Polishing composition and polishing method

Abstract

To provide a polishing composition capable of performing polishing such that the surface of an object to be polished after polishing has extremely high smoothness.SOLUTION: A polishing composition includes colloidal silica and hydrogen peroxide, and the colloidal silica has an average secondary particle diameter of less than 80 nm and a degree of association of 1.5 or more, and the pH of the polishing composition is 5 or more, and the colloidal silica in the polishing composition has a negative zeta potential.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polishing composition and a polishing method. [Background technology]

[0002] In recent years, with the increasing number of multilayer wirings on semiconductor substrate surfaces, so-called chemical mechanical polishing (CMP) technology, which physically polishes and flattens semiconductor substrates, has come to be used in device manufacturing. CMP is a method of flattening the surface of an object to be polished (workpiece) such as a semiconductor substrate using a polishing composition (slurry) containing abrasive grains such as silica, alumina, or ceria, an anticorrosive agent, a surfactant, etc. The object to be polished (workpiece) can be silicon, polysilicon, silicon oxide film (silicon oxide), silicon nitride, or wiring or plug made of metal, etc.

[0003] For example, as a technique for polishing metal for wiring portions, Patent Document 1 discloses a CMP polishing liquid containing (A) an oxidized metal dissolving agent, (B) abrasive grains that have a positive charge in the CMP polishing liquid, (C) a metal corrosion inhibitor, and (D) an oxidizing agent, and having a pH of 2.8 to 4.0. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-134358 Summary of the Invention [Problem to be solved by the invention]

[0005] Recently, in the technology for joining metal materials to each other or to other materials, a new requirement has arisen: that the surfaces of the metal materials to be joined be polished to have extremely high smoothness (for example, an arithmetic mean height Sa of 1.70 nm or less). Up until now, little consideration has been given to such a requirement.

[0006] Therefore, an object of the present invention is to provide a polishing composition that can polish an object so that the surface of the object to be polished has extremely high smoothness after polishing. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the above problems can be solved by a polishing composition comprising colloidal silica and hydrogen peroxide, wherein the colloidal silica has an average secondary particle size of less than 80 nm and a degree of association of 1.5 or more, the pH of the polishing composition is 5 or more, and the zeta potential of the colloidal silica in the polishing composition is negative, thereby completing the present invention. [Effects of the Invention]

[0008] According to the present invention, there is provided a polishing composition that can polish an object so that the surface of the object to be polished has extremely high smoothness after polishing. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention relates to a polishing composition comprising colloidal silica and hydrogen peroxide, wherein the colloidal silica has an average secondary particle diameter of less than 80 nm and a degree of association of 1.5 or more, the pH of the polishing composition is 5 or more, and the zeta potential of the colloidal silica in the polishing composition is negative. The polishing composition according to one embodiment of the present invention having such a configuration can polish an object so that the surface thereof has extremely high smoothness after polishing.

[0010] The mechanism by which the polishing composition of the present invention provides the above-described effects is believed to be as follows: However, the following mechanism is merely speculation, and the scope of the present invention is not limited thereby.

[0011] Metal materials suitable for polishing have multiple regions with different plane orientations on the polishing surface. These regions have different hardnesses and therefore differ in ease of polishing. The colloidal silica contained in the polishing composition of the present invention has an association degree of 1.5 or more, which makes it difficult for rolling to occur and increases the mechanical polishing force to a certain extent. Furthermore, hydrogen peroxide oxidizes the surface of the metal material, facilitating polishing with the colloidal silica. Therefore, even if there are regions with different plane orientations, polishing can be performed approximately uniformly. Furthermore, the average secondary particle diameter of the colloidal silica contained in the polishing composition of the present invention is less than 80 nm, which allows polishing without excessively increasing the polishing rate and makes it easier to obtain a polished surface with high flatness.

[0012] Furthermore, the colloidal silica has a negative zeta potential in a polishing composition having a pH of not less than 5. In a pH range of not less than 5, the surface of the metal material (polished surface) is negatively charged, and therefore, due to electrical repulsion, the colloidal silica does not act excessively on the polished surface, making it possible to obtain a polished surface with extremely high flatness.

[0013] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0014] In this specification, unless otherwise specified, operations and measurements of physical properties are carried out at room temperature (20° C. or higher and 25° C. or lower) and at a relative humidity of 40% RH or higher and 50% RH or lower.

[0015] [Polished object] The object to be polished according to the present invention is not particularly limited, but preferably contains a metal material. That is, according to a preferred embodiment of the present invention, the polishing composition according to the present invention is used for polishing an object to be polished that contains a metal material.

[0016] The metal material is not particularly limited and may be, for example, various metal elements, alloys of these elements with one or more other elements, etc. Typical examples of metal elements include magnesium (Mg), aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), zirconium (Zr), gold (Au), silver (Ag), platinum (Pt), iridium (Ir), bismuth (Bi), niobium (Ni), molybdenum (Mo), tin (Sn), tungsten (W), and lead (Pb).

[0017] Examples of alloys include copper alloys such as Cu-Al alloy, Cu-Al-Fe alloy, Cu-Ni alloy, and Cu-Ni-In alloy; nickel alloys such as Ni-Al alloy, Ni-Cr alloy (e.g., Ni-20Cr alloy, Ni-50Cr alloy, and Inconel), Ni-Cr-Fe alloy (e.g., Incoloy), Ni-Cr-Al alloy, Hastelloy (Ni-Fe-Mo alloy, Ni-Cr-Mo alloy), and Ni-Cu alloy (e.g., Monel); cobalt alloys such as Co-Cr-W alloy (e.g., Stellite), Co-Cr-Ni-WC alloy, Co-Mo-Cr-Si alloy, and Co-Cr-Al-Y alloy; carbon steel; stainless steels such as SUS304, SUS316, SUS410, SUS420J2, and SUS431; and titanium alloys such as Ti-6Al-4V. The term "alloy" as used herein refers to a substance that is composed of the above-mentioned metal elements and one or more other elements and exhibits metallic properties, and the mixture may be in the form of a solid solution, an intermetallic compound, or a composite of these.

[0018] The above-mentioned metal elements and alloys may be contained alone or in combination of two or more.

[0019] Among these, the metal material is preferably copper or a copper alloy, from the viewpoint of more easily achieving the effects of the present invention.

[0020] The object to be polished according to the present invention may further contain other materials in addition to the metal material, such as silicon nitride, silicon oxide, single crystal silicon, polycrystalline silicon (polysilicon), amorphous silicon, polycrystalline silicon doped with n-type or p-type impurities, amorphous silicon doped with n-type or p-type impurities, and titanium nitride.

[0021] Examples of polishing objects containing silicon oxide include TEOS (Tetraethyl Orthosilicate) type silicon oxide surfaces (hereinafter also referred to as "TEOS" or "TEOS film") produced using tetraethyl orthosilicate as a precursor, HDP (High Density Plasma) films, USG (Undoped Silicate Glass) films, PSG (Phosphorus Silicate Glass) films, BPSG (Boron-Phospho Silicate Glass) films, and RTO (Rapid Thermal Oxidation) films.

[0022] The surface of the object to be polished after polishing with the polishing composition of the present invention has extremely high smoothness, and is therefore preferably used for polishing joining members used to join metal materials together or to join metal materials to other materials. When extremely smooth surfaces are joined, atomic rearrangement occurs at the joining interface, allowing the materials to be joined without the use of adhesives such as grease or solder. Examples of such joining include joining a metal substrate (especially a copper substrate) to a ceramic substrate to improve the heat dissipation of a semiconductor substrate, joining lithium tantalate or lithium niobate to a support substrate such as silicon, glass, or sapphire to improve the frequency-temperature characteristics of a SAW device, and Cu-Cu joining to improve the conductivity of a semiconductor device.

[0023] [Colloidal silica] The polishing composition of the present invention contains colloidal silica, which has the effect of mechanically polishing an object to be polished.

[0024] Methods for producing colloidal silica include the sodium silicate method and the sol-gel method. Colloidal silica produced by either method is suitable for use as the colloidal silica of the present invention. However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferred. Colloidal silica produced by the sol-gel method is preferred because it contains less metal impurities that tend to diffuse in semiconductors and less corrosive ions such as chloride ions. Colloidal silica can be produced by the sol-gel method using a conventionally known method. Specifically, colloidal silica can be obtained by hydrolysis and condensation reaction using a hydrolyzable silicon compound (e.g., alkoxysilane or its derivative) as a raw material. Commercially available colloidal silica may also be used.

[0025] The shape of the colloidal silica is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and quadrangular prisms, cylinders, bale-shaped cylinders in which the center is bulged more than the ends, doughnut-shaped discs with a hole in the center, plates, cocoons with a central constriction, associative spheres in which multiple particles are integrated, confetti-shaped colloids with multiple protrusions on the surface, and rugby ball-shaped colloids, and are not particularly limited.

[0026] <Average secondary particle diameter> The colloidal silica according to the present invention has an average secondary particle diameter of less than 80 nm. If the average secondary particle diameter is 80 nm or more, the flatness of the surface of the object to be polished will decrease. The average secondary particle diameter is preferably 70 nm or less, and more preferably 60 nm or less.

[0027] The lower limit of the average secondary particle size of colloidal silica is not particularly limited, but from the viewpoint of more easily achieving the effects of the present invention, it is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. The average secondary particle size of colloidal silica can be measured, for example, by a dynamic light scattering method represented by a laser diffraction scattering method, and more specifically, by the method described in the Examples.

[0028] <Average degree of association> The average degree of association of the colloidal silica according to the present invention is 1.5 or more. If the average degree of association is less than 1.5, the smoothness of the surface of the object to be polished decreases. The average degree of association is preferably 1.55 or more, more preferably 1.57 or more, and even more preferably 1.6 or more. The upper limit of the average degree of association of the colloidal silica is not particularly limited, but is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.0 or less. That is, the average degree of association of the colloidal silica is preferably 1.55 or more and 4.0 or less, more preferably 1.57 or more and 3.5 or less, and even more preferably 1.6 or more and 3.0 or less.

[0029] The average degree of association can be obtained by dividing the average secondary particle size of colloidal silica by the average primary particle size. The average primary particle size of colloidal silica can be calculated, for example, based on the specific surface area of ​​colloidal silica calculated by the BET method, assuming that the colloidal silica has a spherical shape. More specifically, it can be measured by the method described in the Examples.

[0030] The size of the colloidal silica (average secondary particle size, average degree of association, etc.) can be appropriately controlled by selecting the method for producing the colloidal silica, etc.

[0031] <Zeta potential> In the polishing composition of the present invention, the colloidal silica has a negative zeta potential. Here, the "zeta (ζ) potential" refers to the potential difference that occurs at the interface between a solid and a liquid when they are in contact with each other and undergo relative motion.

[0032] If the zeta potential of the colloidal silica in the polishing composition of the present invention is 0 mV or positive, it becomes more accessible to the object to be polished, including metal materials, causing polishing to proceed more than necessary and reducing the flatness of the surface of the object to be polished after polishing.

[0033] In the polishing composition of the present invention, as long as the colloidal silica has a negative zeta potential, the colloidal silica may have cationic groups on its surface. That is, the colloidal silica may be cation-modified colloidal silica (cation-modified colloidal silica). Preferred examples of cation-modified colloidal silica include colloidal silica with amino groups fixed to its surface. Examples of methods for producing colloidal silica with such cationic groups include those described in Japanese Patent Laid-Open No. 2005-162533, in which a silane coupling agent having an amino group, such as aminoethyltrimethoxysilane, aminopropyltrimethoxysilane, aminoethyltriethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, or aminobutyltriethoxysilane, is fixed to the surface of silica particles. This method allows for the production of colloidal silica with amino groups fixed to its surface (amino-modified colloidal silica).

[0034] In addition, as long as the colloidal silica in the polishing composition of the present invention has a negative zeta potential, the colloidal silica of the present invention may have anionic groups on its surface. That is, the colloidal silica may be anion-modified colloidal silica (anion-modified colloidal silica). Preferred examples of anion-modified colloidal silica include colloidal silica having anionic groups such as carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, and aluminic acid groups fixed to its surface. The method for producing such colloidal silica having anionic groups is not particularly limited, and examples thereof include a method of reacting colloidal silica with a silane coupling agent having an anionic group at its terminal.

[0035] As a specific example, sulfonic acid groups can be immobilized on colloidal silica by the method described in "Sulfonic acid-functionalized silica through thiol groups," Chem. Commun. 246-247 (2003). Specifically, colloidal silica with sulfonic acid groups immobilized on its surface (sulfonic acid-modified colloidal silica) can be obtained by reacting colloidal silica with a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, and then oxidizing the thiol group with hydrogen peroxide.

[0036] Carboxylic acid groups can be immobilized on colloidal silica by, for example, the method described in "Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel," Chemistry Letters, 3, 228-229 (2000). Specifically, colloidal silica having carboxylic acid groups immobilized on the surface (carboxylic acid-modified colloidal silica) can be obtained by coupling a silane coupling agent containing a photolabile 2-nitrobenzyl ester to colloidal silica and then irradiating the silica with light.

[0037] However, the anionic or cationic groups of colloidal silica may act as a chelating agent on the surface of the object to be polished, resulting in non-uniform polishing and a decrease in the flatness of the surface of the object to be polished. Furthermore, in the pH range of the polishing composition of the present invention, the surface of the object to be polished, including metal materials, may have a negative zeta potential. Therefore, the positively charged cation-modified colloidal silica may act excessively on the surface of the object to be polished, resulting in a decrease in the flatness of the surface of the object to be polished after polishing. From these viewpoints, the colloidal silica is preferably unmodified colloidal silica or anion-modified colloidal silica, and more preferably unmodified colloidal silica.

[0038] More specifically, the zeta potential of the colloidal silica in the polishing composition is preferably less than 0 mV, more preferably -1 mV or less, even more preferably -5 mV or less, and even more preferably -20 mV or less. The zeta potential of the colloidal silica is preferably -100 mV or more, more preferably -80 mV or more, and even more preferably -60 mV or more.

[0039] Here, the zeta potential of the colloidal silica in the polishing composition is calculated by subjecting the polishing composition to an ELS-Z2 manufactured by Otsuka Electronics Co., Ltd., measuring the composition by a laser Doppler method (electrophoretic light scattering measurement method) using a flow cell at a measurement temperature of 25° C., and analyzing the obtained data using the Smoluchowski equation. The zeta potential of the colloidal silica can be adjusted by the amount of functional groups possessed by the colloidal silica, the pH of the polishing composition, etc.

[0040] In one embodiment of the present invention, the content (concentration) of colloidal silica may be 0.5 mass% or more, 1 mass% or more, 2 mass% or more, 3 mass% or more, 4 mass% or more, 5 mass% or more, 6 mass% or more, 7 mass% or more, 8 mass% or more, 9 mass% or more, 10 mass% or more, 11 mass% or more, 12 mass% or more, 13 mass% or more, 14 mass% or more, 15 mass% or more, 16 mass% or more, 17 mass% or more, 18 mass% or more, 19 mass% or more, or 20 mass% or more, relative to the total mass of the polishing composition. Furthermore, in one embodiment of the present invention, the content (concentration) of colloidal silica may be 40 mass% or less, 35 mass% or less, 30 mass% or less, 28 mass% or less, 26 mass% or less, 25 mass% or less, 23 mass% or less, 20 mass% or less, 19 mass% or less, 18 mass% or less, 17 mass% or less, 16 mass% or less, 15 mass% or less, 14 mass% or less, 13 mass% or less, 12 mass% or less, 11 mass% or less, 10 mass% or less, 9 mass% or less, 8 mass% or less, 7 mass% or less, 6 mass% or less, or 5 mass% or less, relative to the total mass of the polishing composition.

[0041] When the polishing composition contains two or more types of colloidal silica, the content of colloidal silica means the total amount of these.

[0042] The polishing composition of the present invention may further contain abrasive particles other than colloidal silica, provided that the effects of the present invention are not impaired. Such other abrasive particles may be inorganic particles, organic particles, or organic-inorganic composite particles. Specific examples of inorganic particles include unmodified silica, particles made of metal oxides such as alumina, ceria, and titania, silicon nitride particles, silicon carbide particles, and boron nitride particles. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles. The other abrasive particles may be used alone or in combination of two or more types. Furthermore, the other abrasive particles may be commercially available products or synthetic products.

[0043] However, the content of the other abrasive grains is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less, based on the total mass of the colloidal silica and the other abrasive grains. The most preferred embodiment is one in which the content of the other abrasive grains is 0% by mass, i.e., one in which no abrasive grains other than colloidal silica are included.

[0044] [hydrogen peroxide] The polishing composition of the present invention contains hydrogen peroxide. Hydrogen peroxide acts as an oxidizing agent that oxidizes the surface of the object to be polished, improving the flatness of the surface. Furthermore, hydrogen peroxide does not generate hydrogen ions after oxidizing the surface of the object to be polished. Therefore, hydrogen peroxide does not change or barely changes the pH or electrical conductivity in the system, which is advantageous in that it can further improve the flatness of the surface of the object to be polished.

[0045] The content of hydrogen peroxide is not particularly limited, but is preferably 0.03 mass% or more, more preferably 0.1 mass% or more, and even more preferably 0.3 mass% or more, based on the total mass of the polishing composition. The content of hydrogen peroxide is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 2 mass% or less, based on the total mass of the polishing composition.

[0046] That is, in the polishing composition according to one embodiment of the present invention, the content of hydrogen peroxide is preferably 0.03% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 3% by mass or less, and even more preferably 0.3% by mass or more and 2% by mass or less, relative to the total mass of the polishing composition.

[0047] <Other oxidizing agents> The polishing composition of the present invention may further contain an oxidizing agent other than hydrogen peroxide. Examples of such oxidizing agents include nitric acid, sodium peroxide, barium peroxide, peroxodisulfuric acid, peroxolinic acid, peroxosulfuric acid, peroxoboric acid, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, perchloric acid, chloric acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, perbromic acid, bromic acid, hypobromous acid, orthoperiodic acid, metaperiodic acid, iodic acid, hypoiodous acid, potassium permanganate, metal potassium chromate, and potassium dichromate. These other oxidizing agents may be used alone or in combination. Furthermore, commercially available or synthetic products may be used as the other oxidizing agents.

[0048] However, if a large amount of halogen-containing ions are present in the system, the flatness of the surface of the object to be polished may be reduced. Therefore, it is preferable that the polishing composition of the present invention is substantially free of an oxidizing agent containing halogen-containing ions. Here, "substantially free of an oxidizing agent containing halogen-containing ions" not only means that the polishing composition does not contain any oxidizing agent containing halogen-containing ions at all, but also includes the case where the polishing composition contains 0.05 mass% or less of the oxidizing agent containing halogen-containing ions. The content of the oxidizing agent containing halogen-containing ions is more preferably 0.01 mass% or less, even more preferably 0.005 mass% or less, based on the total mass of the polishing composition, and most preferably 0 mass%, i.e., no oxidizing agent containing halogen-containing ions at all.

[0049] [pH and pH adjusters] The pH of the polishing composition of the present invention is 5 or higher. If the pH is less than 5, the flatness of the surface of the object to be polished will decrease. The pH is preferably 5.5 or higher, more preferably 6.0 or higher, and even more preferably 6.5 or higher. The pH is preferably 14.0 or lower, more preferably 13.0 or lower, even more preferably 12.0 or lower, even more preferably 11.0 or lower, and particularly preferably 10.0 or lower, and may be, for example, 9.5 or lower. That is, the pH of the polishing composition of the present invention is preferably 5.5 or higher and 14.0 or lower, more preferably 6.0 or higher and 13.0 or lower, even more preferably 6.5 or higher and 12.0 or lower, even more preferably 6.5 or higher and 11.0 or lower, and particularly preferably 6.5 or higher and 10.0 or lower, and may be, for example, 6.5 or higher and 9.5 or lower.

[0050] The polishing composition of the present invention may contain a pH adjuster for adjusting the pH. The pH adjuster may be any of an inorganic acid, an organic acid, and a base, and may also be any of an inorganic compound and an organic compound. The pH adjuster may be used alone or in combination of two or more.

[0051] Specific examples of inorganic acids that can be used as pH adjusters include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Among these, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid are preferred.

[0052] Specific examples of organic acids that can be used as pH adjusters include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, and phenoxyacetic acid. Sulfur-containing acids such as methanesulfonic acid, ethanesulfonic acid, and isethionic acid may also be used.

[0053] Instead of or in combination with inorganic or organic acids, salts such as alkali metal salts of inorganic or organic acids may be used as pH adjusters. Combinations of a weak acid and a strong base, a strong acid and a weak base, or a weak acid and a weak base can be expected to have a pH buffering effect.

[0054] Specific examples of bases that can be used as pH adjusters include ammonia, sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, etc. The amount of pH adjuster added is not particularly limited, and may be appropriately adjusted so that the polishing composition has a desired pH.

[0055] However, as explained in the section on other oxidizing agents above, if a large amount of halogen-containing ions are present in the system, the flatness of the surface of the object to be polished may be reduced. Therefore, it is preferable that the polishing composition of the present invention is substantially free of a pH adjuster containing halogen-containing ions. Here, "substantially free of a pH adjuster containing halogen-containing ions" not only means that the polishing composition does not contain any pH adjuster containing halogen-containing ions at all, but also includes the case where the polishing composition contains 100 ppm or less of the pH adjuster containing halogen-containing ions. The content of the pH adjuster containing halogen-containing ions is more preferably 80 ppm or less, even more preferably 60 ppm or less, and particularly preferably 50 ppm or less, based on the total mass of the polishing composition. 0 ppm, i.e., no pH adjuster containing halogen-containing ions at all, is most preferable.

[0056] From the above viewpoint, the pH adjuster is preferably sulfuric acid, nitric acid, boric acid, potassium hydroxide, or sodium hydroxide.

[0057] The pH of the polishing composition can be measured, for example, with a pH meter, specifically by the method described in the Examples.

[0058] [Dispersion medium] The polishing composition of the present invention preferably contains a dispersion medium for dispersing each component. Examples of dispersion mediums include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Of these, water is preferred as the dispersion medium. That is, according to a preferred embodiment of the present invention, the dispersion medium contains water. According to a more preferred embodiment of the present invention, the dispersion medium consists essentially of water. Note that the above term "substantially" means that a dispersion medium other than water may be included as long as the intended effect of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% by mass to 100% by mass of water and 0% by mass to 10% by mass of a dispersion medium other than water, and more preferably 99% by mass to 100% by mass of water and 0% by mass to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0059] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, it is preferable that the dispersion medium be water that contains as few impurities as possible. Specifically, pure water or ultrapure water that has had impurity ions removed using an ion exchange resin and then passed through a filter to remove foreign matter, or distilled water, is more preferable.

[0060] [Other ingredients] The polishing composition of the present invention may further contain known additives that can be used in polishing compositions, such as complexing agents, preservatives, and antifungal agents, within the range that does not impair the effects of the present invention. Complexing agents and anticorrosive agents will be described below.

[0061] <Complexing agent> The complexing agent has the effect of chemically etching the surface of the object to be polished. Examples of the complexing agent include inorganic acids or their salts, organic acids or their salts, nitrile compounds, amino acids, and chelating agents. These complexing agents may be used alone or in combination of two or more. Furthermore, the complexing agent may be a commercially available product or a synthetic product.

[0062] More specific examples of the complexing agent include salt compounds such as sodium sulfate, potassium nitrate, potassium carbonate, potassium tetrafluoroborate, potassium pyrophosphate, potassium oxalate, trisodium citrate, (+)-potassium tartrate, and potassium hexafluorophosphate; nitrile compounds such as acetonitrile, aminoacetonitrile, propionitrile, butyronitrile, isobutyronitrile, benzonitrile, glutaronitrile, and methoxyacetonitrile; glycine, α-alanine, β-alanine, and N-methylglycine. , N,N-dimethylglycine, 2-aminobutyric acid, norvaline, valine, leucine, norleucine, isoleucine, phenylalanine, proline, sarcosine, ornithine, lysine, taurine, serine, threonine, homoserine, tyrosine, bicine, tricine, 3,5-diiodo-tyrosine, β-(3,4-dihydroxyphenyl)-alanine, thyroxine, 4-hydroxy-proline, cysteine, methionine, ethionine, lanthionine, cystathionine, cystine, cysteic acid, aspartic acid, glutamic acid, S Amino acids such as -(carboxymethyl)-cysteine, 4-aminobutyric acid, asparagine, glutamine, azaserine, arginine, canavanine, citrulline, δ-hydroxy-lysine, creatine, histidine, 1-methyl-histidine, 3-methyl-histidine and tryptophan; nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, N,N,N-trimethylenephosphonic acid, ethylenediamine-N,N,N',N'-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2- Chelating agents such as diaminopropane tetraacetic acid, glycol ether diamine tetraacetic acid, ethylenediamine orthohydroxyphenylacetic acid, ethylenediamine disuccinic acid (SS form), N-(2-carboxylate ethyl)-L-aspartic acid, β-alanine diacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, and 1,2-dihydroxybenzene-4,6-disulfonic acid; and the like.

[0063] However, if a large amount of complexing agent is present in the system, etching of the surface of the object to be polished may proceed excessively, resulting in a decrease in the flatness of the surface of the object to be polished. Therefore, it is preferable that the polishing composition of the present invention is substantially free of complexing agent. Here, "substantially free of complexing agent" not only means that the polishing composition does not contain any complexing agent at all, but also includes the case where the polishing composition contains 0.2% by mass or less of the complexing agent. The content of the complexing agent is more preferably 0.15% by mass or less, even more preferably 0.1% by mass or less, particularly preferably 0.01% by mass or less, based on the total mass of the polishing composition, and most preferably 0% by mass, i.e., no complexing agent is contained at all.

[0064] <Corrosion inhibitor> The corrosion inhibitor has the role of preventing excessive dissolution of metal. Examples of the corrosion inhibitor include heterocyclic compounds. The number of members of the heterocycle in the heterocyclic compound is not particularly limited. The heterocyclic compound may be a monocyclic compound or a polycyclic compound having condensed rings. The corrosion inhibitor may be used alone or in combination of two or more types. The corrosion inhibitor may be a commercially available product or a synthetic product.

[0065] Specific examples of heterocyclic compounds that can be used as anticorrosive agents include nitrogen-containing heterocyclic compounds such as pyrrole compounds, pyrazole compounds, imidazole compounds, triazole compounds, tetrazole compounds, pyridine compounds, pyrazine compounds, pyridazine compounds, pyrindine compounds, indolizine compounds, indole compounds, isoindole compounds, indazole compounds, purine compounds, quinolizine compounds, quinoline compounds, isoquinoline compounds, naphthyridine compounds, phthalazine compounds, quinoxaline compounds, quinazoline compounds, cinnoline compounds, buteridine compounds, thiazole compounds, isothiazole compounds, oxazole compounds, isoxazole compounds, and furazan compounds.

[0066] Further specific examples of the corrosion inhibitor include 1H-benzotriazole, 5-methyl-1H-benzotriazole, 5,6-dimethyl-1H-benzotriazole, 1-[N,N-bis(hydroxyethyl)aminomethyl]-5-methylbenzotriazole, 1-[N,N-bis(hydroxyethyl)aminomethyl]-4-methylbenzotriazole, 1,2,3-triazole, and 1,2,4-triazole.

[0067] However, if a large amount of anticorrosive agent is present in the system, the surface of the object to be polished is overly protected, the activity of hydrogen peroxide to oxidize the surface of the object to be polished is suppressed, and the flatness of the surface of the object to be polished may be reduced. Therefore, it is preferable that the polishing composition of the present invention is substantially free of anticorrosive agent. Here, "substantially free of anticorrosive agent" includes not only the concept that the anticorrosive agent is not contained in the polishing composition at all, but also the case where the anticorrosive agent is contained in the polishing composition at 0.05% by mass or less. The content of the anticorrosive agent is more preferably 0.1% by mass or less, even more preferably 0.05% by mass or less, particularly preferably 0.02% by mass or less, based on the total mass of the polishing composition, and most preferably 0% by mass, i.e., no complexing agent is contained at all.

[0068] <Preservatives> Examples of preservatives include benzalkonium chloride, benzethonium chloride, 1,2-benzisothiazolin-3-one, (5-chloro-)2-methyl-4-isothiazolin-3-one, hydrogen peroxide, or hypochlorite.

[0069] [Electrical conductivity] The electrical conductivity of the polishing composition of the present invention is preferably 4.0 mS / cm or less, more preferably 2.0 mS / cm or less, even more preferably 1.0 mS / cm or less, and particularly preferably 0.5 mS / cm or less. The lower limit of the electrical conductivity is usually 0.05 mS / cm or more.

[0070] If the electrical conductivity is in this range, the flatness of the surface of the object to be polished after polishing can be further improved. The electrical conductivity can be measured by the method described in the Examples.

[0071] In the present invention, the method for controlling the electrical conductivity of the polishing composition to a desired value is not particularly limited, and examples thereof include a method of adding an electrical conductivity adjuster to the polishing composition. The electrical conductivity adjuster is not particularly limited as long as it can control the electrical conductivity to a desired value, and salt compounds such as acid salts and base salts are suitable. The content of the electrical conductivity adjuster in the polishing composition is not particularly limited as long as it is a content that can adjust the electrical conductivity to a desired value. However, like the above-mentioned pH adjusters, the electrical conductivity adjuster according to the present invention preferably does not contain halogen-containing ions. Furthermore, since it is preferable that the electrical conductivity be as low as possible, it is preferable that the polishing composition according to the present invention does not contain an electrical conductivity adjuster.

[0072] <Halogen atom content> From the viewpoint of further improving the flatness of the polished surface of the object to be polished after polishing, the content of halogen atoms in the polishing composition of the present invention is preferably 100 ppm or less, more preferably 50 ppm or less, and even more preferably 30 ppm or less, based on the total mass of the polishing composition. The content of halogen atoms can be measured by ion chromatography.

[0073] <Colloidal silica particle size and electrical conductivity> In the present invention, the smaller the product of the average secondary particle size of the colloidal silica contained in the polishing composition and the electrical conductivity of the polishing composition, the more preferable. The average secondary particle size represents the distance between the polishing pad used in polishing and the surface of the object to be polished, and the product of this average secondary particle size and the electrical conductivity of the polishing composition is thought to be an index of the likelihood of electrical interaction with the surface of the object to be polished. The smaller this product, the less likely electrical interaction will occur with the surface of the object to be polished, and the more improved the flatness of the surface of the object to be polished. On the other hand, the larger this product, the more likely electrical interaction will occur with the surface of the object to be polished, and the more likely the flatness of the surface of the object to be polished will be.

[0074] For these reasons, the product of the average secondary particle size of the colloidal silica contained in the polishing composition and the electrical conductivity of the polishing composition is preferably 200 or less, more preferably 180 or less, more preferably 150 or less, even more preferably 140 or less, particularly preferably 100 or less, and most preferably 80 or less. Furthermore, the product of the average secondary particle size of the colloidal silica contained in the polishing composition and the electrical conductivity of the polishing composition is preferably 0.1 or more, more preferably 1 or more, even more preferably 2.5 or more, and may be 4 or more.

[0075] [Method for producing polishing composition] The method for producing the polishing composition of the present invention is not particularly limited, and the polishing composition can be obtained, for example, by stirring and mixing colloidal silica, hydrogen peroxide, and, if necessary, other additives in water. The details of each component are as described above.

[0076] The temperature at which the components are mixed is not particularly limited, but is preferably 10° C. to 40° C. Heating may be used to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is achieved.

[0077] [Polishing method] As described above, the polishing composition of the present invention is suitable for use in polishing a metal-containing object. Therefore, the present invention provides a polishing method for polishing a metal-containing object with the polishing composition of the present invention. As described above, from the viewpoint of more easily achieving the effects of the present invention, the polishing method is preferably a method for polishing a metal-containing object containing copper or a copper alloy. Furthermore, since the surface of the object to be polished after polishing with the polishing composition of the present invention has very high flatness, the object to be polished is preferably a joining member.

[0078] Here, the surface of a metal material included in a preferred object to be polished is usually polished by multiple polishing steps, including a preliminary polishing step (a polishing step prior to the final polishing step, also called a rough polishing step) and a final polishing step. For example, a polishing composition with high processing power (abrasive power) tends to be used in the step of roughly polishing a metal material (e.g., the preliminary polishing step), while a polishing composition with low abrasive power tends to be used in the step of more delicate polishing (e.g., the final polishing step). In one embodiment, the polishing composition of the present invention is preferably used in the final polishing step of the surface of an object to be polished, including a metal material.

[0079] As the polishing device, a general polishing device can be used, which is equipped with a holder for holding a substrate or the like having an object to be polished, a motor whose rotation speed can be changed, and a polishing platen onto which a polishing pad (polishing cloth) can be attached.

[0080] The polishing pad may be made of any material, including ordinary nonwoven fabric, polyurethane, porous fluororesin, etc. The polishing pad is preferably provided with grooves to allow the polishing liquid to accumulate.

[0081] Regarding the polishing conditions, for example, the rotation speed of the polishing platen is 10 rpm (0.17 s -1 ) or more 500rpm (8.33s -1 The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 30 g / cm or less. 2(2.94kPa) or more 700g / cm 2 (68.6kPa) or less is preferred.

[0082] The method for supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying the polishing composition using a pump, etc. There is no limit to the amount of the polishing composition supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

[0083] After polishing, the substrate is washed with running water, and water droplets adhering to the substrate are removed by a spin dryer or the like, followed by drying, to obtain a substrate having a metal-containing layer.

[0084] The polishing composition of the present invention may be a one-component type or a multi-component type such as a two-component type. The polishing composition of the present invention may also be prepared by diluting the stock solution of the polishing composition, for example, 10 times or more, with a diluent such as water.

[0085] [Arithmetic mean roughness Sa] The surface of the object to be polished after polishing obtained by the polishing composition and polishing method according to the present invention has very high flatness. Specifically, the arithmetic mean roughness Sa of the surface of the object to be polished after polishing is preferably 1.70 nm or less, more preferably 1.30 nm or less, even more preferably 1.20 nm or less, particularly preferably 1.00 nm or less, and most preferably 0.80 nm or less.

[0086] The arithmetic mean roughness Sa can be measured according to the method described in JIS B0601 (2013), and more specifically, can be measured according to the method described in the examples. [Example]

[0087] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0088] [Measurement Methods of Various Physical Properties] In this embodiment, various physical properties were measured by the following methods.

[0089] [Measurement of Particle Size and Average Degree of Aggregation of Colloidal Silica] The value of the average secondary particle size of colloidal silica was adopted as the volume average particle size measured by the dynamic light scattering method using a particle size distribution measuring apparatus (UPA-UT151, manufactured by Nikkiso Co., Ltd.). Also, the value of the average primary particle size of colloidal silica was calculated based on the specific surface area (SA) of colloidal silica calculated from the BET method, assuming that the shape of colloidal silica is a true sphere, using the formula SA = 4πR 2 and calculated using the formula.

[0090] The average degree of aggregation of colloidal silica was calculated by the formula (average secondary particle size / average primary particle size) from the values of the average secondary particle size and average primary particle size measured above.

[0091] [Measurement of Zeta Potential of Colloidal Silica] The zeta potential of colloidal silica in the polishing composition was obtained by subjecting the polishing composition to ELS-Z2 manufactured by Otsuka Electronics Co., Ltd., and analyzing the data obtained by measuring by the laser Doppler method (electrophoretic light scattering measurement method) using a flow cell at a measurement temperature of 25°C with the Smoluchowski formula.

[0092] [Measurement of pH] The pH of the polishing composition was measured using a pH meter (manufactured by Horiba, Ltd., model number: F-71).

[0093] [Measurement of Electrical Conductivity] The electrical conductivity of the polishing composition was measured using a desktop electrical conductivity meter (manufactured by Horiba, Ltd., model number: DS-71).

[0094] [Preparation of Polishing Composition] (Example 1) Unmodified colloidal silica (average primary particle size: 18.5 nm, average secondary particle size: 40 nm, average degree of association: 2.16) was added to pure water as a dispersion medium so that the final concentration was 19 mass % and hydrogen peroxide was added to a final concentration of 1 mass %. Then, the mixture was stirred and mixed at room temperature (25°C) for 10 minutes to prepare a polishing composition.

[0095] (Examples 2 and 3) Polishing compositions were prepared in the same manner as in Example 1, except that the type of unmodified colloidal silica was changed as shown in Table 1 below.

[0096] (Examples 4 to 5) A polishing composition was prepared in the same manner as in Example 2, except that potassium sulfate, an electrical conductivity adjuster, was further added so as to achieve the electrical conductivity shown in Table 1 below.

[0097] Examples 6 to 8 A polishing composition was prepared in the same manner as in Example 2, except that potassium hydroxide, a pH adjuster, was further added so as to achieve the pH shown in Table 1 below.

[0098] Examples 9 to 10 A polishing composition was prepared in the same manner as in Example 2, except that sulfuric acid, a pH adjuster, was further added so as to achieve the pH shown in Table 1 below.

[0099] Example 11 A polishing composition was prepared in the same manner as in Example 2, except that cation-modified colloidal silica prepared by the method described in JP-A-2005-162533 was used instead of unmodified colloidal silica.

[0100] Example 12 A polishing composition was prepared in the same manner as in Example 2, except that an anion-modified colloidal silica prepared by the method described in "Sulfonic acid-functionalized silica through thiol groups", Chem. Commun. 246-247 (2003) was used instead of unmodified colloidal silica.

[0101] Example 13 A polishing composition was prepared in the same manner as in Example 2, except that glycine, a complexing agent, was further added so that the final concentration was 0.01% by mass.

[0102] Example 14 A polishing composition was prepared in the same manner as in Example 2, except that 1H-benzotriazole (BTA) as an anticorrosion agent was further added so that the final concentration was 0.02 mass %.

[0103] (Comparative Examples 1 and 2) Polishing compositions were prepared in the same manner as in Example 1, except that the type of unmodified colloidal silica was changed as shown in Table 1 below.

[0104] (Comparative Example 3) A polishing composition was prepared in the same manner as in Example 1, except that colloidal silica having an average secondary particle diameter of 53 nm and an average degree of association of 1.31 was used.

[0105] Comparative Example 4 A polishing composition was prepared in the same manner as in Example 2, except that hydrogen peroxide was not added.

[0106] (Comparative Example 5) A polishing composition was prepared in the same manner as in Example 2, except that sulfuric acid as a pH adjuster was further added so that the pH was 3.0.

[0107] (Comparative Example 6) A polishing composition was prepared in the same manner as in Example 2, except that orthoperiodic acid was added in place of hydrogen peroxide so that the final concentration would be 1.0 mass %.

[0108] (Comparative Example 7) A polishing composition was prepared in the same manner as in Example 2, except that potassium permanganate was added in place of hydrogen peroxide so that the final concentration would be 1.0 mass %.

[0109] [evaluation] A copper substrate (CU-113551, manufactured by Nilaco Corporation) measuring 100 mm x 100 mm and having a thickness of 2.0 mm was prepared. The copper substrate was roughly polished using the rough polishing composition prepared below under the polishing conditions below. Thereafter, the polishing compositions of the respective Examples and Comparative Examples obtained above were used to perform finish polishing under the polishing conditions below: (polishing conditions) Polishing machine: EJW-400IN (Engis Japan Co., Ltd.) Polishing pad: Suede pad (Fujibo Ehime Co., Ltd., K-1W-202U) Polishing pressure: 210g / cm for rough polishing 2 (20.6kPa), final polishing process 518g / cm 2 (50.8kPa) Platen rotation speed: 90 rpm Head (carrier) rotation speed: 50 rpm Polishing composition flow rate: 17 ml / min Polishing time: 10 minutes for rough polishing, 10 minutes for finish polishing.

[0110] (Rough polishing composition) A rough polishing composition was prepared in the same manner as in Example 2, except that glycine, a complexing agent, was added so that the final concentration was 2 mass %.

[0111] (polishing speed) The polishing rate in the final polishing step was calculated using the following formula.

[0112]

number

[0113] The film thickness was measured using an XS205 manufactured by METTLER TOLEDO, and the polishing rate was calculated by dividing the difference in weight before and after polishing by the substrate density, polishing area, and polishing time.

[0114] (arithmetic mean roughness Sa) The arithmetic mean roughness Sa of the copper substrate surface after the finish polishing process was measured using a non-contact surface profiler (Zygo NewView9000) using white light interferometry with a viewing angle of 172 μm square and a resolution of 1024 × 1024.

[0115] The composition of the polishing composition of each Example and Comparative Example and the evaluation results are shown in Table 1 below.

[0116] [Table 1]

[0117] As is clear from Table 1 above, when the polishing compositions of Examples were used, the surface of the object to be polished after polishing had very high flatness. On the other hand, when the polishing compositions of Comparative Examples were used, the flatness of the surface of the object to be polished after polishing was found to be reduced.

Claims

1. A polishing composition comprising colloidal silica and hydrogen peroxide, The colloidal silica has an average secondary particle diameter of less than 80 nm and an average degree of association of 1.5 or more, The polishing composition has a pH of 5 or more, the zeta potential of the colloidal silica in the polishing composition is negative; the product of the average secondary particle diameter of the colloidal silica and the electrical conductivity of the polishing composition is 200 nm mS / cm or less; A polishing composition used for polishing an object to be polished, including a metal material.

2. 2. The polishing composition according to claim 1, having a pH of 6.5 or more and 9.5 or less.

3. 3. The polishing composition according to claim 1, wherein the degree of association of the colloidal silica is 1.6 or more and 3.0 or less.

4. 4. The polishing composition according to claim 1, which is substantially free of a complexing agent.

5. 5. The polishing composition according to claim 1, which is substantially free of an anticorrosive agent.

6. 6. The polishing composition according to claim 1, which is substantially free of an oxidizing agent containing a halogen-containing ion.

7. 7. The polishing composition according to claim 1, wherein the colloidal silica is unmodified colloidal silica or anion-modified colloidal silica.

8. 8. The polishing composition according to claim 1, wherein the metal material is copper or a copper alloy.

9. 9. The polishing composition according to claim 1, wherein the object to be polished is a joining member.

10. A polishing method comprising polishing an object to be polished, which includes polishing the object to be polished, the object comprising a metal material, with the polishing composition according to any one of claims 1 to 9.

11. The polishing method according to claim 10, wherein the metal material is copper or a copper alloy.

12. The polishing method according to claim 10 or 11, wherein the object to be polished is a joined member.

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