A polishing process for chemical mechanical polishing

Abstract

The present application relates to the technical field of chemical mechanical polishing pad, and provides a polishing process for chemical mechanical polishing, which comprises the following steps: installing a magnetic polishing pad on a rotating disc, wherein the magnetic polishing pad contains magnetic gold nanoparticles; the polishing area comprises a first area and a second area, and a workpiece to be polished is clamped in the first area; starting the rotating disc, and inputting polishing liquid to the magnetic polishing pad from a polishing liquid releasing device; starting a magnetic field control system, controlling the first electrically controlled permanent magnet assembly in the first area to demagnetize, controlling the second electrically controlled permanent magnet assembly in the second area to magnetize, and simultaneously controlling the first electrically controlled permanent magnet assembly to exert a certain load on the workpiece to be polished for polishing. According to the polishing process, the first area is demagnetized, the heat absorption effect of the magnetic polishing pad in the demagnetization process is utilized, the high temperature generated due to high-speed friction is effectively reduced, the second area is magnetized, the temperature difference on the surface of the workpiece is reduced by the high thermal conductivity of the magnetic gold nanoparticles, and the polishing uniformity is improved.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing pad technology, and more specifically, to a chemical mechanical polishing process. Background Technology

[0002] To achieve ultra-smooth, damage-free, and micro-defect-free high-quality processed surfaces for semiconductor wafers, various ultra-precision polishing methods have been proposed. Chemical mechanical polishing (CMP) is considered almost the only surface finishing technology to date that can provide globally planarized hard and brittle optoelectronic materials. It utilizes a chemical reaction to oxidize the wafer surface, forming a softened layer with lower hardness, weaker strength, and less adhesion. Mechanical material removal then occurs through the relative motion between the polishing pad, ultrafine abrasive particles, and the wafer. Unlike purely chemical or mechanical polishing methods, CMP achieves a balance between chemical and mechanical actions, avoiding the problems of slow polishing speed, low surface flatness, and excessive damage that often occur with the former two methods.

[0003] Polishing pads are a core component in the CMP process, serving to store and transport polishing slurry and remove micro-bumps from the wafer surface. Their mechanical properties, including hardness, elasticity, compressibility, as well as microstructure and surface roughness, all affect the final polishing effect of the wafer.

[0004] CMP polishing pads consist of a polishing layer, a buffer layer, and a matrix material. The polishing layer is the core of the polishing pad and is usually composed of polymer materials, which may or may not contain abrasives, and is prepared as a porous foam material.

[0005] The prior art patent CN201610391966.1 discloses a polishing layer and its preparation method, as well as a chemical mechanical polishing pad. The polishing layer is formed by mixing and curing a polyurethane prepolymer, a curing agent, and functional fillers. The polyurethane prepolymer is formed by reacting polycarbonate polyol and polyfunctional cyanate. While this patent produces a polishing pad with stable mechanical properties, the high-speed friction between the polishing pad and the workpiece during polishing generates a large amount of heat. The inconsistent contact degree between different areas of the polishing pad and the workpiece results in inconsistent heat dissipation, causing temperature differences between different areas of the workpiece and leading to inconsistent polishing removal rates and affecting polishing uniformity.

[0006] Furthermore, excessively high porosity in the polishing layer results in lower surface strength and hardness of the polishing pad, leading to poor wear resistance. During polishing, the polishing pad is prone to deformation, altering the fit between the pad and the workpiece, affecting material removal rate and surface planarization, and potentially even deteriorating workpiece flatness. Conversely, excessively low porosity in the polishing layer leads to higher pad density, reducing the layer's ability to store and transport polishing fluid. This can result in uneven distribution of the polishing fluid between the workpiece and the pad, impacting polishing efficiency and the uniformity of material removal from the workpiece surface. Simultaneously, low porosity hinders the removal of polishing residue, which may accumulate between the pad and the workpiece surface, further affecting polishing quality.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The purpose of this invention is to propose a chemical mechanical polishing process to solve the problem in the prior art where, during the polishing process, the high-speed friction between the polishing pad and the workpiece generates a large amount of heat, and the inconsistent contact degree and heat dissipation performance between different areas of the polishing pad cause temperature differences in different areas of the workpiece, resulting in inconsistent polishing removal rates and affecting polishing uniformity.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0010] A chemical mechanical polishing process, the polishing process comprising the following steps:

[0011] S1. Install a magnetic polishing pad on a polishing rotary disk, wherein the magnetic polishing pad contains magnetic gold nanoparticles;

[0012] S2. The polishing area includes a first area and a second area, and the workpiece to be polished is clamped in the first area.

[0013] S3. Start the rotating disk and input polishing liquid into the magnetic polishing pad through the polishing liquid release device;

[0014] S4. Start the magnetic field control system, control the first electrically controlled permanent magnet component in the first area to demagnetize, control the second electrically controlled permanent magnet component in the second area to magnetize, and simultaneously control the first electrically controlled permanent magnet component to apply a certain load to the workpiece to be polished for polishing.

[0015] Furthermore, the polishing fluid release device is located at the center above the rotating disk.

[0016] Furthermore, the central axis of the workpiece to be polished is located at the center of the first region.

[0017] Furthermore, the workpiece to be polished is clamped in a fixture.

[0018] Furthermore, the magnetic polishing pad includes a magnetic polishing layer, a buffer layer, and a transparent base pad from top to bottom, and the buffer layer is bonded to the magnetic polishing layer and the transparent base pad by pressure-sensitive adhesive.

[0019] Furthermore, the magnetic polishing layer includes a polyurethane prepolymer, a curing agent, and a functional filler, wherein the mass ratio of the polyurethane prepolymer, the curing agent, and the functional filler is 100:(10~25):(5~8).

[0020] Furthermore, the functional fillers include magnetic gold nanoparticles and nano-alumina.

[0021] Furthermore, the preparation of the magnetic gold nanoparticles includes the following steps:

[0022] Dry magnetic Fe3O4 nanoparticles were acid-washed and ultrasonically dispersed in 2-pyrrolidone for 30 min to form dispersion A, with a concentration of 1 mg / mL. Gold nanoparticles were dispersed in 0.1 M PVP ethanol solution, ultrasonicated for 10-20 min, centrifuged and washed three times, and the precipitate was redispersed in 2-pyrrolidone to form dispersion B, with a concentration of 5 mg / mL. Dispersion A and dispersion B were mixed to form a mixture with a volume ratio of 2:1. The mixture was ultrasonicated for 30 min and then placed in a water bath at 40-50℃ and stirred for 10-12 h. Finally, the magnetic Fe3O4 nanoparticles that did not enter the mixture were separated by centrifugation.

[0023] Furthermore, the gold nanoparticles have a hollow internal structure with openings, the diameter of the gold nanoparticles is 350~400nm, and the diameter of the openings of the gold nanoparticles is 100~300nm.

[0024] Furthermore, the size of the magnetic Fe3O4 nanoparticles is less than 100 nm.

[0025] Compared with existing technologies, the chemical mechanical polishing process of the present invention has the following beneficial effects:

[0026] 1) The chemical mechanical polishing process described in this invention utilizes the synergistic effect of magnetic gold nanoparticles and magnetic field control. A magnetic field control system differentiates the control of the electrically controlled permanent magnet components in the first region (the contact area of ​​the workpiece to be polished) and the second region (the non-contact area of ​​the workpiece to be polished), achieving zoned management of the magnetic polishing pad temperature. In the first region, demagnetization is performed, leveraging the heat absorption effect of the magnetic polishing pad during demagnetization and the high thermal conductivity of the magnetic gold nanoparticles to effectively reduce the high temperature generated by high-speed friction. In the second region, magnetization facilitates demagnetization of the polishing pad in the first region. Furthermore, the magnetic polishing pad heats up during magnetization, preventing a decline in polishing fluid performance due to excessively low temperatures. Simultaneously, the high thermal conductivity of the magnetic gold nanoparticles dissipates excess heat, preventing localized overheating. This significantly reduces the temperature difference on the workpiece surface and improves polishing uniformity.

[0027] 2) The chemical mechanical polishing process described in this invention optimizes the mixing mass ratio of polyurethane prepolymer, curing agent, and functional filler, and designs a composite filler of magnetic gold nanoparticles and nano-alumina. The magnetic gold nanoparticles and nano-alumina work synergistically to achieve bilevel pore structure regulation. While ensuring high porosity of the polished layer, it improves the surface strength and hardness of the polished layer, enhances the wear resistance of the polished layer, and breaks through the limitation that a single filler cannot simultaneously achieve both hardness and porosity. It achieves the optimal balance among porosity, mechanical strength, and polishing removal rate. Attached Figure Description

[0028] Figure 1 This is a side view of the polishing equipment used in a chemical mechanical polishing process according to an embodiment of the present invention.

[0029] Figure 2 This is one of the top view structural schematic diagrams of a polishing device for a chemical mechanical polishing process according to an embodiment of the present invention;

[0030] Figure 3 This is a second top view schematic diagram of the polishing equipment for a chemical mechanical polishing process according to an embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Workpiece to be polished; 2. Magnetic polishing pad; 3. Rotary disk; 4. Spindle; 5. Polishing fluid release device; 61. First electrically controlled permanent magnet assembly; 62. Second electrically controlled permanent magnet assembly; 71. First region; 72. Second region. Detailed Implementation

[0033] To make the technical means and the objectives and effects of the present invention easier to understand, the embodiments of the present invention will be described in detail below.

[0034] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "lateral," "longitudinal," and "center," are only used to explain the relative positional relationships and connections between components in a specific state (as shown in the accompanying drawings). They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0035] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] In the existing technology, during the polishing process, the high-speed friction between the polishing pad and the workpiece generates a large amount of heat. However, the different contact levels between different areas and the polishing pad result in inconsistent heat dissipation performance, causing temperature differences in different areas of the workpiece and leading to inconsistent polishing removal rates, which affects the uniformity of polishing.

[0039] Furthermore, excessively high porosity in the polishing layer results in lower surface strength and hardness of the polishing pad, leading to poor wear resistance. During polishing, the polishing pad is prone to deformation, altering the fit between the pad and the workpiece, affecting material removal rate and surface planarization, and potentially even deteriorating workpiece flatness. Conversely, excessively low porosity in the polishing layer leads to higher pad density, reducing the layer's ability to store and transport polishing fluid. This can result in uneven distribution of the polishing fluid between the workpiece and the pad, impacting polishing efficiency and the uniformity of material removal from the workpiece surface. Simultaneously, low porosity hinders the removal of polishing residue, which may accumulate between the pad and the workpiece surface, further affecting polishing quality.

[0040] To solve the above technical problems, such as Figures 1-3 As shown, the applicant proposes a chemical mechanical polishing (CMP) device. The main shaft 4 of the polishing device drives a rotating disk 3 to rotate, and a magnetic polishing pad 2 adheres to the rotating disk 3 and rotates with it. An electrically controlled permanent magnet assembly 6, a polishing liquid release device 5, and a workpiece 1 to be polished are arranged above the polishing area.

[0041] Therefore, the applicant proposes a chemical mechanical polishing process, which includes the following steps:

[0042] S1. Install the magnetic polishing pad 2 on the polishing rotating disk 3. The magnetic polishing pad 2 contains magnetic gold nanoparticles.

[0043] S2. The polishing area includes a first area 71 and a second area 72. The workpiece 1 to be polished is clamped in the first area 71.

[0044] S3. Start the rotating disk 3, and the polishing liquid is input into the magnetic polishing pad 2 by the polishing liquid release device 5;

[0045] S4. Start the magnetic field control system, control the first electrically controlled permanent magnet component 61 in the first region 71 to demagnetize, control the second electrically controlled permanent magnet component 62 in the second region 72 to magnetize, and simultaneously control the first electrically controlled permanent magnet component 61 to apply a certain load to the workpiece 1 to be polished for polishing.

[0046] This application proposes a chemical mechanical polishing (CMP) process. The workpiece 1 to be polished is clamped in a first region 71. During polishing, the magnetic polishing pad 2 in the first region 71 generates a large amount of heat through high-speed friction with the workpiece 1, resulting in a high temperature in the first region 71. The first electrically controlled permanent magnet assembly 61 in the first region 71 is demagnetized. The magnetic polishing pad 2 cools during demagnetization, absorbing the heat generated during the polishing process. Combined with the magnetic gold nanoparticles in the magnetic polishing pad 2, this significantly reduces the temperature of the first region 71. The second region 72 has a relatively lower temperature compared to the first region 71. The second electrically controlled permanent magnet assembly 62 in the second region 72 is magnetized. The heat released during the magnetization process of the magnetic polishing pad 2 maintains the active temperature of the polishing fluid, preventing viscosity increase and reaction rate decrease due to low temperature. Simultaneously, the high thermal conductivity of the magnetic gold nanoparticles dissipates excess heat, preventing localized overheating. This dynamic temperature control mechanism significantly reduces the temperature difference on the surface of the workpiece 1, improving the consistency of material removal.

[0047] The chemical mechanical polishing process proposed in this application has steps S1 to S4 that are interconnected and serve multiple purposes:

[0048] I. Precise Temperature Control Capability: A magnetic field control system differentiates the temperature of the electrically controlled permanent magnet assembly 6 in the first region 71 (the contact area of ​​the workpiece 1 to be polished) and the second region 72 (the non-contact area of ​​the workpiece 1 to be polished), achieving zoned management of the magnetic polishing pad 2's temperature. Demagnetization is performed in the first region 71, utilizing the heat absorption effect of the magnetic polishing pad 2 during demagnetization and the high thermal conductivity of the magnetic gold nanoparticles to effectively reduce the high temperature generated by high-speed friction. Magnetization is performed in the second region 72. This facilitates demagnetization of the polishing pad in the first region 71, and the heat release during magnetization maintains the active temperature of the polishing fluid, preventing viscosity increases and reaction rate decreases due to low temperatures. Simultaneously, the high thermal conductivity of the magnetic gold nanoparticles dissipates excess heat, preventing localized overheating. This dynamic temperature control mechanism significantly reduces the temperature difference on the surface of the workpiece 1 to be polished, improving the consistency of material removal.

[0049] II. Improved Polishing Uniformity: In traditional processes, the surface of the workpiece 1 suffers from inconsistent polishing removal rates due to temperature differences. This process, however, utilizes the synergistic effect of magnetic gold nanoparticles and magnetic field control to achieve micro-environmental regulation of the interface between the magnetic polishing pad 2 and the workpiece 1. During demagnetization, the cooling effect of the magnetic polishing pad 2 not only reduces localized high temperatures but also optimizes the uniformity of material removal by altering the flowability and chemical reaction rate of the polishing slurry. Simultaneously, the magnetization operation in the second region 72 enhances the uniformity of the polishing slurry distribution, further improving the overall polishing effect.

[0050] III. Enhanced Process Stability: The high thermal conductivity and magnetic responsiveness of magnetic gold nanoparticles enable the magnetic polishing pad 2 to respond quickly to changes in the magnetic field, achieving efficient heat transfer and dispersion. This reduces the impact of thermal stress on the surface of the workpiece 1 to be polished, improving process stability and repeatability. The high thermal conductivity of magnetic gold nanoparticles can quickly dissipate and disperse polishing heat, reducing deformation of the void structure caused by thermal stress, further improving polishing quality and making the polished surface smoother and more uniform. The low coefficient of thermal expansion of magnetic gold nanoparticles can suppress dimensional fluctuations in the polishing layer caused by temperature changes, ensuring the long-term stability of the void structure. In high-speed polishing (>100 rpm), the surface temperature of the polishing layer filled with magnetic gold nanoparticles can be reduced by 10~15℃, significantly improving process stability. The introduction of magnetic gold nanoparticles not only serves as a temperature control medium but also has a catalytic effect, improving the chemical-mechanical efficiency of the polishing fluid.

[0051] IV. Energy Saving and Environmental Protection Potential: Compared to traditional external cooling systems, this process achieves temperature management through endogenous magnetic field regulation, reducing energy consumption and the use of cooling media, which aligns with the development trend of green manufacturing. Simultaneously, the reusability of the magnetic polishing pad 2 and the precision of magnetic field control also contribute to reducing process costs and environmental burden.

[0052] Magnetic gold nanoparticles possess high thermal conductivity, magnetic responsiveness, and catalytic activity. The applicant also unexpectedly discovered that the addition of magnetic gold nanoparticles has the following additional effects:

[0053] I. Increase porosity;

[0054] II. Enhanced mechanical properties: The rigid shell of gold nanoparticles can enhance the compressive strength of the polished layer and prevent the voids from collapsing during the polishing process. At the same time, the hollow structure undergoes elastic deformation under stress, absorbing impact energy and reducing surface scratches.

[0055] 3. Improve wear resistance: The high hardness of gold materials can significantly improve the wear resistance of the polished layer.

[0056] Fourth, the open structure of gold nanoparticles promotes the flow of polishing fluid, ensuring a continuous supply of polishing fluid to the polishing interface, improving polishing efficiency and polishing removal rate, while quickly removing abrasive debris and reducing secondary scratches.

[0057] Fifth, gold nanoparticles can improve the antibacterial properties of polishing pads, thereby improving their durability and extending their service life.

[0058] Specifically, the polishing liquid release device 5 is located at the center above the rotating disk 3, and works with the centrifugal force of the rotating disk 3 to achieve radial uniform distribution of the polishing liquid.

[0059] Specifically, the central axis of the workpiece 1 to be polished is located at the center of the first region 71. When the central axis of the workpiece 1 to be polished coincides with the center of the first region 71, the frictional heat diffuses outward in a concentric circle pattern, avoiding the asymmetric thermal gradient caused by eccentricity; the cooling effect of the demagnetizing region (first region) can uniformly cover the entire workpiece contact surface, eliminating the temperature difference between the edge and the center.

[0060] Specifically, the workpiece 1 to be polished is clamped in a fixture (not shown in the figure).

[0061] Specifically, the magnetic polishing pad 2 includes a magnetic polishing layer, a buffer layer, and a transparent base pad from top to bottom. The buffer layer is bonded to the magnetic polishing layer and the transparent base pad with pressure-sensitive adhesive.

[0062] Specifically, the magnetic polishing layer comprises a polyurethane prepolymer, a curing agent, and a functional filler, wherein the mass ratio of the polyurethane prepolymer, curing agent, and functional filler is 100:(10~25):(5~8). The functional filler accounts for 5~8% of the total content; too much will lead to a decrease in material hardness and insufficient system support, while too little will lead to a decrease in the material's ability to retain the polishing liquid and a decrease in polishing removal efficiency.

[0063] Specifically, the functional fillers include magnetic gold nanoparticles and nano-alumina.

[0064] Specifically, the curing agent includes 4,4'-diamino-3,3'-dichlorodiphenylmethane, polyether polyamine D3000, and tetrafunctional polyether amine T5000.

[0065] Specifically, the alumina nanoparticles have a particle size of 10–20 nm.

[0066] The preparation method of gold nanoparticles is a prior art. The preparation method of gold nanoparticles adopts the preparation method described in Example 2 of the prior art publication number CN114160802B. The prepared gold nanoparticles have a hollow structure inside and contain openings.

[0067] Specifically, the preparation method of gold nanoparticles includes the following steps: For the preparation of conventional TiO2 template spheres, by weight, 0.3 parts of ultrapure water and 1.8 parts of dodecylamine are added to a beaker containing a 200-part ethanol / acetonitrile mixed solution (ethanol:acetonitrile = 3:1). After stirring for 5-15 minutes, 4.5 parts of titanium isopropoxide are rapidly injected. After continuous stirring at room temperature for 3-6 hours, the mixture is centrifuged, washed, and freeze-dried to obtain conventional TiO2 template spheres. Alternatively, by weight, 9 parts of TiO2 template spheres, 30 parts of ultrapure water, 6.2 parts of methanol solution, and 8.2 parts of ethanol solution are mixed and stirred for 10-30 minutes. Then, 13 parts of chloroauric acid solution with a concentration of 1 g / 10 ml and 13 parts of bis(chloroauric(I))bis(diphenylphosphine)methane are added and stirred for 10-30 minutes. After stirring, the mixture is irradiated under 100-500 W ultraviolet light for 7-14 days. After centrifugation and precipitation, the precipitate is washed three times with ethanol and deionized water to obtain the final product.

[0068] Specifically, the gold nanoparticles have a hollow internal structure with openings, the diameter of the gold nanoparticles is 350~400nm, and the diameter of the openings of the gold nanoparticles is 100~300nm.

[0069] The preparation method of magnetic Fe3O4 nanoparticles is a prior art. The preparation method of magnetic Fe3O4 nanoparticles adopts the preparation method described in Example 1 of the prior art publication number CN101269845B. The size of the magnetic Fe3O4 nanoparticles prepared is less than 100 nm.

[0070] The preparation of the magnetic gold nanoparticles includes the following steps:

[0071] First, dried magnetic Fe3O4 nanoparticles were acid-washed and dispersed in 2-pyrrolidone, then sonicated for 30-40 min to form dispersion A, with a concentration of 1 mg / mL. Next, gold nanoparticles were dispersed in 0.1 M PVP ethanol solution and sonicated for 10-20 min for pretreatment. The nanoparticles were then centrifuged and washed three times to remove free PVP. Finally, the precipitate was redispersed in 2-pyrrolidone to form dispersion B, with a concentration of 5 mg / mL. Dispersion A and dispersion B were mixed to form a mixture with a volume ratio of 2:1. The mixture was sonicated for 30 min and then placed in a 40-50℃ water bath to slowly evaporate the solvent. A moderate temperature was maintained to avoid high temperatures causing Fe3O4 oxidation or gold nanoparticle aggregation. The mixture was stirred for 10-12 h to improve loading uniformity. Finally, the magnetic Fe3O4 nanoparticles that did not enter the mixture were separated by centrifugation.

[0072] Among them, the acid-washed magnetic Fe3O4 nanoparticles can, on the one hand, remove organic ligands or oxide impurities such as oleic acid and oleylamine remaining on the surface of Fe3O4, reducing the tendency to agglomerate; on the other hand, after acid washing, hydroxyl groups (-OH) are generated on the surface of Fe3O4, which enhances the interaction with 2-pyrrolidone and improves the uniformity of dispersion A.

[0073] Pre-treatment of gold nanoparticles can, on the one hand, remove residual template agents on the surface of gold nanoparticles, thus preventing residual template agents from affecting subsequent loading; on the other hand, it can improve the wettability of the inner wall. In addition, PVP can also prevent the aggregation of gold nanoparticles.

[0074] The acid-washed magnetic Fe3O4 nanoparticles and the pretreated gold nanoparticles were both dispersed in 2-pyrrolidone. This is because: 1. Compared with ethanol or water, 2-pyrrolidone evaporates slowly, which is conducive to the full contact and loading of Fe3O4 and gold nanoparticles during the slow evaporation of the solvent; 2. 2-pyrrolidone has high chemical inertness to Fe3O4 and gold nanoparticles, avoiding the formation of reaction byproducts.

[0075] However, through specific experiments, the applicant discovered the following drawbacks when using magnetic gold nanoparticles and nano-alumina as fillers: 1. Magnetic gold nanoparticles and nano-alumina have high specific surface area and surface energy, making them prone to agglomeration in the polishing layer matrix, forming stress concentration points. This leads to increased surface roughness of the polishing layer and reduced polishing uniformity. 2. The interfacial interaction between magnetic gold nanoparticles / nano-alumina and the polymer matrix is ​​weak, making them prone to detachment during polishing, forming micro-pits or scratches, thus affecting polishing quality.

[0076] To address the aforementioned technical issues, the applicant proposed grafting polyethylene glycol onto magnetic gold nanoparticles.

[0077] Specifically, grafting polyethylene glycol onto magnetic gold nanoparticles includes the following steps:

[0078] T1. Plasma cleaning of magnetic gold nanoparticles: Use an oxygen plasma cleaner to clean the magnetic gold nanoparticles. The power is 70~90W, the time is 4~8min, and the oxygen flow rate is 20~40sccm.

[0079] T2. Grafted polyethylene glycol: First, the plasma-treated magnetic gold nanoparticles are dispersed in water to form reaction solution A, with a concentration of 1 mg / mL, and ultrasonically dispersed for 30 min. Then, mercapto-terminated polyethylene glycol (HS-PEG-OH) is dissolved in anhydrous ethanol to form reaction solution B, with a concentration of 0.6~1 mg / mL. Reaction solution B is added to reaction solution A, and the reaction temperature is room temperature with a stirring time of 30~60 min. The supernatant is removed by centrifugation, and then washed with anhydrous ethanol. The centrifugation is repeated 3 times, and then the mixture is dried.

[0080] Plasma cleaning serves multiple purposes: First, it can thoroughly remove organic contaminants from the surface of magnetic gold nanoparticles; second, it can introduce oxygen-containing polar groups into the magnetic gold nanoparticles, improving their hydrophilicity and reactivity, reducing the contact angle from 60-80° before cleaning to below 10°, thereby improving the dispersion of magnetic gold nanoparticles and enabling better grafting of polyethylene glycol; third, it helps functional fillers form excellent dispersions in polyurethane prepolymer systems, better fulfilling the functions of the fillers.

[0081] The settings for power, time, and oxygen flow rate in plasma cleaning ensure cleaning efficiency while avoiding excessive etching that could damage the structure of the magnetic gold nanoparticles.

[0082] Magnetic gold nanoparticles were grafted with thiol-terminated polyethylene glycol (HS-PEG-OH). The thiol groups (-SH) are strongly covalently bonded to the gold surface (Au-S, bond energy ~40–50 kcal / mol), resulting in stable bonding. The PEG chains are anchored to the magnetic gold nanoparticles via sulfur atoms. Furthermore, after grafting, the PEG ends with hydroxyl groups (-OH), retaining the hydrophilicity and hydrogen bonding ability of polyethylene glycol.

[0083] The concentrations, reaction temperature, and stirring time of reaction solutions A and B are set to ensure the successful preparation of polyethylene glycol-grafted magnetic gold nanoparticles while avoiding high grafting efficiency, thus preventing the formation of a dense hydrophilic layer on the outside of the magnetic gold nanoparticles.

[0084] Grafting polyethylene glycol onto magnetic gold nanoparticles has the following advantages:

[0085] First, the magnetic gold nanoparticles grafted with polyethylene glycol are uniformly dispersed in the polishing layer matrix, making them less prone to agglomeration and improving polishing uniformity.

[0086] Second, the magnetic gold nanoparticles grafted with polyethylene glycol have a stronger interfacial interaction with the polymer matrix, making them less likely to fall off during polishing and thus avoiding affecting the polishing quality.

[0087] Third, the magnetic gold nanoparticles grafted with polyethylene glycol can also improve the problem of alumina agglomeration: On the one hand, the hydrophilic long chains of the magnetic gold nanoparticles grafted with polyethylene glycol form physical adsorption with the hydroxyl groups (-OH) on the surface of alumina nanoparticles through hydrogen bonds or van der Waals forces, enhancing the interfacial bonding between the two; the flexible chains of polyethylene glycol (PEG) can act as "molecular bridges" to directly alleviate the direct contact between rigid alumina nanoparticles and improve the dispersibility of alumina nanoparticles; on the other hand, the polyethylene glycol-PEG grafted layer can form a hydrophilic crown on the surface of the gold nanoparticle container, preventing the agglomeration of alumina nanoparticles through steric hindrance, while maintaining the suspension stability of the composite filler in the polishing solution, indirectly affecting the synergistic effect of the two.

[0088] IV. Reduce costs.

[0089] Specifically, the molecular weight of mercapto-terminated polyethylene glycol is 2000-3000.

[0090] The functional fillers include magnetic gold nanoparticles grafted with polyethylene glycol and nano-alumina.

[0091] By optimizing the mixing mass ratio of polyurethane prepolymer, curing agent, and functional filler, and through the design of a composite filler consisting of magnetic gold nanoparticles grafted with polyethylene glycol and nano-alumina, the synergistic effect of nano-alumina and magnetic gold nanoparticles grafted with polyethylene glycol achieves bilevel pore structure regulation. This ensures high porosity of the polished layer while improving its surface strength and hardness, thus enhancing its wear resistance. This overcomes the limitation of a single filler not being able to balance hardness and porosity, achieving an optimal balance among porosity, mechanical strength, and polishing removal rate.

[0092] Specifically, the mass ratio of the nano-alumina to the magnetic gold nanoparticles grafted with polyethylene glycol is 1:1~2.

[0093] The mass ratio of nano-alumina to magnetic gold nanoparticles grafted with polyethylene glycol is 1:1~2, which reduces costs while achieving excellent performance of functional fillers.

[0094] Specifically, the alumina nanoparticles have a particle size of 10–20 nm.

[0095] Nanoscale particle size (typically <100 nm) can reduce surface scratches and improve the surface planarization of workpieces.

[0096] Specifically, the curing agent includes 4,4'-diamino-3,3'-dichlorodiphenylmethane, polyether polyamine D3000, and tetrafunctional polyether amine T5000.

[0097] The curing agent is designed to lower the curing temperature, prevent the decomposition of the polyethylene glycol in the magnetic gold nanoparticles after grafting with polyethylene glycol, and ensure the integrity of the filler function.

[0098] The applicant achieved multiple benefits by optimizing the mixing mass ratio of polyurethane prepolymer, curing agent, and functional filler, as well as the synergistic effect of nano-alumina and magnetic gold nanoparticles grafted with polyethylene glycol:

[0099] I. A precise balance between porosity and mechanical properties was achieved, which improved the surface strength and hardness of the polishing layer while ensuring high porosity, thus enhancing the wear resistance of the polishing layer. (1) Achieving dual-level pore structure control: The particle size of nano alumina is 10-20nm, which fills the gaps in the polyurethane network to reinforce the skeleton and form submicron-level pores (0.1-1um), which improves the porosity and surface hardness, avoiding the decrease in strength caused by high porosity. The diameter of gold nanoparticles is 350-400nm, and the diameter of the opening of gold nanoparticles is 100-300nm. Gold nanoparticles construct through channels, which greatly increases the amount of polishing liquid retained and solves the problem of uneven transport caused by low porosity. (2) Optimized mechanical properties: The cross-linking reaction between polyurethane prepolymer and curing agent forms a dense network structure, which, combined with the rigid filling of nano-alumina, significantly improves the surface strength and hardness of the polishing layer, reduces deformation caused by pore collapse during polishing, and ensures stable adhesion between the workpiece and the polishing pad; the high hardness of nano-alumina can effectively resist friction and wear during polishing, extend the service life of the polishing pad, and reduce particulate contamination caused by wear. Magnetic gold nanoparticles grafted with polyethylene glycol have two advantages: firstly, gold itself has a high modulus, and adding magnetic gold nanoparticles as fillers can significantly improve the hardness and wear resistance of the polishing layer, thereby improving wear resistance; secondly, the magnetic gold nanoparticles grafted with polyethylene glycol can covalently bond with the matrix, suppress interfacial stress concentration, and greatly reduce the deformation rate of the polishing pad.

[0100] Second, the polyethylene glycol-grafted magnetic gold nanoparticles possess an open structure, and the PEG segments on their surface provide hydrophilicity, promoting the adsorption of polishing slurry. This allows them to act as micro / nano reservoirs, continuously and controllably releasing polishing slurry during the polishing process, avoiding localized drying or over-release, ensuring uniform lubrication and chemical reaction on the workpiece surface, and improving polishing efficiency and quality. Simultaneously, the open structure of the gold nanoparticles, combined with the hydrophilicity of the polyethylene glycol-grafted magnetic gold nanoparticles, promotes the rapid removal of polishing residues, reducing residue accumulation by 40%, avoiding surface scratches caused by buildup, and further improving polishing quality.

[0101] Third, nano-alumina can also act as a catalyst. The hydroxyl groups (-OH) on the surface of nano-alumina synergistically promote the chemical reaction on the workpiece surface with the polishing liquid (such as KOH), thereby improving the polishing removal rate.

[0102] Fourth, the rigid shell of gold nanoparticles can enhance the compressive strength of the polished layer and prevent the voids from collapsing during the polishing process. At the same time, the hollow structure undergoes elastic deformation under stress, absorbing impact energy and reducing surface scratches.

[0103] V. The high thermal conductivity of magnetic gold nanoparticles can rapidly dissipate and disperse polishing heat, reducing deformation of the void structure caused by thermal stress, further improving polishing quality and making the polished surface smoother and more uniform. The low coefficient of thermal expansion of magnetic gold nanoparticles can suppress dimensional fluctuations in the polished layer caused by temperature changes, ensuring the long-term stability of the void structure. In high-speed polishing (>100 rpm), the surface temperature of the polished layer filled with gold nanoparticles can be reduced by 10~15℃, significantly improving process stability.

[0104] VI. The magnetic gold nanoparticles grafted with polyethylene glycol are uniformly dispersed in the polishing layer matrix, are less prone to agglomeration, and improve polishing uniformity.

[0105] VII. Polyethylene glycol (PEG) grafting modification enhances the interfacial interaction between magnetic gold nanoparticles and the polyurethane matrix through covalent bonding, greatly reducing the filler shedding rate and avoiding the generation of micro-pits or scratches.

[0106] 8. The addition of polyethylene glycol-grafted magnetic gold nanoparticles can improve the problem of agglomeration of nano-alumina: The hydrophilic long chains of polyethylene glycol-grafted gold nanoparticles form physical adsorption with the hydroxyl groups (-OH) on the surface of nano-alumina through hydrogen bonds or van der Waals forces, enhancing the interfacial bonding between the two; the flexible chains of polyethylene glycol (PEG) can act as "molecular bridges" to directly alleviate the direct contact between rigid nano-alumina particles and improve the dispersibility of nano-alumina; on the other hand, the polyethylene glycol-PEG grafted layer can form a hydrophilic crown on the surface of the gold nano-can, which prevents the agglomeration of nano-alumina through steric hindrance effect, while maintaining the suspension stability of the composite filler in the polishing solution, indirectly affecting the synergistic effect of the two.

[0107] The method for preparing the polished layer includes the following steps:

[0108] Polyisocyanates and polyols react to form polyurethane prepolymers;

[0109] The curing agent, nano-alumina, and polyethylene glycol-grafted modified gold nanoparticles were added to the polyurethane prepolymer and mixed thoroughly.

[0110] After being poured into the mold and cured, the mixture is cooled to room temperature and then demolded to obtain a polished layer.

[0111] Specifically, the curing time is 16-20 hours and the curing temperature is 70-80℃.

[0112] Specifically, the polyisocyanate is diphenylmethane diisocyanate, and the polyol is polycarbonate polyol.

[0113] When using the chemical mechanical polishing process described in this invention to fine polish Teos Wafer (silicon dioxide deposited silicon wafer), the first electrically controlled permanent magnet assembly 61 applies a load of 1.1 psi to the workpiece 1 to be polished, the rotation speed of the workpiece 1 is 120 rpm, the rotation speed of the magnetic polishing pad 2 is 115 rpm, the rotation speed of the workpiece 1 to be polished is 5 rpm higher than the rotation speed of the magnetic polishing pad 2, the polishing fluid is Anji-D3000, the polishing fluid flow rate is 200 mL / min, and the polishing time is 90 s / piece.

[0114] The polishing solution is an alkaline environment with a pH of 10-11. The polyethylene glycol-grafted gold nanoparticles are resistant to a pH of 2-12. There is no risk of reaction between the polishing solution and the magnetic polishing pad.

[0115] After fine polishing of Teos wafers using the polishing process described in this invention, the surface roughness Ra value of the wafer is <0.30 nm. The chemical mechanical polishing process of this invention can reliably achieve high-quality fine polishing of Teos wafers, meeting the stringent requirements for wafer surface flatness in the semiconductor manufacturing industry.

[0116] Example 1

[0117] A chemical mechanical polishing process, the polishing process comprising the following steps:

[0118] S1. Install the magnetic polishing pad 2 on the polishing rotating disk 3. The magnetic polishing pad 2 contains magnetic gold nanoparticles.

[0119] S2. The polishing area includes a first area 71 and a second area 72. The workpiece 1 to be polished is clamped in the first area 71.

[0120] S3. Start the rotating disk 3, and the polishing liquid is input into the magnetic polishing pad 2 by the polishing liquid release device 5;

[0121] S4. Start the magnetic field control system, control the first electrically controlled permanent magnet component 61 in the first region 71 to demagnetize, control the second electrically controlled permanent magnet component 62 in the second region 72 to magnetize, and simultaneously control the first electrically controlled permanent magnet component 61 to apply a certain load to the workpiece 1 to be polished for polishing.

[0122] Specifically, the polishing liquid release device 5 is located at the center above the rotating disk 3, and works with the centrifugal force of the rotating disk 3 to achieve radial uniform distribution of the polishing liquid.

[0123] Specifically, the central axis of the workpiece 1 to be polished is located at the center of the first region 71. When the central axis of the workpiece 1 to be polished coincides with the center of the first region 71, the frictional heat diffuses outward in a concentric circle pattern, avoiding the asymmetric thermal gradient caused by eccentricity; the cooling effect of the demagnetizing region (first region) can uniformly cover the entire workpiece contact surface, eliminating the temperature difference between the edge and the center.

[0124] Specifically, the workpiece 1 to be polished is clamped in a fixture.

[0125] Specifically, the magnetic polishing pad 2 includes a magnetic polishing layer, a buffer layer, and a transparent base pad from top to bottom. The buffer layer is bonded to the magnetic polishing layer and the transparent base pad with pressure-sensitive adhesive.

[0126] Specifically, the magnetic polishing layer includes a polyurethane prepolymer, a curing agent, and functional fillers.

[0127] Specifically, the functional fillers include magnetic gold nanoparticles and nano-alumina.

[0128] The preparation method of gold nanoparticles includes the following steps: For the preparation of conventional TiO2 template spheres, by weight, 0.3 parts of ultrapure water and 1.8 parts of dodecylamine are added to a beaker containing 200 parts of ethanol:acetonitrile mixed solution (ethanol:acetonitrile = 3:1), stirred for 8 min, and then 4.5 parts of titanium isopropoxide are quickly injected. After stirring continuously at room temperature for 5 h, the mixture is centrifuged, washed, and freeze-dried to obtain conventional TiO2 template spheres. Alternatively, by weight, 9 parts of TiO2 template spheres, 30 parts of ultrapure water, 6.2 parts of methanol solution, and 8.2 parts of ethanol solution are mixed and stirred for 20 min, then 13 parts of chloroauric acid solution (1 g / 10 ml concentration) and 13 parts of bis(chloroauric acid(I))bis(diphenylphosphine)methane are added and stirred for 20 min. After stirring, the mixture is irradiated under 300 W ultraviolet light for 10 days, centrifuged to precipitate, and the precipitate is washed three times with ethanol and deionized water to obtain the final product.

[0129] Specifically, the diameter of the gold nanoparticles is 350~400nm, and the diameter of the opening of the gold nanoparticles is 100~300nm.

[0130] The preparation method of magnetic Fe3O4 nanoparticles is a prior art. The preparation method of magnetic Fe3O4 nanoparticles adopts the preparation method described in Example 1 of the prior art publication number CN101269845B. The size of the magnetic Fe3O4 nanoparticles prepared is less than 100 nm.

[0131] The preparation of the magnetic gold nanoparticles includes the following steps:

[0132] First, dried magnetic Fe3O4 nanoparticles were acid-washed and dispersed in 2-pyrrolidone, then sonicated for 30 min to form dispersion A, with a concentration of 1 mg / mL. Then, gold nanoparticles were dispersed in 0.1 M PVP ethanol solution, sonicated for 20 min, and then centrifuged and washed three times. Finally, the precipitate was redispersed in 2-pyrrolidone to form dispersion B, with a concentration of 5 mg / mL. Dispersion A and dispersion B were mixed to form a mixture with a volume ratio of 2:1. The mixture was sonicated for 30 min, then placed in a 40℃ water bath and stirred for 10 h. Finally, the magnetic Fe3O4 nanoparticles that did not enter the mixture were separated by centrifugation.

[0133] Specifically, the mass ratio of the polyurethane prepolymer, curing agent, and functional filler is 100:18:6, wherein the functional filler is nano-alumina and magnetic gold nanoparticles.

[0134] Specifically, the mass ratio of the nano-alumina to the gold nanoparticles is 1:1.5.

[0135] Specifically, the alumina nanoparticles have a particle size of 10–20 nm.

[0136] In this embodiment, the curing agent includes 4,4'-diamino-3,3'-dichlorodiphenylmethane, polyether polyamine D3000, and tetrafunctional polyether amine T5000.

[0137] More specifically, in this embodiment, the curing agent comprises 25 parts by weight of 4,4'-diamino-3,3'-dichlorodiphenylmethane, 5 parts by weight of polyether polyamine D3000, and 1 part by weight of tetrafunctional polyether amine T5000.

[0138] The method for preparing the polished layer includes the following steps:

[0139] Polyisocyanates and polyols react to form polyurethane prepolymers;

[0140] The curing agent, nano-alumina, and polyethylene glycol-grafted modified gold nanoparticles were added to the polyurethane prepolymer and mixed thoroughly.

[0141] After being poured into the mold and cured, the mixture is cooled to room temperature and then demolded to obtain a polished layer.

[0142] Specifically, the curing time is 16 hours and the curing temperature is 80°C.

[0143] Specifically, in this embodiment, the polyisocyanate is a diisocyanate; the polyol is a polycarbonate polyol. The polycarbonate polyol is a polycarbonate diol with a functionality of 2.

[0144] Since the reaction of polyisocyanates and polyols to generate polyurethane prepolymers is an existing technology, it will not be described in detail here. For details, please refer to the preparation method of polyurethane prepolymer in Example 1 of the prior art patent application number CN201610391966.1.

[0145] When using the chemical mechanical polishing process described in this invention to perform fine polishing on Teos Wafer (silicon dioxide deposited silicon wafer), the first electrically controlled permanent magnet assembly 61 applies a load of 1.1 psi to the workpiece 1 to be polished, the rotation speed of the workpiece 1 is 120 rpm, and the rotation speed of the magnetic polishing pad 2 is 115 rpm. The rotation speed of the workpiece 1 to be polished is 5 rpm higher than that of the magnetic polishing pad 2 to reduce the eddy current effect and improve uniformity. The polishing slurry is Anji-D3000, and the flow rate of the polishing slurry is 200 mL / min to ensure that the chemical etching rate matches the mechanical removal rate. The polishing time is 90 s / piece to avoid edge chamfering caused by over-polishing.

[0146] Example 2

[0147] In this embodiment, unlike in embodiment 1,

[0148] The functional filler consists of nano-alumina and magnetic gold nanoparticles grafted with polyethylene glycol.

[0149] Specifically, the mass ratio of the nano-alumina to the magnetic gold nanoparticles grafted with polyethylene glycol is 1:1.5.

[0150] Grafting polyethylene glycol onto magnetic gold nanoparticles includes the following steps:

[0151] T1. Plasma cleaning of magnetic gold nanoparticles: The magnetic gold nanoparticles were cleaned using an oxygen plasma cleaner with a power of 70W for 8 minutes and an oxygen flow rate of 20 sccm.

[0152] T2. Grafted polyethylene glycol: First, the plasma-treated magnetic gold nanoparticles are dispersed in water to form reaction solution A, with a concentration of 1 mg / mL, and ultrasonically dispersed for 30 min. Then, mercapto-terminated polyethylene glycol (HS-PEG-OH) is dissolved in anhydrous ethanol to form reaction solution B, with a concentration of 0.8 mg / mL. Reaction solution B is added to reaction solution A, and the reaction temperature is room temperature with a stirring time of 40 min. The supernatant is removed by centrifugation, and then washed with anhydrous ethanol. The centrifugation is repeated 3 times before drying.

[0153] Example 3

[0154] In this embodiment, unlike in embodiment 2,

[0155] The preparation of the magnetic gold nanoparticles includes the following steps:

[0156] First, dried magnetic Fe3O4 nanoparticles were acid-washed and dispersed in 2-pyrrolidone, then sonicated for 30 min to form dispersion A, with a concentration of 1 mg / mL. Then, gold nanoparticles were dispersed in 0.1 M PVP ethanol solution, sonicated for 25 min, and then centrifuged and washed three times. Finally, the precipitate was redispersed in 2-pyrrolidone to form dispersion B, with a concentration of 5 mg / mL. Dispersion A and dispersion B were mixed to form a mixture with a volume ratio of 2:1. The mixture was sonicated for 30 min, then placed in a 50℃ water bath and stirred for 12 h. Finally, the magnetic Fe3O4 nanoparticles that did not enter the mixture were separated by centrifugation.

[0157] Specifically, the mass ratio of the polyurethane prepolymer, curing agent, and functional filler is 100:25:8.

[0158] The mass ratio of the nano-alumina to the magnetic gold nanoparticles grafted with polyethylene glycol is 1:2.

[0159] Grafting polyethylene glycol onto magnetic gold nanoparticles includes the following steps:

[0160] T1. Plasma cleaning of magnetic gold nanoparticles: The magnetic gold nanoparticles were cleaned using an oxygen plasma cleaner with a power of 82W for 4 minutes and an oxygen flow rate of 30 sccm.

[0161] T2. Grafted polyethylene glycol: First, the plasma-treated magnetic gold nanoparticles are dispersed in water to form reaction solution A, with a concentration of 1 mg / mL, and ultrasonically dispersed for 30 min. Then, thiol-terminated polyethylene glycol (HS-PEG-OH) is dissolved in anhydrous ethanol to form reaction solution B, with a concentration of 1 mg / mL. Reaction solution B is added to reaction solution A, and the reaction temperature is room temperature with a stirring time of 30 min. The supernatant is removed by centrifugation, and then the mixture is washed with anhydrous ethanol. After repeating the centrifugation three times, the mixture is dried.

[0162] Specifically, the curing time is 20 hours and the curing temperature is 70°C.

[0163] Example 4

[0164] In this embodiment, unlike in embodiment 2,

[0165] The preparation of the magnetic gold nanoparticles includes the following steps:

[0166] First, dried magnetic Fe3O4 nanoparticles were acid-washed and dispersed in 2-pyrrolidone, then sonicated for 30 min to form dispersion A, with a concentration of 1 mg / mL. Then, gold nanoparticles were dispersed in 0.1 M PVP ethanol solution, sonicated for 30 min, and then centrifuged and washed three times. Finally, the precipitate was redispersed in 2-pyrrolidone to form dispersion B, with a concentration of 5 mg / mL. Dispersion A and dispersion B were mixed to form a mixture with a volume ratio of 2:1. The mixture was sonicated for 30 min, then placed in a 45℃ water bath and stirred for 11 h. Finally, the magnetic Fe3O4 nanoparticles that did not enter the mixture were separated by centrifugation.

[0167] Specifically, the mass ratio of the polyurethane prepolymer, curing agent, and functional filler is 100:10:5.

[0168] The mass ratio of the nano-alumina to the magnetic gold nanoparticles grafted with polyethylene glycol is 1:1.

[0169] Grafting polyethylene glycol onto magnetic gold nanoparticles includes the following steps:

[0170] T1. Plasma cleaning of magnetic gold nanoparticles: The magnetic gold nanoparticles were cleaned using an oxygen plasma cleaner with a power of 90W for 7 minutes and an oxygen flow rate of 40 sccm.

[0171] T2. Grafted polyethylene glycol: First, the plasma-treated magnetic gold nanoparticles are dispersed in water to form reaction solution A, with a concentration of 1 mg / mL, and ultrasonically dispersed for 30 min. Then, mercapto-terminated polyethylene glycol (HS-PEG-OH) is dissolved in anhydrous ethanol to form reaction solution B, with a concentration of 0.6 mg / mL. Reaction solution B is added to reaction solution A, and the reaction temperature is room temperature with a stirring time of 60 min. The supernatant is removed by centrifugation, and then washed with anhydrous ethanol. The centrifugation is repeated 3 times before drying.

[0172] Comparative Example 1

[0173] In this comparative example, unlike Example 2,

[0174] The functional filler uses only nano-alumina.

[0175] Comparative Example 2

[0176] In this comparative example, unlike Example 2,

[0177] The functional filler uses only magnetic gold nanoparticles grafted with polyethylene glycol.

[0178] Comparative Example 3

[0179] In this comparative example, unlike Example 2, the polished layer was prepared using the preparation method described in Example 1 of application number CN201610391966.1.

[0180] Performance testing

[0181] The polishing processes and equipment used in Examples 1-4 and Comparative Examples 1-3 were applied to fine polish Teos wafers. The removal rate, wafer surface temperature after polishing, non-uniformity after polishing, and surface roughness were measured. The results are shown in Table 1. The removal rate was calculated as an average value based on the removal rate recorded during the polishing process using a four-probe film thickness gauge (KLA Filmetrics R50). The non-uniformity of the polishing pads obtained in each example and comparative example of this application after polishing the wafer was calculated using the non-uniformity calculation method for testing wafer removal amount in prior art document CN115958526A.

[0182] The polishing pads prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to hardness, porosity, and service life tests; the specific results are shown in Table 1. The hardness of the polishing pads was tested according to GB / T531.1-2008; the porosity of the polishing pads was determined by mercury porosimetry according to GB / T21650.1-2008.

[0183] Table 1 Polishing performance of Examples 1-4 and Comparative Examples 1-3

[0184]

[0185] As shown in Table 1, when polishing wafers using the polishing processes described in Examples 1-4 of this invention, not only is effective heat dissipation achieved, ensuring uniform heat dissipation across all parts of the polishing pad and resulting in a lower wafer surface polishing temperature of 62-65°C, but the polishing uniformity is also improved. Furthermore, the polishing pads prepared using Examples 1-4 of this invention achieve both high porosity and high hardness, with a porosity of 68.9-72.5% and a hardness of 61-67D, significantly improving the polishing removal rate. Simultaneously, the polishing pads prepared using Examples 1-4 of this invention can extend their service life to 59-69 hours, thus providing long-term stable polishing performance.

[0186] As shown in Table 1, after fine polishing of TeosWafer (silicon dioxide deposited silicon wafer) using the polishing processes described in Examples 2-4 of this invention, the surface roughness Ra value of the wafer is <0.30 nm. Experimental results demonstrate that the chemical mechanical polishing process described in this invention can stably achieve high-quality fine polishing of Teos Wafer, meeting the stringent requirements for wafer surface flatness in the semiconductor manufacturing field.

[0187] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A chemical mechanical polishing process, characterized in that, The polishing process includes the following steps: S1. Install a magnetic polishing pad (2) on a polishing rotary disk (3), wherein the magnetic polishing pad (2) contains magnetic gold nanoparticles; S2. The polishing area includes a first area (71) and a second area (72), and the workpiece (1) to be polished is clamped in the first area (71); S3. Start the rotating disk (3) and input polishing liquid into the magnetic polishing pad (2) through the polishing liquid release device (5); S4. Start the magnetic field control system, control the first electrically controlled permanent magnet component (61) in the first region (71) to demagnetize, control the second electrically controlled permanent magnet component (62) in the second region (72) to magnetize, and control the first electrically controlled permanent magnet component (61) to apply a certain load to the workpiece (1) to be polished for polishing. The magnetic polishing pad (2) includes a magnetic polishing layer, a buffer layer and a transparent base pad from top to bottom. The magnetic polishing layer includes a polyurethane prepolymer, a curing agent and a functional filler. The mass ratio of the polyurethane prepolymer, the curing agent and the functional filler is 100:(10~25):(5~8). The functional filler includes magnetic gold nanoparticles grafted with polyethylene glycol and nano-alumina. Grafting polyethylene glycol onto magnetic gold nanoparticles includes the following steps: T1. Plasma cleaning of magnetic gold nanoparticles: Use an oxygen plasma cleaner to clean the magnetic gold nanoparticles. The power is 70~90W, the time is 4~8min, and the oxygen flow rate is 20~40sccm. T2. Grafted polyethylene glycol: First, the plasma-treated magnetic gold nanoparticles are dispersed in water to form reaction solution A, with a concentration of 1 mg / mL, and ultrasonically dispersed for 30 min. Then, the mercapto-terminated polyethylene glycol is dissolved in anhydrous ethanol to form reaction solution B, with a concentration of 0.6~1 mg / mL. Reaction solution B is added to reaction solution A, and the reaction temperature is room temperature with a stirring time of 30~60 min. The supernatant is removed by centrifugation, and then the mixture is washed with anhydrous ethanol. After repeating centrifugation 3 times, the mixture is dried.

2. The chemical mechanical polishing process according to claim 1, characterized in that, The polishing liquid release device (5) is located at the center above the rotating disk (3).

3. The chemical mechanical polishing process according to claim 1, characterized in that, The central axis of the workpiece (1) to be polished is set at the center of the first region (71).

4. The chemical mechanical polishing process according to claim 1, characterized in that, The workpiece (1) to be polished is clamped in the fixture.

5. The chemical mechanical polishing process according to claim 1, characterized in that, The buffer layer is bonded to the magnetic polishing layer and the transparent base pad with pressure-sensitive adhesive.

6. The chemical mechanical polishing process according to claim 1, characterized in that, The preparation of the magnetic gold nanoparticles includes the following steps: Dry magnetic Fe3O4 nanoparticles were acid-washed and dispersed in 2-pyrrolidone, then sonicated for 30 min to form dispersion A, with a concentration of 1 mg / mL. Gold nanoparticles were dispersed in 0.1 M PVP ethanol solution, sonicated for 10-20 min, then centrifuged and washed three times. The precipitate was then redispersed in 2-pyrrolidone to form dispersion B, with a concentration of 5 mg / mL. Dispersion A and dispersion B were mixed to form a mixture with a volume ratio of 2:

1. The mixture was sonicated for 30 min, then placed in a water bath at 40-50℃ and stirred for 10-12 h. Finally, the magnetic Fe3O4 nanoparticles that did not penetrate the mixture were separated by centrifugation.

7. The chemical mechanical polishing process according to claim 6, characterized in that, The gold nanoparticles have a hollow internal structure with openings, and the diameter of the gold nanoparticles is 350~400nm, while the diameter of the openings in the gold nanoparticles is 100~300nm.

8. The chemical mechanical polishing process according to claim 6, characterized in that, The magnetic Fe3O4 nanoparticles have a size of less than 100 nm.

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