Composition for polishing

Abstract

To provide a novel polishing composition capable of improving the polishing speed of metals (particularly, tungsten) and maintaining stability as a composition.SOLUTION: A polishing composition contains: abrasive grains; a quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof; and a liquid carrier, where a pH of the polishing composition is from 2 to 5, and a zeta potential of the abrasive grains in the polishing composition is adjusted to 15 mV or more and less than 40 mV over the entire pH range of 2 to 4.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] The high integration brought about by the miniaturization of LSI manufacturing processes has led to the achievement of high performance in electronic devices such as computers, including miniaturization, multi-functioning, and high speed. Chemical mechanical polishing (CMP) is used as a new microfabrication technology in line with this high integration of LSIs. CMP is a technology that is frequently used in the LSI manufacturing process, particularly in the planarization of interlayer insulating films in the multilayer wiring formation process, metal plug formation, and embedded wiring (damascene wiring) formation.

[0003] In this process, metals with excellent embedding properties (especially tungsten) are used as materials for plugs that electrically connect wirings in the vertical and vertical directions. In the chemical mechanical polishing to form a tungsten plug, a first polishing process step is performed in which the tungsten layer provided on the insulating film is polished, and a second polishing process step is performed in which the tungsten plug, a barrier metal film such as titanium, and the insulating film are polished in that order.

[0004] Regarding the chemical mechanical polishing of such tungsten layers and tungsten plugs (hereinafter also referred to as "tungsten films"), a chemical mechanical polishing composition is known that contains a specific amine compound, a dispersion medium containing water, abrasive grains such as colloidal silica, and an oxidizing agent (Patent Document 1). Patent Document 1 discloses that it is preferable to use cationic modified colloidal silica in which a cationic group is introduced to the surface of colloidal silica by using a silane coupling agent such as aminopropyltrimethoxysilane on the surface of colloidal silica in order to impart stability to the abrasive grains under acidic conditions (Patent Document 1 "0031"). The cationic modification of colloidal silica can be carried out by adding a silane coupling agent such as aminopropyltrimethoxysilane to a dispersion liquid in which colloidal silica is dispersed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-61612 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, even if the chemical mechanical polishing composition disclosed in Patent Document 1 is used, the polishing rate of the tungsten film cannot be sufficiently improved, which causes a problem that productivity is not improved.

[0007] On the other hand, one of the basic physical properties required for a polishing composition is that it is essential that the composition maintain its stability.

[0008] Therefore, an object of the present invention is to provide a novel polishing composition that can improve the removal rate of metals (particularly tungsten) while maintaining the stability as a composition. [Means for solving the problem]

[0009] In order to solve the above problems, the present inventors have conducted extensive research and found that the above problems can be solved by providing a polishing composition that includes an abrasive grain, a quaternary amine having at least one alkyl group having two or more carbon atoms or a salt thereof, and a liquid carrier, the pH of the polishing composition being 2 to 5, and the zeta potential of the abrasive grains in the polishing composition being adjusted to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4. Effect of the Invention

[0010] The present invention can provide a novel polishing composition that can improve the removal rate of metals (particularly tungsten) and maintain the stability as a composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described below. The present invention is not limited to the following embodiments. Unless otherwise specified, the operation and measurement of physical properties are performed under the conditions of room temperature (20 to 25°C) / relative humidity 40 to 50% RH. It should be understood that all combinations of lower and upper limits disclosed in this specification are disclosed. In other words, it should be understood that they can be the basis for correction. It should be understood that all combinations of embodiments are disclosed in this application. In other words, it should be understood that they can be the basis for correction.

[0012] <Polishing composition> In one embodiment of the present invention, there is provided a polishing composition comprising an abrasive, a quaternary amine having at least one alkyl group having two or more carbon atoms or a salt thereof, and a liquid carrier, the pH of the polishing composition being 2 to 5, and the zeta potential of the abrasive in the polishing composition being adjusted to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4. According to this embodiment, there is provided a novel polishing composition that can improve the removal rate of metals (particularly tungsten) and maintains stability as a composition.

[0013] Each component constituting the polishing composition will be described below.

[0014] [Abrasive grain] In one embodiment of the present invention, the polishing composition contains abrasive grains. The abrasive grains have the function of mechanically polishing an object to be polished, and increase the polishing rate of the object to be polished.

[0015] In one embodiment of the present invention, the abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles.Specific examples of inorganic particles include metal oxide particles such as silica, alumina, ceria, and titania, silicon nitride particles, silicon carbide particles, and boron nitride particles.Specific examples of organic particles include polymethylmethacrylate (PMMA) particles.Among these abrasive grains, silica (particularly colloidal silica) is preferred.

[0016] In one embodiment of the present invention, the average primary particle size of the abrasive grains is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, and even more preferably 25 nm or more. By having such a lower limit, the polishing speed of the object to be polished can be improved. In one embodiment of the present invention, the average primary particle size of the abrasive grains is preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less. By having such an upper limit, the polishing quality of the object to be polished can be improved. In addition, in one embodiment of the present invention, the average primary particle size of the abrasive grains may be a value measured by the method described in the Examples.

[0017] In one embodiment of the present invention, the average secondary particle diameter of the abrasive grains is preferably 30 nm or more, more preferably 35 nm or more, even more preferably 40 nm or more, even more preferably 45 nm or more, and even more preferably 50 nm or more. By having such a lower limit, the polishing speed of the object to be polished can be improved. In one embodiment of the present invention, the average secondary particle diameter of the abrasive grains is preferably 100 nm or less, more preferably 90 nm or less, and even more preferably 80 nm or less. By having such an upper limit, the polishing quality of the object to be polished can be improved. In one embodiment of the present invention, the average secondary particle diameter of the abrasive grains may be a value measured by the method described in the Examples.

[0018] In one embodiment of the present invention, the lower limit of the average degree of association of the abrasive grains (average secondary particle size / average primary particle size) is preferably 1.3 or more, more preferably 1.4 or more, and even more preferably 1.5 or more. By having such a lower limit, it is possible to obtain a certain mechanical polishing action, and there is a technical effect of improving the polishing rate. In one embodiment of the present invention, the average degree of association of the abrasive grains (average secondary particle size / average primary particle size) Upper limit is preferably 4.0 or less, more preferably 3.5 or less, even more preferably 3.0 or less, even more preferably 2.5 or less, and even more preferably 2.4 or less. By having such an upper limit, there is a technical effect of suppressing settling due to particle enlargement and defects in the object to be polished.

[0019] In one embodiment of the present invention, the content (solid content) of the abrasive grains in the polishing composition is preferably 0.1% by mass or more, more preferably 1% by mass or more, more preferably 1.5% by mass or more, even more preferably 2% by mass or more, even more preferably 2.5% by mass or more, even more preferably 3.0% by mass or more, and even more preferably 3.5% by mass or more. By having such a lower limit, the polishing speed of the object to be polished can be improved. In one embodiment of the present invention, the content (solid content) of the abrasive grains in the polishing composition is preferably 10% by mass or less, more preferably 9% by mass or less, even more preferably 8% by mass or less, even more preferably 7% by mass or less, even more preferably 6% by mass or less, and even more preferably 5% by mass or less. By having such an upper limit, the polishing quality of the object to be polished can be improved.

[0020] As mentioned above, Patent Document 1 discloses that, in relation to chemical mechanical polishing of tungsten film, it is preferable to use cationic modified colloidal silica in which cationic groups are introduced to the surface of colloidal silica using a silane coupling agent. Here, as a method for producing colloidal silica having such cationic groups, a method is known in which a silane coupling agent having an amino group such as aminoethyltrimethoxysilane, aminopropyltrimethoxysilane, aminoethyltriethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, aminobutyltriethoxysilane, or a silane coupling agent having a quaternary ammonium group such as N-trimethoxysilylpropyl-N,N,N-trimethylammonium is immobilized on the surface of abrasive grains, as described in JP-A-2005-162533. The abrasive grains in one embodiment of the present invention are different from the abrasive grains in which such a silane coupling agent having an amino group or a silane coupling agent having a quaternary ammonium group is immobilized on the surface of the abrasive grains.

[0021] (The number of silanol groups is 0 / nm 2 More than 2.5 pieces / nm 2 below) In one embodiment of the present invention, the number of silanol groups per unit surface area of ​​the abrasive grain is 0 / nm 2 More than 2.5 pieces / nm 2 According to this embodiment, the polishing speed of the object to be polished (particularly tungsten) can be improved.

[0022] In one embodiment of the present invention, the number of silanol groups is 2.4 / nm 2 Below, 2.3 pieces / nm 2 Below, 2.2 pieces / nm 2 Below, 2.1 pieces / nm 2 Below, 2.0 pieces / nm 2 Below, 1.9 pieces / nm 2 or less than 1.8 particles / nm 2By having such an upper limit, the polishing rate of the object to be polished (particularly tungsten) can be improved. In one embodiment of the present invention, the number of silanol groups is 0.2 / nm 2 More than 0.4 pieces / nm 2 More than 0.6 pieces / nm 2 More than 0.8 pieces / nm 2 More than 1.0 pieces / nm 2 More than 1.2 pieces / nm 2 More than 1.4 pieces / nm 2 That is all. By having such a lower limit, there is a technical effect of suppressing defects.

[0023] Here, the number of silanol groups per unit surface area of ​​the abrasive grain is set to 2.5 / nm 2 In order to achieve the above, the number of silanol groups on the abrasive grain surface can be controlled by selecting a manufacturing method for the abrasive grains, and it is preferable to carry out a heat treatment such as calcination. In one embodiment of the present invention, the calcination treatment is, for example, holding the abrasive grains (e.g., silica) in an environment of 120 to 200°C for 30 minutes or more. By carrying out such a heat treatment, the number of silanol groups on the abrasive grain surface can be reduced to 2.5 / nm. 2 Unless such special treatment is performed, the number of silanol groups on the abrasive grain surface is 2.5 / nm2 or less. 2 It will not be below.

[0024] In one embodiment of the present invention, the silanol group density can be calculated by the following method after measuring or calculating each parameter by the following measurement method or calculation method.

[0025] In the formula below, C is the total mass of the abrasive grains, and S is the BET specific surface area of ​​the abrasive grains. First, 1.50 g of abrasive grains as solid content is collected in a 200 ml beaker, 100 ml of pure water is added to make a slurry, and then 30 g of sodium chloride is added and dissolved. Next, 1 N hydrochloric acid is added to adjust the pH of the slurry to about 3.0 to 3.5, and pure water is added until the slurry becomes 150 ml. This slurry is adjusted to pH 4.0 with 0.1 N sodium hydroxide at 25 ° C. using an automatic titration device (manufactured by Hiranuma Sangyo Co., Ltd., COM-1700), and the volume V [L] of the 0.1 N sodium hydroxide solution required to increase the pH from 4.0 to 9.0 by pH titration is measured. The silanol group density can be calculated by the formula below.

[0026]

number

[0027] In the above formula, ρ is the silanol group density (pcs / nm 2 ) ; c represents the concentration (mol / L) of the sodium hydroxide solution used in the titration; V is the volume (L) of sodium hydroxide solution required to raise the pH from 4.0 to 9.0 Represents; N A represents the Avogadro constant (units / mol); C represents the total mass (solids) of the abrasive grains (g); S is the weighted average value of the BET specific surface area of ​​the abrasive grains (nm 2 / g).

[0028] (The number of silanol groups is 2.5 / nm 2 super) In one embodiment of the present invention, the number of silanol groups per unit surface area of ​​the abrasive grain is 2.5 / nm 2 In one embodiment of the present invention, the number of silanol groups is greater than 3.0 / nm 2 More than 4.0 pieces / nm 2or more than 5.0 pieces / nm 2 The lower limit of the silanol group number is 8.0 / nm2. 2 Below, 7.0 pieces / nm 2 Less than or equal to 6.0 pieces / nm 2 By having such an upper limit, there is a technical effect of improving the removal rate.

[0029] [Quaternary amine having at least one alkyl group having two or more carbon atoms or a salt thereof] In one embodiment of the present invention, the polishing composition contains a quaternary amine or a salt thereof having at least one alkyl group having 2 or more carbon atoms. The quaternary amine or a salt thereof having at least one alkyl group having 2 or more carbon atoms can modify the surface of the abrasive grains and adjust the zeta potential of the surface of the abrasive grains. More specifically, the quaternary amine or a salt thereof can adjust the zeta potential of the abrasive grains in the polishing composition to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4. However, the inclusion of the quaternary amine or a salt thereof in the polishing composition does not necessarily mean that the zeta potential can be adjusted to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4.

[0030] In addition, although it is essential that the quaternary amine salt "has at least one alkyl group having two or more carbon atoms," the intended effect of the present invention cannot be achieved even if tetramethylammonium hydroxide is used as the quaternary amine salt. A person skilled in the art can adjust the zeta potential to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4 by adjusting the amount of such a quaternary amine or its salt and selecting the addition of other components.

[0031] In one embodiment of the present invention, the polishing composition contains a quaternary amine or a salt thereof having one, two, three, or four alkyl groups having two or more carbon atoms. In this case, the quaternary amine or a salt thereof has three, two, one, or zero methyl groups. In one embodiment of the present invention, it is preferable to use a quaternary amine or a salt thereof having three or more alkyl groups having two or more carbon atoms.

[0032] In one embodiment of the present invention, the quaternary amine or its salt has an alkyl group having 2 or more carbon atoms, an alkyl group having 3 or more carbon atoms, or an alkyl group having 4 or more carbon atoms. In one embodiment of the present invention, the quaternary amine or its salt has an alkyl group having 18 or less carbon atoms, an alkyl group having 16 or less carbon atoms, an alkyl group having 14 or less carbon atoms, an alkyl group having 12 or less carbon atoms, an alkyl group having 10 or less carbon atoms, an alkyl group having 8 or less carbon atoms, an alkyl group having 6 or less carbon atoms, an alkyl group having 4 or less carbon atoms, or an alkyl group having 3 or less carbon atoms. This embodiment improves the solubility in the liquid carrier. Among them, in order to efficiently achieve the intended effect of the present invention, it is preferable that the quaternary amine or its salt has an alkyl group having 3 or less carbon atoms.

[0033] In one embodiment of the present invention, the alkyl group having 2 to 18 carbon atoms may be linear or branched, and examples thereof include an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a hexyl group, an octyl group, a dodecyl group, etc. However, from the viewpoint of efficiently achieving the intended effects of the present invention, a linear group is preferable.

[0034] In one embodiment of the present invention, the salt may be a hydroxide ion or a halide ion. Preferred examples of the halide ion include a chloride ion and a bromide ion.

[0035] In one embodiment of the present invention, the quaternary amine having at least one alkyl group having two or more carbon atoms or a salt thereof is represented by the following formula:

[0036] [ka]

[0037] In this case, R 1 ~R 4 are each independently an alkyl group having 2 to 18 carbon atoms; Y - is a counter anion. According to such an embodiment, the intended effects of the present invention can be efficiently achieved.

[0038] In such embodiments, R 1 ~R 4 are each independently an alkyl group having 2 or more carbon atoms, an alkyl group having 3 or more carbon atoms, or an alkyl group having 4 or more carbon atoms. 1 ~R 4 are each independently an alkyl group having 18 or less carbon atoms, an alkyl group having 16 or less carbon atoms, an alkyl group having 14 or less carbon atoms, an alkyl group having 12 or less carbon atoms, an alkyl group having 10 or less carbon atoms, an alkyl group having 8 or less carbon atoms, an alkyl group having 6 or less carbon atoms, an alkyl group having 4 or less carbon atoms, or an alkyl group having 3 or less carbon atoms. Such an embodiment improves the solubility in the liquid carrier. In one embodiment of the present invention, the alkyl group has 2 to 4 carbon atoms. Preferably, the alkyl group has 2 or 3 carbon atoms. According to such an embodiment, the intended effect of the present invention can be more efficiently achieved.

[0039] In the above embodiment, Y - can be a hydroxide ion or a halide ion.

[0040] In one embodiment of the present invention, the content (active ingredient concentration) of the quaternary amine or its salt having at least one alkyl group having 2 or more carbon atoms in the polishing composition is 0.001% by mass or more, 0.01% by mass or more, 0.03% by mass or more, 0.06% by mass or more, 0.08% by mass or more, 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more. According to such an embodiment, there are technical effects of improving the polishing rate and good dispersion stability. In one embodiment of the present invention, the content (active ingredient concentration) of the quaternary amine or its salt having at least one alkyl group having 2 or more carbon atoms in the polishing composition is 5% by mass or less, 3% by mass or less, 1% by mass or less, 0.8% by mass or less, 0.6% by mass or less, 0.4% by mass or less, 0.3% by mass or less, 0.2% by mass or less, 0.15% by mass or less, 0.12% by mass or less, or less than 0.12% by mass. According to this embodiment, there are technical effects of improving the polishing rate and providing good dispersion stability.

[0041] [pH of polishing composition] In one embodiment of the present invention, the pH of the polishing composition is 2 to 5. If the pH of the polishing composition is less than 2, the desired effect of the present invention cannot be achieved. If the pH of the polishing composition is more than 5, the dispersion stability of silica may be impaired. In one embodiment of the present invention, the pH of the polishing composition may be 2.2 or more, 2.4 or more, 2.6 or more, 2.8 or more, 3.0 or more, 3.2 or more, 3.4 or more, 3.6 or more, or 3.8 or more. In one embodiment of the present invention, the pH of the polishing composition may be 4.8 or less, 4.6 or less, 4.4 or less, 4.2 or less, 4.0 or less, 3.8 or less, 3.4 or less, 3.2 or less, 3.0 or less, less than 2.9, 2.8 or less, 2.7 or less, or 2.6 or less. By having such a lower limit, the desired effect of the present invention can be efficiently achieved. In this specification, the pH of the polishing composition can be measured according to the method described in the examples.

[0042] In one embodiment of the present invention, the polishing composition contains a pH adjuster. As the pH adjuster, an acid, a base, or a salt thereof can be used.

[0043] In one embodiment of the present invention, the base may be a quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof. In one embodiment of the present invention, the base may contain other compounds. Examples of such bases include amines such as aliphatic amines and aromatic amines, ammonium solutions, organic bases such as quaternary ammonium hydroxide, hydroxides of alkali metals such as potassium hydroxide, hydroxides of Group 2 elements, amino acids such as histidine, and ammonia. However, according to one embodiment of the present invention, the base does not contain anything other than the quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof. According to such an embodiment, the polishing rate can be improved and good dispersion stability can be achieved. The term "not containing" used in this specification also includes cases where the corresponding component is not contained at all in the polishing composition, and also includes cases where the component is contained in an amount of 0.5 mass ppm or less.

[0044] In one embodiment of the present invention, the acid may be an inorganic acid such as periodic acid, hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, or phosphoric acid; or an organic acid such as formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, 2-methylbutyric acid, hexanoic acid, 3,3-dimethyl-butyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, heptanoic acid, 2-methylhexanoic acid, octanoic acid, 2-ethylhexanoic acid, benzoic acid, hydroxyacetic 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, or phenoxyacetic acid.

[0045] In one embodiment of the present invention, the acid has a function of oxidizing a metal. Examples of acids having a function of oxidizing a metal include periodic acid, hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, perchloric acid, sodium persulfate, potassium persulfate, and ammonium persulfate. According to this embodiment, the intended effect of the present invention can be efficiently achieved. In one embodiment of the present invention, the polishing composition does not contain any acid other than the acid having a function of oxidizing a metal. According to this embodiment, there is a technical effect that the polishing rate can be improved.

[0046] In one embodiment of the present invention, the polishing composition contains one acid and one base.

[0047] In one embodiment of the present invention, the content (active ingredient concentration) of the acid in the polishing composition (total of two or more) is 0.001 mass% or more, 0.01 mass% or more, 0.03 mass% or more, 0.06 mass% or more, 0.08 mass% or more, 0.1 mass% or more, 0.2 mass% or more, or 0.3 mass% or more. In one embodiment of the present invention, the content (active ingredient concentration) of the acid in the polishing composition (total of two or more) is 5 mass% or less, 3 mass% or less, 1 mass% or less, 0.8 mass% or less, 0.6 mass% or less, 0.4 mass% or less, 0.3 mass% or less, 0.25 mass% or less, 0.2 mass% or less, or 0.15 mass% or less.

[0048] In one embodiment of the present invention, the content (active ingredient concentration) of the base in the polishing composition (total of two or more) is 0.001 mass% or more, 0.01 mass% or more, 0.03 mass% or more, 0.06 mass% or more, 0.08 mass% or more, 0.1 mass% or more, 0.15 mass% or more, 0.2 mass% or more, 0.3 mass% or more, 0.4 mass% or more, 0.5 mass% or more, or 0.6 mass% or more. In one embodiment of the present invention, the content (active ingredient concentration) of the base in the polishing composition (total of two or more) is 5 mass% or less, 3 mass% or less, 1 mass% or less, 0.8 mass% or less, 0.6 mass% or less, 0.4 mass% or less, 0.3 mass% or less, 0.25 mass% or less, 0.2 mass% or less, or 0.15 mass% or less, 0.12 mass% or less, or less than 0.12 mass%.

[0049] Although the content (active ingredient concentration) of the pH adjuster (acid, base) has been explained, the above content (active ingredient concentration) is not particularly limited, and may be appropriately adjusted so that the polishing composition has a desired pH within the range of pH 2 to 5.

[0050] In one embodiment of the present invention, the polishing composition contains an acid and a base, and the base is only a quaternary amine having at least one alkyl group having two or more carbon atoms or a salt thereof, or a combination of the quaternary amine or a salt thereof and at least one of the above-mentioned bases, and the pH of the polishing composition is adjusted to 2 to 5, 2 to 4.4, 2 to 4, 2 to 3, or 2 or more and less than 2.9. By adopting such an embodiment, the intended effect of the present invention can be efficiently achieved.

[0051] [Zeta potential] In one embodiment of the present invention, the zeta potential of the abrasive grains in the polishing composition is adjusted to 15 mV or more and less than 40 mV over the entire pH range of 2 to 4. If the zeta potential of the abrasive grains in the polishing composition is not maintained at 15 mV or more over the entire pH range of 2 to 4, the desired effect cannot be achieved. Similarly, if the zeta potential of the abrasive grains in the polishing composition is not maintained at less than 40 mV over the entire pH range of 2 to 4, the desired effect cannot be achieved.

[0052] In one embodiment of the present invention, the zeta potential of the abrasive grains is adjusted to be 15 mV or more and less than 40 mV over the entire range of pH from 2 to 5. This embodiment makes it possible to achieve the desired effect over a wider pH range.

[0053] In one embodiment of the present invention, the zeta potential of the abrasive grains is 38 mV or less, 36 mV or less, 34 mV or less, 32 mV or less, 30 mV or less, 28 mV or less, 26 mV or less, 25 mV or less, 24 mV or less, 22 mV or less, less than 22 mV, 21 mV or less, less than 20.7 mV, or 20.5 mV or less. By having such an upper limit, the desired effect of the present invention can be efficiently achieved.

[0054] In one embodiment of the present invention, the zeta potential of the abrasive grains is 16 mV or more, 17 mV or more, 18 mV or more, 19 mV or more, or 20 mV or more. By adopting such an embodiment, the intended effect of the present invention can be more efficiently achieved.

[0055] [Oxidizing agent] In one embodiment of the present invention, the polishing composition may contain an oxidizing agent. In one embodiment of the present invention, when the polishing composition does not contain an acid having a function of oxidizing a metal, it may contain an oxidizing agent.

[0056] In one embodiment of the present invention, the oxidizing agent is preferably a peroxide. Specific examples of such peroxides include, but are not limited to, hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, potassium monopersulfate, and oxone. The above oxidizing agents may be used alone or in combination of two or more.

[0057] In one embodiment of the present invention, the lower limit of the content (active ingredient concentration) of the oxidizing agent in the polishing composition (the total when two or more types are used) is 0.001 mass% or more, 0.005 mass% or more, 0.01 mass% or more, 0.1 mass% or more, 0.2 mass% or more, or 0.3 mass% or more. In one embodiment of the present invention, the upper limit of the content (active ingredient concentration) of the oxidizing agent in the polishing composition (the total when two or more types are used) is 10 mass% or less, 5 mass% or less, 3 mass% or less, 1 mass% or less, or 0.5 mass% or less.

[0058] [Liquid carrier] In one embodiment of the present invention, the polishing composition includes a liquid carrier. The liquid carrier has the function of dispersing or dissolving each component. The liquid carrier is more preferably only water. In addition, the liquid carrier may be a mixed solvent of water and an organic solvent for dispersing or dissolving each component.

[0059] The water is preferably water that contains as few impurities as possible from the viewpoint of preventing contamination of the object to be polished and inhibiting the action of other components. Here, the purity of the water can be increased by, for example, removing impurity ions using an ion exchange resin, removing foreign matter using a filter, distillation, etc. Specifically, it is preferable to use, for example, deionized water (ion-exchanged water), pure water, ultrapure water, distilled water, etc. as the water.

[0060] [Other additives] In one embodiment of the present invention, the polishing composition may or may not contain other additives. When it contains other additives, attention should be paid to adjust the zeta potential of the abrasive grains in the polishing composition to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4. Specific examples of other additives include complexing agents, metal corrosion inhibitors, preservatives, fungicides, reducing agents, water-soluble polymers, and organic solvents for dissolving poorly soluble organic substances.

[0061] Among the other additives, the complexing agent, metal corrosion inhibitor, preservative, and fungicide will be described below.

[0062] (Complexing Agent) The complexing agent has the effect of chemically etching the surface of the object to be polished, and can more effectively increase the polishing rate of the object to be polished with the polishing composition.

[0063] Examples of the complexing agent include inorganic acids or salts thereof, organic acids or salts thereof, nitrile compounds, amino acids, and chelating agents. These complexing agents may be used alone or in combination of two or more. The complexing agent may be a commercially available product or a synthetic product.

[0064] The complexing agent may be a salt of the inorganic acid or the organic acid. In particular, when a salt of a weak acid and a strong base, a salt of a strong acid and a weak base, or a salt of a weak acid and a weak base is used, a pH buffering effect can be expected. Examples of such salts include potassium chloride, sodium sulfate, potassium nitrate, potassium carbonate, potassium tetrafluoroborate, potassium pyrophosphate, potassium oxalate, trisodium citrate, (+)-potassium tartrate, and potassium hexafluorophosphate.

[0065] Specific examples of the nitrile compound include acetonitrile, aminoacetonitrile, propionitrile, butyronitrile, isobutyronitrile, benzonitrile, glutarodinitrile, and methoxyacetonitrile.

[0066] Specific examples of amino acids include glycine, α-alanine, β-alanine, 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, These include 4-hydroxy-proline, cysteine, methionine, ethionine, lanthionine, cystathionine, cystine, cysteic acid, aspartic acid, glutamic acid, S-(carboxymethyl)-cysteine, 4-aminobutyric acid, asparagine, glutamine, azaserine, arginine, canavanine, citrulline, delta-hydroxy-lysine, creatine, histidine, 1-methyl-histidine, 3-methyl-histidine and tryptophan.

[0067] Specific examples of the chelating agent include nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, N,N,N-trimethylenephosphonic acid, ethylenediamine-N,N,N',N'-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-diaminopropanetetraacetic acid, glycol ether diaminetetraacetic 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.

[0068] When the polishing composition contains a complexing agent, the content (active ingredient concentration) of the complexing agent is not particularly limited. For example, the lower limit of the content (active ingredient concentration) of the complexing agent is not particularly limited because it is effective even in a small amount, but is preferably 0.001 g / L or more, more preferably 0.01 g / L or more, and even more preferably 1 g / L or more. In addition, the upper limit of the content (active ingredient concentration) of the complexing agent is preferably 20 g / L or less, more preferably 15 g / L or less, and even more preferably 10 g / L or less. If it is in such a range, the polishing speed of the object to be polished is improved, and it is advantageous in improving the smoothness of the surface of the object to be polished after polishing with the polishing composition.

[0069] (Metal corrosion inhibitor) Metal corrosion inhibitors act to prevent the dissolution of metals, thereby suppressing deterioration of the surface condition, such as roughening of the polished surface.

[0070] The metal corrosion inhibitor is a heterocyclic compound or a surfactant. The number of members of the heterocyclic ring in the heterocyclic compound is not particularly limited. The heterocyclic compound may be a monocyclic compound or a polycyclic compound having a condensed ring. The metal corrosion inhibitor may be used alone or in combination of two or more kinds. The metal corrosion inhibitor may be a commercially available product or a synthetic product.

[0071] Specific examples of the heterocyclic compound 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.

[0072] More specifically, examples of pyrazole compounds include 1H-pyrazole, 4-nitro-3-pyrazolecarboxylic acid, 3,5-pyrazolecarboxylic acid, 3-amino-5-phenylpyrazole, 5-amino-3-phenylpyrazole, 3,4,5-tribromopyrazole, 3-aminopyrazole, 3,5-dimethylpyrazole, 3,5-dimethyl-1-hydroxymethylpyrazole, 3-methylpyrazole, 1-methylpyrazole, 3-amino-5-methylpyrazole, 4-amino-pyrazolo[3,4-d]pyrimidine, allopurinol, 4-chloro-1H-pyrazolo[3,4-D]pyrimidine, 3,4-dihydroxy-6-methylpyrazolo(3,4-B)-pyridine, and 6-methyl-1H-pyrazolo[3,4-b]pyridin-3-amine.

[0073] Examples of the imidazole compound include imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 1,2-dimethylpyrazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, benzimidazole, 5,6-dimethylbenzimidazole, 2-aminobenzimidazole, 2-chlorobenzimidazole, 2-methylbenzimidazole, 2-(1-hydroxyethyl)benzimidazole, 2-hydroxybenzimidazole, 2-phenylbenzimidazole, 2,5-dimethylbenzimidazole, 5-methylbenzimidazole, and 5-nitrobenzimidazole.

[0074] Examples of triazole compounds include, for example, 1,2,3-triazole (1H-BTA), 1,2,4-triazole, 1-methyl-1,2,4-triazole, methyl-1H-1,2,4-triazole-3-carboxylate, 1,2,4-triazole-3-carboxylic acid, methyl 1,2,4-triazole-3-carboxylate, 1H-1,2,4-triazole-3-thiol, 3,5-diamino-1H-1,2,4-triazole, 3-amino-1,2,4 -triazole-5-thiol, 3-amino-1H-1,2,4-triazole, 3-amino-5-benzyl-4H-1,2,4-triazole, 3-amino-5-methyl-4H-1,2,4-triazole, 3-nitro-1,2,4-triazole, 3-bromo-5-nitro-1,2,4-triazole, 4-(1,2,4-triazol-1-yl)phenol, 4-amino-1,2,4-triazole, 4-amino-3,5-dipropyl-4H-1,2,4 -triazole, 4-amino-3,5-dimethyl-4H-1,2,4-triazole, 4-amino-3,5-dipeptyl-4H-1,2,4-triazole, 5-methyl-1,2,4-triazole-3,4-diamine, 1H-benzotriazole, 1-hydroxybenzotriazole, 1-aminobenzotriazole, 1-carboxybenzotriazole, 5-chloro-1H-benzotriazole, 5-nitro-1H-benzotriazole, 5-carboxy-1H-benzotriazole, 5-methyl-1H-benzotriazole, 5,6-dimethyl-1H-benzotriazole, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-[N,N-bis(hydroxyethyl)aminomethyl]benzotriazole, 1-[N,N-bis(hydroxyethyl)aminomethyl]-5-methylbenzotriazole, 1-[N,N-bis(hydroxyethyl)aminomethyl]-4-methylbenzotriazole, and the like.

[0075] Examples of the tetrazole compound include 1H-tetrazole, 5-methyltetrazole, 5-aminotetrazole, and 5-phenyltetrazole.

[0076] Examples of indazole compounds include 1H-indazole, 5-amino-1H-indazole, 5-nitro-1H-indazole, 5-hydroxy-1H-indazole, 6-amino-1H-indazole, 6-nitro-1H-indazole, 6-hydroxy-1H-indazole, and 3-carboxy-5-methyl-1H-indazole.

[0077] Examples of indole compounds include 1H-indole, 1-methyl-1H-indole, 2-methyl-1H-indole, 3-methyl-1H-indole, 4-methyl-1H-indole, 5-methyl-1H-indole, 6-methyl-1H-indole, 7-methyl-1H-indole, 4-amino-1H-indole, 5-amino-1H-indole, 6-amino-1H-indole, 7-amino-1H-indole, 4-hydro-1H-indole, 5-amino-1H-indole, 6-amino-1H-indole, 7-amino-1H-indole, 4-hydro-1H-indole, 5-amino-1H-indole, 6-hydro ... 1H-indole, 5-hydroxy-1H-indole, 6-hydroxy-1H-indole, 7-hydroxy-1H-indole, 4-methoxy-1H-indole, 5-methoxy-1H-indole, 6-methoxy-1H-indole, 7-methoxy-1H-indole, 4-chloro-1H-indole, 5-chloro-1H-indole, 6-chloro-1H-indole, 7-chloro-1H-indole, 4-carboxy-1H- Indole, 5-carboxy-1H-indole, 6-carboxy-1H-indole, 7-carboxy-1H-indole, 4-nitro-1H-indole, 5-nitro-1H-indole, 6-nitro-1H-indole, 7-nitro-1H-indole, 4-nitrile-1H-indole, 5-nitrile-1H-indole, 6-nitrile-1H-indole, 7-nitrile-1H-indole, 2,5-dimethyl-1H-indole Indole, 1,2-dimethyl-1H-indole, 1,3-dimethyl-1H-indole, 2,3-dimethyl-1H-indole, 5-amino-2,3-dimethyl-1H-indole, 7-ethyl-1H-indole, 5-(aminomethyl)indole, 2-methyl-5-amino-1H-indole, 3-hydroxymethyl-1H-indole, 6-isopropyl-1H-indole, 5-chloro-2-methyl-1H-indole, and the like.

[0078] Moreover, examples of surfactants used as metal corrosion inhibitors include anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0079] Examples of anionic surfactants include polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl sulfates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, alkyl ether sulfates, alkyl benzene sulfonates, alkyl phosphates, polyoxyethylene alkyl phosphates, polyoxyethylene sulfosuccinic acids, alkyl sulfosuccinic acids, alkyl naphthalene sulfonates, alkyl diphenyl ether disulfonic acids, and salts thereof.

[0080] Examples of the cationic surfactant include alkyldimethylammonium salts, alkylbenzyldimethylammonium salts, and alkylamine salts.

[0081] Examples of amphoteric surfactants include alkyl betaines and alkyl amine oxides.

[0082] Specific examples of nonionic surfactants include polyoxyalkylene alkyl ethers such as polyoxyethylene alkyl ethers, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkyl amines, and alkyl alkanolamides.

[0083] When the polishing composition contains a metal corrosion inhibitor, the content (active ingredient concentration) of the metal corrosion inhibitor is not particularly limited.For example, the lower limit of the content (active ingredient concentration) of the metal corrosion inhibitor is preferably 0.001g / L or more, more preferably 0.005g / L or more, and even more preferably 0.01g / L or more.In addition, the upper limit of the content (active ingredient concentration) of the metal corrosion inhibitor is preferably 10g / L or less, more preferably 5g / L or less, and even more preferably 2g / L or less.Within such a range, it is possible to prevent the dissolution of metal and suppress the deterioration of the surface condition such as the surface roughness of the polished surface.

[0084] (Preservatives and fungicides) Furthermore, examples of preservatives and antifungal agents that may be contained in the polishing composition if necessary include isothiazoline preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, paraoxybenzoic acid esters, and phenoxyethanol, etc. These preservatives and antifungal agents may be used alone or in combination of two or more kinds.

[0085] [Particularly preferred combinations of embodiments of the polishing composition] As described above, it must be understood that all combinations of the embodiments are disclosed in the present application, but particularly preferred combinations of the embodiments of the polishing composition will be described below.

[0086] That is, according to one embodiment of the present invention, the pH of the polishing composition is 2 to 5, 2 to 4 (4 or less), 2 to 3, or 2 or more and less than 2.9, and the zeta potential of the abrasive grains is adjusted to 15 mV or more and 32 mV or less over the entire range of pH 2 to 4, or pH 2 to 5. According to such an embodiment, the desired effect of the present invention can be efficiently achieved. In addition, in such an embodiment, the zeta potential of the abrasive grains is 25 mV or less, 22 mV or less, less than 22 mV, 21 mV or less, less than 20.7 mV, or 20.5 mV or less. In addition, in such an embodiment, the number of silanol groups per unit surface area of ​​the abrasive grains is 0 / nm 2More than 2.5 pieces / nm 2 In this embodiment, the polishing composition contains an acid, and the acid has a function of oxidizing a metal. In this embodiment, the number of carbon atoms in the alkyl group in the quaternary amine or its salt is 3 or less, or 2. According to this embodiment, the desired effect of the present invention can be significantly obtained.

[0087] In one embodiment of the present invention, the content of metal ions in the polishing composition is less than 0.01 mass ppm. By adopting such an embodiment, the zeta potential can be set within a desired range, and the polishing rate of tungsten can be improved.

[0088] In one embodiment of the present invention, the polishing composition does not contain hydrochloric acid. By adopting such an embodiment, the zeta potential can be set in a desired range, and the polishing rate of tungsten can be improved.

[0089] In one embodiment of the present invention, the polishing composition does not contain cyclodextrin. By adopting such an embodiment, the zeta potential can be set in a desired range, and the polishing rate of tungsten can be improved.

[0090] [Polished object] In one embodiment of the present invention, the object to be polished is preferably tungsten or a tungsten alloy (an alloy in which the mass ratio of tungsten is the largest among the metals constituting the alloy). In one embodiment of the present invention, the object to be polished includes a material selected from the group consisting of silicon nitride, silicon oxide, and polysilicon. Here, examples of the surface containing silicon oxide include surfaces containing silicon oxide films formed using TEOS as a raw material, HDP films, USG films, PSG films, BPSG films, RTO films, and the like. Among these, silicon oxide films formed using TEOS as a raw material are preferred. In particular, the present inventors have confirmed that the polishing rate of silicon oxide films (particularly silicon oxide films formed using TEOS as a raw material) is significantly improved in the pH range of 3 to 5 of the polishing composition. This is believed to be due to the electrostatic attraction caused by the surface potential of silica and silicon oxide, which are abrasive grains.

[0091] <Method of manufacturing the polishing composition> According to one embodiment of the present invention, the method for producing a polishing composition is not particularly limited. For example, a method for producing a polishing composition is provided, which includes mixing an abrasive grain, a quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof, and a liquid carrier, and includes adjusting the pH of the polishing composition to 2 to 5 and the zeta potential of the abrasive grain in the polishing composition to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4. The temperature at which each component is mixed is not particularly limited, but is preferably 10 to 40°C, and may be heated to increase the dissolution rate. The mixing time is also not particularly limited.

[0092] The zeta potential of the abrasive grains in the polishing composition can be adjusted to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4 by adjusting the amount of the quaternary amine or its salt, as described above, and then selecting whether or not to add other components or adjusting the amount of addition. As described above, the zeta potential of the abrasive grains is preferably 20 mV or more, but the addition of other components may result in a potential of less than 20 mV or a decrease in the polishing rate of the object to be polished.

[0093] <Polishing method and substrate manufacturing method> The present invention provides a method for polishing an object to be polished, which comprises polishing the object to be polished using the above-mentioned polishing composition. The present invention also provides a method for manufacturing a substrate, which comprises polishing a substrate before polishing using the polishing method. In one embodiment of the present invention, the substrate is preferably one of the objects listed in [object to be polished], such as tungsten, silicon oxide (silicon oxide derived from TEOS), etc.

[0094] In one embodiment of the present invention, the polishing method can be carried out using a polishing apparatus.

[0095] As a 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.

[0096] The polishing pad may be made of any material, including, without particular limitation, a general nonwoven fabric, polyurethane, porous fluororesin, etc. The polishing pad is preferably provided with grooves for storing the polishing liquid.

[0097] The polishing conditions are not particularly limited. For example, the rotation speed of the polishing platen is preferably 10 to 500 rpm, and the pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 to 10 psi.

[0098] The method of supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying the composition using a pump, etc. is adopted. There is no limit to the amount of the composition supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

[0099] 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 the substrate.

[0100] The present invention encompasses the following aspects and configurations.

[0101] 1. A polishing composition comprising an abrasive, a quaternary amine or a salt thereof having at least one alkyl group having two or more carbon atoms, and a liquid carrier, wherein the pH of the polishing composition is 2 to 5, and the zeta potential of the abrasive in the polishing composition is adjusted to be 15 mV or more and less than 40 mV over the entire pH range of 2 to 4.

[0102] 2. The polishing composition according to 1, wherein the zeta potential of the abrasive grains is adjusted to 15 mV or more and less than 40 mV over the entire range of pH 2 to 5.

[0103] 3. The polishing composition according to 1 or 2, wherein the zeta potential of the abrasive grains is adjusted to 32 mV or less.

[0104] 4. The quaternary amine or salt thereof is represented by the following formula:

[0105] [ka]

[0106] is shown in In this case, R 1 ~R 4 are each independently an alkyl group having 2 to 18 carbon atoms; Y - 4. The polishing composition according to any one of 1. to 3., wherein is a counter anion.

[0107] 5. The polishing composition according to 4., wherein the alkyl group has 2 to 4 carbon atoms.

[0108] 6. The number of silanol groups per unit surface area of ​​the abrasive grain is 0 / nm 2 More than 2.5 pieces / nm 2 The polishing composition according to any one of 1. to 5., which is:

[0109] 7. The number of silanol groups per unit surface area of ​​the abrasive grain is 2.5 / nm 26. The polishing composition according to claim 1, wherein the polishing composition has a viscosity of 1000:1 or more.

[0110] 8. The polishing composition according to 1., wherein the pH of the polishing composition is 4 or less, and the zeta potential of the abrasive grains is adjusted to 15 mV or more and 32 mV or less over the entire range of pH 2 to 4.

[0111] 9. The polishing composition according to any one of 1. to 8., which contains an acid.

[0112] 10. The polishing composition according to 9., wherein the acid has the function of oxidizing metal.

[0113] 11. A method for polishing an object to be polished, comprising polishing the object to be polished with the polishing composition according to any one of 1. to 10. EXAMPLES

[0114] 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. In the following examples, unless otherwise specified, the operations were performed under the conditions of room temperature (25°C) / relative humidity 40-50%RH.

[0115] <Preparation of Polishing Composition> Each polishing composition was prepared by stirring and mixing in water the abrasive grains (colloidal silica with an average primary particle size of 30 nm has an average secondary particle size of 61 nm, and colloidal silica with an average primary particle size of 35 nm has an average secondary particle size of 67 nm) with the composition shown in Table 1, an acid, a base, an oxidizing agent, and an additive (mixing temperature: about 25°C, mixing time: about 10 minutes). Note that "-" in Table 1 means that the component was not added.

[0116] <Average primary particle size of abrasive grains> The average primary particle size of the abrasive grains was calculated from the specific surface area of the abrasive grains by the BET method measured using "Flow SorbII 2300" manufactured by Micromeritics and the density of the abrasive grains.

[0117] <Average secondary particle size of abrasive grains> The average secondary particle size of the abrasive grains was calculated by the dynamic light scattering method measured using "UPA - UT151" manufactured by Microtrac.

[0118] <pH of polishing composition> The pH of the polishing composition was determined by using a glass electrode type hydrogen ion concentration indicator (model number: F - 23, manufactured by Horiba, Ltd.), performing three - point calibration using standard buffer solutions (phthalate pH buffer solution pH: 4.01 (25°C), neutral phosphate pH buffer solution pH: 6.86 (25°C), carbonate pH buffer solution pH: 10.01 (25°C)), putting the glass electrode into the polishing composition, and measuring the value after at least 2 minutes had passed and it had stabilized.

[0119] <Zeta (ζ) potential of abrasive grains> The polishing composition was subjected to ELS - Z2 manufactured by Otsuka Electronics Co., Ltd., and measurement was performed at a measurement temperature of 25°C using a flow cell by the laser Doppler method (electrophoretic light scattering measurement method). The zeta potential of the abrasive grains in the polishing composition was calculated by analyzing the obtained data with Smoluchowski's equation.

[0120] <W Polishing rate> Using the polishing composition, the thickness (film thickness) of the object to be polished before and after polishing was measured with a manual sheet resistor (VR - 120, manufactured by Nihon Kokusai Electric Co., Ltd.). The polishing rate (Removal Rate) (Å / min) was obtained by dividing the difference in the thickness (film thickness) of the object to be polished before and after polishing by the polishing time. A tungsten wafer (size: 32 mm × 32 mm) was used as the object to be polished.

[0121] (Polishing conditions) Polishing machine: Single - side CMP polishing machine (ENGIS) Polishing pad: Polyurethane pad (IC1010: manufactured by Rohm and Haas) Pressure: 2.4psi Platen rotation speed: 100 rpm Head (carrier) rotation speed: 100 rpm Flow rate of polishing composition: 100ml / min Dress: Diamond Disk (in-situ condition).

[0122] <Storage stability> The polishing composition was stored for one week at 80° C. The state of the polishing composition before and after storage was visually confirmed, and the stability was evaluated according to the following criteria. The obtained results are shown in Table 1.

[0123] (Stability evaluation criteria) ○: No change in the state of the polishing composition ×: Settling or aggregation (white turbidity) of the abrasive grains contained in the polishing composition occurred.

[0124] Specifically, X is considered to be a result reflecting aggregation of abrasive grains contained in the polishing composition, and is therefore undesirable from the standpoint of stability.

[0125] [Table 1-1]

[0126] [Table 1-2]

[0127] <Consideration> The polishing compositions of Examples maintain the stability as a composition and can improve the removal rate of tungsten, whereas the polishing compositions of Comparative Examples have poor stability as a composition and / or cannot improve the removal rate of tungsten.

[0128] Here, tungsten has a negative zeta potential in the acidic region. Specifically, it is about -25mV at pH2, about -40mV at pH3, about -50mV at pH4, and about -55mV at pH5. From the common sense of a person skilled in the art, the more the zeta potential of the abrasive grain surface and the zeta potential of the tungsten surface are opposite in sign and the greater the sum of the absolute values ​​of the zeta potentials, the greater the attraction between the abrasive grain and tungsten, and the higher the polishing rate should be. However, the polishing rate of the polishing composition of the embodiment using colloidal silica with a zeta potential adjusted to less than 40mV was significantly higher than the polishing rate of the polishing composition of the comparative example using cation-modified colloidal silica in which amino groups are introduced on the surface of colloidal silica and having a zeta potential of 40mV or more.

[0129] This result is contrary to the common knowledge of those skilled in the art; in other words, it can be said that the polishing composition of the present invention has an unexpected technical effect.

[0130] This application is based on Japanese Patent Application No. 2020-061354, filed on March 30, 2020, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A polishing composition for polishing tungsten, comprising: Abrasive grains and a quaternary amine having at least one alkyl group having two or more carbon atoms or a salt thereof; A liquid carrier; Including, The polishing composition has a pH of 2 to 5, The quaternary amine or salt thereof has the following formula: 【Chemistry 1】 is shown in In this case, R 1 to R 4 are each independently an alkyl group having 2 to 18 carbon atoms, and Y − is a counter anion, except for tetrabutylammonium hydroxide. The zeta potential of the abrasive grains in the polishing composition is adjusted to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4.

2. A polishing composition for polishing tungsten, comprising: Abrasive grains and a quaternary amine having at least one alkyl group having two or more carbon atoms or a salt thereof; A liquid carrier; Including, The polishing composition has a pH of 2 to 5, The quaternary amine or salt thereof has the following formula: 【Chemistry 2】 is shown in In this case, R 1 to R 4 are each independently an alkyl group having 2 to 18 carbon atoms, Y − is a counter anion, The zeta potential of the abrasive grains in the polishing composition is adjusted to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4, and the polishing composition does not contain an iron-containing compound.

3. 3. The polishing composition according to claim 1, wherein the zeta potential of the abrasive grains is adjusted to 15 mV or more and less than 40 mV over the entire range of pH 2 to 5.

4. 4. The polishing composition according to claim 1, wherein the abrasive grains have a zeta potential adjusted to 32 mV or less.

5. 5. The polishing composition according to claim 4, wherein the alkyl group has 2 to 4 carbon atoms.

6. The number of silanol groups per unit surface area of ​​the abrasive grain is 0 / nm ２ More than 2.5 particles / nm ２ The polishing composition according to any one of claims 1 to 5, wherein:

7. The number of silanol groups per unit surface area of ​​the abrasive grain is 2.5 / nm ２ The polishing composition according to any one of claims 1 to 5, wherein the polishing composition has a viscosity of 1000:1 or more.

8. 3. The polishing composition according to claim 1, wherein the pH of the polishing composition is 4 or less, and the zeta potential of the abrasive grains is adjusted to 15 mV or more and 32 mV or less over the entire range of pH 2 to 4.

9. A polishing composition described in any one of claims 1 to 8, wherein the abrasive grains are colloidal silica and do not contain either an aminosilane compound or a phosphonium silane compound incorporated inwardly relative to the outer surface of the colloidal silica.

10. The polishing composition according to any one of claims 1 to 9, which contains an acid.

11. The polishing composition according to claim 10, wherein the acid has a function of oxidizing a metal.

12. 12. A method for polishing an object to be polished, comprising polishing the object to be polished with the polishing composition according to claim 1.

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