A high-precision repairing method of diamond substrate

Abstract

A high-precision repairing method of diamond substrate, comprising the following steps: (1) acid cooking the rough ground diamond substrate surface, and then washing the surface with deionized water; (2) depositing a material having catalytic effect on the conversion of diamond and carbon-based material on the diamond substrate surface; (3) using high-energy electron beam as a heat source to bombard the diamond substrate surface after the catalytic material is deposited in step (2), so that part of the catalytic material enters the stress damage layer of the diamond surface; (4) soft polishing the diamond substrate surface after the bombardment in step (3), so as to realize the best surface roughness of the diamond substrate. The application creatively uses the material having catalytic effect on the conversion of diamond and carbon-based material, realizes the effective removal of the stress damage layer of the diamond substrate surface, reduces the substrate surface roughness, and the diamond substrate reaches the surface roughness of 0.1 nanometer level.

Description

Technical Field

[0001] This invention relates to a method for finely repairing diamond substrates to achieve a roughness of 0.1 nanometers, belonging to the field of crystal material processing technology. Background Technology

[0002] Diamond possesses high thermal conductivity, a wide bandgap, and extremely high hardness, making it widely applicable in semiconductor technology. As diamond dimensions increase, the growth of epitaxial films places higher demands on the surface processing of diamond substrates, with roughness progressing from the nanometer scale to 0.1 nanometers. As the hardest material in nature, diamond is extremely difficult to polish; traditional processing methods mainly include mechanical polishing and chemical-assisted mechanical polishing.

[0003] Mechanical polishing is mainly used for rough grinding of diamond substrates. It typically uses a high-speed rotating cast iron disc with a layer of diamond micro powder coated on the disc surface. The diamond substrate is planarized mechanically, which has high processing efficiency. The surface roughness of the diamond substrate after processing is generally around 10 nm. A stress damage layer of tens to hundreds of nanometers will be formed on the surface of the processed substrate.

[0004] Chemically assisted mechanical polishing (CEM) is characterized by the free distribution of abrasive particles within a slurry containing some chemically corrosive components. During processing, the slurry is continuously fed to a polishing pad or disc that does not contain abrasive particles. The rotation of the polishing pad / disc causes friction between the free abrasive particles and the diamond substrate. This friction is further aided by load, temperature, or chemical reactions, resulting in the removal of material from the diamond surface. The chemical reaction of the slurry and the mechanical action of the abrasive play crucial roles, especially the corrosive effect of the slurry on the diamond surface, which significantly impacts material removal and polishing quality. This processing method is relatively inefficient, typically resulting in a surface roughness of 1-3 nm on the processed diamond substrate, and the formation of a stress damage layer of approximately tens of nanometers on the substrate surface.

[0005] Another approach to high-precision machining of single-crystal diamond is to avoid excessive mechanical action that could directly break and remove carbon atoms from the diamond. Non-abrasive polishing methods have been widely studied. Polishing single-crystal diamond with carbon-soluble metals or metal oxides produces a smoother surface compared to mechanical polishing, but requires high-speed, high-pressure contact or a high-temperature environment to reach the critical chemical reaction conditions.

[0006] Currently, there are still many difficulties in polishing 0.1 nanometer-scale diamond substrates.

[0007] CN113206007A discloses a method for preparing an indium phosphide substrate, which includes the steps of cutting, back-side grinding, front-side thinning, etching, polishing, cleaning, and packaging. This method treats the front and back sides of the wafer separately by combining grinding with thinning, achieving a main surface roughness Ra value of 100-150 nm before CMP polishing. This significantly reduces the thickness of the substrate damage layer before polishing and greatly shortens the CMP polishing time for the indium phosphide substrate. It solves a series of problems in current indium phosphide substrate manufacturing processes, such as high substrate surface mechanical damage rate, thick mechanical damage layer, poor surface roughness, and poor flatness consistency caused by double-sided grinding processes.

[0008] CN115746712A discloses a polishing composition for polishing silicon substrates and its preparation method, comprising: taking a colloidal silica dispersion, obtaining an active silica solution from an organosilicon compound and a catalyst, adding the active silica solution to the colloidal silica dispersion to obtain a mixture in which a coating film is formed on the surface of silica particles; concentrating and displacing, sequentially adding an oxidant, a surfactant, an antifoaming agent, a pH adjuster, and water, so that the final mixture contains 5-10 wt% colloidal silica and has a pH value of 10.5-11.5. By coating the surface of silica particles with a nanofilm, surface scratches during the fine polishing process of silicon wafers can be effectively reduced.

[0009] The methods described above all reduce the substrate damage layer simply by polishing the silicon substrate or by adjusting the polishing material, and none of them can achieve a diamond substrate at the 0.1 nanometer scale. Summary of the Invention

[0010] This invention addresses the shortcomings of existing diamond substrate damage layer repair technologies by providing a high-precision repair method for diamond substrates. This method enables the processing of diamond substrates with a surface roughness of 0.1 nanometers, while simultaneously achieving effective removal of the stress damage layer on the diamond substrate surface, thereby reducing the substrate surface roughness.

[0011] The high-precision repair method for diamond substrates of the present invention includes the following steps:

[0012] (1) The surface of the coarsely ground diamond substrate is acid-boiled and then cleaned with deionized water.

[0013] (2) Depositing a material on the surface of a diamond substrate that catalyzes the conversion of diamond and carbon-based materials;

[0014] (3) Using a high-energy electron beam as a heat source, bombard the surface of the diamond substrate after the catalytic material is deposited in step (2) to allow some of the catalytic material to enter the stress damage layer on the diamond surface.

[0015] The electron beam energy and bombardment time are optimized according to the different needs of the catalytic materials.

[0016] (4) Perform soft polishing on the surface of the diamond substrate after bombardment in step (3) to achieve the optimal surface roughness of the diamond substrate.

[0017] For different catalyst materials, it is necessary to optimize parameters such as polishing time and polishing pressure. This step can be performed using a polishing pad.

[0018] The rough grinding in step (1) refers to the surface roughness Ra of the diamond substrate being no greater than 50 nanometers after mechanical polishing.

[0019] The acid boiling in step (1) refers to soaking in concentrated hydrochloric acid (20%-40% by mass) or concentrated sulfuric acid (75% or more by mass) at 70-90 degrees Celsius in a water bath for 3-10 minutes.

[0020] The surface cleaning in step (1) is performed by using an ultrasonic cleaner to clean the surface with acetone and ethanol for 5 minutes each, and then cleaning it with deionized water at least 3 times.

[0021] The catalytic materials used in step (2) include hexagonal boron nitride, cobalt, iron, and nickel. Deposition is performed using equipment such as magnetron sputtering and atomic layer deposition.

[0022] In step (2), the thickness of the catalytic material deposited on the diamond substrate surface is 50-200 nanometers.

[0023] In step (3), the electron beam bombardment voltage is 6 kV, the current is 150 mA, the operating temperature is 1300 degrees, and the bombardment time is 3-5 minutes.

[0024] In step (4), the polishing temperature for soft polishing is 600-800 degrees Celsius, and the polishing time is 30 minutes to remove the mechanical damage layer of diamond.

[0025] This invention creatively utilizes materials that have a catalytic effect on the conversion of diamond and carbon-based materials (such as hexagonal boron nitride, cobalt-based, iron-based, and nickel-based metals) to effectively remove the stress damage layer on the surface of diamond substrates, thereby reducing the surface roughness of the substrates to the level of 0.1 nanometers. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the surface of a roughly ground diamond substrate.

[0027] Figure 2 This is a schematic diagram showing the deposition of catalytic materials (such as hexagonal boron nitride, cobalt, iron, and nickel thin films) on a diamond substrate.

[0028] Figure 3This is a schematic diagram showing the catalytic material entering the stress-damaged layer on the diamond surface after bombardment of the diamond substrate surface.

[0029] Figure 4 This is a schematic diagram of a diamond substrate after surface soft polishing.

[0030] In the figure: 1. Diamond substrate, 2. Deposited layer. Detailed Implementation

[0031] Example

[0032] The method for fine polishing of diamond substrates according to the present invention mainly includes the following steps:

[0033] 1. After mechanical polishing, the diamond substrate has a surface roughness Ra ≤ 50 nanometers. See [reference needed]. Figure 1 .

[0034] After rough polishing, place the diamond substrate in a 30% hydrochloric acid solution (the concentration can be selected within the range of 20%-40%) or a 70% or higher concentrated sulfuric acid solution, heat it in a water bath at 70-90 degrees Celsius, and soak it for 3-10 minutes. Then, use an ultrasonic cleaner to clean it with acetone and ethanol for 5 minutes each; finally, clean the surface with deionized water at least 3 times.

[0035] 2. Using an electron beam evaporation stage, deposit a 100 nm (selectable within the range of 50-200 nm) metallic nickel thin film (or hexagonal boron nitride, cobalt, iron, or other thin film materials) on the surface of diamond substrate 1, so that the surface of diamond substrate 1 has a deposited layer 2. See [link to documentation]. Figure 2 .

[0036] 3. The surface of diamond substrate 1 is bombarded using an electron beam treatment device. The electron beam bombardment voltage is 6 kV, the current is 150 mA, the operating temperature is 1300 degrees Celsius, and the bombardment time is 3-5 minutes. This allows metallic nickel (catalyst material) to penetrate the surface stress-damaged layer of diamond substrate 1. See [link to documentation]. Figure 3 .

[0037] 4. Use a copper disc to mechanically polish the diamond substrate from step 3 at a temperature of 600-800 degrees Celsius for 30 minutes to remove the mechanically damaged layer of the diamond.

[0038] The surface roughness of diamond substrates can reach 0.1 nm. (See [reference needed]) Figure 4 .

Claims

1. A high-precision repair method for diamond substrates, characterized in that, Includes the following steps: (1) The surface of the coarsely ground diamond substrate is acid boiled and then cleaned with deionized water; (2) Depositing a material on the surface of a diamond substrate that catalyzes the conversion of diamond and carbon-based materials; (3) Using a high-energy electron beam as a heat source, bombard the surface of the diamond substrate after the catalytic material is deposited in step (2) to allow some of the catalytic material to enter the stress damage layer on the diamond surface. (4) Perform soft polishing on the surface of the diamond substrate after bombardment in step (3) to achieve the best surface roughness of the diamond substrate; The catalytic materials in step (2) include hexagonal boron nitride, cobalt, iron, and nickel; In step (3), the electron beam bombardment voltage is 6 kV, the current is 150 mA, the operating temperature is 1300 degrees, and the bombardment time is 3-5 minutes.

2. The high-precision repair method for diamond substrates according to claim 1, characterized in that, The rough grinding in step (1) refers to the surface roughness Ra of the diamond substrate being no more than 50 nanometers after mechanical polishing.

3. The high-precision repair method for diamond substrates according to claim 1, characterized in that, The acid boiling in step (1) refers to soaking in concentrated hydrochloric acid (20%-40% by mass) or concentrated sulfuric acid (75% or more by mass) at 70-90 degrees Celsius in a water bath for 3-10 minutes.

4. The high-precision repair method for diamond substrates according to claim 1, characterized in that, The surface to be cleaned in step (1) is cleaned with acetone and ethanol for 5 minutes each using an ultrasonic cleaner, and then cleaned with deionized water for at least 3 times.

5. The high-precision repair method for diamond substrates according to claim 1, characterized in that, In step (2), the thickness of the catalytic material deposited on the diamond substrate surface is 50-200 nanometers.

6. The high-precision repair method for diamond substrates according to claim 1, characterized in that, In step (4), the polishing temperature for soft polishing is 600-800 degrees Celsius, and the polishing time is 30 minutes to remove the mechanical damage layer of diamond.

Images