Silicon carbide crystal, seed and substrate

Abstract

The application discloses a silicon carbide crystal, and belongs to the field of semiconductor materials. The silicon carbide crystal has a first main surface and a second main surface opposite to the first main surface, the first main surface and / or the second main surface has a nucleation morphology, the nucleation morphology has a nucleation center point, a central axis of the silicon carbide crystal penetrates the first main surface and the second main surface, and an intersection of the central axis and the first main surface and / or the second main surface is a crystal center point; a distance from the nucleation center point to the crystal center point is less than 1 / 4 of a diameter of the silicon carbide crystal. The distance between the nucleation center point and the crystal center point of the silicon carbide crystal is less than 1 / 4 of the diameter of the silicon carbide crystal, the distance between the two center points is small, the nucleation quality is high, and the defect density is low.

Description

TECHNICAL FIELD

[0001] The application relates to a silicon carbide crystal, a seed crystal and a substrate, and belongs to the field of semiconductor materials. BACKGROUND

[0002] Silicon carbide is a typical wide-bandgap semiconductor material and is one of the third-generation semiconductor material representatives after silicon and gallium arsenide. Silicon carbide material has excellent characteristics such as high thermal conductivity, high breakdown field strength and high saturation electron mobility, and has become one of the popular materials for preparing high-temperature, high-frequency, high-power and radiation-resistant devices.

[0003] At present, the methods for growing silicon carbide mainly include physical vapor transport (PVT), liquid phase epitaxy (LPE) and chemical vapor deposition (CVD), wherein the PVT method is the most mature method and is the only method that can meet the demand for commercial silicon carbide substrates. The growth furnace for growing silicon carbide crystals by the PVT method generally adopts an inductive heating mode, that is, a medium-frequency alternating current is passed through an induction coil, the silicon carbide powder in the growth chamber is heated through the induction heating of the crucible, the powder is decomposed, crystallization and growth are performed at the seed crystal with a lower temperature, and thus the growth of the crystal is realized. The PVT method for growing silicon carbide crystals often needs to construct a very uniform temperature field at the seed crystal, and uniform upward transmission and orderly arrangement of the silicon carbide atmosphere are realized through stable radial and axial temperature gradients, so as to obtain high-quality silicon carbide crystals with low defect density. For defects such as microtubes, impurities, small-angle grain boundaries and long-range lattice distortion, researchers have done a lot of work on the seed crystal angle. In order to obtain a high enough growth step density, the seed crystal for growing silicon carbide crystals is usually grown with a seed crystal with a (0001) surface (i.e. a Si surface) deviated from the <11-20> direction by a certain angle, so that the growth information can be effectively transmitted and the defect density of the crystal can be greatly reduced. The silicon carbide crystal continuously transmits growth step information in a spiral growth manner through the nucleation center during the crystal growth, and finally forms a facet structure, and the area outside the facet grows in a step flow manner according to the growth step information transmitted by the nucleation center.

[0004] Nucleation is a very important part of silicon carbide crystal growth, and the quality of nucleation will directly determine the crystalline quality of the later silicon carbide crystal. Although the seed crystal with (0001) surface (i.e. Si surface) deviated from the <11-20> direction by a certain angle can improve the crystal quality, the existence of the angle will also make the nucleation center deviate from the <11-20> direction, resulting in that the nucleation center (i.e. the center point of the facet) is not coincident with the crystal center or the coincidence rate is low. The crystal center is often the center of the temperature field, i.e. the lowest point of the radial temperature, and the growth speed is the fastest in the radial direction. If the nucleation center is not coincident with the center of the temperature field, the growth step information of the nucleation center cannot be effectively transmitted to the crystal center and the opposite area of the nucleation center, and defects such as secondary microtubules, polytypes, stacking faults and dislocations will be generated, which will restrict the further improvement of the crystal quality. SUMMARY

[0005] In order to solve the above problems, a silicon carbide crystal is provided, and the distance between the nucleation center point and the crystal center point of the silicon carbide crystal is less than 1 / 4 of the diameter of the silicon carbide crystal. The distance between the two center points is small, the nucleation quality is high, and the defect density is low.

[0006] According to one aspect of the present application, a silicon carbide crystal is provided, which has a first main surface and a second main surface opposite to the first main surface, the first main surface and / or the second main surface has a nucleation morphology, the nucleation morphology has a nucleation center point, a central axis of the silicon carbide crystal penetrates the first main surface and the second main surface, and the intersection of the central axis and the first main surface and / or the second main surface is a crystal center point.

[0007] In the first main surface and / or the second main surface, the distance between the nucleation center point and the crystal center point is less than 1 / 4 of the diameter of the silicon carbide crystal.

[0008] Preferably, the distance between the nucleation center point and the crystal center point is less than 1 / 5 of the diameter of the silicon carbide crystal.

[0009] Preferably, the distance between the nucleation center point and the crystal center point is less than 1 / 10 of the diameter of the silicon carbide crystal.

[0010] Preferably, the distance between the nucleation center point and the crystal center point is less than 1 / 12 of the diameter of the silicon carbide crystal.

[0011] More preferably, the nucleation center point is coincident with the crystal center point.

[0012] Optionally, the distance between the nucleation center point and the crystal center point is 0-25 mm.

[0013] Preferably, the distance between the nucleation center point and the crystal center point is 0-20 mm.

[0014] More preferably, the distance between the nucleation center point and the crystal center point is 0-15mm;

[0015] Preferably, the distance between the nucleation center point and the crystal center point is 0-10mm;

[0016] Preferably, the distance between the nucleation center point and the crystal center point is 0-6mm;

[0017] Preferably, the distance between the nucleation center point and the crystal center point is 0-3mm;

[0018] More preferably, the distance between the nucleation center point and the crystal center point is 0.

[0019] Optionally, the first main surface is {0001} surface.

[0020] Optionally, the nucleation center point is at the center of the {0001} surface and deviates towards <11-20> direction.

[0021] Optionally, the nucleation morphology is approximately circular, the ratio of the diameter of the nucleation morphology to the diameter of the silicon carbide crystal is 1 / 5-2 / 3, and the ratio of the area of the nucleation morphology to the area of the first main surface or the second main surface is 1 / 25-4 / 9.

[0022] Preferably, the ratio of the diameter of the nucleation morphology to the diameter of the silicon carbide crystal is 1 / 4-1 / 2, and the ratio of the area of the nucleation morphology to the area of the first main surface or the second main surface is 1 / 16-1 / 4.

[0023] Optionally, the diameter of the nucleation morphology is 40mm-220mm, and the diameter of the silicon carbide crystal is greater than or equal to 90mm.

[0024] Preferably, the diameter of the nucleation morphology is 50mm-200mm, and the diameter of the silicon carbide crystal is greater than or equal to 100mm.

[0025] Optionally, the TSD of the crystal region surrounded by the nucleation morphology is less than 160 / cm 2 , and the TED is less than 1600 / cm 2 ; the TSD of the crystal region outside the nucleation morphology is less than 120 / cm 2 , and the TED is less than 1100 / cm 2 ;

[0026] Preferably, the TSD of the crystal region surrounded by the nucleation morphology is less than 150 / cm 2 , and the TED is less than 1500 / cm 2TSD of the crystal region surrounded by the nucleation morphology is less than 100 / cm 2 TED is less than 1000 / cm 2

[0027] More preferably, TSD of the crystal region surrounded by the nucleation morphology is less than 120 / cm 2 TED is less than 1300 / cm 2 TSD of the crystal region surrounded by the nucleation morphology is less than 80 / cm 2 TED is less than 700 / cm 2 .

[0028] Optionally, the surface stress of the crystal is less than 18Mpa in absolute value, the difference value within the nucleation morphology is less than 25Mpa, and the crystallization quality of the crystal is less than 28arcs;

[0029] Preferably, the surface stress of the crystal is less than 15Mpa in absolute value, the difference value within the nucleation morphology is less than 20Mpa, and the crystallization quality of the crystal is less than 25arcs.

[0030] According to another aspect of the present application, a silicon carbide seed crystal is provided, which is cut, ground and polished from any of the silicon carbide crystals described above.

[0031] According to another aspect of the present application, a silicon carbide substrate is provided, which is cut, ground and polished from any of the silicon carbide crystals described above.

[0032] In the present application, the crystal center point is defined as the intersection of the axis and the first main surface ({0001} surface) and the second main surface of the silicon carbide crystal as the crystal center point;

[0033] In the present application, the crystal center refers to the extension of the crystal center point of the first main surface to the crystal center point of the second main surface, which is also the center of the temperature field, i.e. the lowest point of the radial temperature;

[0034] In the present application, the nucleation center refers to the extension of the nucleation center point of the nucleation morphology of the first main surface to the nucleation center point of the nucleation morphology of the second main surface.

[0035] The positional relationship between the nucleation center point and the crystal center point can effectively reflect the positional relationship between the crystal center and the nucleation center.

[0036] The beneficial effects of the present application include but are not limited to:

[0037] ​1. The SiC crystal according to the present application, the distance between the nucleation center point and the crystal center point is less than 1 / 4 of the diameter of the SiC crystal, the smaller the distance between the two points, the higher the coincidence or complete coincidence between the nucleation center and the crystal center, the higher the nucleation quality and the lower the defect density.

[0038] 2. The SiC seed crystal according to the present application, which is made of the SiC crystal according to the present application, the distance between the nucleation center point and the crystal center point is small or coincides, which can effectively transfer the growth step information of the nucleation center to the crystal center and the opposite region symmetrical to the crystal center, and further improve the nucleation quality of the SiC crystal generated by the seed crystal.

[0039] 3. The SiC substrate according to the present application, which is made of the SiC crystal according to the present application, the distance between the crystal center point and the nucleation center point is small, the nucleation quality is high, and the defect density is low.

[0040] 4. The SiC crystal, seed crystal and substrate according to the present application, the Bow is less than 5 um, the Warp is less than 10 um, the TTV is less than 3 um, and the LTV is less than 1 um. BRIEF DESCRIPTION OF DRAWINGS

[0041] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0042] Figure 1 It is an axial sectional view of a SiC crystal growth device related to the embodiments of the present application.

[0043] Figure 2 It is a top view of a SiC crystal growth device related to the embodiments of the present application.

[0044] Figure 3 It is a radial sectional view of an upper chamber of a SiC crystal growth device related to the embodiments of the present application.

[0045] Figure 4 It is a SiC crystal in which the nucleation center point and the crystal center point do not coincide, which is related in the background art.

[0046] Figure 5 It is a SiC crystal in which the nucleation center point and the crystal center point coincide, which is related in the embodiments of the present application.

[0047] 1. Crucible body, 2. Growth chamber, 21. Upper chamber, 22. Lower chamber, 3. Seed crystal placement part (seed crystal), 4. Porous graphite partition plate, 5. SiC powder, 6. Porous graphite platform, 7. Graphite connecting cylinder, 8. Cover body, 9. Chamber,

[0048] 10, silicon carbide crystal, 101, first main surface, 102, second main surface, 103, crystal center point, 104, nucleation morphology, 105, nucleation center point.

[0049] A. A vent (1# vent), A'. A' vent (5# vent), 2-4# vent, 6-8# vent. DETAILED DESCRIPTION

[0050] The present application will be described in detail below with reference to examples, but the present application is not limited to these examples.

[0051] The raw materials in the examples of the present application are all purchased through commercial channels unless otherwise specified.

[0052] The present embodiment provides a silicon carbide crystal growth device for producing a silicon carbide crystal with a nucleation center point 105 close to or coinciding with a crystal center point 103, referring to Figures 1-3 、 Figure 5 The silicon carbide crystal growth device includes a crucible body 1, a plurality of vents are provided on the side wall of a growth chamber 2 in the crucible body 1, the vents are provided at the same height of the side wall of the growth chamber 2, the vents include a first pair of vents, the first pair of vents includes an A vent and an A' vent, the A vent and the A' vent are symmetrically arranged about the central axis of the growth chamber 2, a second pair of vents is symmetrically arranged on both sides of the straight line on which the A vent and the A' vent are located, so that different concentration gradients of the atmosphere are introduced into the growth chamber 2 along the side wall of the growth chamber 2 from the A vent to the A' vent. The nucleation center of the existing silicon carbide crystal 10 is generally offset from the crystal center of the silicon carbide crystal 10 by a certain distance in the <11-20> direction during the crystal growth process, such as at 1 / 4 of the diameter of the silicon carbide crystal 10, the growth step information emitted from the nucleation center will have a large difference in the transmission growth distance in the radial direction of the silicon carbide crystal 10, the transmission distance in the <11-20> direction is the shortest, the transmission distance in the <-1-120> direction is the longest, and the transmission process in the <-1-120> direction will pass through the crystal center, which is the center of the temperature field and has the lowest temperature, and the growth speed is the fastest. The separation of the nucleation center and the crystal center will inevitably disturb the crystal growth process of the silicon carbide crystal, the step information of the nucleation center cannot effectively pass through the crystal center, resulting in loss, mismatch or even mismatch of the growth information, which has great hidden dangers for improving the quality of the crystal. Therefore, a plurality of vents are provided at the same height of the growth chamber to build a gradient change of gradually decreasing Si-containing atmosphere and gradually increasing C-containing atmosphere from the A vent to the A' vent, so as to guide the nucleation center to move towards the crystal center (i.e. the center of the temperature field).

[0053] The second pair of ventilation ports is an odd number of pairs and is evenly distributed on both sides of the straight line where the first pair of ventilation ports is located; the number of the second pair of ventilation ports can be one pair, three pairs, five pairs, or seven pairs, and the number of the second pair of ventilation ports can be set according to actual conditions; in a specific embodiment, the number of the second pair of ventilation ports is three pairs, and reference is made to Figure 2 and Figure 3 The A ventilation ports are sequentially marked as 1#-8# ventilation ports, and the 1#-8# ventilation ports are evenly distributed on the peripheral side wall of the growth cavity, so that the A ventilation port is the 1# ventilation port, the A' ventilation port is the 5# ventilation port, each ventilation port is connected to a different gas source through a graphite conduit, the silicon-containing atmosphere is a silane gas, the C-containing atmosphere is an alkane gas, the alkane gas includes methane and / or ethane, the silane gas includes monosilane and / or disilane, the 3# ventilation port and the 7# ventilation port are connected to the alkane gas and the silane gas at a volume ratio of 1:1, the 2# and 8# ventilation ports are connected to the alkane gas and the silane gas at a volume ratio of 1:3, the 4# and 6# ventilation ports are connected to the alkane gas and the silane gas at a volume ratio of 3:1, the 1# ventilation port is connected to the silane gas, and the 5# ventilation port is connected to the alkane gas, thereby constructing a gradient change in which the Si-containing gas gradually decreases and the C-containing gas gradually increases from the A ventilation port to the A' ventilation port.

[0054] In an embodiment, reference is made to Figure 1 The crucible body 1 is provided with a porous partition piece, and the porous partition piece divides the growth chamber into an upper chamber 21 and a lower chamber 22. The ventilation ports are arranged on the side wall of the upper chamber 21, and the porous partition piece can transport the atmosphere in the upper chamber 21 to the lower chamber 22. The porous partition piece divides the growth chamber 2 into the upper chamber 21 and the lower chamber 22, the ventilation ports are arranged on the side wall of the upper chamber 21, the lower chamber 22 can be provided with different temperature change gradients, and the air permeability of the porous partition piece can ensure that the atmosphere introduced into the upper chamber 21 can be effectively and quickly discharged, maintain the dynamic balance of the pressure and various gas components in the upper chamber, build a stable temperature field and flow field structure for silicon carbide crystal growth, reduce or eliminate the defects (such as stress, TED, TSD, and surface type) of silicon carbide crystals caused by air flow disturbance, and improve the quality of silicon carbide crystals. In addition, the lower chamber 22 can also be used as a raw material recrystallization recovery area, and a certain temperature gradient difference is constructed, so that the unreacted atmosphere in the upper chamber 21 gradually recrystallizes to obtain high-purity silicon carbide powder after entering the lower chamber 22, and the raw material is recycled.

[0055] As an embodiment, the porous partition is a porous graphite partition plate 4, and the density of the porous graphite partition plate 4 is less than the density of the crucible body. The porous partition is the porous graphite partition plate 4, which can effectively and timely exhaust the gas in the upper chamber 21, and the pressure difference between the upper chamber 21 and the lower chamber 22 can form a downward airflow to effectively inhibit the upward movement of C particles into the silicon carbide crystal, thereby reducing the number of inclusions in the silicon carbide crystal. The crucible body is generally a graphite crucible body, and the density of the porous graphite partition plate 4 is less than the density of the graphite crucible body, so that the unreacted gas in the upper chamber 21 gradually recrystallizes to obtain high-purity silicon carbide powder after entering the lower chamber 22, thereby realizing the reuse of raw materials.

[0056] In an embodiment, the density of the porous graphite partition plate 4 is 0.2-1.5 g / cm 3 , and the density of the graphite crucible body is generally 1.3-2.5 g / cm 3 ; further, the density of the porous graphite partition plate 4 is 0.3-1.3 g / cm 3 .

[0057] The inside of the top cover 8 of the upper chamber 21 is provided with a seed crystal placement part 3, and the A' air port is opposite to the <11-20> direction of the seed crystal placement part 3 (also the <11-20> direction of the seed crystal). The air port is arranged on the side wall of the upper chamber 21 near the seed crystal placement part 3. Since the nucleation center of the silicon carbide crystal 10 is generally at a certain distance from the crystal center of the silicon carbide crystal 10 in the <11-20> direction, the A' air port is opposite to the <11-20> direction of the seed crystal placement part 3, the concentration of the Si-containing atmosphere in the A' air port is the lowest, and the concentration of the C-containing atmosphere in the A' air port is the highest. The concentration of the Si-containing atmosphere in the A air port is the highest, and the concentration of the C-containing atmosphere in the A air port is the lowest, which is more conducive to guiding the nucleation center to move to the crystal center (i.e., the center of the temperature field).

[0058] The silicon carbide crystal growth device further comprises a porous graphite platform 6, and the lower chamber 22 is surrounded by the porous graphite platform 6, the side wall of the crucible body, and the porous partition. The density of the porous graphite platform 6 is less than the density of the crucible body 1. The density of the porous graphite platform 6 is less than the density of the crucible body 1, which can avoid the atmosphere entering the lower chamber 22 from entering the side wall of the graphite crucible body to precipitate silicon carbide grains and erode the heat preservation structure of the crucible body 1, thereby prolonging the service life of the heat preservation structure and achieving the effect of reducing cost and increasing efficiency. Further, the porous graphite platform 6 is in the shape of a hollow boss, the top of the porous graphite platform 6 extends to the porous partition, and the porous graphite platform 6 is selected from one of a circular platform, a circular cone, and a circular cylinder, but is not limited to these shapes. The hollow part of the porous graphite platform 6 is provided with a graphite connecting cylinder 7, one end of the graphite connecting cylinder 7 extends away from the lower chamber 22. The graphite connecting cylinder 7 is connected to a gas treatment device through a graphite guide pipe, the gas treatment device absorbs excess atmosphere, and avoids the atmosphere from eroding the heat preservation structure of the crucible body 1.

[0059] The density of the graphite connecting cylinder 7 is less than the density of the crucible body 1; the density of the graphite connecting cylinder 7 is not greater than the density of the porous graphite platform 6. The density of the graphite connecting cylinder 7 is less than the density of the crucible body 1 and not greater than the density of the porous graphite platform 6, which can avoid the atmosphere entering the lower chamber 22 from eroding the heat preservation of the crucible body 1 due to the precipitation of silicon carbide grains from the sidewall of the graphite crucible body, thereby prolonging the service life of the heat preservation.

[0060] In an embodiment, the diameter of the upper chamber 21 is 100-300 mm, the height is 150-500 mm, the pore size of the vent is 5-20 mm, the thickness of the sidewall of the crucible body is 10-30 mm, the height of the lower chamber 22 is 150-500 mm, the distance from the top of the porous graphite platform 6 to the bottom of the porous partition is 30-100 mm, and the temperature variation from top to bottom of the lower chamber 22 is 0.1-10 ℃ / mm, so as to ensure the full recrystallization of the silicon carbide powder.

[0061] In the present embodiment, a silicon carbide crystal growth method is also provided, which uses the growth device described above and includes the following steps:

[0062] 1. Assembly stage

[0063] (1) Assemble the crucible body 1, seed crystal, SiC powder 5, porous graphite partition plate 4, porous graphite platform 6, and graphite connecting cylinder 7 according to the Figure 1 arrangement, wherein the <11-20> direction of the seed crystal unit is directly opposite the A' vent, and then place the growth device in the cavity 9 of the heating device;

[0064] 2. Growth preparation stage

[0065] (1) The pressure in the growth chamber 2 is reduced to below 10 -6 mbar, and the temperature is increased to a first temperature of 1200-1600 ℃, which is maintained for 2-5 h;

[0066] (2) Inert gas is introduced into the growth chamber 2 to increase the pressure to a growth pressure of 0-120 mbar, which is maintained for 1-3 h, and the purity of the inert gas is greater than 99.999%;

[0067] (3) The first temperature and the growth pressure are kept constant, and different gas sources are introduced into the upper chamber through the vents, with a gas flow of 1-300 sccm, and the gas is introduced for 1-3 h to allow the gas to mix and stabilize, thereby constructing a concentration gradient from the A vent (1# vent) to the A' vent (5# vent) with gradually decreasing Si-containing atmosphere and gradually increasing C-containing atmosphere, which prepares for the later crystal growth.

[0068] Specifically, taking the number of the second pair of ventilation ports as 3 pairs as an example, the A ventilation ports are sequentially marked as 1#-8# ventilation ports, the A ventilation port is the 1# ventilation port, the A' ventilation port is the 5# ventilation port, each ventilation port is connected to different gas sources through a graphite guide pipe, the silicon-containing gas is a silane gas, the C-containing atmosphere is an alkane gas, the purity of the silane gas and the alkane gas is greater than 99.999%, the alkane gas includes methane and / or ethane, the silane gas includes monosilane and / or disilane, the 3# and 7# ventilation ports are connected to the alkane gas and the silane gas at a volume ratio of 1:1, the 2# and 8# ventilation ports are connected to the alkane gas and the silane gas at a volume ratio of 1:3, the 4# and 6# ventilation ports are connected to the alkane gas and the silane gas at a volume ratio of 3:1, the 1# gas hole is connected to the silane gas, and the 5# gas hole is connected to the alkane gas, thereby constructing a gradient change from the A ventilation port to the A' ventilation port, in which the Si-containing atmosphere gradually decreases and the C-containing atmosphere gradually increases.

[0069] 3. Crystal growth phase:

[0070] (1) First crystal growth phase: the growth pressure in the upper chamber is kept unchanged, the gas flow of the ventilation ports is kept unchanged, the first temperature is increased to the second temperature 2000-2500℃, the silicon carbide crystal growth is performed, and the growth time is 18-55h;

[0071] (2) Second crystal growth phase: the second temperature is kept in the upper chamber, and the gas flow of each ventilation port is gradually and uniformly reduced to 1 / 3-1 / 2 of the original gas flow within 18-55h;

[0072] (3) Third crystal growth phase: the second temperature is kept in the upper chamber, the gas flow of the ventilation ports at the end of the second crystal growth phase is kept, the silicon carbide crystal growth is continued, and the crystal growth time of the third crystal growth phase is 18-55h.

[0073] In a conventional crystal growth process, the nucleation center is generally at a certain distance, such as 1 / 4 diameter, from the center in the <11-20> direction. The transmission growth distance of the growth steps from the nucleation center in the radial direction will have a large difference. The transmission distance in the <11-20> direction is the shortest, and the transmission distance in the <-1-120> direction is the longest. In the transmission process in the <-1-120> direction, the crystal center, which is the center of the temperature field and the lowest temperature point, will be passed through. The separation of the two centers will inevitably disturb the crystal growth process. The step information of the nucleation center cannot effectively pass through the crystal center, resulting in loss, mismatch or even mismatch of growth information, which has a great hidden danger for improving the crystal quality. The concentration gradient change of the Si-containing atmosphere and / or C-containing atmosphere constructed in the present application guides the nucleation center to shift towards the crystal center, so that the nucleation center can be close to or even coincide with the crystal center. After the two centers coincide, the transmission growth distance of the growth information of the steps in each direction is the same. In this way, the growth information can be effectively transmitted to the maximum extent without causing disturbance.

[0074] 4. After the growth is completed, the silicon carbide crystal is removed from the growth device after cooling.

[0075] 5. The obtained silicon carbide crystal is processed by cutting, grinding, polishing and the like to obtain an improved silicon carbide seed crystal. The seed crystal is used to repeat the processes of steps 1-5. After at least 2-3 rounds, a silicon carbide crystal with the nucleation center coinciding with the crystal center can be obtained.

[0076] 6. The silicon carbide crystal with the nucleation center coinciding with the crystal center is processed by cutting, grinding, polishing and the like to obtain a silicon carbide seed crystal and a substrate with the nucleation center coinciding with the crystal center.

[0077] In an embodiment, the pressure of the upper chamber is 5-120 mbar, the pressure of the lower chamber is 0-100 mbar, the pressure of the upper chamber is greater than that of the lower chamber, and the pressure difference between the upper and lower chambers is 5-20 mbar, so as to ensure that the gas in the upper chamber is quickly guided to the lower chamber through the pores of the porous graphite partition plate, maintain the dynamic balance of the pressure and various gas components in the upper chamber, and the temperature change amount of the lower chamber from top to bottom is 0.1-10 ℃ / mm. The temperature of the upper chamber is the temperature of the top of the lower chamber, which ensures that the silicon carbide powder is fully recrystallized, constructs a stable temperature field and flow field structure for silicon carbide single crystal growth, reduces or eliminates the crystal defects (such as stress, TED, TSD, surface type, etc.) caused by air flow disturbance, and further improves the crystal quality.

[0078] The following Table 1 is the step-related parameters of the silicon carbide crystals 1#-5# prepared according to the above preparation method, and the related parameters of the comparative silicon carbide crystals D1#-D3#, and the measurement of the distance between the nucleation center point 105 and the crystal center point 103 of the silicon carbide crystals 1#-5# and D1#-D3#. The growth device used for the silicon carbide crystal D1# does not have a vent relative to the growth device claimed in the present application used for the silicon carbide crystal 3#, and the steps and parameters other than those related to the vent are the same. The difference between the preparation method of D2# and the silicon carbide crystal 3# is that the pressure difference between the upper and lower chambers is less than 5 mbar, and the other steps and parameters are the same. The difference between the preparation method of D3# and the silicon carbide crystal 3# is that the pressure difference between the upper and lower chambers is greater than 25 mbar, and the other steps and parameters are the same.

[0079] Table 1

[0080]

[0081] It should be noted that the above facet refers to the facet formed by the nucleation morphology 104, and the nucleation morphology is generally circular, and the facet diameter is the diameter of the nucleation morphology.

[0082] As can be seen from the above Table 1, the silicon carbide crystals 1#-5# prepared by the silicon carbide crystal growth device and the preparation method of the present application have the distance between the nucleation center point 105 (i.e. the facet center point) and the crystal center point 103 controlled within the range of 0-20 mm, and the distance between the two center points is <1 / 10 of the crystal diameter. In addition, the facet diameter of the silicon carbide crystal 10 is 50-200 mm, the diameter of the silicon carbide crystal 10 is ≥100 mm, the facet diameter is 1 / 4-1 / 2 of the diameter of the silicon carbide crystal 10, and the facet area is 1 / 16-1 / 4 of the main surface area of the silicon carbide crystal 10. After the silicon carbide crystals 1#-5#, D2# and D3# repeat steps 1-5 three times, the nucleation center point 105 and the crystal center point 103 can completely coincide, indicating that the coincidence degree of the nucleation center and the crystal center is high, and even completely coincides. The nucleation center point 105 and the crystal center point 103 of the comparative silicon carbide crystal D1# always have a certain distance and exceed 30 mm, indicating that the coincidence degree of the nucleation center and the crystal center is relatively low, far lower than the coincidence degree of the two centers of the silicon carbide crystals 1#-5#.

[0083] Table 2 is the performance test of silicon carbide crystals 1#-5#, D2# and D3# after repeating steps 1-5, the performance includes thread dislocation TSD density, edge dislocation TED density, surface stress absolute value, crystalline quality, Bow, Warp, TTV, LTV, and the performance test of silicon carbide seeds Z1#-Z5# and substrates C1#-C5# after processing such as cutting, grinding and polishing of the silicon carbide crystals 1#-5# with the nucleation center point 105 coinciding with the crystal center point 103.

[0084] It should be noted here that the process of cutting, grinding, polishing and the like to obtain seeds or substrates from silicon carbide crystals is prior art and will not be described here. In addition, the crystal center point is defined as the intersection of the axis of the silicon carbide crystal and the first main surface 101 and the second main surface 102 as the crystal center point; the related distance parameters of the crystal center point and the nucleation center point are measured on the first main surface.

[0085]

[0086] From Table 2, it can be seen that the TSD in the facet range of the silicon carbide crystals 1#-5#, the silicon carbide seeds Z1#-Z5# and the substrates C1#-C5# is less than 150 / cm 2 , the TED is less than 1500 / cm 2 , the TSD outside the facet range is less than 100 / cm 2 , the TED is less than 1000 / cm 2 ; the surface stress absolute value is less than 15 MPa, the in-plane difference is less than 20 MPa; the crystalline quality is less than 25 arcs (arc seconds); the Bow is less than 5 um, the Warp is less than 10 um, the TTV is less than 3 um, and the LTV is less than 1 um. The difference between the preparation methods of D2# and silicon carbide crystal 3# is that the pressure difference between the upper and lower chambers is less than 5 mbar, and the other steps and parameters are the same; the difference between the preparation methods of D3# and silicon carbide crystal 3# is that the pressure difference between the upper and lower chambers is greater than 25 mbar, and the other steps and parameters are the same, the performance test results of D2# and D3# are all worse than those of silicon carbide crystals 1#-5#, which shows that too small or too large pressure difference between the upper and lower chambers will affect the pressure in the upper chamber and the dynamic balance of various gas phases, and then affect the flow field structure of the silicon carbide single crystal growth construction, increase or produce crystal defects caused by air flow disturbance, and then affect the quality of the crystal.

[0087] The above merely illustrates the embodiments of the present application, and the protection scope of the present application is not limited to these specific embodiments, but determined by the claims of the present application. The present application can have various changes and modifications for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the technical thought and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A silicon carbide crystal, characterized by, The silicon carbide crystal has a first main surface and a second main surface opposite to the first main surface, the first main surface and / or the second main surface has a nucleation morphology, the nucleation morphology has a nucleation center point, a central axis of the silicon carbide crystal penetrates the first main surface and the second main surface, and an intersection point of the central axis and the first main surface and / or the second main surface is a crystal center point; On the first main surface and / or the second main surface, a distance from the nucleation center point to the crystal center point is less than 1 / 10 of a diameter of the silicon carbide crystal, The silicon carbide crystal is prepared by a PVT method.

2. The silicon carbide crystal according to claim 1, wherein The nucleation center point coincides with the crystal center point.

3. The silicon carbide crystal of claim 1, wherein, The distance between the nucleation center point and the crystal center point is 0-25 mm.

4. The silicon carbide crystal according to claim 3, wherein The distance between the nucleation center point and the crystal center point is 0-20 mm.

5. The silicon carbide crystal of Claim 1 wherein, The first main surface is a {0001} surface.

6. The silicon carbide crystal of Claim 5, wherein The nucleation center point is deviated from a center of the {0001} surface to a <11-20> direction.

7. The silicon carbide crystal of Claim 1 wherein, The nucleation morphology is circular, a ratio of a diameter of the nucleation morphology to a diameter of the silicon carbide crystal is 1 / 5-2 / 3, and a ratio of an area of the nucleation morphology to an area of the first main surface or the second main surface is 1 / 25-4 / 9.

8. The silicon carbide crystal according to claim 7, wherein The ratio of the diameter of the nucleation morphology to the diameter of the silicon carbide crystal is 1 / 4-1 / 2, and the ratio of the area of the nucleation morphology to the area of the first main surface or the second main surface is 1 / 16-1 / 4.

9. The silicon carbide crystal of Claim 7, wherein, The diameter of the nucleation morphology is 40 mm-220 mm, and the diameter of the silicon carbide crystal is greater than or equal to 90 mm.

10. The silicon carbide crystal according to claim 9, wherein The diameter of the nucleation morphology is 50 mm-200 mm, and the diameter of the silicon carbide crystal is greater than or equal to 100 mm.

11. The silicon carbide crystal of Claim 1 wherein, The TSD of the crystal region around the nucleation morphology is less than 160 / cm 2 , the TED is less than 1600 / cm 2 ; the TSD of the crystal region outside the nucleation morphology is less than 120 / cm 2 , the TED is less than 1100 / cm 2 , the absolute value of the surface stress of the crystal is less than 18 Mpa, the difference inside the nucleation morphology is less than 25 Mpa, and the crystallization quality of the crystal is less than 28 arcs.

12. The silicon carbide crystal according to claim 11, wherein TSD of the crystal region surrounding the nucleation morphology is less than 150 / cm 2 , TED is less than 1500 / cm 2 ; TSD of the crystal region outside the nucleation morphology is less than 100 / cm 2 , TED is less than 1000 / cm 2 , the absolute value of surface stress of the crystal is less than 15 Mpa, the difference inside the nucleation morphology is less than 20 Mpa, and the crystallization quality of the crystal is less than 25 arcs.

13. A silicon carbide seed crystal, characterized by, The silicon carbide seed crystal is prepared by cutting, grinding and polishing the silicon carbide crystal according to any one of claims 1-12.

14. A silicon carbide substrate, characterized by, The silicon carbide substrate is prepared by cutting, grinding and polishing the silicon carbide crystal according to any one of claims 1-12.

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