CN115652432A - Silicon carbide crystal, seed crystal and substrate - Google Patents
Silicon carbide crystal, seed crystal and substrate Download PDFInfo
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- CN115652432A CN115652432A CN202211366501.2A CN202211366501A CN115652432A CN 115652432 A CN115652432 A CN 115652432A CN 202211366501 A CN202211366501 A CN 202211366501A CN 115652432 A CN115652432 A CN 115652432A
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Abstract
The application discloses silicon carbide crystal belongs to the semiconductor material field. The silicon carbide crystal comprises a first main surface and a second main surface opposite to the first main surface, wherein the first main surface and/or the second main surface are/is provided with nucleation features, the nucleation features are provided with nucleation center points, a central axis of the silicon carbide crystal penetrates through the first main surface and the second main surface, and the intersection point of the central axis and the first main surface and/or the second main surface is the crystal center point; the distance from the nucleation center point to the crystal center point is less than 1/4 of the diameter of the silicon carbide crystal. The distance between the nucleation center point of the silicon carbide crystal and the crystal center point is less than 1/4 of the diameter of the silicon carbide crystal, the distance between the two center points is smaller, the nucleation quality is high, and the defect density is low.
Description
Technical Field
The application relates to a silicon carbide crystal, a seed crystal and a substrate, belonging to the field of semiconductor materials.
Background
Silicon carbide is a typical wide bandgap semiconductor material and is one of the representatives of the third generation of semiconductor materials following silicon, gallium arsenide. The silicon carbide material has excellent characteristics of high thermal conductivity, high breakdown field strength, high saturated electron mobility and the like, and becomes one of hot materials for preparing high-temperature, high-frequency, high-power and anti-radiation devices.
At present, the methods for growing silicon carbide mainly include Physical Vapor Transport (PVT), liquid Phase Epitaxy (LPE), chemical Vapor Deposition (CVD), etc., wherein the PVT is the most well-established method and is the only growth method that can meet the requirements of commercial silicon carbide substrates. The growth furnace for growing the silicon carbide crystal by the PVT method generally adopts an induction heating mode, namely medium-frequency alternating current is electrified in an induction coil, silicon carbide powder in a growth chamber is heated through induction heating of a crucible, the powder is decomposed, and the crystal grows at a seed crystal with lower temperature, so that the growth of the crystal is realized. The PVT method for growing the silicon carbide crystal usually needs to construct a very uniform temperature field at the seed crystal, and uniform upward transmission and ordered arrangement of the silicon carbide atmosphere are realized through a stable radial temperature gradient and an axial temperature gradient, so that the high-quality silicon carbide crystal with low defect density is obtained. For defects such as micropipes, impurities, small-angle grain boundaries, long-range lattice distortion and the like, researchers do a lot of work on the aspect of seed crystal angles, and in order to obtain a sufficiently high growth step density, the seed crystal for growing the silicon carbide crystal usually grows by the seed crystal of which the (0001) plane (namely the Si plane) deviates to the <11-20> direction by a certain angle, so that growth information can be effectively transmitted, and the defect density of the crystal is greatly reduced. And continuously transmitting growth step information through the nucleation center in a spiral growth mode in the crystal growth process of the silicon carbide crystal to finally form a facet structure, and performing step flow growth on the region outside the facet according to the growth step information transmitted by the nucleation center.
Nucleation is a very important link in the growth of the silicon carbide crystal, and the quality of nucleation can directly determine the crystallization quality of the silicon carbide crystal in the later period. Although the crystal quality can be improved by carrying out the silicon carbide growth by the seed crystal with the (0001) plane (namely the Si plane) deviated to the <11-20> direction for a certain angle, the existence of the angle can also deviate the nucleation center to the <11-20> direction, so that the nucleation center (namely the formed facet center point) is not coincident with the crystal center or the coincidence rate is low. The crystal center is often the temperature field center, namely the lowest radial temperature point, the growth speed is the fastest in the radial direction, and the misalignment between the nucleation center and the temperature field center can cause that 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 the defects of secondary microtubules, polytype, stacking faults, dislocation and the like restrict the further improvement of the crystal quality.
Disclosure of Invention
In order to solve the problems, 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 smaller, the nucleation quality is high, and the defect density is low.
According to one aspect of the present application, a silicon carbide crystal is provided having a first major surface and a second major surface opposite the first major surface, the first major surface and/or the second major surface having a nucleation feature with a nucleation center point, a central axis of the silicon carbide crystal extending through the first major surface and the second major surface, the intersection of the central axis with the first major surface and/or the second major surface being the crystal center point;
the distance from the nucleation center point to the crystal center point at the first and/or second major surface is less than 1/4 the diameter of the silicon carbide crystal.
Preferably, the distance from the nucleation center point to the crystal center point is less than 1/5 of the diameter of the silicon carbide crystal;
preferably, the distance from the nucleation center point to the crystal center point is less than 1/10 of the diameter of the silicon carbide crystal;
preferably, the distance from the nucleation center point to the crystal center point is less than 1/12 of the diameter of the silicon carbide crystal;
more preferably, the nucleation center coincides with the crystal center.
Optionally, the distance between the nucleation center point and the crystal center point is 0-25mm;
preferably, the distance between the nucleation center point and the crystal center point is 0-20mm;
more preferably, the distance between the nucleation center point and the crystal center point is 0-15mm;
preferably, the distance between the nucleation center point and the crystal center point is 0-10mm;
preferably, the distance between the nucleation center point and the crystal center point is 0-6mm;
preferably, the distance between the nucleation center point and the crystal center point is 0-3mm;
more preferably, the nucleation center point is spaced from the crystal center point by a distance of 0.
Optionally, the first major surface is a {0001} plane.
Optionally, the nucleation center point is biased toward a <11-20> direction at the center of the {0001} plane.
Optionally, the nucleation features are substantially circular, the ratio of the diameter of the nucleation features to the silicon carbide crystal diameter is 1/5-2/3, and the ratio of the area of the nucleation features to the area of the first or second major surface is 1/25-4/9;
preferably, the ratio of the diameter of the nucleation features to the silicon carbide crystal diameter is 1/4 to 1/2 and the ratio of the area of the nucleation features to the area of the first or second major surface is 1/16 to 1/4.
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;
preferably, the diameter of the nucleation morphology is 50mm-200mm, and the diameter of the silicon carbide crystal is more than or equal to 100mm.
Optionally, the TSD of the surrounding crystalline region within the nucleation profile is less than 160/cm 2 TED less than 1600/cm 2 (ii) a The TSD of the crystal region outside the nucleation morphology is less than 120/cm 2 TED less than 1100/cm 2 ；
Preferably, the TSD of the surrounding crystalline region within the nucleation profile is less than 150/cm 2 TED less than 1500/cm 2 (ii) a The TSD of the crystal region outside the nucleation morphology is less than 100/cm 2 TED less than 1000/cm 2 ；
More preferably, the TSD of the crystal region surrounding within the nucleation morphology is less than 120/cm2 and the TED is less than 1300/cm2; the TSD of the crystal area outside the nucleation morphology is less than 80/cm < 2 >, and the TED is less than 700/cm < 2 >.
Optionally, the absolute value of the surface stress of the crystal is less than 18Mpa, the difference value in the nucleation morphology is less than 25Mpa, and the crystallization quality of the crystal is less than 28arcs;
preferably, the absolute value of the surface stress of the crystal is less than 15Mpa, the difference value in the nucleation morphology is less than 20Mpa, and the crystallization quality of the crystal is less than 25arcs.
According to another aspect of the present application, there is provided a silicon carbide seed crystal produced by cutting, grinding and polishing a silicon carbide crystal according to any of the above.
According to still another aspect of the present application, there is provided a silicon carbide substrate obtained by cutting, grinding and polishing a silicon carbide crystal according to any one of the above.
The central point of the crystal referred to in the present application is defined as the crystal central point at the intersection of the central axis of the silicon carbide crystal with the first major surface ({ 0001} plane) and the second major surface;
the crystal center referred to in this application refers to the extension of the crystal center point of the first major surface to the crystal center point of the second major surface, and is also the temperature field center, i.e., the radial temperature lowest point;
reference herein to a nucleation center refers to the extension of the nucleation center point of the nucleation feature of the first major surface towards the nucleation center point of the nucleation feature of the second major surface.
The position relationship between the nucleation center point and the crystal center point can effectively reflect the position relationship between the crystal center and the nucleation center.
Benefits of the present application include, but are not limited to:
1. according to the silicon carbide crystal, the distance between the nucleation center point and the crystal center point is smaller than 1/4 of the diameter of the silicon carbide crystal, and the distance between the two center points is smaller, so that the coincidence degree of the nucleation center and the crystal center is higher or completely coincident, the nucleation quality is higher, and the defect density is lower.
2. According to the silicon carbide seed crystal, the distance between the nucleation center point and the crystal center point is small or the nucleation center point is coincident, so that the growth step information of the nucleation center can be effectively transmitted to the crystal center and the opposite area symmetrical about the crystal center, and the nucleation quality of the silicon carbide crystal generated by the seed crystal can be further improved.
3. According to the silicon carbide substrate, 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.
4. According to the silicon carbide crystal, seed crystal and substrate of the present application, bow is less than 5um, warp is less than 10um, TTV is less than 3um, and LTV is less than 1um.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
FIG. 1 is a schematic axial cross-sectional view of a silicon carbide crystal growing apparatus according to an embodiment of the present application.
FIG. 2 is a top view of a silicon carbide crystal growth apparatus according to embodiments of the present application.
Figure 3 is a schematic radial cross-sectional view of an upper chamber of a silicon carbide crystal growing apparatus according to an embodiment of the present application.
FIG. 4 shows a silicon carbide crystal of the background art in which the nucleation center and the crystal center do not coincide.
FIG. 5 shows a silicon carbide crystal with a nucleation center coincident with the crystal center according to an embodiment of the present application.
1. A crucible body, 2 a growth chamber, 21 an upper chamber, 22 a lower chamber, 3 a seed crystal placing part (seed crystal), 4 a porous graphite partition plate, 5, siC powder, 6 a porous graphite table, 7 a graphite connecting cylinder, 8a cover body, 9 and a cavity,
10. silicon carbide crystal 101, first major surface 102, second major surface 103, crystal center point 104, nucleation feature 105, nucleation center point.
A.A vent (vent # 1), A '. A' vent (vent # 5), vent # 2-4, vent # 6-8.
Detailed Description
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
The raw materials in the examples of the present application were all purchased commercially, unless otherwise specified.
The embodiment provides a silicon carbide crystal growth device, in order to be used for producing the silicon carbide crystal that the distance of nucleation center point 105 and crystal center point 103 is little or the coincidence, refer to fig. 1-3, fig. 5, this silicon carbide crystal growth device includes the crucible body 1, a plurality of blow vents are seted up to the lateral wall of growth chamber 2 in the crucible body 1, the same high department of the lateral wall at growth chamber 2 is established to the blow vent, the blow vent includes a first pair of blow vent, a blow vent and A 'blow vent are drawn together to the first pair of blow vent, A blow vent and A' blow vent are symmetrical about the axis of growth chamber 2 and are set up, A blow vent and A 'blow vent place sharp bilateral symmetry are equipped with the second pair of blow vent, let in the atmosphere of different concentration gradients in to growth chamber 2 along the lateral wall of growth chamber 2 from A blow vent to A' blow vent. The nucleation center of the existing silicon carbide crystal 10 is generally deviated to a certain distance in the <11-20> direction at the crystal center of the silicon carbide crystal 10 in the crystal growing process, for example, at 1/4 of the diameter of the silicon carbide crystal 10, the growth step information emitted from the nucleation center and the transmission growth distance in the radial direction of the silicon carbide crystal 10 have a large difference, the transmission distance in the <11-20> direction is shortest, the transmission distance in the < -1-120> direction is longest, and the transmission process in the < -1-120> direction passes through the crystal center, the crystal center is a thermal field center, the temperature is the lowest point, the growth speed is the fastest, the separation of the nucleation center and the crystal center inevitably causes disturbance to the crystal growing process of the silicon carbide crystal, the step information in the nucleation center cannot effectively pass through the crystal center, so that the growth information is lost, mismatched or even mismatched, and the great risk is caused to the improvement of the crystal quality. Therefore, a plurality of air vents are arranged at the same height of the growth chamber, so that the Si atmosphere gradually decreases from the air vent A to the air vent A', the C-containing atmosphere gradually increases in gradient change, and the nucleation center is guided to move towards the center of the crystal (namely, the temperature field center).
The number of the second pair of air vents is odd number, and the second pair of air vents are uniformly distributed on two sides of a straight line where the first pair of air vents are located; the number of the second pair of vents may be 1, 3, 5 or 7, and the number of the second pair of vents may be set according to actual conditions, in a specific embodiment, the number of the second pair of vents is 3, referring to fig. 2 and 3, the vents labeled as vent # 1-8 in sequence from vent a, vent # 1-8 are uniformly distributed on the peripheral sidewall of the growth chamber, vent a is vent # 1, vent a' is vent # 5, each vent is connected to different gas sources through a graphite conduit, the silicon-containing atmosphere is silane gas, the C-containing atmosphere is alkane gas, the alkane gas includes methane and/or ethane, the silane gas includes silane and/or disilane, and the volume ratio of the alkane gas introduced into vent # 3 and vent # 7 to the silane gas is 1: the volume ratio of alkane gas to silane gas introduced into the vent holes 1,2# and 8# is 1:3,4# and 6# vents are filled with alkane gas and silane gas in a volume ratio of 3: silane gas is completely introduced into the 1,1# vent, alkane gas is completely introduced into the 5# vent, and then gradient change that Si gas is gradually reduced and gas containing C is gradually increased from the A vent to the A' vent is constructed.
In an embodiment, referring to fig. 1, a porous partition is provided in the crucible body 1, and divides the growth chamber into an upper chamber 21 and a lower chamber 22, wherein a vent is provided on a sidewall of the upper chamber 21, and the porous partition is capable of transferring an atmosphere in the upper chamber 21 to the lower chamber 22. The growth chamber 2 is divided into an upper chamber 21 and a lower chamber 22 by the porous partition, the vent is 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 can ensure that the atmosphere introduced into the upper chamber 21 can be effectively and quickly led out, so that the dynamic balance of the pressure in the upper chamber and various gas-phase components is maintained, a stable temperature field and flow field structure is constructed for the growth of the silicon carbide crystal, the defects (such as stress, TED, TSD, surface type and the like) of the silicon carbide crystal caused by air flow disturbance are reduced or eliminated, and the quality of the silicon carbide crystal is improved. In addition, the lower chamber 22 can also be used as a raw material recrystallization recovery area, a certain temperature gradient difference is constructed, and the unreacted atmosphere of the upper chamber 21 enters the lower chamber 22 and is gradually recrystallized to obtain high-purity silicon carbide powder, so that the raw material is recycled.
In one embodiment, the porous partition is a porous graphite partition plate 4, and the density of the porous graphite partition plate 4 is less than that of the crucible body. The porous partition is a porous graphite partition plate 4, so that gas introduced into the upper chamber 21 can be effectively discharged in time, and meanwhile, a pressure difference formed by the upper chamber 21 and the lower chamber 22 can form downward airflow, so that C particles are effectively inhibited from moving upwards to enter the silicon carbide crystals, and the number of inclusions of the silicon carbide crystals is reduced. The crucible body is usually the graphite crucible body, and the density of porous graphite division plate 4 is less than the density of the graphite crucible body, makes the gaseous recrystallization gradually after entering cavity 22 under the unreacted gas of upper chamber 21 obtain the carborundum powder of high-purity, realizes raw materials reuse.
In one embodiment, the porous graphite separator plate 4 has a density of 0.2 to 1.5g/cm 3 The density of the graphite crucible body is usually 1.3 to 2.5g/cm 3 (ii) a Further, the porous graphite separator 4 has a density of 0.3 to 1.3g/cm 3 。
The inner side of the top cover body 9 of the upper cavity 21 is provided with a seed crystal placing part, and the air vent A' is over against the <11-20> direction of the seed crystal placing part 3 (also the <11-20> direction of the seed crystal); the vent is opened in a position where the side wall of the upper chamber 21 is close to the seed crystal placement section 3. Since the nucleation center of silicon carbide crystal 10 is generally deviated to a certain distance in the <11-20> direction at the crystal center of silicon carbide crystal 10, the air vent A 'faces the <11-20> direction of seed crystal placing part 3, the concentration of the Si-containing atmosphere in the air vent A' is the lowest, the concentration of the C-containing atmosphere is the highest, the concentration of the Si-containing atmosphere in the air vent A is the highest, and the concentration of the C-containing atmosphere is the lowest, which is more favorable for guiding the nucleation center to move to the crystal center (namely, the temperature field center).
The silicon carbide crystal growing device also comprises a porous graphite platform 6, and a lower chamber 22 is enclosed by the porous graphite platform 6, the side wall of the crucible body and a porous separator; the porous graphite stage 6 has a density less than that of the crucible body 1. The density of porous graphite platform 6 is less than the density of the crucible body 1, thereby can avoid the atmosphere that gets into lower cavity 22 to get into the lateral wall precipitation carborundum grain of the graphite crucible body and cause the life-span that the erosion prolongs insulation construction to the insulation construction of the crucible body 1, plays the effect of cost reduction increase. Further, the porous graphite stage 6 has a hollow boss shape, the top of the porous graphite stage 6 extends toward the porous separator, and the porous graphite stage 6 has one shape selected from a circular truncated cone shape, a conical shape, and a cylindrical shape, but is not limited to these shapes. The hollow part of the porous graphite platform 6 is provided with a graphite connecting cylinder 7, and one end of the graphite connecting cylinder 7 extends towards the direction far away from the lower chamber 22. The graphite connecting cylinder 7 is connected with a gas treatment device through a graphite guide pipe, and the gas treatment device absorbs redundant atmosphere, so that the corrosion of the atmosphere to the heat insulation structure of the crucible body 1 is avoided.
The density of the graphite connecting cylinder 7 is less than that of the crucible body 1; the density of the graphite connecting cylinder 7 is not greater than that of the porous graphite stage 6. The density of graphite connecting cylinder 7 is less than the density of the crucible body 1, is not more than the density of porous graphite platform 6, thereby can avoid the atmosphere that gets into lower cavity 22 to get into the lateral wall of the graphite crucible body and separate out the carborundum grain and cause the erosion to the heat preservation of the crucible body 1 and prolong the heat preservation life.
In one embodiment, the diameter of the upper chamber 21 is 100-300mm, the height is 150-500mm, the aperture of the vent is 5-20mm, the thickness of the side wall of the crucible body is 10-30mm, the height of the lower chamber 22 is 150-500mm, the distance from the top of the porous graphite table 6 to the bottom of the porous partition is 30-100mm, and the temperature variation of the lower chamber 22 from top to bottom is 0.1-10 ℃/mm, so as to ensure that the silicon carbide powder is fully recrystallized.
In the present embodiment, there is also provided a silicon carbide crystal growth method, using the above growth apparatus, the silicon carbide crystal growth method including the steps of:
1. assembling stage
(1) Assembling a crucible body 1, seed crystals, siC powder 5, a porous graphite partition plate 4, a porous graphite table 6 and a graphite connecting cylinder 7 according to a figure 1, wherein the <11-20> direction of a seed crystal unit is opposite to an A' vent, and then placing a growth device into a cavity 9 of a heating device;
2. preparation stage of crystal growth
(1) The pressure in the growth chamber 2 is pumped to 10 -6 mbar, and raising the temperature to 1200-1600 ℃ at the first temperature for 2-5h;
(2) Introducing inert gas into the growth chamber 2, increasing the pressure to the growth pressure of 0-120mbar, and keeping the pressure for 1-3h, wherein the purity of the inert gas is more than 99.999%;
(3) Keeping the first temperature and the growth pressure unchanged, introducing gases with specific components into the upper chamber from different gas sources through the vent holes, wherein the gas flow is 1-300sccm, and the introduction lasts for 1-3h, so that the gases are fully and stably mixed, and the concentration gradient change that the Si-containing atmosphere is gradually reduced and the C-containing atmosphere is gradually increased from the vent hole A (vent hole No. 1) to the vent hole A (vent hole No. 5) is constructed, so as to prepare for later-stage crystal growth.
Specifically, taking the second pair of vents as an example, the vents from vent a are labeled as vent 1# -8# in sequence, vent a is vent 1#, vent a' is vent 5#, each vent is connected to different gas sources through a graphite conduit, the gas containing silicon is silane gas, the atmosphere containing C is alkane gas, the purity of both silane gas and alkane gas is greater than 99.999%, the alkane gas includes methane and/or ethane, the silane gas includes silane and/or disilane, and the volume ratio of alkane gas and silane gas introduced from vent 3# and vent 7# is 1: the volume ratio of alkane gas to silane gas introduced into the vent holes 1,2# and 8# is 1: 5363 and the volume ratio of alkane gas and silane gas introduced into the vents of 3,4# and 6# is 3: the 1,1# air hole is completely filled with silane gas, the 5# air hole is completely filled with alkane gas, and the Si atmosphere is gradually reduced from the A air hole to the A' air hole, and the gradient change of the C-containing atmosphere is gradually increased is constructed.
3. Crystal growth stage:
(1) A first crystal growth stage: keeping the growth pressure in the upper chamber unchanged, keeping the gas flow of the vent unchanged, raising the first temperature to 2000-2500 ℃ of the second temperature, and growing the silicon carbide crystal for 18-55 hours;
(2) A second crystal growth stage: keeping the second temperature in the upper chamber, and gradually and uniformly reducing the gas flow of each vent to 1/3-1/2 of the original gas flow within 18-55 h;
(3) A third crystal growth stage: and keeping the second temperature in the upper chamber, keeping the gas flow of the final gas inlet vent in the second crystal growth stage, and continuing to grow the silicon carbide crystal, wherein the crystal growth time in the third crystal growth stage is 18-55h.
In the conventional crystal growth process, the nucleation center generally deviates from the center in the direction of <11-20> for a certain distance, for example, at the position of 1/4 diameter, the transmission growth distance of the growth step emitted from the nucleation center in the radial direction has larger difference, the transmission distance in the direction of <11-20> is shortest, the transmission distance in the direction of < 1-120> is longest, the transmission distance in the direction of < 1-120> passes through the crystal center, the crystal center is the temperature field center, the temperature is the lowest point, the growth speed per se is fastest, the separation of the two centers inevitably causes disturbance to the crystal growth process, the step information in the nucleation center cannot effectively pass through the crystal center, the growth information is lost, mismatched and even mismatched, and great hidden danger is brought to the improvement of the crystal quality; the concentration gradient change of the Si-containing atmosphere and/or the C-containing atmosphere constructed by the method guides the nucleation center to shift to the crystal center, so that the nucleation center is close to the crystal center and even coincides, and the transmission growth distances of the growth information of the two center-coincident back steps to all directions are the same, so that the growth information can be effectively transmitted to the maximum extent, and disturbance can not be caused.
4. And after the growth is finished, cooling and taking out the silicon carbide crystal from the growth device.
5. Cutting, grinding, polishing and the like the obtained silicon carbide crystal to obtain an improved silicon carbide seed crystal, repeating the steps 1-5 by using the seed crystal, and obtaining the silicon carbide crystal with the nucleation center coincident with the crystal center after at least 2-3 rounds;
6. and cutting, grinding, polishing and the like are carried out on the silicon carbide crystal with the nucleation center coinciding with the crystal center, so as to obtain the silicon carbide seed crystal and the substrate with the nucleation center coinciding with the crystal center.
In one embodiment, the pressure of the upper chamber is 5-120mbar, the pressure of the lower chamber is 0-100mbar, the pressure of the upper chamber is greater than that of the lower chamber, the pressure difference between the upper chamber and the lower chamber is 5-20mbar to ensure that the gas in the upper chamber is rapidly guided to the lower chamber through the pores of the porous graphite partition plate, the dynamic balance of the pressure in the upper chamber and various gas-phase components is maintained, the temperature variation of the lower chamber from top to bottom is 0.1-10 ℃/mm, the temperature of the upper chamber is the temperature at the top of the lower chamber, the silicon carbide powder is ensured to be fully recrystallized, a stable temperature field and flow field structure is constructed for the growth of the silicon carbide single crystal, and crystal defects (such as stress, TED, TSD, surface type and the like) caused by gas flow disturbance are reduced or eliminated, so that the crystal quality is improved.
Table 1 below shows the parameters associated with the steps of preparing silicon carbide crystal 1# -5# according to the above-described preparation method, the parameters associated with comparative silicon carbide crystal D1# -D3#, and the parameters associated with the distances between the nucleation center 105 and the crystal center 103 of silicon carbide crystals 1# -5# and D1# -D3 #. The growing device used for the silicon carbide crystal D1# is not provided with a vent relative to the growing device used for the silicon carbide crystal 3# and the other steps and parameters are the same except for the steps and parameters related to the vent; the preparation method of the D2# and the silicon carbide crystal 3# is different in that the pressure difference of an upper cavity and a lower cavity is less than 5mbar, and other steps and parameters are the same; the difference between the preparation method of the D3# and the preparation method of the silicon carbide crystal 3# is that the pressure difference of the upper chamber and the lower chamber is more than 25mbar, and other steps and parameters are the same.
TABLE 1
It should be noted that the above-mentioned facets refer to facets formed by the nucleation feature 104, the nucleation feature is substantially circular, and the diameter of the facet is the diameter of the nucleation feature.
As can be seen from the above Table 1, the distance between the nucleation center 105 (i.e., the facet center) and the crystal center 103 is controlled within the range of 0-20mm, and the distance between the two centers is less than 1/10 of the crystal diameter for the silicon carbide crystal 1# -5# prepared by the silicon carbide crystal growth apparatus and the preparation method of the present application. In addition, the facet diameter of the silicon carbide crystal 10 is 50-200mm, the diameter of the silicon carbide crystal 10 is more than or equal to 100mm, 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# are subjected to the step 1-5 repeatedly for three times, the nucleation center point 105 and the crystal center point 103 can be completely coincided, which shows that the coincidence degree of the nucleation center and the crystal center is higher, even completely coincided; and compared with the nucleation center 105 and the crystal center 103 of the silicon carbide crystal D1# which are always at a certain distance and exceed 30mm, the coincidence degree of the nucleation center and the crystal center is lower and far inferior to that of the two centers of the silicon carbide crystal 1# -5 #.
Table 2 shows the performance tests of the silicon carbide crystals 1# -5#, D2# and D3# after the steps 1-5 are repeated three times, wherein the performances of the silicon carbide crystals comprise thread dislocation TSD density, edge dislocation TED density, surface stress absolute value, crystallization quality, bending Bow, warping Warp Warp, total thickness deviation TTV and local thickness deviation LTV; and cutting, grinding, polishing and other processing the silicon carbide crystal 1# -5# with the nucleation center point 105 being coincident with the crystal center point 103 to obtain the performance test of the silicon carbide seed crystal Z1# -Z5# with the nucleation center point 105 being coincident with the crystal center point 103 and the substrate C1# -C5 #.
It should be noted here that the process of cutting, grinding, polishing, etc. the silicon carbide crystal to obtain the seed crystal or the substrate is prior art and will not be described herein again. In addition, the crystal center point defines the intersection point of the central axis of the silicon carbide crystal and the first main surface 101 and the second main surface 102 as the crystal center point; the relative distance parameters between the tested crystal center point and the nucleation center point are uniformly measured on the first main surface.
As can be seen from Table 2, TSD < 150/cm in the facet ranges of silicon carbide crystal 1# -5#, silicon carbide seed crystal Z1# -Z5#, and substrate C1# -C5# 2 ，TED＜1500/cm 2 TSD < 100/cm outside the facet 2 ，TED＜1000/cm 2 (ii) a The absolute value of the surface stress is less than 15MPa, and the difference value in the plane is less than 20MPa; the crystalline quality is less than 25arcs (arc seconds); bow is less than 5um, warp is less than 10um, TTV is less than 3um, and LTV is less than 1um. The preparation method of the D2# and the silicon carbide crystal 3# is different in that the pressure difference between the upper cavity and the lower cavity is less than 5mbar, and other steps and parameters are the same; the difference of the D3# and the preparation method of the silicon carbide crystal 3# is that the pressure difference of the upper cavity and the lower cavity is more than 25mbar, other steps and parameters are the same, and the performance test results of the D2# and the D3# are both inferior to that of the silicon carbide crystal 1# to 5#, which shows that the too small or too large pressure difference of the upper cavity and the lower cavity can affect the dynamic balance of the pressure in the upper cavity and various gas phase components, further affect the flow field structure constructed by the growth of the silicon carbide single crystal, increase or generate crystal defects caused by air flow disturbance, and further affect the quality of the crystal.
The above description is only an example of the present application, and the protection scope of the present application is not limited by these specific examples, but is defined by the claims of the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the technical idea and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. A silicon carbide crystal having a first major surface and a second major surface opposite the first major surface, wherein the first and/or second major surfaces have a nucleation site, wherein a central axis of the silicon carbide crystal extends through the first and second major surfaces, and wherein the intersection of the central axis with the first and/or second major surfaces is the crystal center;
the distance from the nucleation center point to the crystal center point at the first major surface and/or the second major surface is less than 1/4 of the diameter of the silicon carbide crystal.
2. The silicon carbide crystal of claim 1 wherein the distance from the nucleation center point to the crystal center point is less than 1/5 the diameter of the silicon carbide crystal;
preferably, the distance from the nucleation center point to the crystal center point is less than 1/10 of the diameter of the silicon carbide crystal;
more preferably, the nucleation center coincides with the crystal center point.
3. The silicon carbide crystal of claim 1 wherein the nucleation center is located 0-25mm from the crystal center;
preferably, the distance between the nucleation center point and the crystal center point is 0-20mm.
4. The silicon carbide crystal of claim 1 wherein the first major surface is a {0001} plane.
5. The silicon carbide crystal of claim 4 wherein the nucleation center point is biased toward a <11-20> orientation at the center of the {0001} plane.
6. The silicon carbide crystal of claim 1 wherein the nucleation features are generally circular in shape, the ratio of the diameter of the nucleation features to the silicon carbide crystal diameter is 1/5-2/3, and the ratio of the area of the nucleation features to the area of the first or second major surface is 1/25-4/9;
preferably, the ratio of the diameter of the nucleation features to the silicon carbide crystal diameter is 1/4 to 1/2 and the ratio of the area of the nucleation features to the area of the first or second major surface is 1/16 to 1/4.
7. The silicon carbide crystal of claim 6 wherein the nucleation features have a diameter of 40mm to 220mm, and the silicon carbide crystal has a diameter of 90mm or greater;
preferably, the diameter of the nucleation morphology is 50mm-200mm, and the diameter of the silicon carbide crystal is more than or equal to 100mm.
8. The silicon carbide crystal of claim 1 wherein the TSD of the surrounding crystal region within the nucleation profile is less than 160/cm 2 TED less than 1600/cm 2 (ii) a The TSD of the crystal region outside the nucleation morphology is less than 120/cm 2 TED less than 1100/cm 2 The absolute value of the surface stress of the crystal is less than 18Mpa, the difference value in the nucleation morphology is less than 25Mpa, and the crystallization quality of the crystal is less than 28arcs;
preferably, the TSD of the surrounding crystalline region within the nucleation profile is less than 150/cm 2 TED less than 1500/cm 2 (ii) a The TSD of the crystal region outside the nucleation morphology is less than 100/cm 2 TED less than 1000/cm 2 The absolute value of the surface stress of the crystal is less than 15Mpa, the difference value in the nucleation morphology is less than 20Mpa, and the crystallization quality of the crystal is less than 25arcs.
9. A silicon carbide seed crystal produced by cutting, grinding and polishing a silicon carbide crystal according to any one of claims 1 to 8.
10. A silicon carbide substrate produced by cutting, grinding and polishing a silicon carbide crystal according to any one of claims 1 to 8.
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| CN202211366501.2A CN115652432A (en) | 2022-10-31 | 2022-10-31 | Silicon carbide crystal, seed crystal and substrate |
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| CN202211366501.2A CN115652432A (en) | 2022-10-31 | 2022-10-31 | Silicon carbide crystal, seed crystal and substrate |
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