A micron-level flatness retaining ring and its processing method and application

Abstract

The application provides a micron-level flatness retaining ring and a processing method and application thereof. The processing method adopts a grinding processing mode to process a grinding head butt joint reference surface of a metal ring of the retaining ring, and comprises the following steps: fixing the retaining ring on a workbench of a grinding machine, so that the grinding head butt joint reference surface of the metal ring faces a processing assembly; and grinding the grinding head butt joint reference surface by using a grinding wheel. After the grinding processing is completed, the retaining ring with the micron-level flatness butt joint reference surface is obtained. The flatness of the grinding head butt joint reference surface is 1-8 microns. The abrasive of the grinding wheel is selected from one or more of cubic boron nitride particles and diamond particles. The grinding head butt joint reference surface flatness of the retaining ring provided by the technical solution reaches the micron level. In the subsequent chemical mechanical polishing process, the wafer surface flatness can be ensured as much as possible, and the product yield is high.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and in particular to a retaining ring with micron-level flatness, its processing method, and its application. Background Technology

[0002] Chemical mechanical polishing (CMP) is a crucial process in semiconductor manufacturing for achieving global planarization of the wafer surface. The retaining ring, a key component of the CMP equipment's polishing head, is typically positioned around the wafer to constrain its position and, in conjunction with the polishing head, apply stable pressure to the wafer and polishing pad.

[0003] A retaining ring typically consists of a metal ring and a plastic ring connected to the metal ring. The side of the metal ring closest to the grinding head forms a mating reference surface for assembly with the grinding head. The flatness of this mating reference surface directly affects the fit and assembly accuracy between the retaining ring and the grinding head. When the mating reference surface has warping, localized protrusions, depressions, or thickness deviations, the retaining ring is prone to tilting, localized suspension, or uneven stress after installation. This further leads to uneven pressure distribution transmitted from the grinding head to the retaining ring and the wafer periphery. Uneven pressure distribution affects the material removal rate in different areas of the wafer, particularly causing over-grinding or under-grinding of the wafer edges, thus impacting the overall flatness, film thickness uniformity, and processing yield of the wafer. Therefore, the flatness of the mating reference surface of the retaining ring is a crucial indicator affecting CMP process stability and wafer processing quality.

[0004] As the feature size and linewidth of semiconductor devices continue to shrink, the requirements for controlling wafer surface flatness and film thickness uniformity are constantly increasing. Correspondingly, the flatness requirements for the mating reference surface of the polishing head for retaining rings are gradually increasing to the micrometer level. However, the flatness of the mating reference surface of existing retaining ring polishing heads is typically 1–3 microns (10–30 micrometers), and the flatness fluctuations between different products or processing batches are quite significant, making it difficult to consistently meet the requirements of high-precision CMP processes for retaining ring assembly accuracy and pressure uniformity. This is because the processing of the mating reference surface of existing retaining ring polishing heads usually relies on polishing pads and polishing slurries, and its processing effect is easily affected by factors such as the wear degree of the polishing pad and changes in the concentration of the polishing slurry. As the processing continues, the surface condition of the polishing pad and the properties of the polishing slurry change, easily causing inconsistent material removal in different areas of the mating reference surface of the polishing head, resulting in poor flatness stability and insufficient batch consistency. To ensure that the product meets the requirements, it is usually necessary to frequently perform flatness checks during processing and repeatedly adjust processing parameters based on the check results. This not only increases processing and inspection costs but also hinders the standardization, continuity, and automation of the processing flow.

[0005] Therefore, how to provide a processing method that can not only improve the flatness of the grinding head mating reference surface of the retaining ring, but also reduce the flatness fluctuation between different products and different batches, with stable and simple process, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a micron-level flatness retaining ring, its processing method and application, to solve the problems in the prior art.

[0007] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0008] The first aspect of this invention provides a method for processing a retaining ring with micron-level flatness, which involves grinding the metal ring of the retaining ring to a reference surface of a grinding head, including the following steps:

[0009] A retaining ring is fixed to the worktable of the grinding machine, with the grinding head mating reference surface of the metal ring facing the processing assembly. A grinding wheel is used to grind the grinding head mating reference surface. After grinding, a retaining ring with a grinding head mating reference surface having a flatness of 1 to 8 micrometers is obtained. The abrasive of the grinding wheel is selected from one or more of cubic boron nitride particles and diamond particles. For example, the flatness can be 1 micrometer, 2 micrometers, 3 micrometers, 4 micrometers, 5 micrometers, 6 micrometers, 7 micrometers, or 8 micrometers.

[0010] Preferably, the surface roughness (Ra) of the grinding head mating reference surface is 0.1 to 0.6 micrometers. For example, it can be 0.1 micrometers, 0.2 micrometers, 0.3 micrometers, 0.4 micrometers, 0.5 micrometers, or 0.6 micrometers.

[0011] Preferably, the abrasive of the grinding wheel is a composite abrasive of cubic boron nitride particles and diamond particles.

[0012] The choice of grinding wheel also affects the final quality of the mating reference surface of the grinding head. The two superhard abrasives in a composite grinding wheel complement each other in terms of mechanical and thermal properties, resulting in a more balanced wear behavior compared to a single-abrasive wheel. Diamond has higher hardness and a sharper cutting edge, allowing for a quicker cut when undertaking the main cutting task; CBN has relatively good toughness and strong resistance to thermal shock, playing a supporting and auxiliary cutting role in the grinding zone. Using a composite abrasive reduces the difference in cutting ability between different locations on the grinding wheel surface, and the material removal rate across different areas of the workpiece end face becomes more consistent. This reduces shape errors caused by local overcutting or undercutting, resulting in a higher flatness of the mating reference surface of the grinding head.

[0013] Preferably, the fixing method is selected from one or more of clamp fixing and adhesive fixing. More preferably, clamp fixing is used, specifically vacuum adsorption clamp fixing. Specifically, the vacuum gauge pressure of the vacuum adsorption clamp during use is -0.1 to -0.01 MPa, such as -0.1 to -0.05 MPa or -0.09 to -0.07 MPa.

[0014] The method of retaining the ring affects the stability of the machining results. This application employs a vacuum adsorption fixture, which meets the stringent requirements for clamping deformation in micron-level flatness machining. Simultaneously, the repeatability of vacuum adsorption can be stably controlled within two micrometers, contributing to the stability of production results across different batches. Furthermore, the clamping force of vacuum adsorption is uniformly distributed along the ring's end face, making the retaining ring less prone to displacement or micro-vibration under grinding forces, which is highly suitable for machining the high-precision retaining ring grinding head mating reference surface.

[0015] Preferably, the grinding machine is a rotary table grinding machine, and the worktable is a rotary worktable with a rotational speed of 100-180 rpm. For example, the rotational speed can be 120-180 rpm, 130-170 rpm, or 140-160 rpm. More preferably, the rotary table grinding machine grinds the workpiece using the circumference of the grinding wheel.

[0016] The grinding wheel used in this application grinds the workpiece around its circumference. Compared with grinding using the end face of the grinding wheel, circumferential grinding only utilizes a local segment of the outer circumference of the grinding wheel for cutting. The linear velocity at each point on the circumference of the grinding wheel is consistent, and the wear spreads evenly along the tangential direction, resulting in better processing stability, longer dressing intervals, and higher process reproducibility. At the same time, the surface texture formed by the machined retaining ring is fine, and the surface roughness and flatness are lower, which is beneficial for achieving high-precision end face quality.

[0017] Preferably, the content of cubic boron nitride abrasive particles is 40–80 wt% based on the total mass of the abrasive particles. For example, it can be 45–70 wt%, or 40–60 wt%.

[0018] Preferably, the content of diamond abrasive particles is 20-60 wt% based on the total mass of the abrasive particles. For example, it can be 30-60 wt% or 40-60 wt%.

[0019] More specifically, in grinding wheels, ceramics or resins are used as binders to bond cubic boron nitride particles and diamond particles.

[0020] Preferably, the abrasive particles in the grinding wheel have a particle size of 150-300 mesh. In this application, the particle size of the abrasive particles refers to the average particle size of the composite abrasive, such as 150-250 mesh or 180-220 mesh.

[0021] Preferably, the hardness grade of the grinding wheel is K.

[0022] Preferably, the abrasive concentration of the grinding wheel is 75-125%. For example, it can be 75% or 125%.

[0023] Preferably, the parameters of the grinding process include one or more of the following technical features:

[0024] The spindle speed is 800–2000 rpm;

[0025] The depth of a single grinding pass is 1 to 50 micrometers;

[0026] The total grinding time is 7–12 minutes;

[0027] During the grinding process, grinding fluid is continuously supplied to the contact grinding area between the grinding wheel and the metal ring for cooling.

[0028] In this application, the concentration of the supplied grinding fluid is 2-15 wt%. For example, it can be 5-15 wt% or 7-10 wt%.

[0029] The spindle speed can be 1200~2000rpm, 1500~2000rpm, or 1700~1900rpm; the single grinding depth can be 1~30 micrometers, 1~20 micrometers, or 1~10 micrometers; and the total grinding time can be 8~12min, 8~10min, or 8~9min.

[0030] Preferably, the grinding process includes rough grinding and fine grinding performed sequentially.

[0031] Preferably, the parameters of the coarse grinding process include one or more of the following technical features:

[0032] The removal margin is 50–120 micrometers;

[0033] The time is 5 to 7 minutes;

[0034] The depth of a single grinding pass is 1 to 50 micrometers.

[0035] During the rough grinding process, the amount of material removed can be 50-100 micrometers, 50-90 micrometers, or 60-80 micrometers; the time can be 5 minutes, 6 minutes, or 7 minutes; and the depth of grinding per pass can be 1-30 micrometers, 1-20 micrometers, or 2-10 micrometers.

[0036] Preferably, the parameters of the fine grinding process include one or more of the following technical features:

[0037] The amount of material removed is 1–15 micrometers;

[0038] The time is 2 to 4 minutes;

[0039] The depth of a single grinding pass is 0.5 to 30 micrometers.

[0040] During the fine grinding process, the amount of material removed can be 1~13 micrometers, 3~10 micrometers, or 5~10 micrometers; the time can be 2 minutes, 3 minutes, or 4 minutes; and the depth of grinding per pass can be 0.5~20 micrometers, 0.5~10 micrometers, or 0.5~5 micrometers.

[0041] In the grinding process of this application, a multi-stage grinding method combining rough grinding and fine grinding is adopted. In the rough grinding stage, a large cutting amount is used to quickly remove the main body material, so that the retaining ring quickly approaches the target size, thereby improving production efficiency. In the fine grinding stage, a very small depth of cut and stable process parameters are used to finely correct shape errors and reduce surface roughness and flatness. While ensuring micron-level flatness, the overall processing time is controlled, thereby improving production efficiency.

[0042] A second aspect of the present invention provides a retaining ring with micron-level flatness, obtained by processing using the method described above; the retaining ring includes a metal ring and a plastic ring fixedly connected to one side of the metal ring, and the flatness of the grinding head of the metal ring mating with the reference surface is 1 to 8 microns. For example, it can be 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, or 8 microns.

[0043] Preferably, the metal includes one or more of iron and stainless steel.

[0044] Preferably, the plastic is selected from one or more of polyphenylene sulfide and polyetheretherketone.

[0045] Preferably, the surface roughness (Ra) of the grinding head mating reference surface is 0.1 to 0.6 micrometers. For example, it can be 0.1 micrometers, 0.2 micrometers, 0.3 micrometers, 0.4 micrometers, 0.5 micrometers, or 0.6 micrometers.

[0046] This application does not specify the method of fixing the metal ring and the plastic ring, such as bonding with glue.

[0047] A third aspect of the present invention provides an application of a retaining ring obtained by the processing method described above, or a retaining ring as described above, in a chemical mechanical polishing process, the application including one or more of the following:

[0048] Used to improve the overall flatness of wafers;

[0049] Used to improve the uniformity of film wafer thickness;

[0050] Used to improve the processing yield of products.

[0051] Beneficial effects:

[0052] This application's technical solution abandons the commonly used flexible polishing process in the prior art—that is, polishing the mating reference surface of the grinding head of the retaining ring with a flat polishing machine—and creatively adopts a "rigid grinding" processing method to process the mating reference surface of the grinding head of the retaining ring. This method fundamentally avoids the problem of flatness fluctuation caused by polishing pad wear or unstable polishing fluid properties, ensuring the processing stability of different batches and resulting in good product consistency.

[0053] Simultaneously, this processing method, combined with specific process paths and parameters, enables the flatness of the grinding head of the retaining ring to align with the reference surface at the micrometer level, ranging from 1 to 8 micrometers, meeting the requirements of high-precision CMP processes. During subsequent chemical mechanical polishing, it ensures the wafer surface remains as flat as possible, preventing edge collapse and resulting in high product yield.

[0054] Furthermore, the processing method provided by this application has a short processing time and high efficiency, and can achieve stable batch production with high efficiency and low fluctuation while ensuring high processing accuracy, effectively balancing the quality of the ring and manufacturing cost. Attached Figure Description

[0055] Figure 1 The diagram shown is a schematic representation of the method for fixing the retaining ring metal ring in Comparative Example 5 of the present invention. Detailed Implementation

[0056] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0057] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0058] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0059] In the existing technology, a "flexible polishing process" is often used to process the grinding head mating reference surface of the retaining ring. However, the processing effect is affected by factors such as the wear degree of the polishing pad and the change of polishing fluid concentration, resulting in poor flatness stability and insufficient batch consistency of the grinding head mating reference surface. Moreover, this process cannot obtain a grinding head mating reference surface of the retaining ring with lower flatness.

[0060] This application's technical solution is a concrete address to this deficiency. The processing method of this application creatively transcends the category of "flexible polishing process," abandoning commonly used methods in existing technologies and providing a "rigid grinding" processing method, thereby fundamentally solving the problems caused by the polishing process. This application's processing method, by selecting a specific fixing method, combining grinding wheel-related characteristics with optimized grinding parameters, provides a grinding head with a retaining ring that has extremely low flatness, aligning with a reference surface for subsequent applications.

[0061] The grinding machine used in the following embodiments of this application is a horizontal spindle rotary table surface grinder (model MGK735015), and the grinding wheel used is a CBN-doped diamond composite grinding wheel, with grinding performed circumferentially. Based on the total mass of the abrasive particles, the diamond content is 50 wt%, the CBN content is 50 wt%, and they are bonded together using a ceramic binder. The abrasive particle size in the grinding wheel is 200 mesh, and the grinding wheel concentration is 75%.

[0062] The grinding fluid used is from the brand Tairent, which is a microemulsion extreme pressure grinding fluid, model CCF-10G, specification: 200KG.

[0063] In this application, the metal ring of the retaining ring to be processed is made of stainless steel, and the plastic ring is made of polyphenylene sulfide (PPS).

[0064] Example 1

[0065] This embodiment provides a specific micron-level flatness retaining ring and its processing method, which specifically includes the following steps:

[0066] Install the existing vacuum adsorption fixture onto the worktable of the grinding machine. The repeatability of this fixture should not exceed 2 micrometers. Clean the retaining ring to be processed using a lint-free cloth dampened with analytical grade isopropanol to remove oil and impurities from its lower end face, ensuring a tight fit between the retaining ring and the fixture's adsorption reference surface. Place the retaining ring stably in the center of the adsorption area of ​​the vacuum adsorption fixture, ensuring its lower end face naturally aligns with the fixture's adsorption reference surface. Start the vacuum pump to create negative pressure inside the fixture, uniformly adsorbing and fixing the retaining ring. After clamping, check for any tilting or misalignment of the retaining ring, confirming that the vacuum level is stable at approximately -0.08 MPa.

[0067] Then, a compound grinding wheel is used for grinding. The specific grinding process is as follows: first, rough grinding is performed for 6 minutes, removing 70 micrometers of material, with a spindle speed of 1800 rpm, a table speed of 150 rpm, and a single grinding depth of 6 micrometers; then, fine grinding is performed for 3 minutes, removing 8 micrometers of material, with a spindle speed of 1200 rpm, a table speed of 150 rpm, and a single grinding depth of 1 micrometer.

[0068] During the grinding process, grinding fluid with a concentration of 8 wt% is continuously supplied to the contact grinding zone between the grinding wheel and the retaining ring for cooling.

[0069] Example 2

[0070] This embodiment provides a specific micron-level flatness retaining ring and its processing method, which specifically includes the following steps:

[0071] The fixture holding the retaining ring to be processed is clamped and fixed on the worktable of the grinding machine (the repeatability of the fixture is ≤2 micrometers). Grinding is performed using a compound grinding wheel. The specific grinding process is as follows: rough grinding is performed first, with a time of 5 minutes, removing 70 micrometers of material, a spindle speed of 1800 rpm, a worktable speed of 150 rpm, and a single grinding depth of 8 micrometers; then fine grinding is performed, with a time of 3 minutes, removing 8 micrometers of material, a spindle speed of 1200 rpm, a worktable speed of 150 rpm, and a single grinding depth of 2 micrometers.

[0072] During the grinding process, grinding fluid with a concentration of 8 wt% is continuously supplied to the contact grinding zone between the grinding wheel and the retaining ring for cooling.

[0073] Comparative Example 1

[0074] Except that the grinding wheel used is a pure CBN grinding wheel, the other steps are the same as in Example 1.

[0075] Comparative Example 2

[0076] Except that the rotary table grinder used is a vertical spindle rotary table surface grinder (purchased from Chaoyang Machine Tool Factory, which grinds workpieces by the end face of the grinding wheel), the other steps are the same as in Example 1.

[0077] Comparative Example 3

[0078] Except that coolant is not used during the grinding process, the other conditions are the same as in Example 1.

[0079] Comparative Example 4

[0080] Except for the continuous use of rough grinding parameters during the grinding process, without fine grinding, specifically: the time is 9 minutes, the amount removed is 70 micrometers, the spindle speed is 1800 rpm, the table speed is 150 rpm, and the single grinding depth is 6 micrometers; other conditions are the same as in Example 1.

[0081] Comparative Example 5

[0082] Except for the method of using a stop block to limit the fixing of the retaining ring instead of a vacuum adsorption clamp, all other conditions are the same as in Example 1.

[0083] Specifically: such as Figure 1 As shown, the metal ring is placed directly on the rotary worktable, and the stop (block-shaped component) fixed on the surface of the worktable is used to limit the contact from the circumference of the retaining ring. That is, the stop is evenly distributed along the circumference of the worktable and fits against the outer circular surface of the retaining ring to achieve radial positioning, while the lower end face of the workpiece naturally fits against the plane of the worktable for axial positioning.

[0084] Example of effect

[0085] The applicant conducted performance tests on the flatness and roughness (Ra) of the mating reference surface of the grinding head of the retaining rings provided in each embodiment and comparative example. The specific test method is as follows:

[0086] Flatness was tested using a Mitutoyo Coordinate Measuring Machine (CMM) from Japan: The workpiece was fixed on the measuring table, and after calibrating the probe, 25 measurement points were evenly selected within the effective area of ​​the plane to be measured according to a 5×5 grid. Three-dimensional coordinates were collected point by point using a contact probe, and the minimum distance between two parallel planes encompassing all measurement points was calculated using the minimum area method with the accompanying measurement software. This minimum distance was taken as the flatness of the plane to be measured. Each sample was measured three times, and the average value was taken as the final test result.

[0087] Roughness was tested using a Mitutoyo roughness tester (SJ-220) from Japan: After calibrating the instrument, three positions were evenly selected on the surface of the sample to be tested, with the probe moving perpendicular to the main machining texture of the surface; the cutoff wavelength was set to 0.8 mm, the evaluation length to 4.0 mm, and the measurement speed to 0.5 mm / s, and the arithmetic mean roughness Ra was measured. The average value of the measurement results at the three positions was taken as the final test result.

[0088] The specific test results are shown in Table 1.

[0089] Table 1

[0090] Flatness, micrometers Roughness (Ra), micrometers Example 1 3 0.2 Example 2 5 0.4 Comparative Example 1 20 0.8 Comparative Example 2 50 6.0 Comparative Example 3 60 5.2 Comparative Example 4 11 1.2 Comparative Example 5 13 0.8

[0091] As shown in Table 1, the processing method provided in this application yields a metal ring with a well-planned grinding head mating reference surface, exhibiting a flatness of only 3-5 micrometers, significantly lower than the flatness of existing technologies (10-30 micrometers). Furthermore, the roughness of the grinding head mating reference surface is low, ranging from 0.1 to 0.6 micrometers. In addition, the processing method of this application demonstrates good stability, with minimal fluctuations in the flatness of the grinding head mating reference surface across different batches of metal rings, indicating excellent stability.

[0092] As can be seen from Example 1 and Comparative Example 1, the choice of grinding wheel type in the technical solution of this application also affects the final flatness effect. Only by selecting the composite grinding wheel provided in this application can the technical effect described in this application be achieved.

[0093] As can be seen from Example 1 and Comparative Example 2, the type of grinding machine used in this application and the grinding working surface of the grinding wheel will affect the flatness of the grinding head mating reference surface of the innermost metal ring. Only by using the grinding machine described in this application that grinds through the circumference of the grinding wheel can the technical effect of this application be achieved.

[0094] As can be seen from Examples 2 and Comparative Examples 3-5, the use of coolant, the coordination of rough and fine grinding processes, and the method of fixing the metal ring in the processing method of this application all affect the flatness of the mating reference surface of the grinding head of the metal ring. Only by using the coolant described in the processing method of this application, the grinding parameters combining rough and fine grinding, and the fixing method can the technical effect of this application be achieved.

[0095] The processing method provided in this application enables the flatness of the grinding head mating reference surface of the retaining ring's metal ring to be stabilized at 3-8 micrometers, significantly reducing the flatness of the grinding head mating reference surface of the retaining ring in the prior art. This retaining ring, with its high stability and extremely low flatness, can minimize problems such as tilting, localized suspension, or uneven stress that easily occur after installation during subsequent mounting and use with the grinding head. This further ensures uniform pressure distribution in the retaining ring and the wafer's peripheral area, ultimately improving the overall flatness of the wafer, film thickness uniformity, and processing yield.

[0096] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for processing a retaining ring with micron-level flatness, characterized in that, The grinding head mating reference surface of the retaining ring is processed by grinding, including the following steps: The retaining ring is fixed on the worktable of the grinding machine, so that the grinding head mating reference surface of the metal ring faces the processing component; the grinding head mating reference surface is ground by a grinding wheel, and after the grinding is completed, a retaining ring with a mating reference surface with micron-level flatness is obtained, the flatness of the grinding head mating reference surface is 1 to 8 microns; the abrasive of the grinding wheel is selected from one or more of cubic boron nitride particles and diamond particles.

2. The processing method according to claim 1, characterized in that, The surface roughness of the grinding head's mating reference surface is 0.1–0.6 micrometers; And / or, the abrasive of the grinding wheel is a composite abrasive of cubic boron nitride particles and diamond particles; And / or, the fixing method is selected from one or more of clamp fixing and adhesive fixing; And / or, the grinding machine is a rotary table grinding machine, the worktable is a rotary worktable, and the rotation speed of the worktable is 100-180 rpm.

3. The processing method according to claim 2, characterized in that, The rotary table grinder grinds the workpiece by the circumference of the grinding wheel; And / or, based on the total mass of the abrasive particles, the content of the cubic boron nitride abrasive particles is 40–80 wt%; And / or, based on the total mass of the abrasive particles, the content of the diamond abrasive particles is 20–60 wt%; And / or, the particle size of the abrasive particles in the grinding wheel is 150~300 mesh; And / or, the grinding wheel has a hardness grade of K; And / or, the abrasive concentration of the grinding wheel is 75~125%.

4. The processing method according to claim 1, characterized in that, The parameters of the grinding process include one or more of the following technical features: The spindle speed is 800–2000 rpm; The depth of a single grinding pass is 1 to 50 micrometers; The total grinding time is 7–12 minutes; And / or, grinding fluid is continuously supplied to the contact grinding zone between the grinding wheel and the metal ring for cooling during the grinding process.

5. The processing method according to claim 4, characterized in that, The grinding process includes rough grinding and fine grinding performed sequentially.

6. The processing method according to claim 5, characterized in that, The parameters of the rough grinding process include one or more of the following technical features: The removal margin is 50–120 micrometers; The time is 5 to 7 minutes; The depth of a single grinding pass is 1 to 50 micrometers.

7. The processing method according to claim 5, characterized in that, The parameters of the fine grinding process include one or more of the following technical features: The amount of residue removed is 1–15 micrometers; The time is 2 to 4 minutes; The depth of a single grinding pass is 0.5 to 30 micrometers.

8. A retaining ring with micron-level flatness, characterized in that, The retaining ring is obtained by processing using the processing method described in any one of claims 1 to 7; the retaining ring includes a metal ring and a plastic ring fixedly connected to one side of the metal ring, and the flatness of the grinding head of the metal ring abutting the reference surface is 1 to 8 micrometers.

9. The retaining ring according to claim 8, characterized in that, The metal includes one or more of iron and stainless steel; And / or, the plastic is selected from one or more of polyphenylene sulfide and polyetheretherketone; And / or, the surface roughness of the grinding head mating reference surface is 0.1 to 0.6 micrometers.

10. The application of the retaining ring obtained by the processing method according to any one of claims 1 to 7, or the retaining ring according to any one of claims 8 to 9, in a chemical mechanical polishing process, wherein the application includes one or more of the following: Used to improve the overall flatness of wafers; Used to improve the uniformity of film wafer thickness; Used to improve the processing yield of products.

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