CN218842406U - Silicon carbide crystal growing device - Google Patents
Silicon carbide crystal growing device Download PDFInfo
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- CN218842406U CN218842406U CN202222893174.8U CN202222893174U CN218842406U CN 218842406 U CN218842406 U CN 218842406U CN 202222893174 U CN202222893174 U CN 202222893174U CN 218842406 U CN218842406 U CN 218842406U
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Abstract
The application discloses carborundum crystal growing apparatus, this growing apparatus includes: a crucible body provided with a growth chamber; the utility model discloses a growth chamber, including growth chamber, a plurality of ventilators, the blow vent is seted up at the lateral wall of growth chamber, and is in the same high department of growth chamber, and the blow vent includes first pair of blow vent and second pair of blow vent, and first pair of blow vent includes A blow vent and A ' blow vent, and A blow vent and A ' blow vent set up about the axis symmetry of growth chamber, and the second is to the distribution of blow vent symmetry in the both sides of first pair of blow vent place straight line to let in the atmosphere of different concentration gradients in the growth chamber along the lateral wall of growth chamber from A blow vent to A ' blow vent. A plurality of air vents are arranged at the same height of the growth chamber, so that the Si atmosphere is gradually reduced from the air vent A to the air vent A', the gradient change of the atmosphere containing C is gradually increased, and the nucleation center is guided to move towards the crystal center.
Description
Technical Field
The application relates to a silicon carbide crystal growth device, and belongs 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 provide 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.
SUMMERY OF THE UTILITY MODEL
In order to solve the problems, the growth device and the preparation method are provided, and the distance between the nucleation centers and the crystal center of the prepared silicon carbide crystal, the seed crystal and the substrate is reduced, the nucleation quality is improved, and the density defect is reduced.
According to one aspect of the present application, there is provided a silicon carbide crystal growing apparatus comprising:
the crucible comprises a crucible body, wherein a growth chamber is arranged in the crucible body;
a plurality of ventilators, the ventilators are seted up the lateral wall of growth chamber, and are in the same high department of growth chamber, the ventilators include first pair of ventilators and second pair of ventilators, first pair of ventilators include A ventilators and A ' ventilators, A ventilators and A ' ventilators about the axis symmetry of growth chamber sets up, the distribution that the second pair of ventilators is symmetrical is in the both sides of first pair of ventilators place straight line to follow A ventilators to A ' ventilators edge the lateral wall of growth chamber to the atmosphere that lets in different concentration gradients in the growth chamber.
The nucleation center of the existing silicon carbide crystal is generally deviated to a certain distance in the <11-20> direction in the crystal center of the silicon carbide crystal in the crystal growing process, for example, at 1/4 of the diameter of the silicon carbide crystal, the growth step information emitted from the nucleation center and the transmission growth distance in the radial direction of the silicon carbide crystal have a large difference, the transmission distance in the <11-20> direction is shortest, the transmission distance in the < -1-120> direction is longest, the crystal center passes through the crystal center in the transmission process in the < -1-120> direction, the crystal center is the 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 of the nucleation center cannot effectively pass through the crystal center, the growth information is lost, mismatched or even mismatched, and the potential hazard to the improvement of the crystal quality is generated. 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).
Optionally, silicon carbide crystal growing apparatus is still including establishing porous separator in the crucible body, in order to incite somebody to action the growth cavity divide into cavity and lower cavity, the blow vent is seted up the lateral wall of last cavity, porous separator can with the atmosphere in the upper cavity is carried to lower cavity.
The growth chamber is divided into an upper chamber and a lower chamber by the porous partition, the vent is arranged on the side wall of the upper chamber, the lower chamber 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 can be effectively and quickly led out, so that the pressure in the upper chamber and the dynamic balance of various gas-phase components are 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 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 enters the lower chamber and then is gradually recrystallized to obtain high-purity silicon carbide powder, so that the raw material is recycled.
Optionally, the top of the upper chamber is provided with a seed crystal placing part, and the A vent or the A' vent is opposite to the <11-20> direction of the seed crystal placing part;
the vent is arranged on the side wall of the upper cavity and close to the seed crystal placing part.
As the nucleation center of the silicon carbide crystal is generally deviated to the <11-20> direction for a certain distance in the crystal center of the silicon carbide crystal, the A 'ventilation port is opposite to the <11-20> direction of the seed crystal placing part, the concentration of the Si-containing atmosphere in the A' ventilation port is the lowest, the concentration of the C-containing atmosphere is the highest, the concentration of the Si-containing atmosphere in the A ventilation port is the highest, and the concentration of the C-containing atmosphere is the lowest, so that the movement of the nucleation center to the crystal center (namely the temperature field center) is more favorably guided.
Optionally, the porous separator is a porous graphite separator plate having a density less than the density of the crucible body;
the porous separator is a porous graphite separation plate, so that gas introduced into the upper chamber can be effectively discharged in time, and meanwhile, a pressure difference formed by the upper chamber and the lower chamber 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 a graphite crucible body, and the density of the porous graphite partition plate is smaller than that of the crucible body, so that the unreacted atmosphere in the upper cavity enters the lower cavity and then is gradually recrystallized to obtain high-purity silicon carbide powder, and the raw material recycling is realized.
Preferably, the porous graphite separator has a density of 0.2 to 1.5g/cm 3 ；
Preferably, the porous graphite separator has a density of 0.3 to 1.3g/cm 3 (ii) a Further, porous graphiteThe upper limit of the density of the separator is selected from 0.3g/cm 3 、0.4g/cm 3 、0.5g/cm 3 、0.6g/cm 3 、0.7g/cm 3 、0.8g/cm 3 0.9, 1.0, the lower limit is selected from 1.0g/cm 3 、1.1g/cm 3 、1.2g/cm 3 、1.3g/cm 3 、1.4g/cm 3 。
Optionally, 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;
preferably, the number of the second pair of vents is 1 pair, 3 pairs, 5 pairs or 7 pairs;
for convenience of understanding, taking the number of the second pair of vents as an example, the vents from the vent a are labeled as vent # 1 to vent # 8 in sequence, the vent a is vent # 1, the 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 alkane gas comprises methane and/or ethane, the silane gas comprises silane and/or disilane, and the volume ratio of the alkane gas to the silane gas introduced from the vent # 3 and the vent # 7 is 1: the volume ratio of alkane gas to silane gas introduced into the 1,2# and 8# vents is 1: the volume ratio of alkane gas and silane gas introduced into the vents of No. 3,4 and No. 6 is 3: silane gas is completely introduced into the 1,1# air hole, alkane gas is completely introduced into the 5# air hole, and then gradient change that Si atmosphere is gradually reduced and C-containing atmosphere is gradually increased from the A air hole to the A' air hole is constructed.
Optionally, the silicon carbide crystal growing apparatus further comprises a porous graphite table, and the lower chamber is enclosed by the porous graphite table, the crucible side wall and a porous partition;
the density of the porous graphite stage is less than that of the crucible body.
The density of porous graphite platform is less than the density of the crucible body, thereby can avoid entering the atmosphere of cavity down and get into the heat preservation that the lateral wall of the graphite crucible body of graphite precipitates the silicon carbide grain and causes the erosion to the crucible body and prolong the heat preservation life-span, play the effect of cost reduction increase.
Preferably, the porous graphite stage has an upper density limit selected from 0.3g/cm 3 、0.4g/cm 3 、0.5g/cm 3 、0.6g/cm 3 、0.7g/cm 3 、0.8g/cm 3 、0.9g/cm 3 、1.0g/cm 3 The lower limit is selected from 1.0g/cm 3 、1.1g/cm 3 、1.2g/cm 3 、1.3g/cm 3 、1.4g/cm 3 。
As an implementation mode, the diameter of the upper chamber is 100-300mm, the height of the upper chamber 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 is 150-500mm, the distance from the top of the porous graphite table to the bottom of the porous partition is 30-100mm, and the temperature change amount of the lower chamber from top to bottom is 0.1-10 ℃/mm, so as to ensure that the silicon carbide powder is fully recrystallized.
Optionally, the porous graphite table is in the shape of a hollow boss, and the top of the porous graphite table extends towards the porous separator;
a graphite connecting cylinder is arranged at the hollow part of the porous graphite table, and one end of the graphite connecting cylinder extends in the direction far away from the lower chamber;
preferably, the porous graphite stage is selected from one of a circular truncated cone shape, a conical shape, and a cylindrical shape, but is not limited to these shapes.
The graphite connecting cylinder is connected with the gas treatment device through the graphite guide pipe, and the gas treatment device absorbs redundant atmosphere, so that the corrosion of the heat insulation structure of the crucible body caused by the atmosphere is avoided.
Preferably, the graphite connector barrel has a density less than that of the crucible body;
preferably, the graphite connector barrel has a density no greater than the density of the porous graphite stage.
The density of the graphite connecting cylinder is 0.2-1.5g/cm 3 (ii) a Preferably, the graphite connecting cylinder has a density of 0.3 to 1.3g/cm 3 。
The density of graphite connecting cylinder is less than the density of the crucible body, is not more than the density of porous graphite platform, thereby can avoid the atmosphere that gets into down the cavity and get into the lateral wall precipitation silicon carbide grain of the graphite crucible body and cause the erosion to the heat preservation of the crucible body and prolong the heat preservation life.
Benefits of the present application include, but are not limited to:
1. according to the silicon carbide crystal growth device, the plurality of vent holes are formed in the same height of the growth cavity, so that Si atmosphere is gradually reduced from the A vent hole to the A' vent hole, the gradually increased gradient change of the C-containing atmosphere is established, the nucleation center is guided to move towards the crystal center (namely, the temperature field center), and the silicon carbide crystal prepared by the growth device is high in nucleation quality and low in density defect.
2. According to the silicon carbide crystal growing device, the porous partition part divides the growing chamber into the upper chamber and the lower chamber, the vent hole is formed in the side wall of the upper chamber, the lower chamber can be provided with different temperature change gradients, the air permeability of the porous partition part is added, the atmosphere introduced into the upper chamber can be effectively and quickly led out, 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 can also be used as a raw material recrystallization recovery area, a certain temperature gradient difference is constructed, the unreacted atmosphere of the upper chamber enters the lower chamber and then is recrystallized gradually to obtain high-purity silicon carbide powder, and the raw material recycling is realized. The porous partition is a porous graphite partition plate, so that gas introduced into the upper chamber can be effectively discharged in time, and meanwhile, a pressure difference formed by the upper chamber and the lower chamber 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 the graphite alkene crucible body usually, and the density of porous graphite division board is less than the density of the crucible body, makes the atmosphere of cavity unreacted of epicoele get into down the cavity after recrystallization gradually and obtain high-purity carborundum powder, realizes raw materials reuse.
3. The distance between the nucleation center (namely the facet center) and the crystal center is 0-20mm, and the distance value between the two centers is less than 1/10 of the crystal diameter; the facet diameter of the silicon carbide crystal is 50-200mm, the crystal diameter is not less than 100mm, and the facet is straightThe diameter is 1/4-1/2 of the crystal diameter, and the facet area is 1/16-1/4 of the crystal main surface area; the silicon carbide crystal, a substrate prepared from the silicon carbide crystal and TSD in the range of seed crystal facet is less than 150/cm 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.
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.
Figure 2 is a top view of an apparatus for growing a silicon carbide crystal according to an embodiment 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.
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 platform, 7 a graphite connecting cylinder, 8 a cover body,
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.
This embodiment provides a silicon carbide crystal growth device, with the silicon carbide crystal that is used for producing the distance of nucleation central point and crystal central point little or the coincidence, refer to fig. 1-3, this silicon carbide crystal growth device includes 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 at the lateral wall of growth chamber 2 is established to the blow vent, the blow vent includes a pair of blow vent, a pair of blow vent includes A blow vent and A 'blow vent, A blow vent and A' blow vent are symmetrical about the axis of growth chamber 2 and are set up, the bilateral symmetry of A blow vent and A 'blow vent place straight line is equipped with the second and is right to the blow vent, with the atmosphere of different concentration gradients lets 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 is generally deviated to a certain distance in the <11-20> direction in the crystal center of the silicon carbide crystal in the crystal growing process, for example, at 1/4 of the diameter of the silicon carbide crystal, the growth step information emitted from the nucleation center and the transmission growth distance in the radial direction of the silicon carbide crystal have a large difference, the transmission distance in the <11-20> direction is shortest, the transmission distance in the < -1-120> direction is longest, the crystal center passes through the crystal center in the transmission process in the < -1-120> direction, the crystal center is the 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 of the nucleation center cannot effectively pass through the crystal center, the growth information is lost, mismatched or even mismatched, and the potential hazard to the improvement of the crystal quality is generated. Therefore, a plurality of air vents are formed at the same height of the growth chamber, so that Si atmosphere is gradually reduced from the air vent A to the air vent A', the gradient change of the atmosphere containing C is gradually increased, and the nucleation center is guided to move to the crystal center (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 vents of No. 1,2 and No. 8 is 1: the volume ratio of alkane gas and silane gas introduced into the vents of No. 3,4 and No. 6 is 3: silane gas is completely introduced into the 1,1# vent, alkane gas is completely introduced into the 5# vent, and the gradient change that Si gas is gradually reduced and C-containing gas 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 part 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 the graphite crucible body usually, and the density of porous graphite division board 4 is less than the density of the graphite crucible body, makes the gaseous recrystallization gradually after getting into cavity 22 down of last cavity 21 unreacted obtain the carborundum powder of high-purity, realizes raw materials reuse.
In a specific 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 opposite to the <11-20> direction of the seed crystal placing part 3 (also the <11-20> direction of the seed crystal); the vent is opened at a position close to the seed crystal placement section 3 on the side wall of the upper chamber 21. Since the nucleation center of the silicon carbide crystal is generally deviated to the <11-20> direction for a certain distance in the crystal center of the silicon carbide crystal, the A 'vent is opposite to the <11-20> direction of the seed crystal placing part 3, the Si-containing atmosphere of the A' vent has the lowest concentration, the C-containing atmosphere has the highest concentration, the Si-containing atmosphere of the A vent has the lowest concentration, and the C-containing atmosphere has the lowest concentration, so that the nucleation center is more favorably guided 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 partition, and the porous graphite stage 6 has one shape selected from a circular truncated cone shape, a conical cone 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, and thereby the atmosphere that can avoid entering lower cavity 22 enters the lateral wall of the graphite crucible body and separates 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 change 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 vents of No. 1,2 and No. 8 is 1: the volume ratio of alkane gas and silane gas introduced into the vents of No. 3,4 and No. 6 is 3: silane gas is completely introduced into the 1,1# air hole, alkane gas is completely introduced into the 5# air hole, and then gradient change that Si atmosphere is gradually reduced and C-containing atmosphere is gradually increased from the A air hole to the A' air hole is constructed.
3. A 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 a second temperature of 2000-2500 ℃, 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 is generally deviated from the center in the <11-20> direction 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 <11-20> direction is shortest, the transmission distance in the < -1-120> direction is longest, the transmission distance in the < -1-120> direction passes through the crystal center in the < -1-120> direction, the crystal center is the center of a thermal field, 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, even mismatched, and great hidden danger is caused for 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 towards the crystal center, so that the nucleation center is close to the crystal center and even coincides with the crystal center, and the transmission growth distances of the growth information of 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 step 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 crystals 1# -5# according to the above preparation method, the parameters associated with comparative silicon carbide crystals D1# -D3#, and the parameters associated with the distance between the nucleation center and the crystal center 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 features, the nucleation features are substantially circular, and the diameters of the facets are the diameters of the nucleation features.
As can be seen from the above table 1, in the silicon carbide crystal 1# -5# prepared by the silicon carbide crystal growth device and the preparation method of the present application, the distance between the nucleation center point (i.e., the facet center) and the crystal center point is controlled within the range of 0-20mm, and the distance between the two centers is less than 1/10 of the crystal diameter; the facet diameter of the silicon carbide crystal is 50-200mm, the diameter of the silicon carbide crystal is more than or equal to 100mm, the facet diameter is 1/4-1/2 of the diameter of the silicon carbide crystal, and the facet area is 1/16-1/4 of the area of the main surface of the crystal. 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 and the crystal center point 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 silicon carbide crystal D1#, the nucleation center point of the silicon carbide crystal has a certain distance with the crystal center point and exceeds 30mm, which shows that 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 the like the silicon carbide crystal 1# -5# with the nucleation center point coincident with the crystal center point to obtain the performance test of the silicon carbide seed crystal Z1# -Z5# with the nucleation center point coincident with the crystal center point 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 substrate is prior art and will not be described herein. In addition, the crystal center point defines the intersection point of the central axis of the silicon carbide crystal and the first main surface and the second main surface 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.
Reference in this application to a crystal center 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 center of the thermal field, i.e., the radial temperature nadir.
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. That is, the closer the distance between the nucleation center and the crystal center is, the higher the coincidence degree between the crystal center and the nucleation center is, and the higher the quality of the silicon carbide crystal is.
As can be seen from Table 2, carbonizationTSD < 150/cm in the facet range of the silicon crystal 1# -5#, the silicon carbide seed crystal Z1# -Z5# and the 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 preparation method of the D3# and the silicon carbide crystal 3# is that the pressure difference between 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# -5#, which indicates that the too small or too large pressure difference between 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 (12)
1. An apparatus for growing a silicon carbide crystal, comprising:
the crucible comprises a crucible body, wherein a growth chamber is arranged in the crucible body;
a plurality of ventilators, the ventilators are seted up the lateral wall of growth chamber, and are in the same high department of growth chamber, the ventilators include first pair of ventilators and second pair of ventilators, first pair of ventilators include A ventilators and A ' ventilators, A ventilators and A ' ventilators about the axis symmetry of growth chamber sets up, the distribution that the second pair of ventilators is symmetrical is in the both sides of first pair of ventilators place straight line to follow A ventilators to A ' ventilators edge the lateral wall of growth chamber to the atmosphere that lets in different concentration gradients in the growth chamber.
2. The silicon carbide crystal growth apparatus of claim 1 further comprising a porous partition disposed within the crucible body to divide the growth chamber into an upper chamber and a lower chamber, the vent opening in a sidewall of the upper chamber, the porous partition capable of delivering an atmosphere within the upper chamber to the lower chamber.
3. The silicon carbide crystal growing apparatus of claim 2 wherein the top of the upper chamber has a seed placement portion, the a or a' vents being aligned with the <11-20> direction of the seed placement portion;
the vent is arranged on the side wall of the upper cavity and close to the seed crystal placing part.
4. A silicon carbide crystal growth apparatus according to claim 2 wherein the porous partition is a porous graphite partition plate having a density less than the density of the crucible body.
5. The silicon carbide crystal growth apparatus of claim 4 wherein the porous graphite separator plate has a density of 0.2-1.5g/cm 3 。
6. The silicon carbide crystal growth apparatus of claim 1 wherein the second pair of aeration ports is an odd number of pairs evenly distributed on either side of a line along which the first pair of aeration ports is located.
7. The silicon carbide crystal growth apparatus of claim 2 further comprising a porous graphite table, the lower chamber being enclosed by the porous graphite table, the crucible body sidewalls and a porous divider;
the density of the porous graphite stage is less than that of the crucible body.
8. The silicon carbide crystal growth apparatus of claim 7 wherein the porous graphite stage is in the form of a hollow boss with a top of the porous graphite stage extending toward the porous partition;
the hollow part of the porous graphite table is provided with a graphite connecting cylinder, and one end of the graphite connecting cylinder extends towards the direction far away from the lower chamber.
9. The silicon carbide crystal growing apparatus of claim 8 wherein the silicon carbide crystal growing apparatus,
the density of the graphite connecting cylinder is less than that of the crucible body;
the density of the graphite connecting cylinder is not more than that of the porous graphite table.
10. The silicon carbide crystal growth apparatus of claim 7 wherein the porous graphite stage is selected from one of a truncated cone, a cone, and a cylinder.
11. A silicon carbide crystal growing apparatus according to claim 2 wherein the upper chamber has a diameter of 100-300mm and a height of 150-500mm.
12. The silicon carbide crystal growth apparatus of claim 7 wherein the lower chamber has a height of 150-500mm and the distance from the top of the porous graphite table to the bottom of the porous partition is 30-100mm.
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