JP2021161385A - Polishing composition - Google Patents

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

The present invention relates to a polishing composition.

Due to the high integration brought about by the miniaturization of the LSI manufacturing process, electronic devices such as computers have achieved high performance such as miniaturization, multi-functionality, and high speed. The chemical mechanical polishing (CMP) method is used in a new microfabrication technique accompanying the high integration of LSIs. The CMP method is a technique frequently used in the LSI manufacturing process, particularly in the process of forming a multilayer wiring, flattening an interlayer insulating film, forming a metal plug, and forming an embedded wiring (damer wiring).

In this process, a metal having excellent embedding property (particularly tungsten) is used as a material such as a plug for electrically joining the wirings in the vertical and vertical directions. In chemical mechanical polishing for forming a tungsten plug, the first polishing process mainly polishes the tungsten layer provided on the insulating film, and the second polishing for polishing the tungsten plug, the barrier metal film such as titanium, and the insulating film. The processing steps are carried out in sequence.

Regarding chemical mechanical polishing of such a tungsten layer and a tungsten plug (hereinafter, also referred to as “tungsten film”), a specific amine compound, a dispersion medium containing water, abrasive grains such as colloidal silica, an oxidizing agent, and the like. A composition for chemical mechanical polishing is known, which comprises the above (Patent Document 1). In Patent Document 1, in order to impart stability to abrasive grains under acidic conditions, a silane coupling agent such as aminopropyltrimethoxysilane is used on the surface of colloidal silica, and a cationic group is formed on the surface of colloidal silica. It is disclosed that it is preferable to use the introduced cationically modified colloidal silica (Patent Document 1 "0031"). Cationic modification of colloidal silica can be performed by adding a silane coupling agent such as aminopropyltrimethoxysilane to the dispersion liquid in which colloidal silica is dispersed.

JP-A-2017-61612

However, even if the composition for chemical mechanical polishing disclosed in Patent Document 1 is used, it cannot be said that the polishing speed of the tungsten film is sufficiently improved. It caused the problem that it did not lead to the improvement of productivity.

On the other hand, it is indispensable to maintain the stability of the composition as a basic physical characteristic required for the polishing composition.

Therefore, an object of the present invention is to provide a novel polishing composition capable of improving the polishing rate of a metal (particularly tungsten) and maintaining stability as a composition.

In order to solve the above problems, the present inventors have accumulated intensive research. As a result, the 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, and the pH of the polishing composition is high. , 2-5, and 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, by providing the polishing composition. , Found that the above problem can be solved.

The present invention can provide a novel polishing composition capable of improving the polishing rate of a metal (particularly tungsten) and maintaining stability as a composition.

Hereinafter, the present invention will be described. The present invention is not limited to the following embodiments. Unless otherwise specified, the operation and physical properties are measured under the conditions of room temperature (20 to 25 ° C.) / relative humidity of 40 to 50% RH. It should also be understood that all combinations of all lower limit and upper limit values disclosed herein are disclosed. In other words, it must be understood that it can be the basis for amendment. It should also be understood that all combinations of embodiments are disclosed herein. In other words, it must be understood that it can be the basis for amendment.

<Polishing composition>
In one embodiment of the present invention, the polishing composition comprises 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, and is used for polishing. A polishing composition in which the pH of the composition is 2 to 5, and 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. Is provided. According to such an embodiment, it is possible to provide a novel polishing composition which can improve the polishing rate of a metal (particularly tungsten) and maintain the stability as a composition.

Hereinafter, each component constituting the polishing composition will be described.

[Abrasive grain]
In one embodiment of the invention, the polishing composition comprises abrasive grains. The abrasive grains have an action of mechanically polishing the object to be polished, and improve the polishing speed of the object to be polished.

In one embodiment of the present invention, the abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the 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 the organic particles include polymethyl methacrylate (PMMA) particles. Among these abrasive grains, silica (particularly colloidal silica) is preferable.

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, further preferably 20 nm or more, and more preferably 25 nm or more. More preferred. 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 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.

In one embodiment of the present invention, the average secondary particle size of the abrasive grains is preferably 30 nm or more, more preferably 35 nm or more, further preferably 40 nm or more, and 45 nm or more. Is even more preferable, and 50 nm or more is even more preferable. 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 size of the abrasive grains is preferably 100 nm or less, more preferably 90 nm or less, and further 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 size of the abrasive grains may be a value measured by the method described in the examples.

In one embodiment of the present invention, the lower limit of the average degree of association (average secondary particle size / average primary particle size) of the abrasive grains is preferably 1.3 or more, and more preferably 1.4 or more. It is preferably 1.5 or more, and 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 that the polishing speed can be improved. In one embodiment of the present invention, the lower limit of the average degree of association (average secondary particle size / average primary particle size) of the abrasive grains is preferably 4.0 or less, and more preferably 3.5 or less. It is more preferably 3.0 or less, still 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 that sedimentation due to enlargement of particles and defects of the object to be polished can be suppressed.

In one embodiment of the present invention, the content (solid content concentration) of the abrasive grains in the polishing composition is preferably 0.1% by mass or more, and more preferably 1% by mass or more. It is more preferably 1.5% by mass or more, further preferably 2% by mass or more, further preferably 2.5% by mass or more, and 3.0% by mass or more. Is even more preferable, and 3.5% by mass or more is even more preferable. 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 concentration) of the abrasive grains in the polishing composition is preferably 10% by mass or less, more preferably 9% by mass or less. It is more preferably 8% by mass or less, further preferably 7% by mass or less, further 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.

As described above, in Patent Document 1, regarding chemical mechanical polishing of a tungsten film, it is preferable to use a cationically modified colloidal silica in which a cationic group is introduced into the surface of the colloidal silica using a silane coupling agent. There is a disclosure of what is. Here, as a method for producing colloidal silica having such a cationic group, aminoethyltrimethoxysilane, aminopropyltrimethoxysilane, aminoethyltriethoxy, as described in JP-A-2005-162533, are used. A silane coupling agent having an amino group such as silane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, aminobutyltriethoxysilane, or N-trimethoxysilylpropyl-N, N, N- A method of immobilizing a silane coupling agent having a fourth ammonium group such as trimethylammonium on the surface of abrasive grains is known. The abrasive grains in one embodiment of the present invention are different from the abrasive grains obtained by immobilizing such a silane coupling agent having an amino group or a silane coupling agent having a quaternary ammonium group on the surface of the abrasive grains. To.

(The number of silanol groups ^{exceeds 0 / nm 2} and 2.5 / nm ² or less)
In one embodiment of the present invention, the number of silanol groups per unit surface area of the abrasive grains ^{is more than 0 pieces / nm 2} and 2.5 pieces / nm ² or less. According to such an embodiment, the polishing speed of the object to be polished (particularly tungsten) can be improved.

In one embodiment of the present invention, the number of silanol groups is 2.4 / nm ² or less, 2.3 / nm ² or less, 2.2 / nm ² or less, 2.1 / nm ² or less, 2 It is 0.0 pieces / nm ² or less, 1.9 pieces / nm ² or less, or 1.8 pieces / nm ² or less. By having such an upper limit, the polishing speed 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 or more, 0.4 / nm ² or more, 0.6 / nm ² or more, 0.8 / nm ² or more, 1 .0 pieces / nm ² or more, 1.2 pieces / nm ² or more, 1.4 pieces / nm ² or more. Having such a lower limit has a technical effect of suppressing defects.

Here, in order to reduce the number of silanol groups per unit surface area of the abrasive grains to 2.5 / nm ² or less, it can be controlled by selecting a method for producing the abrasive grains, for example, heat treatment such as firing. It is preferable to do so. In one embodiment of the present invention, the firing treatment means, for example, holding abrasive grains (for example, silica) in an environment of 120 to 200 ° C. for 30 minutes or more. By performing such a heat treatment, the number of silanol groups on the surface of the abrasive grains can be reduced to a desired value such as ^{2.5 elements / nm 2 or less.} Unless such a special treatment is applied, the number of silanol groups on the surface of the abrasive grains does not become 2.5 / nm ² or less.

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 measuring method or calculation method.

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

In the above formula,
ρ represents the silanol group density (pieces / nm ² );
c represents the concentration (mol / L) of the sodium hydroxide solution used for the titration;
V is the volume (L) of the sodium hydroxide solution required to raise the pH from 4.0 to 9.0.
Represents;
N _A represents Avogadro constant (pieces / mol);
C represents the total mass (solid content) (g) of the abrasive grains;
^{S represents a weighted average value (nm 2} / g) of the BET specific surface area of the abrasive grains.

(The number of silanol groups is 2.5 / nm over ² )
In one embodiment of the present invention, the number of silanol groups per unit surface area of the abrasive grains is more than ^{2.5 / nm 2.} In one embodiment of the present invention, the number of silanol groups is 3.0 / nm ² or more, 4.0 / nm ² or more, or 5.0 / nm ² or more. Having such a lower limit has a technical effect of suppressing defects. In one embodiment of the present invention, the number of silanol groups is 8.0 / nm ² or less, 7.0 / nm ² or less, or 6.0 / nm ² or less. Having such an upper limit has a technical effect of improving the polishing rate.

[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 polishing composition comprises a quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof. A quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof may have a function of modifying the surface of the abrasive grains and adjusting the zeta potential on 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, it is not always possible to adjust the zeta potential to 15 mV or more and less than 40 mV over the entire range of pH 2 to 4 when the polishing composition contains the quaternary amine or a salt thereof. ..

Further, where it is essential that "having at least one alkyl group having 2 or more carbon atoms", even if tetramethylammonium hydroxide is used as the quaternary amine salt, the desired effect of the present invention can be obtained. Can't. Those skilled in the art can adjust the amount of such a quaternary amine or a salt thereof, and by selecting the addition of other components, the zeta potential can be adjusted to the entire pH range of 2 to 4. Over, it can be adjusted to 15 mV or more and less than 40 mV.

In one embodiment of the present invention, the polishing composition comprises a quaternary amine or a salt thereof having one, two, three, or four alkyl groups having two or more carbon atoms. In that case, the quaternary amine or salt thereof has 3, 2, 1, or 0 methyl groups. In one embodiment of the present invention, it is preferable to use a quaternary amine having three or more alkyl groups having two or more carbon atoms or a salt thereof.

In one embodiment of the present invention, the quaternary amine or a salt thereof 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 a salt thereof 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, and an alkyl group having 12 or less carbon atoms. It has 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 a liquid carrier. Above all, it is preferable that the quaternary amine or a salt thereof has an alkyl group having 3 or less carbon atoms in order to efficiently exert the desired effect of the present invention.

In one embodiment of the present invention, the alkyl group having 2 to 18 carbon atoms may be a linear group or may have a branched group, for example, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and the like. Examples thereof include sec-butyl group, tert-butyl group, hexyl group, octyl group and dodecyl group. However, it is preferable that it is linear from the viewpoint of efficiently producing the desired effect of the present invention.

In one embodiment of the present invention, examples of the salt include hydroxide ion and halide ion. Preferred examples of the halide ion include chloride ion and bromide ion.

In one embodiment of the present invention, the quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof has the following formula:

In this case, R ^{1 to} R ⁴ are independently alkyl groups having 2 to 18 carbon atoms, and Y ⁻ is a counter anion. According to such an embodiment, the desired effect of the present invention can be efficiently achieved.

In such an embodiment, R ^{1 to} R ⁴ are 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. Further, R ^{1 to} R ⁴ independently have 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, and 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 a 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 desired effect of the present invention can be achieved more efficiently.

In the above embodiment, Y ⁻ can be a hydroxide ion or a halide ion.

In one embodiment of the present invention, the content (active component concentration) of the quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof in the polishing composition is 0.001% by mass or more and 0. 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 be. 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 component concentration) of the quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof in the polishing composition is 5% by mass or less and 3% by mass or less. Below, 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 such an embodiment, there are technical effects of improving the polishing rate and good dispersion stability.

[PH of polishing composition]
In one embodiment of the present invention, the pH of the polishing composition is 2-5. 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 is 2.2 or higher, 2.4 or higher, 2.6 or higher, 2.8 or higher, 3.0 or higher, 3.2 or higher, 3.4. It can be 3.6 or more, or 3.8 or more. In one embodiment of the present invention, the pH of the polishing composition is 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. Below, it can be 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 the present specification, the pH of the polishing composition can be measured according to the method described in Examples.

In one embodiment of the invention, the polishing composition comprises a pH adjuster. As such a pH adjuster, an acid, a base, or a salt thereof can be used.

In one embodiment of the present invention, examples of the base include the above-mentioned 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, other compounds may be contained as the base. Examples of such bases include amines such as aliphatic amines and aromatic amines, ammonium solutions, organic bases such as tetraammonium hydroxide, hydroxides of alkali metals such as potassium hydroxide, and hydroxylation of Group 2 elements. Examples include substances, amino acids such as histidine, and ammonia. However, according to one embodiment of the present invention, the base does not contain other than the above-mentioned 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 speed can be improved and good dispersion stability can be realized. The term "not included" as used in the present specification is also included in the case where the corresponding component is not contained in the polishing composition at all and is contained in an amount of 0.5 mass ppm or less.

In one embodiment of the present invention, the acid includes periodic acid, hydrochloric acid, sulfuric acid, nitrate, hydrofluoric acid, boric acid, carbonic acid, hypophobic acid, phobic acid, inorganic acids such as phosphoric acid, and 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, heptanic 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, pimelli acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, Examples thereof include organic acids such as diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetracarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, and phenoxyacetic acid.

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

In one embodiment of the invention, the polishing composition comprises one acid and one base.

In one embodiment of the present invention, the acid content (active ingredient concentration) (two or more of them is the total) in the polishing composition is 0.001% by mass or more, 0.01% by mass or more, 0.03. It is 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 acid content (active ingredient concentration) (two or more of them is the total) 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, 0.25% by mass or less, 0.2% by mass or less, or 0.15% by mass or less. ..

In one embodiment of the present invention, the content of the base (active ingredient concentration) (the total of two or more types) in the polishing composition is 0.001% by mass or more, 0.01% by mass or more, 0.03. Mass% or more, 0.06% by mass or more, 0.08% by mass or more, 0.1% by mass or more, 0.15% by mass or more, 0.2% by mass or more, 0.3% by mass or more, 0.4% by mass % Or more, 0.5% by mass or more, or 0.6% by mass or more. In one embodiment of the present invention, the content of the base (active component concentration) (the total of two or more types) 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, 0.25% by mass or less, 0.2% by mass or less, or 0.15% by mass or less, 0 .12% by mass or less, or less than 0.12% by mass.

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

In one embodiment of the invention, the polishing composition comprises only an acid and a base, the base being only 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, and at least one of the above-mentioned bases, and the pH of the polishing composition is 2 to 5, 2 to 4.4, 2 to 4, 2 to 3, or It is adjusted to 2 or more and less than 2.9. By such an embodiment, the desired effect of the present invention can be efficiently achieved.

[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 range of pH 2 to 4. Unless the zeta potential of the abrasive grains in the polishing composition is maintained at 15 mV or higher over the entire range of pH 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 below 40 mV over the entire range of pH 2 to 4, the desired effect cannot be achieved.

In one embodiment of the present invention, 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 2-5. According to such an embodiment, the desired effect can be achieved over a wider range of pH.

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. Hereinafter, it is 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.

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. With such an embodiment, the desired effect of the present invention can be achieved more efficiently.

[Oxidant]
In one embodiment of the present invention, the polishing composition may contain an oxidizing agent. In one embodiment of the present invention, if the polishing composition does not contain an acid having a function of oxidizing a metal, an oxidizing agent may be contained.

In one embodiment of the present invention, the oxidizing agent is preferably a peroxide. Specific examples of such peroxides are not limited to the following, but are not limited to hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, potassium monosulfate and oxone. And so on. The above-mentioned oxidizing agent may be used alone or in combination of two or more.

In one embodiment of the present invention, the lower limit of the content (active ingredient concentration) of the oxidizing agent (the total of two or more kinds) in the polishing composition is 0.001% by mass or more and 0.005% by mass. As mentioned above, it is 0.01% by mass or more, 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more. In one embodiment of the present invention, the upper limit of the content (active ingredient concentration) of the oxidizing agent (the total of two or more kinds) in the polishing composition is 10% by mass or less, 5% by mass or less, and 3% by mass. % Or less, 1% by mass or less, or 0.5% by mass or less.

[Liquid carrier]
In one embodiment of the invention, the polishing composition comprises a liquid carrier. The liquid carrier has a function of dispersing or dissolving each component. More preferably, the liquid carrier is water only. Further, the liquid carrier may be a mixed solvent of water and an organic solvent for dispersion or dissolution of each component.

The water is preferably water containing as little impurities as possible from the viewpoint of contaminating the object to be polished and inhibiting the action of other components. Here, the purity of water can be increased by, for example, operations such as removal of impurity ions using an ion exchange resin, removal of foreign substances by a filter, and distillation. Specifically, as the water, for example, deionized water (ion-exchanged water), pure water, ultrapure water, distilled water and the like are preferably used.

[Other additives]
In one embodiment of the invention, the polishing composition may or may not contain other additives. If included, care should be taken to ensure that the zeta potential of the abrasive grains in the polishing composition is adjusted to greater than or equal to 15 mV and less than 40 mV over the entire range of pH 2-4. Specific examples of other additives include complexing agents, metal anticorrosive agents, preservatives, fungicides, reducing agents, water-soluble polymers, organic solvents for dissolving sparingly soluble organic substances, and the like. ..

Among the above other additives, a complexing agent, a metal anticorrosive agent, an antiseptic agent, and an antifungal agent will be described.

(Coordinating agent)
The complexing agent has an action of chemically etching the surface of the object to be polished, and can more effectively improve the polishing rate of the object to be polished by the polishing composition.

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

As the complexing agent, the inorganic acid or the salt of the organic acid may be used. 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 action can be expected. Examples of such salts include, for example, potassium chloride, sodium sulfate, potassium nitrate, potassium carbonate, potassium tetrafluoroborate, potassium pyrophosphate, potassium oxalate, trisodium citrate, (+)-potassium tartrate, hexafluoro. Examples include potassium phosphate and the like.

Specific examples of the nitrile compound include acetonitrile, aminoacetonitrile, propionitrile, butyronitrile, isobutyronitrile, benzonitrile, glutaloginitrile, methoxynitrile, and the like.

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, sarcosin, Ornitine, lysine, taurine, serine, threonine, homoserine, tyrosine, bicin, tricine, 3,5-diiodo-tyrosine, β- (3,4-dihydroxyphenyl) -alanine, tyrosin, 4-hydroxy-proline, cysteine, methionine , Ethionin, lanthionin, cystathionine, cystine, tyrosine, aspartic acid, glutamic acid, S- (carboxymethyl) -cysteine, 4-aminobutyric acid, asparagine, glutamine, azaserine, arginine, canabanine, citrulin, δ-hydroxy-lysine, creatine , Histidine, 1-methyl-histidine, 3-methyl-histidine and tryptophan.

Specific examples of the chelating agent include nitrilotriacetic acid, diethylenetriaminetetraacetic acid, ethylenediaminetetraacetic acid, N, N, N-trimethylenephosphonic acid, ethylenediamine-N, N, N', N'-tetramethylenesulfonic acid, and transcyclohexane. Diamine tetraacetic acid, 1,2-diaminopropane tetraacetic acid, glycol ether diaminetetraacetic acid, ethylenediamine orthohydroxyphenylacetic acid, ethylenediaminediaminediamine (SS form), N- (2-carboxylate ethyl) -L-aspartic acid, β -Alanindiacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, N, N'-bis (2-hydroxybenzyl) ethylenediamine-N, N'-diacetic acid , 1,2-Dihydroxybenzene-4,6-disulfonic acid and the like.

When the polishing composition contains a complexing agent, the content of the complexing agent (active ingredient concentration) 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 exerts an effect even in a small amount, but is preferably 0.001 g / L or more, preferably 0.01 g / L. The above is more preferable, and 1 g / L or more is further preferable. 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 further preferably 10 g / L or less. Within 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.

(Metal corrosion inhibitor)
The metal anticorrosive agent acts to prevent deterioration of the surface condition such as surface roughness of the polished surface by preventing the dissolution of the metal.

The metal corrosion inhibitor is a heterocyclic compound or a surfactant. The number of heterocyclic members in the heterocyclic compound is not particularly limited. Further, the heterocyclic compound may be a monocyclic compound or a polycyclic compound having a condensed ring. The metal anticorrosive agent may be used alone or in combination of two or more. Further, as the metal anticorrosive agent, a commercially available product or a synthetic product may be used.

Specific examples of the heterocyclic compound include, for example, pyrrole compound, pyrazole compound, imidazole compound, triazole compound, tetrazole compound, pyridine compound, pyrazine compound, pyridazine compound, pyrindin compound, indridin compound, indole compound, isoindole compound, and indazole. Compounds, purine compounds, quinolidine compounds, quinoline compounds, isoquinoline compounds, naphthylidine compounds, phthalazine compounds, quinoxalin compounds, quinazoline compounds, cinnoline compounds, buteridine compounds, thiazole compounds, isothiazole compounds, oxazole compounds, isooxazole compounds, frazane compounds, etc. Examples include nitrogen-containing heterocyclic compounds.

More specific examples include, for example, 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-methyl Pyrazole, 3-amino-5-methylpyrazole, 4-amino-pyrazolo [3,4-d] pyrimidine, alloprinol, 4-chloro-1H-pyrazolo [3,4-D] pyrimidin, 3,4-dihydroxy-6 Examples thereof include −methylpyrazolo (3,4-B) -pyridine, 6-methyl-1H-pyrazolo [3,4-b] pyridine-3-amine and the like.

Examples of imidazole compounds include, for example, imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 1,2-dimethylpyrazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, benzimidazole, 5,6-dimethylbenzimidazole, 2-aminobenzoimidazole, 2-chlorobenzoimidazole, 2-methylbenzimidazole, 2- (1-hydroxyethyl) benzimidazole, 2-hydroxybenzimidazole, 2-phenylbenzimidazole, 2 , 5-Dimethylbenzimidazole, 5-methylbenzimidazole, 5-nitrobenzimidazole and the like.

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-triazole-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) Bentriazole, 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 can be mentioned.

Examples of the tetrazole compound include, for example, 1H-tetrazole, 5-methyltetrazole, 5-aminotetrazole, 5-phenyltetrazole and the like.

Examples of indazole compounds include, for example, 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, 3-carboxy-5-methyl-1H-indazole and the like can be mentioned.

Examples of indole compounds include, for example, 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-Hydroxy-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, 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 etc. can be mentioned.

Further, examples of the surfactant used as a metal anticorrosive agent include anionic surfactants, cationic surfactants and amphoteric surfactants.

Examples of anionic surfactants include polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfate ester, alkyl sulfate ester, polyoxyethylene alkyl ether sulfuric acid, alkyl ether sulfuric acid, alkylbenzene sulfonic acid, and alkyl phosphate ester. , Polyoxyethylene alkyl phosphate ester, polyoxyethylene sulfosuccinic acid, alkyl sulfosuccinic acid, alkylnaphthalene sulfonic acid, alkyldiphenyl ether disulfonic acid, salts thereof and the like.

Examples of cationic surfactants include alkyldimethylammonium salts, alkylbenzyldimethylammonium salts, alkylamine salts and the like.

Examples of amphoteric surfactants include alkyl betaines, alkyl amine oxides and the like.

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 alkylamines, and alkyl alkanols. Examples include amide.

When the polishing composition contains a metal anticorrosive agent, the content (active ingredient concentration) of the metal anticorrosive agent is not particularly limited. For example, the lower limit of the content (active ingredient concentration) of the metal anticorrosive agent is preferably 0.001 g / L or more, more preferably 0.005 g / L or more, and 0.01 g / L or more. Is even more preferable. The upper limit of the content (active ingredient concentration) of the metal anticorrosive agent is preferably 10 g / L or less, more preferably 5 g / L or less, and further preferably 2 g / L or less. Within such a range, it is possible to prevent the metal from melting and suppress deterioration of the surface condition such as surface roughness of the polished surface.

(Preservatives and fungicides)
Further, examples of preservatives and fungicides that can be contained in the polishing composition if necessary include 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3. Examples thereof include isothiazolinone-based preservatives such as −ON, paraoxybenzoic acid esters, and phenoxyethanol. These preservatives and fungicides may be used alone or in combination of two or more.

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

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 abrasive grains. The zeta potential of the above 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. Further, in such an embodiment, the zeta potential of the abrasive grains is 25 mV or less, 22 mV or less, 22 mV or less, 21 mV or less, 20.7 mV or less, or 20.5 mV or less. Further, in such an embodiment, the number of silanol groups per unit surface area of the abrasive grains ^{is more than 0 elements / nm 2} and 2.5 elements / nm ² or less. Further, in such an embodiment, the polishing composition contains an acid, and the acid has a function of oxidizing a metal. Further, in such an embodiment, the number of carbon atoms of the alkyl group in the quaternary amine or its salt is 3 or less, or 2. According to such an embodiment, the desired effect of the present invention can be remarkably obtained.

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

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

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

[Object to be polished]
In one embodiment of the present invention, tungsten or a tungsten alloy (an alloy having the largest proportion of the mass of tungsten in the metal constituting the alloy) is suitable as the object to be polished. 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, as the surface containing silicon oxide, a surface containing a silicon oxide film, an HDP film, a USG film, a PSG film, a BPSG film, an RTO film, etc. formed from TEOS as a raw material can be mentioned. Among these, a silicon oxide film formed from TEOS as a raw material is preferable. In particular, the present inventors have confirmed that the polishing rate of the silicon oxide film (particularly, the silicon oxide film formed from TEOS as a raw material) is remarkably improved in the region where the pH of the polishing composition is 3 to 5. There is. It is considered that this is because the electrostatic attraction action works by the surface potentials of silica and silicon oxide which are abrasive grains.

<Manufacturing method of polishing composition>
According to one embodiment of the present invention, the method for producing the polishing composition is not particularly limited. For example, the polishing composition comprises 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 the pH of the polishing composition is set to 2 to 5. Provided is a method for producing a polishing composition, which comprises adjusting 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. 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. Further, the mixing time is not particularly limited.

In order 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, the amount of the quaternary amine or a salt thereof is adjusted as described above. Therefore, it can be realized by selecting whether or not the addition of other components is necessary or adjusting the amount of addition. As described above, the zeta potential of the abrasive grains is preferably 20 mV or more, but depending on the addition of other components, the zeta potential may be less than 20 mV, or the polishing speed of the object to be polished may decrease.

<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 composition for polishing. Further, in the present invention, there is provided a method for manufacturing a substrate, which comprises polishing the substrate before polishing by using the polishing method. In one embodiment of the present invention, as the substrate, the objects listed in [Abrasion target] such as tungsten and silicon oxide (silicon oxide derived from TEOS) are suitable.

In one embodiment of the present invention, the polishing method can be carried out by using a polishing device.

As a polishing device, a holder for holding a substrate or the like having an object to be polished and a motor or the like whose rotation speed can be changed are attached, and a polishing platen to which a polishing pad (polishing cloth) can be attached is generally provided. Polishing equipment can be used.

As the polishing pad, general non-woven fabric, polyurethane, porous fluororesin and the like can be used without particular limitation. It is preferable that the polishing pad is grooved so that the polishing liquid can be collected.

The polishing conditions are also not particularly limited. For example, the rotation speed of the polishing surface plate 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.

The method of supplying the polishing composition to the polishing pad is also not particularly limited, and for example, a method of continuously supplying the polishing composition with a pump or the like is adopted. Although the supply amount is not limited, it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

After the polishing is completed, the substrate is washed in running water, and the water droplets adhering to the substrate are wiped off by a spin dryer or the like and dried to obtain the substrate.

The present invention includes the following aspects and forms.

1. 1. The 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, and the pH of the polishing composition is 2 to 2. 5. The polishing composition, wherein 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. 1. 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. The polishing composition according to.

3. 3. 1. The zeta potential of the abrasive grains is adjusted to 32 mV or less. Or 2. The polishing composition according to.

4. The quaternary amine or a salt thereof has the following formula:

Indicated by
At this time, R ^{1 to} R ⁴ are independently alkyl groups having 2 to 18 carbon atoms, and Y ⁻ is a counter anion. ~ 3. The polishing composition according to any one of the above items.

5. 4. The alkyl group has 2 to 4 carbon atoms. The polishing composition according to.

6. 1. The number of silanol groups per unit surface area of the abrasive grains ^{is more than 0 / nm 2} and 2.5 / nm ² or less. ~ 5. The polishing composition according to any one of.

7. 1. The number of silanol groups per unit surface area of the abrasive grains is more than ^{2.5 / nm 2.} ~ 5. The polishing composition according to any one of.

8. 1. 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. The polishing composition according to.

9. Contains acid 1. ~ 8. The polishing composition according to any one of.

10. 9. The acid has a function of oxidizing a metal. The polishing composition according to.

11. 1. 1. -10. A method for polishing an object to be polished, which comprises polishing the object to be polished using the polishing composition according to any one of.

The present invention will be described in more detail with reference to 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 "part" mean "mass%" and "part by mass", respectively. Further, in the following examples, unless otherwise specified, the operation was performed under the conditions of room temperature (25 ° C.) / relative humidity of 40 to 50% RH.

<Preparation of polishing composition>
Abrasive grains (coloidal silica having an average primary particle size of 30 nm has an average secondary particle size of 61 nm and an average primary particle size of 35 nm have an average secondary particle size of 67 nm) having the compositions shown in Table 1. Each polishing composition was prepared by stirring and mixing the acid, the base, the oxidizing agent, and the additive in water (mixing temperature: about 25 ° C., mixing time: about 10 minutes). .. In addition, "-" in Table 1 means that the component was not added.

<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 Micromeritex Co., Ltd. and the density of the abrasive grains.

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

<pH of polishing composition>
For the pH of the polishing composition, a glass electrode type hydrogen ion concentration indicator (Horiba Seisakusho Co., Ltd. model number: F-23) was used, and a standard buffer solution (phthalate pH buffer solution pH: 4.01 (25 ° C.)) was used. ), Neutral phosphate pH buffer pH: 6.86 (25 ° C), carbonate pH buffer pH: 10.01 (25 ° C)), and then polish the glass electrode after three-point calibration. It was determined by putting it in the composition and measuring the value after it became stable after 2 minutes or more.

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

<W polishing speed>
Using the polishing composition, the thickness (film thickness) of the object to be polished before and after polishing was measured by a manual sheet resistor (VR-120, manufactured by Hitachi Kokusai Electric Inc.). The polishing rate (Removal Rate) (Å / min) was determined 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.

(Polishing conditions)
Polishing machine: Single-sided CMP polishing machine (ENGIS)
Polishing pad: Polyurethane pad (IC1010: Roam and Haas)
Pressure: 2.4psi
Platen (surface plate) rotation speed: 100 rpm
Head (carrier) rotation speed: 100 rpm
Flow rate of polishing composition: 100 ml / min
Dress: Diamond Disk (in-situ condition).

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

(Stability evaluation criteria)
◯: No change in the state of the polishing composition ×: Sedimentation or aggregation (white turbidity) of abrasive grains contained in the polishing composition occurred.

Specifically, x is considered to be the result of reflecting the aggregation of abrasive grains contained in the polishing composition, and is therefore not preferable from the viewpoint of stability.

<Discussion>
The polishing composition of the example can maintain the stability as a composition and can improve the polishing rate of tungsten. On the other hand, the polishing composition of the comparative example has poor stability as a composition and / or cannot improve the polishing rate of tungsten.

Here, tungsten has a negative zeta potential in the acidic region. Specifically, it is about -25 mV at pH 2, about -40 mV at pH 3, about -50 mV at pH 4, and about -55 mV at pH 5. According to the common wisdom of those skilled in the art, the greater the sum of the zeta potentials on the surface of the abrasive grains and the zeta potentials on the surface of tungsten, and the greater the sum of the absolute values of each zeta potential, the more the abrasive grains and tungsten The attractive force should be increased and the polishing speed should be improved. However, the zeta potential is adjusted to less than 40 mV as compared with the polishing rate of the polishing composition of the comparative example in which the zeta potential is 40 mV or more using the cation-modified colloidal silica having an amino group introduced on the surface of the colloidal silica. The polishing rate of the polishing composition of the example using the colloidal silica was significantly higher.

This result is contrary to the common sense 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.

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 (11)

A polishing composition
Abrasive grains and
A quaternary amine having at least one alkyl group having 2 or more carbon atoms or a salt thereof,
With liquid carriers
Including
The pH of the polishing composition is 2 to 5, and the polishing composition has a pH of 2 to 5.
A polishing composition in which 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. 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. The polishing composition according to claim 1 or 2, wherein the zeta potential of the abrasive grains is adjusted to 32 mV or less. The quaternary amine or a salt thereof has the following formula:

Indicated by
At this time, the polishing according to any one of claims 1 to 3 ^{, wherein R 1 to} R ⁴ are independently alkyl groups having 2 to 18 carbon atoms and Y ^{− is a counter anion.} Composition. The polishing composition according to claim 4, wherein the alkyl group has 2 to 4 carbon atoms. The polishing composition according to any one of claims 1 to 5, wherein the number of silanol groups per unit surface area of the abrasive grains ^{is more than 0 pieces / nm 2} and 2.5 pieces / nm ^{2 or less.} The polishing composition according to any one of claims 1 to 5, wherein the number of silanol groups per unit surface area of the abrasive grains ^{is more than 2.5 / nm 2.} 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. Composition. The polishing composition according to any one of claims 1 to 8, which comprises an acid. The polishing composition according to claim 9, wherein the acid has a function of oxidizing a metal. A method for polishing an object to be polished, which comprises polishing the object to be polished using the polishing composition according to any one of claims 1 to 10.