Chemical mechanical polishing composition for metal alloys and method of polishing thereof

Abstract

A chemical mechanical polishing composition and method for polishing metal alloys. The composition includes alumina abrasive particles, an oxidizing agent, a dispersing agent, a pH adjuster, wherein the dispersing agent is a nanoclay having a z-average particle size of up to 1000 nm. The composition can be used to polish the surface of a metal alloy substrate with a near neutral pH value, without the risk of corroding metal parts of the polishing equipment.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a chemical mechanical polishing composition and polishing method for metal alloys. Background Technology

[0002] Chemical mechanical polishing (CMP) is a common process for achieving global planarization in integrated circuit manufacturing and other fields. This process primarily aims to obtain a smooth surface that is both flat and free of scratches and impurities. It polishes various target substrates through a combination of chemical and mechanical forces, with the CMP composition playing a crucial role. These compositions are typically aqueous solutions containing a uniformly dispersed array of chemical additives and abrasive grains. CMP compositions, also known as polishing slurries, polishing fluids, or polishing compositions, are commonly used to polish the surfaces of various substrates, such as metals, metal alloys, minerals, and plastics.

[0003] There is a widespread demand for polishing metal and metal alloy substrates. Metal parts in vehicles, ships, aircraft, pipes, light reflectors, containers, handrails, kitchenware, cookware, building metal, and jewelry often require polishing. Ferrous alloy substrates (such as stainless steel with good corrosion resistance) are widely used in machine tools, cookware, structural materials such as surgical instruments, transportation equipment, consumer electronics parts such as smartphone casings and laptop casings, and metal crafts such as car logos. Therefore, there is also a demand for polishing stainless steel surfaces.

[0004] CMP compositions containing alumina abrasive grains are commonly used to polish ferrous alloy materials to obtain a smooth, mirror-like surface. Many metal alloy applications require low surface roughness, high gloss, and a smooth, mirror-like finish, which can be achieved using CMP compositions containing alumina abrasive grains. However, alumina abrasive grains easily create pits, scratches, and other surface defects on the surface of metal alloy substrates. These surface defects can lead to corrosion problems in ferrous metal alloys such as stainless steel due to oxygen deficiency and localized damage to the protective passivation film of stainless steel. Furthermore, these defective areas are susceptible to contamination by dirt and bacteria during daily use. Therefore, there remains a need for CMP compositions containing alumina abrasive grains suitable for polishing metal alloy substrates that can achieve low surface roughness and a low number of surface defects.

[0005] To reduce manufacturing costs, waste, and environmental impact, CMP compositions are typically recycled during the polishing process of metal alloy substrates. For example, a CMP composition is used for polishing, then discharged from the polishing unit and collected in a tank, before being recycled back into the unit for further polishing. Therefore, a long recycling time is necessary for CMP compositions containing alumina abrasive particles. Recycling time refers to the time during which the composition can be reused for chemical mechanical polishing of the substrate without a decline in overall polishing performance (e.g., material removal rate). However, the activity of the CMP composition often decreases over time during recycling, possibly due to wear, breakage, and shrinkage of alumina particles during polishing, or due to chemical changes in the alumina particles. This decreased polishing activity reduces the time the CMP composition can be recycled for polishing, while replacing the CMP composition increases manufacturing costs and environmental burden. Meanwhile, the chemical mechanical polishing compositions currently available on the market for polishing stainless steel are usually acidic, posing a risk of corroding iron and stainless steel components in chemical mechanical polishing equipment. Therefore, there is still a need for CMP compositions containing alumina abrasives that can achieve higher removal rates, longer recycling times, low surface defect numbers, and neutral pH values ​​for polishing metal alloy substrates. Summary of the Invention

[0006] One object of the present invention is to overcome the aforementioned problems existing in the prior art. Specifically, embodiments of the present invention provide a composition suitable for chemical mechanical polishing of the surface of a metal alloy substrate. This composition exhibits high material removal rate and longer recycling time, while achieving low surface roughness and low surface defect number, and has a neutral pH value, eliminating the risk of corrosion to metal components in the polishing equipment.

[0007] Specifically, the chemical mechanical polishing composition of the present invention comprises alumina abrasive particles, an oxidant, a complexing agent, a dispersant, and a pH adjuster, wherein the dispersant is nano-clay having a z-average particle size of up to 1000 nm.

[0008] Preferably, the zeta potential of the nanoclay is at least -5 mV.

[0009] Preferably, the alumina abrasive particles in the composition have a negative zeta potential at a pH of 6 to 7.

[0010] Preferably, the oxidant is an inorganic peroxide, an organic peroxide, or a combination thereof.

[0011] Preferably, the composition further comprises a complexing agent, which is a dicarboxylic acid, a polycarboxylic acid, an amino acid, an organic amine, an aminocarboxylic acid, a polyaminopolycarboxylic acid, a phosphate, a polyphosphate, an organophosphonic acid, a phosphonoylcarboxylic acid, a phenolic derivative, a ketone, or a combination thereof.

[0012] Preferably, the complexing agent is an organophosphonic acid.

[0013] Preferably, the composition contains 0.1 wt% to 33.3 wt% of a complexing agent.

[0014] Preferably, the composition comprises 0.0001 wt% to 15 wt% nano-clay.

[0015] Preferably, the pH adjuster is an alkali metal hydroxide, a quaternary ammonium hydroxide, an alkali metal carbonate, or a combination thereof.

[0016] Another objective of this invention is to provide a polishing method for metal alloy substrates, the method being implemented using the above-described composition.

[0017] The CMP composition provided by this invention not only achieves high material removal rates in the chemical mechanical polishing of metal alloy substrates, but also has a neutral pH value, eliminating the risk of metal equipment corrosion, and enabling longer recycling times, making it environmentally friendly and more economical. Products polished with the CMP composition of this invention exhibit low surface roughness, low surface defect count (scratches and pits), and a satisfactory mirror finish. Detailed Implementation

[0018] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0019] Chemical mechanical polishing compositions typically comprise abrasive grains dispersed in an aqueous carrier. The abrasive grains aid in removing material from the substrate surface during the polishing process. Preferably, the abrasive grains are metal oxide abrasive grains selected from cerium oxide (cerium dioxide), aluminum oxide (alumina), silicon oxide (silicon dioxide), zirconium oxide (zirconia), titanium oxide (titanium dioxide), germanium oxide (germanium oxide), magnesium oxide (magnesium oxide), nickel oxide, gallium oxide (gallium oxide), yttrium oxide (yttrium oxide), and combinations thereof. Preferably, the abrasive grains comprise at least 67 wt%, more preferably at least 74 wt%, more preferably at least 81 wt%, more preferably at least 88 wt%, and most preferably at least 93 wt% of alumina. In a particularly preferred embodiment, the abrasive grains are entirely alumina abrasive grains.

[0020] When used, the composition preferably contains at least 0.02 wt%, more preferably at least 0.24 wt%, more preferably at least 0.63 wt%, more preferably at least 0.82 wt%, and most preferably at least 1.0 wt% of abrasive grains. The term "when used" as used herein refers to the moment the composition is applied to the substrate surface during a chemical mechanical polishing process. If the concentration of abrasive grains is too high, the composition can cause undesirable surface defects during polishing, such as substrate scratches. Therefore, when used, the composition preferably contains at most 40 wt%, more preferably at most 35 wt%, more preferably at most 30 wt%, more preferably at most 25 wt%, and most preferably at most 20 wt% of abrasive grains. In a preferred embodiment, the composition contains from 0.02 wt% to 40 wt%, more preferably from 0.24 wt% to 35 wt%, more preferably from 0.63 wt% to 30 wt%, more preferably from 0.63 wt% to 25 wt%, and most preferably from 1.0 wt% to 20 wt% of abrasive grains.

[0021] As those skilled in the art know, alumina abrasive grains can be fumed alumina or alumina with different crystalline phases, such as α-alumina, β-alumina, γ-alumina, δ-alumina, θ-alumina, σ-alumina, κ-alumina, η-alumina, χ-alumina, p-alumina, and combinations thereof. Preferably, the alumina abrasive grains are selected from α-alumina, β-alumina, γ-alumina, δ-alumina, σ-alumina, θ-alumina, and combinations thereof.

[0022] It has been demonstrated that α-alumina exhibits a higher substrate material removal rate during chemical mechanical polishing compared to alumina abrasives with other crystalline phases. Therefore, the alumina abrasives preferably contain at least 6 wt%, more preferably at least 11 wt% α-alumina. As is known to those skilled in the art, the amount of α-alumina can be obtained by X-ray diffraction (XRD), for example, using a D8 X-ray diffractometer (Bruker Corp) based on the integral intensity ratio of the (113) plane. However, a large amount of α-alumina can lead to an increase in the number of defects such as scratches and pits on the substrate surface. The inventors have found that the compositions of the present invention exhibit high material removal rates even with low α-alumina content, resulting in fewer defects on the substrate surface. Therefore, the alumina abrasives preferably contain up to 96 wt%, more preferably up to 95 wt% α-alumina. In a preferred embodiment, the alumina abrasives contain 6 wt% to 96 wt%, more preferably 11 wt% to 95 wt% α-alumina.

[0023] Preferably, the alumina abrasive grains comprise a mixture of α-alumina and alumina having a non-α-crystalline phase. The alumina having a non-α-crystalline phase can be any alumina other than α-alumina, such as β-alumina, γ-alumina, δ-alumina, θ-alumina, σ-alumina, κ-alumina, η-alumina, χ-alumina, and p-alumina, or combinations thereof. Preferably, the alumina having a non-α-crystalline phase is selected from β-alumina, γ-alumina, δ-alumina, σ-alumina, θ-alumina, and combinations thereof. Preferably, the alumina abrasive grains comprise at least two crystalline phases, more preferably at least three crystalline phases. The inventors have found that the alumina abrasive grains described herein can reduce the number of surface defects on a substrate and reduce the surface roughness of the substrate surface, thereby helping to improve the visual effect of mirror finishing to obtain a bright and reflective surface.

[0024] The average particle size (diameter) of the abrasive grains affects the material removal rate. As those skilled in the art know, the average particle size of the abrasive grains can be obtained by measuring the composition using laser diffraction (e.g., using an LA-960 from Horiba). The graph obtained by this measurement provides the cumulative volume percentage of particles of a certain size, from which the corresponding D10, D30, D50, D70, and D90 values ​​can be obtained. The particle size of the alumina abrasive grains mentioned herein is obtained from the particle size distribution of the alumina abrasive grains measured in the composition.

[0025] The average particle size (D50) of the alumina abrasive corresponds to the value where the particle size of 50% by volume is smaller than this value. A smaller D50 will reduce the material removal rate. Preferably, the abrasive has a D50 of at least 0.09 µm, more preferably at least 0.41 µm, more preferably at least 1.28 µm, more preferably at least 1.72 µm, and most preferably at least 2.01 µm as measured by laser diffraction. However, if the D50 of the alumina abrasive is too large, a large number of undesirable surface defects, such as scratches and pits, will occur during CMP processing. Therefore, the abrasive preferably has a D50 of at most 15 µm, more preferably at most 12 µm, more preferably at most 10 µm, more preferably at most 8 µm, and most preferably at most 6 µm as measured by laser diffraction. In a preferred embodiment, the abrasive grains have a D50 of 0.09 µm to 15 µm, more preferably 0.41 µm to 12 µm, more preferably 1.28 µm to 10 µm, more preferably 1.72 µm to 8 µm, and more preferably 2.01 µm to 6 µm as measured by laser diffraction.

[0026] The value corresponding to D10 is: the particle size of 10% by volume particles is smaller than this value. Experiments have shown that a smaller D10 can achieve a smaller surface roughness during CMP processing. The D10 of the alumina abrasive mentioned here is obtained from the particle size distribution of the alumina abrasive in the composition. Preferably, the abrasive has a D10 of at most 10 µm, more preferably at most 8 µm, more preferably at most 6 µm, more preferably at most 4 µm, and most preferably at most 3 µm as measured by laser diffraction. However, a smaller D10 of the alumina abrasive will reduce the material removal rate. Preferably, the abrasive has a D10 of at least 0.005 µm, more preferably at least 0.009 µm, more preferably at least 0.02 µm, more preferably at least 0.04 µm, and most preferably at least 0.08 µm as measured by laser diffraction. In a preferred embodiment, the abrasive grains have a D10 of 0.005 µm to 10 µm, more preferably 0.009 µm to 8 µm, more preferably 0.02 µm to 6 µm, more preferably 0.04 µm to 4 µm, and most preferably 0.08 µm to 3 µm as measured by laser diffraction.

[0027] The value corresponding to D30 is: 30% by volume of particles with a diameter smaller than this value. Experiments have shown that a smaller D30 for alumina abrasive grains can achieve a smaller surface roughness during CMP processing. The D30 of the alumina abrasive grains mentioned here is obtained from the particle size distribution of the alumina abrasive grains measured in the composition. Preferably, the abrasive grains have a D30 of at most 12.5 µm, more preferably at most 11 µm, more preferably at most 9 µm, more preferably 7 µm, and most preferably at most 5 µm as measured by laser diffraction. However, a smaller D30 for alumina abrasive grains will reduce the material removal rate. Preferably, the abrasive grains have a D30 of at least 0.009 µm, more preferably at least 0.02 µm, more preferably at least 0.05 µm, more preferably at least 0.81 µm, and most preferably at least 1.12 µm as measured by laser diffraction. In a preferred embodiment, the abrasive grains preferably have a D30 with a laser diffraction measurement of 0.009 µm to 12.5 µm, more preferably 0.02 µm to 11 µm, more preferably 0.05 µm to 9 µm, more preferably 0.81 µm to 7 µm, and most preferably 1.12 µm to 5 µm.

[0028] The value corresponding to D70 is: 70% by volume of particles with a diameter smaller than this value. A higher D70 for alumina abrasive grains leads to a higher material removal rate. The D70 of the alumina abrasive grains mentioned here is obtained from the particle size distribution of the alumina abrasive grains measured in the composition. Preferably, the abrasive grains have a D70 of at least 0.13 µm, more preferably at least 0.34 µm, more preferably at least 0.78 µm, more preferably at least 1.71 µm, and most preferably at least 2.68 µm as measured by laser diffraction. However, if the D70 of the alumina abrasive grains is too large, a large number of undesirable surface defects, such as scratches and pits, will occur during CMP processing. Preferably, the abrasive grains have a D70 of at most 19 µm, more preferably at most 16 µm, more preferably at most 13 µm, more preferably at most 10 µm, and most preferably at most 8 µm as measured by laser diffraction. In a preferred embodiment, the abrasive grains preferably have a D70 of 0.13 µm to 19 µm, more preferably 0.34 µm to 16 µm, more preferably 0.78 µm to 13 µm, more preferably 1.71 µm to 10 µm, and most preferably 2.68 µm to 8 µm as measured by laser diffraction.

[0029] The value corresponding to D90 is: 90% by volume of particles with a diameter smaller than this value. A higher D90 of the abrasive grains leads to a higher material removal rate. The D90 of the alumina abrasive grains mentioned here is obtained from the particle size distribution of the alumina abrasive grains measured in the composition. Preferably, the abrasive grains have a D90 of at least 0.16 µm, more preferably at least 1.58 µm, more preferably at least 2.15 µm, more preferably at least 3.26 µm, and most preferably at least 4.42 µm as measured by laser diffraction. However, if the D90 is too large, a large number of undesirable surface defects, such as scratches and pits, will occur during CMP processing. Preferably, the abrasive grains have a D90 of at most 25 µm, more preferably at most 21 µm, more preferably at most 18 µm, more preferably at most 15 µm, and most preferably at most 12 µm as measured by laser diffraction. In a preferred embodiment, the abrasive grains have a D90 of 0.16 µm to 25 µm, more preferably 1.58 µm to 21 µm, more preferably 2.15 µm to 18 µm, more preferably 3.26 µm to 15 µm, and most preferably 4.42 µm to 12 µm as measured by laser diffraction.

[0030] The abrasive grains should have a suitable BET surface area. The BET surface area can be measured by those skilled in the art using the Brunauer-Emmett-Teller method by measuring nitrogen adsorption on the abrasive grain surface. A larger surface area increases the contact area between the grains and the substrate, thereby improving material removal efficiency. Therefore, the abrasive grains preferably have a surface area of ​​at least 2.1 μm. 2 / g, more preferably at least 6.4 m 2 / g, more preferably at least 10.1 m 2 / g, optimally at least 16.3 m 2 The BET surface area is approximately 94.7 m² / g. Preferably, the abrasive grains have a maximum BET surface area of ​​94.7 m² / g. 2 / g, more preferably up to 81.2 m 2 / g, more preferably up to 72.9 m 2 / g, optimal value up to 60.6m 2 / g of BET surface area.

[0031] Preferably, the abrasive grains are positively charged. Charge refers to zeta potential, which can be measured, for example, by a Mastersizer S (Malvern Instruments). As known to those skilled in the art, the zeta potential of the abrasive grains in a composition refers to the potential at the interface between the moving fluid within the composition and the fluid-stabilized layer attached to the abrasive grains dispersed in the composition. A higher zeta potential results in stronger electrostatic repulsion between particles, thereby increasing the stability of the particle dispersion in the composition. Preferably, the abrasive grains in the composition have a negative zeta potential at pH 6 to 7, more preferably at least -0.5 mV, more preferably at least -1 mV, more preferably at least -2 mV, and most preferably at least -3 mV at pH 6 to 7. Preferably, the abrasive grains in the composition have a zeta potential of up to -50 mV, more preferably up to -40 mV, more preferably up to -30 mV, and most preferably up to -20 mV at pH 6 to 7. Preferably, the abrasive grains have a zeta potential of -0.5 mV to -50 mV, more preferably -1 mV to -40 mV, more preferably -2 mV to -30 mV, and more preferably -3 mV to -20 mV in the composition at a pH of 6 to 7.

[0032] The composition also includes an oxidizing agent. Depending on the substrate, the oxidizing agent can react with the substrate surface and promote material removal from the substrate during the polishing process. Specifically, the oxidizing agent can be an inorganic peroxide, an organic peroxide, or a combination thereof, such as hydrogen peroxide, percarbonate, benzyl peroxide, peracetic acid, dibutyl peroxide, monopersulfate, dipersulfate, peroxide, urea peroxide, perchlorate, periodate, perborate, perbromate, permanganate, or a combination thereof.

[0033] Preferably, the oxidant is an inorganic peroxide. The oxidant can be present in the composition in any suitable form, such as an acid, conjugate acid, salt (e.g., potassium salt, sodium salt, ammonium salt), or a combination thereof. The oxidant according to the invention can improve the material removal rate of the substrate during polishing.

[0034] Too low a concentration of oxidant will reduce the material removal rate of the substrate during the polishing process. Preferably, when used, the composition contains at least 0.01 wt%, more preferably at least 0.06 wt%, more preferably at least 0.12 wt%, more preferably at least 0.28 wt%, and most preferably at least 0.51 wt% of oxidant. Preferably, when used, the composition contains at most 15 wt%, more preferably at most 10 wt%, more preferably at most 8 wt%, more preferably at most 7 wt%, and most preferably at most 6 wt% of oxidant. In a preferred embodiment, when used, the composition contains 0.01 wt% to 15 wt%, more preferably 0.06 wt% to 10 wt%, more preferably 0.12 wt% to 8 wt%, more preferably 0.28 wt% to 7 wt%, and most preferably 0.51 wt% to 6 wt% of oxidant.

[0035] The composition further comprises a complexing agent. The complexing agent can bind metal ions that may form during the chemical mechanical polishing process. Depending on the substrate being polished, the complexing agent can improve the material removal rate during polishing. Suitable complexing agents are dicarboxylic acids, polycarboxylic acids, amino acids, organic amines, aminocarboxylic acids, polyaminopolycarboxylic acids, phosphates, polyphosphates, organophosphonic acids, phosphonoylcarboxylic acids, phenolic derivatives, ketones, or combinations thereof. The complexing agent can be present in the composition in any suitable form, such as an acid, conjugate acid, salt (e.g., potassium salt, sodium salt, ammonium salt), or combinations thereof.

[0036] Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, maleic acid, phthalic acid, tartaric acid, aspartic acid, glutamic acid, gluconic acid, and combinations thereof. Examples of polycarboxylic acids include citric acid, butanetetracarboxylic acid, and combinations thereof. Examples of organic amines include ethylenediamine, diethylenetriamine, trimethyltetraamine, and combinations thereof. Examples of aminopolycarboxylic acids include ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenediaminetetraacetic acid (EGTA), diethylenetriaminepentaacetic acid (DTPA), diaminohydroxypropanetetraacetic acid (DTPA-OH), triethylenetetraaminehexaacetic acid (TTHA), iminodiacetic acid (IDA), nitrotriacetic acid (NTA), bis(aminophenoxyethanetetraacetic acid) (BAPTA), tetraxetan (DOTA), nicotinamide, ethylenediaminedihydroxyphenylacetic acid (EDDHA), nitrilotriacetic acid, and combinations thereof. Examples of organophosphonic acids include ethylenediaminetetra(methylenephosphonic acid) (EDTMP), aminotri(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid) (DTPMP), 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), 6-hexyldiphosphonic acid, 1,5-pentenediphosphonic acid, 1,4-phenyldiphosphonic acid, xylenediphosphonic acid, diethylenetriaminepenta(methylenephosphonic acid), and hexamethylenediamine-N,N,N',N'-tetra(methylphosphonic acid). Bis(hexamethylenetriaminepenta(methylenephosphonic acid)), aminotri(methylenephosphonic acid)), methylphosphonic acid, (aminomethyl)phosphonic acid, nitrotrimethylenephosphonic acid, 4-amino-1-hydroxybutane-1,1-diphosphonic acid, iminodi(methylphosphonic acid), (1-hydroxy-2-(1H-imidazol-1-yl)ethane-1,1-diyl)diphosphonic acid, ethylenediaminetetra(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane- 1,1,2-Triphosphonic acid, methanehydroxyphosphonic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, hypozoxytriacetic acid, sodium hypozoxytriacetate, ammonium hypozoxytriacetate, aminotris(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, α-methylphosphonic acid, and combinations thereof. Examples of ketones include 1,3-diketones, etc.

[0037] Preferably, the complexing agent is an organophosphonic acid. The organophosphonic acid may have one, two, three, or more phosphonic acid groups. Preferably, the complexing agent is an organobisphosphonic acid. In the most preferred embodiment, the complexing agent is HEDP, an organobisphosphonic acid that can complex iron, copper, and zinc, exhibiting good corrosion and scale inhibition properties and good chemical stability at high pH values. It has been found that the complexing agent of the present invention increases the material removal rate of the substrate during CMP treatment.

[0038] Preferably, when used, the composition comprises at least 0.1 wt%, more preferably at least 0.5 wt%, more preferably at least 1.1 wt%, more preferably at least 2.2 wt%, and most preferably at least 5.2 wt% of a complexing agent. Preferably, when used, the composition comprises at most 33.3 wt%, more preferably at most 27.5 wt%, more preferably at most 19.8 wt%, more preferably at most 15.2 wt%, and most preferably at most 10.1 wt% of a complexing agent. In a preferred embodiment, the composition comprises from 0.1 wt% to 33.3 wt%, more preferably from 0.5 wt% to 27.5 wt%, more preferably from 1.1 wt% to 19.8 wt%, more preferably from 2.2 wt% to 15.2 wt%, and more preferably from 5.2 wt% to 10.1 wt% of a complexing agent.

[0039] The composition comprises an aqueous carrier. The abrasive particles and chemical additives are suspended in the aqueous carrier. This aqueous carrier allows the abrasive particles and chemical additives to contact the substrate and polishing pad during CMP processing. The aqueous carrier can be any component suitable for suspending abrasive particles and oxidants. Examples of the aqueous carrier include water, ethers (such as dialkylene and tetrahydrofuran), alcohols (such as methanol and ethanol), and combinations thereof. Preferably, the aqueous carrier contains at least 50 wt%, more preferably at least 70 wt%, more preferably at least 90 wt%, more preferably at least 95 wt%, and most preferably at least 99 wt% water. Preferably, the water is deionized water.

[0040] The composition contains a pH adjuster when used. This pH adjuster helps the composition achieve a suitable pH. The pH adjuster can be a base or a salt thereof. The base or its salt can be an organic base, an inorganic base, or a combination thereof.

[0041] Examples of inorganic bases include alkali metal hydroxides (e.g., potassium hydroxide, sodium hydroxide, lithium hydroxide), alkaline earth metal hydroxides (e.g., magnesium hydroxide, calcium hydroxide, beryllium hydroxide), alkali metal carbonates (e.g., potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, lithium bicarbonate), alkaline earth metal carbonates (e.g., magnesium carbonate, calcium carbonate, beryllium carbonate), alkali metal phosphates (e.g., tripotassium phosphate, trisodium phosphate, dipotassium phosphate, disodium phosphate), alkaline earth metal phosphates (e.g., magnesium phosphate, calcium phosphate, beryllium phosphate), ammonium carbonate, ammonium bicarbonate, ammonium hydroxide, and combinations thereof.

[0042] Examples of organic bases include aliphatic amines, aromatic amines, quaternary ammonium hydroxides (e.g., tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH)) and combinations thereof.

[0043] Preferably, the pH adjuster is an alkali metal hydroxide, a quaternary ammonium hydroxide, an alkali metal carbonate, or a combination thereof. In a particularly preferred embodiment, the pH adjuster is selected from tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, potassium hydroxide, sodium hydroxide, potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, and combinations thereof. The pH adjuster of the present invention has been found to increase the material removal rate of the substrate during CMP treatment. The composition may contain a pH adjuster at a concentration suitable for achieving the pH of the present invention.

[0044] The composition may optionally also include a pH buffer. This pH buffer helps maintain a suitable pH for the composition. The pH buffer can be any suitable buffer. It can be, for example, a phosphate, sulfate, acetate, borate, ammonium salt, or a combination thereof. The composition may contain a pH buffer at a concentration suitable for maintaining the pH of the present invention.

[0045] The pH of the composition affects the substrate removal rate during CMP treatment. It has been found that alkaline pH leads to lower material removal rates, while acidic pH poses a risk of corroding iron and stainless steel components in chemical mechanical polishing equipment. Therefore, it is preferred that the composition has a pH of at least 4.5, more preferably at least 5.0, even more preferably at least 5.5, and most preferably at least 6.0 when used. Preferably, the composition has a pH of up to 8.5, more preferably up to 8.0, even more preferably up to 7.5, and most preferably up to 7.0 when used. In a preferred embodiment, the pH range of the composition is 4.5 to 8.5, more preferably 5.0 to 8.0, even more preferably 5.5 to 7.5, and most preferably 6.0 to 7.0 when used.

[0046] The composition further comprises a dispersant that helps disperse alumina abrasive particles and maintain their stability in solution, thereby improving shelf life. The dispersant is preferably nanoclay, polyacrylic acid, sodium dodecylbenzenesulfonate, tetrasodium pyrophosphate, sodium hexametaphosphate, or a combination thereof. In a particularly preferred embodiment, the dispersant is nanoclay. As used herein, the term "nanoclay" refers to clay with a z-average particle size of up to 1000 nm. Nanoclay can be any type of nanoclay, such as natural clay, synthetic clay, modified clay, or a combination thereof. Examples of nanoclays include kaolin (such as kaolinite, dickite, halloysite, and pearl clay), montmorillonite (such as saponite, lithium montmorillonite, lithium saponite, chlorite, bedesulfurite, magnesite, bentonite, andalusite, kyanite, sillimanite, kaolinite, metakaolinite, mullite, aluminum silicate, aluminum silicate dihydrate, potassium aluminum silicate, sodium aluminum silicate, calcium aluminum silicate, aluminum oxide silicate, magnesium aluminum silicate, and boron aluminum silicate), illite (e.g., mica such as phlogopite, biotite, lithium mica, muscovite, and glauconite), chlorite, palygorskite, sepiolite, vermiculite, talc, pyrophyllite, modified forms of such nanoclays, and combinations thereof. In a preferred embodiment, the nanoclay is montmorillonite. In a particularly preferred embodiment, the nanoclay is selected from bentonite, lithium saponite, magnesium aluminum silicate, kaolinite, or combinations thereof.

[0047] For example, the nano-clay can be purchased from Shengxinxin Chemical Technology Co., Ltd. (Guangzhou, China).

[0048] It has been found that the composition containing nano-clay of the present invention can extend the shelf life of the composition, and that the nano-clay of the present invention can reduce the decrease in material removal rate during recycling.

[0049] Preferably, when used for polishing, the composition contains at least 0.0001 wt%, more preferably at least 0.001 wt%, more preferably at least 0.01 wt%, more preferably at least 0.03 wt%, and most preferably at least 0.05 wt% of nanoclay. However, the amount of nanoclay should not be too high, as it can hinder the interaction between the abrasive grains and the substrate surface, thereby reducing the material removal rate during the CMP process. Therefore, when used, the composition preferably contains up to 15 wt%, more preferably up to 13 wt%, more preferably up to 12 wt%, more preferably up to 11 wt%, and most preferably up to 10 wt% of nanoclay. In a preferred embodiment, the composition contains 0.0001 wt% to 15 wt%, more preferably 0.001 to 13 wt%, more preferably 0.01 wt% to 12 wt%, more preferably 0.03 wt% to 11 wt%, and more preferably 0.05 wt% to 10 wt% of nanoclay.

[0050] The composition should have high viscosity. Viscosity can be measured in mPa*s (millipascal-seconds) at 25°C using an NDJ-8S viscometer (Shanghai Lichen Instrument Technology Co., Ltd.). High viscosity of the composition can be achieved, for example, through the nano-clay of the present invention. It has been found that the viscosity of the present invention can reduce abrasive particle aggregation and agglomeration, and achieve fewer defects on the substrate surface. Preferably, the composition has a viscosity of at least 2 mPa*s, more preferably at least 5 mPa*s, and most preferably at least 8 mPa*s when measured as a 2% solution at 25°C; preferably, the composition has a viscosity of up to 903 mPa*s, more preferably up to 80 mPa*s, and most preferably up to 70 mPa*s when measured as a 2% solution at 25°C.

[0051] Preferably, the nano-clay carries a negative charge. The larger the absolute value of the negative Zeta potential of the nano-clay, the more stable the dispersion system. Preferably, the value of the Zeta potential of the nano-clay is at least -5 mV, more preferably at least -10 mV, more preferably at least -15 mV, more preferably at least -20 mV, and most preferably at least -22 mV.

[0052] The zeta potential, particle size distribution, and z-mean particle size of the nanoclay can be tested after sonicating a 0.1 wt.% aqueous dispersion of the nanoclay at 25°C for 30 minutes. The zeta potential, particle size distribution, and z-mean particle size of the nanoclay are measured in the aqueous dispersion, not in the composition. The zeta potential of the nanoclay can be measured using a Mastersizer S (Malvern Instruments Ltd., UK); the particle size distribution and z-mean particle size can be further measured by dynamic light scattering, for example using a Zetasizer Nano ZSE (Malvern Instruments Ltd.); the z-mean particle size refers to the intensity-weighted average hydrodynamic size of the particle ensemble measured by dynamic light scattering (e.g., using a Zetasizer Nano ZSE (Malvern Instruments Ltd.)). The D10, D30, D50, D70, and D90 of the nanoclay can be obtained from the particle size distribution measured as described above.

[0053] The inventors have discovered that nanoclays with smaller z-average particle sizes can improve the dispersibility of alumina particles, extend the shelf life of the composition, reduce the number of pits on the substrate surface, and reduce surface roughness. They have found that nanoclays with larger z-average particle sizes cause agglomeration and aggregation of alumina abrasive particles, leading to a greater increase in the measured D10, D30, D50, D70, and D90 of alumina in the composition, and consequently increasing surface roughness and surface defects (such as pits). Furthermore, the inventors have found that nanoclays with nanoscale dimensions can improve the surface morphology of stainless steel, while micron-scale nanoclays deteriorate the surface morphology of stainless steel. The nanoclays should have a suitable z-average particle size. Preferably, the nanoclays have a z-average particle size of at most 1100 nm, preferably at most 1050 nm, preferably at most 1000 nm, preferably at most 990 nm, preferably at most 980 nm, and more preferably at most 970 nm, as measured by dynamic light scattering. However, if the z-average particle size of the nanoclay is too small, it will affect the viscosity of the composition, causing the opposite effect. Preferably, the nanoclay has a z-average particle size of at least 1 nm, preferably at least 2 nm, preferably at least 5 nm, preferably at least 10 nm, preferably at least 15 nm, and more preferably at least 20 nm, as measured by dynamic light scattering. In a preferred embodiment, the nanoclay preferably has a z-average particle size of 1 nm to 1100 nm, preferably 2 nm to 1050 nm, preferably 5 nm to 1000 nm, preferably 10 nm to 990 nm, preferably 15 nm to 980 nm, and more preferably 20 nm to 970 nm, as measured by dynamic light scattering.

[0054] Experiments have shown that nanoclays with a smaller D10 can achieve a smaller surface roughness during CMP processing. Preferably, the nanoclay has a D10 of at most 600 nm, more preferably at most 550 nm, more preferably at most 500 nm, more preferably at most 450 nm, and most preferably at most 400 nm, as measured by dynamic light scattering. However, if the D10 of the nanoclay is too small, it will reduce the material removal rate. Preferably, the nanoclay has a D10 of at least 0.01 nm, more preferably at least 0.05 nm, more preferably at least 0.1 nm, more preferably at least 0.5 nm, and most preferably at least 1 nm, as measured by dynamic light scattering. In a preferred embodiment, the nanoclay has a D10 of 0.01 nm to 600 nm, 0.05 nm to 550 nm, 0.1 nm to 500 nm, more preferably 0.5 nm to 450 nm, and more preferably 1 nm to 400 nm, as measured by dynamic light scattering.

[0055] Experiments have shown that nanoclays with a smaller D30 can achieve a smaller surface roughness during CMP processing. Preferably, the nanoclay has a D30 of at most 1100 nm, more preferably at most 1050 nm, more preferably at most 1000 nm, more preferably at most 950 nm, and most preferably at most 900 nm, as measured by dynamic light scattering. However, a smaller D30 in the nanoclay reduces the material removal rate. Preferably, the nanoclay has a D30 of at least 0.05 nm, more preferably at least 0.1 nm, more preferably at least 0.5 nm, more preferably at least 1 nm, and most preferably at least 1.3 nm, as measured by dynamic light scattering. In a preferred embodiment, the nanoclay has a D30 of 0.05 nm to 1100 nm, more preferably 0.1 nm to 1050 nm, more preferably 0.5 nm to 1000 nm, more preferably 1 nm to 950 nm, and most preferably 1.3 nm to 900 nm, as measured by dynamic light scattering.

[0056] Experiments have shown that nanoclays with a smaller D50 can achieve a smaller surface roughness during CMP processing. Preferably, the nanoclay has a D50 of at most 1300 nm, more preferably at most 1200 nm, more preferably at most 1100 nm, more preferably at most 1000 nm, and more preferably at most 950 nm as measured by dynamic light scattering. However, a smaller D50 in the nanoclay reduces the material removal rate. Preferably, the nanoclay has a D50 of at least 0.1 nm, more preferably at least 0.5 nm, more preferably at least 1 nm, more preferably at least 1.3 nm, and most preferably at least 1.5 nm as measured by dynamic light scattering. In a preferred embodiment, the nanoclay has a D50 as measured by dynamic light scattering of 0.1 nm to 1300 nm, more preferably 0.5 nm to 1200 nm, more preferably 1 nm to 1100 nm, more preferably 1.3 nm to 1000 nm, and most preferably 1.5 nm to 950 nm.

[0057] Experiments have shown that nanoclays with a smaller D70 can achieve a smaller surface roughness during CMP processing. Preferably, the nanoclay has a D70 of at most 1600 nm, more preferably at most 1550 nm, more preferably at most 1500 nm, more preferably at most 1450 nm, and most preferably at most 1400 nm, as measured by dynamic light scattering. However, a smaller D70 in the nanoclay reduces the material removal rate. Preferably, the nanoclay has a D70 of at least 0.5 nm, more preferably at least 1 nm, more preferably at least 1.4 nm, more preferably at least 1.8 nm, and most preferably at least 2 nm, as measured by dynamic light scattering. In a preferred embodiment, the nanoclay has a D70 of 0.5 nm to 1600 nm, more preferably 1 nm to 1550 nm, more preferably 1.4 nm to 1500 nm, more preferably 1.8 nm to 1450 nm, and most preferably 2 nm to 1400 nm, as measured by dynamic light scattering.

[0058] Experiments have shown that nanoclays with a smaller D90 can achieve a smaller surface roughness during CMP processing. Preferably, the nanoclay has a D90 of at most 2000 nm, more preferably at most 1950 nm, more preferably at most 1900 nm, more preferably at most 1800 nm, and most preferably at most 1700 nm, as measured by dynamic light scattering. However, a smaller D90 in the nanoclay reduces the material removal rate. Preferably, the nanoclay has a D90 of at least 1 nm, more preferably at least 2 nm, more preferably at least 3 nm, more preferably at least 3.5 nm, and most preferably at least 4 nm, as measured by dynamic light scattering. In a preferred embodiment, the nanoclay has a D90 of 1 nm to 2000 nm, more preferably 2 nm to 1950 nm, more preferably 3 nm to 1900 nm, more preferably 3.5 nm to 1800 nm, and most preferably 4 nm to 1700 nm, as measured by dynamic light scattering.

[0059] The increase in alumina particle sizes D10, D30, D50, D70, and D90 refers to the ratio of the alumina particle size in the composition to the alumina particle size in the aqueous dispersion (regardless of the composition's components). This is specifically obtained through laser diffraction measurement, meaning the ratio of the alumina particle size measured in the composition to the alumina particle size measured in an alumina dispersion with an alumina concentration of 15 wt.% (85 wt.% water). The inventors have discovered that the nano-clay of this invention can reduce the increase ratio of alumina particle sizes D10, D30, D50, D70, and D90. Preferably, the increase ratio of alumina D10 in the composition containing nano-clay to the alumina D10 measured in an alumina dispersion with an alumina concentration of 15 wt.% (85 wt.% water) is at most 3.5, more preferably at most 3, more preferably at most 2.5, and most preferably at most 2. Preferably, the increase ratio of alumina D30 in the composition to that measured in an alumina dispersion (85 wt.% water) with an alumina concentration of 15 wt.% is at most 4.2, preferably at most 3.5, more preferably at most 3, and even more preferably at most 2.5. Preferably, the increase ratio of alumina D50 in the composition to that measured in an alumina dispersion (85 wt.% water) with an alumina concentration of 15 wt.% is at most 5.5, more preferably at most 5, further preferably at most 4.5, and even more preferably at most 4. Preferably, the increase ratio of alumina D70 in the composition to that measured in an alumina dispersion (85 wt.% water) with an alumina concentration of 15 wt.% is at most 5.5, more preferably at most 5, further preferably at most 4.5, and even more preferably at most 4. Preferably, the ratio of the increase in D90 of alumina in the composition to the increase in D90 of alumina measured in an alumina dispersion (85 wt.% water) with an alumina concentration of 15 wt.% is at most 5, more preferably at most 5, further preferably at most 4.5, and most preferably at most 4.

[0060] The composition may optionally contain one or more preservatives. The preservative can be any suitable compound that prevents, inhibits, reduces the growth of, suppresses the activity of, or eliminates unwanted microorganisms. Examples of suitable preservatives include sodium hypochlorite, methylisothiazolinone, benzisothiazolinone, chloromethylisothiazolinone, and combinations thereof. Preferably, the composition contains at least 0.6 ppm by weight, more preferably at least 1.6 ppm by weight, more preferably at least 2.7 ppm by weight, more preferably at least 3.8 ppm by weight, and most preferably at least 4.6 ppm by weight. High concentrations of preservatives can lead to undesirable interactions between the preservative and other components of the composition, as well as the substrate. Therefore, the composition preferably contains at most 98 ppm by weight, more preferably at most 83 ppm by weight, more preferably at most 74 ppm by weight, and most preferably at most 69 ppm by weight. ppm as used herein refers to ppm by weight.

[0061] Preferably, the composition is substantially free of polymers. The polymer can be any polymer. Typically, polymers are used in CMP compositions containing alumina to improve the dispersibility of alumina particles, thereby increasing the shelf life of the composition and preventing particle aggregation that could lead to defects on the substrate surface. However, during CMP polishing, polymers generally reduce the material removal rate of the substrate. Surprisingly, it has been found that even without polymers, the compositions according to the invention induce fewer defects on the substrate surface.

[0062] As used herein, the term “substantially free of component X” means a composition that substantially does not contain said component X, i.e., such component may at most be present in the composition as an impurity or contaminant, but is not added to the composition as a separate component.

[0063] The present invention also provides a method for chemical mechanical polishing (CMP) of a substrate, the method comprising the steps of: (a) providing a CMP composition; (b) contacting the substrate with the CMP composition and a polishing pad; (c) moving the polishing pad relative to the substrate, wherein the composition is located between the two; and (d) removing at least a portion of the substrate. The CMP composition provided in step (a) is the composition of the present invention. The method may optionally include other steps.

[0064] The composition can be prepared using suitable techniques known to those skilled in the art. The abrasive particles, nanoclay, and other chemical additives described above can be added to the aqueous carrier in any order and in suitable amounts to achieve the desired concentration. The abrasive particles, nanoclay, and other chemical additives can be mixed and stirred in the aqueous carrier. The pH value can be adjusted using the pH adjuster and pH buffer described above to obtain and maintain the desired pH. The abrasive particles, nanoclay, and other chemical additives can be added at any time before use (e.g., one month, one day, one hour, or one minute) or during CMP treatment.

[0065] The composition can be provided as a single-part system, a two-part system, or a multi-part system. For example, as a two-part system, the first part may include abrasive particles and one or more chemical additives, and the second part may include nanoclay and one or more other chemical additives. The first and second parts can be mixed at any time prior to CMP treatment (e.g., one month, one day, one hour, or one minute) or during CMP treatment, for example when using polishing equipment with a supply path having multiple CMP compositions.

[0066] The composition can be provided as a concentrate and can be diluted with an appropriate amount of water before use. The concentration of each component in the composition can be any suitable, such as 2, 3, 10, or 25 times the concentration described above for use. For example, the concentration of abrasive particles and chemical additives contained in the concentrate is such that, after dilution with an appropriate amount of water, the abrasive particles and chemical additives are present in the composition at the concentrations described above. If the composition is provided, for example, as a two-part system, one or both parts can be provided as a concentrate. The two parts can be provided with different concentrations, for example, a first part with a concentration of three times and a second part with a concentration of five times. The two parts can be diluted in any order before mixing.

[0067] During CMP processing, the composition should achieve a high material removal rate for substrates containing ferrous metal alloys, such as stainless steel, carbon steel, leaded steel, tool steel, and cast steel. Preferably, the composition exhibits a material removal rate of at least 8 µm / h, more preferably at least 13 µm / h, more preferably at least 21 µm / h, and more preferably at least 25 µm / h for substrates containing ferrous metal alloys during CMP processing.

[0068] This invention also relates to the use of the compositions of this invention. The compositions of this invention can be used for polishing various materials. Preferably, the compositions of this invention are used for chemical mechanical polishing of substrates comprising one or more materials, said materials including metals, semi-metals, metal alloys, metal oxides, semi-metal oxides, carbides, minerals, plastics, or combinations thereof. As known to those skilled in the art, chemical mechanical polishing refers to the process of placing a substrate within a CMP apparatus, bringing it into contact with a polishing pad and a CMP composition situated between them. The polishing pad moves relative to the substrate to remove portions of the substrate.

[0069] For some materials such as metals, metal alloys, metal oxides, and minerals, the composition is used in the final polishing step, while for other materials such as ceramics and plastics, the composition is used in the intermediate polishing step.

[0070] Examples of metals, metal alloys, and metal oxides that can be polished using the compositions of the present invention include iron, ferroalloys (e.g., steel), aluminum, aluminum alloys, titanium, titanium alloys, nickel, nickel alloys, copper, copper alloys, Kovar, cupronickel, chromium-nickel-iron alloys, brass, niobium, bronze, nickel-silver, beryllium, Monel alloys, vanadium, Hastelloy, tantalum, silver, gold, molybdenum, Nimonic alloys, Waspalooy alloys, tungsten, ceramics, and combinations thereof. The metal oxides may be in the form of single crystals, polycrystalline materials, sintered bodies (ceramics), or combinations thereof.

[0071] In a particularly preferred embodiment, the present invention is used for chemical mechanical polishing of substrates comprising a metal alloy. The metal alloy may comprise one metal as its main component and at least one metal different from the main component. There is no limitation on the number of metals different from the main component; for example, it may be two, three, or more. Preferably, the metal as the main component of the metal alloy is selected from aluminum, titanium, magnesium, iron, nickel, and copper. In a particularly preferred embodiment, the main metal is iron. Examples of ferroalloys include stainless steel, carbon steel, alloy steel, lead-containing steel, tool steel, cast steel, maraging steel, cast iron, and combinations thereof.

[0072] The present application will be described in detail below through specific embodiments.

[0073] Example 1

[0074] The stainless steel material removal rate, surface roughness, and surface defects of compositions A1 and E1-E7 were evaluated. Compositions A1 and E1-E7 each contained 15 wt.% alumina abrasive particles, 1 wt.% hydrogen peroxide, 1 wt.% lithium saponite with a z-average particle size of 61.75 nm and a zeta potential of -31 mV, and 30 ppm (by weight) of the preservative KATHON. TMLX 150 (Dow Inc.). The pH of these compositions was adjusted to 6.5 using KOH. All compositions were polymer-free. Compositions E1-E7 also contained 2 wt.% of a complexing agent, the specific components of which are shown in Table 1.

[0075] The z-mean particle size of magnesium aluminum silicate was measured by dynamic light scattering from a 0.1 wt% dispersion using a Zetasizer Nano ZSE (Malvern Instruments Ltd., UK), and the D50 was obtained as described above. The zeta potential of the nanoclay was measured in a 0.1 wt% aqueous dispersion using a Mastersizer S (Malvern Instruments Ltd., UK). The magnesium aluminum silicate aqueous dispersion was sonicated at 25°C for 30 minutes prior to the z-mean particle size and zeta potential measurements to obtain a homogeneous dispersion.

[0076] As described above, before adding alumina abrasive particles to the composition, the D30, D50, D70, and D90 of the alumina abrasive particles were obtained by laser diffraction in an 85 wt.% aqueous solution using a Horiba LA960. After dispersing the alumina particles, the D30, D50, D70, and D90 of the alumina abrasive particles were measured within the composition using a Horiba LA960. As described above, the increase ratio of D30, D50, D70, and D90 was obtained by calculating the ratio of the corresponding particle size of the alumina abrasive particles dispersed in the composition to the corresponding particle size of the alumina abrasive particles dispersed in the 85 wt.% aqueous solution.

[0077] Using a Nano-Max polishing tool (Shenzhen Nanos Precision Machinery Technology Co., Ltd.), with a platen speed of 80 rpm, a downforce of 2.0 psi, and a slurry flow rate of 100 ml / min, polish a surface with an area of ​​9 cm². 2 Polish a 3 mm thick stainless steel plate for 4 minutes.

[0078] The polished stainless steel sheet underwent a visual inspection for surface defects, and pits were counted and classified as A = no corresponding defects, B = less than 10 corresponding defects, and C = more than 10 corresponding defects. The results are shown in Table 1. The material removal rate of the stainless steel sheet was measured using an electronic balance and calculated based on the weight difference before and after polishing. The material removal rate is listed in Table 1 as a percentage relative to the material removal rate of composition A1. Surface roughness (average roughness, Ra) was measured using an SJ-410 surface roughness tester (Mitutoyo Corp) over a measurement length of 25 mm and is listed in Table 1. As is known to those skilled in the art, surface roughness is the arithmetic mean of the absolute values ​​of the deviations of the profile height from the average height over the measurement length. Furthermore, all surface roughness values ​​below 0.02 are considered good.

[0079] Table 1

[0080]

[0081] As shown in Table 1, compositions E1-E7 containing different complexing agents exhibit higher removal rates than A1 without a complexing agent. Furthermore, E5, using only HEDP as the complexing agent, shows no pitting and has the lowest surface roughness. Compositions E1-E4 and E6-E7, using other complexing agents, do not show ideal results.

[0082] Example 2

[0083] The stainless steel material removal rate, surface roughness, and surface defects of compositions A2 and E8-E11 were evaluated. Compositions A2 and E8-E11 comprise 15 wt.% alumina abrasive particles, 2 wt.% 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), 1 wt.% bentonite with a z-average particle size of 444.5 nm and a zeta potential of -28.9 mV, and 30 ppm (by weight) of the corrosion inhibitor KATHON. TM LX 150 (Dow Inc.). The pH of these compositions was adjusted to 6.5 using KOH. Compositions E8-E11 also contain 1 wt.% of the oxidant shown in Table 2.

[0084] Prior to polishing, the zeta potential of the alumina particles in the composition was measured using a Mastersizer S (Malvern Instruments Ltd., UK). The stainless steel sheet was polished, and its relative removal rate, surface roughness, and pitting were measured as described in Example 1. The results are shown in Table 2.

[0085] Table 2

[0086]

[0087] As can be seen from Table 2, the composition using only hydrogen peroxide and nitrous acid showed no defects, and the composition E8 using hydrogen peroxide showed the lowest surface roughness.

[0088] Example 3

[0089] The stainless steel material removal rate, surface roughness, and surface defects of compositions A3-A4 and composition E12 were evaluated. Compositions A3-A4 and composition E12 comprise 15 wt.% alumina abrasive particles, 1 wt.% hydrogen peroxide, 2 wt.% 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), 1 wt.% magnesium aluminum silicate with a z-average particle size of 91.11 nm and a zeta potential of -29.8 mV, and 30 ppm (by weight) of the corrosion inhibitor KATHON. TM LX 150 (Dow Inc.). These compositions were adjusted to different pH values ​​using KOH, as shown in Table 3.

[0090] The stainless steel sheet was polished, and its relative removal rate, surface roughness, and pitting were measured as described in Example 1. The results are shown in Table 3.

[0091] The static corrosion of stainless steel by each composition was evaluated by measuring the weight of the stainless steel sheet. First, the weight of the stainless steel was measured. Then, the stainless steel sheet was placed in the composition, heated to 60°C, and left to stand for 5 hours. The weight of the stainless steel sheet was then measured again. The difference in weight before and after this process (weight loss due to corrosion) is the static corrosion assessment.

[0092] Table 3

[0093]

[0094] As can be seen from Table 3, the composition with alkaline pH exhibits the lowest static corrosion, indicating less corrosion, but the relative removal rate is not high, and the polished stainless steel plate has many defects; the composition E12 with neutral pH has a slightly lower relative removal rate than the acidic composition, but its static corrosion is lower than that of the acidic composition, its roughness is lower than that of the acidic composition, and it has no defects like the acidic composition, so it is acceptable.

[0095] Example 4

[0096] The removal rate, surface roughness, and surface defects of stainless steel materials were evaluated for compositions A5-A9 and compositions E13-E18. Compositions A5-A9 and E13-E18 comprise 15 wt.% alumina abrasive particles, 1 wt.% hydrogen peroxide, 2 wt.% 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), and 30 ppm (by weight) of the corrosion inhibitor KATHON.TM LX150 (Dow Inc.). These compositions have a pH of 6.5. All compositions except A5 also contain 1 wt.% of the nanoclays listed in Table 4. Prior to adding the nanoclays to the compositions, the Zeta potential and z-mean particle size of the nanoclays listed in Table 4 were measured using a Zetasizer Nano ZSE (Malvern Instruments Ltd., UK) as described in Example 1.

[0097] The stainless steel sheet was polished, and the relative removal rate, surface roughness, and pitting were measured as described in Experiment 1. The results are shown in Table 4.

[0098] The shelf life of compositions A5-A9 and compositions E13-E18 was evaluated: 500 mL of each composition was dispensed into a 500 mL polyethylene bottle and left to stand at room temperature without stirring. "Shelf life" was defined as the time from the start of standing of the composition until the composition precipitates and forms a hard cake that is difficult to redisperse. The shelf life evaluation results are shown in Table 4.

[0099] Table 4

[0100]

[0101] As can be seen from Table 4:

[0102] Although compositions E13 and E14 containing magnesium aluminum silicate with an average z-particle size of less than 1000 nm of nano-clay did not have the highest relative removal rates, they exhibited low surface roughness and no pits. Among them, composition E13 containing magnesium aluminum silicate with an average z-particle size of less than 100 nm of nano-clay exhibited high relative removal rates, good surface roughness, and no pits. Compositions E15-18 containing bentonite and lithium saponite with an average z-particle size of less than 1000 nm of nano-clay exhibited low surface roughness and no pits. Among them, composition E17 containing bentonite and lithium saponite with an average z-particle size of less than 100 nm of nano-clay exhibited good surface roughness and no pits.

[0103] Shelf life was obtained by observing the compositions after they had been left to stand at room temperature. For composition A5, which did not contain nanoclay, the alumina settled after 5 days, forming a hard cake that was difficult to redisperse. All compositions A6-A9 and compositions E13-E18 containing nanoclay were observed for up to 9 months and were found to remain dispersed (without settling) after 9 months. No further observation of the compositions was conducted after 9 months.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A chemical mechanical polishing composition for metal alloy surfaces, having a pH range of 6-7 when in use, comprising alumina abrasive particles, 0.01 wt% - 15 wt% of an oxidizing agent, a dispersant, a pH adjuster, and 0.1 wt% - 33.3 wt% of a complexing agent, wherein, The dispersant is a nanoclay, the nanoclay has a mass fraction of 0.0001 wt% - 15 wt%, the nanoclay has a z-average particle size of up to 1000 nm, the nanoclay has a Zeta potential value of at least -5 mV, the alumina abrasive particles have a negative zeta potential in the composition at a pH of 6 to 7, the oxidizing agent is hydrogen peroxide; the complexing agent is 1-hydroxyethylidene-1,1-diphosphonic acid.

2. The composition of claim 1, wherein The pH adjuster is an alkali metal hydroxide, a quaternary ammonium hydroxide, an alkali metal carbonate, or a combination thereof.

3. A polishing method for a metal alloy substrate, the method being achieved using the composition of any one of claims 1-2.

Images