CN113492139A

CN113492139A - Processing method and device for improving cleanliness of seed crystal

Info

Publication number: CN113492139A
Application number: CN202110749772.5A
Authority: CN
Inventors: 李加林; 刘星; 张宁; 姜岩鹏; 刘家朋
Original assignee: Shandong Tianyue Advanced Technology Co Ltd
Current assignee: Shandong Tianyue Advanced Technology Co Ltd
Priority date: 2021-07-01
Filing date: 2021-07-01
Publication date: 2021-10-12
Anticipated expiration: 2041-07-01
Also published as: CN113492139B

Abstract

The application discloses a processing method and a processing device for improving seed crystal cleanliness, and belongs to the technical field of semiconductor material cleaning. The device includes: the side wall of the shell is provided with a plurality of seed crystal inlets along the axial direction of the shell, the top or the bottom of the shell is provided with an air inlet, the side wall of the shell close to each seed crystal inlet is correspondingly provided with at least one air outlet, and the air outlet and the air inlet are positioned on the same side of the seed crystal inlets; and the seed crystal tray is inserted into the seed crystal inlet, so that the seed crystal and the shell on the side of the gas inlet enclose a gas cleaning chamber, and cleaning gas is blown into the gas cleaning chamber from the gas inlet and flows to the surface of the seed crystal closest to the gas inlet and then flows out from the gas outlet. The device can effectively remove residual particles adsorbed on the surface of the seed crystal, improve the smoothness of the surface of the seed crystal and improve the surface quality of the seed crystal.

Description

Processing method and device for improving cleanliness of seed crystal

Technical Field

The application relates to a processing method and a processing device for improving the cleanliness of seed crystals, and belongs to the technical field of semiconductor material cleaning.

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.

The most widely used method for growing silicon carbide crystals is the physical vapor transport method, and then the liquid phase method, the chemical vapor transport method and the like are available. The high-quality silicon carbide substrate prepared by the growth method can not be separated from the high-quality silicon carbide seed crystal (SiC seed crystal), and the silicon carbide crystal grows on the seed crystal in a homogeneous way. The presence of the seed crystal provides an easier center for continued growth of the crystal for subsequent crystal growth. Problems existing in the seed crystal are often inherited into the subsequently grown crystal, and the quality, size and surface state of the seed crystal have a crucial influence on the quality and size of the grown crystal.

Conventional seed crystals for growing silicon carbide crystals are generally grown at an angle off the C-plane (0001) in order to obtain a sufficiently high growth step density and high quality crystals. The high-quality seed crystal is obtained by requiring high levels of various parameters of the silicon carbide crystal, has high requirements on the processing process of the seed crystal substrate, and the silicon carbide seed crystal substrate meeting the growth requirements is obtained after the procedures of cutting, grinding, polishing, washing and the like.

The consistency of the surface quality of the seed crystal is improved in the processing process of the seed crystal substrate, the growth of large-scale silicon carbide single crystals is facilitated, the original growth information of the surface of the seed crystal is inevitably damaged in the cutting, grinding and polishing process in the processing process of the surface of the seed crystal, a large number of particles can remain on the surface of the seed crystal, the particles cannot be effectively removed in the traditional cleaning mode, especially, the residual particles of the processing raw materials are strongly adsorbed on the surface of the seed crystal, the roughness of the surface of the seed crystal is increased due to the existence of the particles, the nucleation quality is seriously affected, and the crystal defects such as micropipes, polytype, dislocation, stacking fault and the like are induced.

Disclosure of Invention

In order to solve the problems, the application provides a processing method and a processing device for improving the cleanliness of seed crystals, and by using the processing device, the surface of the seed crystals is quantitatively and directionally blown by clean gas from a gas inlet, so that residual particles adsorbed on the surface of the seed crystals can be effectively removed, the smoothness of the surface of the seed crystals is improved, the generation of defects such as micropipes, polytype and dislocation in the crystal growing process is reduced, and the quality of silicon carbide crystals is improved.

According to an aspect of the application, a processing apparatus for improving the cleanliness of seed crystals is provided, a plurality of seed crystals to be cleaned are fixed in a shell through a seed crystal tray, the seed crystals closest to an air inlet and the shell on the side of the air inlet form a gas cleaning chamber, each seed crystal can form the gas cleaning chamber with the shell, clean gas cleans the seed crystals in the gas cleaning chamber, after cleaning one seed crystal, the seed crystal tray is taken down from the seed crystal tray, the seed crystal tray which does not carry the seed crystal covers a seed crystal opening again, cleaning of the next seed crystal is carried out, the cleaning efficiency of the seed crystals can be improved, manual operation steps are reduced, secondary pollution of the seed crystals is avoided, and the seed crystal cleaning apparatus is suitable for cleaning the seed crystals in a large batch. The device includes:

the side wall of the shell is provided with a plurality of seed crystal inlets along the axial direction of the shell, the top or the bottom of the shell is provided with an air inlet, the side wall of the shell close to each seed crystal inlet is correspondingly provided with at least one air outlet, and the air outlet and the air inlet are positioned on the same side of the seed crystal inlets; and

the seed crystal tray is inserted into the seed crystal inlet, so that the seed crystal and the shell on the side of the air inlet enclose a gas cleaning chamber, and cleaning gas is blown into the gas cleaning chamber from the air inlet and flows to the surface of the seed crystal closest to the air inlet and then flows out from the air outlet.

Optionally, the distance between the air inlet and the seed crystal inlet closest to the air inlet is 50-1500mm, preferably 500-1000mm, and more preferably 700-800 mm.

Preferably, the distance between two adjacent seed crystal inlets is 10-60mm, the number of the seed crystal inlets is 2-40, and the height of the seed crystal inlet is 3-25 mm.

Preferably, the distance between two adjacent seed crystal inlets is 10-30mm, the number of the seed crystal inlets is 10-25, and the height of the seed crystal inlet is 10-20 mm.

More preferably, the distance between two adjacent seed crystal inlets is 15-20mm, the number of the seed crystal inlets is 10-15, and the height of the seed crystal inlet is 10-15 mm.

Optionally, the number of the air outlets corresponding to each seed crystal inlet is multiple, and the multiple air outlets are arranged at least in a single row along the axial direction of the housing and are uniformly distributed in the radial direction of the housing.

Preferably, a plurality of the air outlets are arranged in a single row in the axial direction of the housing.

Optionally, the distance between the air outlets and the seed crystal inlets is 0-10mm, the number of the air outlets in each row is 2-60, preferably 3-30, and the opening area of each air outlet is 0.5cm²-15cm²。

Preferably, the distance between the air outlets and the seed crystal inlets is 3-5mm, the number of the air outlets in each row is 6-20, and the opening area of each air outlet is 0.7cm²-10cm²。

Optionally, the air outlet is rectangular and circular, preferably circular, and the aperture of the air outlet is 5-20mm, preferably 10-15 mm.

The distances are the shortest distance between the gas outlet and the seed crystal inlet.

Optionally, a heating coil is sleeved outside the shell, and the heating coil is arranged between the air inlet and a seed crystal inlet closest to the air inlet and used for heating the cleaning gas entering the gas cleaning chamber;

preferably, the housing is of a cylindrical structure, the diameter of the housing is 50-500mm, and the heating coil and the housing are arranged on the same central axis.

Optionally, a support plate is arranged on one side of the shell close to the air inlet, the side wall of the support plate is attached to the inner wall of the shell, a gas nozzle is arranged on the support plate and communicated with the air inlet, and the cleaning gas is blown into the gas cleaning chamber through the air inlet and the gas nozzle in sequence;

preferably, the support plate can drive the gas shower nozzle to lift and/or rotate.

Preferably, at least one gas nozzle is provided, at least one gas nozzle is vertically arranged at the central position of the support plate, and the rest gas nozzles are uniformly distributed around the circumference of the gas nozzle at the central position;

preferably, the distance between the gas nozzle and the seed crystal is 50-1500mm, and the included angle between the rest of the gas nozzles surrounding the gas nozzle at the central position and the support plate is 80-90 degrees.

Preferably, the number of the gas nozzles is 7, one gas nozzle is vertically arranged at the central position of the supporting plate, and the included angles between the rest 6 gas nozzles and the supporting plate are 88 degrees.

Optionally, the seed crystal inlet is arranged as a strip-shaped slit horizontally extending along the radial direction of the shell;

optionally, the housing is of a cylindrical structure, the seed crystal inlet is arc-shaped, the radian of the radial cross section of the seed crystal inlet is not less than 180 °, the shape of the seed crystal tray is matched with that of the seed crystal inlet, and the inner diameter of the seed crystal tray is consistent with that of the housing.

Preferably, the radian of the radial cross section of the seed crystal inlet is 180 degrees, and the radian of the radial direction of the seed crystal tray is 180 degrees.

Optionally, a clamping groove is formed in the edge of the bottom of the seed crystal tray, and the seed crystal tray is inserted into the seed crystal inlet through the clamping groove.

Preferably, the width of the clamping groove is consistent with the thickness of the shell, and the depth of the clamping groove is 5-30 mm.

Preferably, the clamping groove is 5-30 mm.

Optionally, the clamping connection between the seed crystal inlet and the seed crystal tray is used for improving the sealing performance between the seed crystal inlet and the seed crystal tray.

Optionally, a first raised annular groove is formed in the inner side wall of the seed crystal tray, and the first annular groove is used for fixing the seed crystal; and

a second raised annular groove is formed in the inner side wall of the shell, the second annular groove and the first annular groove are arranged at the same height, the seed crystal tray covers the seed crystal inlet, and the first annular groove is abutted to the second annular groove to fix the seed crystal;

preferably, the height of the first annular groove and the second annular groove is equal to the thickness of the seed crystal, and the width of the first annular groove and the width of the second annular groove are 2-10 mm.

Preferably, the height of the first annular groove and the height of the second annular groove are 0.1-10mm, and the width of the first annular groove and the width of the second annular groove are 4-6 mm.

Optionally, a handle is arranged on the outer side wall of the seed crystal tray, and the seed crystal tray can be taken out or put back by pulling the handle.

According to another aspect of the present application, there is provided a processing method for improving the cleanliness of a seed crystal, which is performed using the processing apparatus of any one of the above, the housing being provided therein with a support plate having a gas shower head, the method comprising the steps of:

s1: fixing a plurality of seed crystals to be cleaned in the shell;

s2: opening the gas nozzle, moving the support plate towards the seed crystal to be cleaned, and driving the gas nozzle to rotate so as to clean the seed crystal to be cleaned closest to the gas inlet for at least 30 min;

s3, closing the gas nozzle, taking down the cleaned seed crystal, replacing the seed crystal tray without the seed crystal, moving the support plate 10-60mm towards the seed crystal to be cleaned, and cleaning the next seed crystal;

s4: repeating the steps S2 and S3 until the seed crystal to be cleaned is completely cleaned;

optionally, a heating coil is sleeved outside the housing, and in step S2, the heating coil is turned on to heat the cleaning gas entering the gas cleaning chamber, where the heating temperature of the cleaning gas is 150-.

In the steps S2 and S3, the support plate moves towards the seed crystal to be cleaned, so that the distance between the gas spray head and the seed crystal to be cleaned closest to the gas inlet is 50-1500 mm;

preferably, the rotation rate of the support plate is 1 to 60 rpm.

Benefits that can be produced by the present application include, but are not limited to:

1. the application provides a processing apparatus, it is fixed in the casing through the seed crystal tray with a plurality of seed crystals of treating cleanness, every seed crystal can both form gaseous clean room with the casing, after every clean seed crystal, will not carry the seed crystal tray lid of seed crystal again after taking off with it and close the seed crystal opening, carry out the cleanness of next seed crystal, can improve the clean efficiency of seed crystal, reduce the manual operation step, avoid the secondary pollution of seed crystal, be applicable to big clean seed crystal in batches.

2. The application provides a processing apparatus, the setting up of air inlet can guarantee that the clean gas who gets into from the air inlet can effectively clean the seed crystal surface, sweeps the attached granule on seed crystal surface to the gas outlet outflow, can avoid gas impact force too big again to cause the damage to the seed crystal, avoid breaking of seed crystal.

3. According to the processing device provided by the application, the lifting of the supporting plate can adjust the volume of the gas cleaning chamber, so that the cleanliness and the cleaning efficiency of seed crystals are improved; the rotation of backup pad is convenient for sweep the great granule of adhesive force down, can also prolong the distance that clean gas transmitted to the seed crystal, plays the cushioning effect to clean gas, avoids damaging the seed crystal.

4. The processing method provided by the application can be used for quantitatively and directionally cleaning the seed crystal by using the clean gas, can be used for effectively removing residual particles adsorbed on the surface of the seed crystal, improving the smoothness of the surface of the seed crystal, reducing the generation of defects such as micropipes, polytype and dislocation in the crystal growth process and improving the quality of the silicon carbide crystal.

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 cross-sectional view of a processing apparatus according to an embodiment of the present application;

fig. 2 is a perspective view of a seed crystal tray according to an embodiment of the present disclosure;

FIG. 3 is a partial perspective view of a seed tray according to an embodiment of the present disclosure;

fig. 4 is a schematic perspective view of a housing according to an embodiment of the present application;

FIG. 5 is a perspective view of the assembly of the housing and the seed tray according to the embodiment of the present application;

list of parts and reference numerals:

10. a housing; 11. an air inlet; 12. an air outlet; 13. a gas cleaning chamber; 14. a seed crystal inlet; 15. a second annular groove; 20. a seed crystal tray; 21. seed crystal; 22. a first annular groove; 23. a handle; 30. a support plate; 31. a gas shower; 32. a gas source; 33. a motor; 34. a controller; 50. heating coil

Detailed Description

In order to more clearly explain the overall concept of the present application, the following detailed description is given by way of example in conjunction with the accompanying drawings.

In order that the above objects, features and advantages of the present application can be more clearly understood, the present application will be described in further detail with reference to the accompanying drawings and detailed description. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, however, the present application may be practiced in other ways than those described herein, and therefore the scope of the present application is not limited by the specific embodiments disclosed below.

In addition, in the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", and the like, indicate orientations and positional relationships based on those shown in the drawings, are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

In this application, unless expressly stated or limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral parts; the connection can be mechanical connection, electrical connection or communication; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The analysis method in the examples of the present application is as follows:

1. particle count detection was performed using CS8520 equipment from KLA corporation.

2. The element content is detected by SIMS testing equipment of EAG company.

3. Total thickness deviation, warp and bow measurements were performed using the Tropel equipment from Corning.

4. Microscopic examination was carried out using a microscope model BX51 from OLYMPUS.

5. The polytype test used a model HR800 Raman spectrometer from HORIBA.

6. The dislocation test was carried out using a microscope model BX51 from OLYMPUS after etching with potassium hydroxide.

7. The inclusion test was performed using a microscope model BX51 from OLYMPUS.

Unless otherwise specified, the cleaning gases in the examples of the present application were purchased commercially, wherein the purity of each component in the cleaning gas was greater than 99.99%.

The processing method and the processing device of the embodiment can clean two surfaces of the seed crystal, can also only clean the growth surface of the seed crystal, and can be cleaned by a person skilled in the art according to the actual production requirement.

Example 1

Referring to fig. 1-5, the embodiment of the present application discloses a processing apparatus for improving seed crystal cleanliness, the apparatus includes a housing 10 and a seed crystal tray 20, a plurality of seed crystal inlets 14 are arranged on the side wall of the housing 10 along the axial direction of the housing 10, an air inlet 11 is arranged at the top or bottom of the housing 10, at least one air outlet 12 is correspondingly arranged on the side wall of the housing 10 near each seed crystal inlet 14, and the air outlet 12 and the air inlet 11 are located at the same side of the seed crystal inlet 14; the seed crystal tray 20 is used for fixing the seed crystal 21, the seed crystal tray 20 is inserted into the seed crystal inlet 14, so that the seed crystal 21 and the shell 10 on the side of the gas inlet 11 enclose a gas cleaning chamber 13, and the cleaning gas is blown into the gas cleaning chamber 13 from the gas inlet 11, flows to the surface of the seed crystal 21 closest to the gas inlet 11 and then flows out through the gas outlet 12.

The device can place a plurality of seed crystals 21 of treating to clean in casing 10, each seed crystal 21 all blocks between casing 10 and seed crystal tray 20, the homoenergetic encloses into gaseous clean room 13 with the casing 10 of air inlet 11 side, clean gas in the air supply 32 enters into in gaseous clean room 13 from air inlet 11, can carry out directional quantitative sweeping to the seed crystal 21 that is closest to air inlet 11, produce certain air current impact force to seed crystal 21, this impact force can blow off a large amount of granules of seed crystal 21 surface adhesion, and drive to gas outlet 12 and flow out, along with clean gas continuously sweep the seed crystal 21 surface and in time take away from gas outlet 12 with the granule that will sweep down, the granule of avoiding blowing down carries out secondary pollution and fish tail seed crystal 21 to seed crystal 21, reduce the remaining granule quantity in seed crystal 21 surface, improve seed crystal 21's cleanliness. After the seed crystal 21 is blown for a certain time, the seed crystal tray 20 for fixing the seed crystal 21 is taken down, the cleaned seed crystal 21 is taken out, the seed crystal tray 20 which does not carry the seed crystal 21 is sealed at the seed crystal inlet 14, so that the other seed crystal 21 close to the air inlet 11 and the shell 10 at the side of the air inlet 11 form the gas cleaning chamber 13, the next seed crystal 21 is cleaned until all the seed crystals 21 to be cleaned are cleaned, the cleaning efficiency of the seed crystal 21 can be improved, the seed crystals 21 can be cleaned by one-time installation, the manual operation is reduced, and the method is suitable for cleaning the seed crystals 21 on a large scale.

Specifically, when the air inlet 11 sets up in the casing 10 bottom, then every seed crystal entry 14 below all corresponds and sets up at least one gas outlet 12, when the air inlet 11 sets up at the top of casing 10, then every seed crystal entry 14 top all corresponds and sets up at least one gas outlet 12, clean gas enters into to gaseous clean room 13 from air inlet 11 and moves to seed crystal 21, after sweeping to seed crystal 21 surface back reverse motion to gas outlet 12 outflow, can make and maintain in gaseous clean room 13 under certain atmospheric pressure, play the cushioning effect to clean gas, avoid the air current too big, cause the impact force damage to seed crystal 21. Preferably, the gas inlet 11 is arranged at the central position of the bottom of the housing 10, so that the cleaning gas can be uniformly diffused to the gas cleaning chamber 13 when entering, the circumferential force of the cleaning gas reaching the seed crystal 21 is the same, the stress deviation of the seed crystal 21 is avoided, and the flatness of the seed crystal 21 is reduced.

In one embodiment, a heating coil 50 is sleeved outside the housing 10, and the heating coil 50 is disposed between the gas inlet 11 and the seed inlet 14 closest to the gas inlet 11 for heating the cleaning gas entering the gas cleaning chamber 13. The unheated cleaning gas has limited cleaning capability when blowing the seed crystal 21, and can not blow off some particles with large adhesive force, and the heated cleaning gas is transmitted to the surface of the seed crystal 21, so that the particles can be promoted to move, the adhesive force between the particles and the surface of the seed crystal 21 is reduced, the particles with large adhesive force on the surface of the seed crystal 21 can be further blown off, the particle residue on the surface of the seed crystal 21 is reduced, and the cleanliness of the seed crystal 21 is further improved; in addition, when the seed crystal 21 is blown and swept by the cleaning gas, the seed crystal 21 is heated uniformly, the stress in the seed crystal 21 can be reduced, the stress concentration of the seed crystal 21 caused by blowing and sweeping is avoided, the quality of the seed crystal 21 is improved, and the subsequent processing and production are facilitated.

Specifically, the housing 10 may be an integral structure or a separate structure, which is not limited to this. When casing 10 is structure as an organic whole, directly peg graft seed crystal tray 20 in seed crystal entry 14 department, can enclose into gaseous clean chamber, when casing 10 is high, can be with setting up to components of a whole that can function independently structure, casing 10 divide into shell construction and shell construction down, go up shell construction and seted up seed crystal entry 14, the shell construction outside cover is equipped with heating coil 50 down, peg graft a plurality of seed crystal trays 20 that have seed crystal 21 in the upper casing, place the upper casing on the lower casing again, seed crystal 21 encloses into gaseous clean room 13 with the upper casing and the lower casing below rather than.

Specifically, the air inlet 11 is arranged at the bottom of the shell 10, the air outlet 12 is arranged below each seed crystal inlet 14, under the heating of the heating coil 50, the high-temperature clean air moves upwards and does not generate convection with the cooler clean air which just enters the air cleaning chamber 13, the airflow stability of the clean air is ensured, the temperature is uniform when the clean air reaches the surface of the seed crystal 21, the seed crystal 21 can be cleaned continuously and efficiently, and the cleaning efficiency is improved.

In one embodiment, the housing 10 has a cylindrical structure, the diameter of the housing 10 is 50-500mm, and the heating coil 50 is disposed coaxially with the housing 10. Horizontal distance between each position of heating coil 50 and casing 10 equals, can improve the heating effect to clean gas, guarantee that clean gas thermally equivalent for the temperature when clean gas reachs seed crystal 21 surface is unanimous, can clean the whole surface of seed crystal 21, further improve the cleanliness on the whole surface of seed crystal 21, avoid the local granule quantity on seed crystal 21 surface to be too much, also be favorable to seed crystal 21 to release stress simultaneously, further improve the quality of seed crystal 21.

As an embodiment, the distance between the air inlet 11 and the seed crystal inlet 14 closest to the air inlet 11 is 50-1500mm, and the arrangement mode can ensure that the cleaning gas entering from the air inlet 11 can effectively clean the surface of the seed crystal 21, blow the particles attached to the surface of the seed crystal 21 to the air outlet 12 and flow out, and can also avoid overlarge gas impact force, so that the seed crystal 21 is damaged, and the breakage of the seed crystal 21 is avoided. Meanwhile, at the distance, the heating coil 50 can uniformly heat the cleaning gas in the gas cleaning chamber 13, so as to ensure the heating effect of the cleaning gas and improve the cleaning effect of the seed crystal 21, if the distance is too long, although the cleaning gas is heated more uniformly, the gas flow impact force generated when the cleaning gas reaches the surface of the seed crystal 21 is reduced, so as to reduce the cleaning effect of the seed crystal 21, if the distance is too short, the heating effect is not uniform, and the gas flow impact force is too large, so that the seed crystal 21 is easily damaged, the seed crystal 21 is deformed, and the surface quality of the seed crystal 21 is reduced, wherein the distance is preferably 500-.

As an implementation mode, the distance between two adjacent seed crystal inlets 14 is 10-60mm, the number of the seed crystal inlets 14 is 2-40, and the height of the seed crystal inlet 14 is 3-25 mm; preferably, the distance between two adjacent seed crystal inlets 14 is 10-30mm, the number of the seed crystal inlets 14 is 10-25, and the height of the seed crystal inlet 14 is 10-20 mm; more preferably, the distance between two adjacent seed crystal inlets 14 is 15-20mm, the number of the seed crystal inlets 14 is 10-15, and the height of the seed crystal inlet 14 is 10-15 mm. Clean gas gets into gaseous clean room 13 at air inlet 11, and along with the extension of clean gas migration distance, clean gas produces the air current impact force and reduces, weakens the clean effect of seed crystal 21, therefore the setting of the quantity and the interval of seed crystal entry 14 can once only place more seed crystal 21, improves the clean efficiency of seed crystal 21, ensures simultaneously that clean gas still has better cleaning power when cleaning the seed crystal 21 of furthest from air inlet 11. The thickness of the seed crystal 21 is 0.1-10mm, the height of the seed crystal inlet 14 is set to ensure that the opening area of the seed crystal inlet 14 is reduced as much as possible on the basis of putting the seed crystal 21 into the shell 10 and the seed crystal tray 20, and the leakage of cleaning gas from the insertion position of the seed crystal inlet 14 and the seed crystal tray 20 is avoided, so that the cleaning effect is reduced.

In one embodiment, the seed crystal inlet 14 is a bar-shaped slot horizontally extending along the radial direction of the housing 10, the seed crystal inlet 14 is in an arc shape, the radian of the radial cross section of the seed crystal inlet 14 is not less than 180 degrees, the shape of the seed crystal tray 20 is matched with the shape of the seed crystal inlet 14, and the inner diameter of the seed crystal tray 20 is consistent with the inner diameter of the housing 10. The seed crystal 21 is usually processed into a round shape, the seed crystal 21 is fixed on the seed crystal tray 20, the radian of the seed crystal inlet 14 is not less than 180 degrees, the seed crystal tray 20 is convenient to take and place, the seed crystal tray 20 is clamped with the diameter inlet, the outer wall of the seed crystal tray 20 is inosculated with the outer side wall of the shell 10, the seed crystal 21 can be stably placed between the seed crystal tray 20 and the shell 10, and the compactness of the device is improved.

As a preferred embodiment, the radian of the radial cross section of the seed crystal inlet 14 is 180 °, the radial radian of the seed crystal tray 20 is 180 °, at this time, the seed crystal tray 20 is half circular, a clamping groove is arranged at the position, close to the outer side wall, of the bottom edge of the seed crystal tray 20, the shape of the clamping groove is the same as that of the seed crystal tray 20, the width of the clamping groove is consistent with the thickness of the shell 10, the inner diameter of the clamping groove is consistent with that of the shell 10, the depth of the clamping groove is 5-30mm, the seed crystal tray 20 is clamped at the seed crystal inlet 14 through the clamping groove, the seed crystal tray 20 and the shell 10 can be ensured to be tightly combined, the sealing performance of the device is improved, and the outflow of cleaning gas from the position is avoided.

As an embodiment, a sealing gasket is arranged at the clamping connection part of the seed crystal inlet 14 and the seed crystal tray 20, so that the sealing performance between the seed crystal inlet 14 and the seed crystal tray 20 is improved, the seed crystal inlet 14 and the seed crystal tray 20 can be prevented from colliding, and the service life of the device is prolonged.

In one embodiment, a first annular groove 22 is provided on the inner sidewall of the seed tray 20, the first annular groove 22 is used for fixing the seed crystal 21, a second annular groove 15 is provided on the inner sidewall of the housing 10, the second annular groove 15 and the first annular groove 22 are provided at the same height, the seed tray 20 covers the seed inlet 14, and the first annular groove 22 abuts against the second annular groove 15 to fix the seed crystal 21. Preferably, first ring channel 22 sets up in being close to air inlet 11 one side, be convenient for first ring channel 22 and second ring channel 15 set up in same height, be convenient for place seed crystal 21 on same horizontal plane, when guaranteeing that clean gas cleans again, can avoid seed crystal 21 local atress too big, and then reduce the deformation of seed crystal 21 in clean process, be fixed in seed crystal 21 between first ring channel 22 and second ring channel 15, can increase the leakproofness of seed crystal 21 and casing 10 and seed crystal tray 20, first ring channel 22 and second ring channel 15 are around the circumference of seed crystal 21, can increase the steadiness of seed crystal 21, play certain guard action to the edge of seed crystal 21, prevent that seed crystal 21 from producing crackle or breakage in clean process, improve the yield of seed crystal 21.

In a preferred embodiment, the height of the first annular groove 22 and the second annular groove 15 is equal to the thickness of the seed crystal 21, preferably 0.1-10mm, and the seed crystal 21 is placed more stably in a mode that no shaking occurs when the seed crystal 21 is put in and taken out; the width of the first annular groove 22 and the width of the second annular groove 15 are 2-10mm, preferably 4-6mm, and the width is set to ensure effective cleaning of the surface of the seed crystal 21 and to ensure stabilization and protection of the seed crystal 21 against damage to the seed crystal 21.

In one embodiment, a handle 23 is provided on an outer side wall of the seed tray 20, and the handle 23 can be pulled to take out or put back the seed tray 20. The handle 23 is provided to facilitate the taking of the seed tray 20 and also to facilitate the pushing of the seed tray 20 to seal the seed inlet 14.

In one embodiment, the number of the gas outlets 12 corresponding to each seed crystal inlet 14 is multiple, and the multiple gas outlets 12 are arranged in at least a single row along the axial direction of the housing 10 and are uniformly distributed in the radial direction of the housing 10. When the air inlet 11 is arranged at the bottom of the shell 10, a group of air outlets 12 are corresponding to the side wall of the shell 10 below each seed crystal inlet 14, each group of air outlets 12 is multiple, clean air flows out of the air outlets 12 below the seed crystals 21, the air outlets 12 are at least arranged in a single row and are uniformly distributed in the radial direction of the shell 10, particles on the surfaces of the seed crystals 21 are driven by the clean air to flow out of the air outlets 12 on the periphery of the shell 10, the clean air is guaranteed not to be retained in the shell 10, the clean air with the particles is prevented from being driven to the surfaces of the seed crystals 21 by new clean air, and therefore the cleaning effect is reduced; furthermore, the air outlets 12 which are uniformly distributed along the radial direction of the shell 10 can ensure that the airflow generated by the cleaning gas in the circumferential direction of the seed crystal 21 is uniform, avoid uneven stress on the seed crystal 21 and improve the surface quality of the seed crystal 21. Preferably, the plurality of air outlets 12 are arranged in a single row along the circumferential direction of the housing 10, that is, one circle of air outlets 12 is arranged below each seed crystal inlet 14.

Specifically, the number of the air outlets 12 corresponding to each seed crystal inlet 14 is equal, so that the uniformity of the cleaning degree of the seed crystals 21 can be ensured when the seed crystals 21 are cleaned in batches, and the batch obtaining of the seed crystals 21 with consistent quality is facilitated. Preferably, the gas outlets 12 corresponding to each seed crystal inlet 14 are arranged in a row along the axial direction of the housing 10, so that the housing 10 can be conveniently formed, when the gas outlets 12 are staggered along the axial direction of the housing 10, the number of the gas outlets 12 below the seed crystals 21 is increased along with the increase of the cleaning number of the seed crystals 21, and the cleaning gas just entering the gas cleaning chamber 13 easily flows out from the gas outlets 12 arranged in a staggered manner, so that the cleaning effect of the seed crystals 21 is reduced.

In one embodiment, the distance between the gas outlet 12 and the seed crystal inlet 14 is 0-10mm, the number of gas outlets 12 per row is 2-60, preferably 3-30, and the opening area of each gas outlet 12 is 0.5cm²-15cm². The distance between the gas outlet 12 and the seed crystal inlet 14 is smaller than that between the gas inlet 11 and the seed crystal inletThe distance of the seed crystal inlet 14, the arrangement makes the cleaning gas blow to the surface of the seed crystal 21 when entering the gas cleaning chamber 13, avoids the cleaning gas which is not cleaned to the seed crystal 21 directly flowing out from the gas outlet 12, improves the effective utilization rate of the cleaning gas and the cleaning force to the seed crystal 21, reduces the waste of the cleaning gas and saves the cost. The number of the gas outlets 12 and the opening area of the gas outlets 12 are to ensure that the cleaning gas after cleaning the seed crystal 21 can smoothly bring the particles to the gas outlets 12 to flow out, so as to avoid overlarge air pressure in the shell 10, thereby damaging the seed crystal 21 and reducing the cleaning effect. The number of the gas outlets 12 is too small or the opening area is too small, so that the clean gas cannot flow out in time, the pressure of the gas cleaning chamber 13 is too large, the seed crystals 21 are easy to break, meanwhile, a certain number of particles float in the gas cleaning chamber 13, and along with the continuous entering of the clean gas in the gas inlet 11, the particles are driven to move towards the direction of the seed crystals 21 again, so that the secondary pollution of the seed crystals 21 is easy to cause, and the cleaning effect is reduced; the number of the gas outlets 12 is too large or the opening area is too large, so that the cleaning gas can easily and directly flow out from the gas outlets 12, and the seed crystals 21 cannot be effectively cleaned.

Preferably, the distance between the air outlets 12 and the seed crystal inlet 14 is 3-5mm, the number of the air outlets 12 in each row is 6-20, and the opening area of each air outlet 12 is 0.7cm²-10cm²The number of particles on the surface of the seed crystal 21 can be minimized and the deformation of the seed crystal 21 can be reduced. Specifically, the shape of the gas outlet 12 can be rectangular or circular, or polygonal, preferably circular, which is beneficial for the outflow of clean gas, when the gas outlet 12 is circular, the aperture of the gas outlet 12 is 5-20mm, preferably 10-15mm, which further improves the cleanliness of the seed crystal 21, and when the seed crystal 21 is used for preparing a silicon carbide crystal, the micro-tube and polytype of the silicon carbide crystal can be reduced, and the crystal dislocation is reduced.

In one embodiment, a support plate 30 is disposed in the housing 10 at a side close to the gas inlet 11, a side wall of the support plate 30 is attached to an inner wall of the housing 10, a gas nozzle 31 is disposed on the support plate 30, the gas nozzle 31 is communicated with the gas inlet 11, and the cleaning gas is blown into the gas cleaning chamber 13 through the gas inlet 11 and the gas nozzle 31 in sequence. Backup pad 30 and gas shower nozzle 31 set up in casing 10, enclose into gaseous clean room 13 between backup pad 30, seed crystal 21 and the casing 10, through the gaseous flow of clean of controller 34 control flow through gas shower nozzle 31, according to the seed crystal 21 surface particle how much and there is the position, adjust clean gaseous spouting angle in a flexible way through gas shower nozzle 31, avoid clean gaseous extravagant or have the phenomenon that clean dynamics is not enough, improve the practicality and the flexibility of device.

As a preferred embodiment, the support plate 30 can drive the gas nozzle 31 to lift and/or rotate, the lifting and the rotation of the support plate 30 are controlled by the motor 33, when the seed crystal 21 is cleaned, the cleaning effect is reduced along with the increase of the distance between the seed crystal 21 to be cleaned and the gas inlet 11, the lifting of the support plate 30 can adjust the distance between the gas nozzle 31 and the seed crystal 21, and further adjust the volume of the gas cleaning chamber 13, so that the cleaning gas can continuously and efficiently clean the seed crystal 21 when each seed crystal 21 is cleaned, and the cleanliness and the cleaning efficiency of the seed crystal 21 are improved; by the rotation of the supporting plate 30, the gas entering the gas cleaning chamber 13 through the gas nozzle 31 is blown to the surface of the seed crystal 21 at a certain angle, so that the particles with larger adhesive force can be conveniently blown off, the number of the particles on the surface of the seed crystal 21 is further reduced, and the cleanliness of the seed crystal 21 is improved; further, along with the rotation of backup pad 30, the air current that clean gas formed is rotatory air current, can prolong clean gas transmission to seed crystal 21's distance, play the cushioning effect to clean gas, it is too big to avoid clean gaseous impact force, thereby cause the damage of seed crystal 21, and simultaneously, rotatory air current makes clean gas can produce an even impact force to seed crystal 21's surface when arriving the seed crystal 21 surface, can reduce seed crystal 21's deformation, reduce seed crystal 21's gross thickness deviation, angularity and crookedness, improve seed crystal 21's face type quality, be used for growing brilliant in-process with seed crystal 21, also can improve the quality of crystal.

Specifically, the number of the motors 33 may be two, one controls the lifting of the support plate 30 and one controls the rotation of the support plate 30, and a motor having a function of controlling the lifting or the rotation in the prior art is adopted.

In one embodiment, at least one gas nozzle 31 is provided, at least one gas nozzle 31 is vertically disposed at the central position of the support plate 30, the rest of the gas nozzles 31 are uniformly distributed around the circumference of the gas nozzle 31 at the central position, the number of the gas nozzles 31 is more than one, so that the cleaning gas can generate enough impact force to clean the seed crystal 21, at least one gas nozzle 31 vertically disposed at the central position of the support plate 30 and the cleaning gas sprayed by the gas nozzles 31 at the central position and the circumference of the gas nozzles 31 can be simultaneously blown to the whole surface of the seed crystal 21, and the cleaning effect of the seed crystal 21 is further improved.

As an implementation mode, the distance between the gas nozzle 31 and the seed crystal 21 is 50-1500mm, the included angle between the rest gas nozzles 31 surrounding the gas nozzle 31 at the central position and the supporting plate 30 is 80-90 degrees, and the distance between the gas nozzle 31 and the seed crystal 21 is adjusted through the supporting plate 30 according to the number of particles on the surface of the seed crystal 21, so that the flexibility of the device is improved, and the consistency of the quality of the seed crystal 21 after cleaning is improved; the included angle between the rest of the gas nozzles 31 and the support plate 30 is 80-90 degrees, and the cleaning gas flowing out through the gas nozzles 31 can be blown to the circumferential direction of the seed crystal 21 along with the extension of the transmission distance and is matched with the gas nozzles 31 at the central position, so that the cleaning effect of the seed crystal 21 is further improved, and the particle number on the surface of the seed crystal 21 is reduced. Preferably, 7 gas nozzles 31 are provided, one gas nozzle 31 is vertically arranged at the center of the support plate 30, the included angle between the rest 6 gas nozzles 31 and the support plate 30 is 88 degrees, in the cleaning process, the gas flow can uniformly blow and sweep the surface of the seed crystal 21, the number of particles on the surface of the seed crystal 21 is reduced, the deformation of the seed crystal 21 is reduced, and the surface shape quality of the seed crystal 21 is improved.

Example 2

This example provides a method of improving the cleanliness of a seed crystal prepared from a single cutting, grinding and polishing process using the apparatus of any one of the embodiments of example 1, comprising the steps of:

a preparation stage: fixing a plurality of seed crystals to be cleaned in the shell;

a cleaning stage: and opening the air inlet, heating the cleaning gas to the temperature of 150-.

Preferably, the treatment method for improving the cleanliness of the seed crystal comprises the following steps:

(1) respectively fixing a plurality of seed crystals to be cleaned on a plurality of seed crystal trays, wherein each seed crystal tray is inserted into one seed crystal inlet so that the seed crystals are fixed between the shell and the seed crystal trays, and the growth surfaces of the seed crystals face to the air inlet;

(2) the supporting plate is lifted to ensure that the distance between the gas nozzle and the seed crystal to be cleaned closest to the gas inlet is 50-1500mm, and the pressure of the gas cleaning chamber is pumped to 10^-6mbar for 1-3 h; then continuously introducing inert gas, adjusting the pressure in the gas cleaning chamber to 10-100mba, and opening the heating coil to ensure that the temperature in the gas cleaning chamber is 150-;

(3) opening the gas inlet and the gas nozzle to enable the flow of the cleaning gas entering the gas cleaning chamber to be 0.1-20SLM, rotating the support plate, and cleaning the crystal growth face of the seed crystal to be cleaned for at least 30 min;

(4) closing the air inlet and the gas nozzle after cleaning, stopping rotating the support plate, pulling a handle of the seed crystal tray, taking the cleaned seed crystal off the seed crystal tray, inserting the seed crystal tray which does not carry the seed crystal into the inlet of the seed crystal, enclosing the seed crystal to be cleaned closest to the air inlet and the shell again to form a gas cleaning chamber, and moving the support plate 10-60mm towards the seed crystal to be cleaned;

(5) and (5) repeating the steps (3) and (4) until all the seed crystals to be cleaned are cleaned completely.

The flow rate of the cleaning gas is expressed in SLM (standard liquid per minute) and represents a gas flow rate in a standard state, for example, a gas flow rate of 1L/min in a standard state of 1 SLM.

The cleaning gas is at least two or more of hydrogen, methane, ethane, monosilane, disilane, helium and argon, preferably, the cleaning gas comprises 35-70% of hydrogen, 0-40% of methane, ethane, monosilane and/or disilane and 0-30% of helium and/or argon, and the "%" represents volume percent.

As a preferred embodiment, the cleaning in step (3) is divided into a first cleaning stage and a second cleaning stage,

the temperature of the first cleaning stage is 50-150 ℃ lower than the temperature of the second cleaning stage, the flow rate of the cleaning gas in the first cleaning stage is 1-2SLM less than the flow rate of the cleaning gas in the second cleaning stage, and the purging time in the first cleaning stage is longer than the purging time in the second cleaning stage.

The apparatus used in this processing method is a preferred embodiment of the present invention, referring to fig. 1.

The seed crystal 1# -6# and the comparative seed crystal D1# -D2# were cleaned according to the above treatment method, wherein the support plate was moved to a distance of 700mm from the growth surface of the seed crystal in step (2) before cleaning, and the differences between the specific treatment method and the above method are shown in Table 1.

TABLE 1

The prepared seed crystal 1# -6# and the comparative seed crystal D1# -D2# were tested for grain number, element content, surface roughness, Total Thickness Variation (TTV), warpage (Bow), and Bow (Warp) in combination with Table 1, and the test results are shown in Table 2, where the element content in Table 2 refers to the total content of Ca, Fe, Cu, Zn, V, Mn, Cr, Al, Na, Ti, Ni, K, Pb, and Ru elements. Wherein the number of particles having a particle diameter in the range of 0.5 μm to 1 μm means the number of particles having a particle diameter of more than 0.5 μm, excluding 0.5 μm, and a particle diameter of 1 μm or less; the particle size is 0.1-0.5 μm, which means the particle size is larger than 0.1 μm, excluding 0.1 μm, and is less than or equal to 0.5 μm; the particle size is 0.02 μm to 0.1 μm, which means that the particle size is larger than 0.02 μm, excluding 0.02 μm, and the particle size is 0.1 μm or smaller.

TABLE 2

Example 3

The seed crystal treated in the above example 2 is used for preparing the silicon carbide single crystal, and the preparation method comprises the following steps:

(1) putting seed crystals and silicon carbide raw materials into a crystal growth furnace, sealing, vacuumizing the crystal growth furnace and introducing inert gas to remove impurities;

(2) introducing high-purity inert gas into the furnace body to increase the pressure in the crystal growth furnace to 1 × 10⁴-1×10⁵Pa, continuously introducing high-purity inert gas, keeping the pressure unchanged, and controlling the temperature in the crystal growth furnace to rise to 2000-2300K;

(3) controlling the crystal growth temperature to be 2200K-2800K, the crystal growth pressure to be 500-3000Pa, and keeping the time for 50-100h to obtain the silicon carbide single crystal No. 1-6 and the comparative silicon carbide single crystal No. D1-D2.

The prepared silicon carbide single crystal 1# -6# and the comparative silicon carbide single crystal D1# -D2# were tested for structural defects such as micropipes, polytypes, dislocations including threading dislocations (TSD), edge dislocations (TED), plane dislocations (BPD), inclusions, etc., and the test results are shown in Table 3.

TABLE 3

As can be seen from the analysis of the data in tables 1 to 3, the flow rate of the cleaning gas, the heating temperature of the cleaning gas, the rotation rate of the support plate, and the distance between the support plate and the seed crystal affect the quality of the cleaned seed crystal, and the quality of the seed crystal affects the quality of the silicon carbide single crystal under the same growth condition. The seed crystal 1# -6# cleaned by the treatment method has lower particle number and element content, and the surface quality is good. According to the seed crystals 1#, 3#, 5# and D1#, the heating temperature of the cleaning gas has a large influence on the cleaning quality of the seed crystals, and the temperature of the cleaning gas in the second cleaning stage is increased, so that the particle number of the growth surface of the seed crystals can be further reduced, and the cleanness of the growth surface of the seed crystals can be improved; as can be known from the seed crystals 1# and 4#, the rotation speed of the support plate influences the cleaning quality of the growth surface of the seed crystal, the rotation speed is too high, the cleaning gas easily generates vortex, particles cannot be effectively removed, and the surface quality is poor; from the seed crystal 1# and D2#, it can be known that the gas flow of the cleaning gas has a large influence on the cleaning quality of the seed crystal, and the use of the large gas flow can cause that the cleaning gas can not bring the particles to the gas outlet to flow out, so that the secondary pollution of the seed crystal is easily caused, and the surface quality of the seed crystal is deteriorated; according to the seed crystal 1# and the seed crystal 6# which are used for cleaning, the volume of the gas cleaning chamber is changed in the cleaning process, the cleaning quality of the seed crystal can be influenced by the heating temperature and the flow of the cleaning gas, the volume of the gas cleaning chamber is reduced in the cleaning later period, and the cleanliness of the seed crystal can be further improved by increasing the heating temperature and the flow of the cleaning gas.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A processing apparatus for improving the cleanliness of a seed crystal, comprising:

2. The apparatus as claimed in claim 1, wherein the distance between the gas inlet and the seed crystal inlet closest to the gas inlet is 50-1500mm, preferably 500-1000 mm; and/or

The distance between every two adjacent seed crystal inlets is 10-60mm, the number of the seed crystal inlets is 2-40, and the height of each seed crystal inlet is 3-25 mm;

preferably, the distance between two adjacent seed crystal inlets is 10-30mm, the number of the seed crystal inlets is 10-15, and the height of the seed crystal inlet is 10-15 mm.

3. The apparatus as claimed in claim 2, wherein the number of the gas outlets corresponding to each seed crystal inlet is plural, and the plural gas outlets are arranged in at least a single row along the axial direction of the housing and are uniformly distributed in the radial direction of the housing.

4. The apparatus as claimed in claim 1, wherein the number of the air outlets corresponding to each seed crystal inlet is equal, and the air outlets corresponding to a plurality of seed crystal inlets are arranged in a row along the axial direction of the housing;

preferably, the distance between the air outlets and the seed crystal inlets is 0-10mm, the number of the air outlets in each row is 2-60,preferably 3-30, and the opening area of each air outlet is 0.5cm²-15cm²。

5. The apparatus according to any one of claims 1 to 4, wherein a support plate is provided in the housing on a side thereof adjacent to the gas inlet, a side wall of the support plate is attached to an inner wall of the housing, a gas shower is provided on the support plate, the gas shower is communicated with the gas inlet, and the cleaning gas is blown into the gas cleaning chamber through the gas inlet and the gas shower in this order;

6. The apparatus of claim 5, wherein the number of the gas showers is at least one, at least one of the gas showers is vertically disposed at a central position of the support plate, and the rest of the gas showers are uniformly distributed around a circumference of the gas showerhead at the central position;

7. The apparatus according to any one of claims 1 to 4, wherein the seed crystal inlet is provided as a strip-shaped slit horizontally extending in a radial direction of the housing;

preferably, the shell is of a cylindrical structure, the seed crystal inlet is arc-shaped, the radian of the radial cross section of the seed crystal inlet is not less than 180 degrees, the shape of the seed crystal tray is matched with that of the seed crystal inlet, and the inner diameter of the seed crystal tray is consistent with that of the shell.

8. The apparatus as claimed in claim 7, wherein a raised first annular groove is provided on the inner side wall of the seed tray for fixing the seed crystal; and

9. A process for improving the cleanliness of a seed crystal, which is carried out using the apparatus according to any one of claims 1 to 8, wherein a support plate having a gas shower head is provided in the housing, the process comprising the steps of:

s1: fixing a plurality of seed crystals to be cleaned in the shell;

s4: repeating the steps S2 and S3 until the seed crystal to be cleaned is completely cleaned.

10. The method of claim 9, wherein a heating coil is sleeved outside the housing;

in the step S2, the heating coil is turned on to heat the cleaning gas entering the gas cleaning chamber, and the heating temperature of the cleaning gas is 150-.