CN114561695B

CN114561695B - Bonding device and bonding method for seed crystal and seed crystal holder

Info

Publication number: CN114561695B
Application number: CN202210211679.3A
Authority: CN
Inventors: 程章勇; 张云伟; 何丽娟; 杨丽雯; 李天运
Original assignee: Hefei Century Gold Core Semiconductor Co ltd
Current assignee: Hefei Century Gold Core Semiconductor Co ltd
Priority date: 2022-03-04
Filing date: 2022-03-04
Publication date: 2023-07-07
Anticipated expiration: 2042-03-04
Also published as: CN114561695A

Abstract

The application provides a bonding device and bonding method of seed crystal and seed crystal support, include: the device comprises a chamber, a heating module, a seed crystal holder and a pressing module, wherein the heating module, the seed crystal holder and the pressing module are positioned in the chamber; wherein the heating module is positioned at the bottom of the cavity; the seed crystal support is positioned at one side of the heating module, which is away from the bottom of the cavity, and is used for fixing seed crystals, and the seed crystals are fixed at one side of the seed crystal support, which is away from the heating module; the pressing module is positioned at one side of the seed crystal support, which is away from the heating module, and is used for pressing towards the seed crystal so as to fix the seed crystal and the seed crystal support in a fitting way; the pressing module comprises a 1 st pressing unit to an n-th pressing unit, wherein n is a positive integer greater than 1, and the n-th pressing unit surrounds the n-1-th pressing unit; the pressing module is used for sequentially controlling the 1 st pressing unit to the n th pressing unit to press the seed crystal. According to the bonding device and the bonding method provided by the technical scheme of the invention, the defect structure of the microcavity between the seed crystal and the seed crystal support is reduced, and the bonding quality of the seed crystal and the seed crystal support is improved.

Description

Bonding device and bonding method for seed crystal and seed crystal holder

Technical Field

The invention relates to the field of crystal growth, in particular to a bonding device and a bonding method of seed crystals and a seed crystal holder.

Background

Silicon carbide (SiC) has been rapidly developed in recent decades as a wide band gap semiconductor material, and compared with other semiconductor materials, silicon carbide has advantages of wide band gap, high thermal conductivity, high carrier saturation mobility, high power density, and the like, and is widely used in related fields such as semiconductors.

At present, the method for obtaining the silicon carbide crystal is mainly a physical vapor transmission method, a SiC raw material, a seed crystal and a seed crystal holder (a part for fixing the seed crystal) are usually placed in a crucible, and the technological conditions are controlled so that the SiC raw material sublimates to the seed crystal to be piled up and grown to form the silicon carbide crystal. Wherein, fixing the seed crystal on the seed crystal support is a basic condition for realizing the growth of the silicon carbide crystal, and is also a key factor influencing the crystal growth process and the crystallization quality.

In the prior art, most of adhesives are used for fixing the seed crystal and the seed crystal support, but partial bubbles generated by uneven sizing, incapability of smoothly removing gas-phase substances generated by physical volatilization and chemical reaction in the high-temperature process of glue between the seed crystal and the seed crystal support and microporous cavity defect structures such as isolated point cavities, linear cavities or flaky cavities between the seed crystal and the seed crystal support caused by neglecting the change of the spacing between the seed crystal and the seed crystal support influence the bonding effect of the seed crystal and the seed crystal support, hexagonal cavities, micropipes and the like are easy to appear in the silicon carbide crystal grown by the adhesive, and even the seed crystal falls off in the growth process when serious. In addition, the above phenomenon is more pronounced with increasing crystal size (e.g., 8 inch silicon carbide crystals). Therefore, how to achieve high quality bonding between the seed crystal and the seed holder is one of the problems to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the present application provides a bonding apparatus and a bonding method for a seed crystal and a seed crystal holder, which improve the bonding quality of the seed crystal and the seed crystal holder.

In order to achieve the above purpose, the present invention provides the following technical solutions:

the present application provides in a first aspect a bonding apparatus for seed crystal and seed holder comprising:

the device comprises a chamber, a heating module, a seed crystal holder and a pressing module, wherein the heating module, the seed crystal holder and the pressing module are positioned in the chamber; wherein,,

the heating module is positioned at the bottom of the cavity;

the seed crystal support is positioned at one side of the heating module, which is away from the bottom of the cavity, and is used for fixing seed crystals, and the seed crystals are fixed at one side of the seed crystal support, which is away from the heating module;

the pressing module is positioned at one side of the seed crystal support, which is away from the heating module, and is used for pressing towards the seed crystal so as to ensure that the seed crystal is attached and fixed with the seed crystal support; the pressing module comprises a 1 st pressing unit to an n-th pressing unit, wherein n is a positive integer greater than 1, and the n-th pressing unit surrounds the n-1-th pressing unit; the pressing module is used for sequentially controlling the 1 st pressing unit to the n th pressing unit to press the seed crystal.

Preferably, the center of the 1 st pressing unit corresponds to the centers of the seed crystal and the seed crystal holder;

further comprises: wedge-shaped gaskets and drive assemblies; before the 1 st pressing unit presses the seed crystal, the driving assembly is used for controlling the wedge-shaped gasket to be positioned between the edge of the seed crystal support and the edge of the seed crystal, and the thickness of the wedge-shaped gasket is sequentially increased in the direction of the center of the seed crystal support towards the edge; the driving assembly is used for controlling the wedge-shaped gasket to be pulled away from the area between the seed crystal holder and the seed crystal before the nth pressing unit presses the seed crystal.

Preferably, the chamber comprises:

a vent for providing a shielding gas for the chamber to ensure that the seed holder, the seed crystal and the adhesive are not oxidized while maintaining the pressure of the chamber at a target value during high-temperature heating;

and the pumping port is used for pumping gas in the cavity so as to prevent the seed crystal holder, the seed crystal and the adhesive from being oxidized before heating and simultaneously keep the pressure of the cavity at a target value.

Preferably, the 1 st pressing unit is cylindrical, and the n-th pressing unit is hollow cylindrical.

Preferably, an adhesive is arranged between the seed crystal holder and the seed crystal.

The present application also provides in a second aspect a method of bonding a seed crystal to a seed holder, the seed crystal having a first surface, the seed holder having a second surface, the first surface being adhesively secured to the second surface, the method comprising:

acquiring surface morphology information of the first surface and surface morphology information of the second surface;

determining a relative fitting mode of the first surface and the second surface based on the surface morphology information of the first surface and the surface morphology information of the second surface;

after the second surface is coated with an adhesive, the second surface is placed in the bonding device according to any one of the first aspect, and the seed holder and the seed crystal are bonded and fixed based on the relative bonding mode.

Preferably, the method for bonding and fixing the seed crystal holder coated with the adhesive and the seed crystal in the bonding device comprises the following steps:

placing the seed crystal support coated with the adhesive on a heating module of the bonding device for heating so as to remove bubbles and volatile substances in the adhesive;

performing pre-bonding fixation, comprising: sequentially controlling the 1 st pressing unit to the n th pressing unit to press the seed crystal through a pressing module of the bonding device, wherein the pressing force formed by the m-th pressing unit is greater than the pressing force formed by the m+1 th pressing unit; m is a positive integer less than n;

After the pre-bonding and fixing are completed, homogenizing and forming are carried out on the surface of one side of the seed crystal, which is away from the seed crystal holder, and the method comprises the following steps: and the pressure applied to the seed crystal by the 1 st pressure applying unit to the n th pressure applying unit is controlled by the pressure applying module of the bonding device in sequence, and the pressure formed by the m-th pressure applying unit is equal to the pressure formed by the m+1-th pressure applying unit.

Preferably, the method for obtaining the surface topography information of the first surface and the surface topography information of the second surface includes:

setting the first surface and the second surface as sampling surfaces, and collecting coordinate information of a plurality of sampling points on the sampling surfaces

Wherein the center coordinates of the sampling surface are (0, 0), the center coordinates of the sampling surface are the origin of a three-dimensional coordinate system comprising the three-dimensional coordinate systemThe X axis, the Y axis and the Z axis perpendicular to the sampling surface are perpendicular to each other in the sampling surface, the planes of the X axis and the Y axis are XY planes, and the projection point of the sampling point on the XY planes is P; r is the distance of P from the center of the sampling surface,

and z is the distance between the sampling point and the XY plane, wherein the angle is the angle between the connecting line of P and the center of the sampling surface and the positive direction of the X axis.

Preferably, determining the relative fit of the first surface and the second surface includes:

establishing a model of the seed crystal and the seed crystal holder;

the model center of the first surface and the model center of the second surface are oppositely overlapped and then attached;

fixing the model of the seed crystal support so as to rotate the model of the seed crystal based on a set step value through the center of the model of the seed crystal and the rotating shaft of the center of the model of the seed crystal support, and collecting the number of contact points of the model of the first surface and the model of the second surface under different rotating angles;

and determining the relative fitting mode based on the state when the number of contact points is the largest between the model of the first surface and the model of the second surface.

Preferably, the adhesive comprises epoxy resin, silicone, and isopropyl alcohol.

According to the bonding device and the bonding method provided by the technical scheme of the invention, the 1 st pressing unit to the n th pressing unit are controlled to press the seed crystal through the pressing module in sequence, so that air in a cavity between the seed crystal and the seed crystal support escapes from inside to outside, a micro-cavity defect structure between the seed crystal and the seed crystal support is reduced, and the bonding quality of the seed crystal and the seed crystal support is improved.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present application, and that other drawings may be obtained according to the provided drawings without inventive effort to a person skilled in the art.

The structures, proportions, sizes, etc. shown in the drawings are shown only in connection with the present disclosure, and should not be construed as limiting the scope of the invention, since any modification, variation in proportions, or adjustment of the size, which would otherwise be used by those skilled in the art, would not have the essential significance of the present disclosure, would not affect the efficacy or otherwise be achieved, and would still fall within the scope of the present disclosure.

FIG. 1 is a schematic diagram of a physical vapor transport method according to an embodiment of the present disclosure;

fig. 2 is a schematic structural view of an adhesive device according to an embodiment of the present application;

FIG. 3 is a schematic side view of a wedge gasket according to an embodiment of the present application;

FIG. 4 is a schematic top view of a pressing module according to an embodiment of the present disclosure;

FIG. 5 is a schematic top view of another pressure application module according to an embodiment of the present disclosure;

FIG. 6 is a schematic diagram illustrating steps of an adhesion method according to an embodiment of the present disclosure;

FIG. 7 is a schematic diagram of a structure for bonding a seed crystal to a seed crystal holder according to an embodiment of the present disclosure;

FIG. 8 is a schematic view of another embodiment of a bonding method of a seed crystal and a seed holder;

fig. 9 is a schematic structural view of another bonding method of a seed crystal and a seed crystal holder according to an embodiment of the present application.

Detailed Description

Embodiments of the present application will now be described more fully hereinafter with reference to the accompanying drawings, in which it is shown, and in which it is evident that the embodiments described are exemplary only some, and not all embodiments of the application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

As described in the background art, the currently mainstream silicon carbide crystal growth method is mainly a Physical Vapor Transport (PVT) method, and the principle of the method is shown in fig. 1, where fig. 1 is a growth schematic diagram of the physical vapor transport method provided in the embodiment of the present application, and the apparatus in fig. 1 includes:

A growth chamber 1 for growing silicon carbide crystals, the growth chamber 1 typically being a graphite crucible;

a seed holder 2 positioned at the top of the growth chamber 1 for holding a seed crystal 3.

In the physical vapor transmission method, a silicon carbide raw material for growing a silicon carbide crystal is placed at the bottom of a growth chamber 1, a seed crystal 3 is fixed on a seed crystal holder 2, and after the silicon carbide raw material sublimates, the silicon carbide raw material rises to the seed crystal 3 positioned at the top of the growth chamber 1 for stacking growth by controlling the temperature, the pressure and other relevant conditions in the growth chamber 1, so that the silicon carbide crystal is obtained.

In the above-described growth method, the crystal growth of silicon carbide is affected by numerous factors such as temperature, pressure, temperature field distribution, and purity of raw materials, and how to fix the seed crystal 3 on the top of the growth chamber 1 is a basic condition for achieving the crystal growth of silicon carbide, and is also a key factor affecting the crystal growth process and crystallization.

The current method for fixing the seed crystal 3 and the seed crystal holder 2 is a bonding process, the bonding process is generally glue-bonding-curing, so that the seed crystal 3 and the seed crystal holder 2 are fixed, but in the actual process, the bonding thickness of the seed crystal 3 and the seed crystal holder 2 is uneven due to uneven coating of an adhesive, so that micro-cavities are formed between the seed crystal 3 and the seed crystal holder 2, meanwhile, the flatness of the contact surface of the seed crystal 3 and the seed crystal holder 2 is different, and an untouched part possibly exists between the seed crystal 3 and the seed crystal holder 2, so that cavities can be formed in the bonding process, and gas in the cavities is difficult to remove. In addition, when the adhesive is cured at a high temperature, the gas retained in the cavity between the seed crystal 3 and the seed crystal holder 2 expands due to the temperature rise, and meanwhile, the adhesive generates a certain amount of gas under the high temperature condition, so that the gas generated by the adhesive forms a new cavity or is collected to the original cavity, the number and the volume of the cavity are increased, and when more gas is retained between the seed crystal holder 2 and the seed crystal 3, a linear cavity is possibly generated when the gas rapidly escapes outwards due to larger local air pressure.

The presence of the cavity may lead to a decrease in the adhesion between the seed crystal 3 and the seed holder 2 and may even lead to the seed crystal 3 falling off during crystal growth. In addition, as the heat transfer efficiency of the bonding area of the seed crystal 3 and the seed crystal holder 2 is different from that of the cavity area, the seed crystal 3 is corroded in the back direction in the cavity area, so that defects such as micropipes and hexagonal cavities are formed, and the crystal quality is seriously affected. The larger the size of the seed crystal 3, the higher the requirement for the seed crystal bonding process. The more difficult it is, the more defects the seed crystal 3 has without a good seed crystal bonding process, and the more serious the effect on crystal quality is.

The technical scheme of the application provides a bonding device and a bonding method for seed crystals and seed crystal holders based on the problems, so that cavity defects between the seed crystals and the seed crystal holders are reduced, and bonding quality between the seed crystals and the seed crystal holders is further improved.

Referring to fig. 2, fig. 2 is a schematic structural diagram of an adhesive device according to an embodiment of the present application. The bonding device comprises:

a chamber 1, and a heating module 4, a seed crystal holder 2 and a pressurizing module 5 which are positioned in the chamber 1; wherein,,

the heating module 4 is located at the bottom of the chamber 1.

The seed crystal support 2 is located on one side of the heating module 4, which is away from the bottom of the cavity 1, the seed crystal support 2 is used for fixing the seed crystal 3, and the seed crystal 3 is fixed on one side of the seed crystal 3, which is away from the heating module 4.

The pressing module 5 is positioned on one side of the seed crystal holder 2 away from the heating module 4 and is used for pressing the seed crystal 3 so as to enable the seed crystal 3 to be attached and fixed with the seed crystal holder 2; the pressing module 5 comprises 1 st pressing units 51 to n-th pressing units, wherein n is a positive integer greater than 1, and the n-th pressing units surround the n-1-th pressing units; the pressing module 5 is used for sequentially controlling the 1 st pressing unit 51 to the n th pressing unit to press the seed crystal 3.

According to the bonding device, the 1 st pressing unit 51 to the n-th pressing unit are controlled to press the seed crystal 3 through the pressing module 5, so that the pressure intensity from the corresponding area of the 1 st pressing unit 51 to the corresponding area of the n-th pressing unit is gradually reduced, and then air in a cavity between the seed crystal 3 and the seed crystal support 2 escapes, and defects caused by the existence of the cavity are reduced. In addition, the bonding device can heat the bonding agent between the seed crystal holder 2 and the seed crystal 3, remove gas and volatile substances in the bonding agent, and the heating can change the physical state and chemical property of the bonding agent so as to improve the bonding property of the bonding agent, thereby improving the bonding quality of the seed crystal 3 and the seed crystal holder 2.

In order that the above-recited objects, features and advantages of the present application will become more readily apparent, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings.

In an embodiment of the present application, referring to fig. 2, the center of the 1 st pressing unit 51 corresponds to the center of the seed crystal 3 and the seed crystal holder 2; the bonding device further includes: wedge pad 6 and drive assembly; before the 1 st pressing unit 51 presses the seed crystal 3, the driving assembly is used for controlling the wedge-shaped gasket 6 to be positioned between the edge of the seed crystal holder 2 and the edge of the seed crystal 3, and the thickness of the wedge-shaped gasket 6 is sequentially increased in the direction of the center of the seed crystal holder 2 towards the edge; the driving assembly is used for controlling the wedge-shaped gasket 6 to be pulled out of the area between the seed holder 2 and the seed crystal 3 before the nth pressing unit presses the seed crystal 3.

After the 1 st pressing unit 51 presses the seed crystal 3, the driving assembly controls the wedge-shaped gasket 6 to slowly move from the center toward the edge until the wedge-shaped gasket 6 is pulled away from the area between the seed crystal holder 2 and the seed crystal 3 before the n-th pressing unit presses the seed crystal 3.

It should be noted that, as shown in fig. 3, fig. 3 is a schematic side view of a wedge-shaped gasket provided in the embodiment of the present application, where the wedge-shaped gasket 6 contacts with the edge of the seed holder 2, and does not form a complete surface contact with the seed holder 2, so as to prevent the adhesive coated on the surface of the seed holder 2 from being damaged.

The bonding device controls the height difference between the seed crystal 3 and the seed crystal support 2 through the wedge-shaped gasket 6 and the driving assembly, so that silicon carbide is prevented from being cracked due to overlarge external torque in the pressing process, and gaps are formed between the wedge-shaped gasket 6 and the seed crystal 3 and between the wedge-shaped gasket 6 and the seed crystal support 2 when the wedge-shaped gasket 6 moves, and then gas in the bonding agent can smoothly escape.

In addition, the chamber 1 includes: and a vent 71 for supplying a shielding gas to the chamber 1 to ensure that the seed holder 2, the seed crystal 3, and the adhesive are not oxidized while maintaining the pressure of the chamber 1 at a target value during high-temperature heating.

An extraction port 72 for extracting gas from the chamber 1 to prevent oxidation of the seed holder 2, the seed crystal 3, and the adhesive before heating, while maintaining the pressure of the chamber 1 at a target value.

In the embodiment of the present application, the pumping hole 72 and the vent hole 71 are controlled, so that the pressure in the chamber 1 is controlled to be kept at the target value. In addition, the control vent 71 supplies the chamber 1 with a shielding gas, so that the seed crystal 3, the seed crystal holder 2 and the adhesive in the chamber 1 can be protected from oxidation; accordingly, the gas in the chamber 1 is pumped through the pumping port 72, and oxidation of the seed crystal 3, the seed holder 2, and the adhesive can be prevented.

When needing to be described, the shielding gas comprises argon, nitrogen, argon and nitrogen mixed gas, and the like, so that the chemical reaction of the heated seed crystal support 3, the heated seed crystal 2 and the adhesive with oxygen in the air in the bonding and curing process of the seed crystal 3 and the seed crystal support 2 can be avoided, and the bonding quality of the seed crystal 2 and the seed crystal support 3 is further affected. In the actual process, the gas which does not react with the raw materials can be regarded as a protective gas, and the protective gas is within the protection scope of the application, and the application is not limited to the protection scope.

In addition, the chamber 1 further includes: and the cavity pressure control system is used for controlling the cavity pressure of the cavity 1. The cavity pressure control system includes a pressure control pump connected to the extraction port 72.

The cavity pressure control system can enable the cavity 1 to be negative pressure, so that proper pressure difference exists between the seed crystal 3 and the seed crystal support 2, gas which is directly pressed by the seed crystal 3 and the seed crystal support 2 can escape conveniently, and the possibility of gas aggregation is reduced. In addition, the chamber 1 comprises: and a hydraulic control system for controlling the application pressures of the 1 st to nth pressing units 51 to 51.

Optionally, in this embodiment, the cavity 1 is a structure of an upper cover 12 and a lower cover 11, and during a process, the upper cover 12 and the lower cover 11 form a closed cavity 1 by fastening a screw 8, and the cavity 1 is easy to take seed crystal and the seed crystal holder 2, and is beneficial to repair and maintenance of the bonding device. In other embodiments, the chamber 1 may be an integrated closed chamber 1, which is within the scope of the present application.

Optionally, the seed crystal holder 2 is graphite, which is favorable for the escape of gas between the seed crystal 3 and the seed crystal holder 2. In addition, the vacuum area is arranged on one side of the seed crystal holder 2 away from the seed crystal 3, so that the escape of gas between the seed crystal 3 and the seed crystal holder 2 is further facilitated.

In the embodiment of the present application, as shown in fig. 4, fig. 4 is a schematic top view of a pressing module provided in the embodiment of the present application, the 1 st pressing unit 51 is in the shape of a cylinder, and the n-th pressing unit is in the shape of a hollow cylinder, wherein the end of the cylinder and the end of the hollow cylinder form a pressing surface as shown in fig. 4. In other embodiments, the 1 st pressing unit 51 is not limited to a cylinder, and may have other shapes, and similarly, the shape of the n-th pressing unit is not limited to a hollow cylinder, and may have other shapes, so as to satisfy the shape surrounding the 1 st pressing unit 51.

In addition, in other embodiments, the pressing surface of the pressing device 5 may be a complete surface formed by a plurality of pressing units, as shown in fig. 5, fig. 5 is a schematic top view of another pressing module according to an embodiment of the present invention, where the pressing units are in a prism shape, and the ends of the prism form the pressing surface shown in fig. 5, where there is no space between the prism ends. The prism is not limited to a cube, a rectangular parallelepiped, a prism, a trapezoid, or the like, and the present application is not limited thereto.

In the embodiment of the present application, when the 1 st pressing unit 51 is in the shape of a cylinder and the n-th pressing unit is in the shape of a hollow cylinder, the wedge-shaped spacer 6 is an annular wedge-shaped ring. The annular wedge ring is made up of a plurality of wedge members to facilitate movement from the center toward the edges.

It should be noted that, in all embodiments of the present application, the 1 st pressing unit 51 to the n-th pressing unit may apply different pressures to the seed crystal 3, respectively, for example, when the pressing module 5 has 4 pressing units, as shown in fig. 2, the 1 st pressing unit 51 provides a pressure of 11kg, the 2 nd pressing unit 52 provides a pressure of 19kg, the 3 rd pressing unit 53 provides a pressure of 27kg, and the 4 th pressing unit 54 provides a pressure of 35 kg. Similarly, the 1 st to n-th pressing units 51 to 51 apply the same pressure to the seed crystal 3, and the description thereof will not be repeated.

The seed crystal 3 and the seed crystal holder 2 are fixed by an adhesive, namely, the adhesive is arranged between the seed crystal holder 2 and the seed crystal 3. Alternatively, the adhesive may be applied only to the surface of the seed holder 2 facing the seed crystal 3, or may be applied to both the surface of the seed holder 2 facing the seed crystal 3 and the surface of the seed crystal 3 facing the seed holder 2. In other embodiments, the adhesive may be applied only to the surface of the seed crystal 3 facing the seed holder 2.

The following describes the bonding method provided in the embodiments of the present application, and the bonding method described below may be referred to in correspondence with the bonding apparatus described above.

Correspondingly, the application also provides a bonding method of the seed crystal and the seed crystal holder, and referring to fig. 6, fig. 6 is a schematic step diagram of the bonding method according to the embodiment of the application. The seed crystal 3 has a first surface 31, the seed holder 2 has a second surface 21, the first surface 31 and the second surface 21 are bonded and fixed, and the bonding method comprises:

step S110: surface topography information of the first surface 31 and surface topography information of the second surface 21 are acquired.

Wherein the surface topography information comprises: the total thickness variation TTV, bow, warp Wrap, local thickness variation LTV, etc. of the seed crystal 3 and the seed holder 2.

Step S120: based on the surface topography information of the first surface 31 and the surface topography information of the second surface 21, a relative bonding manner of the first surface 31 and the second surface 21 is determined.

It should be noted that, referring to fig. 7, fig. 7 is a schematic structural diagram of bonding between a seed crystal and a seed crystal holder according to an embodiment of the present application, in an ideal case, the second surface 21 and the first surface 31 are smooth perfect surfaces, that is, the second surface 21 and the first surface 31 have no roughness, so that a good bonding effect can be achieved after the adhesive is uniformly coated. However, in practice, the bonding surface is not perfect and has irregularities, regardless of experimental statistics or theoretical analysis.

Based on the above, in the non-ideal case (the bonding surface has roughness), referring to fig. 8 to fig. 9, fig. 8 is a schematic structural diagram of bonding another seed crystal with the seed crystal holder according to the embodiment of the present application, and fig. 9 is a schematic structural diagram of bonding another seed crystal with the seed crystal holder according to the embodiment of the present application. The seed crystal 3 surface shown in fig. 8 and the seed crystal 3 surface shown in fig. 9 are partial surfaces of the same seed crystal 3 at different positions of the first surface 31, and the seed crystal holder 2 surface shown in fig. 8 and the seed crystal holder 2 surface shown in fig. 9 are partial surfaces of the same seed crystal holder 2 at the same position of the second surface 21. The bonding structure formed in fig. 8 does not confirm the relative bonding method based on the surface topography information of the first surface 31 and the second surface 21, but the bonding structure formed in fig. 9 confirms the relative bonding method based on the surface topography information of the first surface 31 and the second surface 21.

It is apparent that the uniformity of the spacing between the seed crystal 3 and the seed holder 2 in the bonding structure formed in fig. 9 is superior to the uniformity of the spacing between the seed crystal 3 and the seed holder 2 in the bonding structure formed in fig. 8. That is, in the case of non-ideal conditions (irregularities in the bonding surface), the relative bonding method is confirmed based on the surface topography information of the first surface 31 and the second surface 21, and in the relative bonding method, the uniformity of the pitch between the seed crystal 3 and the seed holder 2 is the best. Specifically, when the first surface 31 has a first protrusion and a first recess, and the second surface 21 has a second protrusion and a second recess, the relative fitting manner is that the center of the first surface 31 coincides with the center of the second surface 21, the first protrusion is maximally opposite to the second recess, and the first recess is maximally opposite to the second protrusion.

The confirmation relative bonding mode in the bonding method can effectively improve the uniformity of the spacing between the seed crystal 3 and the seed crystal support 2, fundamentally reduces the probability of forming a cavity tissue structure, increases the uniformity of heat transfer between the seed crystal 3 and the seed crystal support 2, is beneficial to controlling the nucleation and growth process in crystal growth, and optimizes the crystal quality. The amount of the adhesive between the seed crystal 3 and the seed crystal holder 2 is relatively reduced, so that the cost is reduced and the bonding quality between the seed crystal 3 and the seed crystal holder 2 is improved. In addition, the relative attaching mode also enhances the friction strength between the seed crystal 3 and the seed crystal holder 2, and improves the bonding strength.

Step S130: after the second surface 21 is coated with an adhesive, the adhesive is placed in the bonding apparatus according to any one of the above embodiments, and the seed holder 2 and the seed crystal 3 are bonded and fixed based on the relative bonding method.

Accordingly, the method of bonding and fixing the seed holder 2 coated with the adhesive and the seed crystal 3 in the bonding apparatus includes:

step S131: the seed crystal holder 2 coated with the adhesive is placed on a heating module 4 of the bonding device for heating so as to remove bubbles and volatile substances in the adhesive. In the embodiment of the application, the volatile substances include small organic molecular substances such as alkane, alcohols and the like, and inorganic gas-phase substances such as water vapor, carbon dioxide and the like.

Meanwhile, the heating module 4 heats the seed crystal holder 2 to volatilize volatile substances in the adhesive, so that cavities generated by rapid escape of the volatile substances in a subsequent high-temperature process are effectively avoided. In addition, the heating module 4 heats the seed crystal holder 2 to reduce the viscosity coefficient of the adhesive, so that a relatively uniform adhesive layer is formed on the seed crystal holder 2, and the bonding effect of the seed crystal 3 and the seed crystal holder 2 is improved.

Step S132: performing pre-bonding fixation, the pre-bonding fixation comprising: sequentially controlling the 1 st pressing unit 51 to the n-th pressing unit to press the seed crystal 3 through a pressing module 5 of the bonding device, wherein the pressing force formed by the m-th pressing unit is greater than the pressing force formed by the m+1-th pressing unit; m is a positive integer less than n.

The pre-bonding fixation is performed, so that the pressure formed by the mth pressure applying unit is higher than the pressure formed by the (m+1) th pressure applying unit, for example, the pressure formed by the (1) th pressure applying unit 51 is higher than the pressure formed by the (2) nd pressure applying unit 52, and therefore, the air in the cavity between the seed crystal 3 and the seed crystal support 2 can smoothly escape under the condition of pressure difference, and the cavity tissue between the seed crystal 3 and the seed crystal support 2 is further reduced.

Step S133: after the pre-bonding and fixing are completed, homogenizing and forming are carried out on the surface of one side, away from the seed crystal holder 2, of the seed crystal 3, and the method comprises the following steps: the 1 st pressing unit 51 to the n-th pressing unit are sequentially controlled to press the seed crystal 3 by the pressing module 5 of the bonding device, and the pressure formed by the m-th pressing unit is equal to the pressure formed by the m+1-th pressing unit.

After the pre-bonding is fixed, the pressure intensity formed based on the m-th pressure applying unit is greater than the pressure intensity formed by the m+1-th pressure applying unit, so that the thickness of the adhesive layer between the seed crystal 3 and the seed crystal support 2 is relatively different.

Accordingly, the method for obtaining the surface topography information of the first surface 31 and the surface topography information of the second surface 21 includes: setting the first surface 31 and the second surface 21 as sampling surfaces, and collecting coordinate information of a plurality of sampling points on the sampling surfaces

The center coordinates of the sampling surface are (0, 0), the center coordinates of the sampling surface are origins of a three-dimensional coordinate system, the three-dimensional coordinate system comprises an X axis, a Y axis and a Z axis which are positioned in the sampling surface and are perpendicular to the sampling surface, the X axis, the Y axis and the Z axis are perpendicular to each other, a plane where the X axis and the Y axis are positioned is an XY plane, and a projection point of the sampling point on the XY plane is P; r is the distance of P from the center of the sampling surface,

It should be noted that, based on the actual process, the shapes of the seed crystal 3 and the seed crystal holder 2 are circular, so r is selected in the embodiment of the present application,

the z cylindrical coordinate system characterizes the position information of the sampling point. However, in other embodiments, other parameters that can represent the position information of the sampling point may be selected, for example, (X, Y, Z), where X is the coordinate of the X axis (abscissa), Y is the coordinate of the Y axis (ordinate), and Z is the coordinate of the Z axis (ordinate).

Accordingly, determining the relative fit of the first surface 31 and the second surface 21 includes:

step S121: and establishing a model of the seed crystal 3 and the seed crystal holder 2.

Step S122: the center of the first surface 31 and the center of the second surface 21 are overlapped and then bonded.

Step S123: fixing the model of the seed holder 2 to rotate the model of the seed 3 based on a set step value through the rotation axes of the model center of the seed 3 and the model center of the seed holder 2, and collecting the number of contact points of the model of the first surface 31 and the model of the second surface 21 at different rotation angles.

Step S124: the relative fit is determined based on the state when there is the maximum number of contact points between the model of the first surface 31 and the model of the second surface 21. Wherein, when having the state of the maximum number of contact points, the space between the seed crystal 3 and the seed holder 2 is smallest, and the portion capable of generating the cavity tissue is smallest. Accordingly, the adhesive includes epoxy, silicone, and isopropyl alcohol.

In the bonding method, the relative bonding mode is determined based on the obtained surface morphology information of the first surface 31 and the surface morphology information of the second surface 21, so that the gap between the seed crystal 3 and the seed crystal holder 2 is minimized, the usage amount of the adhesive between the seed crystal 3 and the seed crystal holder 2 is relatively reduced, the cost is reduced, the number of cavity tissues between the seed crystal 3 and the seed crystal holder 2 is further reduced, and the friction strength between the seed crystal and the seed crystal holder is enhanced. Meanwhile, the method sequentially presses from the 1 st pressing unit 51 to the n th pressing unit in the bonding device, so that air between the seed crystal 3 and the seed crystal holder 2 escapes from inside to outside, defects including cavities, hexagonal cavities and the like existing between the seed crystal 3 and the seed crystal holder 2 are greatly reduced, and the bonding quality of the seed crystal 3 and the seed crystal holder 2 is improved.

In order to make the bonding method provided in the present application more understandable, the present application will be described in further detail with reference to the accompanying drawings and detailed description.

The specific bonding method provided by the embodiment of the application comprises the following steps:

step S210: surface topography information is obtained on the first surface 31 of the seed 3 and on the second surface 21 of the seed holder 2, i.e. the first surface 31 and the second surface 21 are characterized.

Specifically, the first surface 31 and the second surface 21 are characterized by a high-precision displacement testing device, so that geometric patterns of the first surface 31 and the second surface 21 are obtained, and a cylindrical coordinate system is correspondingly established for data of the geometric patterns of the first surface 31 and the second surface 21.

Taking the first surface 31 as an example, the axis of the seed crystal 3 is taken as the center origin of a cylindrical coordinate system, the cylindrical coordinate system comprises an X axis, a Y axis and a Z axis perpendicular to the first surface 31, the X axis, the Y axis and the Z axis are perpendicular to each other, and the coordinates of any point C on the first surface 31 are

r1 is the distance between the projection point of the C point on the first surface 31 and the center origin, and +.>

The angle between the line of the projected point of the C point on the first surface 31 and the center origin and the positive direction of the X axis is z1, which is the distance between the C point and the first surface 31. Correspondingly, the second surface 21 takes the axis of the seed crystal holder 2 as the center origin of a cylindrical coordinate system, and the coordinate of any point D on the second surface 21 is +. >

r2 is the distance of the projection point of the D point on the second surface 21 from the center origin, +.>

The angle between the line of the projected point of the D point on the second surface 21 and the center origin and the positive direction of the X axis is z2, which is the distance between the D point and the second surface 21.

During the geometrical data of the first surface 31 and the second surface 21, the first surface 31 and the second surface 21 are sampled, wherein the locations of the sampling points are determined based on a certain logical relationship. As shown in Table 1 below, table 1 is a table of positional information of sampling points on seed crystal 3 having a diameter of 100 mm.

TABLE 1 position information table of sampling points on seed crystal with diameter of 100mm

Sequence number	r1(mm)	Phi 1 (degree)	z1(μm)
				0	0	0	0
1	0.2	5	-0.1
				2	0.2	10	0
…	…	…	…
				2259250	50	360	0.8

Wherein r1 is valued by an arithmetic series with a head of 0 and a tolerance of 0.2mm, and an arithmetic series with a head of 0 and a tolerance of 5 degrees

Take the value to determine different r1 and +.>

The corresponding z1 value, in turn, characterizes the relief of the first surface 31.

Accordingly, the second surface 21 was sampled in the same manner, as shown in the following table 2, table 2 is a table of positional information of sampling points on the seed holder 2 having a diameter of 100 mm.

TABLE 2 position information table of sampling points on a seed holder with a diameter of 100mm

Sequence number	r2(mm)	Phi 2 (degree)	z2(μm)
				0	0	0	0
1	0.2	5	0.20
				2	0.2	10	0.23
…	…	…	…
				2259250	50	360	-0.6

Step S220: the relative bonding method of the seed crystal 3 and the seed holder 2 is determined in the same manner as in the above steps S121 to S124. Specifically, taking Python language for calculation and analysis as an example, determining the relative bonding mode of the seed crystal 3 and the seed crystal holder 2, wherein the core code of the calculation and analysis program is as follows:

In the case of fixing the seed holder 2, the above procedure sets i to an initial value of 1, j to an initial value of 0, r to an initial value of 1, and a tolerance of 0.2 based on the variation of the radius r, so that the step value d of rotation (i.e., the tolerance d of the rotation angle) satisfies: d=1/(r×0.2). In addition, f represents the number of sampling points on a certain radius, and f satisfies: f=360/d+1. The variable g is used for performing traversal calculation on points on a certain radius, and the value range is 0-f;

0 represents initializing the angle value of the seed crystal 3 and the seed crystal holder 2; after initialization, add to->

And->

Assigning a value to->

Representing the respective angle value +.>

Corresponding points, ++>

Representing the respective angle value +.>

Corresponding points. />

Representing when->

Point and +.>

The coordinate points of the points on the XY plane are mutually corresponding. if abs (z 1-z 2)<=0.3:j++ stands for ++based on tables 1 and 2>

Correspondence with z1->

And z2, when the absolute value of the difference between z1 and z2 is less than 0.3, is considered to be a contact, and thus represents the number of j of the number of contact pointsThe value is added to 1. The above procedure may be able to calculate the total number j of contact points of the seed crystal 3 and the seed holder 2 in this fitting manner (i.e., the relative positional relationship between the seed crystal 3 and the seed holder 2 after i rotations) after each rotation.

In addition, through the program operation, a numdirect dictionary database after one rotation period (360 degrees) of the seed crystal is completed is obtained. The relative fit is determined by finding i corresponding to the maximum value of j in the dictionary, i.e. the fit between the seed crystal 3 and the seed crystal holder 2 is chosen to be the relative fit when the seed crystal is rotated 360/i, in which the number of contact points of the first surface 31 and the second surface 21 is the largest (i.e. j takes the maximum value), i.e. the space between the seed crystal 3 and the seed crystal holder 2 is the smallest.

Step S230: an adhesive is applied to the second surface 21. In this embodiment of the present application, the adhesive is applied to the second surface 21 by a printing process, specifically, the adhesive is applied to the second surface 21 by using a 3D printing technology.

It should be noted that, the traditional sizing scheme is generally manual spreading and a spreading machine. The manual scraping to realize uniform sizing has great difficulty, has various uncontrollable factors such as scraping force, included angle, pushing rate and the like, and uses glue quantity, sizing homogenization degree and the like, is difficult to form stable bonding effect, and can not provide reliable guarantee for silicon carbide industrialization. And for the sizing scheme of the spin coater, the spin coater utilizes the centrifugal force to uniformly coat the liquid adhesive on the seed crystal, and the centrifugal force between the concentric circles has larger difference because the concentric circles are related to the radius, so that the spin coater is difficult to ensure the sizing uniformity. The two sizing schemes described above do not allow quantitative analysis of sizing amounts.

For above-mentioned two kinds of sizing schemes, the 3D printing technique that this application adopted can realize the imaging design of adhesive on the seed crystal holds in the palm, can also be through setting up the sizing dosage of the arbitrary position of accurate calculation of coordinate system, realizes the quantitative control to the sizing dosage, realizes the homogenization control of adhesive in the time of can reduce cost. In addition, the 3D printing technology is adopted, so that the bonding effect can be ensured, the using amount of the bonding agent is reduced to the greatest extent, the gas generation amount in the bonding process is reduced to the greatest extent, the stability of the bonding process is improved, and the large-scale and industrialized preparation of crystals is realized.

Specifically, the method for applying the adhesive on the second surface 21 includes:

step S231: and (3) configuring the adhesive, and placing the configured adhesive in printing equipment for standby. The adhesive comprises epoxy resin, silicone and isopropanol; wherein, the specific gravity of the adhesive is epoxy resin: silicone: isopropyl alcohol: carbon powder = 5-8:0-3:0.5-3:0.5-3. Preferably, in the embodiment of the present application, the component of the adhesive is epoxy resin: silicone: isopropyl alcohol: carbon powder = 7:1:1.5:0.5. it should be noted that the epoxy resin may be replaced by epoxy resin and phenolic resin, the silicone may be replaced by silicon powder, silane and silicone oil, the isopropyl alcohol may be replaced by propylene glycol, propanol, ethanol and ethylene glycol, and the particle size of the carbon powder is 10nm-100nm.

Step S232: the second surface 21 is coated with adhesive by a printing device. Specific:

step S232.1: on a computing unit in the printing equipment, a cylindrical coordinate system is established, and a model of the seed crystal holder 2 and the seed crystal 3 is established based on a relative fitting mode. The center of the seed crystal support 2 and the center of the seed crystal 3 are coincident, and the relative position relationship between the seed crystal support 2 model and the seed crystal 3 model is determined based on the relative fitting mode. In this step, the relative bonding method between the seed holder 2 model and the seed 3 model is a relative positional relationship after the application of the adhesive.

Specifically, referring to step S133 and step S210, a cylindrical coordinate system is established

Wherein, the distance between the positions where the seed crystal 3 contacts with the seed crystal holder 2 is 0, the distance between the seed crystal 3 and any one of the positions where the seed crystal holder 2 is not contacted is e, and z corresponding to the coordinate point of any one of the non-contact points is: z=0.8×e+α.

Where α is the minimum thickness of the glue applied between the seed crystal 3 and the seed holder 2, i.e. the glue applied at the point of contact between the seed crystal 3 and the seed holder 2, typically 20 μm to 50 μm, preferably α is 25 μm; the 0.8 is the fuzzy coefficient of the glue thickness and the gap distance, that is, the effective glue thickness is 0.8×e, the fuzzy coefficient is generally 0.6-0.95, and in this embodiment, the fuzzy coefficient is preferably 0.8, and the fuzzy coefficient is related to the concentration of the adhesive, the pressure of the pressing module, the curing curve and other factors.

Step S232.2: the number of required sizing times w at any one of the non-contacted positions is determined based on the height h of the single sizing of the printing device, the number of sizing times w being: w= { (h+e) ×δ }/H.

Where H is the height of the single sizing of the printing apparatus, H is the sizing thickness when the spacing between the seed crystal 3 and the seed crystal holder 2 is 0, and the sizing thickness at the non-contact space position is (h+e) ×δ, δ is the thickness correction coefficient, and the value of the thickness correction coefficient is usually less than 1. Generally, the thickness coefficient of the seed crystal using the silicon carbide conductive substrate is larger than that of the seed crystal using the silicon carbide semi-insulating substrate, and the LTV phase difference deviation is larger, so that the thickness correction coefficient delta is larger. Preferably, in the embodiment of the present application, the value of the thickness correction coefficient δ is generally 0.85.

The number of sizing times w is a rounded integer. For example, when w=1.5, w takes a value of 2.

In addition, when the glue application nozzle of the printing device is circular, the height h of single glue application of the printing device satisfies: h=pi θv ₁ /4k ₁ V ₂ θ is the diameter of the sizing nozzle, V1 is the glue outlet rate of the sizing nozzle, V2 is the moving rate of the sizing surface, and k ₁ To correct the factor, k ₁ The value is related to the viscosity coefficient, temperature, surface tension, wetting degree, etc. of the adhesive, k in the examples of the present application ₁ Has a value of 0.7-1, preferably k ₁ 0.85.

When the glue application nozzle of the printing equipment is square, the single glue application height h of the printing equipment meets the following conditions: h=k ₂ V ₁ h ₁ /V ₂ ，k ₂ To correct the factor, k ₂ The value is related to the viscosity coefficient, temperature, surface tension, wetting degree, etc. of the adhesive, and is implemented in the present applicationIn the example, k ₂ Has a value of 0.7 to 0.95, preferably k ₂ 0.85.h is a ₁ The height of the glue nozzle from the glue applying surface.

Step S232.3: placing the seed crystal support 2 on a workbench surface in printing equipment, setting the temperature of the seed crystal support 2 at 30-80 ℃ through the workbench surface, starting the printing equipment to coat the surface of the seed crystal support 2, marking the position of the seed crystal support 2 after coating is finished, and taking out the seed crystal support 2 for later use. Preferably, the working surface sets the temperature of the seed holder 2 at 40 ℃.

Wherein the number of times the printing device is applied at any one position is determined based on the calculated w of that position. By heating the seed crystal support 2, the volatile substances such as isopropanol with reduced viscosity coefficient can be timely escaped from the adhesive at the printing interval, so that the uniformity of the adhesive coating is improved, and especially, the uniformity of the coating is better when a plurality of printing areas exist, and the bonding effect of the adhesive is improved.

In the embodiment of the application, in the design sizing scheme, a three-dimensional geometric model of sizing is established on a computer according to the distance relation between a seed crystal 3 and a seed crystal holder 2, and a sizing program is set while a prepared adhesive is added into a printer resin tank; the sizing process starts at a certain point and then uniformly sizes on the seed holder 2. Other sizing methods such as dot or line sizing are also possible, and are not limited in this application.

Step S240: the seed crystal holder 2 with the second surface 21 coated with the adhesive is placed in an adhesion device, and the seed crystal holder 2 and the seed crystal 3 are adhered and fixed based on a relative adhesion mode.

Specifically, the method for adhering and fixing the seed crystal holder 2 and the seed crystal 3 comprises the following steps:

step S241: the seed holder 2 with the second surface 21 coated with the adhesive is placed on the heating module 4 for heating treatment. Wherein, the heating module 4 heats the seed crystal holder 2 to 30-60 ℃, and after the temperature is stable, the seed crystal holder 2 is kept stand on the heating module 4 for 10-60 min; and then the heating module 4 heats to 40-100 ℃ at a heating speed of 0.2-5 ℃/min, and after the temperature is stable, the seed crystal holder 2 is kept stand on the heating module 4 for 10-60 min.

Preferably, in the embodiment of the application, the heating module 4 heats the seed crystal holder 2 to 40 ℃, and after the temperature is stable, the seed crystal holder 2 is kept stand on the heating module 4 for 30min; and then the heating module 4 is heated to 60 ℃ at a heating speed of 2 ℃/min, and after the temperature is stable, the seed crystal holder 2 is kept stand on the heating module 4 for 30min.

According to the step, the seed crystal support 2 is subjected to heating treatment, and is kept stand for a period of time under the heating condition, so that bubbles and volatile substances in the adhesive can be effectively removed, cavity tissues caused by air aggregation and volatile substance volatilization are avoided, meanwhile, the viscosity coefficient of the adhesive can be reduced at a higher temperature, the adhesive is uniformly distributed on the surface of the seed crystal support 2, and the bonding quality between the seed crystal 3 and the seed crystal support 2 is improved.

Step S242: the first surface 31 and the second surface 21 are pre-bonded and fixed based on the above-described relative bonding method. Specifically, the pre-bonding and fixing method comprises the following steps:

step S242.1: after the heat treatment of the seed holder 2, an annular wedge-shaped spacer 6 is placed at the edge position of the seed holder 2. Wherein the height of the wedge-shaped gasket 6 is about 1 to 4 times the thickness of the adhesive, preferably the height of the wedge-shaped gasket 6 is about 1.5 times the thickness of the adhesive.

Step S242.2: the seed crystal 3 is placed on the seed crystal holder 2 in the above relative bonding mode, and then the heating module 4 heats the seed crystal holder 2 at a heating speed of 0.2 ℃/min-4 ℃/min until the target temperature is raised to 80 ℃ to 150 ℃, and then the target temperature is kept for 5min-60min.

Preferably, in the embodiment of the present application, the heating module 4 heats the seed holder 2 at a heating rate of 0.5 ℃/min until the target temperature is maintained for 15min after the target temperature is raised to 100 ℃.

Step S242.3: the seed crystal 3 is pressed by a pressing module 5, wherein the pressing module 5 sequentially controls the 1 st pressing unit 51 to the n-th pressing unit to press the seed crystal 3, and the pressing force formed by the m-th pressing unit is greater than the pressing force formed by the m+1-th pressing unit; m is a positive integer less than n.

Specifically, referring to table 3, table 3 is pressing data in which the pressing module 5 is 4 annular pressing units and the seed crystal is 6 inches. In this application, the central circular pressing unit is regarded as an annular pressing unit, that is, the 4 annular pressing units are 1 central circular pressing unit and 3 annular pressing units surrounding the circular pressing unit, and are not described in detail in other positions of this application.

TABLE 3 pressure information table formed by pressing seed crystal by 1 st pressing unit to 4 th pressing unit

As is clear from table 3, the pressure applied by the 1 st pressing unit 51 was 11kg, the pressure applied by the 2 nd pressing unit 52 was 19kg, the pressure applied by the 3 rd pressing unit 53 was 27kg, and the pressure applied by the 4 th pressing unit 54 was 35kg. Obviously, the pressures formed by the 1 st pressing unit 51 to the 4 th pressing unit 54 are sequentially reduced, and the gas between the seed crystal 3 and the seed crystal holder 2 escapes due to the pressure difference from inside to outside, so that the cavity between the seed crystal 3 and the seed crystal holder 2 is reduced, and the bonding quality is improved.

It should be noted that, during the process of successive pressing by the pressing unit, the driving assembly controls the annular wedge-shaped gasket 6 to move outwards gradually, and before the nth pressing unit presses, the driving assembly controls the annular wedge-shaped gasket 6 to move out between the seed crystal 3 and the seed crystal holder 2. Through the removal of control wedge gasket 6, realized controlling the difference in height between seed crystal 3 and the seed crystal support 2, avoided seed crystal 3 to damage because of the extra torque is too big, simultaneously, wedge gasket 6 exists the space in seed crystal and the seed crystal support 2, for the gaseous passageway that has provided the escape between seed crystal 3 and the seed crystal support 2, ensured gaseous escape, improved bonding quality. Further, the pressing module 5 is exemplified by 4 annular pressing units, namely, a 1 st pressing unit 51, a 2 nd pressing unit 52, a 3 rd pressing unit 53 and a 4 th pressing unit 54 from inside to outside.

After the heating module 4 heats the seed crystal holder 2 to 80-150 ℃ and keeps the temperature for 5-60 min, preferably, the heating module 4 heats the seed crystal holder 2 to 100 ℃ and keeps the temperature for 15min, a pressure control pump in the chamber 1 is started, gas in the chamber 1 is pumped through the gas pumping hole 72, 200sccm of protective gas is pumped through the gas pumping hole 71, the pressure of the chamber 1 is controlled to 80kPa through the gas pumping hole 72 and the gas pumping hole 71, namely, the chamber 1 is in a negative pressure state, so that a pressure difference exists between the seed crystal 3 and the seed crystal holder 2, gas is convenient to escape, and the possibility of gas aggregation is reduced.

Starting a hydraulic control system in the cavity 1, controlling the 1 st pressing unit 51 to apply 11kg pressure to the seed crystal 3, keeping the pressure for 5-60 min, and then controlling the wedge-shaped gasket 6 to move outwards by 1/3, namely 1mm, based on the fact that the length of the part of the wedge-shaped gasket 6, which is positioned between the seed crystal 3 and the seed crystal holder 2, is 3 mm; the 2 nd pressing unit 52 is controlled to apply 19kg of pressure to the seed crystal and keep for 5min-60min, and then the driving assembly is controlled to continuously move the wedge-shaped gasket 6 outwards for 1/3, namely 1mm; the 3 rd pressing unit 53 is controlled to apply 27kg of pressure to the seed crystal 3 and keep for 5min-60min, and then the driving assembly controls the wedge-shaped gasket 6 to continue to move outwards for 1/3, namely 1mm, and at the moment, the wedge-shaped gasket 6 is completely moved out from between the seed crystal 3 and the seed crystal holder 2; the 4 th pressing unit 54 is controlled to apply a pressure of 35kg to the seed crystal and hold for 5min to 60min.

Preferably, in the embodiment of the present application, after the 1 st pressing unit 51 applies 11kg of pressure to the seed crystal 3, the pressure is maintained for 10 minutes; the 2 nd pressing unit 52 applies a pressure of 19kg to the seed crystal 3 and then holds the pressure for 10 minutes; the 3 rd pressing unit 53 keeps the pressure for 10 minutes after applying 27kg to the seed crystal 3; after the 4 th pressing unit 54 applies a pressure of 35kg to the seed crystal 3, the pressure was maintained for 10 minutes.

Step S243: after the pre-bonding and fixing are completed, flattening the surface of one side, away from the seed crystal holder 2, of the seed crystal 3, wherein the flattening comprises the following steps: and the 1 st pressing unit 51 to the n th pressing unit are sequentially controlled to press the seed crystal through a pressing module 5 of the bonding device, and the pressure formed by the m-th pressing unit is equal to the pressure formed by the m+1-th pressing unit.

Specifically, referring to table 4, table 4 is pressing data in which the pressing module 5 is 4 annular pressing units and the seed crystal 3 is 6 inches.

TABLE 4 pressure information Table formed by pressing seed crystal by another 1 st pressing unit to 4 th pressing unit

As is clear from table 4, the pressure applied by the 1 st pressing unit 51 was 11kg, the pressure applied by the 2 nd pressing unit 52 was 33kg, the pressure applied by the 3 rd pressing unit 53 was 55kg, and the pressure applied by the 4 th pressing unit 54 was 77kg. Obviously, the pressures formed by the 1 st pressing unit 51 to the 4 th pressing unit 54 are equal, and the pressing units of the pressing module 5 are used for pressing the seed crystal 3 to form the same pressure, so that the seed crystal 3 is flattened, the flatness of the surface of one side of the seed crystal 3, which is away from the seed crystal holder 2, is improved, the heat conductivity between the seed crystal 3 and the seed crystal holder 2 is better, and the growth quality of the seed crystal 3 is further improved.

In the embodiment of the present application, the pressure applied by the pressing unit to the seed crystal 3 is 0.01 to 1N/mm ² Preferably, the pressure applied by the pressure applying unit to the seed crystal 3 is 0.05-0.5N/mm ² 。

Further, the pressing module 5 is exemplified by 4 annular pressing units, namely, a 1 st pressing unit 51, a 2 nd pressing unit 52, a 3 rd pressing unit 53 and a 4 th pressing unit 54 from inside to outside.

After the pre-bonding fixation is completed, the temperature of the seed crystal holder 2 is raised to 135-165 ℃ through a heating module 4 at a heating rate of 0.4 ℃/min-4 ℃/min, and the seed crystal holder is kept at the temperature of 135-165 ℃ for 30-300 min. It should be noted that, as the diameter of the seed crystal 3 increases, the heating rate of the heating module 4 decreases, and the time for relatively keeping warm is longer, so that the gas between the seed crystal 3 and the seed crystal holder 2 can escape more sufficiently. Preferably, in the present embodiment, the heating module 4 increases the temperature of the seed holder 2 to 150 ℃ at a heating rate of 1 ℃/min, and maintains the temperature at 150 ℃ for 60min.

The temperature is continuously increased by the heating module 4 at the heating rate of 0.5 ℃/min-5 ℃/min, and the temperature is kept at the temperature for 40min-400min when the temperature is increased to 500 ℃ -800 ℃. After the end of the heat preservation, the hydraulic control system in the chamber 1 is started, and the pressures applied by the 1 st pressing unit 51 to the 4 th pressing unit 54 are controlled to be 11kg, 33kg, 55kg and 77kg in sequence. Then the temperature is continuously increased by the heating module 4 at the heating rate of 1 ℃ to 10 ℃ per minute, and the temperature is kept at the temperature for 60 to 300 minutes after the temperature is increased to 900 ℃ to 1500 ℃. After the heat preservation is finished, the temperature of the seed crystal holder 2 is controlled to be reduced to the room temperature at the cooling speed of 2 ℃/min-20 ℃/min. After the temperature is reduced to room temperature, introducing protective gas into the cavity 1 until the pressure in the cavity 1 is normal pressure, and taking out the bonded seed crystal 3 and the seed crystal holder 2 for standby, wherein the bonding of the seed crystal 3 and the seed crystal holder 2 is finished.

Preferably, the heating module 4 continues to raise the temperature at a heating rate of 2 ℃/min, and is maintained at 600 ℃ for 60min when the temperature is raised to 600 ℃. After the end of the heat preservation, the hydraulic control system in the chamber 1 is started, and the pressures applied by the 1 st pressing unit 51 to the 4 th pressing unit 54 are controlled to be 11kg, 33kg, 55kg and 77kg in sequence. The temperature was then continued to be increased by the heating module 4 at a heating rate of 4 deg.c/min, and maintained at that temperature for 180min after the temperature was increased to 1200 deg.c. After the heat preservation is finished, the temperature of the seed crystal holder 2 is controlled to be reduced to the room temperature at the cooling speed of 6 ℃/min.

In addition to the above bonding method, the present application also provides another specific bonding method, including:

step S310: the first surface 31 of the seed crystal 3 is subjected to hydrogen etching treatment to obtain a third surface for bonding, and surface topography information of the third surface of the seed crystal 3 and surface topography information of the second surface 21 of the seed holder 2 are obtained, i.e. the third surface and the second surface 21 are characterized. The method of obtaining a third surface for bonding comprises: hydrogen with the temperature of 1550 ℃ is kept for 50min for hydrogen etching treatment by introducing hydrogen with the temperature of 5slm-60slm, so that microscopic damage on the first surface 31 of the seed crystal 3 can be removed, and an intrinsic structural layer of the seed crystal is exposed.

In addition, after the hydrogen etching treatment, 200sccm of silane was introduced at 1000℃to 1300℃to form a third surface. Preferably, 200sccm of silane is introduced at 1050 ℃. The method can eliminate the unbalance phenomenon of the surface stoichiometric ratio caused by hydrogen etching, and is also beneficial to eliminating the oxide on the surface of the seed crystal 3. Meanwhile, the third surface formed by the method has better bonding effect with the second surface 21.

It is preferable that the hydrogen etching treatment of the seed crystal 3 is performed by supplying 10slm of hydrogen gas and maintaining the pressure at 85kPa and the temperature at 1850 ℃ for 15 minutes to obtain the third surface. When the seed crystal is silicon carbide seed crystal, the process can lead silicon atoms of the seed crystal to sublimate and carbon atoms to reconstruct, and finally a graphite layer, namely graphene, is formed on the surface of the silicon carbide seed crystal.

In addition, the principle of characterizing the third surface and the second surface 21 is the same as that of characterizing the first surface 31 and the second surface 21 in step S210, and thus, they are not described in detail herein.

Step S320: based on the surface topography information of the third surface and the surface topography information of the second surface 21, a relative bonding manner of the seed crystal 3 and the seed holder 2 is determined. The principle of step S320 is the same as that of step S210, and reference may be made to each other, which is not described in detail in this application.

Step S330: an adhesive is applied to the second surface 21 and the third surface. The adhesive is divided into an A adhesive and a B adhesive, wherein the A adhesive is coated on the second surface 21, and the B adhesive is coated on the third surface.

Wherein, the adhesive A comprises epoxy resin, silicone and isopropanol, and the specific gravity of the adhesive is epoxy resin: silicone: isopropyl alcohol: carbon powder = 5-8:0-3:0.5-3:0.5-3. Preferably, in the embodiment of the present application, the component of the adhesive is epoxy resin: silicone: isopropyl alcohol: carbon powder = 7:1:1.5:0.5. in addition, the particle size of the carbon powder is 10nm-100nm, and preferably, the particle size of the nano carbon powder in the embodiment of the application is 30nm.

The adhesive B comprises epoxy resin, methylsilane, nano silicon powder and isopropanol, and the specific gravity of the adhesive B is the epoxy resin: methylsilane: nano silicon powder: isopropanol=1: 5:1:3. it should be noted that, the epoxy resin may be replaced by epoxy resin and phenolic resin, the silicone may be replaced by silicon powder, silane and silicone oil, the isopropyl alcohol may be replaced by propylene glycol, propanol, ethanol and ethylene glycol, and the nano silicon powder has a particle size of 10nm-100nm, preferably, in the embodiment of the application, the nano silicon powder has a particle size of 35nm.

Accordingly, the method of applying the adhesive a to the second surface 21 in step S330 is the same as the method of applying the adhesive to the second surface 21 in step S230. The method of coating the adhesive B on the third surface is the same as the method of coating the adhesive on the second surface 21 in step S230, except that the thickness of the single-layer adhesive for printing on the third surface is 0.5 μm-5 μm, and other process conditions are the same. Preferably, the thickness of the single layer of glue that prints onto the third surface is 2 μm.

Step S340: the seed crystal holder 2 coated with the adhesive A on the second surface 21 and the seed crystal coated with the adhesive B on the third surface are placed in an adhesion device, and the seed crystal holder 2 are adhered and fixed based on a relative adhesion mode.

The method for bonding and fixing the seed crystal and the seed crystal holder 2 comprises the following steps:

step S341: heating the seed crystal 3 by a heating module 4 at a heating rate of 0.5 ℃/min-5 ℃/min until the temperature reaches 50 ℃ -80 ℃, and keeping the seed crystal at the temperature for 35min-40min; then heating the temperature to 80-150 ℃ by a heating module 4 at a heating rate of 0.5-5 ℃/min, and standing the seed crystal 3 at the temperature for 5-60 min; finally, the temperature of the seed crystal 3 is controlled to be reduced to the room temperature at the cooling speed of 1 ℃/min-20 ℃/min. The step effectively removes the gas and volatile substances in the adhesive B.

Preferably, in the embodiment of the application, the heating module 4 heats the seed crystal 3 at a heating rate of 1 ℃/min until the temperature reaches 70 ℃, and then the seed crystal is kept standing at 70 ℃ for 20min; heating the temperature to 100 ℃ through a heating module 4 at a heating rate of 1 ℃/min, and standing the seed crystal 3 at 100 ℃ for 15min; finally, the temperature of the seed crystal 3 is controlled to be reduced to room temperature at a temperature reduction speed of 5 ℃/min.

Step S342: the same principle as in step S241 can be referred to each other, and will not be described here again.

Step S343: the same principle as in step S242 can be referred to each other, and will not be described here again.

Step S344: the same principle as that of step S243 can be referred to each other, and will not be described here again.

In summary, according to the bonding device and the bonding method between the seed crystal 3 and the seed crystal holder 2 provided by the application, the 1 st pressing unit 51 to the n-th pressing unit are sequentially controlled by the pressing module 5 to press the seed crystal 3, so that air in the cavity between the seed crystal 3 and the seed crystal holder 2 escapes from inside to outside, and defects including cavities, hexagonal cavities and the like existing between the seed crystal 3 and the seed crystal holder 2 are reduced. Meanwhile, the mutual attaching mode is determined by representing the first surface 31 and the second surface 21, and the second surface 21 is coated with the adhesive through a printing technology, so that the space between the seed crystal 3 and the seed crystal support 2 and the using amount of the adhesive are effectively reduced, the cavity between the seed crystal 3 and the seed crystal support 2 is relatively reduced besides the cost is reduced, and the bonding quality of the seed crystal 3 and the seed crystal support 2 is further improved.

In the present specification, each embodiment is described in a progressive manner, or a parallel manner, or a combination of progressive and parallel manners, and each embodiment is mainly described as a difference from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.

It should be noted that, in the description of the present application, it should be understood that the directions or positional relationships indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the apparatus or element to be referred to must have a specific direction, be configured and operated in the specific direction, and thus should not be construed as limiting the present application. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.

It is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in an article or apparatus that comprises such element.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bonding apparatus for a seed crystal and a seed crystal holder, comprising:

the heating module is positioned at the bottom of the cavity;

the pressing module is positioned at one side of the seed crystal support, which is away from the heating module, and is used for pressing towards the seed crystal so as to ensure that the seed crystal is attached and fixed with the seed crystal support; the pressing module comprises a 1 st pressing unit to an n-th pressing unit, wherein n is a positive integer greater than 1, and the n-th pressing unit surrounds the n-1-th pressing unit; the pressing module is used for sequentially controlling the 1 st pressing unit to the n th pressing unit to press the seed crystal, so that the pressure of the corresponding area of the 1 st pressing unit to the pressure of the corresponding area of the n th pressing unit is gradually reduced;

The center of the 1 st pressing unit corresponds to the centers of the seed crystal and the seed crystal support;

further comprises: wedge-shaped gaskets and drive assemblies; before the 1 st pressing unit presses the seed crystal, the driving assembly is used for controlling the wedge-shaped gasket to be positioned between the edge of the seed crystal support and the edge of the seed crystal, and the thickness of the wedge-shaped gasket is sequentially increased in the direction of the center of the seed crystal support towards the edge; after the 1 st pressing unit presses the seed crystal, the driving assembly controls the wedge-shaped gasket to slowly move from the center to the edge until the nth pressing unit presses the seed crystal, and the driving assembly is used for controlling the wedge-shaped gasket to be pulled away from the area between the seed crystal support and the seed crystal.

2. The bonding apparatus of claim 1, wherein the chamber comprises:

a vent for providing a shielding gas for the chamber to ensure that the seed holder, the seed crystal and the adhesive are not oxidized when heated at a high temperature, and simultaneously to maintain the pressure of the chamber at a target value;

3. The bonding apparatus according to claim 1, wherein the 1 st pressing unit is in the shape of a cylinder, and the n-th pressing unit is in the shape of a hollow cylinder.

4. The bonding apparatus of claim 1, wherein an adhesive is provided between the seed holder and the seed crystal.

5. A method of bonding a seed crystal to a seed holder, the seed crystal having a first surface and the seed holder having a second surface, the first surface being adhesively secured to the second surface, the method comprising:

after the second surface is coated with an adhesive, the second surface is placed in the bonding device according to any one of claims 1 to 4, and the seed crystal holder and the seed crystal are bonded and fixed based on the relative bonding mode.

6. The bonding method according to claim 5, wherein the method of bonding and fixing the seed holder coated with the adhesive to the seed crystal in the bonding apparatus comprises:

7. The bonding method according to claim 5, wherein the method of acquiring the surface topography information of the first surface and the surface topography information of the second surface comprises:

setting the first surface and the second surface as sampling surfaces, and collecting coordinate information (r, phi, z) of a plurality of sampling points on the sampling surfaces;

The center coordinates of the sampling surface are (0, 0), the center coordinates of the sampling surface are origins of a three-dimensional coordinate system, the three-dimensional coordinate system comprises an X axis, a Y axis and a Z axis which are positioned in the sampling surface and are perpendicular to the sampling surface, the X axis, the Y axis and the Z axis are perpendicular to each other, a plane where the X axis and the Y axis are positioned is an XY plane, and a projection point of the sampling point on the XY plane is P; r is the distance between P and the center of the sampling surface, phi is the angle between the connecting line of P and the center of the sampling surface and the positive direction of the X axis, and z is the distance between the sampling point and the XY plane.

8. The bonding method according to claim 5, wherein determining the relative fit of the first surface and the second surface comprises:

establishing a model of the seed crystal and the seed crystal holder;

9. The bonding method according to claim 5, wherein the adhesive comprises epoxy resin, silicone, and isopropyl alcohol.