CN114561695A

CN114561695A - Device and method for bonding seed crystal and seed crystal holder

Info

Publication number: CN114561695A
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 Shiji Jinguang Semiconductor Co ltd
Current assignee: Hefei Shiji Jinguang Semiconductor Co ltd
Priority date: 2022-03-04
Filing date: 2022-03-04
Publication date: 2022-05-31
Anticipated expiration: 2042-03-04
Also published as: CN114561695B

Abstract

The application provides a seed crystal and a seed crystal support bonding device and a bonding method, comprising the following steps: the device comprises a cavity, and a heating module, a seed crystal support and a pressure applying module which are positioned in the cavity; wherein, the heating module is positioned at the bottom of the chamber; the seed crystal support is positioned on one side of the heating module, which is far away from the bottom of the chamber, and is used for fixing seed crystals; the pressure applying module is positioned on one side of the seed crystal support, which is far away from the heating module, and is used for applying pressure to the seed crystal so as to ensure that the seed crystal is fixedly attached to the seed crystal support; the pressing module comprises a 1 st pressing unit to an nth pressing unit, wherein n is a positive integer greater than 1, and the nth pressing unit surrounds an n-1 th pressing unit; the pressure applying module is used for sequentially controlling the 1 st to the nth pressure applying units to apply pressure to the seed crystal. The bonding device and the bonding method provided by the technical scheme of the invention reduce the micro-cavity defect structure between the seed crystal and the seed crystal support and improve the bonding quality of the seed crystal and the seed crystal support.

Description

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

Technical Field

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

Background

Silicon carbide (SiC) is a wide bandgap semiconductor material that has been rapidly developed in recent ten years, and compared with other semiconductor materials, silicon carbide materials have advantages such as a wide bandgap, high thermal conductivity, high carrier saturation mobility, and high power density, and are widely used in related fields such as semiconductors.

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

In the prior art, most of the seed crystals and the seed crystal supports are fixed by using an adhesive, but due to uneven sizing, local bubbles generated by the fact that gas-phase substances generated by chemical reaction cannot be smoothly removed in the high-temperature process of glue between the seed crystals and the seed crystal supports and micropore cavity defect structures such as an isolated point cavity, a linear cavity or a sheet cavity and the like existing between the seed crystals and the seed crystal supports caused by neglecting the change of the distance between the seed crystals and the seed crystal supports, the bonding effect of the seed crystals and the seed crystal supports is influenced, hexagonal cavities, microtubules and the like easily occur in the silicon carbide crystal grown by using the silicon carbide crystal support, and even the seed crystals fall off in the growth process in serious cases. In addition, the above phenomenon is more prominent with increasing crystal size (e.g., 8 inch silicon carbide crystals). Therefore, how to achieve high-quality bonding of the seed crystal and the seed holder becomes one of the problems to be solved by those skilled in the art.

Disclosure of Invention

In view of this, the application provides a device and a method for bonding 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 purpose, the invention provides the following technical scheme:

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

the device comprises a cavity, and a heating module, a seed crystal support and a pressure applying module which are positioned in the cavity; wherein the content of the first and second substances,

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

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

the pressure applying module is positioned on one side of the seed crystal support, which is far away from the heating module, and is used for applying pressure to the seed crystal so as to ensure that the seed crystal is fixedly attached to the seed crystal support; the pressing module comprises a 1 st pressing unit to an nth pressing unit, wherein n is a positive integer greater than 1, and the nth pressing unit surrounds an n-1 th pressing unit; the pressure applying module is used for sequentially controlling the 1 st to the nth pressure applying units to apply pressure to 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 comprising: a wedge shim and a drive assembly; before the 1 st pressure applying unit applies pressure to 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 increased in sequence in the direction from the center of the seed crystal support to the edge; before the nth pressing unit presses the seed crystal, the driving assembly is used for controlling the wedge-shaped gasket to be drawn out of the area between the seed crystal holder and the seed crystal.

Preferably, the chamber comprises:

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

and a pumping port for pumping gas in the chamber to prevent the seed holder, the seed crystal and the adhesive from being oxidized before heating, while maintaining the pressure of the chamber 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 for 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 bonding method comprising:

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

determining a relative fit mode of the first surface and the second surface based on the surface topography information of the first surface and the surface topography information of the second surface;

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

Preferably, the method for adhesively fixing the seed crystal holder coated with the adhesive to the seed crystal in the bonding apparatus includes:

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

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

after the pre-bonding fixation is completed, homogenizing and forming the surface of one side of the seed crystal, which is far away from the seed crystal support, and the method comprises the following steps: and sequentially controlling the 1 st pressing unit to the nth pressing unit to press the seed crystal through the pressing module of the bonding device, wherein the pressure formed by the mth pressing unit is equal to the pressure formed by the m +1 th pressing unit.

Preferably, the method for acquiring 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

The central coordinate of the sampling surface is (0, 0, 0), the central coordinate of the sampling surface is the origin of a three-dimensional coordinate system, the three-dimensional coordinate system comprises an X axis, a Y axis and a Z axis, the X axis, the Y axis and the Z axis are located in the sampling surface, the X axis and the Y axis are perpendicular to each other, the plane where the X axis and the Y axis are located is an XY plane, and the 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,

is the angle between the line connecting the 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 surface.

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

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

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

fixing the model of the seed crystal holder so as to rotate the model of the seed crystal based on a set step value through a rotating shaft passing through the model center of the seed crystal and the model center of the seed crystal holder, 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 model of the first surface and the model of the second surface have the maximum number of the contact points.

Preferably, the adhesive includes epoxy, silicone, and isopropyl alcohol.

According to the bonding device and the bonding method provided by the technical scheme of the invention, the 1 st to nth pressure applying units are sequentially controlled by the pressure applying module to apply pressure to the seed crystal, 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 existing 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 needed to be used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

The structures, proportions, and dimensions shown in the drawings and described in the specification are for illustrative purposes only and are not intended to limit the scope of the present disclosure, which is defined by the claims, but rather by the claims, it is understood that these drawings and their equivalents are merely illustrative and not intended to limit 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 diagram of a bonding apparatus according to an embodiment of the present disclosure;

FIG. 3 is a side view of a wedge-shaped shim according to an embodiment of the present disclosure;

fig. 4 is a schematic top view of a pressure application module provided in an embodiment of the present application;

fig. 5 is a schematic top view of another pressing module provided in the embodiments of the present application;

FIG. 6 is a schematic step diagram of a bonding method according to an embodiment of the present disclosure;

FIG. 7 is a schematic structural diagram of a seed crystal bonded to a seed holder according to an embodiment of the present disclosure;

FIG. 8 is a schematic structural view of another seed crystal bonded to a seed crystal holder according to an embodiment of the present application;

fig. 9 is a schematic structural diagram of another seed crystal and seed holder bonding structure provided in the 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 embodiments of the application are shown, and in which it is to be understood that the embodiments described are merely illustrative of some, but not all, of the embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

As described in the background art, the currently mainstream silicon carbide crystal growth method is mainly a physical vapor transport method (PVT), the principle of the method is shown in fig. 1, fig. 1 is a growth principle diagram of a physical vapor transport method provided in an 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 crystal holder 2 positioned at the top of the growth chamber 1 for holding a seed crystal 3.

In the physical vapor phase transmission method, a silicon carbide raw material for growing the silicon carbide crystal is placed at the bottom of a growth chamber 1, a seed crystal 3 is fixed on a seed crystal support 2, and the silicon carbide raw material is sublimated and then rises to the seed crystal 3 positioned at the top of the growth chamber 1 to carry out 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-mentioned growth method, the crystal growth of silicon carbide is influenced by many factors such as temperature, pressure, temperature field distribution and purity of raw material, wherein how to fix the seed crystal 3 on the top of the growth chamber 1 is a basic condition for realizing the growth of silicon carbide crystal and is also a key factor for influencing the crystal growth process and crystallization.

At present, a commonly used method for fixing the seed crystal 3 and the seed crystal holder 2 is a bonding process, the bonding process is generally 'glue application-bonding-curing', and then the seed crystal 3 and the seed crystal holder 2 are fixed, but in the actual process, due to the uneven coating of the adhesive, the bonding thickness of the seed crystal 3 and the seed crystal holder 2 is uneven, so that a micro-cavity is generated 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 a non-contact part possibly exists between the seed crystal 3 and the seed crystal holder 2, so that a cavity is generated in the bonding process, and the gas in the cavity is difficult to remove. In addition, when the adhesive is cured at high temperature, gas retained in the cavity between the seed crystal support 2 and the seed crystal 3 expands due to temperature rise, and meanwhile, the adhesive can generate a certain amount of gas under the high-temperature condition, so that the gas generated by the adhesive forms a new cavity or is converged to the original cavity, the number and the volume of the cavities are increased, and when the gas retained between the seed crystal support 2 and the seed crystal 3 is more, a linear cavity can be generated due to the fact that local gas pressure is large and escapes rapidly outwards.

The presence of the cavity may cause a reduction in the adhesion between the seed crystal 3 and the seed crystal holder 2, and may even cause the seed crystal 3 to fall off during the crystal growth. In addition, because 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 generates back corrosion in the cavity area, so that defects such as micropipes and hexagonal cavities are formed, and the crystal quality is seriously influenced. When the size of the seed crystal 3 is larger, the requirement for the seed crystal bonding process is higher. 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 influence on the crystal quality.

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

Referring to fig. 2, fig. 2 is a schematic structural diagram of a bonding apparatus according to an embodiment of the present disclosure. The bonding apparatus includes:

the device comprises a chamber 1, and a heating module 4, a seed crystal holder 2 and a pressure applying module 5 which are positioned in the chamber 1; wherein, the first and the second end of the pipe are connected with each other,

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

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

The pressing module 5 is positioned on one side of the seed crystal holder 2, which is far away from the heating module 4, and is used for pressing the seed crystal 3 so as to ensure that the seed crystal 3 is fixedly attached to the seed crystal holder 2; the pressing module 5 comprises a 1 st pressing unit 51 to an nth pressing unit, wherein n is a positive integer greater than 1, and the nth pressing unit surrounds an n-1 th pressing unit; the pressure applying module 5 is used for sequentially controlling the 1 st pressure applying unit 51 to the nth pressure applying unit to apply pressure to the seed crystal 3.

The bonding device controls the 1 st pressing unit 51 to the nth pressing unit to press the seed crystal 3 through the pressing module 5, so that the pressure intensity of the area corresponding to the 1 st pressing unit 51 to the pressure intensity of the area corresponding to the nth pressing unit are gradually reduced, air in a cavity between the seed crystal 3 and the seed crystal support 2 is enabled to escape, and defects caused by the existence of the cavity are reduced. In addition, the bonding device can also heat the adhesive between the seed crystal holder 2 and the seed crystal 3 to remove gas and volatile substances in the adhesive, and the physical state and chemical properties of the adhesive can be changed by heating to improve the bonding property of the adhesive, so that the bonding quality of the seed crystal 3 and the seed crystal holder 2 is improved.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, the present application is described in further detail with reference to the accompanying drawings and the detailed description.

In an embodiment of the present application, referring to fig. 2, the center of the 1 st pressing unit 51 corresponds to the centers of the seed crystal 3 and the seed crystal holder 2; the bonding apparatus further includes: a wedge-shaped gasket 6 and a driving 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 increased in sequence in the direction from the center of the seed crystal holder 2 to the edge; before the n-th pressing unit presses the seed crystal 3, the driving assembly is used for controlling the wedge-shaped gasket 6 to be drawn out of the area between the seed crystal holder 2 and the seed crystal 3.

After the 1 st pressing unit 51 presses the seed crystal 3, the driving assembly controls the wedge-shaped pad 6 to slowly move from the center to the edge until the wedge-shaped pad 6 is pulled away from the area between the seed 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 pad provided in the embodiment of the present application, and the wedge-shaped pad 6 is in contact with the edge of the seed crystal holder 2 and does not form a complete surface contact with the seed crystal holder 2, so as to prevent the adhesive coated on the surface of the seed crystal holder 2 from being damaged.

This bonding device passes through wedge gasket 6 and drive assembly, realizes controlling the difference in height between seed crystal 3 and the seed crystal support 2, has avoided carborundum to be cracked because of the extra torque is too big at the in-process of exerting pressure, and when wedge gasket 6 removed, wedge gasket 6 and seed crystal 3 and seed crystal support between 2 produced the gap, and then can make the gas in the bonding agent escape smoothly.

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

A pumping port 72 for pumping gas inside the chamber 1 to prevent the seed holder 2, the seed crystal 3, and the adhesive from being oxidized before heating while maintaining the pressure of the chamber 1 at a target value.

In the embodiment of the present application, the pressure in the chamber 1 is controlled by controlling the pumping port 72 and the vent 71 so that the pressure is maintained at a target value. In addition, the control vent 71 provides protective gas for the chamber 1, and can protect the seed crystal 3, the seed crystal holder 2 and the adhesive in the chamber 1 from being oxidized; accordingly, the pumping port 72 is controlled to pump the gas in the chamber 1, thereby preventing the seed crystal 3, the seed holder 2 and the adhesive from being oxidized.

When needing to be explained, the protective gas comprises argon, nitrogen, argon and nitrogen mixed gas and the like, and can avoid that the heated seed crystal support 3, the heated seed crystal 2 and the adhesive react with oxygen in the air in the bonding and curing process of the seed crystal 3 and the seed crystal support 2, so as to influence the bonding quality of the seed crystal 2 and the seed crystal support 3. In the actual process, the gases having no reaction with the raw materials can be regarded as the protective gases, and are all within the protection scope of the present application, which is not limited in the present application.

In addition, the chamber 1 further comprises: and the cavity pressure control system is used for controlling the cavity pressure of the cavity 1. The cavity pressure control system comprises a pressure control pump, and the pressure control pump is connected with the pumping hole 72.

The cavity pressure control system can enable the cavity 1 to be under negative pressure, so that a 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 conveniently escape, and the possibility of gas aggregation is reduced. Besides, the chamber 1 comprises: a hydraulic control system for controlling the application pressures of the 1 st to nth pressing units 51 to 51.

Optionally, in the embodiment of the present application, the chamber 1 is a structure of an upper cover 12 and a lower cover 11, and the upper cover 12 and the lower cover 11 form a closed chamber 1 by fastening the screws 8 during the process, and the chamber 1 is easy to take the seed crystal and the seed crystal holder 2, and facilitates the maintenance of the bonding device. In other embodiments, the chamber 1 may be an integrally enclosed chamber 1, and all such embodiments are within the scope of the present application.

Optionally, the seed crystal holder 2 is made of graphite, so that the escape of gas between the seed crystal 3 and the seed crystal holder 2 is facilitated. In addition, a vacuum area is arranged on one side of the seed crystal holder 2, which is far 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 pressure applying module provided in the embodiment of the present application, the 1 st pressure applying unit 51 is in the shape of a cylinder, and the n th pressure applying unit is in the shape of a hollow cylinder, wherein an end of the cylinder and an end of the hollow cylinder form a pressure applying surface as shown in fig. 4. It should be noted that, 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 of surrounding the 1 st pressing unit 51.

In addition, in other embodiments, the pressing surface of the pressing device 5 may also be a complete surface composed of a plurality of pressing units, as shown in fig. 5, fig. 5 is a schematic top view of another pressing module provided in an embodiment of the present invention, the pressing units are in the shape of prisms, the tips of the prisms form the pressing surface shown in fig. 5, and there is no space between the prism-shaped tips. The prism is not limited to a square, a rectangular parallelepiped, a prism, a trapezoid, and the like, and the present application does not limit this.

In the embodiment of the present application, when the 1 st pressing unit 51 has a cylindrical shape and the n th pressing unit has a hollow cylindrical shape, the wedge shim 6 is an annular wedge ring. The annular wedge ring is composed of a plurality of wedge members so as to be movable from a center toward an edge.

It should be noted that, in all embodiments of the present application, the 1 st to nth pressing units 51 to 51 may apply different pressures to the seed crystal 3, respectively, for example, as shown in fig. 2, when the pressing module 5 has 4 pressing units, the 1 st pressing unit 51 provides 11kg of pressure, the 2 nd pressing unit 52 provides 19kg of pressure, the 3 rd pressing unit 53 provides 27kg of pressure, and the 4 th pressing unit 54 provides 35kg of pressure. Likewise, the 1 st pressing unit 51 to the nth pressing unit can apply the same pressure to the seed crystal 3, and the description thereof is omitted.

The seed crystal 3 and the seed crystal holder 2 are fixed by an adhesive, that is, 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 coated only on the surface of the seed crystal 3 facing the seed holder 2.

The following describes a bonding method provided in an embodiment of the present application, and the bonding method described below may be referred to as a 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 provided by the embodiment of the application. The seed crystal 3 is provided with a first surface 31, the seed holder 2 is provided with a second surface 21, and the first surface 31 and the second surface 21 are fixedly bonded, wherein the bonding method comprises the following steps:

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

Wherein the surface topography information comprises: the total thickness change TTV, the curvature Bow, the warping degree Wrap, the local thickness change LTV and the like of the seed crystal 3 and the seed crystal holder 2.

Step S120: and determining the relative fit mode of the first surface 31 and the second surface 21 based on the surface topography information of the first surface 31 and the surface topography information of the second surface 21.

It should be noted that, referring to fig. 7, fig. 7 is a schematic structural diagram of bonding of a seed crystal and a seed crystal holder provided in the embodiment of the present application, in an ideal case, both the second surface 21 and the first surface 31 are smooth and perfect surfaces, that is, there is no unevenness in the second surface 21 and the first surface 31, and a good bonding effect can be achieved after the adhesive is uniformly applied. However, in practice, whether it is experimental statistics or theoretical analysis, the bonding surface is not a perfect surface, and there are irregularities.

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

It is apparent that the bonding structure of fig. 9 is formed such that the uniformity of the spacing between the seed crystal 3 and the seed receptacle 2 is superior to the bonding structure of fig. 8 in that the uniformity of the spacing between the seed crystal 3 and the seed receptacle 2 is superior. That is, in the non-ideal case (uneven bonding surface), the relative bonding mode is confirmed based on the surface topography information of the first surface 31 and the second surface 21, and in the relative bonding mode, the uniformity of the distance between the seed crystal 3 and the seed crystal 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 attaching 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 relative fit confirming mode in the bonding method can effectively improve the uniformity of the distance 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 due to the uniform distance, is favorable for controlling the nucleation and growth processes in crystal growth, and optimizes the crystal quality. The dosage of the adhesive between the seed crystal 3 and the seed crystal support 2 is relatively reduced, and the adhesive quality between the seed crystal 3 and the seed crystal support 2 is improved while the cost is reduced. 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 the adhesive, the second surface is placed in the bonding device as described in any of the above embodiments, and the seed crystal holder 2 and the seed crystal 3 are bonded and fixed based on the relative bonding manner.

Correspondingly, the method for bonding and fixing the seed crystal holder 2 coated with the adhesive and the seed crystal 3 in the bonding device comprises the following steps:

step S131: and placing the seed crystal holder 2 coated with the adhesive on a heating module 4 of the bonding device for heating so as to remove air bubbles and volatile substances in the adhesive. In the examples of the present application, the volatile substances include organic small molecule substances such as alkanes and alcohols, and inorganic gas phase substances such as water vapor and carbon dioxide.

Meanwhile, the heating module 4 heats the seed crystal support 2 to volatilize volatile substances in the adhesive, so that a cavity generated by the volatile substances rapidly escaping in a subsequent high-temperature process is effectively avoided. In addition, the heating module 4 heats the seed crystal support 2, so that the viscosity coefficient of the adhesive is reduced, a relatively uniform adhesive layer is formed on the seed crystal support 2, and the adhesion effect of the seed crystal 3 and the seed crystal support 2 is improved.

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

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

Step S133: after the pre-bonding fixation is completed, the homogenization molding is performed on the surface of one side of the seed crystal 3 departing from the seed crystal support 2, and the method comprises the following steps: and sequentially controlling the 1 st pressing unit 51 to the nth pressing unit to press the seed crystal 3 through the pressing module 5 of the bonding device, wherein the pressure formed by the mth 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 mth pressure applying unit is greater than the pressure intensity formed by the (m + 1) th pressure applying unit, so that the thickness of an adhesive layer between the seed crystal 3 and the seed crystal support 2 is relatively different, the homogenization treatment is carried out on the surface of the seed crystal 3, the bonding uniformity of the seed crystal 3 and the seed crystal support 2 on each point in space can be improved, meanwhile, most of volatile substances in the adhesive are volatilized in earlier stage, the uniform pressure applying at the moment can not increase the cavity tissue, and the uniform pressure applying can enable the bonding effect of the seed crystal support 2 and the edge region of the seed crystal to be consistent with other regions such as the center, and further the growth quality of the seed crystal 3 is improved.

Accordingly, the method for acquiring the surface topography information of the first surface 31 and the surface topography information of the second surface 21 comprises: 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

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

and the cylindrical coordinate system of z represents the position information of the sampling points. However, in other embodiments, other parameters capable of representing 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).

Correspondingly, determining the relative fitting manner of the first surface 31 and the second surface 21 includes:

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

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

Step S123: fixing the model of the seed crystal holder 2 to rotate the model of the seed crystal 3 based on the set step value through a rotation axis passing through the model center of the seed crystal 3 and the model center of the seed crystal 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 fitting manner is determined based on a state in which the number of contact points between the model of the first surface 31 and the model of the second surface 21 is at most. Wherein, when having a state of the maximum number of the contact points, the space between the seed crystal 3 and the seed tray 2 is the smallest, and the portion capable of generating the cavity tissue is the smallest. Accordingly, the adhesive includes epoxy, silicone, and isopropyl alcohol.

In the bonding method, the relative bonding mode is determined based on the acquired surface topography information of the first surface 31 and the acquired surface topography 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 applies pressure from the 1 st pressure applying unit 51 to the nth pressure applying unit in the bonding device, so that air between the seed crystal 3 and the seed crystal support 2 escapes from inside to outside, the defects of cavities, hexagonal cavities and the like between the seed crystal 3 and the seed crystal support 2 are greatly reduced, and the bonding quality of the seed crystal 3 and the seed crystal support 2 is improved.

In order to make the bonding method provided in the present application more comprehensible, the present application is described in further detail below with reference to the accompanying drawings and specific embodiments.

The embodiment of the application provides a specific bonding method, which comprises the following steps:

step S210: the surface topography information of the first surface 31 of the seed crystal 3 and the surface topography information of the second surface 21 of the seed holder 2 are acquired, 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 to obtain geometric map of the first surface 31 and the second surface 21, and a cylindrical coordinate system is correspondingly established for datamation of the geometric maps 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 origin of the center of a cylindrical coordinate system, the cylindrical coordinate system includes an X axis, a Y axis and a Z axis, the X axis, the Y axis and the Z axis are located in the first surface 31, the X axis, the Y axis and the Z axis are perpendicular to each other, and the coordinate of any point C located on the first surface 31 is taken as the origin of the center of the cylindrical coordinate system

r1 is the distance from the center origin of the projected point of point C on the first surface 31,

is the angle between the line connecting the projected point of the point C on the first surface 31 and the origin of the center and the positive direction of the X axis, and z1 is the distance between the point C and the first surface 31. Correspondingly, the second surface 21 uses the axis of the seed crystal holder 2 as the central origin of the cylindrical coordinate system, and is located at the coordinate of any point D of the second surface 21Is composed of

r2 is the distance from the center origin of the projected point of point D on the second surface 21,

and z2 is the distance between the projection point of the point D on the second surface 21 and the line connecting the center origin and the positive direction of the X axis.

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

TABLE 1 table of information on the position of the sampling point on a seed crystal with a diameter of 100mm

Serial 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, the first term is 0, the tolerance is 0.2mm, the arithmetic sequence pair r1 is taken, the first term is 0, the tolerance is 5 degrees, the arithmetic sequence pair

Taking values to determine different r1 and

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

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

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

Serial 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 attachment manner of the seed crystal 3 and the seed crystal holder 2 is determined as in the above-described steps S121 to S124. Specifically, taking Python language as an example for calculation and analysis, the relative fitting mode of the seed crystal 3 and the seed crystal holder 2 is determined, wherein the core code of the calculation and analysis program is as follows:

in the case of fixing the seed holder 2, the program sets i to have an initial value of 1, j to have an initial value of 0, r to have an initial value of 1, and the variation tolerance based on the radius r to be 0.2, so that the step value d of rotation (i.e., the tolerance d of the rotation angle) satisfies: d is 1/(r 0.2). In addition, f represents the number of sampling points on a certain radius, and f satisfies: f is 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 the initialization of the angle value of the seed crystal 3 and the seed crystal holder 2; after initialization, the first and second pairs

And

the value is assigned to the value to be assigned,

representing various angle values over the traversal radius r

The corresponding point is set to be the point of the corresponding point,

representing various angle values over the traversal radius r

The corresponding point.

Is represented as

Point of time and

coordinate points of the points in time on the XY plane correspond to each other. if abs (z1-z2)<0.3 j + + representation is based on tables 1 and 2

And a correspondence relationship of z1,

and z2, when the absolute value of the difference between z1 and z2 is less than 0.3, it is regarded as contact, and therefore the value of j representing the number of contact points is incremented by 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 after each rotation in the fitting manner (i.e., the relative positional relationship between the seed crystal 3 and the seed holder 2 after i rotations).

In addition, through the program operation, a numdit dictionary database after the seed crystal completes one rotation period (360 °) is obtained. Determining a relative attaching mode by solving i corresponding to the maximum value of j in the dictionary, namely selecting the attaching mode of the seed crystal 3 and the seed crystal holder 2 as the relative attaching mode when the seed crystal rotates for 360/i angle, wherein in the relative attaching mode, the number of contact points of the first surface 31 and the second surface 21 is the largest (namely j is the maximum value), namely 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 the embodiment of the present application, the adhesive is coated on the second surface 21 through a printing process, and specifically, the adhesive is coated on the second surface 21 by using a 3D printing technology.

It should be noted that, the traditional glue application scheme is generally manual glue scraping and glue throwing of a glue throwing machine. The manual glue scraping has great difficulty in realizing uniform gluing, and has various uncontrollable factors such as glue scraping strength, included angle, pushing speed and the like, glue consumption, glue gluing homogenization degree and the like, so that a stable bonding effect is difficult to form, and reliable guarantee cannot be provided for silicon carbide industrialization. For the glue applying scheme of the glue throwing machine, the glue throwing machine uniformly coats the liquid adhesive on the seed crystal by utilizing the action of centrifugal force, and the glue applying uniformity is difficult to ensure by the glue throwing machine because the concentric circles are related to the radius and the centrifugal force between the concentric circles has large difference. The two sizing schemes described above do not allow quantitative analysis of sizing usage.

For above-mentioned two kinds of glueing 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 realize the quantitative control to the glueing quantity through establishing the glueing quantity of coordinate system accurate calculation arbitrary position, can realize the homogenization control of adhesive when can reduce cost. In addition, the 3D printing technology can ensure the bonding effect, simultaneously maximally reduces the using amount of the bonding agent, further maximally reduces the gas generation amount in the bonding process, is favorable for improving the stability of the bonding process, and realizes the large-scale and industrialized preparation of crystals.

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

step S231: the adhesive is disposed and the disposed adhesive is placed in a printing apparatus for use. The adhesive comprises epoxy resin, silicone and isopropanol; wherein, the specific gravity of the adhesive is that the epoxy resin: silicone: isopropyl alcohol: carbon powder is 5-8: 0-3: 0.5-3: 0.5-3. Preferably, in the embodiment of the present application, the adhesive comprises the following components: silicone: isopropyl alcohol: carbon powder 7: 1: 1.5: 0.5. it should be noted that the epoxy resin can be replaced by epoxy resin and phenolic resin, the silicone can be replaced by silicon powder, silane and silicone oil, the isopropyl alcohol can be replaced by propylene glycol, propanol, ethanol and ethylene glycol, and the particle size of the carbon powder is 10nm-100 nm.

Step S232: the second surface 21 is coated with an adhesive by the printing apparatus. Specifically, the method comprises the following steps:

step S232.1: and establishing a cylindrical coordinate system on a computing unit in the printing equipment, and establishing a model of the seed crystal holder 2 and the seed crystal 3 based on a relative fitting mode. And the model center of the seed crystal support 2 is superposed with the model center of the seed crystal 3, and the relative position relation between the model of the seed crystal support 2 and the model of the seed crystal 3 is determined based on the relative fitting mode. In this step, the seed holder 2 model and the seed crystal 3 model are set up in a manner of being attached to each other in a relative positional relationship after the adhesive is applied.

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

Wherein, the distance between the contact positions of the seed crystal 3 and the seed crystal support 2 is 0, the distance between any non-contact position of the seed crystal 3 and the seed crystal support 2 is e, and then the z corresponding to the coordinate point of any non-contact is: z is 0.8 × e + α.

Wherein, alpha is the minimum thickness of glue applied between the seed crystal 3 and the seed crystal support 2, namely the glue applied thickness of the contact point position between the seed crystal 3 and the seed crystal support 2, and is generally 20-50 μm, and preferably, alpha is 25 μm; 0.8 is the blurring factor of the size thickness versus gap distance, i.e. the effective size thickness is a distance of 0.8 × e, which is typically 0.6-0.95, and in the present embodiment is preferably 0.8, which is related to the concentration of adhesive, the pressure of the press module, the curing curve, etc.

Step S232.2: the number w of applications needed at any untouched location is determined based on the height h of a single application of the printing device, and the number w of applications is: w { (H + e) × δ }/H.

Wherein H is the height of single gluing of the printing equipment, H is the gluing thickness when the distance between the seed crystal 3 and the seed crystal support 2 is 0, the gluing thickness of the untouched space position is (H + e) multiplied by delta, and delta is a thickness correction coefficient, and the value of the thickness correction coefficient is usually less than 1. Generally, compared with the seed crystal adopting a silicon carbide semi-insulating substrate, the seed crystal adopting a silicon carbide conductive substrate has a larger thickness coefficient, and the LTV phase difference is larger, so that the thickness correction coefficient delta is larger. Preferably, in the embodiment of the present application, the thickness correction coefficient δ has a value of generally 0.85.

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

In addition, when the dispensing nozzle of the printing apparatus is circular, the printing apparatusThe height h of the single sizing satisfies: h ═ pi θ V₁/4k₁V₂Theta is the diameter of the applicator nozzle, V1 is the dispensing rate of the applicator nozzle, V2 is the rate of movement of the applicator face, k₁As a correction factor, k₁The value is related to the viscosity coefficient of the adhesive, the temperature, the surface tension of the adhesive, the degree of wetting, etc., in the examples of the present application, k₁Has a value of 0.7 to 1, preferably, k₁Is 0.85.

When the glue applying nozzle of the printing equipment is square, the height h of single glue applying of the printing equipment meets the following requirements: h is k₂V₁h₁/V₂，k₂To correct the factor, k₂The value is related to the viscosity coefficient of the adhesive, the temperature, the surface tension of the adhesive, the degree of wetting, etc., in the examples of the present application, k₂Is 0.7-0.95, preferably, k₂Is 0.85. h is₁Is the height of the glue applying nozzle from the glue applying surface.

Step S232.3: the seed crystal support 2 is placed on a working table in printing equipment, after the temperature of the seed crystal support 2 is set to be 30-80 ℃ through the working table, the printing equipment is started to coat the surface of the seed crystal support 2, the position of the seed crystal support 2 is marked after coating is completed, and then the seed crystal support 2 is taken out 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 applies the size at any one position is determined based on the calculated w at that position. By heating the seed crystal support 2, volatile substances such as isopropanol and the like which reduce the viscosity coefficient can timely escape from the adhesive at printing intervals, the coating uniformity of the adhesive is improved, the coating uniformity is better especially when multiple printing areas exist, and the bonding effect of the adhesive is improved.

In the embodiment of the application, in the sizing scheme, a three-dimensional geometric model for sizing is established on a computer according to the distance relationship between the seed crystal 3 and the seed crystal support 2, the prepared adhesive is added into a resin tank of a printer, and a sizing program is set; the sizing process is started from a certain point and then the seed crystal holder 2 is sized evenly. Other sizing methods such as spot sizing or line sizing may be used, which is not limited in the present application.

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

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

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

This step is through holding in the palm 2 the heating process to the seed crystal, and a period of time that stews under the heating condition, can get rid of bubble and volatile substances in the adhesive effectively, avoided the air gathering and volatile substances volatilize the cavity tissue that leads to, higher temperature can reduce the viscosity coefficient of adhesive simultaneously, makes the adhesive hold in the palm 2 surface distribution at the seed crystal even, has improved the bonding quality between seed crystal 3 and the seed crystal holds in the palm 2.

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

step S242.1: after the seed holder 2 is subjected to the heating treatment, the annular wedge-shaped pad 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: and placing the seed crystal 3 on the seed crystal support 2 in the relative attaching mode, then heating the seed crystal support 2 by the heating module 4 at the heating speed of 0.2-4 ℃/min until the target temperature is raised to 80-150 ℃, and keeping the target temperature for 5-60 min.

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

Step S242.3: pressurizing the seed crystal 3 by a pressurizing module 5, wherein the pressurizing module 5 sequentially controls a 1 st pressurizing unit 51 to an nth pressurizing unit to pressurize the seed crystal 3, and the pressure formed by the mth pressurizing unit is greater than the pressure formed by the m +1 th pressurizing unit; m is a positive integer less than n.

Specifically, referring to table 3, table 3 shows pressure data for a pressure module 5 of 4 annular pressure cells and a seed of 6 inches. In the present 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, which are not described in detail in other places in the present application.

TABLE 3 pressure information table formed by pressing seed crystal by No. 1 to No. 4 pressing units

As can be seen from table 3, the 1 st pressing unit 51 applies 11kg of pressure, the 2 nd pressing unit 52 applies 19kg of pressure, the 3 rd pressing unit 53 applies 27kg of pressure, and the 4 th pressing unit 54 applies 35kg of pressure. Obviously, the pressures formed by the 1 st pressure applying unit 51 to the 4 th pressure applying unit 54 are sequentially reduced, and the pressure difference from inside to outside enables the gas between the seed crystal 3 and the seed crystal holder 2 to escape, 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 pressing the pressing unit successively, the driving assembly controls the annular wedge-shaped pad 6 to move outward gradually, and before the nth pressing unit presses, the driving assembly controls the annular wedge-shaped pad 6 to move out between the seed crystal 3 and the seed crystal holder 2. Through the removal of control wedge gasket 6, realized control seed crystal 3 and seed crystal and held in the palm the difference in height between 2, avoided seed crystal 3 to damage because of the extra moment of torsion is too big, simultaneously, wedge gasket 6 holds in the palm the 2 with seed crystal and has the space, holds in the palm 2 for seed crystal 3 and seed crystal between gas provides the passageway of effusion, has ensured gaseous effusion, has improved the bonding quality. Further, taking the example that the pressing module 5 is 4 annular pressing units, the 1 st pressing unit 51, the 2 nd pressing unit 52, the 3 rd pressing unit 53 and the 4 th pressing unit 54 are from the inside to the 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 extracted through the air extraction hole 72, 200sccm protective gas is introduced through the vent hole 71, and the pressure of the chamber 1 is controlled to 80kPa through the air extraction hole 72 and the vent 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, the gas is convenient to escape, and the possibility of gas aggregation is reduced.

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

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 min; the 2 nd pressurizing unit 52 applies 19kg of pressure to the seed crystal 3 and then maintains the pressure for 10 min; the 3 rd pressing unit 53 applies 27kg of pressure to the seed crystal 3 and then maintains the pressure for 10 min; after applying 35kg of pressure to the seed crystal 3 by the 4 th pressing unit 54, the pressure is maintained for 10 min.

Step S243: after the pre-bonding fixation is completed, the surface of one side of the seed crystal 3 departing from the seed crystal support 2 is flattened, and the method comprises the following steps: and sequentially controlling the 1 st pressing unit 51 to the nth pressing unit to press the seed crystal through the pressing module 5 of the bonding device, wherein the pressure formed by the mth pressing unit is equal to the pressure formed by the m +1 th pressing unit.

Specifically, referring to table 4, table 4 shows pressure data for a pressure module 5 of 4 annular pressure units and a seed crystal 3 of 6 inches.

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

As can be seen from table 4, the 1 st pressing unit 51 applies 11kg of pressure, the 2 nd pressing unit 52 applies 33kg of pressure, the 3 rd pressing unit 53 applies 55kg of pressure, and the 4 th pressing unit 54 applies 77kg of pressure. Obviously, the pressure intensity formed by the 1 st pressure applying unit 51 to the 4 th pressure applying unit 54 is equal, the pressure applying units of the pressure applying module 5 apply pressure to the seed crystal 3 to form the same pressure intensity, and then the seed crystal 3 is flattened, so that the flatness of the surface of one side of the seed crystal 3, which is far away from the seed crystal holder 2, is improved, the thermal 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.

It should be noted that, in the embodiment of the present application, the pressure applied by the pressure applying unit to the seed crystal 3 is 0.01-1N/mm²Preferably, the pressure applied to the seed crystal 3 by the pressure applying unit is 0.05-0.5N/mm²。

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

After the pre-bonding fixation is finished, the temperature of the seed crystal support 2 is raised to 135-165 ℃ by the heating module 4 at the heating rate of 0.4-4 ℃/min, and 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 keeping the temperature 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 raises the temperature of the seed crystal holder 2 to 150 ℃ at a heating rate of 1 ℃/min and maintains the temperature at 150 ℃ for 60 min.

The temperature is continuously increased by the heating module 4 at the heating rate of 0.5 ℃/min-5 ℃/min, and when the temperature is increased to 500-800 ℃, the temperature is kept for 40-400 min. After the heat preservation is finished, 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 ℃/min-10 ℃/min-, and the temperature is kept for 60min-300min after the temperature is increased to 900 ℃ -1500 ℃. After the heat preservation is finished, the temperature of the seed crystal support 2 is controlled to be reduced to the room temperature at the cooling speed of 2-20 ℃/min. After the temperature is reduced to the room temperature, introducing protective gas into the chamber 1 until the pressure in the chamber 1 is normal, taking out the bonded seed crystal 3 and the seed crystal holder 2 for later use, and bonding the seed crystal 3 and the seed crystal holder 2 at the moment.

Preferably, the heating module 4 continues to increase the temperature at a heating rate of 2 ℃/min and remains at 600 ℃ for 60min when the temperature is increased to 600 ℃. After the heat preservation is finished, 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 is then increased further by means of the heating module 4 at a heating rate of 4 ℃/min and, after the temperature has increased to 1200 ℃, is held at this temperature for 180 min. After the heat preservation is finished, the temperature of the seed crystal support 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 provides another specific bonding method including:

step S310: and carrying out hydrogen etching treatment on the first surface 31 of the seed crystal 3 to obtain a third surface for bonding, and acquiring surface topography information of the third surface of the seed crystal 3 and the second surface 21 of the seed crystal holder 2, namely characterizing the third surface and the second surface 21. The method of obtaining a third surface for bonding comprises: and introducing 5slm-60slm hydrogen, keeping the temperature at 1550 ℃ for 50min for hydrogen etching treatment, and removing microscopic damage on the first surface 31 of the seed crystal 3 to expose the intrinsic structure layer of the seed crystal.

In addition, after the hydrogen etching treatment, 200sccm of silane is introduced at 1000-1300 ℃ to form a third surface. Preferably, 200sccm of silane is passed at 1050 ℃. The method can eliminate the phenomenon of unbalance of the surface stoichiometric ratio caused by hydrogen etching, and is favorable for 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, for the hydrogen etching treatment of the seed crystal 3, hydrogen gas of 10slm is introduced, the pressure is maintained at 85kPa, and the temperature is maintained at 1850 ℃ for 15min to obtain the third surface. When the seed crystal is a silicon carbide seed crystal, silicon atoms of the seed crystal can be sublimated and carbon atoms can be reconstructed in the process, and finally a graphite layer, namely graphene, is formed on the surface of the silicon carbide seed crystal.

In addition, the characterization of the third surface and the second surface 21 is the same as the characterization of the first surface 31 and the second surface 21 in step S210, and may be referred to each other, so that the description is omitted here.

Step S320: and determining the relative fitting mode of the seed crystal 3 and the seed crystal holder 2 based on the surface topography information of the third surface and the surface topography information of the second surface 21. The principle of step S320 is the same as that of step S210, and the steps may be referred to each other, which is not described herein again.

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

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

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

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

Step S340: and placing the seed crystal support 2 with the second surface 21 coated with the glue A and the seed crystal with the third surface coated with the glue B in a bonding device, and bonding and fixing the seed crystal and the seed crystal support 2 based on a relative bonding mode.

The method for fixing the seed crystal and the seed crystal holder 2 by bonding 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 standing the seed crystal at the temperature for 35-40 min; 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; and finally, the temperature of the seed crystal 3 is controlled to be reduced to the room temperature at the cooling speed of 1-20 ℃/min. This step effectively removes gases and volatile substances in the B glue.

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 20 min; then heating the temperature to 100 ℃ by a heating module 4 at a heating rate of 1 ℃/min, and standing the seed crystal 3 for 15min at 100 ℃; and finally, the temperature of the seed crystal 3 is controlled to be reduced to the room temperature at the cooling speed of 5 ℃/min.

Step S342: the same principle as that of step S241 can be referred to each other, and will not be described herein.

Step S343: the same principle as that of step S242 can be referred to each other, and will not be described herein.

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

To sum up, 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 nth pressing unit are sequentially controlled by the pressing module 5 to press the seed crystal 3, so that air in a cavity between the seed crystal 3 and the seed crystal holder 2 escapes from inside to outside, and the defects of the cavity, the hexagonal cavity and the like existing between the seed crystal 3 and the seed crystal holder 2 are reduced. Meanwhile, the mutual attaching mode is determined for the characterization of the first surface 31 and the second surface 21, the adhesive is coated on the second surface 21 through a printing technology, the space between the seed crystal 3 and the seed crystal support 2 and the using amount of the adhesive are effectively reduced, a cavity between the seed crystal 3 and the seed crystal support 2 is relatively reduced besides the cost is reduced, and the attaching quality of the seed crystal 3 and the seed crystal support 2 is further improved.

The embodiments in the present description are described in a progressive manner, or in a parallel manner, or in a combination of a progressive manner and a parallel manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments can be referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

It should be noted that in the description of the present application, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only used for convenience of description and simplification of the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present application. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or intervening components may also be present.

It is further noted that, herein, relational terms such as first and second, and the like may be 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. Also, 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 an … …" does not exclude the presence of other like elements in an article or device that comprises the 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 seed crystal holds in palm bonding device of bonding, its characterized in that includes:

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

the pressure applying module is positioned on one side of the seed crystal support, which is far away from the heating module, and is used for applying pressure to the seed crystal so as to ensure that the seed crystal is fixedly attached to the seed crystal support; the pressure applying module comprises a 1 st pressure applying unit to an nth pressure applying unit, wherein n is a positive integer greater than 1, and the nth pressure applying unit surrounds an n-1 th pressure applying unit; the pressure applying module is used for sequentially controlling the 1 st to the nth pressure applying units to apply pressure to the seed crystal.

2. The bonding apparatus according to claim 1, wherein the center of the 1 st pressing unit corresponds to the centers of the seed crystal and the seed crystal holder;

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

4. The bonding apparatus according to claim 1, wherein the 1 st pressing unit has a cylindrical shape and the n-th pressing unit has a hollow cylindrical shape.

5. The bonding apparatus according to claim 1, wherein an adhesive is provided between the seed holder and the seed crystal.

6. A method for 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:

after the second surface is coated with the adhesive, the second surface is placed on the bonding device according to any one of claims 1 to 6, and the seed crystal holder and the seed crystal are bonded and fixed based on the relative attaching mode.

7. The bonding method according to claim 6, wherein the method of bonding and fixing the seed crystal holder to which the adhesive is applied and the seed crystal in the bonding apparatus comprises:

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

after the pre-bonding fixation is completed, the surface of one side of the seed crystal departing from the seed crystal support is subjected to homogenization molding, and the method comprises the following steps: and sequentially controlling the 1 st pressing unit to the nth pressing unit to press the seed crystal through the pressing module of the bonding device, wherein the pressure formed by the mth pressing unit is equal to the pressure formed by the m +1 th pressing unit.

8. The bonding method according to claim 6, wherein the method of acquiring the surface topography information of the first surface and the surface topography information of the second surface comprises:

9. The bonding method of claim 6, wherein determining the relative fit of the first surface to the second surface comprises:

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

10. The bonding method of claim 6, wherein the adhesive comprises epoxy, silicone, and isopropyl alcohol.