Diamond polishing solution, preparation method thereof and chemical mechanical polishing method

Abstract

The invention discloses a diamond polishing solution and a preparation method and a chemical mechanical polishing method thereof, and the diamond polishing solution comprises the following components by total mass of 100%: 1-10% of polyvinyl alcohol, 1-5% of natamycin, 0.5-3% of organic amine ester, 0.5-3% of diamond micro powder, and the balance of pure water. The diamond polishing solution provided by the invention has relatively good compatibility, and through multi-space structure obstruction and crystal electrostatic repulsion, the phenomena of temperature change and grinding agglomeration in the grinding process are remarkably reduced, the problem of longitudinal lines on the surface of a wafer is solved, the grinding repeatability and the one-time yield are guaranteed, and the production efficiency is improved. And the application requirements of the polishing process of the ultra-thin silicon carbide and monocrystalline silicon wafer with the thickness of 150-250 microns can be fully met.

Description

Technical Field

[0001] This invention belongs to the field of polishing technology, specifically relating to a diamond polishing fluid and its preparation method, as well as a chemical mechanical polishing method. Background Technology

[0002] Diamond polishing slurry is a type of fine chemical product widely used in the polishing and fine grinding of material surfaces, especially suitable for applications with extremely high surface precision requirements such as precision grinding and polishing and high-quality wafer surface treatment. Its conventional preparation process is as follows: diamond particles are dispersed in a solvent, mixed and stirred, and then emulsifiers and various additives are added to finally form a diamond suspension polishing slurry. Due to the excellent hardness and grinding performance of diamond particles, this type of polishing slurry has unique advantages in improving the surface finish of materials, and therefore is widely used in the field of precision manufacturing.

[0003] However, existing diamond polishing slurries and their preparation and application technologies still have many shortcomings that urgently need to be addressed: First, diamond micro / nano powders are prone to agglomeration during preparation and use, resulting in poor dispersion. They also commonly exhibit solid-liquid separation, severely affecting the uniformity and stability of the polishing slurry, leading to fluctuations in polishing performance and an inability to guarantee consistent surface quality. Second, existing preparation processes often employ a two-step combined method, which is time-consuming and involves complex steps, increasing operational difficulty, production efficiency, and significantly raising operating costs. Third, when applied to polishing precision components such as wafers, it easily generates scratches and other processing defects on the wafer surface, drastically reducing wafer yield and limiting its further application in high-end precision machining.

[0004] Therefore, there is a need for a diamond polishing slurry that can avoid the dispersion of diamond powder and, in practical applications, avoid problems such as longitudinal lines on the wafer surface. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a diamond polishing fluid and its preparation method, as well as a chemical mechanical polishing method.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a diamond polishing slurry, wherein the diamond polishing slurry comprises, by weight 100%, 1-10% polyvinyl alcohol, 1-5% natamycin, 0.5-3% organic amine ester and 0.5-3% diamond micro powder, with the balance being pure water.

[0008] The polishing slurry provided by this invention constructs a "honeycomb skeleton" by introducing polyvinyl alcohol and a "honeycomb cell shell" by introducing natamycin. Each diamond is located in an independent honeycomb cell, thus providing excellent coating for the monodisperse diamond ("single diamond") and avoiding problems such as diamond agglomeration and precipitation. In other words, the diamond micropowder in the diamond polishing slurry provided by this invention has excellent dispersion effect, with no agglomeration, no stratification, and no sedimentation.

[0009] Meanwhile, in the diamond polishing slurry, the diamond micro powder is in a "dormant" state. When the workpiece is to be polished, the machine applies pressure to awaken the diamond in the polishing slurry and "transfer" it from inside the honeycomb cavity to the surface of the polishing disc for precision grinding and polishing of the workpiece.

[0010] Furthermore, the diamond polishing slurry provided by this invention has good compatibility. Through multiple spatial structure barriers and crystal electrostatic repulsion, it significantly reduces temperature changes and grinding agglomeration during the grinding process, solves the problem of longitudinal lines on the wafer surface, ensures grinding repeatability and first-pass yield, and can fully meet the application requirements of polishing processes for ultra-thin 150-250 μm silicon carbide and single crystal silicon wafers. At the same time, in precision grinding and polishing of third-generation and fourth-generation semiconductor chip substrates and epitaxial applications, it can improve product yield. The polished products have better surface planarization, and the surface finish Ra can reach 0.4-0.6 nm.

[0011] In this invention, the polyvinyl alcohol 1-10% can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.; the natamycin 1-5% can be 1%, 2%, 3%, 4%, 5%, etc.; the organic amine ester 0.5-3% can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.; and the diamond micron powder 0.5-3% can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0012] Preferably, the diamond micropowder has a particle size D50 of 2.5-3.0 μm, such as 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, etc., and more preferably 2.8-2.9 μm.

[0013] The test method for the particle size D50 of the diamond micro powder described in this invention is as follows: wet analysis is performed using a Panaloko Malvern 3000 ultra-high-speed laser particle size analyzer from the UK.

[0014] In actual use, the present invention also includes a trace amount of sodium hydroxide. The purpose of the sodium hydroxide is to dissolve natamycin. The present invention does not impose too many restrictions on the amount of sodium hydroxide used. Any amount that meets the preparation requirements can be used in the present invention.

[0015] In a second aspect, the present invention provides a method for preparing the diamond polishing fluid as described in the first aspect, the method comprising:

[0016] (1) Mix polyvinyl alcohol with pure water to obtain a polyvinyl alcohol solution;

[0017] (2) Mix natamycin with polyvinyl alcohol solution to obtain a base solution;

[0018] (3) Diamond micro powder is added to a base solution and mixed, and then an organic amine ester is added and mixed to obtain the diamond polishing solution.

[0019] Preferably, the polyvinyl alcohol is added to pure water in batches, and more preferably in three batches.

[0020] Preferably, the natamycin is added to the polyvinyl alcohol solution in batches, preferably in two separate additions.

[0021] Preferably, the diamond micro powder is added to the base solution within 30-35 minutes, preferably ultrasonically dispersed after addition, and even more preferably, multiple ultrasonic dispersions are performed.

[0022] Preferably, the organic amine ester is added completely within 50-60 minutes, and more preferably, ultrasonic dispersion is performed after the addition of the organic amine ester, and even more preferably, multiple ultrasonic dispersions are performed.

[0023] As a preferred embodiment of the present invention, the preparation method includes:

[0024] (1) Prepare a polyvinyl alcohol solution and construct a honeycomb skeleton:

[0025] Mix a portion of pure water with the first portion of polyvinyl alcohol at a stirring rate of 220-250 r / min for 10-15 h;

[0026] Then add the second part of polyvinyl alcohol at 250-280 r / min and mix for 5-8 h;

[0027] Finally, at a constant temperature of 8-10℃, the remaining polyvinyl alcohol is added and mixed at 50-60 r / min for 5-6 h to obtain a polyvinyl alcohol solution, which is used as the honeycomb skeleton.

[0028] (2) Constructing the honeycomb cell structure:

[0029] Take the remaining pure water and add sodium hydroxide and natamycin to make the pH value of the solution ≤ 8 and make all the natamycin dissolve to obtain a natamycin solution;

[0030] At a stirring rate of 50-60 r / min, a portion of the natamycin solution was added dropwise to the polyvinyl alcohol solution. The preferred addition time was 30-35 min. After the addition was completed, stirring was continued for 0.5-1 h. At the same time, ultrasonic ionization was performed three times at a frequency of 37 kHz, each time for 10 min.

[0031] Then, the remaining natamycin solution is added dropwise to the polyvinyl alcohol solution, preferably over a period of 30-35 minutes. After the addition is complete, the stirring temperature is kept constant at 16-18°C to obtain the basic solution, which has a cell nucleus spheroid / body structure.

[0032] (3) Coated diamond:

[0033] The prescribed amount of diamond micro powder is slowly added to the base solution, with a feeding time of 30-35 min. After the addition is complete, the mixture is stirred at 500-600 r / min for 0.5-1 h. During the 0.5-1 h period, ultrasonic ionization is performed at 80 kHz, repeated three times for 10 min each time. Then, stirring is continued for 2 h to allow the ultrasonic microjet of diamond micro powder to enter the honeycomb cells / cells, forming a coating and skeletal support for the diamond micro powder. During this process, there is no aggregation, solid-liquid separation, or sedimentation of the diamond micro powder.

[0034] (4) Complete bonding:

[0035] At 500-600 r / min, the organic amine ester of the formula is added dropwise, and the dropwise time is controlled to be 50-60 min. After the dropwise addition is completed, the mixture is stirred for 2 h. During the stirring process, the ultrasonic spectrum of 6-8 kHz is turned on for ultrasonic ionization, and the process is repeated twice, each time for 2 min. Under the low-frequency micro-jet, the free trace amount of diamond powder can be completely introduced into the honeycomb cavity / cluster cell skeleton.

[0036] Then, it is left to stand at a constant temperature of 3-5℃ for 6 hours to allow the diamond polishing slurry with a honeycomb structure to enter a dormant state.

[0037] In step (1) of this invention, the 220-250 r / min can be 220 r / min, 225 r / min, 230 r / min, 235 r / min, 240 r / min, 245 r / min, 250 r / min, etc.; the 10-15 h can be 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, etc.; the 250-280 r / min can be 250 r / min, 255 r / min, 260 r / min, 265 r / min, 270 r / min, 275 r / min, 280 r / min, etc.; the 5-8 h can be 5 h, 6 h, 7 h, 8 h, etc.; the 8-10℃ can be 8℃, 8.5℃, 9℃, 9.5℃, 10℃, etc.; the 50-60 r / min can be 50 r / min, 52 r / min, 55 r / min, 58 r / min, etc. r / min, 60 r / min, etc.; the 5-6 h can be 5 h, 5.2 h, 5.5 h, 5.8 h, 6 h, etc.

[0038] In step (1) of the present invention, the mass ratio between the first part of polyvinyl alcohol, the second part of polyvinyl alcohol and the remaining part of polyvinyl alcohol is (1-2):(1-2):1, for example 1:1:1, 1:1.5:1, 1:2:1, 1.5:1:1, 1.5:1.5:1, 1.5:2:1, 2:1:1, 2:1.5:1, 2:2:1, etc.

[0039] In step (2) of this invention, the pH value ≤ 8 can be 8, 7.9, 7.8, 7.7, 7.6, 7.5, 7.4, 7.3, etc.; the 50-60 r / min can be 50 r / min, 52 r / min, 55 r / min, 58 r / min, 60 r / min, etc.; the 30-35 min can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, etc.; the 0.5-1 h can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, etc.; the 30-35 min can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, etc.; the 16-18℃ can be 16℃, 16.5℃, 17℃, 17.5℃, 18℃, etc.

[0040] In step (2) of the present invention, the remaining pure water accounts for 10-20% of the total mass of pure water, for example, 10%, 12%, 14%, 15%, 16%, 18%, 20%, etc., and the natamycin solution accounts for 50% of the total mass.

[0041] In step (2) of this invention, the amount of sodium hydroxide added is such that the pH value of the remaining pure water is ≤8. This invention does not impose too much limitation on the specific amount of sodium hydroxide used, as long as the pH value of the remaining pure water meets the application requirements.

[0042] Preferably, in step (2), the mass of the remaining pure water is 10-20 times the mass of the natamycin, for example, 10 times, 12 times, 14 times, 15 times, 16 times, 18 times, 20 times, etc.

[0043] In step (3) of the present invention, the 30-35 min can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, etc.; the 500-600 r / min can be 500 r / min, 520 r / min, 550 r / min, 560 r / min, 580 r / min, 600 r / min, etc.; the 0.5-1 h can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, etc.

[0044] In step (4) of the present invention, the 500-600 r / min can be 500 r / min, 520 r / min, 550 r / min, 560 r / min, 580 r / min, 600 r / min, etc.; the 50-60 min can be 50 min, 52 min, 55 min, 56 min, 58 min, 60 min, etc.; the 6-8 kHz can be 6 kHz, 6.5 kHz, 7 kHz, 7.5 kHz, 8 kHz, etc.; and the 3-5℃ can be 3℃, 3.5℃, 4℃, 4.5℃, 5℃, etc.

[0045] The preparation method provided by the present invention constructs a bonded scaffold honeycomb, and then constructs and reshapes several honeycomb cells, precisely coating each diamond microparticle (diamond monodisperse) in the honeycomb cells, so that the resulting diamond polishing fluid has excellent dispersibility, does not agglomerate, does not separate, and does not settle.

[0046] Thirdly, the present invention provides a chemical mechanical polishing method, wherein the chemical mechanical polishing method utilizes the diamond polishing solution described in the first aspect.

[0047] Preferably, the chemical mechanical polishing method includes:

[0048] The workpiece to be polished is placed between the upper and lower polishing discs and polished. During the polishing process, the diamond polishing liquid is dripped onto the surface of the upper polishing disc.

[0049] Preferably, the upper polishing disc is pressed against the lower polishing disc.

[0050] Preferably, the upper and lower polishing discs rotate in opposite directions.

[0051] Preferably, the pressure value of the pressurization is 0.1-0.2 MPa, such as 0.1 MPa, 0.12 MPa, 0.15 MPa, 0.18 MPa, 0.2 MPa, etc.

[0052] In this invention, the diamond polishing slurry has a dual awakening mechanism. First, the diamond in the polishing slurry is awakened by the pressure of 0.1-0.2 MPa applied by the precision grinding and polishing machine, which causes the diamond to transfer from the honeycomb cell / cluster structure and participate in precision polishing. Second, the awakening mechanism is triggered by the movement of the machine, which causes friction and temperature changes, making the diamond polishing slurry form a moving flow surface and participate in wafer grinding and polishing.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] (1) The diamond polishing fluid provided by the present invention can significantly solve the temperature change and grinding agglomeration phenomenon during the grinding process through multiple spatial structure barriers and crystal electrostatic repulsion, solve the problem of longitudinal lines on the wafer surface, and at the same time solve the problem of ensuring grinding repeatability and first-pass yield.

[0055] (2) The diamond polishing fluid provided by the present invention can simultaneously meet the polishing process of ultra-thin 150-250 μm silicon carbide or single crystal silicon wafers. Attached Figure Description

[0056] Figure 1 This is a suspension dispersion microscope image of the sample provided in Example 1 of the present invention;

[0057] Figure 2 A suspension dispersion microscope image of the sample provided in Comparative Example 1 of this invention;

[0058] Figure 3 A diagram showing the suspension and dispersion results of the residual liquid after polishing with the polishing slurry provided in Example 1 of the present invention;

[0059] Figure 4 This is a diagram showing the suspension and dispersion results of the residual liquid after polishing with the polishing liquid provided in Comparative Example 1 of this invention.

[0060] Figure 5 The image shows the polished surface of a silicon carbide wafer after polishing with the diamond polishing fluid provided in Example 1.

[0061] Figure 6 The image shows the polished surface of a silicon carbide wafer after polishing with the diamond polishing slurry provided in Comparative Example 1. Detailed Implementation

[0062] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0063] Unless otherwise specified, the raw materials involved in the following specific embodiments of the present invention are all conventional materials in the art, and can be purchased from commercially available products. Some raw material information is as follows:

[0064] Polyvinyl alcohol: purchased from Jiangshun Industrial, model number 2488;

[0065] Diamond micron powder: particle size D50 is 2.8-2.9 μm, purchased from Nanjing Jinrui Lifeng;

[0066] Organic amine esters: purchased from Cai Jianxiong Industrial Co., Ltd., model number CH-99.

[0067] Example 1

[0068] This embodiment provides a diamond polishing slurry and its preparation method. The diamond polishing slurry comprises: 5% polyvinyl alcohol, 4% natamycin, 0.5% organic amine ester, and 0.5% diamond micro powder, with the balance being pure water.

[0069] The preparation method is as follows:

[0070] (1) Prepare a polyvinyl alcohol solution and construct a honeycomb skeleton:

[0071] Pure water with a total mass of 90 wt% was mixed with 40 wt% polyvinyl alcohol at a stirring rate of 250 r / min for 12 h.

[0072] Then add 40% polyvinyl alcohol at 260 r / min and mix for 8 h;

[0073] Finally, at a constant temperature of 9℃, the remaining polyvinyl alcohol was added and mixed at 55 r / min for 6 h to obtain a polyvinyl alcohol solution, which was used as the honeycomb skeleton.

[0074] (2) Constructing the honeycomb cell structure:

[0075] Add sodium hydroxide and natamycin to 10 wt% pure water to make the pH of the solution 8 and to completely dissolve the natamycin to obtain a natamycin solution.

[0076] At a stirring rate of 55 r / min, 50 wt% natamycin solution was added dropwise to polyvinyl alcohol solution over a time of 35 min. After the addition was completed, stirring was continued for 1 h. At the same time, ultrasonic ionization was performed three times at a frequency of 37 kHz, each time for 10 min.

[0077] Then the remaining natamycin solution was added dropwise to the polyvinyl alcohol solution over a period of 35 minutes. After the addition was complete, the stirring temperature was kept constant at 17°C to obtain the basic solution, which has a nucleus spheroid / body structure.

[0078] (3) Coated diamond:

[0079] The prescribed amount of diamond micro powder was slowly added to the base solution, with a feeding time of 35 min. After the addition was completed, the mixture was stirred at 550 r / min for 1 h. During this 1 h, ultrasonic ionization was performed at 80 kHz, repeated three times for 10 min each time. Then, stirring was continued for 2 h to allow the ultrasonic microjet of diamond micro powder to enter the honeycomb cells / cells, forming a coating and skeletal support for the diamond micro powder. During this process, there was no agglomeration, solid-liquid separation, or sedimentation of the diamond micro powder.

[0080] (4) Complete bonding:

[0081] At 550 r / min, the organic amine ester of the formula was added dropwise, and the dropwise time was controlled to be 55 min. After the dropwise addition was completed, the mixture was stirred for 2 h. During the stirring process, the ultrasonic spectrum of 7 kHz ultrasonic ionization was turned on and repeated twice, each time for 2 min. Under the low frequency micro-jet, the free trace amount of diamond powder could be completely introduced into the honeycomb cavity / cluster cell skeleton.

[0082] Then, it is left to stand at a constant temperature of 4°C for 6 hours to allow the diamond polishing fluid with a honeycomb structure to enter a static dormant state, thus obtaining the diamond polishing fluid.

[0083] Example 2

[0084] This embodiment provides a diamond polishing slurry and its preparation method. The diamond polishing slurry comprises: 1% polyvinyl alcohol, 1% natamycin, 1% organic amine ester, and 1% diamond micro powder, with the balance being pure water, as follows:

[0085] (1) Prepare a polyvinyl alcohol solution and construct a honeycomb skeleton:

[0086] 80 wt% pure water and 30 wt% polyvinyl alcohol were mixed and stirred at a stirring rate of 220 r / min for 10 h.

[0087] Then add 40 wt% polyvinyl alcohol at 250 r / min and mix for 5 h;

[0088] Finally, at a constant temperature of 10℃, the remaining polyvinyl alcohol was added and mixed at 50 r / min for 5 h to obtain a polyvinyl alcohol solution, which was used as the honeycomb skeleton.

[0089] (2) Constructing the honeycomb cell structure:

[0090] Add sodium hydroxide and natamycin to 20 wt% pure water to make the pH of the solution 7.5 and to completely dissolve the natamycin, thus obtaining a natamycin solution;

[0091] At a stirring rate of 50 r / min, 50 wt% natamycin solution was added dropwise to polyvinyl alcohol solution over a period of 30 min. After the addition was completed, stirring was continued for 0.5 h. At the same time, ultrasonic ionization was performed three times at a frequency of 37 kHz, each time for 10 min.

[0092] Then the remaining natamycin solution was added dropwise to the polyvinyl alcohol solution over a period of 30 minutes. After the addition was complete, the stirring temperature was kept constant at 16°C to obtain the basic solution, which has a nucleus spheroid / body structure.

[0093] (3) Coated diamond:

[0094] The prescribed amount of diamond micro powder was slowly added to the base solution, with a feeding time of 32 min. After the addition was completed, the mixture was stirred at 500 r / min for 0.5 h. During the 0.5 h, ultrasonic ionization was performed at 80 kHz, repeated three times for 10 min each time. Then, stirring was continued for 2 h to allow the ultrasonic microjet of diamond micro powder to enter the honeycomb cells / cells, forming a coating and skeletal support for the diamond micro powder. During this process, there was no aggregation, solid-liquid separation, or sedimentation of the diamond micro powder.

[0095] (4) Complete bonding:

[0096] At 500 r / min, the organic amine ester of the formula was added dropwise, and the dropwise time was controlled to be 50 min. After the dropwise addition was completed, the mixture was stirred for 2 h. During the stirring process, the ultrasonic spectrum of 6 kHz was turned on for ultrasonic ionization, and the process was repeated twice, each time for 2 min. Under the low frequency micro-jet, the free trace amount of diamond powder could be completely introduced into the honeycomb cavity / cluster cell skeleton.

[0097] Then, it is left to stand at a constant temperature of 3°C for 6 hours to allow the diamond polishing fluid with a honeycomb structure to enter a static dormant state, thus obtaining the diamond polishing fluid.

[0098] Example 3

[0099] This embodiment provides a diamond polishing slurry and its preparation method. The diamond polishing slurry comprises: 10% polyvinyl alcohol, 5% natamycin, 3% organic amine ester, and 3% diamond micro powder, with the balance being pure water, as follows:

[0100] (1) Prepare a polyvinyl alcohol solution and construct a honeycomb skeleton:

[0101] 90 wt% pure water and 40 wt% polyvinyl alcohol were mixed and stirred at a stirring rate of 240 r / min for 15 h.

[0102] Then add 30 wt% polyvinyl alcohol at 280 r / min and mix for 6 h;

[0103] Finally, at a constant temperature of 8℃, the remaining polyvinyl alcohol was added and mixed at 60 r / min for 5.5 h to obtain a polyvinyl alcohol solution, which was used as the honeycomb skeleton.

[0104] (2) Constructing the honeycomb cell structure:

[0105] Add sodium hydroxide and natamycin to 10 wt% pure water to make the pH of the solution 8 and to completely dissolve the natamycin to obtain a natamycin solution.

[0106] At a stirring rate of 60 r / min, 50 wt% natamycin solution was added dropwise to polyvinyl alcohol solution over a time of 35 min. After the addition was complete, stirring was continued for 0.8 h. At the same time, ultrasonic ionization was performed three times at a frequency of 37 kHz, each time for 10 min.

[0107] Then the remaining natamycin solution was added dropwise to the polyvinyl alcohol solution over a period of 32 minutes. After the addition was complete, the stirring temperature was kept constant at 18°C ​​to obtain the basic solution, which has a cell nucleus spheroid / body structure.

[0108] (3) Coated diamond:

[0109] The prescribed amount of diamond micro powder was slowly added to the base solution, with a feeding time of 30 min. After the addition was completed, the mixture was stirred at 600 r / min for 0.8 h. During the 0.8 h, ultrasonic ionization was performed at 80 kHz, repeated three times for 10 min each time. Then, stirring was continued for 2 h to allow the ultrasonic microjet of diamond micro powder to enter the honeycomb cells / cells, forming a coating and skeletal support for the diamond micro powder. During this process, there was no aggregation, solid-liquid separation, or sedimentation of the diamond micro powder.

[0110] (4) Complete bonding:

[0111] At 600 r / min, the organic amine ester of the formula was added dropwise, and the dropwise time was controlled to be 60 min. After the dropwise addition was completed, the mixture was stirred for 2 h. During the stirring process, the ultrasonic spectrum of 8 kHz ultrasonic ionization was turned on and repeated twice, each time for 2 min. Under the low frequency micro-jet, the free trace amount of diamond powder could be completely introduced into the honeycomb cavity / cluster cell skeleton.

[0112] Then, it is left to stand at a constant temperature of 5°C for 6 hours to allow the diamond polishing slurry with a honeycomb structure to enter a static dormant state, thus obtaining the diamond polishing slurry.

[0113] Comparative Example 1

[0114] This comparative example provides a commercially available diamond polishing slurry, Pureon polishing slurry (3 μm), purchased from DiamondSlurry (OPW-FG-3 micron).

[0115] Application examples

[0116] This application example provides a chemical mechanical polishing method using the diamond polishing slurry provided in Example 1, including:

[0117] The workpiece to be polished is placed between the upper and lower polishing discs and polished. During the polishing process, the diamond polishing liquid is dripped onto the surface of the upper polishing disc.

[0118] The upper polishing disc is pressurized at 0.2 MPa to fit against the lower polishing disc, and the upper and lower polishing discs rotate in opposite directions.

[0119] Performance testing

[0120] The performance of the samples provided in the examples and comparative examples was tested using the following methods:

[0121] (1) Dispersibility: The dispersibility of diamonds in the diamond polishing slurry was observed using a Zeiss 10,000x focal length microscope. The results are as follows:

[0122] Figure 1-2 The figures show the suspension dispersion results of the samples provided in Example 1 and Comparative Example 1 of the present invention, respectively, with a magnification of 1000 times. As can be seen from the figure comparison, the diamond in the diamond polishing solution provided by the present invention is dispersed as 3 μm single particles, while the polishing solution provided in Comparative Example 1 contains agglomerates.

[0123] (2) Referring to the application example, a silicon carbide wafer with a thickness of 380 μm was polished using a double-sided grinding and polishing machine with polishing parameters of Ra=0.8 nm. After polishing, the dispersion of diamond in the residual liquid was observed using a Zeiss 10000x focal length microscope. The results are as follows:

[0124] Figure 3-4 The figures show the suspension and dispersion results of the residual liquid after polishing with the polishing slurry provided in Example 1 and Comparative Example 1 of the present invention, respectively. The magnification is 1000 times. As can be seen from the figures, the diamond polishing slurry provided by the present invention still has excellent dispersion uniformity after use.

[0125] Meanwhile, the diamond polishing slurry provided by this invention can be directly applied to the machine for use, while the polishing slurry provided in Comparative Example 1 requires mechanical mixing before it can be used, which is more expensive.

[0126] (3) Referring to the application example, a silicon carbide wafer with a thickness of 380 μm was polished using a double-sided grinding and polishing machine with polishing parameters of Ra=0.8 nm. After polishing, the polished surface was observed to be free of defects such as longitudinal striations or scratches using a 3D white light interferometer. The results are as follows:

[0127] Figure 5-6 The figures show the polished surfaces of silicon carbide wafers after polishing with the diamond polishing slurry provided in Example 1 and Comparative Example 1, respectively. As can be seen from the figures, when polished with the diamond polishing slurry provided by the present invention, the wafer surface only has normal processing trajectory movement marks; while when polished with the polishing slurry provided in Comparative Example 1, the wafer surface has through marks, and under professional strong light observation, fine deep scratches can be seen.

[0128] (4) Surface finish Ra: The surface finish of the polished silicon carbide wafer was measured using a 3D white light interferometry analyzer. The results are as follows:

[0129] The polishing slurry provided in the embodiments of the present invention enables the wafer to have better surface planarization. Specifically, after polishing with the diamond polishing slurry provided in Example 1, the Ra of the silicon carbide wafer is 0.54 nm, in Example 2 it is 0.50 nm, and in Example 3 it is 0.42 nm. That is, the polishing slurry of the present invention can achieve better surface planarization of the wafer, and the surface finish Ra can reach 0.4-0.6 nm.

[0130] As can be seen from the examples and performance tests, the diamond in the diamond polishing fluid provided by the present invention is in a single-particle dispersion state, which has excellent dispersibility, does not agglomerate, does not separate, and does not precipitate. At the same time, using it for polishing can significantly reduce temperature changes and grinding agglomeration during the grinding process, solve the problem of longitudinal lines on the wafer surface, ensure grinding repeatability and first-pass yield, and the surface finish Ra of the polished wafer can reach 0.4-0.6 nm.

[0131] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A diamond polishing fluid, characterized in that, Based on the total mass of the diamond polishing slurry as 100%, the diamond polishing slurry comprises: 1-10% polyvinyl alcohol, 1-5% natamycin, 0.5-3% organic amine ester and 0.5-3% diamond micro powder, with the balance being pure water.

2. The diamond polishing slurry according to claim 1, characterized in that, The diamond micropowder has a particle size D50 of 2.5-3.0 μm, preferably 2.8-2.9 μm.

3. A method for preparing the diamond polishing fluid as described in claim 1 or 2, characterized in that, The preparation method includes: (1) Mix polyvinyl alcohol with pure water to obtain a polyvinyl alcohol solution; (2) Mix natamycin with polyvinyl alcohol solution to obtain a base solution; (3) Diamond micro powder is added to a base solution and mixed, and then an organic amine ester is added and mixed to obtain the diamond polishing solution.

4. The preparation method according to claim 3, characterized in that, The polyvinyl alcohol is added to pure water in batches, preferably in three batches; And / or, the natamycin is added to the polyvinyl alcohol solution in batches, preferably in two separate additions.

5. The preparation method according to claim 3 or 4, characterized in that, The diamond micro powder is added to the base solution within 30-35 minutes. Preferably, ultrasonic dispersion is performed after the addition is complete, and more preferably, multiple ultrasonic dispersions are performed.

6. The preparation method according to any one of claims 3-5, characterized in that, The organic amine ester is added completely within 50-60 minutes, preferably ultrasonically dispersed after the addition of the organic amine ester, and more preferably multiple ultrasonic dispersions are performed.

7. A chemical mechanical polishing method, characterized in that, The chemical mechanical polishing method is performed using the diamond polishing fluid described in claim 1 or 2.

8. The chemical mechanical polishing method according to claim 7, characterized in that, The chemical mechanical polishing method includes: The workpiece to be polished is placed between the lower and upper plates using a planetary wheel for polishing. During the polishing process, the diamond polishing liquid is dripped onto the surface of the upper polishing plate.

9. The chemical mechanical polishing method according to claim 8, characterized in that, The upper polishing disc is pressed and adhered to the lower polishing disc; And / or, the upper and lower polishing discs rotate in opposite directions.

10. The chemical mechanical polishing method according to claim 9, characterized in that, The pressurization pressure is 0.1-0.2 MPa.

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