Polishing solution for diamond and chemical mechanical polishing method for diamond

Abstract

The invention relates to the technical field of diamond precision machining, and provides a polishing solution for diamond and a diamond chemical mechanical polishing method. The polishing solution for the diamond is formed by mixing and uniformly stirring deionized water, diamond micro-powder, iron powder, a catalyst and a dispersing agent; the grinding aid comprises the following components in percentage by weight: 50%-68% of deionized water, 10%-40% of diamond micro powder, 10%-35% of iron powder, 2%-5% of a catalyst and 0.1%-0.5% of a dispersing agent. By adding the iron powder into the polishing solution, the iron powder can reduce the activation energy of diamond graphitization and catalyze the diamond surface, and the catalytic action aggravates the conversion from diamond to graphite, so that the diamond surface becomes very soft, and carbon atoms on the diamond surface are easier to separate. And the polishing and removing process of the diamond material is accelerated through the catalysis effect of the iron powder, so that ideal surface quality and precision can be achieved in a short time during diamond polishing.

Description

Technical Field

[0001] The present application relates to the technical field of diamond precision machining, and in particular provides a diamond polishing liquid and a diamond chemical mechanical polishing method. Background Art

[0002] As a material with extremely high hardness and brittleness, diamond has extremely high hardness, wear resistance and excellent thermal conductivity. Due to these excellent properties, diamond is widely used in ultra-precision machining, optics and semiconductor fields. Moreover, with the continuous advancement of science and technology, diamond is also the core material of the fifth generation of semiconductors, so it is very important to achieve efficient ultra-precision machining and manufacturing of diamond.

[0003] There are two major difficulties in the field of diamond grinding and polishing: on the one hand, diamond is extremely hard and usually requires a large polishing load to remove material, so scratches, pits and other surface / sub-surface damage are easily generated during the polishing process; on the other hand, the elastic limit of diamond is very close to its strength limit. When the load it bears exceeds the elastic limit, fracture damage will occur. Therefore, diamond is very easy to break during polishing.

[0004] Chemical Mechanical Polishing (CMP) is a combination of mechanical grinding and chemical etching. It uses ultra-fine ion grinding and chemical etching of slurry to form a smooth surface on the surface of the polished medium. It is one of the better processes for polishing diamonds. However, the known polishing liquid used in the current chemical mechanical polishing process has a poor chemical effect on diamonds, and the material removal rate is low, resulting in the diamond surface roughness not meeting the requirements of precision processing. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a diamond polishing liquid and a diamond chemical mechanical polishing method, aiming to solve the problem that the existing polishing liquid has a low material removal rate for diamond in the chemical mechanical polishing process, resulting in the diamond surface roughness not meeting the precision processing requirements.

[0006] To achieve the above purpose, the technical solution adopted in the embodiment of the present application is:

[0007] In a first aspect, an embodiment of the present application provides a polishing liquid for diamond, wherein the polishing liquid is prepared by mixing deionized water, diamond powder, iron powder, a catalyst and a dispersant and stirring them evenly; the weight percentage of each component is: 50%-68% of the deionized water, 10%-40% of the diamond powder, 10%-35% of the iron powder, 2% to 5% of the catalyst, and 0.1% to 0.5% of the dispersant.

[0008] The diamond polishing liquid of the present application has the following beneficial effects: the diamond micropowder and iron powder play a dual role in mechanical and chemical grinding and polishing of diamonds; by adding iron powder to the polishing liquid, the iron powder can reduce the activation energy of diamond graphitization and catalyze the diamond surface. This catalytic effect accelerates the transformation of diamond to graphite, making the diamond surface very soft, so that carbon atoms on the diamond surface are easier to detach. The catalytic effect of iron powder greatly accelerates the polishing and removal process of diamond materials, so that diamond polishing can achieve ideal surface quality and precision in a short time, and improve the efficiency of diamond polishing.

[0009] In some embodiments, the purity of the iron powder is 90% or more.

[0010] By adopting the above technical solution, pure iron powder with higher purity is used, which has better chemical and physical properties.

[0011] In some embodiments, the iron powder has a particle size ranging from 40 to 150 μm.

[0012] By adopting the above technical solution, the iron powder is ultrafine powder, and the reaction activity is higher.

[0013] In some embodiments, the particle size of the diamond powder is in the range of 1 to 2 μm.

[0014] By adopting the above technical solution, the particle size of the diamond powder is not much different from that of the iron powder, ensuring the uniformity of the polishing liquid.

[0015] By adopting the above technical solution, diamond micropowder is used to remove impurities on the surface of diamond and reduce the surface roughness of diamond.

[0016] In some embodiments, the catalyst includes one or more of copper oxide, chromium oxide, titanium dioxide, and cerium oxide; and / or the dispersant includes one or more of sodium dodecyl sulfate, polyacrylic acid, and polyethylene glycol.

[0017] By adopting the above technical solution, the catalyst can promote the electron transfer between carbon atoms and iron atoms; the dispersant can increase the dispersibility of the polishing liquid.

[0018] In a second aspect, an embodiment of the present application provides a diamond chemical mechanical polishing method, which uses the diamond polishing liquid; comprising the following steps: preparing the polishing liquid; mixing diamond powder, iron powder, deionized water, a catalyst and an oxidant in a preset weight ratio to prepare the polishing liquid; polishing the diamond using a chemical mechanical polishing device; the chemical mechanical polishing device includes a polishing disk and a stage; placing the diamond on the stage and in contact with the polishing disk, and driving the stage and the polishing disk to rotate; and dripping the polishing liquid onto the surface of the polishing disk.

[0019] In some embodiments, the step of fixing the diamond on the stage and contacting the polishing disc, and driving the stage and the polishing disc to rotate, includes: using a cast iron disc as the polishing disc.

[0020] By adopting the above technical solution, iron filings can be generated during the grinding process between the polishing disc and the diamond, thereby improving the catalytic effect on the diamond.

[0021] In some embodiments, the step of mixing diamond powder, iron powder, deionized water, a catalyst and an oxidant in a preset weight ratio to prepare the polishing liquid includes: mixing diamond powder, iron powder, deionized water, a catalyst and an oxidant in a preset weight ratio and performing magnetic stirring.

[0022] By adopting the above technical solution, the polishing liquid mixture is fully stirred by magnetic stirring.

[0023] In some embodiments, the step of mixing diamond powder, iron powder, deionized water, a catalyst and an oxidant in a preset weight ratio to prepare the polishing liquid includes: mixing diamond powder, iron powder, deionized water, a catalyst and an oxidant in a preset weight ratio and then subjecting them to ultrasonic vibration.

[0024] By adopting the above technical solution, ultrasonic equipment is used to perform ultrasonic vibration on the polishing liquid, so that the components of the polishing liquid are dispersed more evenly and stably.

[0025] In some embodiments, the flow range of the polishing liquid is configured to be 10-20 ml / min; and / or, the rotation speed range of the stage is: 50-80 r / min; and / or, the rotation speed range of the rotating disk is 60-80 r / min. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative work.

[0027] Figure 1 A flow chart of a gold diamond chemical mechanical polishing method provided by an embodiment of the present invention;

[0028] Figure 2 A structural schematic diagram of a diamond polishing process using a chemical mechanical polishing device provided in an embodiment of the present invention.

[0029] Among them, the reference numerals in the figure are:

[0030] 100. Chemical mechanical polishing equipment; 10. Polishing disc; 20. Stage; 30. Rotating table;

[0031] 40. Polish the catheter. DETAILED DESCRIPTION

[0032] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0033] In the description of the present application, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0035] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0036] At present, diamond is widely used in ultra-precision machining, optics and semiconductor fields; especially diamond has become the core material of the fifth-generation semiconductor, so efficient ultra-precision machining and manufacturing of diamond wafers is crucial. Chemical Mechanical Polishing (CMP) is a combination of mechanical grinding and chemical corrosion. It uses ultra-fine ion grinding and chemical corrosion of slurry to form a smooth surface on the surface of the ground medium. It is one of the better processes for polishing diamond. However, the known polishing liquid used in the current chemical mechanical polishing process has a poor chemical effect on diamond, and the low material removal rate causes the diamond surface roughness to fail to meet the requirements of precision machining.

[0037] In view of this, the present application provides a polishing liquid for diamonds. By adding iron powder to the polishing liquid, the iron powder can reduce the activation energy of diamond graphitization and catalyze the surface of the diamond. This catalytic effect accelerates the transformation of diamonds into graphite, making the surface of the diamond very soft, so that the carbon atoms on the surface of the diamond are easier to detach. The catalytic effect of the iron powder greatly accelerates the polishing and removal process of the diamond material, and the diamond particle powder and the iron powder play a dual role in mechanical and chemical grinding and polishing of diamonds, so that the diamond polishing can achieve the ideal surface quality and precision in a short time, and improve the efficiency of diamond polishing.

[0038] Please refer to Figure 1 , Figure 2 The present application provides a diamond chemical mechanical polishing method for grinding and polishing diamond, comprising the following steps:

[0039] S101, preparing a polishing liquid; mixing diamond powder, iron powder, deionized water, a catalyst and an oxidant according to a preset weight ratio to prepare a polishing liquid.

[0040] In some embodiments, the polishing liquid is prepared by mixing deionized water, diamond powder, iron powder, a catalyst and a dispersant and stirring them evenly; the weight percentage of each component is: deionized water 50%-68%, diamond powder 10%-40%, iron powder 10%-35%, catalyst 2%~5%, dispersant 0.1%~0.5%.

[0041] In some embodiments, the particle size of the diamond powder is in the range of 1 to 2 um. The particle size of the diamond powder can be 1.0 um, 1.2 um, 1.4 um, 1.6 um, 1.8 um, 2.0 um, etc.

[0042] It can be understood that diamond powder is used to remove impurities on the surface of diamond and reduce the surface roughness of diamond. If the particle size of diamond powder is too small, the polishing removal rate will be low, prolonging the polishing time, increasing the production cost of diamond, and increasing the probability of diamond powder agglomeration, making the surface roughness of diamond after polishing more different. If the particle size of diamond powder is too large, the surface roughness of diamond will increase, and it is easy to damage the surface of diamond, reducing the final polishing effect.

[0043] The content of diamond powder affects the polishing effect of diamond. If the content of diamond powder is too small, the removal rate of diamond will be slow, the polishing time will be extended, and the production cost will be increased. If the content of diamond powder is too much, the diamond powder will easily agglomerate in the polishing liquid, resulting in a decrease in the polishing effect.

[0044] In some embodiments, the particle size of the iron powder ranges from 40 to 150 um. The particle size of the iron powder can be 40 um, 60 um, 80 um, 100 um, 120 um, 130 um, 150 um, etc.

[0045] Specifically, the specific mechanism of the addition of iron powder on catalysis of diamond is as follows: from the perspective of electron transfer changing chemical bonds and thermodynamics, the unpaired electrons in the valence electron layer of iron atoms interact with the electrons of diamond atoms to form chemical bonds, which have an attractive effect on diamond atoms, causing them to gradually change into a graphite structure; specifically, iron atoms have unpaired free electrons in 3d orbitals, and these free electrons are transferred to diamond carbon atoms, which will cause the interlayer binding energy of carbon-carbon bonds between different layers to change, reducing the activation energy required to cause the diamond to undergo graphitization transformation, and then the iron atoms in the iron powder have a significant catalytic effect on the diamond graphitization chemical reaction, which can accelerate the graphitization process of diamond.

[0046] Furthermore, the presence of iron atoms in the iron powder will reduce the transition temperature of diamond graphitization. For example, diamond graphitization under vacuum conditions needs to be carried out at a high temperature of 1700K, but under the catalytic effect of iron powder, this transition temperature is reduced to 1000-1700K. As the grinding process in chemical mechanical polishing proceeds, the temperature at the grinding site increases. When the activation energy temperature of the electron-induced effect of the iron atoms is reached, the diamond undergoes a graphitization transition. Therefore, the strong affinity between iron atoms and carbon atoms in diamond at high temperatures is utilized. During the polishing process, the activation energy of diamond graphitization is reduced by adding iron powder, and the diamond surface is catalyzed. This catalytic effect intensifies the transformation of diamond to graphite, making the diamond surface very soft, thereby making it easier for carbon atoms on the diamond surface to detach. The catalytic effect of iron powder greatly accelerates the removal process of diamond materials, allowing diamond polishing to achieve ideal surface quality and precision in a short time, and improving the polishing efficiency of diamond.

[0047] Understandably, the iron powder has a smaller particle size, better particle dispersibility, and better reaction activation. The particle size of diamond micropowder is not much different from that of iron powder, which is conducive to improving the uniformity of the polishing liquid.

[0048] In some embodiments, diamond powder plays a mechanical polishing role, and iron powder plays a chemical polishing role. The dominant position of mechanical polishing and chemical polishing in polishing is controlled by adjusting the ratio between diamond powder and iron powder in the polishing liquid.

[0049] The catalyst for diamond of the present application plays a dual role of mechanical and chemical in diamond grinding and polishing through diamond particle powder and iron powder; by adding iron powder to the polishing liquid, the iron powder can reduce the activation energy of diamond graphitization and catalyze the diamond surface. This catalytic effect accelerates the transformation of diamond into graphite, making the diamond surface very soft, so that carbon atoms on the diamond surface are easier to detach. The catalytic effect of iron powder greatly accelerates the polishing and removal process of diamond materials, so that diamond polishing can achieve ideal surface quality and precision in a short time, and improve the efficiency of diamond polishing.

[0050] In some embodiments, the purity of the iron powder is 90% or above. Using pure iron powder with higher purity has better chemical and physical properties.

[0051] In some embodiments, the catalyst includes one or more of copper oxide, chromium oxide, titanium dioxide and cerium oxide; the catalyst can interact with carbon atoms on the surface of diamond during the reaction, promote electron transfer between carbon atoms and iron atoms, weaken the strength of carbon-carbon bonds, and reduce the activation energy of diamond graphitization.

[0052] In yet other embodiments, the dispersant includes one or more of sodium lauryl sulfate, polyacrylic acid, and polyethylene glycol.

[0053] Specifically, the dispersant can increase the dispersibility of the polishing liquid, maintain the dispersed state of solid particles in the polishing liquid, prevent their precipitation and aggregation, maintain the stability and uniformity of the polishing liquid, and improve the polishing effect of the polishing liquid.

[0054] In some embodiments, diamond powder, iron powder, deionized water, a catalyst and an oxidant are mixed in a preset weight ratio and magnetically stirred to achieve sufficient stirring of the polishing liquid mixture; in an exemplary embodiment, the duration of the magnetic stirring may be 1 hour.

[0055] In some embodiments, during the stirring process of the polishing liquid, an ultrasonic device is used to perform ultrasonic vibration on the polishing liquid so that the components of the polishing liquid are dispersed more evenly and stably. For example, the ultrasonic vibration duration can be 10 minutes.

[0056] S102, polishing the diamond using a chemical mechanical polishing device 100; the chemical mechanical polishing device 100 includes a polishing disc 10 and a stage 20; fixing the diamond on the stage 20 and contacting the polishing disc 10, and driving the stage 20 and the polishing disc 10 to rotate.

[0057] refer to Figure 2 , a chemical mechanical polishing device 100 is used to perform chemical mechanical polishing on diamond. The polishing object of the present application can be a diamond wafer or a diamond wafer. The chemical mechanical polishing process (CMP) is widely used in the semiconductor industry to globally flatten the wafer through chemical mechanical grinding.

[0058] Specifically, the polishing disc 10 is arranged on a rotating table 30, and the rotating table 30 can drive the polishing disc 10 to rotate; the stage 20 is located above the polishing disc 10, and the diamond is arranged on the stage 20. The stage 20 applies downward pressure to the diamond to press the diamond on the polishing disc 10. The polishing disc 10 supports the diamond, and the stage 20 can also rotate to drive the diamond to rotate; the polishing disc 10 and the stage 20 are controlled to rotate simultaneously to ensure uniform mechanical grinding between the diamond surface and the polishing disc 10.

[0059] In some embodiments, a cast iron disc is used as the polishing disc 10. It can be understood that since iron atoms can reduce the activation energy of diamond graphitization and catalyze the diamond surface, the cast iron disc is used as the polishing disc 10, and iron filings can be generated during the grinding process between the polishing disc 10 and the diamond, thereby improving the catalytic effect on the diamond.

[0060] S103 , dripping polishing liquid onto the surface of the polishing disc 10 .

[0061] It can be understood that during the grinding process between the diamond and the polishing disk 10, the polishing liquid is pre-stored in the polishing duct 40, the polishing liquid is dripped into the polishing duct 40, and a groove for the circulation of the polishing liquid is formed on the upper surface of the polishing disk 10. The polishing liquid is evenly formed between the diamond and the polishing disk 10 under the transmission of the polishing disk 10 and the action of centrifugal force.

[0062] Specifically, the iron powder and other ingredients in the polishing liquid react chemically with the diamond, and the diamond surface reacts with the cast iron powder to graphitize, making the surface of the diamond crystal very soft, making it easier for the carbon atoms on the surface of the diamond crystal to detach. At the same time, the mechanical friction generated by the diamond powder in the polishing liquid on the diamond removes the excess material on the diamond surface. Under the dual effects of mechanical and chemical, the surface material is evenly removed to achieve the effect of polishing and leveling.

[0063] In some embodiments, the polishing liquid flow rate ranges from 10-20 ml / min.

[0064] In some embodiments, the polishing liquid flow rate may be 10 ml / min, 12 ml / min, 14 ml / min, 16 ml / min, 18 ml / min, 20 ml / min, etc., so as to ensure that the polishing liquid can be evenly formed between the diamond and the polishing disk 10 .

[0065] In some embodiments, the rotation speed of the stage 20 ranges from 50 rpm to 80 rpm. The rotation speed of the stage 20 may specifically be 50 rpm, 60 rpm, 70 rpm, 80 rpm, etc.

[0066] In some embodiments, the rotation speed of the polishing disk 10 ranges from 60 to 80 r / min, and the rotation speed of the polishing disk 10 can specifically be 60 rpm, 65 rpm, 70 rpm, 75 rpm, 80 rpm, etc.

[0067] Embodiment 1

[0068] Polishing liquid A was prepared, and the weight percentage of each component was: 50% deionized water, 30% diamond powder with a particle size of 2 μm, 15% iron powder with a particle size of 50 nm, 4.5% catalyst, and 0.5% dispersant.

[0069] Specifically, the weight of deionized water is 200 g; copper oxide is used as the catalyst; and polyethylene glycol is used as the dispersant.

[0070] The weighed raw materials of the polishing liquid are mixed and subjected to magnetic stirring for 1 hour and ultrasonic vibration for 10 minutes to prepare polishing liquid A; the mass percentage of diamond micropowder in polishing liquid A is greater than the mass percentage of iron powder, that is, polishing liquid A is a polishing liquid dominated by mechanical grinding and polishing.

[0071] Embodiment 2

[0072] Polishing liquid B was prepared, and the weight percentage of each component was: 50% deionized water, 10% diamond powder with a particle size of 2 μm, 35% iron powder with a particle size of 50 nm, 4.5% catalyst, and 0.5% dispersant.

[0073] Specifically, the weight of deionized water is 200 g; copper oxide is used as the catalyst; and polyethylene glycol is used as the dispersant.

[0074] The weighed raw materials of the polishing liquid are mixed and subjected to magnetic stirring for 1 hour and ultrasonic vibration for 10 minutes to prepare polishing liquid B; the mass percentage of diamond micropowder in polishing liquid B is less than the mass percentage of iron powder, that is, polishing liquid B is a polishing liquid dominated by iron-carbon affinity chemical reaction.

[0075] Referring to Table 1, the present application further provides a comparative experiment of the surface roughness of diamond after grinding and polishing diamond using the diamond chemical mechanical polishing method of the present application using three groups of polishing solutions A, B, and C. It can be understood that all experimental parameters except the polishing solution are consistent during the experiment.

[0076] The experimental parameters in each group are as follows: the initial roughness (Ra) value of the diamond before each experiment is 1um; the grinding and polishing time of the diamond is 80min; the polishing pressure is 2Mpa; the rotation speed of the stage 20 is 80rpm; the diameter of the polishing disc 10 is 300mm; the rotation speed of the polishing disc 10 is 80rpm; the flow rate of the polishing liquid is 15ml / min.

[0077] The weight percentages of the components of polishing liquid A are: 50% deionized water, 30% diamond powder with a particle size of 2 μm, 15% iron powder with a particle size of 50 nm, 4.5% copper oxide, and 0.5% polyethylene glycol; the weight of the deionized water is 200 g.

[0078] The weight percentages of the components of the B polishing solution are: 50% deionized water, 10% diamond powder with a particle size of 2 μm, 35% iron powder with a particle size of 50 nm, 4.5% copper oxide, and 0.5% polyethylene glycol; the weight of the deionized water is 200 g.

[0079] Polishing liquid C is the Fenton polishing liquid of the prior art, and the weight percentage of each component is: deionized water is 50%, hydrogen peroxide is 35%, ferrous sulfate is 13%, and polyethylene glycol is 2%; the weight of deionized water is 200g. Specifically, hydrogen peroxide (H2O2) and iron ions (Fe 2+ ) interact with each other to generate highly active hydroxyl radicals (·OH); these free radicals have strong oxidizing ability and can effectively oxidize organic matter or change the chemical properties of the material surface. Fenton polishing fluid uses this reaction mechanism to achieve surface polishing of materials.

[0080] Table 1

[0081]

[0082] Specifically, it can be seen from the comparison in Table 1 that the polishing liquids A and B containing iron powder have better grinding and polishing effects on diamonds than the polishing liquid C without iron powder, and can achieve precision machining.

[0083] In addition, although the compositions of polishing liquid A and polishing liquid B are the same, the weight percentage of iron powder in polishing liquid A is lower than the weight percentage of iron powder in polishing liquid B, that is, polishing liquid A is a polishing liquid dominated by mechanical polishing, and polishing liquid B is a polishing liquid dominated by iron-carbon affinity chemical reaction.

[0084] From the comparison in Table 1, it can be seen that the surface roughness of the diamond polished with the B polishing liquid is smaller, that is, the effect of the B polishing liquid on the diamond grinding and polishing is higher than that of the A polishing liquid; then it can be concluded that by adjusting the ratio between the diamond powder and the iron powder in the polishing liquid, the dominant position of mechanical polishing and chemical polishing in polishing can be controlled. When the proportion of iron powder is higher than that of diamond powder, chemical polishing dominates the polishing and can achieve a better polishing effect.

[0085] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A diamond polishing liquid, characterized in that: The polishing liquid is prepared by mixing deionized water, diamond micropowder, iron powder, catalyst and dispersant and stirring them uniformly; the weight percentage of each component is: 50%-68% of the deionized water, 10%-40% of the diamond micropowder, 10%-35% of the iron powder, 2%-5% of the catalyst, and 0.1%-0.5% of the dispersant.

2. The diamond polishing liquid according to claim 1, characterized in that: The purity of the iron powder is 90% or above.

3. The diamond polishing liquid according to claim 1, characterized in that: The particle size of the iron powder is in the range of 40 to 150 nm.

4. The diamond polishing liquid according to claim 1, characterized in that: The particle size of the diamond powder is in the range of 1 to 2 μm.

5. The diamond polishing liquid according to claim 1, characterized in that: The catalyst comprises one or more of copper oxide, chromium oxide, titanium dioxide and cerium oxide; and / or, The dispersant includes one or more of sodium lauryl sulfate, polyacrylic acid and polyethylene glycol.

6. A diamond chemical mechanical polishing method, using the diamond polishing liquid according to any one of claims 1 to 5; characterized in that: The steps are as follows: Prepare the polishing liquid; mix diamond powder, iron powder, deionized water, catalyst and oxidant according to a preset weight ratio to prepare the polishing liquid; Diamond is polished using chemical mechanical polishing equipment; the chemical mechanical polishing equipment comprises a polishing disc and a stage; Placing a diamond on the stage and in contact with the polishing disc, and driving the stage and the polishing disc to rotate; The polishing liquid is dripped onto the surface of the polishing disc.

7. The diamond chemical mechanical polishing method according to claim 6, characterized in that: The step of fixing the diamond on the stage and contacting the diamond with the polishing disk, and driving the stage and the polishing disk to rotate comprises: A cast iron disc is used as the polishing disc.

8. The diamond chemical mechanical polishing method according to claim 6, characterized in that: The step of mixing diamond powder, iron powder, deionized water, a catalyst and an oxidant in a preset weight ratio to prepare the polishing liquid includes: Diamond powder, iron powder, deionized water, a catalyst and an oxidant are mixed in a preset weight ratio and magnetically stirred.

9. The diamond chemical mechanical polishing method according to claim 6 or 8, characterized in that: The step of mixing diamond powder, iron powder, deionized water, a catalyst and an oxidant in a preset weight ratio to prepare the polishing liquid includes: Diamond micro powder, iron powder, deionized water, catalyst and oxidant are mixed in a preset weight ratio and then subjected to ultrasonic vibration.

10. The diamond chemical mechanical polishing method according to claim 6, characterized in that: The flow rate range of the polishing liquid is configured to be 10-20 ml / min; and / or, The rotation speed range of the stage is: 50-80r / min; and / or, The rotation speed of the polishing disc ranges from 60 to 80 r / min.

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