Chemical mechanical polishing composition for metal alloy and polishing method therefor

Abstract

A chemical mechanical polishing composition for a metal alloy and a polishing method. The composition comprises alumina abrasive particles, an oxidant, a dispersant and a pH regulator, wherein the dispersant is nanoclay, and the nanoclay has a z-average particle size of at most 1,000 nm. The composition can be used for polishing the plane of a metal alloy substrate, has a near neutral pH value, and has no risk of corroding metal parts in a polishing device.

Description

Chemical mechanical polishing composition for metal alloys and polishing method thereof Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and in particular relates to a chemical mechanical polishing composition for metal alloys and a polishing method. Background Art

[0002] Chemical Mechanical Polishing (CMP) is a common process for achieving global planarization in integrated circuit manufacturing and other fields. This process is primarily used to obtain a smooth surface that is both flat and free of scratches and impurities. This process polishes various target substrates through a combination of chemical and mechanical forces, and chemical mechanical polishing (CMP) compositions play a decisive role in this process. These compositions are typically aqueous solutions containing a uniform dispersion of various chemical additives and abrasive particles. CMP compositions, also known as polishing slurries, polishing solutions, or polishing compositions, are commonly used to polish the surfaces of various substrates (such as metals, metal alloys, minerals, and plastics).

[0003] The demand for polishing metal and metal alloy substrates is widespread, including metal parts such as those found in vehicles, ships, aircraft, pipelines, light reflectors, containers, handrails, kitchenware, cookware, architectural metals, and jewelry. Ferrous alloy substrates (such as corrosion-resistant stainless steel) are widely used in machine tools, cookware, structural materials such as surgical knives, transportation equipment, consumer electronic device parts such as smartphone and laptop casings, and metal crafts such as automobile logos. Consequently, there is a demand for polishing stainless steel surfaces.

[0004] CMP compositions containing aluminum oxide abrasives are commonly used to polish materials containing iron alloys to obtain substrates with smooth mirror surfaces. Many applications of metal alloys require low surface roughness, high brightness and a smooth mirror effect, which can be achieved by CMP compositions containing aluminum oxide abrasives. However, aluminum oxide abrasives can easily cause pits, scratches and other surface defects on the surface of metal alloy substrates. Due to lack of oxygen and local destruction of the protective passivation film of stainless steel, such surface defects can cause corrosion problems in ferrous metal alloys such as stainless steel. And in daily use, these surface defect areas are easily contaminated by dirt, bacteria, etc. Therefore, there is still a need for a CMP composition containing aluminum oxide abrasives suitable for polishing the surface of metal alloy substrates that can achieve low surface roughness and a low number of surface defects.

[0005] In order to reduce manufacturing costs, reduce waste and alleviate the environmental burden, CMP compositions are often recycled during the polishing process of metal alloy substrates. For example, a CMP composition is used for polishing, then discharged from the polishing apparatus and collected in a tank, and then recycled back to the polishing apparatus for further polishing. Therefore, it is necessary to enable CMP compositions containing aluminum oxide abrasives to have a long recycling time. The recycling time refers to the time during which the composition can be used again for chemical mechanical polishing of a substrate without an overall decrease in polishing performance (such as material removal rate). However, during recycling, the activity of the CMP composition often decreases over time, which may be due to wear, cracking and shrinkage of the aluminum oxide particles during the polishing process, or due to chemical changes in the aluminum oxide particles. The reduction in the polishing activity of the CMP composition results in a reduction in the time during which the CMP composition can be recycled for polishing, and replacing the CMP composition will lead to an increase in manufacturing costs and environmental burden. At the same time, the chemical mechanical polishing compositions currently available on the market for polishing stainless steel are generally acidic, which poses a risk of corroding iron and stainless steel parts in chemical mechanical polishing equipment. Therefore, there is still a need for a CMP composition containing aluminum oxide abrasives suitable for polishing the surface of metal alloy substrates that can achieve higher removal rates, longer recycling times, low surface defect counts, and a neutral pH value.

[0006] Summary of the Invention

[0007] 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 metal alloy substrate surfaces. The composition exhibits high material removal rates and extended recycle times, while achieving low surface roughness and low surface defect counts. Furthermore, the composition has a neutral pH and poses no risk of corrosion to metal components in the polishing equipment.

[0008] Specifically, the chemical mechanical polishing composition of the present invention comprises aluminum oxide abrasive particles, an oxidizing agent, a complexing agent, a dispersant, and a pH adjuster, wherein the dispersant is nanoclay having a z-average particle size of at most 1000 nm.

[0009] Preferably, the nanoclay has a zeta potential of at least -5 mV.

[0010] Preferably, the aluminum oxide abrasive particles have a negative zeta potential at a pH of 6 to 7 in the composition.

[0011] Preferably, the oxidant is an inorganic percompound, an organic percompound, or a combination thereof.

[0012] Preferably, the composition further comprises a complexing agent, and the complexing agent is a dicarboxylic acid, a polycarboxylic acid, an amino acid, an organic amine, an aminocarboxylic acid, a polyaminopolycarboxylic acid, a phosphate, a polyphosphate, an organic phosphonic acid, a phosphonocarboxylic acid, a phenol derivative, a ketone, and combinations thereof.

[0013] Preferably, the complexing agent is an organic phosphonic acid.

[0014] Preferably, the composition comprises from 0.1 wt% to 33.3 wt% complexing agent.

[0015] Preferably, the composition comprises 0.0001 wt% to 15 wt% nanoclay.

[0016] Preferably, the pH adjuster is an alkali metal hydroxide, a quaternary ammonium hydroxide, an alkali metal carbonate, or a combination thereof.

[0017] Another object of an embodiment of the present invention is to provide a polishing method for a metal alloy substrate, wherein the method is implemented using the above composition.

[0018] The CMP composition provided by the present invention not only achieves high material removal rates in chemical mechanical polishing of metal alloy substrates, but also has a neutral pH, eliminates the risk of metal equipment corrosion, and enables longer recycling times, making it environmentally friendly and economically efficient. Products polished with the CMP composition of the present invention exhibit low surface roughness, a low number of surface defects (scratches and pits), and a satisfactory mirror finish. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] Chemical mechanical polishing compositions typically comprise abrasive particles dispersed in an aqueous carrier. The abrasive particles can aid in the removal of material from the substrate surface during the polishing process. Preferably, the abrasive particles are metal oxide abrasive particles selected from the group consisting of cerium oxide (ceria), aluminum oxide (aluminum oxide), silicon oxide (silicon dioxide), zirconium oxide (zirconium oxide), titanium oxide (titania), germanium oxide (germania), magnesium oxide (magnesium oxide), nickel oxide, gallium oxide (gallium oxide), yttrium oxide (yttrium oxide), and combinations thereof. Preferably, the abrasive particles comprise at least 67 wt% (weight percent), 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% aluminum oxide. In particularly preferred embodiments, the abrasive particles are entirely aluminum oxide abrasive particles.

[0021] When in use, the composition preferably comprises 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% abrasive particles. As used herein, the term "when in use" refers to the moment when the composition is applied to the surface of the substrate during chemical mechanical polishing. If the concentration of abrasive particles is too high, the composition may cause undesirable surface defects such as substrate scratches during polishing. Therefore, when in use, the composition preferably comprises 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% abrasive particles. In a preferred embodiment, the composition comprises 0.02 wt% to 40 wt%, more preferably 0.24 wt% to 35 wt%, more preferably 0.63 wt% to 30 wt%, more preferably 0.63 wt% to 25 wt%, and most preferably 1.0 wt% to 20 wt% abrasive particles.

[0022] As known to those skilled in the art, the aluminum oxide abrasive grains may be fumed aluminum oxide or aluminum oxide with different crystalline phases, such as α-alumina, β-alumina, γ-alumina, δ-alumina, θ-alumina, σ-alumina, κ-alumina, η-alumina, χ-alumina, β-alumina, and combinations thereof. Preferably, the aluminum oxide abrasive grains are selected from α-alumina, β-alumina, γ-alumina, δ-alumina, σ-alumina, θ-alumina, and combinations thereof.

[0023] It has been shown that α-alumina can exhibit higher substrate material removal rates during chemical mechanical polishing compared to alumina abrasive grains having other crystalline phases. Therefore, the alumina abrasive grains preferably contain at least 6 wt%, more preferably at least 11 wt% of α-alumina. As known to those skilled in the art, the amount of α-alumina can be obtained by X-ray diffraction (XRD), for example, based on the integrated intensity ratio of the (113) plane using a D8 X-ray diffractometer (Bruker Corp). However, a large amount of α-alumina leads to an increase in the number of defects such as scratches and pits on the substrate surface. The inventors have found that the composition of the present invention can exhibit a high material removal rate even at a low α-alumina content, thereby generating a smaller number of defects on the substrate surface. Therefore, preferably, the alumina abrasive grains contain up to 96 wt%, more preferably up to 95 wt% of α-alumina. In a preferred embodiment, the alumina abrasive grains contain 6 wt% to 96 wt%, more preferably 11 wt% to 95 wt% of α-alumina.

[0024] Preferably, the aluminum oxide abrasive grains comprise a mixture of α-aluminum oxide and aluminum oxide having a non-α crystalline phase. The aluminum oxide having a non-α crystalline phase may be any aluminum oxide other than α-aluminum oxide, such as β-aluminum oxide, γ-aluminum oxide, δ-aluminum oxide, θ-aluminum oxide, σ-aluminum oxide, κ-aluminum oxide, η-aluminum oxide, χ-aluminum oxide, and β-aluminum oxide, or a combination thereof. Preferably, the aluminum oxide having a non-α crystalline phase is selected from β-aluminum oxide, γ-aluminum oxide, δ-aluminum oxide, σ-aluminum oxide, θ-aluminum oxide, and a combination thereof. Preferably, the aluminum oxide abrasive grains comprise at least two crystalline phases, more preferably at least three crystalline phases. The inventors have found that the aluminum oxide abrasive grains described herein can reduce the number of surface defects on the 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.

[0025] The average particle size (diameter) of the abrasive particles affects the material removal rate. As known to those skilled in the art, the average particle size of the abrasive particles can be determined by measuring the composition using laser diffraction (e.g., using an LA-960 from Horiba). The graph obtained from 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 aluminum oxide abrasive particles mentioned herein is obtained from the particle size distribution of the aluminum oxide abrasive particles measured in the composition.

[0026] The average particle size (D50) of the aluminum oxide abrasive corresponds to the value at which 50% by volume of the particles have a particle size smaller than this value. A smaller D50 will result in a lower 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 aluminum oxide abrasive is too large, a large number of undesirable surface defects such as scratches and pits will appear during the CMP process. 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 particles have a D50 measured by laser diffraction of 0.09 to 15 μm, more preferably 0.41 to 12 μm, more preferably 1.28 to 10 μm, more preferably 1.72 to 8 μm, more preferably 2.01 to 6 μm.

[0027] The numerical value corresponding to D10 is: 10% by volume of the particles have a particle size smaller than this value. Experiments have shown that a smaller D10 can achieve a smaller surface roughness during the CMP process. The D10 of the aluminum oxide abrasive mentioned here is obtained from the particle size distribution of the aluminum oxide abrasive measured in the composition. Preferably, the abrasive has a D10 measured by laser diffraction 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. However, a smaller D10 of the aluminum oxide abrasive will reduce the material removal rate. Preferably, the abrasive has a D10 measured by laser diffraction 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. In a preferred embodiment, the abrasive particles have a D10 measured by laser diffraction 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, most preferably 0.08 μm to 3 μm.

[0028] The numerical value corresponding to D30 is: 30% by volume of the particles have a particle size smaller than this value. Experiments have shown that a smaller D30 of the aluminum oxide abrasive can achieve a smaller surface roughness during the CMP process. The D30 of the aluminum oxide abrasive mentioned here is obtained from the particle size distribution of the aluminum oxide abrasive measured in the composition. Preferably, the abrasive has a D30 measured by laser diffraction 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. However, a smaller D30 of the aluminum oxide abrasive will reduce the material removal rate. Preferably, the abrasive has a D30 measured by laser diffraction 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. In a preferred embodiment, the abrasive particles preferably have a D30 measured by laser diffraction of 0.009 to 12.5 μm, more preferably 0.02 to 11 μm, more preferably 0.05 to 9 μm, more preferably 0.81 to 7 μm, most preferably 1.12 to 5 μm.

[0029] D70 corresponds to a value that is smaller than the particle size of 70% by volume of the particles. A higher D70 of the aluminum oxide abrasive results in a higher material removal rate. The D70 of the aluminum oxide abrasive mentioned here is obtained from the particle size distribution of the aluminum oxide abrasive measured in the composition. Preferably, the abrasive has 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 aluminum oxide abrasive is too large, a large number of unfavorable surface defects such as scratches and pits will appear during the CMP process. Preferably, the abrasive has 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 particles preferably have a D70 measured by laser diffraction 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, most preferably 2.68 μm to 8 μm.

[0030] D90 corresponds to a value that is smaller than the particle size of 90% by volume of the particles. A higher D90 of the abrasive particles results in a higher material removal rate. The D90 of the alumina abrasive particles mentioned here is obtained from the particle size distribution of the alumina abrasive particles measured in the composition. Preferably, the abrasive particles 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 unfavorable surface defects such as scratches and pits will appear during the CMP process. Preferably, the abrasive particles 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 particles have a D90 measured by laser diffraction 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, most preferably 4.42 μm to 12 μm.

[0031] The abrasive particles should have a suitable BET surface area. The BET surface area can be measured by a person skilled in the art using the Brunauer-Emmett-Teller method by adsorbing nitrogen on the abrasive particle surface. A larger surface area of ​​the particle can increase the contact area between the particle and the substrate, thereby improving the material removal rate. Therefore, the abrasive particles preferably have a surface area of ​​at least 2.1 m 2 / g, more preferably at least 6.4m 2 / g, more preferably at least 10.1m 2 / g, most preferably at least 16.3m2 The abrasive particles preferably have a BET surface area of ​​at most 94.7 m 2 / g, more preferably up to 81.2m 2 / g, more preferably up to 72.9m 2 / g, most preferably up to 60.6m 2 / g of BET surface area.

[0032] Preferably, the abrasive particles have a positive charge. Charge refers to the zeta potential, which can be measured, for example, using a Mastersizer S (Malvern Instruments). As known to those skilled in the art, the zeta potential of the abrasive particles in a composition refers to the electrical potential at the interface between the mobile fluid within the composition and the fluid stabilizing layer attached to the abrasive particles dispersed in the composition. A higher zeta potential results in stronger electrostatic repulsion between the particles, thereby increasing the stability of the particle dispersion in the composition. Preferably, the abrasive particles have a negative zeta potential in the composition at a pH of 6 to 7. Preferably, the abrasive particles have a zeta potential of at least -0.5 mV, more preferably at least -1 mV, more preferably at least -2 mV, and most preferably at least -3 mV in the composition at a pH of 6 to 7. Preferably, the abrasive particles have a zeta potential of at least -50 mV, more preferably at most -40 mV, more preferably at most -30 mV, and most preferably at most -20 mV in the composition at a pH of 6 to 7. Preferably, the abrasive particles 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, more preferably -3 mV to -20 mV in the composition at a pH of 6 to 7.

[0033] The composition further comprises 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. The oxidizing agent can specifically be an inorganic percompound, an organic percompound, 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.

[0034] Preferably, the oxidizing agent is an inorganic peroxide. The oxidizing agent can be present in the composition in any suitable form, such as an acid, a conjugate acid, a salt (e.g., a potassium salt, a sodium salt, an ammonium salt), or a combination thereof. The oxidizing agent according to the present invention can increase the material removal rate of the substrate during the polishing process.

[0035] Too low a concentration of the oxidizing agent can reduce the material removal rate of the substrate during the polishing process. Preferably, when used, the composition comprises 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 the oxidizing agent. Preferably, when used, the composition comprises 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 the oxidizing agent. In a preferred embodiment, when used, the composition comprises from 0.01 wt% to 15 wt%, more preferably from 0.06 wt% to 10 wt%, more preferably from 0.12 wt% to 8 wt%, more preferably from 0.28 wt% to 7 wt%, and most preferably from 0.51 wt% to 6 wt% of the oxidizing agent.

[0036] The composition also includes a complexing agent. The complexing agent can bind metal ions that may be formed during the chemical mechanical polishing process. Depending on the substrate being polished, the complexing agent can improve the material removal rate during the polishing process. Suitable complexing agents are dicarboxylic acids, polycarboxylic acids, amino acids, organic amines, aminocarboxylic acids, polyaminopolycarboxylic acids, phosphates, polyphosphates, organic phosphonic acids, phosphonocarboxylic acids, phenol derivatives, ketones, or combinations thereof. The complexing agent can be present in the composition in any suitable form, such as an acid, a conjugate acid, a salt (e.g., a potassium salt, a sodium salt, an ammonium salt), or a combination thereof.

[0037] 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, trimethyltetramine, and combinations thereof. Examples of aminopolycarboxylic acids include ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylene glycol diaminetetraacetic acid (EGTA), diethylenetriaminepentaacetic acid (DTPA), diaminohydroxypropanetetraacetic acid (DTPA-OH), triethylenetetraaminehexaacetic acid (TTHA), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), bisaminophenoxyethanetetraacetic acid (BAPTA), tetraxetan (DOTA), nicotinamide, ethylenediaminebishydroxyphenylacetic acid (EDDHA), nitrilotriacetic acid, and combinations thereof. Examples of organic phosphonic acids are ethylenediaminetetrakis(methylenephosphonic acid) (EDTMP), aminotris(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, ditolylenediphosphonic acid, diethylenetriaminepenta(methylenephosphonic acid), hexamethylenediamine-N,N,N',N'-tetrakis(methylphosphonic acid), bis(hexamethylenetriaminepenta(methylenephosphonic acid)), aminotris(methylenephosphonic acid)), methylphosphonic acid, (aminomethyl)phosphonic acid, nitrotrimethylenephosphonic acid, 4-amino-1- Hydroxybutane-1,1-diphosphonic acid, iminobis(methylphosphonic acid), (1-hydroxy-2-(1H-imidazol-1-yl)ethane-1,1-diyl)diphosphonic acid, ethylenediaminetetrakis(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, methanehydroxyphosphonic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, 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-diketone and the like.

[0038] Preferably, the complexing agent is an organic phosphonic acid. The organic phosphonic acid may have one, two, three, or more phosphonic acid groups. Preferably, the complexing agent is an organic diphosphonic acid. In a most preferred embodiment, the complexing agent is HEDP, an organic diphosphonic acid that complexes iron, copper, and zinc, exhibits excellent corrosion and scale inhibition properties, and exhibits good chemical stability at high pH values. The complexing agents of the present invention have been found to increase the material removal rate of substrates during CMP processing.

[0039] 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.

[0040] The composition comprises an aqueous carrier. The abrasive and chemical additives are suspended in the aqueous carrier. The aqueous carrier enables the abrasive and chemical additives to come into contact with the substrate and polishing pad during the CMP process. The aqueous carrier can be any component suitable for suspending the abrasive and the oxidizing agent. Examples of the aqueous carrier include water, ethers (such as dioxane 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.

[0041] The composition comprises a pH adjusting agent when used. The pH adjusting agent helps the composition achieve a suitable pH. The pH adjusting agent can be a base or a salt thereof. The base or salt thereof can be an organic base, an inorganic base, or a combination thereof.

[0042] 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.

[0043] Examples of organic bases are aliphatic amines, aromatic amines, quaternary ammonium hydroxides (eg, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH)), and combinations thereof.

[0044] 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 include the pH adjuster at a concentration suitable to achieve the pH of the present invention.

[0045] The composition may also optionally include a pH buffer. The pH buffer helps maintain a suitable pH for the composition. The pH buffer can be any suitable buffer. The pH buffer can be, for example, a phosphate, sulfate, acetate, borate, ammonium salt, or a combination thereof. The composition may include a pH buffer at a concentration suitable for maintaining the pH of the present invention.

[0046] The pH of the composition affects the removal rate of the substrate during the CMP process. Alkaline pH has been found to result in lower material removal rates, while acidic pH carries the risk of corrosion of iron and stainless steel components in chemical mechanical polishing equipment. Therefore, preferably, when used, the composition has a pH of at least 4.5, more preferably at least 5.0, more preferably at least 5.5, and most preferably at least 6.0. Preferably, when used, the composition has a pH of at most 8.5, more preferably at most 8.0, more preferably at most 7.5, and most preferably at most 7.0. In a preferred embodiment, when used, the composition has a pH in the range of 4.5 to 8.5, more preferably 5.0 to 8.0, more preferably 5.5 to 7.5, and most preferably 6.0 to 7.0.

[0047] The composition further comprises a dispersant, which helps to disperse the aluminum oxide abrasive particles and stabilize them in solution, thereby improving shelf life. The dispersant is preferably a nanoclay, polyacrylic acid, sodium dodecylbenzene sulfonate, tetrasodium pyrophosphate, sodium hexametaphosphate, or a combination thereof. In a particularly preferred embodiment, the dispersant is a nanoclay. As used herein, the term "nanoclay" refers to a clay having a z-average particle size of at most 1000 nm. The nanoclay can be any type of nanoclay, such as natural clay, synthetic clay, modified clay, or a combination thereof. Examples of nanoclays include kaolin (e.g., kaolinite, dickite, halloysite, and nacrite), montmorillonite (e.g., saponite, hectorite, laponite, nontronite, beidellite, magnesite, bentonite, andalusite, kyanite, sillimanite, kaolinite, metakaolin, mullite, aluminum silicate, dihydrate aluminum silicate, potassium aluminum silicate, sodium aluminum silicate, calcium aluminum silicate, aluminum oxide silicate, magnesium aluminum silicate, and boroaluminum silicate), illite (e.g., micas such as phlogopite, biotite, lepidolite, muscovite, and glauconite), chlorite, palygorskite, sepiolite, vermiculite, talc, pyrophyllite, modifications 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, hectorite, magnesium aluminum silicate, kaolinite, or combinations thereof.

[0048] For example, the nanoclay can be purchased from Shengxinxin Chemical Technology Co., Ltd. (Guangzhou, China).

[0049] The nanoclay-containing compositions of the present invention have been found to extend the shelf life of the compositions. The nanoclays of the present invention have also been found to reduce the drop in material removal rate during recycling.

[0050] Preferably, when used for polishing, the composition comprises 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 of the abrasive particles with the substrate surface, thereby reducing the material removal rate during the CMP process. Therefore, when used, the composition preferably comprises at most 15 wt%, more preferably at most 13 wt%, more preferably at most 12 wt%, more preferably at most 11 wt%, and most preferably at most 10 wt% of nanoclay. In a preferred embodiment, the composition comprises from 0.0001 wt% to 15 wt%, more preferably from 0.001 to 13 wt%, more preferably from 0.01 wt% to 12 wt%, more preferably from 0.03 wt% to 11 wt%, and most preferably from 0.05 wt% to 10 wt% of nanoclay.

[0051] The composition should have a 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.). The high viscosity of the composition can be achieved, for example, by the nanoclay of the present invention. It has been found that the viscosity of the present invention can reduce the aggregation and agglomeration of abrasive particles 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 at most 903 mPa*s, more preferably at most 80 mPa*s, and most preferably at most 70 mPa*s when measured as a 2% solution at 25°C.

[0052] Preferably, the nanoclay is negatively charged. The greater the absolute value of the negative zeta potential of the nanoclay, the more stable the dispersion. Preferably, the zeta potential of the nanoclay is at least -5 mV, preferably at least -10 mV, more preferably at least -15 mV, more preferably at least -20 mV, and most preferably at least -22 mV.

[0053] The zeta potential, particle size distribution and z-average particle size of the nanoclay can be measured by ultrasonically treating a 0.1 wt.% aqueous dispersion of the nanoclay at 25°C for 30 minutes. The zeta potential, particle size distribution and z-average particle size of the nanoclay are measured for the nanoclay in the aqueous dispersion, not the nanoclay in the composition. The zeta potential of the nanoclay can be measured by a Mastersizer S (Malvern Instruments Ltd., UK); the particle size distribution and z-average particle size can be measured by dynamic light scattering, for example, using a Zetasizer Nano ZSE (Malvern Instruments Ltd.); the z-average particle size refers to the intensity-weighted average hydrodynamic size of the particle ensemble measured by dynamic light scattering (for example, 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.

[0054] The inventors have found that nanoclays with a smaller z-average particle size can improve the dispersibility of aluminum oxide particles, extend the shelf life of the composition, reduce the number of pits on the substrate surface, and reduce surface roughness. It was found that nanoclays with a larger z-average particle size can cause aggregation and agglomeration of aluminum oxide abrasive particles, resulting in a greater increase in the D10, D30, D50, D70, and D90 of aluminum oxide measured in the composition, and the increase caused by this increase in surface roughness and surface defects (such as pits). The inventors have also found that nanoclays with nanometer size can improve the surface morphology of stainless steel, while nanoclays with micrometer size can deteriorate the apparent morphology of stainless steel. The nanoclay should have a suitable z-average particle size. Preferably, the nanoclay has 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, resulting in an adverse 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.

[0055] Experiments have shown that nanoclays with smaller D10 can achieve 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, the material removal rate will be reduced. 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 preferred embodiments, 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.

[0056] Experiments have shown that nanoclays with a smaller D30 can achieve 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 of the nanoclay can reduce 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.

[0057] Experiments have shown that nanoclays with a smaller D50 can achieve smaller surface roughness during CMP processing. Preferably, the nanoclay has a D50 of at most 1300nm, more preferably at most 1200nm, more preferably at most 1100nm, more preferably at most 1000nm, and more preferably at most 950nm as measured by dynamic light scattering. However, a smaller D50 of the nanoclay will reduce the material removal rate. Preferably, the nanoclay has a D50 of at least 0.1nm, more preferably at least 0.5nm, more preferably at least 1nm, more preferably at least 1.3nm, and most preferably at least 1.5nm as measured by dynamic light scattering. In a preferred embodiment, the nanoclay has a D50 of 0.1nm to 1300nm, more preferably 0.5nm to 1200nm, more preferably 1nm to 1100nm, more preferably 1.3nm to 1000nm, and most preferably 1.5nm to 950nm as measured by dynamic light scattering.

[0058] Experiments have shown that nanoclays with a smaller D70 can achieve 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 of the nanoclay can reduce 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.

[0059] Experiments have shown that nanoclays with a smaller D90 can achieve 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 of the nanoclay can reduce 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.

[0060] The increase in the D10, D30, D50, D70, and D90 of the alumina particles refers to the ratio of the particle size of the alumina particles in the composition to the particle size of the alumina particles in the aqueous dispersion (regardless of the composition's composition content), specifically as measured by laser diffraction, and specifically refers to the corresponding ratio of the particle size of the alumina particles measured in the composition to the particle size of the alumina particles measured in an alumina dispersion having an alumina concentration of 15 wt.% (85 wt.% water). The inventors have discovered that the nanoclays of the present invention can reduce the ratio of the increase in the D10, D30, D50, D70, and D90 of the alumina particles. Preferably, the ratio of the increase in the D10 of the alumina in the composition containing the nanoclay to the D10 of the alumina measured in an alumina dispersion having 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 ratio of the increase in D30 of the aluminum oxide in the composition to the D30 of the aluminum oxide measured in an aluminum oxide dispersion having an aluminum oxide concentration of 15 wt.% (85 wt.% water) is at most 4.2, preferably at most 3.5, more preferably at most 3, and more preferably at most 2.5. Preferably, the ratio of the increase in D50 of the aluminum oxide in the composition to the D50 of the aluminum oxide measured in an aluminum oxide dispersion having an aluminum oxide concentration of 15 wt.% (85 wt.% water) is at most 5.5, preferably at most 5, more preferably at most 4.5, and even more preferably at most 4. Preferably, the ratio of the increase in D70 of the aluminum oxide in the composition to the D70 of the aluminum oxide measured in an aluminum oxide dispersion having an aluminum oxide concentration of 15 wt.% (85 wt.% water) is at most 5.5, preferably at most 5, more preferably at most 4.5, and even more preferably at most 4. Preferably, the increased ratio of the D90 of alumina in the composition to the D90 of alumina measured in an alumina dispersion having an alumina concentration of 15 wt.% (85 wt.% water) is at most 5.5, preferably at most 5, further preferably at most 4.5, and most preferably at most 4.

[0061] The composition also optionally includes one or more preservatives. The preservative can be any suitable compound that prevents, inhibits, reduces growth, inhibits activity, or eliminates unwanted microorganisms. Examples of suitable preservatives include sodium hypochlorite, methylisothiazolinone, benzisothiazolinone, chloromethylisothiazolinone, and combinations thereof. Preferably, the composition includes at least 0.6ppm by weight, more preferably at least 1.6ppm by weight, more preferably at least 2.7ppm by weight, more preferably at least 3.8, most preferably at least 4.6ppm by weight of preservative. High concentrations of preservatives can cause undesirable interactions between the preservative and other components of the composition and the substrate. Therefore, the composition preferably includes at most 98ppm by weight, more preferably at most 83ppm by weight, more preferably at most 74ppm by weight, most preferably at most 69ppm by weight of preservative. Ppm used herein refers to ppm by weight.

[0062] Preferably, the composition is substantially free of polymers. The polymer can be any polymer. Typically, polymers are used in CMP compositions containing aluminum oxide to improve the dispersibility of the aluminum oxide particles, thereby increasing the shelf life of the composition, and to prevent particle aggregation, which can lead to defects on the substrate surface. However, during the CMP polishing process, polymers typically reduce the material removal rate of the substrate. Surprisingly, it was found that the composition according to the present invention caused fewer defects in the substrate surface, even in the absence of polymers.

[0063] As used herein, the term "substantially free of component X" refers to a composition that does not substantially contain the component X, ie, 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.

[0064] The present invention also provides a method for chemical mechanical polishing of a substrate, comprising the following steps: (a) providing a chemical mechanical polishing composition; (b) contacting the substrate with the chemical mechanical polishing composition and a polishing pad; (c) moving the polishing pad relative to the substrate with the chemical mechanical polishing composition positioned therebetween; and (d) removing at least a portion of the substrate. The CMP composition provided in step (a) is a composition of the present invention. The method may optionally include other steps.

[0065] 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 appropriate 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 regulators and pH buffers 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 the CMP process.

[0066] The composition can be provided as a one-part system, a two-part system, or a multi-part system. For example, as a two-part system, the first part can include abrasive particles and one or more chemical additives, and the second part can include nanoclay and one or more other chemical additives. The first and second parts can be mixed at any time before the CMP process (e.g., one month, one day, one hour, or one minute) or during the CMP process, such as when using a polishing apparatus having multiple supply paths for the CMP composition.

[0067] The composition can be provided as a concentrate and can be diluted with a suitable amount of water before use. The concentration of the components in the composition can be any suitable concentration, for example, 2 times, 3 times, 10 times, or 25 times the above-mentioned concentrations for use. For example, the concentrate can contain the abrasive and chemical additives at concentrations such that, upon dilution with a suitable amount of water, the abrasive and chemical additives are present in the composition at the above-mentioned concentrations. 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 at different concentrations, for example, the first part at a concentration of three times and the second part at a concentration of five times. The two parts can be diluted in any order before mixing.

[0068] The composition should achieve high material removal rates during CMP processing of substrates comprising 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 of substrates comprising ferrous metal alloys during CMP processing.

[0069] The present invention also relates to uses of the compositions of the present invention. The compositions of the present invention can be used to polish a variety of materials. Preferably, the compositions of the present invention are used for chemical mechanical polishing of substrates comprising one or more 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 a process in which a substrate is placed in a CMP apparatus and brought into contact with a polishing pad and a CMP composition positioned therebetween. The polishing pad and substrate are moved relative to each other to remove portions of the substrate.

[0070] For some materials such as metals, metal alloys, metal oxides, and minerals, the compositions are used in a final polishing step, while for other materials such as ceramics and plastics, the compositions are used in intermediate polishing steps.

[0071] Examples of metals, metal alloys, and metal oxides that can be polished with the compositions of the present invention include iron, iron alloys (e.g., steel), aluminum, aluminum alloys, titanium, titanium alloys, nickel, nickel alloys, copper, copper alloys, Kovar, cupronickel, Inconel, brass, niobium, bronze, nickel silver, beryllium, monel, vanadium, Hastelloy, tantalum, silver, gold, molybdenum, Nimonic alloys, Waspaloy alloys, tungsten, ceramics, and combinations thereof. The metal oxides can be in the form of single crystals, polycrystalline, sintered bodies (ceramics), or combinations thereof.

[0072] In a particularly preferred embodiment, the present invention is used for chemical mechanical polishing of a substrate comprising a metal alloy. The metal alloy may comprise a metal as its main component and at least one metal different from the main component. The number of metal species different from the main component is not limited and may be, for example, two, three or more. Preferably, the metal that is 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 species is iron. Examples of iron alloys include stainless steel, carbon steel, alloy steel, leaded steel, tool steel, cast steel, maraging steel, cast iron and combinations thereof.

[0073] The present application is described in detail below through specific embodiments.

[0074] Example 1

[0075] The stainless steel material removal rate, surface roughness, and surface defects of the polished products of composition A1 and compositions E1-E7 were evaluated. Composition A1 and compositions E1-E7 each contained 15 wt.% of aluminum oxide abrasive particles, 1 wt.% of hydrogen peroxide, 1 wt.% of hectorite having a z-average particle size of 61.75 nm and a zeta potential of -31 mV, and 30 ppm (by weight) of the corrosion inhibitor KATHON TM LX150 (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 composition of which is shown in Table 1.

[0076] The z-average particle size of the magnesium aluminum silicate was measured by dynamic light scattering using a Zetasizer Nano ZSE (Malvern Instruments Ltd., UK) from a 0.1 wt% dispersion, and the D50 was obtained as described above. The zeta potential of the nanoclay was measured using a Mastersizer S (Malvern Instruments Ltd., UK) from a 0.1 wt% aqueous dispersion. Prior to measuring the z-average particle size and zeta potential, the aqueous magnesium aluminum silicate dispersion was sonicated for 30 minutes at 25°C to obtain a homogenous dispersion.

[0077] As described above, before the aluminum oxide abrasive particles were added to the composition, the D30, D50, D70, and D90 of the aluminum oxide abrasive particles were obtained by laser diffraction in an 85 wt.% aqueous solution using a Horiba LA960. After the aluminum oxide particles were dispersed, the D30, D50, D70, and D90 of the aluminum oxide 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 aluminum oxide abrasive particles dispersed in the composition to the corresponding particle size of the aluminum oxide abrasive particles dispersed in the 85 wt.% aqueous solution.

[0078] A Nano-Max polishing tool (Shenzhen Nanos Precision Machinery Technology Co., Ltd.) was used to polish the surface of the 9 cm2 surface with a platen speed of 80 rpm, a down force of 2.0 psi, and a slurry flow rate of 100 ml / min. 2 , a stainless steel plate with a thickness of 3 mm was polished for 4 minutes.

[0079] The polished stainless steel plates were visually inspected for surface defects, and the 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 plates was measured using an electronic balance, and the weight difference before and after polishing was calculated. The material removal rate is listed in Table 1 as a percentage of the material removal rate of composition A1. The surface roughness (average roughness, Ra) was measured using an SJ-410 surface roughness tester (Mitutoyo Corp) at a measuring length of 25 mm and is listed in Table 1. As known to those skilled in the art, surface roughness is the arithmetic mean of the absolute value of the deviation of the profile height from the average height within the measuring length. In addition, all surface roughness values ​​below 0.02 can be considered good.

[0080] Table 1

[0081] As shown in Table 1, compositions E1-E7 containing different complexing agents achieved higher removal rates than A1, which did not contain a complexing agent. Furthermore, E5, which used only HEDP as a complexing agent, showed no pitting and the lowest surface roughness. Compositions E1-E4 and E6-E7, which used other complexing agents, did not perform as well.

[0082] Example 2

[0083] Composition A2 and compositions E8-E11 were evaluated for stainless steel material removal rate, surface roughness, and surface defects. Composition A2 and compositions E8-E11 included 15 wt.% aluminum oxide abrasive particles, 2 wt.% 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), 1 wt.% bentonite having 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 contained 1 wt.% of an oxidizing agent as shown in Table 2.

[0084] Before polishing, the zeta potential of the aluminum oxide particles in the composition was measured using a Mastersizer S (Malvern Instruments Ltd., UK). The stainless steel plates were polished and their 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] 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.

[0087] Example 3

[0088] Compositions A3-A4 and E12 were evaluated for stainless steel material removal rate, surface roughness, and surface defects. Compositions A3-A4 and E12 included 15 wt.% aluminum oxide abrasive particles, 1 wt.% hydrogen peroxide, 2 wt.% 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), 1 wt.% magnesium aluminum silicate having 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 have different pH values ​​using KOH, as shown in Table 3.

[0089] The stainless steel plate was polished and its relative removal rate, surface roughness and pits were measured as described in Example 1. The results are shown in Table 3.

[0090] Static corrosion of stainless steel by each composition was evaluated by measuring the weight of the stainless steel plate. The stainless steel plate was first weighed, then placed in the composition, heated to 60°C, and allowed to stand for 5 hours. The plate was then weighed again. The difference in weight (weight loss due to corrosion) was defined as static corrosion.

[0091] Table 3

[0092] As can be seen from Table 3, the composition with an 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 a 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.

[0093] Example 4

[0094] Compositions A5-A9 and E13-E18 were evaluated for stainless steel material removal rate, surface roughness, and surface defects. Compositions A5-A9 and E13-E18 included 15 wt.% aluminum oxide 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 TMLX150 (Dow Inc.). The pH value of these compositions was 6.5. Except for A5, all other compositions also contained 1 wt.% of the nanoclays listed in Table 4. Before adding the nanoclays to the compositions, the zeta potential and z-average 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.

[0095] The stainless steel plates were polished and the relative removal rate, surface roughness, and pitting were measured as described in Experiment 1. The results are shown in Table 4.

[0096] The shelf life of compositions A5-A9 and E13-E18 was evaluated by placing 500 mL of each composition into a 500 mL polyethylene bottle and allowing it to stand at room temperature without stirring. "Shelf life" was defined as the time from the start of standing until the composition settled and formed a hard cake that was difficult to redisperse. The results of the shelf life evaluation are shown in Table 4.

[0097] Table 4

[0098] From Table 4 we can see that:

[0099] Although the relative removal rates of compositions E13 and E14 containing magnesium aluminum silicate with nanoclay z-average particle size less than 1000 nm were not the highest, they exhibited lower surface roughness and no pits. Among them, composition E13 containing magnesium aluminum silicate with nanoclay z-average particle size less than 100 nm exhibited higher relative removal rate, good surface roughness and no pits. Compositions E15-18 containing bentonite and hectorite with nanoclay z-average particle size less than 1000 nm exhibited lower surface roughness and no pits. Among them, composition E17 containing bentonite and hectorite with nanoclay z-average particle size less than 100 nm exhibited good surface roughness and no pits.

[0100] The shelf life was determined by observing the compositions at room temperature. For composition A5, which did not contain nanoclay, the aluminum oxide settled after 5 days and formed a hard cake that was difficult to redisperse. Compositions A6-A9 and E13-E18, all containing nanoclay, were observed for up to 9 months and remained dispersed (not settled) after 9 months. No further observation of the compositions was performed after 9 months.

[0101] 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 in the scope of protection of the present invention.

Claims

1. A chemical mechanical polishing composition for a metal alloy surface, comprising aluminum oxide abrasive particles, an oxidizing agent, a dispersant and a pH regulator, wherein: The dispersant is a nanoclay having a z-average particle size of at most 1000 nm.

2. The composition according to claim 1, characterized in that The nanoclay has a zeta potential of at least -5 mV.

3. The composition according to claim 1, characterized in that The aluminum oxide abrasive particles have a negative zeta potential in the composition at a pH of at least 5.

0.

4. The composition according to claim 1, characterized in that The oxidant is an inorganic peroxide compound, an organic peroxide compound, or a combination thereof.

5. The composition according to claim 1, characterized in that 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 organic phosphonic acid, a phosphonocarboxylic acid, a phenol derivative, a ketone, or a combination thereof.

6. The composition according to claim 5, characterized in that The complexing agent is an organic phosphonic acid.

7. The composition according to any one of claims 5 to 6, characterized in that The composition comprises 0.1 wt% to 33.3 wt% of a complexing agent.

8. The composition according to claim 1, characterized in that The composition comprises 0.0001 wt % to 15 wt % of nanoclay.

9. The composition according to claim 1, characterized in that The pH adjuster is an alkali metal hydroxide, a quaternary ammonium hydroxide, an alkali metal carbonate, or a combination thereof.

10. A polishing method for a metal alloy substrate, the method being achieved by using the composition according to any one of claims 1 to 9.

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