Polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation and control

Abstract

The invention provides a polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation and control, and relates to the field of ultrahard material ultra-precision machining, the method comprises the steps of mechanical polishing, zeta potential regulation and control rough polishing in chemical mechanical polishing, zeta potential regulation and control fine polishing in chemical mechanical polishing, and cleaning, and finally the polycrystalline diamond with the low-damage and high-quality surface is obtained. By regulating and controlling the zeta potential of the polishing solution in the fine polishing and rough polishing processes, the mechanical damage of the abrasive material in the polishing solution to the polycrystalline diamond can be reduced, and the surface quality of the polished polycrystalline diamond can be improved, so that low-damage and high-quality machining of the polycrystalline diamond is realized.

Description

Technical Field

[0001] The invention relates to the technical field of ultra-precision machining of superhard materials, and in particular to a polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation. Background Art

[0002] Diamond, with its excellent optical, mechanical, and thermal properties, is of great significance for the development of optical windows / fairings used in airborne, missile-borne, and shipborne infrared search and tracking systems, heat dissipation substrates for TR components and high-power devices such as lasers, and tool coatings in cutting and machining. However, the high brittleness, high hardness, and chemical stability of diamond greatly increase the difficulty of subsequent processing, especially for large-sized polycrystalline diamond wafers. The complex polycrystalline orientation characteristics make surface processing control more difficult. The stress, deformation, and sub-surface damage defects associated with the diamond processing process are also difficult problems that need to be solved urgently. At present, ultra-precision processing of large-sized diamonds has become a bottleneck for diamonds in many application fields, and breakthroughs must be made to overcome them, which has become a key obstacle to the application of diamond materials.

[0003] In the face of ultra-precision processing of diamonds, scholars have successively adopted methods based on direct or assisted polishing of energy beams, such as laser polishing, ion beam polishing, and plasma-assisted polishing. However, these new ultra-precision processing methods have problems such as high cost, small sample size, and complex operation. At present, chemical mechanical polishing is still the most effective technical method for ultra-precision polishing of diamonds. In the chemical mechanical polishing process, the polishing process parameters, the components and ratios of the polishing liquid, and the type of polishing pad will have an important impact on the quality of the polished surface. The prior art discloses a polishing liquid for chemical mechanical polishing of single-crystal diamonds and a preparation method thereof. The provided polishing liquid has a large oxidation capacity and removal rate, and realizes high-quality and efficient processing of diamonds. The prior art also discloses a double-sided chemical mechanical polishing method for single-crystal diamond wafers. By preparing a polishing liquid with environmentally friendly reagents such as ursolic acid, iodine, and kerosene as the main components, the single-crystal diamond wafers are rough polished and fine polished to solve the problems of many scratches and large damage layers in traditional mechanical grinding. The above two methods both achieve high-quality processing of diamonds by improving the components of the polishing liquid, but cannot achieve control and complete removal of diamond surface damage during polishing. Therefore, it is necessary to propose a new chemical mechanical polishing method to obtain high-quality polycrystalline diamond with low / no damage. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides the following technical solutions:

[0005] A polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation, comprising:

[0006] Step S1: Mechanical polishing

[0007] Fix the polycrystalline diamond film on the quartz plate, prepare diamond liquid with a particle size of 10-20μm for rough polishing, and then use diamond liquid with a particle size of 1-5μm for fine polishing;

[0008] Step S2: Rough polishing with zeta potential control

[0009] Polishing liquid A is prepared and its zeta potential is adjusted so that the zeta potential difference between it and the polycrystalline diamond film is in the range of -80~-110mV (i.e., the zeta potential value of the diamond film minus the zeta potential value of the polishing liquid A), and the polycrystalline diamond film after mechanical polishing is placed on a polyurethane polishing pad for polishing; by controlling a larger potential difference, the repulsion between the hard abrasive and the surface of the diamond film can be achieved, thereby reducing the damage of the hard abrasive to the surface of the diamond film;

[0010] Step S3: Fine polishing with zeta potential control

[0011] Polishing liquid B is prepared and the zeta potential of polishing liquid B is adjusted so that the zeta potential difference between it and the polycrystalline diamond film is in the range of -5~-30mV (i.e., the zeta potential value of the diamond film minus the zeta potential value of polishing liquid B). The polycrystalline diamond film after rough polishing is placed on the flannel polishing pad and the polycrystalline diamond film is continued to be finely polished. By controlling a smaller potential difference, the repulsion between the soft abrasive and the surface of the diamond film can be reduced, thereby enhancing the polishing of the diamond film surface by the soft abrasive;

[0012] Step S4: Cleaning

[0013] The polished polycrystalline diamond film was cleaned with acetone, alcohol and deionized water in turn.

[0014] The reason why the zeta potential difference between the polishing liquid A and the polycrystalline diamond film in step S2 is large is to ensure that the electrostatic repulsion between the polishing liquid A and the polycrystalline diamond film is large, and the damage of the hard abrasive in the polishing liquid A to the surface of the polycrystalline diamond film is reduced; the reason why the zeta potential difference between the polishing liquid B and the polycrystalline diamond film in step S3 is small is to ensure that the electrostatic repulsion between the polishing liquid A and the polycrystalline diamond film is small, and the polishing effect of the soft abrasive in the polishing liquid B on the surface of the polycrystalline diamond film is increased, so as to obtain a polycrystalline diamond film with better surface quality.

[0015] Preferably, the polishing disk for mechanical polishing in step S1 is a cast iron disk, and the rotation speed of the cast iron disk during rough polishing and fine polishing is 30-200 r / min, the load pressure is 0.5-3 MPa, and the grinding time is 30-120 min.

[0016] Preferably, in step S2, the components of the polishing liquid A include K2FeO4, H2O2, CH3COOH, single crystal diamond powder (abrasive) and deionized water, wherein the K2FeO4 content is 30-50 g / L, the H2O2 content is 20-60 g / L, the CH3COOH content is 15-30 g / L, and the particle size of the single crystal diamond powder is 50-100 nm and the content is 70-100 g / L.

[0017] Preferably, the zeta potential of the polishing liquid A in step S2 is adjusted by changing the pH value of the polishing liquid A. The pH value of the polishing liquid A is adjusted by NaOH and / or HCl solution. The pH value of the polishing liquid A is 4-9, and the corresponding zeta potential value of the polishing liquid A is -15~-40mV. The DLS particle size distribution of the single crystal diamond in the polishing liquid is 150-200nm (diamond powder will agglomerate in the solution), and the zeta potential value of the diamond film surface is -5~-150mV.

[0018] Preferably, in step S2, the polishing disc rotation speed is 50-200 r / min, the polishing pressure is 100-800 kPa, the polishing liquid flow rate is 2-10 ml / min, and the polishing time is 40-180 min.

[0019] Preferably, in step S3, the components of polishing liquid B include SiO2 (abrasive), sodium methylene bis naphthalene sulfonate, polyethylene glycol and deionized water, wherein the particle size of SiO2 powder is 10-60nm, the content is 20-40g / L, the content of sodium methylene bis naphthalene sulfonate is 1-5g / L, and the content of polyethylene glycol is 30-60g / L. The compositions of polishing liquid A and polishing liquid B in the present invention are specially designed to adapt to the polishing system of the present invention, especially for hard abrasive and soft abrasive polishing, respectively, and can further improve the polishing effect of the present invention.

[0020] Preferably, in step S3, the zeta potential of polishing liquid B is adjusted by changing the pH value of polishing liquid B, the pH value of polishing liquid B is adjusted by NaOH and / or HCl solution, the pH value of polishing liquid B is 2-10, the corresponding zeta potential value of polishing liquid A is 0~-50mV, the DLS particle size distribution of SiO2 in the polishing liquid is 40-100nm (SiO2 will agglomerate in the solution), and the zeta potential value of the diamond film surface is -5~-150mV. In the present invention, the process conditions of steps S2 and S3 are selected by comprehensively considering the cost and polishing effect.

[0021] Preferably, in step S3, the polishing disc rotation speed is 30-100 r / min, the polishing pressure is 50-300 kPa, the polishing liquid flow rate is 2-10 ml / min, and the polishing time is 30-120 min.

[0022] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0023] The present invention is the first to use zeta potential regulation for polishing diamond films. In the chemical mechanical polishing process of the present invention, the polycrystalline diamond film has a large negative zeta potential value, and there will be an electrostatic attraction between the abrasive and the abrasive in a liquid environment. In the rough polishing process of zeta potential regulation, the diamond abrasive with a negative zeta potential in the polishing liquid A has the same sign as the zeta potential of the polycrystalline diamond film. By adjusting the zeta potential, a large electrostatic repulsion between the two can be achieved, and the mechanical damage of the diamond abrasive to the polycrystalline diamond film can be reduced, thereby achieving low-damage and high-efficiency processing of superhard abrasives; in the fine polishing process of zeta potential regulation, although the SiO2 abrasive in the polishing liquid B has the same sign as the zeta potential of the polycrystalline diamond film, by adjusting the zeta potential, a small electrostatic repulsion between the two can be achieved, the adsorption behavior of the SiO2 abrasive is enhanced, and the mechanical energy field effect is strengthened, thereby achieving high-quality processing of soft abrasives. In summary, the polycrystalline diamond chemical mechanical polishing using two-step zeta potential regulation can achieve low-damage, high-efficiency, and high-quality processing of polycrystalline diamond films. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 It is a process flow chart of the present invention;

[0026] FIG2( a ) is an AFM surface morphology image of a polycrystalline diamond film after mechanical polishing in a comparative example;

[0027] FIG2( b ) is an AFM surface morphology image of the polycrystalline diamond film after chemical mechanical polishing in Example 2;

[0028] FIG2( c ) is the surface contour of the sample after polishing in the comparative example and embodiment 2;

[0029] Figure 3 This is the SEM image of the surface of the polycrystalline diamond film of Example 2 after chemical mechanical polishing. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0031] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0032] In the embodiments of the present invention, "image" and "picture" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express are the same. "of", "corresponding" and "corresponding" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express are the same.

[0033] In the embodiments of the present invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are consistent.

[0034] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] A polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation, the specific process is as follows Figure 1 As shown, the following steps are included:

[0037] S1 Mechanical polishing: Use paraffin wax to fix the polycrystalline diamond film on the quartz plate, place it in a fixture, use a cast iron disc as the polishing disc, first prepare a 10μm particle size diamond liquid for rough polishing, the cast iron disc speed is 200r / min, the load pressure is 2MPa, and the grinding time is 120min; then use a 2μm particle size diamond liquid for fine polishing; the cast iron disc speed is 100r / min, the load pressure is 1MPa, and the grinding time is 60min during fine polishing;

[0038] S2 zeta potential controlled rough polishing: prepare polishing liquid A, put the polycrystalline diamond film after mechanical polishing on the polyurethane polishing pad for polishing, the K2FeO4 content in polishing liquid A is 30g / L, the H2O2 content is 20g / L, the CH3COOH content is 15g / L, the particle size of the single crystal diamond powder is 50nm, and the content is 70g / L. The zeta potential value of polishing liquid A is adjusted by changing the pH value of the solution. The pH value of polishing liquid A is 6, and the corresponding zeta potential value of polishing liquid A is -20mV. The DLS particle size distribution of single crystal diamond in the polishing liquid is 174nm, and the zeta potential value range of the diamond film surface is -100mV. The polishing disk speed is 150r / min, the polishing pressure is 600kPa, the polishing liquid flow rate is 5ml / min, and the polishing time is 100min.

[0039] S3 zeta potential controlled fine polishing: prepare polishing liquid B, replace the polyurethane polishing pad used in rough polishing with a flannel polishing pad, and continue fine polishing the polycrystalline diamond film. The particle size of SiO2 powder in polishing liquid B is 30nm, the content is 20g / L, the content of sodium methylene bisnaphthalene sulfonate is 1g / L, and the content of polyethylene glycol is 30g / L. The zeta potential value of polishing liquid B is adjusted by changing the pH value of the solution. The pH value of polishing liquid B is 3, and the corresponding zeta potential value of polishing liquid B is 0mV. The DLS particle size distribution of SiO2 in the polishing liquid is 45nm, and the zeta potential value of the diamond film surface is -5mV. The polishing disc speed is 50r / min, the polishing pressure is 100kPa, the polishing liquid flow rate is 5ml / min, and the polishing time is 60min.

[0040] S4 Cleaning: Use acetone, alcohol, and deionized water to clean the polished polycrystalline diamond film in turn.

[0041] Example 2

[0042] A polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation comprises the following steps:

[0043] S1 Mechanical polishing: Use paraffin wax to fix the polycrystalline diamond film on the quartz plate, place it in a fixture, use a cast iron disc as the polishing disc, first prepare a 15μm particle size diamond liquid for rough polishing, the cast iron disc speed is 200r / min, the load pressure is 2.5MPa, and the grinding time is 120min; then use a 1μm particle size diamond liquid for fine polishing; the cast iron disc speed is 50r / min, the load pressure is 1MPa, and the grinding time is 60min;

[0044] S2 zeta potential controlled rough polishing: prepare polishing liquid A, put the polycrystalline diamond film after mechanical polishing on the polyurethane polishing pad for polishing, the K2FeO4 content in the polishing liquid A is 40g / L, the H2O2 content is 40g / L, the CH3COOH content is 20g / L, the particle size of the single crystal diamond powder is 70nm, and the content is 80g / L. The zeta potential value of the polishing liquid A is adjusted by changing the pH value of the solution. The pH value of the polishing liquid A is 8, and the corresponding zeta potential value of the polishing liquid A is -30mV. The DLS particle size distribution of the single crystal diamond in the polishing liquid is 170nm, and the zeta potential value range of the diamond film surface is -120mV. The polishing disk speed is 180r / min, the polishing pressure is 700kPa, the polishing liquid flow rate is 6ml / min, and the polishing time is 150min.

[0045] S3 zeta potential controlled fine polishing: prepare polishing liquid B, replace the polyurethane polishing pad used in rough polishing with a flannel polishing pad, and continue fine polishing the polycrystalline diamond film. The particle size of SiO2 powder in polishing liquid B is 50nm, the content is 30g / L, the content of sodium methylene bisnaphthalene sulfonate is 1g / L, and the content of polyethylene glycol is 40g / L. The zeta potential value of polishing liquid B is adjusted by changing the pH value of the solution. The pH value of polishing liquid B is 4, and the corresponding zeta potential value of polishing liquid B is -15mV. The DLS particle size distribution of SiO2 in the polishing liquid is 42nm, and the zeta potential value of the diamond film surface is -20mV. The polishing disc speed is 70r / min, the polishing pressure is 200kPa, the polishing liquid flow rate is 6ml / min, and the polishing time is 60min.

[0046] S4 Cleaning: Use acetone, alcohol, and deionized water to clean the polished polycrystalline diamond film in turn.

[0047] From Figure 2 (a), Figure 2 (b), Figure 2 (c) and Figure 3 It can be seen that the surface roughness of the diamond film polished by the polishing method of the present invention is significantly better than the surface roughness of the diamond film polished by mechanical polishing.

[0048] Example 3

[0049] A polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation comprises the following steps:

[0050] S1 Mechanical polishing: Use paraffin wax to fix the polycrystalline diamond film on the quartz plate, place it in a fixture, use a cast iron disc as the polishing disc, first prepare a 20μm particle size diamond liquid for rough polishing, the cast iron disc speed is 200r / min, the load pressure is 3MPa, and the grinding time is 120min; then use a 1μm particle size diamond liquid for fine polishing; the cast iron disc speed is 50r / min, the load pressure is 2MPa, and the grinding time is 60min during fine polishing;

[0051] S2 zeta potential controlled rough polishing: prepare polishing liquid A, put the polycrystalline diamond film after mechanical polishing on the polyurethane polishing pad for polishing, the K2FeO4 content in the polishing liquid A is 50g / L, the H2O2 content is 60g / L, the CH3COOH content is 30g / L, the particle size of the single crystal diamond powder is 80nm, and the content is 100g / L. The zeta potential value of the polishing liquid A is adjusted by changing the pH value of the solution. The pH value of the polishing liquid A is 9, and the corresponding zeta potential value of the polishing liquid A is -20mV. The DLS particle size distribution of the single crystal diamond in the polishing liquid is 180nm, and the zeta potential value range of the diamond film surface is -130mV. The polishing disk speed is 200r / min, the polishing pressure is 800kPa, the polishing liquid flow rate is 8ml / min, and the polishing time is 150min;

[0052] S3 zeta potential controlled fine polishing: prepare polishing liquid B, replace the polyurethane polishing pad used in rough polishing with a flannel polishing pad, and continue fine polishing the polycrystalline diamond film. The particle size of SiO2 powder in polishing liquid B is 60nm, the content is 40g / L, the content of sodium methylene bisnaphthalene sulfonate is 1g / L, and the content of polyethylene glycol is 50g / L. The zeta potential value of polishing liquid B is adjusted by changing the pH value of the solution. The pH value of polishing liquid B is 5, and the corresponding zeta potential value of polishing liquid B is -55mV. The DLS particle size distribution of SiO2 in the polishing liquid is 50nm, and the zeta potential value of the diamond film surface is -75mV. The polishing disc speed is 90r / min, the polishing pressure is 300kPa, the polishing liquid flow rate is 7ml / min, and the polishing time is 60min.

[0053] S4 Cleaning: Use acetone, alcohol, and deionized water to clean the polished polycrystalline diamond film in turn.

[0054] Comparative Example 1

[0055] The polycrystalline diamond film was fixed on the quartz plate with paraffin wax and placed in a fixture. A cast iron disc was used as the polishing disc. First, a diamond liquid with a particle size of 15 μm was prepared for rough polishing. During rough polishing, the rotation speed of the cast iron disc was 200 r / min, the load pressure was 2.5 MPa, and the grinding time was 120 min. Then, a diamond liquid with a particle size of 1 μm was used for fine polishing. During fine polishing, the rotation speed of the cast iron disc was 50 r / min, the load pressure was 1 MPa, and the grinding time was 60 min.

[0056] Comparative Example 2

[0057] A polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation comprises the following steps:

[0058] S1 Mechanical polishing: Use paraffin wax to fix the polycrystalline diamond film on the quartz plate, place it in a fixture, use a cast iron disc as the polishing disc, first prepare a 15μm particle size diamond liquid for rough polishing, the cast iron disc speed is 200r / min, the load pressure is 2.5MPa, and the grinding time is 120min; then use a 1μm particle size diamond liquid for fine polishing; the cast iron disc speed is 50r / min, the load pressure is 1MPa, and the grinding time is 60min;

[0059] S2 zeta potential controlled rough polishing: prepare polishing liquid A, put the polycrystalline diamond film after mechanical polishing on the polyurethane polishing pad for polishing, the K2FeO4 content in the polishing liquid A is 40g / L, the H2O2 content is 40g / L, the CH3COOH content is 20g / L, the particle size of the single crystal diamond powder is 70nm, and the content is 80g / L. The zeta potential value of the polishing liquid A is adjusted by changing the pH value of the solution. The pH value of the polishing liquid A is 8, and the corresponding zeta potential value of the polishing liquid A is -30mV. The DLS particle size distribution of the single crystal diamond in the polishing liquid is 170nm, and the zeta potential value range of the diamond film surface is -120mV. The polishing disk speed is 180r / min, the polishing pressure is 700kPa, the polishing liquid flow rate is 6ml / min, and the polishing time is 150min.

[0060] S3 Cleaning: Use acetone, alcohol, and deionized water to clean the polished polycrystalline diamond film in turn.

[0061] Performance Testing:

[0062] The roughness of the polycrystalline diamond films polished in Examples 1 to 3 and the comparative example was tested.

[0063] Compared with the polishing quality, the specific results are shown in Table 1:

[0064] Table 1

[0065]

[0066] Result analysis: By comparing the examples and comparative examples, it can be seen that the surface roughness Ra of the polycrystalline diamond film can reach 0.56nm by first mechanically polishing the polycrystalline diamond film and then performing chemical mechanical polishing with two-step zeta potential control, thereby obtaining a polycrystalline diamond film with a high-quality surface. At the same time, if the zeta potential is not within the range defined by the present invention, the polycrystalline diamond film with a high-quality surface of the present invention cannot be obtained.

[0067] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation, characterized in that: include: Step S1: Mechanical polishing Fix the polycrystalline diamond film on the quartz plate, prepare diamond liquid with a particle size of 10-20μm for rough polishing, and then use diamond liquid with a particle size of 1-5μm for fine polishing; Step S2: Rough polishing with zeta potential control Polishing liquid A containing hard abrasive is prepared and the zeta potential of the polishing liquid A is adjusted so that the zeta potential difference between the polishing liquid A and the polycrystalline diamond film is in the range of -80 to -110 mV, and the polycrystalline diamond film after mechanical polishing is placed on a polyurethane polishing pad for polishing; Step S3: Fine polishing with zeta potential control Prepare polishing liquid B containing soft abrasive and adjust the zeta potential of polishing liquid B so that the difference between its zeta potential and that of the polycrystalline diamond film is in the range of -5 to -30 mV. Place the polycrystalline diamond film after rough polishing on a flannel polishing pad and continue to fine polish the polycrystalline diamond film. Step S4: Cleaning The polished polycrystalline diamond film was cleaned with acetone, alcohol and deionized water in turn.

2. The method according to claim 1, characterized in that: The polishing disc for mechanical polishing in step S1 is a cast iron disc. During rough polishing and fine polishing, the rotation speed of the cast iron disc is 30-200 r / min, the load pressure is 0.5-3 MPa, and the grinding time is 30-120 min.

3. The method according to claim 1, characterized in that In step S2, the components of polishing liquid A include K2FeO4, H2O2, CH3COOH, single crystal diamond powder and deionized water, wherein the K2FeO4 content is 30-50g / L, the H2O2 content is 20-60g / L, the CH3COOH content is 15-30g / L, and the particle size of the single crystal diamond powder is 50-100nm and the content is 70-100g / L.

4. The method according to claim 1, characterized in that: In step S2, the zeta potential of polishing liquid A is adjusted by changing the pH value of polishing liquid A. The pH value of polishing liquid A is adjusted by NaOH and / or HCl solution. The pH value of polishing liquid A is 4-9, and the corresponding zeta potential value of polishing liquid A is -15~-40mV. The DLS particle size distribution of single crystal diamond in the polishing liquid is 150-200nm, and the zeta potential value of the diamond surface is -5~-150mV.

5. The method according to claim 1, characterized in that In step S2, the polishing disc rotation speed is 50-200 r / min, the polishing pressure is 100-800 kPa, the polishing liquid flow rate is 2-10 ml / min, and the polishing time is 40-180 min.

6. The method according to claim 1, characterized in that In step S3, the components of polishing liquid B include SiO2, sodium methylene bisnaphthalene sulfonate, polyethylene glycol and deionized water, wherein the particle size of SiO2 powder is 10-60nm and the content is 20-40g / L, the content of sodium methylene bisnaphthalene sulfonate is 1-5g / L, and the content of polyethylene glycol is 30-60g / L.

7. The method according to claim 1, characterized in that In step S3, the zeta potential of polishing liquid B is adjusted by changing the pH value of polishing liquid B. The pH value of polishing liquid B is adjusted by NaOH and / or HCl solution. The pH value of polishing liquid B is 2-10, and the corresponding zeta potential value of polishing liquid B is 0~-50mV. The DLS particle size distribution of SiO2 in the polishing liquid is 40-100nm, and the zeta potential value of the diamond film surface is -5~-150mV.

8. The method according to claim 1, characterized in that: In step S3, the polishing disc rotation speed is 30-100 r / min, the polishing pressure is 50-300 kPa, the polishing liquid flow rate is 2-10 ml / min, and the polishing time is 30-120 min.

9. A polycrystalline diamond chemical mechanical polishing method based on two-step zeta potential regulation according to any one of claims 1 to 8, to obtain polycrystalline diamond with low damage and high quality surface.

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