阅读说明：本技术 一种碳化硅晶体的加工方法 (Processing method of silicon carbide crystal ) 是由 贾河顺 周敏 刘圆圆 梁庆瑞 赵吉强 辛鹏波 于 2020-04-08 设计创作，主要内容包括：本发明提供了一种碳化硅晶体的加工方法,该方法包括以下步骤：(1)将碳化硅晶锭进行激光刻蚀,形成所需尺寸的晶体的边界；(2)在所述晶体表面粘附上薄膜后,进行激光辐照；(3)将所述粘附有薄膜的晶体从碳化硅晶锭上剥离下来；(4)将所述晶体与薄膜分离。本发明采用激光刻蚀和激光辐照两次激光处理,使得单位面积内产生更多的应力,在剥离时晶体能够更加弯曲折叠,不影响良率,且可以获得很薄的晶体。本发明可以实现超硬碳化硅晶体的加工,加工工艺简单,成品率高,可以切割成任意尺寸和形状的碳化硅微型晶体；且同时实现了对晶体的减薄处理。(The invention provides a processing method of silicon carbide crystals, which comprises the following steps: (1) carrying out laser etching on the silicon carbide crystal ingot to form a crystal boundary with a required size; (2) after a film is adhered to the surface of the crystal, laser irradiation is carried out; (3) peeling the crystal adhered with the thin film from the silicon carbide crystal ingot; (4) separating the crystal from the film. The invention adopts laser etching and laser irradiation for two times of laser processing, so that more stress is generated in unit area, the crystal can be bent and folded more during stripping, the yield is not influenced, and very thin crystals can be obtained. The invention can realize the processing of the superhard silicon carbide crystal, has simple processing technology and high yield, and can be cut into silicon carbide micro crystals with any size and shape; and simultaneously realizes the thinning treatment of the crystal.)

1. A method of processing a silicon carbide crystal, the method comprising the steps of:

(1) carrying out laser etching on the silicon carbide crystal ingot to form a crystal boundary with a required size;

(2) after a film is adhered to the surface of the crystal, laser irradiation is carried out;

(3) peeling the crystal adhered with the thin film from the silicon carbide crystal ingot;

(4) separating the crystal from the film.

2. The processing method of silicon carbide crystals according to claim 1, wherein in the step (1), the depth of the laser etching is 0.1-1000 μm, and the width of the laser etching is 1-1000 μm;

preferably, the depth of the laser etching is 20-200 μm, and the width of the laser etching is 30-50 μm.

3. The method for processing a silicon carbide crystal according to claim 1, wherein in step (1), the laser is at least one selected from the group consisting of a nanosecond laser and a femtosecond laser;

preferably, the laser is a femtosecond laser;

preferably, the power of the laser is 10-1000W, and the laser etching time is 1-60 s.

4. The method for processing a silicon carbide crystal according to claim 1, wherein in step (2), the film is at least one selected from the group consisting of polydimethylsiloxane-containing film, polyethylene, polyisobutylene and butyl rubber film;

preferably, the film is adhered by one selected from coating and film bonding;

preferably, the thickness of the film is 0.1 to 200 μm.

5. The method for processing a silicon carbide crystal according to claim 1, wherein in step (2), the laser is at least one selected from the group consisting of a nanosecond laser and a femtosecond laser;

preferably, the laser is a femtosecond laser;

preferably, the depth of the laser irradiation is the same as the depth of the laser etching.

6. The method of processing a silicon carbide crystal according to claim 1 wherein in step (3), after cooling, the crystal with the film adhered thereto is peeled from the silicon carbide ingot;

preferably, the cooling is selected from at least one of liquid nitrogen cooling and cooling using a cryogenic box.

7. The method for processing a silicon carbide crystal according to claim 1, wherein in step (4), the thin film on the surface of the crystal is removed by chemical solvent etching to separate the crystal from the thin film;

and/or separating the crystals from the film using a grain picker.

8. Use of the method for processing a silicon carbide crystal according to any one of claims 1 to 7 for producing a silicon carbide nanocrystal.

9. The use according to claim 8, wherein the silicon carbide nanocrystals have a shape selected from at least one of a polygon, a circle, an ellipse, and a profile;

preferably, the silicon carbide nanocrystals are square in shape.

10. The use according to claim 8, wherein the silicon carbide nanocrystals have a thickness of 0.1 to 1000 μm;

preferably, the thickness of the silicon carbide micro-crystal is 20 to 200 μm.

Technical Field

The invention belongs to the technical field of crystal processing, and relates to a processing method of a silicon carbide crystal, in particular to a method for obtaining a crystal with a required size by stripping from a silicon carbide crystal ingot.

Background

The silicon carbide micro crystal is a third-generation wide-bandgap semiconductor material, has excellent properties of high thermal conductivity, high breakdown voltage, extremely high carrier mobility, high chemical stability and the like, can be manufactured into high-frequency and high-power electronic devices and optoelectronic devices which work under the conditions of high temperature and strong radiation, has great application value in the fields of national defense, high technology, industrial production, power supply and power transformation, and is regarded as a third-generation wide-bandgap semiconductor material with great development prospect.

The silicon carbide micro crystal is applied to devices and needs to be processed into crystals with a certain size, and the size of the crystals needed in some fields is micron level or nanometer level. Existing silicon carbide crystal processing techniques involve slicing an ingot into microcrystals of a desired size, such as CN 102514110B. Because the hardness of the silicon carbide crystal is high and is second to diamond, the silicon carbide crystal brings great difficulty to crystal processing, and particularly, the cutting speed is slow and the time is long.

Disclosure of Invention

In order to solve the above technical problems, an object of the present invention is to provide a method for processing a silicon carbide microcrystal, which includes the steps of laser etching, film coating, and laser irradiation, and is capable of cutting a silicon carbide ingot into crystals of any size.

The technical scheme adopted by the invention is as follows:

according to one aspect of the present application, there is provided a method of processing a silicon carbide crystal, the method comprising the steps of:

(1) carrying out laser etching on the silicon carbide crystal ingot to form a boundary of crystals with required size;

(2) after a film is adhered to the surface of the crystal, laser irradiation is carried out;

(3) and peeling the crystal adhered with the thin film from the silicon carbide crystal ingot.

(4) Separating the crystal from the film.

The invention realizes that crystals with required size, especially micro crystals are stripped from the silicon carbide crystal ingot by the steps of laser etching, film coating and laser irradiation of the silicon carbide crystal ingot. Firstly, performing laser etching on the surface of a silicon carbide crystal ingot, and cutting a boundary pattern of a micro crystal with a certain depth and a required size according to the requirement; adhering a film on the surface of the crystal, and then carrying out laser irradiation; laser irradiation not only realizes deep grooving of primary laser and crystal formation defects of an ingot internal structure of secondary laser, but also realizes the denaturation of a thin film so as to be tightly bonded with the crystal, and the crystal and the denatured thin film are conveniently stripped from the ingot together; the peeling of the crystals is achieved by the adhesion of the thin film, and then by separating the micro-crystals from the thin film, crystals of the desired size are obtained. The method has simple processing technology and high yield, and can cut the silicon carbide crystal into silicon carbide crystals with any size.

Further, in the step (1), the depth of the laser etching is 0.1-1000 μm, and the width of the laser etching is 1-1000 μm; preferably, the depth of the laser etching is 20-200 μm, and the width of the laser etching is 30-50 μm. The depth of the laser etch is selected according to the thickness of the crystal of the desired size. The width of the laser etching is determined by the spot diameter of the laser, and is generally 1-3 spot diameters. The purpose of the laser etching is to obtain a pattern of crystals of a desired size, more precisely, the laser etching forms the boundaries of the crystals of the desired size, for example, in the embodiment of the present invention, the desired crystals are squares, the pattern of the desired crystals is obtained by laser etching, the width and depth of the etching form etched trenches, and the trenches surround the perimeter of the desired crystals. Because the inside of the depth of the laser etching generates great internal stress, the unit area generates greater stress, so that the crystal can be bent and folded more during peeling, and the yield is not influenced.

Further, the size of the crystal is micron-scale and/or nanometer-scale, and preferably, the number of the micro-crystal is at least two or more. In a preferred embodiment of the present invention, a plurality of crystals of a desired size are etched on the entire surface of the silicon carbide ingot, and when the plurality of crystals of the desired size are peeled off from the silicon carbide ingot, a thinning process of the silicon carbide ingot is also performed.

Further, in the step (1), the laser is at least one selected from a nanosecond laser and a femtosecond laser; preferably, the laser is a femtosecond laser. Preferably, the power of the laser is 10-1000W, and the laser etching time is 1-60 s. The x-y surface of the needed crystal is formed by the laser etching, and the irradiation intensity and time of the laser etching do not make special requirements as long as the depth required by the etching is met.

Further, in the step (2), the film is at least one selected from polydimethylsiloxane-containing films, polyethylene, polyisobutylene and butyl rubber films. The film has high thermal expansion coefficient, has good bonding effect on silicon carbide crystals, does not influence the crystal lattice structure of the crystals,

preferably, the film is adhered by one selected from the group consisting of coating and film bonding. Preferably, the thickness of the film is 0.1 to 200 μm. The coating liquid or the polymer film can be filled in the etched groove in a mode of coating the coating liquid once and coating the polymer coating liquid for multiple times, the film in the groove plays a certain buffering protection role after being denatured, and can generate large internal stress after being cooled, so that more uniform stress is generated when crystals are adhered to the film and stripped.

Further, in the step (2), the laser is at least one selected from a nanosecond laser and a femtosecond laser; more preferably, the laser is a femtosecond laser. In the step (1), laser etching is performed to obtain an x-y surface of a required crystal, and the laser irradiation in the step (2) causes a defect to be formed at a certain position of the crystal; and by adopting two times of laser processing, more stress is generated in unit area, and the crystal can be bent and folded when being stripped, so that the yield is not influenced.

Preferably, the depth of the laser irradiation is the same as the depth of the laser etching. By regulating and controlling the power density and time of laser etching, the depth of laser irradiation is controlled to be the same as that of laser etching, so that the lower surface of the crystal obtained by stripping is almost flat, and the micro crystal with uniform thickness is obtained. The laser beam in the laser irradiation penetrates into the silicon carbide ingot to a desired depth, i.e., the depth of laser etching, so that a specific layer in the silicon carbide ingot is defective, thereby facilitating peeling. Preferably, the damage in the exfoliation layer of the silicon carbide ingot is caused to propagate less than 2 rayleigh lengths.

Further, in the step (3), after cooling, the crystal adhered with the film is stripped from the silicon carbide crystal ingot; preferably, the cooling is selected from at least one of liquid nitrogen cooling and cooling using a cryogenic box; more preferably, liquid nitrogen cooling is used. The effect of the cooling is to exacerbate the stress that causes the formation of crystal defects.

Furthermore, in the step (4), the film on the surface of the micro crystal is removed by adopting a chemical solvent corrosion method, the micro crystal is separated from the film, and oxygen can be introduced for combustion at the temperature of less than 1500 ℃ before the chemical corrosion. The chemical corrosion can clean the polymer on the crystal surface, and can also remove most of the polymer on the crystal surface by high-temperature oxygen combustion and then remove the polymer more cleanly by chemical corrosion. Or separating the micro crystal from the film by a crystal grain selector, and rapidly removing the crystal bonded on the surface of the film by the crystal grain selector.

According to another aspect of the invention, the application of the processing method of the silicon carbide crystal in manufacturing the silicon carbide microcrystal is provided. The processing method of the invention can obtain silicon carbide micro-crystals with required size and shape.

Further, the shape of the silicon carbide nanocrystal is selected from at least one of a polygon, a circle, an ellipse, and a profile. The polygon is selected from one of a triangle, a square, a regular pentagon, and the like. The profile may include various irregular shapes consisting of curves and lines. More preferably, the silicon carbide nanocrystals are square in shape.

Further, the thickness of the silicon carbide micro crystal is 0.1-1000 μm; preferably, the thickness of the silicon carbide micro-crystal is 20 to 200 μm. The thickness of the silicon carbide micro crystal obtained by the method has a wider range, because the laser etching and the laser irradiation are adopted for twice laser processing, more stress is generated in the unit area of the crystal, so that the required crystal can be bent and folded more when being stripped, and the silicon carbide micro crystal with different thicknesses can be obtained, thereby obtaining the very thin silicon carbide micro crystal.

The invention has the beneficial effects that:

(1) according to the invention, through the steps of laser etching, film coating and laser irradiation of the silicon carbide crystal ingot, the crystal with the required size is stripped from the silicon carbide crystal ingot. The invention adopts laser etching and laser irradiation for two times of laser processing, so that more stress is generated in unit area, the crystal can be bent and folded more during stripping, the yield is not influenced, and the thin silicon carbide micro crystal can be obtained. The invention can not only obtain the crystal with required size, but also realize the thinning treatment of the crystal.

(2) The invention can realize the processing of the superhard silicon carbide micro crystal, has simple processing technology and high yield, and can be cut into the silicon carbide micro crystal with any size. The method can obtain the micro-crystals with various shapes, has wide thickness range of the micro-crystals and can meet the requirements of various fields on the size of the micro-crystals.

Drawings

FIG. 1 is a laser etched pattern in an embodiment of the present invention;

FIG. 2 is a schematic diagram of a laser irradiation configuration in an embodiment of the present invention;

FIG. 3 is a laser etched pattern in another embodiment of the present invention;

FIG. 4 is a laser etched pattern in yet another embodiment of the present invention;

in the figure, the position of the upper end of the main shaft,

1. a silicon carbide ingot; 2. a micro-crystal; 3. a film; 4. a laser device.

Detailed Description

The present invention is described in detail with reference to specific examples, which are provided to facilitate the understanding of the technical solutions of the present invention by those skilled in the art, and the implementation or use of the present invention is not limited by the description of the present invention.

In the present invention, reagents and equipment used are commercially available or commonly used in the art, if not specified.