A polishing layer of a chemical mechanical polishing polishing pad and a method of manufacturing the same

Abstract

The present application relates to the technical fields of chemical mechanical polishing pad, and provides a polishing layer of a chemical mechanical polishing pad and a preparation method thereof.The polishing layer comprises polyurethane prepolymer, curing agent and functional filler, and the mixing mass ratio of the three is 100:(10-25):(4-9), wherein the functional filler comprises nano-alumina and gold nanoparticles grafted with polyethylene glycol.The polishing layer of the chemical mechanical polishing pad has the synergistic effect of nano-alumina and gold nanoparticles grafted with polyethylene glycol, realizes the precise balance between porosity and mechanical properties, ensures high porosity of the polishing layer, improves the surface strength and hardness of the polishing pad, and improves the wear resistance of the polishing layer;in the polishing process, the polishing pad is not prone to deformation, and the polishing removal rate of the polishing pad is also improved.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing pad technology, and more specifically, to a polishing layer of a chemical mechanical polishing pad and its preparation method. 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 porosity of the polishing layer results in low surface strength and hardness, 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 flattening, and potentially even deteriorating workpiece flatness. However, in the prior art, excessively low porosity in the polishing layer leads to a high polishing 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 polishing pad, affecting polishing efficiency and the uniformity of material removal from the workpiece surface. Furthermore, low porosity hinders the removal of polishing residues, which may accumulate between the polishing pad and the workpiece surface, further impacting polishing quality.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a polishing layer for a chemical mechanical polishing (CMP) pad and its preparation method, addressing the problems in the prior art where excessively high porosity in the polishing layer reduces the surface strength and hardness of the polishing pad, resulting in 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 flattening effect, and potentially even worsening the workpiece flatness; conversely, excessively low porosity leads to a high polishing pad density, reducing the polishing layer's ability to store and transport polishing fluid, potentially causing uneven distribution of polishing fluid between the workpiece and the polishing pad, affecting polishing efficiency and the uniformity of material removal from the workpiece surface; furthermore, low porosity hinders the removal of polishing residues, which may accumulate between the polishing pad and the workpiece surface, further impacting polishing quality.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0009] A polishing layer for a chemical mechanical polishing pad, the polishing layer comprising 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):(4~9), wherein the functional filler comprises nano-alumina and polyethylene glycol grafted modified gold nanoparticles.

[0010] Furthermore, the mass ratio of the nano-alumina to the polyethylene glycol-grafted gold nanoparticles is 1:1~2.

[0011] Furthermore, the alumina nanoparticles have a particle size of 10–20 nm.

[0012] Furthermore, the preparation of the polyethylene glycol grafted modified gold nanoparticles includes the following steps:

[0013] (1) Plasma cleaning of gold nanoparticles: Gold nanoparticles were cleaned using an oxygen plasma cleaner with a power of 70~90W and a time of 4~8min, and an oxygen flow rate of 20~40sccm.

[0014] (2) Grafting polyethylene glycol: First, the plasma-treated gold nanoparticles are dispersed in water to form reaction solution A, with a concentration of 1 mg / mL. The mixture is 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 0.6~1 mg / mL. The reaction solution is added to reaction solution A. The reaction temperature is room temperature, and the stirring time is 30~60 min. The supernatant is removed by centrifugation. Then, the polyethylene glycol-grafted gold nanoparticles are rinsed with anhydrous ethanol. After centrifugation three times, the mixture is dried for later use.

[0015] Furthermore, the gold nanoparticles have a hollow structure and contain openings, the diameter of the gold nanoparticles is 350~400nm, and the diameter of the openings of the gold nanoparticles is 100~300nm.

[0016] Furthermore, the molecular weight of the thiol-terminated polyethylene glycol is 2000-3000.

[0017] Furthermore, the curing agent comprises 4,4'-diamino-3,3'-dichlorodiphenylmethane, polyether polyamine D3000, and tetrafunctional polyether amine T5000.

[0018] A second aspect of the present invention provides a method for preparing a polishing layer of a chemical mechanical polishing pad, the method comprising the following steps:

[0019] Polyisocyanates and polyols react to form polyurethane prepolymers;

[0020] The curing agent, nano-alumina, and polyethylene glycol-grafted modified gold nanoparticles were added to the polyurethane prepolymer and mixed thoroughly.

[0021] The mixture is poured into a mold, cured, and then cooled to room temperature before being demolded to obtain a polished layer.

[0022] Furthermore, the curing time is 16~20h, and the curing temperature is 70~80℃.

[0023] Furthermore, the polyisocyanate is diphenylmethane diisocyanate, and the polyol is polycarbonate polyol.

[0024] Compared with the prior art, the polishing layer of the polishing pad for chemical mechanical polishing and its preparation method described in this invention have the following beneficial effects:

[0025] The present invention discloses a polishing layer for a chemical mechanical polishing (CMP) pad and its preparation method. By optimizing the mixing mass ratio of polyurethane prepolymer, curing agent, and functional filler, and by designing a composite filler using nano-alumina and polyethylene glycol-grafted modified gold nanoparticles, the synergistic effect of nano-alumina and polyethylene glycol-grafted modified gold nanoparticles achieves bilevel pore structure regulation. This ensures high porosity of the polishing layer while improving its surface strength and hardness, thus enhancing its wear resistance. It overcomes the limitation of a single filler not being able to simultaneously achieve both hardness and porosity, achieving an optimal balance among porosity, mechanical strength, and polishing removal rate. Detailed Implementation

[0026] 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.

[0027] 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. 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.

[0028] 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.

[0029] 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.

[0030] The present invention will now be described in detail with reference to embodiments.

[0031] In existing technologies, excessively high porosity in the polishing layer reduces the surface strength and hardness of the polishing pad, resulting in 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 flattening, and potentially even deteriorating workpiece flatness. Conversely, excessively low porosity leads to a high polishing pad density, reducing the polishing layer's ability to store and transport polishing fluid. This can result in uneven distribution of the polishing fluid between the workpiece and the polishing pad, affecting polishing efficiency and the uniformity of material removal from the workpiece surface. Furthermore, low porosity hinders the removal of polishing residues, which may accumulate between the polishing pad and the workpiece surface, further impacting polishing quality.

[0032] To address the aforementioned technical issues, the applicant proposed incorporating gold nanoparticles as fillers into the polishing layer.

[0033] 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 internal structure and contain openings.

[0034] 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.

[0035] 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.

[0036] Although incorporating gold nanoparticles as fillers into the polishing layer has the following advantages:

[0037] I. Increase porosity.

[0038] 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.

[0039] 3. Improve wear resistance: The high hardness of gold materials can significantly improve the wear resistance of the polished layer.

[0040] 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.

[0041] V. The high thermal conductivity of gold nanomaterials 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 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.

[0042] VI. Gold nanoparticles can improve the antibacterial properties of polishing pads, thereby improving their durability and extending their service life.

[0043] However, through specific experiments, the applicant discovered the following drawbacks when using gold nanoparticles as a filler: 1. Gold nanoparticles have a high specific surface area and surface energy, making them prone to aggregation 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 gold nanoparticles and the polymer matrix is ​​weak, making them prone to detachment during polishing, forming micro-pits or scratches, thus affecting polishing quality.

[0044] To address the aforementioned technical issues, the applicant proposed modifying gold nanoparticles by grafting them with polyethylene glycol.

[0045] Specifically, the preparation of the polyethylene glycol-grafted modified gold nanoparticles includes the following steps:

[0046] (1) Plasma cleaning of gold nanoparticles: Gold nanoparticles were cleaned using an oxygen plasma cleaner with a power of 70~90W and a time of 4~8min, and an oxygen flow rate of 20~40sccm.

[0047] Plasma cleaning serves multiple purposes: First, it can thoroughly remove organic contaminants from the surface of gold nanoparticles; second, it can introduce oxygen-containing polar groups into the gold nanoparticles, improving their hydrophilicity and reactivity, reducing the contact angle from 60-80° before cleaning to below 10°, thereby improving the dispersion of gold nanoparticles and enabling better grafting with polyethylene glycol; third, it helps functional fillers form excellent dispersions in polyurethane prepolymer systems, better fulfilling the functions of the fillers.

[0048] 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 gold nanoparticles.

[0049] (2) Grafting polyethylene glycol: First, the plasma-treated gold nanoparticles are dispersed in water to form reaction solution A, with a concentration of 1 mg / mL. The mixture is 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 0.6~1 mg / mL. The reaction solution is added to reaction solution A. The reaction temperature is room temperature, and the stirring time is 30~60 min. The thiol-gold reaction is rapid, and too long a reaction time may cause PEG chain entanglement. The supernatant is removed by centrifugation. Then, the polyethylene glycol-grafted gold nanoparticles are rinsed with anhydrous ethanol. After centrifugation three times, the mixture is dried for later use.

[0050] 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 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.

[0051] The concentrations, reaction temperatures, and stirring times of reaction solutions A and B are set to ensure the successful preparation of polyethylene glycol-grafted modified gold nanoparticles while avoiding high grafting efficiency, thus preventing the formation of a dense hydrophilic layer on the outside of the gold nanoparticles.

[0052] Specifically, the molecular weight of mercapto-terminated polyethylene glycol is 2000-3000.

[0053] Specific experiments revealed the following: 1. Polyethylene glycol-grafted gold nanoparticles are uniformly dispersed in the polishing layer matrix, are less prone to aggregation, and thus improve polishing uniformity. 2. The interfacial interaction between the polyethylene glycol-grafted gold nanoparticles and the polymer matrix is ​​strong, making them less likely to detach during polishing and thus avoiding affecting polishing quality.

[0054] In order to further improve the porosity, surface strength and hardness of the polished layer, enhance its wear resistance and polishing removal rate, and reduce costs, the applicant designed the functional filler as a composite filler of nano-alumina and polyethylene glycol-grafted modified gold nanoparticles.

[0055] Specifically, the mass ratio of the polyurethane prepolymer, curing agent, and functional filler is 100:(10~25):(4~9), wherein the functional filler is nano-alumina and polyethylene glycol grafted modified gold nanoparticles. The functional filler accounts for 4~9% of the total composition. Too much filler will lead to a decrease in material hardness and insufficient system support, while too little filler will lead to a decrease in the material's ability to retain polishing liquid and a decrease in polishing removal efficiency.

[0056] Specifically, the mass ratio of the nano-alumina to the polyethylene glycol-grafted gold nanoparticles is 1:1~2.

[0057] The mass ratio of nano-alumina to gold nanoparticles is 1:1~2, which reduces costs while achieving excellent performance of functional fillers.

[0058] Specifically, the alumina nanoparticles have a particle size of 10–20 nm.

[0059] Nanoscale particle size (typically <100 nm) can reduce surface scratches and improve the surface planarization of workpieces.

[0060] Specifically, the curing agent includes 4,4'-diamino-3,3'-dichlorodiphenylmethane, polyether polyamine D3000, and tetrafunctional polyether amine T5000.

[0061] The curing agent is designed to lower the curing temperature, prevent the decomposition of polyethylene glycol in the polyethylene glycol-grafted gold nanoparticles, and ensure the integrity of the filler function.

[0062] 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 polyethylene glycol grafted gold nanoparticles:

[0063] 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 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, solving 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. Polyethylene glycol grafted modified gold nanoparticles, on the one hand, gold itself has the characteristic of high modulus, and adding gold nanoparticles as fillers can significantly improve the hardness and wear resistance of the polishing layer, thereby improving wear resistance; on the other hand, gold nanoparticles can be covalently bonded to the matrix through PEG grafting, suppressing interfacial stress concentration and greatly reducing the deformation rate of the polishing pad.

[0064] II. Polyethylene glycol (PEG) grafted 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, preventing 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 PEG-grafted 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.

[0065] Third, nano-alumina can also act as a catalyst. The surface hydroxyl groups (-OH) 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.

[0066] 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.

[0067] Fifth, the high thermal conductivity of 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 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.

[0068] VI. Polyethylene glycol grafted modified gold nanoparticles are uniformly dispersed in the polishing layer matrix, are not prone to agglomeration, and improve polishing uniformity.

[0069] VII. Polyethylene glycol (PEG) grafting modification enhances the interfacial interaction between gold nanoparticles and the polyurethane matrix through covalent bonding, greatly reducing the filler shedding rate and avoiding the generation of micro-pits or scratches.

[0070] 8. The addition of polyethylene glycol (PEG)-grafted gold nanoparticles can improve the problem of nano-alumina agglomeration: The hydrophilic long chains of PEG-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," directly alleviating the direct contact between rigid nano-alumina particles and improving the dispersibility of nano-alumina; on the other hand, the PEG-grafted layer can form a hydrophilic crown on the surface of the gold nanoparticle container, preventing the agglomeration of nano-alumina through steric hindrance, while maintaining the suspension stability of the composite filler in the polishing solution, indirectly affecting the synergistic effect of the two.

[0071] The applicant also proposes a method for preparing a polishing layer of a chemical mechanical polishing (CMP) pad, wherein the method for preparing the polishing layer comprises the following steps:

[0072] Polyisocyanates and polyols react to form polyurethane prepolymers;

[0073] The curing agent, nano-alumina, and polyethylene glycol-grafted modified gold nanoparticles were added to the polyurethane prepolymer and mixed thoroughly.

[0074] After being poured into the mold and cured, the mixture is cooled to room temperature and then demolded to obtain a polished layer.

[0075] Specifically, the curing time is 16-20 hours and the curing temperature is 70-80℃.

[0076] Specifically, the polyisocyanate is diphenylmethane diisocyanate, and the polyol is polycarbonate polyol.

[0077] Example 1

[0078] 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.

[0079] Specifically, the diameter of the gold nanoparticles is 350~400nm, and the diameter of the opening of the gold nanoparticles is 100~300nm.

[0080] Specifically, the preparation of the polyethylene glycol-grafted modified gold nanoparticles includes the following steps:

[0081] (1) Plasma cleaning of gold nanoparticles: Gold nanoparticles were cleaned using an oxygen plasma cleaner with a power of 70W and a time of 8min and an oxygen flow rate of 40sccm.

[0082] (2) Grafting polyethylene glycol: First, the plasma-treated gold nanoparticles were dispersed in water to form reaction solution A, with a concentration of 1 mg / mL. The mixture was ultrasonically dispersed for 30 min. Then, the mercapto-terminated polyethylene glycol (HS-PEG-OH) was dissolved in anhydrous ethanol to form reaction solution B, with a concentration of 0.6 mg / mL. The reaction solution was added to reaction solution A. The reaction temperature was room temperature, and the stirring time was 30 min. The supernatant was removed by centrifugation. Then, the polyethylene glycol-grafted gold nanoparticles were rinsed with anhydrous ethanol. The mixture was centrifuged three times and then dried for later use.

[0083] Specifically, the molecular weight of mercapto-terminated polyethylene glycol is 2000-3000.

[0084] Specifically, the mass ratio of the polyurethane prepolymer, curing agent, and functional filler is 100:17:6, wherein the functional filler is nano-alumina and polyethylene glycol grafted modified gold nanoparticles.

[0085] Specifically, the mass ratio of the nano-alumina to the polyethylene glycol-grafted gold nanoparticles is 1:1.5.

[0086] Specifically, the alumina nanoparticles have a particle size of 10–20 nm.

[0087] In this embodiment, the curing agent includes 4,4'-diamino-3,3'-dichlorodiphenylmethane, polyether polyamine D3000, and tetrafunctional polyether amine T5000.

[0088] 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.

[0089] The applicant also proposes a method for preparing a polishing layer of a chemical mechanical polishing (CMP) pad, wherein the method for preparing the polishing layer comprises the following steps:

[0090] Polyisocyanates and polyols react to form polyurethane prepolymers;

[0091] The curing agent, nano-alumina, and polyethylene glycol-grafted modified gold nanoparticles were added to the polyurethane prepolymer and mixed thoroughly.

[0092] After being poured into the mold and cured, the mixture is cooled to room temperature and then demolded to obtain a polished layer.

[0093] Specifically, the curing time is 16 hours and the curing temperature is 80°C.

[0094] 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.

[0095] 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.

[0096] Example 2

[0097] In this embodiment, unlike in Embodiment 1,

[0098] Specifically, the preparation of the polyethylene glycol-grafted modified gold nanoparticles includes the following steps:

[0099] (1) Plasma cleaning of gold nanoparticles: Gold nanoparticles were cleaned using an oxygen plasma cleaner with a power of 80W and a time of 6min and an oxygen flow rate of 30sccm.

[0100] (2) Grafting polyethylene glycol: First, the plasma-treated gold nanoparticles were 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 (HS-PEG-OH) was dissolved in anhydrous ethanol to form reaction solution B, with a concentration of 0.8 mg / mL; the reaction solution was added to reaction solution A, the reaction temperature was room temperature, and the stirring time was 60 min; the supernatant was removed by centrifugation, and then the polyethylene glycol grafted modified gold nanoparticles were rinsed with anhydrous ethanol, centrifuged 3 times, and then dried for later use.

[0101] Specifically, the mass ratio of the polyurethane prepolymer, curing agent, and functional filler is 100:25:9.

[0102] The mass ratio of the nano-alumina to the polyethylene glycol-grafted gold nanoparticles is 1:2.

[0103] Specifically, the curing time is 20 hours and the curing temperature is 70°C.

[0104] Example 3

[0105] In this embodiment, unlike in Embodiment 1,

[0106] Specifically, the preparation of the polyethylene glycol-grafted modified gold nanoparticles includes the following steps:

[0107] (1) Plasma cleaning of gold nanoparticles: Gold nanoparticles were cleaned using an oxygen plasma cleaner with a power of 90W and a time of 4min and an oxygen flow rate of 20sccm.

[0108] (2) Grafting polyethylene glycol: First, the plasma-treated gold nanoparticles were dispersed in water to form reaction solution A, with a concentration of 1 mg / mL. The mixture was ultrasonically dispersed for 30 min. Then, the mercapto-terminated polyethylene glycol (HS-PEG-OH) was dissolved in anhydrous ethanol to form reaction solution B, with a concentration of 1 mg / mL. The reaction solution was added to reaction solution A, and the reaction temperature was room temperature. The stirring time was 50 min. The supernatant was removed by centrifugation. Then, the polyethylene glycol-grafted gold nanoparticles were rinsed with anhydrous ethanol. After centrifugation was repeated 3 times, the mixture was dried for later use.

[0109] Specifically, the mass ratio of the polyurethane prepolymer, curing agent, and functional filler is 100:10:4.

[0110] The mass ratio of the nano-alumina to the polyethylene glycol-grafted gold nanoparticles is 1:1.

[0111] Specifically, the curing time is 18 hours and the curing temperature is 60°C.

[0112] Comparative Example 1

[0113] In this comparative example, unlike Example 1,

[0114] The functional filler uses only nano-alumina.

[0115] Comparative Example 2

[0116] In this comparative example, unlike Example 1,

[0117] The functional filler uses only polyethylene glycol-grafted modified gold nanoparticles.

[0118] Comparative Example 3

[0119] The polished layer was prepared using the preparation method described in Example 1 of application number CN201610391966.1.

[0120] Performance testing

[0121] The polishing layers prepared in Examples 1-3 and Comparative Examples 1-3 were processed into groove structures using a grooving machine, and then bonded to a buffer layer and a transparent base pad to obtain a polishing pad. The layers were bonded together with pressure-sensitive adhesive. The raw materials and preparation methods of the buffer layer and the transparent base pad are the same as those in the prior art and will not be described in detail here.

[0122] The polishing pads prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to hardness and porosity tests.

[0123] The hardness of the prepared polishing pads was tested according to GB / T531.1-2008; the porosity of the polishing pads was determined by mercury intrusion porosimetry according to GB / T21650.1-2008.

[0124] The polishing pads prepared in Examples 1-3 and Comparative Examples 1-3 were used to polish wafers. Performance tests were conducted on the polishing pads. A 30-inch polishing pad sample was attached to a CMP (Chemical Mechanical Polishing) machine. The polishing fluid was Anji-D3000 with a flow rate of 300 cc / min. The CMP machine was a Universal-300B with a pressure of 1.3 psi, a grinding head speed of 85 rpm, a grinding disc speed of 80 rpm, and a polishing time of 90 s / wafer. The wafers were 12-inch Teos wafers. The polishing temperature, polishing removal rate, surface scratches, and polishing pad wear were measured on the wafer surface. Surface scratches were observed using atomic force microscopy. The results are shown in Table 1.

[0125] The removal rate is an average value calculated by recording the removal rate during the polishing process using a four-probe film thickness gauge (KLA Filmetrics R50).

[0126] The polishing pads prepared in Examples 1-3 and Comparative Examples 1-3 were used to polish wafers. Their ultimate service life was tested by long-term cutting of the dressing pad, which is the time required to cut all the grooves with the same parameters. The specific results are shown in Table 1.

[0127] Table 1. Performance of the polishing pads prepared in Examples 1-3 and Comparative Examples 1-2

[0128] Hardness (Shore D) Porosity (%) Polishing removal rate Polishing pad wear Wafer surface scratch conditions Wafer surface polishing temperature (°C) Service life (h) Example 1 64 72.2 1431 Less wear Very few scratches 71 57 Example 2 65 71.4 1425 Less wear Very few scratches 70 60 Example 3 66 70.7 1436 Less wear Very few scratches 72 56 Comparative Example 1 57 48.2 1108 Significant wear There are many scratches 77 42 Comparative Example 2 54 50.6 1224 Significant wear There are many scratches 75 39 Comparative Example 3 48 52.3 1002 Significant wear and tear Many scratches 82 31

[0129] As shown in Table 1, the polishing pads prepared in Examples 1-3 of this invention achieve both high porosity and high hardness when polishing wafers. The porosity is 70.7-72.2%, and the hardness is 64-66D. This significantly improves the polishing removal rate and the wear resistance of the polishing pads, resulting in less wear and fewer scratches on the wafer surface, which also contributes to improved wafer surface polishing quality. The wafer surface polishing temperature is relatively low, at 70-72℃. This is because the high thermal conductivity of gold nanomaterials in the polishing pads increases their thermal conductivity, thereby improving heat dissipation and reducing the wafer polishing temperature. Simultaneously, the polishing pads prepared in Examples 1-3 of this invention can extend their service life to 56-60 hours, thus providing long-term stable polishing performance.

[0130] 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 polishing layer of a polishing pad for chemical mechanical polishing, characterized in that, The 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):(4~9). The functional filler includes nano-alumina and polyethylene glycol-grafted modified gold nanoparticles.

2. The polishing layer of a chemical mechanical polishing pad according to claim 1, characterized in that, The mass ratio of the nano-alumina and polyethylene glycol-grafted gold nanoparticles is 1:1~2.

3. The polishing layer of a chemical mechanical polishing pad according to claim 2, characterized in that, The particle size of the nano-alumina particles is 10–20 nm.

4. The polishing layer of a polishing pad for chemical mechanical polishing according to claim 2, characterized in that, The preparation of the polyethylene glycol grafted gold nanoparticles includes the following steps: (1) Plasma cleaning of gold nanoparticles: Gold nanoparticles were cleaned using an oxygen plasma cleaner with a power of 70~90W and a time of 4~8min, and an oxygen flow rate of 20~40sccm. (2) Grafting polyethylene glycol: First, the plasma-treated gold nanoparticles are dispersed in water to form reaction solution A, with a concentration of 1 mg / mL. The mixture is 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 0.6~1 mg / mL. The reaction solution is added to reaction solution A. The reaction temperature is room temperature, and the stirring time is 30~60 min. The supernatant is removed by centrifugation. Then, the polyethylene glycol-grafted gold nanoparticles are rinsed with anhydrous ethanol. After centrifugation three times, the mixture is dried for later use.

5. The polishing layer of a polishing pad for chemical mechanical polishing according to claim 4, 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.

6. The polishing layer of a polishing pad for chemical mechanical polishing according to claim 4, characterized in that, The thiol-terminated polyethylene glycol has a molecular weight of 2000-3000.

7. The polishing layer of a chemical mechanical polishing pad according to claim 4, characterized in that, The curing agent includes 4,4'-diamino-3,3'-dichlorodiphenylmethane, polyether polyamine D3000, and tetrafunctional polyether amine T5000.

8. A method for preparing a polishing layer of a chemical mechanical polishing pad, wherein the method for preparing the polishing layer is used to prepare the polishing layer according to any one of claims 1 to 7, characterized in that, The method for preparing the polished layer includes the following steps: Polyisocyanates and polyols react to form polyurethane prepolymers; The curing agent, nano-alumina, and polyethylene glycol-grafted modified gold nanoparticles were added to the polyurethane prepolymer and mixed thoroughly. After being poured into the mold and cured, the mixture is cooled to room temperature and then demolded to obtain a polished layer.

9. The method for preparing the polishing layer of a polishing pad for chemical mechanical polishing according to claim 8, characterized in that, The curing time is 16~20h, and the curing temperature is 70~80℃.

10. The method for preparing the polishing layer of a polishing pad for chemical mechanical polishing according to claim 8, characterized in that, The polyisocyanate is diphenylmethane diisocyanate, and the polyol is polycarbonate polyol.