Diamond substrate processing method

Abstract

The invention provides a diamond substrate machining method, and relates to the field of precision machining of superhard materials. The method comprises the following steps: determining a first included angle between a current growth surface of an initial diamond substrate and a standard crystal face; determining a second included angle between the target growth surface of the initial diamond substrate and the standard crystal face; cutting the current growth surface of the initial diamond substrate according to the angle difference between the first included angle and the second included angle and the size of the current growth surface of the initial diamond substrate to obtain a target growth surface of the initial diamond substrate; and processing the target growth surface of the initial diamond substrate to obtain a target diamond substrate. By means of the collaborative process of laser cutting, mechanical grinding and polishing and plasma etching and polishing, surface deviation angle crystal orientation control and sub-nanometer level surface roughness of the diamond substrate are achieved, the machining efficiency is improved, and surface or sub-surface damage is reduced.

Description

Technical Field

[0001] The present invention relates to the field of superhard material precision processing, and in particular to a diamond substrate processing method. Background Art

[0002] Single-crystal diamond, due to its ultra-high thermal conductivity, carrier mobility, and chemical stability, is considered an ideal candidate for next-generation semiconductor materials. High-quality CVD (Chemical Vapor Deposition) diamond is typically grown on HPHT (High Pressure High Temperature) diamond substrates. The surface quality and orientation angle of HPHT diamond directly influence various properties of the epitaxial layer. It is generally believed that lower substrate surface roughness leads to lower surface roughness of the epitaxial layer under the same conditions.

[0003] The substrate surface deflection angle also varies depending on the epitaxial layer requirements, such as slow, high-quality growth, high-speed growth, or doped growth. Due to current processing limitations and diamond's exceptional strength, hardness, and chemical resistance, the processing and preparation of electronic-grade semiconductor diamond or high-quality diamond substrates is extremely difficult.

[0004] Therefore, it is an urgent problem to be solved by those skilled in the art to perform a series of processing on a common diamond turning substrate so that it has a predetermined surface deflection angle and surface roughness. Summary of the Invention

[0005] In view of the above problems, the present invention provides a diamond substrate processing method.

[0006] The present invention provides a diamond substrate processing method, comprising: determining a first angle between a current growth surface of an initial diamond substrate and a standard crystal plane; determining a second angle between a target growth surface of the initial diamond substrate and the standard crystal plane; cutting the current growth surface of the initial diamond substrate according to an angular difference between the first angle and the second angle and a size of the current growth surface of the initial diamond substrate to obtain a target growth surface of the initial diamond substrate; and processing the target growth surface of the initial diamond substrate to obtain a target diamond substrate.

[0007] According to an embodiment of the present invention, an initial diamond substrate is placed in an X-ray orienter; one side of a current growth surface of the initial diamond substrate is kept parallel to a plane formed by incident X-rays and outgoing X-rays of the X-rays to obtain a first surface angle; the current growth surface of the initial diamond substrate is rotated three times along a normal axis of the current growth surface of the diamond substrate to obtain a second surface angle, a third surface angle, and a fourth surface angle in sequence; and the first angle is determined based on the first surface angle, the second surface angle, the third surface angle, and the fourth surface angle.

[0008] According to an embodiment of the present invention, an initial diamond substrate is fixed on a fixture; a laser is incident multiple times in parallel from different positions on the growth surface of the fixed initial diamond substrate; and the current growth surface of the initial diamond substrate is cut multiple times by the multiple incident lasers to obtain a target growth surface of the initial diamond substrate.

[0009] According to an embodiment of the present invention, the laser beam incident multiple times sequentially cuts the current growth surface of the initial diamond substrate at equal intervals from the inside to the outside.

[0010] According to an embodiment of the present invention, the side view of the target growth surface of the initial diamond substrate is a right triangle, and the angle of the smaller acute angle in the right triangle is the angle difference.

[0011] According to an embodiment of the present invention, the target growth surface of the initial diamond substrate is mechanically ground; the target growth surface of the initial diamond substrate after mechanical ground is mechanically polished; and the target growth surface of the initial diamond substrate after mechanical polishing is etched and polished to obtain a target diamond substrate.

[0012] According to an embodiment of the present invention, diamond grinding liquid is used in mechanical grinding and mechanical polishing.

[0013] According to an embodiment of the present invention, mechanical grinding initially causes the surface roughness of the target growth surface of the initial diamond substrate to be less than 20 nm.

[0014] According to an embodiment of the present invention, mechanical polishing further allows the surface roughness of the target growth surface of the initial diamond substrate to be less than 5 nm.

[0015] According to an embodiment of the present invention, etching and polishing ultimately result in a surface roughness of the target growth surface of the initial diamond substrate being less than 1 nm.

[0016] The diamond substrate processing method provided by the present invention can achieve the following beneficial effects:

[0017] Through the collaborative process of laser cutting-mechanical grinding and polishing-plasma etching and polishing, the surface deviation angle crystal orientation control and sub-nanometer surface roughness of the diamond substrate are achieved, which improves processing efficiency and reduces surface or sub-surface damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0019] Figure 1 The flowchart of the method for processing a diamond substrate according to an embodiment of the present invention is schematically shown;

[0020] Figure 2 Schematically showing a principle diagram for calculating the angles between incident and outgoing X-rays and the substrate surface according to an embodiment of the present invention;

[0021] Figure 3 A schematic diagram illustrating a principle diagram for determining a first angle according to an embodiment of the present invention is shown;

[0022] Figure 4 Schematically showing a principle diagram of cutting the target growth surface of an initial diamond substrate according to an embodiment of the present invention;

[0023] Figure 5 The flowchart of obtaining a target diamond substrate according to an embodiment of the present invention is schematically shown.

[0024] Description of Figure Numbers:

[0025] 1-first vertex; 2-second vertex; 3-third vertex; 4-fourth vertex. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0027] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise," "include," etc. used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0028] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0029] Before describing specific embodiments of the present invention in detail, technical terms are first explained to facilitate a better understanding of the present invention.

[0030] Current growth surface: refers to the surface state achieved by the initial surface of the substrate used for depositing material during thin film growth.

[0031] Target growth surface: refers to the surface state that is ultimately desired to be achieved after depositing material on the substrate during thin film growth.

[0032] X-ray orientation meter: an instrument that uses the principle of X-ray diffraction to analyze materials. It is mainly used to measure the angle at which the surface of natural and artificial single crystals deviates from the standard crystal plane.

[0033] Figure 1 The flowchart of the substrate processing method according to the embodiment of the present invention is schematically shown.

[0034] like Figure 1 As shown, the diamond substrate processing method according to an embodiment of the present invention includes steps S1 to S4.

[0035] Step S1, determining a first angle between a current growth surface of an initial diamond substrate and a standard crystal plane.

[0036] For example, standard crystal planes include the (100) crystal plane and the (111) crystal plane. The (100) crystal plane is one of the commonly used crystal planes in silicon-based semiconductors and is also one of the commonly used crystal planes in diamond. It has low surface energy, high electron mobility, and high surface flatness, and has advantages in manufacturing high-performance integrated circuits; the (111) crystal plane has high surface energy, low electron mobility, and has an anisotropic etching effect, can better control the etching shape, and is more suitable for wet etching.

[0037] Step S2: determining a second angle between the target growth surface of the initial diamond substrate and the standard crystal plane.

[0038] Step S3 , cutting the current growth surface of the initial diamond substrate according to the angle difference between the first included angle and the second included angle and the size of the current growth surface of the initial diamond substrate to obtain a target growth surface of the initial diamond substrate.

[0039] The initial diamond substrate to be processed is fixed on a fixture, and the laser is incident parallel to the current surface of the initial diamond substrate fixed on the fixture. The initial diamond substrate is cut into the target growth surface of the initial diamond substrate through multiple laser cuttings of different depths.

[0040] Step S4: processing the target growth surface of the initial diamond substrate to obtain a target diamond substrate.

[0041] The target growth surface of the initial diamond substrate is mechanically ground using a cast iron disk to quickly remove the laser cutting damage layer and reduce the surface roughness, and then mechanical polishing and etching polishing are performed to obtain the target diamond substrate.

[0042] Figure 2Schematically showing a principle diagram for calculating the angles between incident and outgoing X-rays and the substrate surface according to an embodiment of the present invention; Figure 3 The principle diagram of determining the first angle according to an embodiment of the present invention is schematically shown.

[0043] like Figure 2 As shown, the standard crystal plane has a standard angle of ,

[0044] like Figure 3 As shown in the upper part of (a), when the first vertex 1 of the initial diamond substrate is at the upper left corner of the substrate, the initial diamond substrate is placed in the X-ray orientation instrument as the initial position, so that one side of the initial diamond substrate surface is parallel to the plane composed of the incident and outgoing X-rays, as shown in FIG. Figure 3 As shown in the lower part of (a), the incident and outgoing X-rays are incident from the initial diamond substrate surface, and the angles of the incident and outgoing X-rays with the substrate surface are obtained. ,calculate and The difference between the first surface angle ;

[0045] like Figure 3 As shown in the upper part of (b), the initial diamond substrate to be tested is rotated 90° along the normal axis of the current growth surface of the diamond substrate. At this time, the fourth vertex 4 is at the upper left corner of the substrate, as shown in FIG. Figure 3 As shown in the lower part of (b), the incident and outgoing X-rays are incident from the initial diamond substrate surface to obtain the angles of the incident and outgoing X-rays with the substrate surface. ,calculate and The difference between the two surfaces gives the second surface angle ;

[0046] like Figure 3 As shown in the upper part of (c), the initial diamond substrate to be tested is further rotated 90° along the normal axis of the current growth surface of the diamond substrate. At this time, the third vertex 3 is at the upper left corner of the substrate, as shown in FIG. Figure 3 As shown in the lower part of (c), the incident and outgoing X-rays are incident from the initial diamond substrate surface to obtain the angles of the incident and outgoing X-rays with the substrate surface. ,calculate and The difference between the third surface angle ;

[0047] like Figure 3 As shown in the upper part of (d), the initial diamond substrate to be tested is finally rotated 90° along the normal axis of the current growth surface of the diamond substrate. At this time, the second vertex 2 is at the upper left corner of the substrate, as shown in FIG. Figure 3As shown in the lower part of (d), the incident and outgoing X-rays are injected from the initial diamond substrate surface to obtain the angles of the incident and outgoing X-rays with the substrate surface. ,calculate and The difference between the fourth surface angle .

[0048] Next, the first surface angle can be calculated Angle between the second surface The square of the average of the absolute values ​​of and the third surface angle Angle with the fourth surface The first angle can be obtained by taking the square root of the average of the absolute values ​​of .

[0049] For example, the first angle It can be calculated using the following formula:

[0050]

[0051] Figure 4 The schematic diagram shows the principle of cutting the target growth surface of the initial diamond substrate according to an embodiment of the present invention.

[0052] like Figure 4 As shown, according to an embodiment of the present invention, cutting the target growth surface of the initial diamond substrate specifically includes:

[0053] The current growth surface of the initial diamond substrate is cut using multiple lasers at different depths. The cutting direction is from the side away from the diamond substrate surface to the side close to the diamond substrate surface. During laser cutting, the depth of the current growth surface of the initial diamond substrate increases equidistantly, and finally an initial diamond substrate target growth surface at a specific angle is obtained. At this time, the initial diamond substrate target growth surface has cutting damage and a high surface roughness.

[0054] Figure 5 The flowchart of obtaining a target diamond substrate according to an embodiment of the present invention is schematically shown.

[0055] like Figure 5 As shown, according to an embodiment of the present invention, a target diamond substrate is obtained, and the method includes steps S41 to S43.

[0056] Step S41 , mechanically grinding the target growth surface of the initial diamond substrate.

[0057] The initial diamond substrate target growth was mechanically ground using a cast iron disk with diamond grinding fluids of 20 μm, 10 μm and 5 μm particle sizes, quickly removing the laser cutting damage layer and reducing the surface roughness to Ra < 20 nm. At this time, the initial diamond substrate target growth surface exhibited mirror reflection.

[0058] Step S42: mechanically polishing the target growth surface of the initial diamond substrate after mechanical grinding.

[0059] For example, when the target growth surface of the initial diamond substrate exhibits overall mirror reflection, mechanical polishing is performed using a diamond grinding fluid with a particle size less than 1 μm. A cast iron disk can be used with a diamond grinding fluid with a particle size of 0.5 μm to mechanically polish the diamond substrate for 0.5 h. The surface roughness Ra at this time is measured by AFM (Atomic Force Microscope) testing to be 2.036 nm.

[0060] Step S43 , etching and polishing the target growth surface of the initial diamond substrate after mechanical polishing to obtain a target diamond substrate.

[0061] The diamond substrate was plasma etched and polished using 50% O2+50% CF4 as the process gas. The RF power of the etching system was set in the range of 200~500W, the chamber pressure was controlled in the range of 0.01~0.1mbar, and the etching time was 0.3h. The surface roughness Ra was measured by AFM test at this time, which showed that the diamond substrate had a predetermined surface deflection angle and surface roughness Ra<1nm.

[0062] In summary, the embodiments of the present invention provide a diamond substrate processing method, which realizes the surface deviation angle crystal orientation control and sub-nanometer surface roughness of the diamond substrate through the coordinated process of laser cutting-mechanical grinding and polishing-plasma etching and polishing, improves processing efficiency, reduces surface or sub-surface damage, and is used for the preparation of substrates for high-quality CVD diamond epitaxy. The same processing process can be directly used for CVD diamond and can also be used for some other non-diamond substrates.

[0063] It will be understood by those skilled in the art that the features described in the various embodiments of the present invention may be combined and / or coupled in various ways, even if such combinations or couplings are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention may be combined and / or coupled in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or couplings fall within the scope of the present invention.

[0064] The above describes embodiments of the present invention. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be advantageously used in combination. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which are intended to fall within the scope of the present invention.

Claims

1. A diamond substrate processing method, characterized in that: include: determining a first angle between a current growth surface of the initial diamond substrate and a standard crystal plane; determining a second angle between the target growth surface of the initial diamond substrate and the standard crystal plane; cutting the current growth surface of the initial diamond substrate according to the angle difference between the first angle and the second angle and the size of the current growth surface of the initial diamond substrate to obtain the target growth surface of the initial diamond substrate; The target growth surface of the initial diamond substrate is processed to obtain a target diamond substrate.

2. The method according to claim 1, wherein Determining a first angle between the current growth surface of the initial diamond substrate and the standard crystal plane includes: placing the initial diamond substrate into an X-ray orientation instrument; Keeping one characteristic edge of the current growth surface of the initial diamond substrate parallel to the plane formed by the incident X-ray and the outgoing X-ray, thereby obtaining a first surface angle; Rotating the current growth surface of the initial diamond substrate three times along the normal axis of the current growth surface of the diamond substrate to obtain a second surface angle, a third surface angle, and a fourth surface angle in sequence; The first angle is determined by the first surface angle, the second surface angle, the third surface angle and the fourth surface angle.

3. The method according to claim 1, wherein Cutting the current growth surface of the initial diamond substrate to obtain the target growth surface of the initial diamond substrate includes: fixing the initial diamond substrate on a fixture; Allowing laser light to be incident in parallel from multiple positions on the growth surface of the fixed initial diamond substrate; The current growth surface of the initial diamond substrate is cut multiple times by the multiple incident laser beams to obtain the target growth surface of the initial diamond substrate.

4. The method according to claim 3, characterized in that The multiple incident lasers sequentially cut the current growth surface of the initial diamond substrate at equal intervals from the inside to the outside.

5. The method according to claim 3, characterized in that A side view of the target growth surface of the initial diamond substrate is a right triangle, and the angle of the smaller acute angle in the right triangle is the angle difference.

6. The method according to claim 1, wherein The step of processing the target growth surface of the initial diamond substrate to obtain a target diamond substrate comprises: Mechanically grinding the target growth surface of the initial diamond substrate; Mechanically polishing the target growth surface of the initial diamond substrate after mechanical grinding; The target growth surface of the initial diamond substrate after mechanical polishing is etched and polished to obtain the target diamond substrate.

7. The method according to claim 6, characterized in that The mechanical grinding and the mechanical polishing adopt diamond grinding liquid.

8. The method according to claim 6, characterized in that The mechanical grinding initially allows the surface roughness of the target growth surface of the initial diamond substrate to be less than 20 nm.

9. The method according to claim 6, characterized in that The mechanical polishing further allows the surface roughness of the target growth surface of the initial diamond substrate to be less than 5 nm.

10. The method according to claim 6, characterized in that The etching and polishing ultimately results in a surface roughness of the target growth surface of the initial diamond substrate being less than 1 nm.

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