Method for obtaining (111) crystal face in (001) CVD (Chemical Vapor Deposition) monocrystal diamond

Abstract

The invention discloses a method for obtaining a crystal face (111) in a (001) CVD (Chemical Vapor Deposition) monocrystal diamond, which comprises the following steps of: fixing the monocrystal diamond, enabling femtosecond laser to be vertical to the crystal face (001) of the monocrystal diamond, and scanning by taking the crystal orientation of a diagonal line [110] of the crystal face as a preset path, so that a graphitized modified line is formed in the monocrystal diamond; forming a leap crack along a crystal face (111); pulling force is applied to the single-crystal diamond, so that the single-crystal diamond is separated in the crack direction, and a diamond stripping block is obtained; and cleaning the stripping surface of the diamond stripping block to obtain the crystal face (111) of the monocrystal diamond. As the crystal face (111) is an easy-cleavage face, striding cracks along the crystal face (111) can be formed in the diamond. The crystal face (111) of the single crystal diamond can be obtained in a short time, cold ablation processing of the interior of a material can be achieved in an ultra-short time, and the method has the advantages of being high in efficiency, low in loss, low in cost, capable of simplifying polishing and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor element manufacturing, and in particular relates to a method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In the semiconductor field, diamond is an indirect bandgap semiconductor material with a bandgap width of about 5.2 eV, a thermal conductivity of up to 22 W / (cm·K), and room temperature electron and hole mobilities of up to 4500 cm 2 / (Vs) and 3380cm 2 / (Vs), it has broad application prospects in the field of high-temperature and high-power power electronics and high-frequency and high-power microwave devices. In addition, diamond also has great potential in the preparation of high-power deep ultraviolet light-emitting diodes, and plays an important role in the development of extreme ultraviolet and high-energy particle detectors.

[0004] However, due to the limited reserves of natural diamond resources, high prices and unguaranteed quality, it is difficult to meet the needs of industrial applications. Therefore, artificial synthesis of single crystal diamond is the first step to meet its different application needs. At present, the growth methods of single crystal diamond for semiconductors mainly include microwave plasma chemical vapor deposition (MPCVD) and high temperature and high pressure (HTHP). Diamond (111) crystal plane is easier to achieve P-type doping, and the devices prepared on this crystal plane also have better performance. Therefore, obtaining a (111) crystal plane with a smooth surface and a large effective area on single crystal diamond will help the subsequent application and development of single crystal diamond for semiconductors.

[0005] Research has found that during the growth and epitaxy process, the (111) crystal plane is more likely to grow defects such as twins and stacking faults than the (001) crystal plane, making it difficult to prepare a flat surface. The (111) crystal plane is prone to shrinkage during CVD growth, its growth rate is less than one-tenth of that of the (100) crystal plane, and it is more difficult to polish than the (100) crystal plane.

[0006] Therefore, the commonly used method for obtaining the (111) crystal plane on the diamond single crystal grown from other crystal planes is laser cutting, which is to focus the laser beam on the diamond surface, use high energy to fuse the diamond crystal, and then cool and solidify the molten pool through a high-pressure gas flow to achieve cutting. However, this method has large material loss, long time consumption, high energy consumption, and is easily affected by diamond wear (1. The quality of diamond has a direct impact on its wear resistance and resistance to chipping. High-quality diamond has good wear resistance and can better withstand the high temperature and high pressure generated during laser cutting, thereby maintaining cutting accuracy and efficiency. Low-quality diamonds, on the contrary, are prone to significant wear and chipping during the cutting process, affecting cutting accuracy and production efficiency; 2. As the laser cuts the diamond, the diamond surface will have more serious wear problems due to thermal ablation such as melting, so the subsequent focusing and moving accuracy and efficiency of laser cutting will also be affected). Summary of the invention

[0007] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] A method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond comprises the following steps:

[0010] After the single crystal diamond is fixed, a femtosecond laser is directed perpendicularly to the (001) crystal plane of the single crystal diamond, and the crystal direction

[110] diagonal of the crystal plane is used as a preset path for scanning, so that a graphitization modification line is formed inside the single crystal diamond, and a leapfrogging crack is formed along the (111) crystal plane;

[0011] Applying a tensile force to the single crystal diamond to separate the single crystal diamond along the crack direction to obtain a diamond peeling block;

[0012] After cleaning the peeled surface of the diamond peeling block, the (111) crystal plane of the single crystal diamond is obtained. Since the (111) crystal plane is an easy cleavage plane, a leaping crack along the (111) crystal plane will be formed inside the diamond.

[0013] The leaping cracks are interconnected and cover the preset peeling surface. The closely arranged cracks can significantly reduce the internal binding force of the diamond crystal, and the diamond crystal can be successfully separated under the condition of applying external force.

[0014] In some embodiments, the single crystal diamond is natural diamond or artificial diamond.

[0015] In some embodiments, the focusing depth of the ultrashort pulse laser inside the single crystal diamond is 1 / 2 of the thickness of the single crystal diamond.

[0016] In some embodiments, the (001) crystal plane of the single crystal diamond is a polished surface. In order to achieve successful incidence and scanning of the laser.

[0017] In some embodiments, when separating single crystal diamond, two sides of a leaping crack of the single crystal diamond are bonded and fixed before applying a tensile force to separate the single crystal diamond.

[0018] The non-diamond layer is peeled off by applying glue and then separating with external force, which not only protects the internal structure of the single crystal diamond, but also saves processing time, which is simple and convenient.

[0019] Preferably, after separation is completed, a debonding agent or an organic solvent is used to separate the two separated parts of the single crystal diamond from the separation platform and remove the glue.

[0020] In some embodiments, the method for cleaning the peeling surface of the diamond peeling block is: immersing the diamond peeling block in a cleaning solution, and ultrasonically cleaning the block to remove the graphite remaining on the peeling surface.

[0021] Preferably, the cleaning liquid is a mixture of one or more of deionized water, acetone, ethanol, isopropanol, nitric acid, sulfuric acid or perchloric acid. The strong cavitation effect generated when ultrasonic waves propagate in the liquid can effectively destroy the oxygen-containing functional groups inside the graphite oxide, thereby increasing the escape rate of the graphite oxide, and no impurities are introduced, ensuring the product quality and integrity of the diamond stripping block; in addition, the cavitation effect of ultrasonic waves can increase the reduction rate of graphite oxide in H plasma solution, further accelerating the speed at which the residual graphite on the surface of the stripping layer is separated from the interior of the single crystal diamond.

[0022] In some embodiments, the surface area of ​​the obtained single crystal diamond (111) crystal plane is equal to the vertical cross-sectional area of ​​the single crystal diamond corresponding to the scanning path. times.

[0023] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0024] The present invention uses a block diamond with a (100) crystal plane as the growth plane, and uses ultrafast laser focusing to repeatedly scan inside the diamond crystal until a graphitization modification line is formed in its inner layer. Since the (111) crystal plane is the easy cleavage plane of diamond, a leaping crack along the (111) crystal plane will be formed inside the crystal. Under the action of tension, the diamond crystal is separated. This method can obtain a group of (111) crystal planes on both sides. At the same time, the material processing range is small, the loss is small, the time is short, and the efficiency is high.

[0025] The present invention focuses ultrafast laser on the inside of diamond to achieve cutting. Firstly, the ultrashort pulse laser has a short action time on the material and is not easy to cause thermal damage to the material. Secondly, it acts on the inside of the material and no obvious wear and breakage will occur during the cutting process.

[0026] Ultrafast femtosecond laser technology is used to achieve cold ablation processing inside the material in an ultra-short time, with the advantages of high precision, high stability (in addition to the high stability of high-precision equipment, for a certain diamond crystal, the fact that repeated focusing is not required during processing will also improve its processing stability. For batches of diamond crystals, the application is simple to operate, the effect is stable, and the processing qualification rate can be guaranteed. Therefore, this method has high stability), high efficiency, low loss, low cost and simplified polishing (since this method divides the diamond crystal into two parts, rather than ablating and removing part of the crystal as in conventional laser cutting, the processing area and volume are greatly reduced, which can reduce losses; in addition, the surface roughness of the (111) crystal plane obtained by this method is significantly reduced compared to conventional laser cutting, which can also reduce losses and facilitate subsequent polishing). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 It is a schematic diagram of a flow chart in an embodiment of the present invention.

[0029] Figure 2 Schematic diagram of the structure of the diamond crystal used in the embodiment of the present invention.

[0030] Figure 3 It is a schematic diagram of using an ultrashort pulse laser to focus vertically on the inside of a diamond crystal and scan along a scanning path at a preset depth to form a peeling surface in an embodiment of the present invention.

[0031] Figure 4 Schematic diagram of the diamond peeling surface structure according to an embodiment of the present invention.

[0032] Figure 5 Schematic diagram of crack structure at the diamond peeling surface according to an embodiment of the present invention.

[0033] Figure 6 Schematic diagram of the diamond peeling surface structure according to an embodiment of the present invention. Figure 7 Schematic diagram of crack structure at the diamond peeling surface according to an embodiment of the present invention. Figure 8 Schematic diagram of a diamond stripping block according to an embodiment of the present invention.

[0034] Wherein: 100-diamond single crystal; 101-diamond single crystal (001) crystal plane; 102-diamond single crystal (111) crystal plane; 103-diamond peeling block; 200-laser scanning path; 201-laser scanning modification line inside the diamond single crystal; 202-crack. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0036] The present invention will be further described below in conjunction with the embodiments.

[0037] Example 1

[0038] See also Figure 1 as well as Figures 3 to 5 In an embodiment of the present invention, laser scanning is performed inside a CVD single crystal diamond 100 to obtain a (111) crystal plane 102 of the diamond.

[0039] Specifically, the steps include:

[0040] S1, vertically positioning the focus of a femtosecond laser with a transmittance wavelength at a fixed depth inside the single crystal diamond 100 to perform a single path 200 repeated scan, so that a graphitization modification line 201 is directly formed in the inner layer of the diamond crystal 100, and a leaping crack 202 is formed along the (111) crystal plane;

[0041] S2, fixing the diamond crystal 100 so as to separate the diamond crystal 100 along the crack 202 under the action of tension to obtain a diamond peeling block 103;

[0042] S3, remove the diamond stripping block 103, use ultrasound to clean the graphite on the surface of the diamond, and dry it after cleaning for later use.

[0043] The above steps S1 to S3 are implemented until a group of (111) crystal planes on the diamond peeling block 103 are obtained.

[0044] The pulse width of the ultrashort pulse laser is at the femtosecond level. The laser emits a pulse laser and moves along a preset scanning path 200 to form an extended crack 202 along a preset peeling (111) crystal plane 102 in the diamond. The cracks 202 are interconnected to form a peeling layer 102.

[0045] The focus of the ultrashort pulse laser with a transmittance wavelength is vertically positioned at 1 / 2 of the thickness of the diamond single crystal 100. Of course, the setting method of step S1 is not limited to this, and the focus depth of the ultrashort pulse laser inside the diamond crystal 100 can be changed according to needs.

[0046] like Figure 2 FIG. 1 is a schematic diagram of the structure of the diamond crystal to be processed in this embodiment, which is a CVD single crystal with the (001) plane as the growth plane;

[0047] The diamond crystal 100 may also be an insulating natural diamond or an insulating artificial diamond.

[0048] In order to achieve successful laser incidence and scanning, the (001) crystal plane 101 of the diamond crystal 100 should be a polished surface.

[0049] See also Figure 3 , that is, in this embodiment, an ultrashort pulse laser is vertically focused on the inside of the diamond and scanned along a scanning path at a preset depth to form a peeling surface. In one embodiment of the present application, the preset scanning path 200 is along the diagonal of the (001) crystal plane 101 of the diamond single crystal 100, and by repeatedly scanning 200, the cracks 202 can be connected to each other and then cover the preset peeling surface 102.

[0050] The diamond crystal 100 that has been scanned by the ultrafast laser is coated with special glue on both sides and then bonded to the upper and lower surfaces of the separation platform, and a pulling force is applied to the separation platform to separate the diamond crystal 100.

[0051] The non-diamond layer 102 is peeled off by applying glue and then separating by external force, which not only protects the internal structure of the diamond crystal 100 but also saves processing time, which is simple and convenient.

[0052] like Figure 4 FIG. 1 is a schematic diagram of the structure of the diamond peeling surface in this embodiment. In this embodiment, the surface area of ​​the obtained diamond (111) crystal plane 102 is equal to the vertical cross-sectional area of ​​the diamond crystal 100 corresponding to the scanning path 200. times.

[0053] Please refer to the structural diagram of the cracks on the diamond peeling surface in this embodiment. Figure 5 The cracks 202 are interconnected and then spread all over the preset peeling surface 102. The closely arranged cracks 202 can significantly reduce the internal binding force of the diamond crystal 100, and the diamond crystal 100 can be successfully separated under the condition of applying external force.

[0054] The separated diamond stripping block 103 is separated from the separation platform by using a debonding agent or an organic solvent, and then is put into debonding cleaning and dried for use. Chemical reagents such as acetone used in the debonding process are convenient and easy to obtain, the debonding time is short and the effect is significant, which can save processing time and improve efficiency;

[0055] In step S3, the residual graphite on the surface of the diamond stripping block 103 is cleaned by ultrasonic waves generated by an ultrasonic generator, and then dried for later use. Of course, the solution in the ultrasonic generator is not limited to deionized water. For example, in another embodiment of the present application, placing the solution in an ultrasonic generator filled with ethanol can also achieve beneficial effects;

[0056] In addition to the methods of separating the diamond crystal 100 mentioned in S2 and S3 above, in another embodiment of the present application, the diamond block 100 after laser scanning is placed in an ultrasonic generator containing H plasma solution, the ultrasonic generator is turned on to generate ultrasonic waves, and the electrolysis device is turned on to reduce the diamond crystal 100.

[0057] The strong cavitation effect generated when ultrasonic waves propagate in liquid can effectively destroy the oxygen-containing functional groups inside the graphite oxide, thereby increasing the escape rate of the graphite oxide, and no impurities are introduced, ensuring the product quality and integrity of the diamond stripping block 103. In addition, the cavitation effect of ultrasonic waves can increase the reduction rate of graphite oxide in H plasma solution, further accelerating the speed at which the residual graphite on the surface of the stripping layer 102 is detached from the diamond crystal 100.

[0058] The specific crystal plane of the present invention is obtained by repeatedly scanning an ultrafast laser along a preset path to form a modified layer on the preset peeling surface and then peeling it off. Therefore, it has the beneficial effects brought by the method of obtaining a (111) crystal plane in a (001) CVD single crystal diamond using an ultrafast laser in the above-mentioned embodiment, and will not be described in detail here.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond, characterized in that: The steps include: After the single crystal diamond is fixed, a femtosecond laser is directed perpendicularly to the (001) crystal plane of the single crystal diamond, and the crystal direction [110] diagonal of the crystal plane is used as a preset path for scanning, so that a graphitization modification line is formed inside the single crystal diamond, and a leapfrogging crack is formed along the (111) crystal plane; Applying a tensile force to the single crystal diamond to separate the single crystal diamond along the crack direction to obtain a diamond peeling block; After cleaning the peeled surface of the diamond peeling block, the (111) crystal plane of the single crystal diamond is obtained. Since the (111) crystal plane is an easy cleavage plane, a leaping crack along the (111) crystal plane will be formed inside the diamond.

2. The method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond according to claim 1, characterized in that: The single crystal diamond is natural diamond or artificial diamond.

3. The method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond according to claim 1, characterized in that: The focusing depth of the ultrashort pulse laser inside the single crystal diamond is 1 / 2 of the thickness of the single crystal diamond.

4. The method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond according to claim 1, characterized in that: The (001) crystal plane of single crystal diamond is a polished surface.

5. The method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond according to claim 1, characterized in that: When separating single crystal diamond, two sides of the leaping crack of the single crystal diamond are bonded and fixed, and then a tensile force is applied to separate them.

6. The method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond according to claim 1, characterized in that: After the separation is completed, the two parts of the single crystal diamond that have been pulled apart are separated from the separation platform using a debonding agent or an organic solvent, and the debonding is then performed.

7. The method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond according to claim 1, characterized in that: The method for cleaning the stripping surface of the diamond stripping block is as follows: immersing the diamond stripping block in a cleaning solution, performing ultrasonic cleaning, and removing graphite remaining on the stripping surface.

8. The method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond according to claim 7, characterized in that: The cleaning solution is a H plasma solution.

9. The method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond according to claim 8, characterized in that: The cleaning solution is a mixture of one or more of deionized water, acetone, ethanol, isopropanol, nitric acid, sulfuric acid or perchloric acid.

10. The method for obtaining a (111) crystal plane in a (001) CVD single crystal diamond according to claim 1, characterized in that: The surface area of ​​the obtained single crystal diamond (111) crystal plane is equal to the vertical cross-sectional area of ​​the single crystal diamond corresponding to the scanning path. times.

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