce argon. After cooling the heating chamber to room temperature, take out the growth device to obtain a silicon carbide crystal. Among them, the final growth interface of the crystal is an arc-shaped micro-convex interface that smoothly transitions from the center to the edge, the effective thickness of the crystal is 17.54 mm, there is no polycrystalline growth at the edge position, and there is no macroscopic micro-crack extending inwards at the edge, and the effective diameter of the crystal is 306.38 mm.

[0071] Comparative Example 1

[0072] The difference between this comparative example and Example 1 is that: the growth device does not have the third heater and the fourth heater. Moreover, in the silicon carbide crystal obtained in this comparative example, the final growth interface of the crystal presents a morphological feature of convexity at the center and the edge and concavity in the transition region between the center and the edge, resulting in an effective thickness of the crystal of 10.23 mm, and there is more polycrystalline growth at the convex position at the edge and gradually extends towards the center, resulting in an effective diameter of the crystal of only 275 mm.

[0073] Comparing the crystal parameters of Example 1 and Comparative Example 1, it can be seen that the silicon carbide crystal obtained by the growth device and growth method provided by the present invention has a larger effective thickness and effective diameter, and there is no polycrystalline morphology in the crystal. Therefore, the growth device and growth method provided by the present invention can increase the effective thickness and effective diameter of the silicon carbide crystal, contribute to obtaining a large-diameter silicon carbide crystal, thereby providing sufficient processing margin for processing the silicon carbide crystal to prepare a silicon carbide substrate and improving the yield of the silicon carbide substrate. Moreover, it can avoid the appearance of polycrystals in the silicon carbide crystal and improve the quality of the silicon carbide crystal.

[0074] In summary, the present invention provides a growth apparatus for silicon carbide crystals and its application. By improving the growth apparatus for silicon carbide crystals, it is possible to regulate the radial and axial temperature gradients during crystal growth, reduce the thermal stress during crystal growth, and obtain high-quality large-diameter silicon carbide crystals. Moreover, the growth apparatus for silicon carbide crystals and its application provided by the present invention can improve the utilization rate of silicon carbide powder in the growth apparatus, avoid waste of resources, reduce the preparation cost, and are suitable for large-scale popularization and application.

[0075] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A growth apparatus for silicon carbide crystals, characterized in that, Comprising at least: A crucible, including a side portion and a bottom portion, the side portion being disposed around one side of the bottom portion; A cover body, disposed on the side of the side portion away from the bottom portion; A first heater, disposed around the crucible and close to the side of the cover body; A second heater, disposed around the crucible and close to the side of the bottom portion, a preset distance being maintained between the second heater and the first heater; A third heater, spacedly disposed on the side of the cover body away from the crucible; Silicon carbide powder, filled on the side of the bottom portion close to the side portion; And A silicon carbide seed crystal, suspended on the side of the cover body close to the crucible.

2. The growth device according to claim 1, characterized in that, The bottom portion further includes a convex portion, the convex portion protruding from the center of the bottom portion towards the side of the cover body.

3. The growth device according to claim 2, wherein, The growth device further includes a fourth heater, the fourth heater being disposed within the convex portion.

4. The growth device according to claim 1, characterized in that, The side of the first heater close to the bottom portion is higher than the plane where the surface of the silicon carbide powder is located, and the side of the second heater close to the cover body is lower than the plane where the surface of the silicon carbide powder is located.

5. The growth device according to claim 1, wherein The growth device further includes an expanding ring, the expanding ring being disposed around between the cover body and the side portion and extending towards the direction of the bottom portion.

6. The growth device according to claim 5, characterized in that, In the direction from the cover body towards the bottom portion, the inner diameter of the expanding ring becomes larger.

7. The growth device according to claim 5, characterized in that, The side of the expanding ring away from the cover body is in contact with the silicon carbide powder.

8. A method for growing a silicon carbide crystal, characterized in that, At least including the following steps: Providing the growth device for silicon carbide crystals according to any one of claims 1-7; Placing the growth device in a cavity, and after performing a first vacuum pumping on the cavity, heating the cavity to a first temperature; After introducing a protective gas into the cavity to a first pressure, performing a second vacuum pumping on the cavity, and repeating the steps of introducing the protective gas and the second vacuum pumping for a preset number of times; After introducing nitrogen into the cavity to a second pressure, reducing the pressure in the cavity to a third pressure and maintaining for a first time; Raising the temperature of the cavity from the first temperature to a second temperature and maintaining for a second time; And After introducing the protective gas into the cavity to a fourth pressure, cooling the cavity, taking out the growth device, and obtaining silicon carbide crystals.

9. The growth method according to claim 8, characterized in that, The first temperature is 1700°C - 1900°C, the protective gas includes at least one of argon and helium, the first pressure is 500 mbar - 700 mbar, the flow rate of nitrogen introduced is 6 mL / min - 50 mL / min, the second pressure is 400 mbar - 800 mbar, the third pressure is 0.8 mbar - 3 mbar, the speed of reducing the second pressure to the third pressure is 0.5 mbar / h - 10 mbar / h, and the second temperature is 2200°C - 2300°C.

10. A silicon carbide crystal, characterized in that, Obtained by using the growth method according to any one of claims 8-9.

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