CN116163009A - Method for growing silicon carbide single crystal - Google Patents
Method for growing silicon carbide single crystal Download PDFInfo
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- CN116163009A CN116163009A CN202111403566.5A CN202111403566A CN116163009A CN 116163009 A CN116163009 A CN 116163009A CN 202111403566 A CN202111403566 A CN 202111403566A CN 116163009 A CN116163009 A CN 116163009A
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
- C30B23/02—Epitaxial-layer growth
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
- C30B23/002—Controlling or regulating
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/36—Carbides
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
- C30B33/02—Heat treatment
Abstract
The present invention provides a method for growing a silicon carbide single crystal, comprising the steps of: (1) Assembling the feedstock into an apparatus for single crystal growth of silicon carbide; (2) Placing the device in an induction coil in a single crystal growth furnace; (3) Then, a first protective gas is adopted for washing the furnace, and the vacuum degree of the growth furnace is controlled; (4) Then, in the presence of a second protective gas, silicon carbide single crystal growth is performed by controlling the pressure and temperature in the apparatus; (5) Annealing the device after the growth of the silicon carbide single crystal is completed; and cooling the device to room temperature to obtain the silicon carbide single crystal. The method of the present invention can grow SiC single crystals of large size, such as 8 inches or more. The method of the invention can increase the utilization rate of the raw materials in the growth of SiC crystals, reduce the consumption of the raw materials in the growth of SiC single crystals and reduce the growth cost.
Description
Technical Field
The invention belongs to the field of crystal growth. In particular, the present invention relates to a method of growing a silicon carbide single crystal.
Background
Silicon carbide (SiC) has wide band gap, high thermal conductivity, high electron mobility, high breakdown field strength, good thermal stability and good chemical stability, is an ideal material for preparing high-temperature, high-frequency, high-power and radio-frequency devices, and has wide application prospect in the fields of new energy electric automobiles, rail transit, high-voltage power transmission and transformation, communication base stations and the like.
The large-size SiC single crystal, high raw material utilization rate and high growth rate can obviously reduce the cost of SiC devices.
Physical Vapor Transport (PVT) is the main method for growing large-size SiC single crystals, 6 inch SiC single crystals have been grown at present, and industrialization has been achieved. However, there is currently no commercialized 8 inch SiC single crystal and 8 inch SiC single crystal growth technology.
Aiming at the problem of large-size SiC single crystal growth, CN 113151895A realizes the growth of large-diameter silicon carbide single crystals by adopting a conical crucible cover structure and a double heating device. However, the silicon carbide single crystal grown by the method cannot realize the growth of a large-diameter silicon carbide constant diameter region, and it is difficult to realize the processing of a single crystal wafer. In addition, this patent application needs to adopt two heating device to realize the effective supply of raw materials, and the upper surface of raw materials owing to having covered the raw materials, along with the growth, the raw materials can sinter gradually together, can not provide effectual transmission path for the gaseous phase material that the growth needs to reduce the utilization ratio of raw and other materials, reduced growth rate.
There is an urgent need for a method capable of growing large-sized SiC single crystals, particularly 8 inches.
Disclosure of Invention
The present invention aims to provide a method capable of growing large-size SiC single crystals.
The above object of the present invention is achieved by the following technical solutions.
The present invention provides a method for growing a silicon carbide single crystal, comprising the steps of:
(1) Assembling the feedstock into an apparatus for single crystal growth of silicon carbide;
(2) Placing the device in an induction coil of a single crystal growth furnace;
(3) Then, a first protective gas is adopted for washing the furnace, and the vacuum degree of the growth furnace is controlled;
(4) Then, in the presence of a second protective gas, silicon carbide single crystal growth is performed by controlling the pressure and temperature in the apparatus;
(5) Annealing the device after the growth of the silicon carbide single crystal is completed; cooling the device to room temperature to obtain a silicon carbide single crystal;
the device comprises a graphite crucible main body, a graphite crucible cover and seed crystals, wherein the seed crystals are fixed on the inner side of the graphite crucible cover; the apparatus further comprises a graphite ring positioned between the graphite crucible body and the graphite crucible cover;
the graphite ring is comprised of an expanded diameter section proximate to the graphite crucible cover and an equal diameter section distal from the graphite crucible cover, wherein the reduced diameter expanded diameter section has an inclined face inclined relative to the seed crystal and the inclined face extends toward the seed crystal in at least alignment with a peripheral edge of the seed crystal.
The inventors of the present application have unexpectedly found that when the graphite ring of the present invention is provided between the graphite crucible main body and the graphite crucible cover, a large-sized silicon carbide single crystal can be obtained. Without wishing to be bound by theory, this may be due to the fact that the graphite ring of the present invention has an expanded diameter section that can allow the vapor phase species of SiC to be transported as far as possible toward the central seed crystal by means of physical confinement, thereby reducing the likelihood of spontaneous nucleation of supersaturated vapor phase species on the graphite baffle to form polycrystalline regions; meanwhile, the baffle plate of the crucible is provided with a section of constant diameter part, so that the constant diameter growth of the large-size SiC crystal after the diameter expansion can be realized, and the difficulty of later crystal processing is reduced.
Preferably, in the method of the present invention, the inclined surface is inclined at an angle of 30 to 89 ° with respect to the radial direction of the graphite crucible body (refer to angle θ in fig. 2).
The inventors of the present application have unexpectedly found that when the inclination angle of the inclined surface with respect to the radial direction of the graphite crucible main body is 30 to 89 °, a silicon carbide single crystal of a larger size can be obtained which is more effective. Too large an angle affects the expansion efficiency, too small an angle tends to form polycrystalline regions at the edges of the growing crystal, eroding the growing crystal.
Preferably, in the method of the present invention, the constant diameter section has the same inner diameter as the graphite crucible main body.
Preferably, in the method of the present invention, the inclined surface extends toward the seed crystal to cover a periphery of the seed crystal by 10 to 30mm. Since more defects often exist at the edge of the seed crystal, the graphite ring covers the defects at the edge of the seed crystal in the growth process, so that the quality of the grown crystal can be improved.
Preferably, in the method of the present invention, the apparatus further comprises at least one graphite sleeve located within the graphite crucible body to divide the graphite crucible body into a raw material region surrounded by the graphite sleeve and the graphite crucible body and a non-raw material region surrounded by the graphite sleeve interior;
the side wall of the graphite sleeve is provided with a through hole, and the extending direction of the through hole forms an acute angle with the axis of the graphite sleeve so as to prevent raw materials in the raw material area from entering the non-raw material area.
In the method of the present invention, the device may further comprise a graphite sleeve as described above. The graphite sleeve can increase the utilization rate of raw materials, increase the growth speed and further reduce the cost of SiC single crystals. During the growth of SiC crystals by PVT, atmospheric species are typically transported to the SiC seed crystal through the interstices between the SiC particles and the gaps between the feedstock and the graphite crucible. Along with the growth, the raw material particles can sinter together, so that the transportation of gas-phase substances is blocked, and the utilization rate of raw materials is reduced. In addition, as the size of the grown crystal increases, the difficulty in transporting the gas phase material from the crucible edge to the center of the seed crystal through the gap between the graphite crucible and the raw material increases, resulting in a decrease in the crystal growth rate and a decrease in the quality of the grown crystal. The increase in crystal size also increases the stress within the grown SiC crystal. Low utilization of raw materials, low growth rate, uneven transport of gas phase substances, result in an increase in SiC crystal cost and a decrease in crystal quality. The device of the present invention further comprising a graphite sleeve solves the above mentioned problems.
Preferably, in the method of the present invention, the first protective gas and the second protective gas are each independently selected from one or more of argon, hydrogen, and nitrogen.
Preferably, in the method of the present invention, the first protective gas is argon.
Preferably, in the method of the present invention, the second protective gas is argon and hydrogen.
Preferably, in the method of the present invention, the volume ratio of the hydrogen gas to the argon gas is 1 (5-1).
Preferably, in the method of the present invention, the second protective gas is argon and nitrogen.
Preferably, in the method of the present invention, the volume ratio of the nitrogen gas to the argon gas is 1 (5-1).
Preferably, in the method of the present invention, the vacuum degree in the step (3) is 10 or less -3 Pa。
Preferably, in the method of the present invention, the controlling of the pressure and temperature in the apparatus in the step (4) is performed under the following conditions:
the pressure at the time of growth of the silicon carbide single crystal is controlled to 100Pa to 9.8kPa, and the temperature at the time of growth of the silicon carbide single crystal is controlled to 2000 to 2400 ℃.
Preferably, in the method of the present invention, the annealing in the step (5) is performed in a method comprising the steps of:
cooling the device to 400-1000 ℃ at a speed of 10-800 ℃/h, and keeping for 1-10h.
Preferably, in the method of the present invention, the height of the graphite sleeve is 20-70% of the distance of the seed crystal from the bottom wall of the graphite crucible body.
Preferably, in the method of the present invention, the sum of the bottom areas of the graphite sleeves is 10-70% of the bottom area of the graphite crucible body.
Preferably, in the method of the present invention, the thickness of the wall of the graphite sleeve is 5-80mm.
Preferably, in the method of the present invention, the inner diameter of the graphite sleeve is 20% -100% of the maximum dimension of the seed crystal.
Preferably, in the method of the present invention, the inner diameter of the upper top surface of the graphite sleeve is 20-80% of the inner diameter of the lower bottom surface.
Preferably, in the method of the present invention, the outer diameter of the upper top surface of the graphite sleeve is 20-80% of the outer diameter of the lower bottom surface.
Preferably, in the method of the present invention, the graphite sleeve is a cylindrical sleeve, a conical sleeve or a frustoconical sleeve.
Preferably, in the method of the present invention, the outer diameter of the cylindrical sleeve is 1.1 to 5.5 times the inner diameter of the cylindrical sleeve.
Preferably, in the method of the present invention, the inner diameter of the cylindrical sleeve is 10-200mm.
Preferably, in the method of the present invention, the outer diameter of the cylindrical sleeve is 20-220mm.
Preferably, in the method of the present invention, an outer diameter of an upper top surface of the conical sleeve is the same as an inner diameter of the graphite crucible body.
Preferably, in the method of the present invention, the minimum distance between the through hole and the upper top surface of the graphite sleeve is 5-40% of the height of the graphite sleeve.
Preferably, in the method of the present invention, the minimum distance between the through hole and the upper top surface of the graphite sleeve is 10-100mm.
Preferably, in the method of the present invention, the minimum distance between the through hole and the lower bottom surface of the graphite sleeve is 10-100mm.
Preferably, in the method according to the invention, the distance between two adjacent through holes is 5-100mm.
Preferably, in the method of the present invention, the diameter of the through hole is 5-30mm.
Preferably, in the method of the present invention, the axis of the graphite sleeve overlaps with the axis of the graphite crucible main body.
In a specific embodiment of the present invention, the starting material required for growing SiC is preferably SiC, or Si, C, or SiC, si, C, or Si, C, V-containing species, or SiC, V-containing species;
in a specific embodiment of the present invention, the height of the feedstock filled in the graphite crucible (i.e., feedstock zone) outside the graphite sleeve is consistent with the graphite sleeve or is 1-5mm below the graphite sleeve;
in particular embodiments of the present invention, a barrier cover, such as a graphite sheet, may be employed to shield the top of the graphite sleeve as the feedstock is added to the feedstock zone in order to prevent the feedstock from falling into the graphite sleeve; when growing the single crystal, the blocking cover is removed.
In particular embodiments of the present invention, the graphite sleeve may be placed at any desired location in the graphite crucible, either centrally in the graphite crucible or offset to any side of the graphite crucible.
In a specific embodiment of the present invention, the side wall of the graphite sleeve needs to be perforated, and the number of through holes is preferably more than 2.
In a specific embodiment of the present invention, the growth process of a silicon carbide single crystal includes the steps of:
placing a plurality of graphite sleeves with through holes on the side walls into a graphite crucible; filling raw materials required by growth into a graphite crucible outside a graphite sleeve; adhering SiC seed crystal on the bottom cover of the crucible cover, screwing a graphite ring, and assembling the SiC seed crystal with the graphite crucible main body; and placing the graphite crucible tool loaded with the graphite sleeve and the growth raw materials in silicon carbide crystal growth equipment to grow the silicon carbide crystal.
In a specific embodiment of the present invention, a graphite sleeve is used (as shown in fig. 3) having a sidewall thickness at the lower bottom surface that is greater than the sidewall thickness at the upper bottom surface. Compared with a cylindrical sleeve with the same inner diameter, the thickness of the side wall at the lower bottom surface has better heat preservation effect, so that the temperature inside the graphite sleeve is increased, the temperature gradient is increased, the utilization rate of SiC raw materials can be further improved, and the crystal growth amount is increased.
In a specific embodiment of the present invention, a conical graphite sleeve is used in the present invention, the outer diameter of the upper bottom surface of which is the same as the inner diameter of the graphite crucible (as shown in fig. 4). The silicon carbide feedstock in the feedstock zone will decompose at high temperatures to compounds containing Si and C, as the SiC feedstock does not decompose according to Si: c=1:1, resulting in some graphitization of the feedstock to form graphite particles that remain in the crucible. These graphite particles may then be carried into the growing crystal by vapor phase species generated by SiC decomposition, which can affect the crystal quality. The conical graphite sleeve (shown in figure 4) can prevent graphite particles from being transmitted into SiC crystals, so that the crystal quality is improved.
In a specific embodiment of the present invention, a large-sized SiC single crystal may be grown by a method including the steps of: uniformly placing a graphite sleeve with through holes on the side wall in a graphite crucible main body, loading raw material particles for growing silicon carbide crystals into a graphite crucible outside the graphite sleeve, and assembling a graphite crucible cover with silicon carbide seed crystals with the graphite crucible; placing the graphite crucible which is well assembled into a silicon carbide crystal growth furnace; pumping air from the silicon carbide crystal growth furnace, and filling a first protective gas, and repeating for 3-5 times; charging a second protective gas of 10kPa-90kPa into a silicon carbide crystal growth furnace, and heating the graphite crucible to 2000-2400 ℃; reducing the pressure in the growth system to 100Pa-9.8kPa, starting to grow silicon carbide crystals, wherein the temperature rising rate of the graphite crucible in the crystal growth process is 0.8-1.2 ℃/h, and the pressure reducing rate is as follows: 0.5Pa-2Pa/h; stopping heating when the growth of the silicon carbide crystal is completed; and cooling the crystal to room temperature to obtain the large-size silicon carbide single crystal.
In particular embodiments of the invention, the SiC seed crystal preferably has a diameter of 150-180mm, and may be semi-insulating or conductive.
In a specific embodiment of the invention, the SiC seed crystal is affixed to the bottom cover of the crucible cover in a size that is 10-50mm smaller than the size of the desired grown SiC crystal.
In a particular embodiment of the invention, the second protective gas may be high purity Ar, N 2 、Ar/N 2 Mixed gas or Ar/H 2 And (3) mixing the gases.
In a specific embodiment of the invention, the single crystal growth time is 60 to 300 hours, preferably 60 to 200 hours.
The invention has the following beneficial effects:
(1) The method of the present invention can grow SiC single crystals of large size, such as 8 inches or more.
(2) The method of the invention can increase the utilization rate of the raw materials in the growth of SiC crystals, reduce the consumption of the raw materials in the growth of SiC single crystals and reduce the growth cost. The method can provide sufficient and stable gas phase substances for SiC crystal growth, increase the utilization rate of raw materials and improve the crystal quality of the grown SiC single crystal.
(3) The annealing process in the method can effectively reduce the stress in the SiC single crystal, is simple to operate and easy to implement, and solves the problem of the stress in the growth process of the large-size SiC single crystal.
(4) The method can obtain the high-purity semi-insulating large-size SiC single crystal substrate and also can obtain the n-type large-size SiC single crystal substrate.
Drawings
Embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein:
FIG. 1 is a schematic cross-sectional view of an apparatus for growing a silicon carbide single crystal in one embodiment of the invention;
FIG. 2 is a schematic cross-sectional view of a graphite crucible cover in an apparatus for growing a silicon carbide single crystal in which θ is an inclined surface angle, in one embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of an apparatus for single crystal growth of silicon carbide in which 1 frustoconical graphite sleeve is disposed within a graphite crucible body in one embodiment of the present invention;
FIG. 4 is a schematic cross-sectional view of an apparatus for single crystal growth of silicon carbide in which 1 conical graphite sleeve is disposed within a graphite crucible body in one embodiment of the present invention;
FIG. 5 is a schematic cross-sectional view of an apparatus for growing a silicon carbide single crystal in which 2 cylindrical graphite sleeves are provided in a graphite crucible body in one embodiment of the present invention;
FIG. 6 is a pictorial view of a grown SiC single crystal ingot in one embodiment of the invention;
wherein, the reference numerals:
1-an induction coil; 2-seed crystal; 3-graphite crucible cover; 4-graphite ring; 41-an expanded diameter section; 411-inclined plane; 42-isodiametric section; 5-a feedstock zone; 6-graphite sleeve; 61-through holes; 7-a graphite crucible body; 8-non-feed zone.
Detailed Description
Referring now to the drawings, illustrative aspects of the disclosed apparatus for silicon carbide crystal growth are described in detail. Although the drawings are provided to present some embodiments of the invention, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present disclosure. The position of part of components in the drawings can be adjusted according to actual requirements on the premise of not affecting the technical effect. The appearances of the phrase "in the drawings" or similar language in the specification do not necessarily refer to all figures or examples.
It should be noted that certain directional terms used hereinafter to describe the drawings, such as "transverse", "vertical", "front", "rear", "inner", "outer", "above", "below" and other directional terms, will be understood to have their ordinary meaning and refer to those directions as they would normally be referred to in viewing the drawings. Unless otherwise indicated, directional terms described herein are generally in accordance with conventional directions as understood by those skilled in the art.
Some embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following embodiments and features of the embodiments may be combined with each other without conflict.
In the method of the present invention, the apparatus used in growing silicon carbide crystals of the present invention may be referred to in FIGS. 1 to 5, and comprises a graphite crucible body 7, a graphite crucible cover 3, and a seed crystal 2, the seed crystal 2 being fixed inside the graphite crucible cover 3; wherein the device further comprises a graphite ring 4 positioned between the graphite crucible body 7 and the graphite crucible cover 3;
the graphite ring 4 is constituted by an enlarged diameter section 41 close to the graphite crucible cover 3 and an equal diameter section 42 distant from the graphite crucible cover 3, wherein the enlarged diameter section 41 has an inclined face 411 inclined with respect to the seed crystal 2 and the inclined face 411 extends toward the seed crystal 2 to be at least aligned with the peripheral edge of the seed crystal 2. Further, the inclination angle of the inclined surface 411 with respect to the radial direction of the graphite crucible body 7 may be 30 to 89 °, such as 30 °, 40 °, 50 °, 65 °, or 80 °.
Further, the inner diameter of the constant diameter section 42 is the same as the inner diameter of the graphite crucible body 7.
Further, the inclined surface 411 extends toward the seed crystal 2 to cover the periphery of the seed crystal 2 by 10 to 30mm, such as 15mm, 20mm or 25mm.
In an embodiment of the present invention, the apparatus of the present invention further comprises at least one graphite sleeve 6 (refer to fig. 1-5) located within the graphite crucible body 7 to divide the graphite crucible body 7 into a raw material zone 5 surrounded by the graphite sleeve 6 and the graphite crucible body 7 and a non-raw material zone 8 surrounded by the interior of the graphite sleeve 6. Of course, in other embodiments, more than one graphite sleeve 6 may be provided, such as 2 graphite sleeves 6 (see fig. 5). The side walls of the graphite sleeve 6 are provided with through holes 61, the direction of extension of the through holes 61 being at an acute angle, such as 30 °, 60 ° or 70 °, to the axis of the graphite sleeve to prevent the feedstock in the feedstock zone 5 from entering the non-feedstock zone 8. The height of the graphite sleeve 6 is 20-70%, such as 30%, 40%, 50% or 60%, of the distance of the seed crystal 2 from the bottom wall of the graphite crucible body 7. For example, the graphite sleeve 6 may have a height of 120mm. The distance of the seed crystal 2 from the bottom wall of the graphite crucible body 7 may be 180mm. The bottom area of the graphite sleeve 6 is 10-70%, such as 40%, 50%, 60% of the bottom area of the graphite crucible body. The thickness of the wall of the graphite sleeve 6 is 5-80mm. The inner diameter of the graphite sleeve 6 is 20% -100%, such as 50%, 60%, 70% of the maximum dimension of the seed crystal.
The minimum distance of the through holes 61 from the upper top surface of the graphite sleeve 6 is 5-40%, such as 10%, 20% or 30% of the height of the graphite sleeve 6; for example, the minimum distance of the through hole 61 from the upper top surface of the graphite sleeve 6 is 50mm; the minimum distance between the through hole 61 and the lower bottom surface of the graphite sleeve 6 is 40mm; the distance between two adjacent through holes is 5-100mm, such as 50mm. The diameter of the through hole 61 is 5-30mm, such as 20mm. In a specific embodiment, the axis of the graphite sleeve 6 may overlap with the axis of the graphite crucible body 7, i.e., the graphite sleeve 6 is placed at the center position of the graphite crucible body 7 (refer to fig. 1, 3-4).
The graphite sleeve 6 may be a cylindrical sleeve (refer to fig. 1 and 5), a conical sleeve (refer to fig. 4), or a frustoconical sleeve (refer to fig. 3). The outer diameter of the cylindrical sleeve is 1.1-5.5 times, such as 2 times, 3 times, 4 times and 5 times, the inner diameter of the cylindrical sleeve; for example, the inner diameter of the cylindrical sleeve is 180mm; the outer diameter of the cylindrical sleeve was 200mm.
In a particular embodiment, the graphite sleeve 6 may be a frustoconical sleeve (see fig. 3) with a wall thickness that tapers from bottom to top. The inner diameter of the upper top surface of the graphite sleeve 6 is 20-80% of the inner diameter of the lower bottom surface; the outer diameter of the upper top surface of the graphite sleeve 6 is 20-80% of the outer diameter of the lower bottom surface.
In one embodiment, the upper top surface of the conical sleeve has the same outer diameter as the inner diameter of the graphite crucible body 7 (see fig. 4).
Example 1
The method for growing large-size SiC single crystal using the apparatus shown in fig. 1 of the present invention includes the steps of:
6 inch commercial 4H-SiC was used as a seed crystal and the C-plane was used as the crystal growth plane. The seed crystal was bonded to the inside of the graphite crucible cover. And filling enough SiC powder raw materials outside a graphite sleeve of the graphite crucible main body, placing a graphite crucible cover adhered with seed crystals on the upper part of the graphite crucible, and placing the graphite crucible cover into an induction coil in a single crystal growth furnace after assembly.
Vacuumizing the single crystal furnace until the pressure is less than 10 percent -3 Pa, then the following procedure is carried out in sequence: (1) By Ar and N 2 The mixed gas is inflated to the single crystal growth furnace until the pressure reaches 30kPa, then the pressure is kept unchanged, meanwhile, medium frequency induction heating is adopted to raise the temperature, the temperature of the raw material is set at 2400 ℃, the temperature is kept for 3 hours after reaching the temperature, and then the temperature in the furnace is kept unchanged; (2) Pressure is controlled by a pressure control system of the growth furnaceReducing to 1200Pa and maintaining for 2 hours; (3) The pressure was then maintained at 1200Pa for 20 hours, and the crucible was lowered at a rate of 1mm/h for 20mm; (4) Then, the pressure is continuously maintained at 1200Pa for 100h; (5) Thereafter, the pressure was raised to 30kPa, and the crucible temperature was reduced to 1000 ℃ at a rate of 100 ℃/h for 10 hours; then the temperature of the crucible is reduced to 800 ℃ at the speed of 10-800 ℃/h; (6) Then, the power supply was turned off, and after the SiC single crystal and the crucible were cooled to room temperature, the crystal was taken out to obtain an 8-inch 4H-SiC single crystal.
FIG. 3 is a physical view showing a SiC single crystal ingot having a diameter of 213mm obtained by growth in this example.
Example 2
The method for growing a large-sized SiC single crystal using the apparatus shown in fig. 3 of the present invention includes the steps of:
4H-SiC is used as a seed crystal, and a C face is used as a crystal growth face. The seed crystal was bonded to the inside of the graphite crucible cover. And filling enough Si powder, C powder raw materials and V-containing particles in a ratio of 1:1:2 outside a graphite sleeve of a crucible main body, placing a crucible cover adhered with seed crystals on the upper part of the crucible, and placing the crucible cover into an induction coil in a single crystal growth furnace after assembly.
Vacuumizing the growth chamber of the single crystal furnace until the pressure is less than 10 -3 Pa, flushing high-purity Ar into the growth chamber to 90kPa; vacuumizing the growth chamber of the single crystal furnace again until the pressure is less than 10 -3 Pa, flushing high-purity Ar into the growth chamber to 90kPa; this procedure was repeated 3 times; then the following processes are sequentially carried out: (1) Charging argon gas into the growth furnace until the pressure reaches 90kPa, keeping the pressure unchanged, heating by adopting medium-frequency induction heating, setting the temperature of the raw material at 2000 ℃, preserving heat for 4 hours after the temperature reaches, and keeping the temperature in the furnace unchanged; (2) Reducing the pressure to 1000Pa through a growth furnace pressure control system, and keeping for 2 hours; (3) Maintaining the pressure at 1000Pa for 20 hours, and reducing the crucible by 20mm at a speed of 1 mm/h; (4) maintaining the pressure at 1000Pa for 200h; (5) Raising the pressure to 30kPa, reducing the temperature to 600 ℃, and keeping for 2 hours; (6) And then the power supply is turned off, and after the SiC single crystal and the crucible are cooled to room temperature, the crystal is taken out, and the large-size high-purity insulating 4H-SiC single crystal is obtained.
Example 3
The method for growing a large-sized semi-insulating silicon carbide single crystal using the apparatus shown in fig. 4 of the present invention comprises the steps of:
4H-SiC was used as a seed crystal, and the C-plane was used as a crystal growth plane. The seed crystal was bonded to the inside of the graphite crucible cover. And filling enough SiC powder and VC powder particles in a ratio of 1:2 outside a graphite sleeve of the crucible main body, placing a crucible cover adhered with seed crystals on the upper part of the crucible, and placing the crucible cover into an induction coil in a single crystal growth furnace after assembly.
Vacuumizing the growth chamber of the single crystal furnace until the pressure is less than 10 -3 Pa, flushing high-purity Ar to 10kPa into the growth chamber, heating the graphite crucible to 600 ℃, and keeping for 40 minutes; vacuumizing the growth chamber of the single crystal furnace again until the pressure is less than 10 -3 Pa, flushing high-purity Ar to 10kPa into the growth chamber, and repeating the process for 3 times; then the following processes are sequentially carried out: (1) By Ar and H 2 Aerating the growth furnace until the pressure reaches 30kPa, keeping the pressure unchanged, heating by adopting medium-frequency induction heating, setting the temperature of the raw material at 2000 ℃, preserving heat for 4 hours after the temperature reaches, and keeping the temperature in the furnace unchanged; (2) Reducing the pressure to 700Pa in 1 hour by a growth furnace pressure control system, and keeping for 2 hours; after (3), maintaining the pressure at 700Pa for 20 hours; then the crucible is lowered at a speed of 1mm/h for 20mm; (4) maintaining the pressure at 700Pa for 200h; (5) Then, the pressure is increased to 30kPa, the temperature is reduced to 600 ℃, and the temperature is kept for 2 hours; (6) And then the power supply is turned off, and after the SiC single crystal and the crucible are cooled to room temperature, the crystal is taken out, and the large-size high-purity insulating 4H-SiC single crystal is obtained.
Example 4
The method for growing a large-sized semi-insulating silicon carbide single crystal using the apparatus shown in fig. 5 of the present invention comprises the steps of:
4H-SiC is used as seed crystal, and C face is used as crystal growth face. The seed crystal is bonded to the expanded region on the graphite crucible cover. And filling high-purity SiC raw materials outside a graphite sleeve of the crucible main body, placing a crucible cover adhered with seed crystals on the upper part of the crucible, and placing the crucible cover into an induction coil in a single crystal growth furnace after assembly.
Vacuumizing the growth chamber of the single crystal furnace until the pressure is less than 10 -3 Pa, flushing high-purity Ar into the growth chamber to 100Pa; vacuumizing the growth chamber of the single crystal furnace again until the pressure is less than 10 -3 Pa, flushing high-purity Ar into the growth chamber to 100Pa; this procedure was repeated 3 times; then the following processes are sequentially carried out: (1) Argon gas is used for filling high-purity Ar/N into a growth furnace 2 Mixing gas until the pressure reaches 100Pa, keeping the pressure unchanged, heating by adopting medium-frequency induction heating, setting the temperature of the raw material at 2200 ℃, preserving heat for 4 hours after the temperature reaches the 2200 ℃, and keeping the temperature in the furnace unchanged; (2) Reducing the pressure to 1000Pa through a growth furnace pressure control system, and keeping for 2 hours; (3) Then, the pressure was maintained at 1000Pa, for 20 hours, and the crucible was lowered at a speed of 1mm/h by 20mm; (4) Then, the pressure is continuously maintained at 1000Pa for 60 hours; (5) Then, the pressure is increased to 30kPa, the temperature is reduced to 800 ℃, and the temperature is kept for 10 hours; (6) And then turning off the power supply, and taking out the crystal after the SiC single crystal and the crucible are cooled to room temperature to obtain the large-size 4H-SiC single crystal.
It should be noted that the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same. Although specific process parameters can be optimized and adjusted, the basic structure of the two main core guiding ideas and the growth device of the invention are clear. It should be understood by those skilled in the relevant art that the invention can be practiced with modification and equivalent arrangements without departing from the spirit and scope of the present invention, which is intended to be encompassed within the scope of the appended claims.
Claims (10)
1. A method of growing a silicon carbide single crystal comprising the steps of:
(1) Assembling the feedstock into an apparatus for single crystal growth of silicon carbide;
(2) Placing the device in an induction coil of a single crystal growth furnace;
(3) Then, a first protective gas is adopted for washing the furnace, and the vacuum degree of the growth furnace is controlled;
(4) Then, in the presence of a second protective gas, silicon carbide single crystal growth is performed by controlling the pressure and temperature in the apparatus;
(5) Annealing the device after the growth of the silicon carbide single crystal is completed; cooling the device to room temperature to obtain a silicon carbide single crystal;
the device comprises a graphite crucible main body, a graphite crucible cover and seed crystals, wherein the seed crystals are fixed on the inner side of the graphite crucible cover; the apparatus further comprises a graphite ring positioned between the graphite crucible body and the graphite crucible cover;
the graphite ring is comprised of an expanded diameter section proximate to the graphite crucible cover and a constant diameter section distal from the graphite crucible cover, wherein the expanded diameter section has an inclined face inclined relative to the seed crystal and the inclined face extends toward the seed crystal in at least alignment with a peripheral edge of the seed crystal.
2. The method of claim 1, wherein the inclined surface is inclined at an angle of 30-89 ° relative to a radial direction of the graphite crucible body;
preferably, the inner diameter of the constant diameter section is the same as the inner diameter of the graphite crucible body;
preferably, the inclined surface extends towards the seed crystal to cover 10-30mm of the periphery of the seed crystal.
3. The method of claim 1, wherein the apparatus further comprises at least one graphite sleeve within the graphite crucible body to divide the graphite crucible body into a feedstock region surrounded by the graphite sleeve and the graphite crucible body and a non-feedstock region surrounded by the graphite sleeve interior;
the side wall of the graphite sleeve is provided with a through hole, and the extending direction of the through hole forms an acute angle with the axis of the graphite sleeve so as to prevent raw materials in the raw material area from entering the non-raw material area.
4. The method of claim 1, wherein the first and second protective gases are each independently selected from one or more of argon, hydrogen, and nitrogen.
5. The method of claim 1, wherein the first protective gas is argon.
6. The method of claim 1, wherein the second protective gas is argon and hydrogen;
preferably, the volume ratio of the hydrogen to the argon is 1 (5-1).
7. The method of claim 1, wherein the second protective gas is argon and nitrogen;
preferably, the volume ratio of the nitrogen to the argon is 1 (5-1).
8. The method according to claim 1, wherein the vacuum degree in the step (3) is 10 or less -3 Pa。
9. The method according to claim 1, wherein the controlling of the in-plant pressure and temperature in step (4) is performed under the following conditions:
the pressure at the time of growth of the silicon carbide single crystal is controlled to 100Pa to 9.8kPa, and the temperature at the time of growth of the silicon carbide single crystal is controlled to 2000 to 2400 ℃.
10. The method of claim 1, wherein the annealing in step (5) is performed in a method comprising:
cooling the device to 400-1000 ℃ at a speed of 10-800 ℃/h, and keeping for 1-10h.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115124040A (en) * | 2022-07-07 | 2022-09-30 | 安徽微芯长江半导体材料有限公司 | Solid-phase synthesis method for improving material ratio of large-particle-size silicon carbide powder |
| CN116815320A (en) * | 2023-06-28 | 2023-09-29 | 通威微电子有限公司 | Silicon carbide crystal growth device and method and silicon carbide crystal |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115124040A (en) * | 2022-07-07 | 2022-09-30 | 安徽微芯长江半导体材料有限公司 | Solid-phase synthesis method for improving material ratio of large-particle-size silicon carbide powder |
| CN116815320A (en) * | 2023-06-28 | 2023-09-29 | 通威微电子有限公司 | Silicon carbide crystal growth device and method and silicon carbide crystal |
| CN116815320B (en) * | 2023-06-28 | 2024-01-12 | 通威微电子有限公司 | Silicon carbide crystal growth device and method and silicon carbide crystal |
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