Device for growing crystal by PVT method and method for growing silicon carbide crystal

Abstract

The invention belongs to the technical field of crystal growth and manufacturing, and provides a device for growing crystals through a PVT method and a growth method of silicon carbide crystals, the device comprises a crucible and an ultrasonic generation device outside the crucible, and the ultrasonic range of the ultrasonic generation device covers a raw material area and a growth area. The ultrasonic generation device is arranged and utilized, airflow orientation in the PVT method application process is improved, the problems of uneven airflow guiding and airflow turbulence in the large-size crystal growth process are solved, the improvement effect on defects such as growth interfaces, carbon wrapping, dislocation and microtubes is greatly improved, and the device is simple in structure, low in input cost and suitable for industrial production. The method is suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal manufacturing, and relates to a device for growing crystals using a PVT method and a method for growing silicon carbide crystals. Background Art

[0002] With the rapid development of modern science and technology, semiconductor materials, as core components of the information industry and energy field, have a significant impact on the development of related technologies due to their quality and performance. Silicon carbide (SiC), as a third-generation semiconductor material, has attracted widespread attention due to its excellent physical and chemical properties.

[0003] Silicon carbide has advantages such as wide bandgap, high critical electric field and high saturation mobility, which makes it show significant advantages in the field of high-temperature, high-frequency and high-power electronic devices. These characteristics make silicon carbide materials widely used in many fields such as new energy vehicles, photovoltaic power generation, railway transportation and power systems, becoming one of the key materials to promote technological innovation in these industries.

[0004] In order to meet the demand for high-quality silicon carbide materials in industrial production, researchers are constantly exploring and developing efficient crystal growth technology. At present, physical vapor transport (PVT) is one of the main methods for preparing silicon carbide single crystals. The basic principle of the PVT method is to sublimate the silicon carbide raw material into a gaseous state by heating in a closed reaction container, and then use the temperature gradient to transfer the gaseous components to the seed crystal with a lower temperature for crystallization, and finally form a silicon carbide single crystal.

[0005] The PVT process involves complex physical and chemical changes, among which the design and control of the temperature gradient are crucial. Normally, the temperature distribution in the reaction vessel shows radial and axial gradient characteristics, that is, it gradually decreases from the center to the outside in the radial direction and gradually increases from the bottom to the top in the axial direction. This temperature distribution is conducive to the effective transmission of gaseous components from the raw material area to the seed crystal area (growth area). Specifically, when heated to a certain temperature, the silicon carbide raw material at the bottom of the reaction vessel begins to sublimate, and the generated gaseous silicon carbide molecules migrate to the seed crystal area at the top under the action of the temperature gradient. Since the temperature in the seed crystal area is relatively low, the gaseous components cool and recrystallize here, gradually forming a single crystal structure. By precisely controlling reaction conditions, such as temperature, pressure, and gas phase flow rate, the crystal growth process can be regulated, thereby obtaining high-quality silicon carbide single crystals.

[0006] However, the existence of temperature gradient will lead to uneven temperature field in the raw material area, the temperature at the edge of the reaction vessel is relatively high, and the gas phase components are easy to crystallize at the center of the top of the raw material, thereby forcing the gas phase components to move upward from the edge area of ​​the reaction vessel, making it difficult to control the diffusion and convection of the airflow inside the reaction vessel. On the one hand, this process is easy to lead to the formation of a concave growth interface, which is not conducive to the stable growth of crystals; on the other hand, in the middle and late stages of growth, the airflow will drive the micropowder in the carbonized layer at the edge of the raw material area, thereby increasing carbon encapsulation or inducing defects such as microtubes; at the same time, excessive growth components at the edge are prone to repeated crystallization and sublimation at the side edge of the growth zone, driving graphite particles into the growth interface to form carbon encapsulation. The above problems are more prominent in the production process of large-sized (such as 8 inches) crystals, and the internal airflow guidance unevenness and convection are more difficult to control.

[0007] In summary, although the PVT method has made remarkable achievements in the growth of silicon carbide single crystals, the problems faced in practical applications limit the high-efficiency and high-quality production of large-size crystals. Therefore, there is an urgent need to optimize and improve the PVT method. Summary of the invention

[0008] In view of the problems existing in the prior art, the purpose of the present invention is to provide a device for growing crystals by the PVT method and a method for growing silicon carbide crystals, wherein the device comprises a crucible and an ultrasonic generator outside the crucible, and the ultrasonic range of the ultrasonic generator covers the raw material area and the growth area. The present invention improves the airflow orientation during the application of the PVT method by setting and utilizing the ultrasonic generator, solves the problems of uneven airflow orientation and airflow turbulence during the growth of large-sized crystals, greatly improves the improvement effect of defects such as growth interface, carbon encapsulation, dislocation and microtubes, and the device has a simple structure, low investment cost, and is suitable for large-scale application and production.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a device for growing crystals by a PVT method, the device comprising a crucible with an opening at one end, the opening being provided with a matching cover; inside the crucible, the lower space away from the opening is a raw material zone, and the upper space close to the opening is a growth zone; the device also comprises an ultrasonic generator arranged outside the crucible, the ultrasonic range of the ultrasonic generator covering the raw material zone and the growth zone.

[0011] The present invention forms a new thermal field structure that can control the orientation of gas phase components in the raw material area and growth area inside the crucible by setting the ultrasonic generating device. The effect of ultrasound on gas phase components solves the problem of uneven flow direction and turbulent airflow of gas phase components during the growth process, and has a significant effect on improving defects such as crystal growth interface, carbon encapsulation, microtubes, and dislocations. Specifically, suitable ultrasonic waves can produce acoustic flow phenomena, promote the macroscopic directional movement of gas phase components, and thus avoid the phenomenon of turbulent airflow; ultrasonic waves can also cause periodic fluctuations in pressure when transmitted in the gas phase, and the pressure fluctuations generated help gas phase molecules overcome resistance for transmission. At the same time, the high-frequency vibration generated by ultrasonic waves can effectively prevent the agglomeration of particles in the gas phase components, and ultrasonic waves will produce thermal effects when propagating in the medium, which can change the uniformity of the temperature distribution of gas phase components, reduce gas viscosity, and reduce flow resistance, which is conducive to improving gas phase transmission.

[0012] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] As a preferred technical solution of the present invention, the ultrasonic generating device is arranged just below the raw material zone and is coaxial with the crucible.

[0014] Preferably, the ultrasonic frequency of the ultrasonic generating device is 40 to 100 kHz, for example, 40 kHz, 45 kHz, 50 kHz, 55 kHz, 60 kHz, 65 kHz, 70 kHz, 75 kHz, 80 kHz, 85 kHz, 90 kHz, 95 kHz or 100 kHz.

[0015] In the present invention, the ultrasonic frequency of the ultrasonic generating device should be adaptively adjusted according to the specific growth reaction in actual application. Too high a frequency may cause excessive pressure fluctuations and produce unstable phenomena such as shock waves, which will hinder the normal transmission of gas phase components.

[0016] Preferably, in the orthographic projection of the plane where the opening of the crucible is located, the ultrasonic diameter range of the ultrasonic generating device is 20% to 50% of the diameter of the crucible, for example, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48% or 50%.

[0017] As a preferred technical solution of the present invention, a porous barrier layer is provided inside the crucible between the raw material zone and the growth zone.

[0018] The present invention provides the porous barrier layer and utilizes a large number of pores in the porous barrier layer to provide a transmission channel for the gas phase components, thereby further stabilizing the airflow entering the growth zone and reducing growth defects. At the same time, it can effectively filter the micropowder generated by the ultrasonic energy wave vibration from entering the growth zone, avoiding the generation of defects such as wrapping and microtubes.

[0019] Preferably, the material of the porous barrier layer includes a carbon material, and the carbon material includes a combination of one or more of graphite, porous graphite, and carbon fiber.

[0020] Preferably, the porosity of the porous barrier layer is 30% to 80%, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%, etc.

[0021] Preferably, the porous barrier layer is a single-layer structure or a composite structure formed by at least two sub-layers, with a total thickness of 3 to 40 mm, for example, 3 mm, 5 mm, 8 mm, 10 mm, 13 mm, 15 mm, 18 mm, 20 mm, 23 mm, 25 mm, 28 mm, 30 mm, 33 mm, 35 mm, 38 mm or 40 mm.

[0022] Preferably, in the porous barrier layer, the pore size of the sublayer close to the raw material region is larger than the pore size of the sublayer close to the growth region.

[0023] Preferably, the porous barrier layer consists of two layers, the pore size of the sublayer close to the raw material zone is 100-500nm, for example, 100nm, 130nm, 150nm, 180nm, 200nm, 230nm, 250nm, 280nm, 300nm, 330nm, 350nm, 380nm, 400nm, 420nm, 450nm, 480nm or 500nm, etc., and the pore size of the sublayer close to the growth zone is 20-100nm, for example, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm or 100nm, etc.

[0024] Preferably, a limiting step is provided on the inner wall of the crucible, and the porous barrier layer is provided on the limiting step for fixation.

[0025] As a preferred technical solution of the present invention, the device for growing crystals using the PVT method further includes a growth chamber side wall, which is arranged in the growth zone to divide the growth zone into an inner growth chamber area and an outer growth chamber area.

[0026] Preferably, one end of the growth chamber side wall close to the raw material zone is arranged on the porous barrier layer for support and fixation.

[0027] Preferably, a through hole is formed on a side wall of the growth chamber at one end close to the opening, and the through hole connects the inner area of ​​the growth chamber and the outer area of ​​the growth chamber.

[0028] The present invention provides the through holes on the side wall of the growth chamber to alleviate the convection in the growth chamber caused by the airflow after ultrasonic enhancement.

[0029] Preferably, the diameter of the through hole is ≤2 mm, for example, 2 mm, 1.8 mm, 1.6 mm, 1.4 mm, 1.2 mm, 1 mm, 0.8 mm, 0.6 mm, 0.4 mm, 0.2 mm or 0.1 mm.

[0030] Preferably, the center of the through hole is 1 to 5 mm from the opening, for example, 1 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2 mm, 2.3 mm, 2.5 mm, 2.8 mm, 3 mm, 3.2 mm, 3.5 mm, 3.8 mm, 4 mm, 4.2 mm, 4.5 mm, 4.8 mm or 5 mm.

[0031] As a preferred technical solution of the present invention, the device for growing crystals by the PVT method also includes an insulation layer and a heater; the insulation layer wraps the outside of the crucible, and the heater is arranged around the insulation layer away from the outside of the crucible; the ultrasonic generating device is arranged at the bottom of the outside of the crucible in the insulation layer.

[0032] It should be noted that the present invention does not specifically limit the size of the crucible. The crucible should be reasonably adjusted to meet the needs of the target size crystals, for example, to make it suitable for the growth of 8-inch and larger crystals.

[0033] Exemplarily, the diameter of the crucible is 200-300 mm, for example, 200 mm, 210 mm, 220 mm, 230 mm, 240 mm, 250 mm, 260 mm, 270 mm, 280 mm, 290 mm or 300 mm.

[0034] In a second aspect, the present invention provides a method for growing a silicon carbide crystal, the method using the device for growing a crystal using the PVT method described in the first aspect, the method comprising the following steps:

[0035] S1. Load the silicon carbide raw material into the raw material area of ​​the crucible, and then tighten the cover and the crucible;

[0036] S2. The crucible is heated to a first preheating temperature under a vacuum environment, and then the temperature is continued to rise under a protective atmosphere of a first pressure to a second preheating temperature, and then the pressure of the protective atmosphere is reduced to a second pressure, and the ultrasonic generator is turned on;

[0037] S3. Raise the temperature to the growth temperature again and grow to obtain silicon carbide crystals.

[0038] As a preferred technical solution of the present invention, in step S1, the distance between the material surface of the raw material in the raw material area and the top surface of the raw material area is 0 to 10 mm, for example, 0 mm (i.e., filling the raw material area), 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm, etc.

[0039] Preferably, in step S1, before tightening the cover and the crucible, a porous barrier layer is first arranged in the crucible, and then a side wall of the growth chamber is arranged on the porous barrier layer. Then, the cover and the crucible are tightened so that the edge of the porous barrier layer is in close contact with the inner wall of the crucible, and the end of the side wall of the growth chamber close to the opening is in close contact with the cover.

[0040] As a preferred technical solution of the present invention, in step S2, the vacuum degree of the vacuum environment is less than 1×10 -1 Pa, for example 9×10 -2 Pa, 6×10 -2 Pa, 3×10 -2 Pa, 1×10 -2 Pa, 9×10 -3 Pa, 6×10 -3 Pa, 3×10 -3 Pa, 1×10 -3 Pa, 9×10 -4 Pa, 6×10 -4 Pa, 2×10 -4 Pa or 1×10 -4 Pa et al.

[0041] Preferably, the heating power for raising the temperature to the first preheating temperature is 1 to 8 kW, for example, 1 kW, 1.5 kW, 2 kW, 2.5 kW, 3 kW, 3.5 kW, 4 kW, 4.5 kW, 5 kW, 5.5 kW, 6 kW, 6.5 kW, 7 kW, 7.5 kW or 8 kW, etc.

[0042] Preferably, the first preheating temperature is 1000-1200°C, for example, 1000°C, 1020°C, 1040°C, 1060°C, 1080°C, 1100°C, 1120°C, 1140°C, 1160°C, 1180°C or 1200°C.

[0043] Preferably, the first pressure is 400-600 mbar, for example, 400 mbar, 420 mbar, 440 mbar, 460 mbar, 480 mbar, 500 mbar, 520 mbar, 540 mbar, 560 mbar, 580 mbar or 600 mbar.

[0044] Preferably, the heating rate to the second preheating temperature is 1-5°C / min, for example, 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min or 5°C / min, etc.

[0045] Preferably, the second preheating temperature is 1800-2000°C, for example, 1800°C, 1820°C, 1850°C, 1880°C, 1900°C, 1920°C, 1950°C, 1980°C or 2000°C.

[0046] Preferably, the pressure reduction rate to the second pressure is 0.5-2 mbar / min, for example 0.5 mbar / min, 0.8 mbar / min, 1 mbar / min, 1.2 mbar / min, 1.4 mbar / min, 1.6 mbar / min, 1.8 mbar / min or 2 mbar / min.

[0047] Preferably, the second pressure is 8-12 mbar, for example, 8 mbar, 8.5 mbar, 9 mbar, 9.5 mbar, 10 mbar, 10.5 mbar, 11 mbar, 11.5 mbar or 12 mbar.

[0048] Preferably, in step S2, the ultrasonic frequency of the ultrasonic generating device is 40 to 100 kHz, for example, 40 kHz, 45 kHz, 50 kHz, 55 kHz, 60 kHz, 65 kHz, 70 kHz, 75 kHz, 80 kHz, 85 kHz, 90 kHz, 95 kHz or 100 kHz.

[0049] As a preferred technical solution of the present invention, in step S3, the heating rate to the growth temperature is 0.2-1°C / min, for example, 0.2°C / min, 0.3°C / min, 0.4°C / min, 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min or 1°C / min, etc.

[0050] Preferably, the growth temperature is 2100-2300°C, for example, 2100°C, 2130°C, 2150°C, 2180°C, 2200°C, 2230°C, 2250°C, 2280°C or 2300°C.

[0051] Preferably, the growth time is 80 to 200 h, for example, 80 h, 90 h, 100 h, 110 h, 120 h, 130 h, 140 h, 150 h, 160 h, 170 h, 180 h, 190 h or 200 h.

[0052] As a preferred technical solution of the present invention, after the growth is completed, the ultrasonic generating device is turned off, and the pressure of the protective atmosphere is increased to 50-80 kPa and then cooled until it reaches room temperature and then taken out, for example, 50 kPa, 53 kPa, 55 kPa, 58 kPa, 60 kPa, 63 kPa, 65 kPa, 68 kPa, 70 kPa, 72 kPa, 75 kPa, 78 kPa or 80 kPa.

[0053] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0054] The present invention forms a new thermal field structure capable of controlling the orientation of gas phase components in the raw material area and the growth area inside the crucible by arranging an ultrasonic generator in the device for growing crystals by the PVT method, and solves the problems of uneven gas phase component flow and turbulent gas flow during the growth process by using the influence of ultrasound on the gas phase components, and has a significant effect on improving defects such as crystal growth interface, carbon encapsulation, microtubes, dislocations, etc. It is particularly suitable for the PVT growth of silicon carbide.

[0055] The present invention further arranges the porous barrier layer between the raw material zone and the growth zone in the crucible, and utilizes a large number of pores in the porous barrier layer to provide a transmission channel for the gas phase components, thereby further stabilizing the airflow entering the growth zone and reducing growth defects. At the same time, it can effectively filter the micropowder generated by the ultrasonic energy wave vibration process from entering the growth zone, thereby avoiding the generation of defects such as wrapping and microtubes.

[0056] The present invention provides the through holes on the side wall of the growth chamber in the growth zone to alleviate the convection in the growth chamber caused by the airflow after ultrasonic enhancement, and further stabilizes the flow and transmission process of the gas phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a schematic structural diagram of a device for growing crystals using the PVT method according to Example 1;

[0058] Figure 2 is a schematic diagram of a side wall of a growth chamber in a device for growing crystals using a PVT method according to Example 1;

[0059] In the figure: 10-crucible, 11-cover, 12-raw material area, 13-growth area, 20-ultrasonic generating device, 30-porous barrier layer, 40-side wall of growth chamber, 41-through hole, 50-insulation layer, 60-heater, 70-seed crystal. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0061] It should be clear to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0062] In some specific embodiments, the present invention provides a device for growing crystals using a PVT method, such as Figure 1 As shown, the device includes a crucible 10 with an opening at one end, and the opening is provided with a matching cover 11; inside the crucible 10, the lower space away from the opening is a raw material zone 12, and the upper space close to the opening is a growth zone 13; the device also includes an ultrasonic generating device 20 arranged outside the crucible 10, and the ultrasonic range of the ultrasonic generating device 20 covers the raw material zone 12 and the growth zone 13.

[0063] In one embodiment, the ultrasonic generator 20 is disposed directly below the raw material zone 12 and is coaxial with the crucible 10 .

[0064] In one embodiment, in the orthographic projection of the plane where the opening of the crucible 10 is located, the ultrasonic diameter range of the ultrasonic generating device 20 is 20% to 50% of the diameter of the crucible 10 .

[0065] In one embodiment, the ultrasonic frequency of the ultrasonic generating device 20 is 40-100 kHz.

[0066] In one embodiment, a porous barrier layer 30 is disposed between the raw material zone 12 and the growth zone 13 inside the crucible 10 .

[0067] In one embodiment, the porous barrier layer 30 is made of a carbon material, and the carbon material includes one or a combination of graphite, porous graphite, and carbon fiber.

[0068] In one embodiment, the porosity of the porous barrier layer 30 is 30% to 80%.

[0069] In one embodiment, the porous barrier layer 30 is a single-layer structure or a composite structure formed by at least two sub-layers, with a total thickness of 3 to 40 mm.

[0070] In one embodiment, in the porous barrier layer 30 , the pore size of the sublayer close to the raw material region 12 is larger than the pore size of the sublayer close to the growth region 13 .

[0071] In one embodiment, a limiting step is provided on the inner wall of the crucible 10 , and the porous barrier layer 30 is provided on the limiting step for fixing.

[0072] In one embodiment, the porous barrier layer 30 is composed of two layers, the pore size of the sublayer close to the raw material area 12 is 100-500 nm, and the pore size of the sublayer close to the growth area 13 is 20-100 nm.

[0073] In one embodiment, the device for growing crystals by the PVT method also includes a growth chamber side wall 40, and the growth chamber side wall 40 is arranged in the growth zone 13 to divide the growth zone 13 into an inner area of ​​the growth chamber and an outer area of ​​the growth chamber; the end of the growth chamber side wall 40 close to the raw material zone 12 is arranged on the porous barrier layer 30 for support and fixation; a through hole 41 is opened on the side wall of the growth chamber side wall 40 close to the opening, and the through hole 41 connects the inner area of ​​the growth chamber and the outer area of ​​the growth chamber.

[0074] In one embodiment, the diameter of the through hole 41 is ≤2 mm.

[0075] In one embodiment, the height between the center of the through hole 41 and the opening is 1 to 5 mm.

[0076] In one embodiment, the device for growing crystals using the PVT method further includes a heat preservation layer 50 and a heater 60 .

[0077] In one embodiment, the heat-insulating layer 50 wraps the outside of the crucible 10 , and the heater 60 is disposed around the outside of the heat-insulating layer 50 away from the crucible 10 .

[0078] In one embodiment, the ultrasonic generator 20 is disposed at the outer bottom of the heat-insulating layer 50 away from the crucible 10 .

[0079] In one embodiment, the diameter of the crucible 10 is 200-300 mm.

[0080] Example 1

[0081] This embodiment provides a device for growing crystals using a PVT method in the above-mentioned embodiment, the device comprising:

[0082] A crucible 10 is open at one end, and the opening is provided with a matching cover 11; the diameter of the crucible 10 is 260 mm; inside the crucible 10, the lower space away from the opening is a raw material area 12, and the upper space close to the opening is a growth area 13, and a seed crystal 70 is provided on the cover 11 of the growth area 13; the raw material area 12 and the growth area 13 form a limiting step on the inner wall of the crucible 10, so that the diameter of the raw material area 12 is smaller than that of the growth area 13;

[0083] The porous barrier layer 30 is composed of two stacked graphite sublayers, the graphite sublayer close to the raw material area 12 has a pore size of 300nm and a thickness of 18mm, and the graphite sublayer close to the growth area 13 has a pore size of 60nm and a thickness of 6mm; the porosity of the porous barrier layer 30 is 50%; the porous barrier layer 30 is arranged on the limiting step inside the crucible 10 for fixing;

[0084] The growth chamber side wall 40 is arranged in the growth zone 13 inside the crucible 10, and the growth zone 13 is divided into an inner growth zone and an outer growth zone; one end of the growth chamber side wall 40 close to the raw material zone 12 is arranged on the porous barrier layer 30 for support and fixation, such as Figure 2 As shown, a plurality of through holes 41 are provided on the side wall near one end of the opening, and the through holes 41 connect the inner area of ​​the growth chamber and the outer area of ​​the growth chamber; the diameter of each through hole 41 is 1.2 mm, and the height of the center of the through hole 41 from the opening is 1 to 5 mm;

[0085] A heat-insulating layer 50, wherein the heat-insulating layer 50 wraps the crucible 10, and a channel is left on the upper portion of the cover 11 corresponding to the heat-insulating layer 50;

[0086] A heater 60, wherein the heater 60 is disposed around the insulation layer 50 away from the outer side of the crucible 10;

[0087] An ultrasonic generating device 20 is arranged directly below the outer bottom of the heat-insulating layer 50 away from the crucible 10 and coaxial with the crucible 10; the ultrasonic range of the ultrasonic generating device 20 covers the raw material area 12 and the growth area 13; in the orthographic projection to the plane where the opening of the crucible 10 is located, the diameter of the ultrasonic range of the ultrasonic generating device 20 is 40% of the diameter of the crucible 10; the ultrasonic frequency of the ultrasonic generating device 20 is adjustable between 40 and 100 kHz.

[0088] Example 2

[0089] This embodiment provides a device for growing crystals using the PVT method, wherein the device adjusts the pore size of the graphite sublayer close to the growth region 13 from 60 nm to 15 nm. Except for the above, other conditions are exactly the same as those of Embodiment 1.

[0090] Example 3

[0091] This embodiment provides a device for growing crystals using the PVT method, wherein the device adjusts the pore size of the graphite sublayer close to the growth zone 13 from 60 nm to 20 nm. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0092] Example 4

[0093] This embodiment provides a device for growing crystals using the PVT method, wherein the device adjusts the pore size of the graphite sublayer close to the growth zone 13 from 60 nm to 100 nm. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0094] Example 5

[0095] This embodiment provides a device for growing crystals using the PVT method, wherein the device adjusts the pore size of the graphite sublayer close to the growth zone 13 from 60 nm to 130 nm. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0096] Example 6

[0097] This embodiment provides a device for growing crystals using the PVT method, which adjusts the thickness of the graphite sublayer near the raw material area 12 from 18 mm to 1 mm, and adjusts the thickness of the graphite sublayer near the growth area 13 from 6 nm to 1 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0098] Example 7

[0099] This embodiment provides a device for growing crystals using the PVT method, which adjusts the thickness of the graphite sublayer near the raw material area 12 from 18 mm to 2 mm, and adjusts the thickness of the graphite sublayer near the growth area 13 from 6 nm to 2 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0100] Example 8

[0101] This embodiment provides a device for growing crystals using the PVT method, which adjusts the thickness of the graphite sublayer near the raw material area 12 from 18 mm to 10 mm, and adjusts the thickness of the graphite sublayer near the growth area 13 from 6 nm to 10 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0102] Example 9

[0103] This embodiment provides a device for growing crystals using the PVT method, which adjusts the thickness of the graphite sublayer near the raw material area 12 from 18 mm to 20 mm, and adjusts the thickness of the graphite sublayer near the growth area 13 from 6 nm to 20 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0104] Example 10

[0105] This embodiment provides a device for growing crystals using the PVT method, which adjusts the thickness of the graphite sublayer near the raw material area 12 from 18 mm to 24 mm, and adjusts the thickness of the graphite sublayer near the growth area 13 from 6 nm to 22 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0106] Embodiment 11

[0107] This embodiment provides a device for growing crystals using the PVT method, wherein the device adjusts the thickness of the graphite sublayer near the raw material area 12 from 18 mm to 0 mm, i.e., the graphite sublayer is not provided. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0108] Example 12

[0109] This embodiment provides a device for growing crystals using the PVT method, wherein the device adjusts the thickness of the graphite sublayer near the growth zone 13 from 6 nm to 0 nm, that is, the graphite sublayer is not provided. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0110] Embodiment 13

[0111] This embodiment provides a device for growing crystals using the PVT method, wherein the device adjusts the thickness of the graphite sublayer near the raw material area 12 from 18 mm to 0 mm, and adjusts the thickness of the graphite sublayer near the growth area 13 from 6 nm to 0 nm, that is, the porous barrier layer is not arranged inside the crucible 10. Except for the above, other conditions are exactly the same as those in Example 1.

[0112] Embodiment 14

[0113] This embodiment provides a device for growing crystals using a PVT method, wherein the diameter of the through hole 41 on the side wall 40 of the growth chamber is adjusted from 1.2 mm to 0.3 mm. Except for the above, other conditions are exactly the same as those of Embodiment 1.

[0114] Embodiment 15

[0115] This embodiment provides a device for growing crystals using a PVT method, wherein the diameter of the through hole 41 on the side wall 40 of the growth chamber is adjusted from 1.2 mm to 0.7 mm. Except for the above, other conditions are exactly the same as those of Embodiment 1.

[0116] Example 16

[0117] This embodiment provides a device for growing crystals using the PVT method. The device adjusts the diameter of the through hole 41 on the side wall 40 of the growth chamber from 1.2 mm to 2 mm. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0118] Embodiment 17

[0119] This embodiment provides a device for growing crystals using the PVT method. The device adjusts the diameter of the through hole 41 on the side wall 40 of the growth chamber from 1.2 mm to 2.3 mm. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0120] Embodiment 18

[0121] This embodiment provides a device for growing crystals using the PVT method, wherein the diameter of the through hole 41 on the side wall 40 of the growth chamber is adjusted from 1.2 mm to 0 mm, i.e., the through hole 41 is not provided on the side wall 40 of the growth chamber. Except for the above, other conditions are exactly the same as those of Embodiment 1.

[0122] Comparative Example 1

[0123] This comparative example provides a device for growing crystals using the PVT method, wherein the device does not contain the ultrasonic generator 20 . Except for the above, other conditions are exactly the same as those of Example 1.

[0124] Application Example 1

[0125] This application example provides a method for growing an 8-inch silicon carbide crystal. The method uses the devices for growing crystals using the PVT method provided in Examples 1 to 18, respectively. The method includes the following steps:

[0126] S1. The silicon carbide raw material is loaded into the crucible 10, and the distance between the material surface of the raw material area 12 and the top surface of the raw material area 12 is 0 mm, that is, the raw material area 12 is filled; a porous barrier layer 30 is arranged on the limiting step in the crucible 10, and then a growth chamber side wall 40 is arranged on the porous barrier layer 30, and then the cover 11 and the crucible 10 are screwed tightly, so that the edge of the porous barrier layer 30 is in close contact with the inner wall of the crucible 10, and the end of the growth chamber side wall 40 close to the opening is in close contact with the cover 11;

[0127] S2. Place the entire set of crucibles 10 into the furnace and evacuate to <10 -1Pa is maintained for a certain period of time, the heating power is turned on, and the power is increased to the first power of 5kW for heating, and the molecular pump is turned on at the same time until the temperature rises to the first preheating temperature of 1100°C; then the protective gas is filled to the first pressure of 500mbar, and the temperature is switched to temperature control. After the temperature is increased to the second preheating temperature of 1900°C at 2°C / min, the pressure is reduced to the second pressure of 10mbar at a pressure reduction rate of 1mbar / min, and then the ultrasonic generating device 20 is turned on to control the ultrasonic frequency to 50kHz;

[0128] S3. The temperature is then raised to the growth temperature of 2200°C at a rate of 0.5°C / min, and the growth is continued for 160 hours. After the growth is completed, the heating and ultrasonic generating device 20 is turned off, a protective gas is filled to 80 kPa, and the silicon carbide is taken out after being cooled to room temperature to obtain an 8-inch silicon carbide crystal.

[0129] Application Example 2

[0130] This application example provides a method for growing silicon carbide crystals. The method adopts the device for growing crystals by the PVT method provided in Example 1. The method adjusts the ultrasonic frequency of the ultrasonic generating device 20 in step S2 from 50 kHz to 30 kHz, 40 kHz, 80 kHz, 100 kHz and 110 kHz respectively. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0131] Application Comparative Example 1

[0132] This application example provides a method for growing silicon carbide crystals. The method adopts the device for growing crystals using the PVT method provided in Comparative Example 1. The method does not use the ultrasonic generator 20 to generate ultrasound in steps S2 and S3. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0133] Characterization and Testing:

[0134] The silicon carbide crystals obtained in Application Example 1, Application Example 2 and Application Comparative Example 1 were taken, and then cut, ground and polished to obtain silicon carbide wafers with a thickness of 500 μm. The cleaned wafers were inspected using a Candela 8520 surface defect detection system (the scan speed was set to 2000 under the SSpfRO channel), and the results were recorded in Table 1.

[0135] Table 1

[0136]

[0137] It can be seen from Table 1 that the reasonable selection and matching of the ultrasonic generator, the porous barrier layer and the through-hole diameter have a significant improvement effect on the wafer wrapping and micro-tube.

[0138] From the above, it can be seen that the present invention improves the airflow orientation during the application of the PVT method by setting and utilizing the ultrasonic generating device 20, solves the problems of uneven airflow orientation and airflow turbulence during the growth process of large-size crystals, and greatly enhances the improvement effect of defects such as growth interface, carbon encapsulation, dislocation and microtubes. The device has a simple structure and low investment cost, and is suitable for large-scale application and production.

[0139] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0140] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0141] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A device for growing crystals by a PVT method, characterized in that: The device comprises a crucible with an opening at one end, wherein the opening is provided with a matching cover; inside the crucible, the lower space away from the opening is a raw material zone, and the upper space close to the opening is a growth zone; the device also comprises an ultrasonic generating device arranged outside the crucible, wherein the ultrasonic range of the ultrasonic generating device covers the raw material zone and the growth zone.

2. The device for growing crystals by the PVT method according to claim 1, characterized in that: The ultrasonic generating device is arranged just below the raw material area and coaxial with the crucible; in the orthographic projection of the plane where the opening of the crucible is located, the ultrasonic diameter range of the ultrasonic generating device is 20% to 50% of the diameter of the crucible; the ultrasonic frequency of the ultrasonic generating device is 40 to 100 kHz.

3. The device for growing crystals by the PVT method according to claim 1, characterized in that: A porous barrier layer is provided between the raw material zone and the growth zone inside the crucible; the material of the porous barrier layer includes a carbon material, and the carbon material includes a combination of one or more of graphite, porous graphite, and carbon fiber; the porosity of the porous barrier layer is 30% to 80%; The porous barrier layer is a single-layer structure or a composite structure formed by at least two sub-layers, with a total thickness of 3 to 40 mm; in the porous barrier layer, the pore size of the sub-layer close to the raw material area is larger than the pore size of the sub-layer close to the growth area; A limiting step is arranged on the inner wall of the crucible, and the porous barrier layer is arranged on the limiting step for fixing.

4. The device for growing crystals by the PVT method according to claim 3, characterized in that: The porous barrier layer consists of two layers, the pore size of the sublayer close to the raw material area is 100-500nm, and the pore size of the sublayer close to the growth area is 20-100nm.

5. The device for growing crystals by the PVT method according to claim 3 or 4, characterized in that: The device for growing crystals by the PVT method further comprises a growth chamber side wall, which is arranged in the growth zone, dividing the growth zone into an inner growth chamber area and an outer growth chamber area; one end of the growth chamber side wall close to the raw material area is arranged on the porous barrier layer for support and fixation; a through hole is provided on the side wall of the growth chamber side wall close to the opening, and the through hole connects the inner growth chamber area and the outer growth chamber area; The diameter of the through hole is ≤2 mm; the height from the center of the through hole to the opening is 1 to 5 mm.

6. The device for growing crystals by the PVT method according to claim 1, characterized in that: The device for growing crystals by the PVT method further comprises a heat preservation layer and a heater; the heat preservation layer wraps the outside of the crucible, and the heater is arranged around the heat preservation layer away from the outside of the crucible; the ultrasonic generator is arranged at the bottom of the heat preservation layer away from the outside of the crucible; The diameter of the crucible is 200-300 mm.

7. A method for growing silicon carbide crystals, characterized in that: The method uses the device for growing crystals by the PVT method according to any one of claims 1 to 6, and the method comprises the following steps: S1. Load the silicon carbide raw material into the raw material area of ​​the crucible, and then tighten the cover and the crucible; S2. The crucible is heated to a first preheating temperature under a vacuum environment, and then the temperature is continued to rise under a protective atmosphere of a first pressure to a second preheating temperature, and then the pressure of the protective atmosphere is reduced to a second pressure, and the ultrasonic generator is turned on; S3. Raise the temperature to the growth temperature again and grow to obtain silicon carbide crystals.

8. The method for growing silicon carbide crystal according to claim 7, characterized in that: In step S1, the distance between the material surface of the raw material area and the top surface of the raw material area is 0 to 10 mm; In step S1, before tightening the cover and the crucible, a porous barrier layer is first arranged in the crucible, and then a side wall of the growth chamber is arranged on the porous barrier layer. Then the cover and the crucible are tightened so that the edge of the porous barrier layer is in close contact with the inner wall of the crucible, and the end of the side wall of the growth chamber close to the opening is in close contact with the cover.

9. The method for growing silicon carbide crystal according to claim 7, characterized in that: In step S2, the vacuum degree of the vacuum environment is less than 1×10 -1 Pa; The heating power for heating to the first preheating temperature is 1-8 kW; the first preheating temperature is 1000-1200° C.; the first pressure is 400-600 mbar; The heating rate of heating to the second preheating temperature is 1-5°C / min; the second preheating temperature is 1800-2000°C; the pressure reduction rate of reducing the pressure to the second pressure is 0.5-2mbar / min; the second pressure is 8-12mbar; The ultrasonic frequency of the ultrasonic generating device is 40 to 100 kHz.

10. The method for growing silicon carbide crystal according to claim 7, characterized in that: In step S3, the heating rate to the growth temperature is 0.2-1°C / min; the growth temperature is 2100-2300°C; the growth time is 80-200h; After the growth is completed, the ultrasonic generator is turned off, the pressure of the protective atmosphere is increased to 50-80 kPa, and then cooled to room temperature before being taken out.

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