JP2024141119A - Polishing composition, polishing method, and method for producing semiconductor substrate - Google Patents

Abstract

[Problem] To provide a polishing composition that can polish a polycrystalline silicon film at high speed and suppress the polishing rate of at least one of a silicon nitride film and a silicon oxide film. [Solution] The polishing composition contains abrasive grains and an amine oxide compound, and has a pH of more than 5 and not more than 10, the abrasive grains have a negative zeta potential in the polishing composition and an average degree of association of 3.0 or more and 6.0 or less, and the amine oxide compound has a structure represented by formula (1). [Selected Figure] None

Description

The present invention relates to a polishing composition, a polishing method, and a method for manufacturing a semiconductor substrate.

In recent years, with the trend toward multi-layer wiring on the surface of semiconductor substrates, a technique known as chemical mechanical polishing (CMP) is used to polish and flatten semiconductor substrates when manufacturing devices.

CMP has been applied to various processes in semiconductor manufacturing, and one example of this is its application to the gate formation process in transistor fabrication. When fabricating transistors, materials such as metal, silicon, silicon oxide, polycrystalline silicon, and silicon nitride may be polished, and there is a demand for polishing each material at high speed to improve productivity. In order to meet such demands, for example, Patent Document 1 discloses a technology that aims to improve the polishing speed of polycrystalline silicon.

JP 2013-041992 A

In examining the application of CMP to each step in semiconductor manufacturing, the present inventors discovered that in some cases it is preferable from a manufacturing perspective to polish a polycrystalline silicon film at high speed in the presence of a silicon nitride film or silicon oxide film. On the other hand, they discovered that in some cases it is preferable from a manufacturing perspective to keep the polishing speed as low as possible for silicon nitride films or silicon oxide films. However, there is still no polishing composition that can polish a polycrystalline silicon film at high speed while suppressing the polishing speed for a silicon nitride film or silicon oxide film.

The present invention aims to provide a polishing composition that can polish polycrystalline silicon films at high speeds while suppressing the polishing rate of at least one of silicon nitride films and silicon oxide films.

In order to solve the above problems, the present inventors have conducted extensive research. As a result, a polishing composition containing abrasive grains and an amine oxide compound and having a pH of more than 5 and not more than 10, in which the abrasive grains have a negative zeta potential in the polishing composition and an average degree of association of 3.0 or more and 6.0 or less, and the amine oxide compound is represented by the following formula (1):

In formula (1),
R ¹ to R ³ are each independently an alkyl group having 1 to less than 14 carbon atoms, and at least one of R ¹ to R ³ is an alkyl group having more than 8 and less than 14 carbon atoms;
It has been found that the above problems can be solved by a polishing composition represented by the formula (I), and thus the present invention has been completed.

The present invention provides a polishing composition that can polish polycrystalline silicon films at high speeds while suppressing the polishing rate of at least one of silicon nitride films and silicon oxide films.

The following describes in detail the embodiments for carrying out the present invention. The embodiments shown here are merely examples for embodying the technical ideas of the present invention, and do not limit the present invention. Therefore, all other possible embodiments, methods of use, and operational techniques that can be conceived by those skilled in the art without departing from the gist of the present invention are included in the scope and gist of the present invention, as well as the invention described in the claims and their equivalents. The embodiments described in this specification can be combined in any way to form other embodiments. In addition, unless otherwise specified in this specification, operations and measurements of physical properties are performed at room temperature (20°C to 25°C) and relative humidity of 40% RH to 60% RH.

The present invention relates to a polishing composition that contains an abrasive grain and an amine oxide compound and has a pH of more than 5 and not more than 10, the abrasive grain has a negative zeta potential in the polishing composition and has an average degree of association of 3.0 or more and 6.0 or less, and the amine oxide compound is represented by the following formula (1):

In formula (1),
R ¹ to R ³ are each independently an alkyl group having 1 to less than 14 carbon atoms, and at least one of R ¹ to R ³ is an alkyl group having more than 8 and less than 14 carbon atoms;
This polishing composition is represented by the formula: Such a polishing composition can polish a polycrystalline silicon film at high speed, and suppress the polishing rate of at least one of a silicon nitride film and a silicon oxide film. The inventors of the present invention presume the mechanism by which such an effect is obtained by the present invention as follows. However, the following mechanism is merely speculation, and the scope of the present invention is not limited thereby.

In the present invention, the object to be polished preferably includes at least a polycrystalline silicon film and at least one of a silicon nitride film and a silicon oxide film. According to the polishing composition of the present invention, the polycrystalline silicon film of the object to be polished is polished at a high speed, and at least one of a silicon nitride film and a silicon oxide film has an effect of suppressing the polishing speed. In a polishing composition having a pH of more than 5 and not more than 10, abrasive grains having a negative zeta potential are easily adsorbed to a polycrystalline silicon film, a silicon nitride film and a silicon oxide film, and thus the number of abrasive grains present on the surface of a polycrystalline silicon film, a silicon nitride film and a silicon oxide film during polishing increases. At this time, when the degree of association of the abrasive grains is high (for example, in the case of abrasive grains having a degree of association of 3.0 or more and 6.0 or less), the shape of the abrasive grains becomes rod-like and tends to remain on the surface of the object to be polished. This further improves the polishing speed of a polycrystalline silicon film, a silicon nitride film and a silicon oxide film. However, if the polishing speed of silicon nitride film and silicon oxide film is increased, the ratio of the polishing speed of polycrystalline silicon to the polishing speed of silicon nitride (polishing speed of polycrystalline silicon/polishing speed of silicon nitride) and the ratio of the polishing speed of polycrystalline silicon to the polishing speed of silicon oxide (polishing speed of polycrystalline silicon/polishing speed of silicon oxide) will be lowered. The inventors have found that the polishing composition of the present invention, which contains a specific amine oxide compound at a pH of more than 5 and not more than 10, improves the polishing speed of polycrystalline silicon film and suppresses or maintains the polishing speed of silicon nitride film and silicon oxide film. In the following, the ratio of the polishing speed of polycrystalline silicon to the polishing speed of silicon nitride or silicon oxide is also referred to as the "polishing selectivity of polycrystalline silicon".

In other words, it is believed that certain amine oxide compounds are more likely to be adsorbed onto polycrystalline silicon films at certain pH levels. When an amine oxide compound is adsorbed onto a polycrystalline silicon film, the unshared electron pair on the nitrogen atom of the amine oxide compound interacts with the silicon-silicon bonds on the surface of the polycrystalline silicon film, embrittling the surface of the polycrystalline silicon film. This makes it easier for the abrasive grains on the surface of the polycrystalline silicon film to act on the polycrystalline silicon film, improving the polishing speed of the polycrystalline silicon film.

On the other hand, the above-mentioned interaction of certain amine oxide compounds with silicon nitride films and silicon oxide films is not as strong as with polycrystalline silicon films, and the effect of embrittling the silicon nitride film surface and silicon oxide film surface is weak. In other words, silicon nitride films and silicon oxide films are chemically stable in the presence of the polishing composition of the present invention, and the pH and the potential of the abrasive grains are dominant, and it is speculated that as a result, the polishing selectivity of polycrystalline silicon can be improved by improving the polishing speed of polycrystalline silicon films. As described above, it is believed that the polishing composition of the present invention can polish polycrystalline silicon films at high speed and suppress the polishing speed of silicon nitride films and silicon oxide films.

As described above, the inventors have discovered that a polishing composition having a pH greater than 5 and not greater than 10, containing abrasive grains with a negative zeta potential and a degree of association of 3.0 or more and 6.0 or less, and a specific amine oxide compound, can solve the problem of polishing polycrystalline silicon films at high speeds while suppressing the polishing rate of silicon nitride films and silicon oxide films.

Note that the above mechanism is based on speculation, and the present invention is in no way limited to the above mechanism.

[Polished object]
The object to be polished according to the present invention preferably includes a polycrystalline silicon (polysilicon) film and at least one of a silicon nitride (Si ₃ N ₄ ) film and a silicon oxide (SiO ₂ ) film. That is, the polishing composition according to a preferred embodiment of the present invention is used for polishing an object to be polished that includes a polycrystalline silicon film and at least one of a silicon nitride film and a silicon oxide film.

According to one embodiment of the present invention, the use of the object to be polished is not limited, and examples include semiconductor substrates, solar cell substrates, and TFTs for liquid crystal displays (LCDs). It is also suitable for use as test wafers, monitor wafers, transport check wafers, dummy wafers, etc. for these.

The object to be polished according to the present invention may contain other materials in addition to the polycrystalline silicon film, silicon nitride film, and silicon oxide film, such as silicon carbonitride (Si _x C _y N _z ), doped polycrystalline silicon (doped polysilicon), undoped amorphous silicon, metal, SiGe, etc.

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

Examples of films containing metals include tungsten (W) film, titanium nitride (TiN) film, ruthenium (Ru) film, platinum (Pt) film, silver (Ag) film, gold (Au) film, hafnium (Hf) film, cobalt (Co) film, palladium (Pd), iridium (Ir), osmium (Os), nickel (Ni) film, copper (Cu) film, aluminum (Al) film, and tantalum (Ta) film.

Furthermore, there are no particular limitations on the shape of the object to be polished. In one embodiment of the present invention, the polishing composition can be preferably used for polishing an object to be polished that has a flat surface, such as a plate or polyhedron.

[Abrasive grain]
The polishing composition according to the present invention contains abrasive grains. The abrasive grains contained in the polishing composition according to the present invention have a negative zeta potential. When the zeta potential of the abrasive grains is 0 mV or positive, the polishing speed of the polycrystalline silicon film is lowered, or the polishing speed of the silicon nitride film or silicon oxide film is increased, and as a result, the polishing speed of the polycrystalline silicon film is lower than the polishing speed of the silicon nitride film or silicon oxide film (the polishing selectivity of polycrystalline silicon is lowered). The abrasive grains are preferably anion-modified silica (silica having an anionic group), and more preferably anion-modified colloidal silica (colloidal silica having an anionic group). The abrasive grains may be used alone or in combination of two or more kinds. In addition, the abrasive grains may be commercially available products or synthetic products.

The polishing composition according to the present invention preferably contains anion-modified colloidal silica as an abrasive. Anion-modified colloidal silica is colloidal silica whose surface is modified with anionic groups, and in the polishing composition, it has the effect of mechanically polishing the object to be polished.

Preferred examples of anion-modified colloidal silica include colloidal silica having anionic groups, such as carboxyl groups, sulfonic acid groups, phosphonic acid groups, and aluminic acid groups, immobilized on the surface. There are no particular limitations on the method for producing colloidal silica having such anionic groups, and examples of the method include a method of reacting colloidal silica with a silane coupling agent having an anionic group at the end.

As a specific example, if sulfonic acid groups are to be fixed to colloidal silica, this can be done by the method described in, for example, "Sulfonic acid-functionalized silica through of thiol groups", Chem. Commun. 246-247 (2003). Specifically, a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, is coupled to colloidal silica, and then the thiol group is oxidized with hydrogen peroxide to obtain colloidal silica with sulfonic acid groups fixed to the surface (sulfonic acid-modified colloidal silica).

Carboxylic groups can be immobilized on colloidal silica by, for example, the method described in "Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel", Chemistry Letters, 3, 228-229 (2000). Specifically, a silane coupling agent containing a photoreactive 2-nitrobenzyl ester is coupled to colloidal silica, followed by light irradiation, to obtain colloidal silica with carboxyl groups immobilized on the surface (carboxylic acid-modified colloidal silica).

The lower limit of the zeta potential of the abrasive grains in the polishing composition is preferably -50 mV or more, more preferably -45 mV or more, even more preferably -40 mV or more, particularly preferably -35 mV or more, and most preferably -30 mV or more. The upper limit of the zeta potential of the abrasive grains in the polishing composition is preferably -1 mV or less, more preferably -5 mV or less, even more preferably -10 mV or less, particularly preferably -15 mV or less, and most preferably -20 mV or less. That is, the zeta potential of the abrasive grains in the polishing composition is preferably -50 mV or more and -1 mV or less, more preferably -45 mV or more and -5 mV or less, even more preferably -40 mV or more and -10 mV or less, particularly preferably -35 mV or more and -15 mV or less, and most preferably -30 mV or more and -20 mV or less.

Abrasive grains having the above-mentioned zeta potential can polish polycrystalline silicon films at a higher polishing rate, and the polishing rate of polycrystalline silicon films is higher than the polishing rate of silicon nitride films or silicon oxide films (the polishing selectivity of polycrystalline silicon is higher).

The average primary particle size of the abrasive grains is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. As the average primary particle size of the abrasive grains increases, the polishing speed of the polycrystalline silicon film increases. Also, the average primary particle size of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. As the average primary particle size of the abrasive grains decreases, the polishing speed of the polycrystalline silicon film becomes higher compared to the polishing speed of the silicon nitride film or silicon oxide film (the polishing selectivity of polycrystalline silicon becomes higher).

That is, the average primary particle size of the abrasive grains is preferably 1 nm or more and 100 nm or less, more preferably 3 nm or more and 50 nm or less, and even more preferably 5 nm or more and 30 nm or less. The average primary particle size of the abrasive grains can be calculated, for example, based on the specific surface area (SA) of the abrasive grains calculated by the BET method and the density of the abrasive grains.

The average secondary particle diameter of the abrasive grains is preferably 15 nm or more, more preferably 20 nm or more, and even more preferably 25 nm or more. As the average secondary particle diameter of the abrasive grains increases, the resistance during polishing decreases, enabling stable polishing of the polycrystalline silicon film. The average secondary particle diameter of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less. As the average secondary particle diameter of the abrasive grains decreases, the surface area per unit mass of the abrasive grains increases, the frequency of contact with the object to be polished increases, and the polishing speed of the polycrystalline silicon film increases. That is, the average secondary particle diameter of the abrasive grains is preferably 15 nm or more and 200 nm or less, more preferably 20 nm or more and 150 nm or less, and even more preferably 25 nm or more and 100 nm or less. The average secondary particle diameter of the abrasive grains can be measured, for example, by a dynamic light scattering method represented by a laser diffraction scattering method, and specifically, the value measured by the method described in the examples is adopted.

The ratio of the average secondary particle diameter to the average primary particle diameter of the abrasive grains (average secondary particle diameter/average primary particle diameter, hereinafter also referred to as the "average degree of association") is 3.0 or more and 6.0 or less. If the average degree of association of the abrasive grains is less than 3.0, the abrasive grains tend to roll on the object to be polished, and the abrasive grains escape from between the polishing pad and the object to be polished, making efficient polishing impossible and reducing the polishing rate of the polycrystalline silicon film. If the average degree of association of the abrasive grains exceeds 6.0, the abrasive grains tend to remain on the surface of the object to be polished, improving the polishing rate of the silicon nitride film or silicon oxide film, and reducing the polishing rate of the polycrystalline silicon film relative to the polishing rate of the silicon nitride film or silicon oxide film (polishing selectivity of the polycrystalline silicon film). The average degree of association of the abrasive grains is preferably 3.5 or more, more preferably 3.6 or more, even more preferably 3.7 or more, particularly preferably 3.8 or more, and most preferably 4.0 or more. As the average degree of association of the abrasive grains increases, the polishing speed of the polycrystalline silicon film increases. The average degree of association of the abrasive grains is preferably 5.9 or less, more preferably 5.8 or less, even more preferably 5.5 or less, particularly preferably 5.0 or less, and most preferably 4.8 or less. As the average degree of association of the abrasive grains decreases, the polishing speed of the polycrystalline silicon film becomes higher than the polishing speed of the silicon nitride film or silicon oxide film (the polishing selectivity of polycrystalline silicon becomes higher). That is, the average degree of association of the abrasive grains is preferably 3.5 to 5.9, more preferably 3.6 to 5.8, even more preferably 3.7 to 5.5, particularly preferably 3.8 to 5.0, and most preferably 4.0 to 4.8.

The average degree of association of the abrasive grains is obtained by dividing the average secondary particle size of the abrasive grains by the average primary particle size.

The shape of the primary particles of the abrasive grains is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and square prisms, cylinders, bale shapes in which the center of a cylinder is more bulging than the ends, donut shapes with a disk penetrating the center, plate shapes, so-called cocoon shapes with a constriction in the center, so-called confetti shapes with multiple protrusions on the surface, and rugby ball shapes, and various other shapes are not particularly limited.

The shape of the secondary particles of the abrasive grains is not particularly limited, and may be a peanut shape in which two primary particles of the abrasive grains are connected in parallel, a rosary shape in which three or more primary particles of the abrasive grains are connected in parallel, a three-dimensional spherical shape in which three or more primary particles are integrated, or a polygonal shape in which three or more primary particles are integrated and flat (e.g., triangular, rectangular, rhombic, hexagonal, etc.). Of these, the rosary shape is preferred from the viewpoint of achieving a good balance between the polishing speed of the polycrystalline silicon film and the polishing speed of the silicon nitride film or silicon oxide film.

The size of the abrasive grains (average primary particle size, average secondary particle size, aspect ratio, primary particle shape, secondary particle shape, etc.) can be appropriately controlled by selecting the manufacturing method of the abrasive grains, etc.

In this specification, the zeta potential of the abrasive grains is a value measured by the method described in the Examples. The zeta potential of the abrasive grains can be adjusted by the amount of anionic groups contained in the abrasive grains, the pH of the polishing composition, etc.

In the polishing composition according to the present invention, the abrasive grains may be used alone or in a mixture of two or more kinds. In addition, the abrasive grains to be used may be either commercially available products or synthetic products.

The content (concentration) of the abrasive grains in the polishing composition is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably more than 0.5% by mass, based on the total mass of the polishing composition. The upper limit of the content (concentration) of the abrasive grains in the polishing composition is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 4% by mass or less, and particularly preferably less than 4% by mass, based on the total mass of the polishing composition. That is, the content (concentration) of the abrasive grains in the polishing composition is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, even more preferably 0.5% by mass or more and 4% by mass or less, and particularly preferably more than 0.5% by mass and less than 4% by mass. In one embodiment, the content (concentration) of the abrasive grains in the polishing composition is 0.01% by mass or more and 3.0% by mass or less.

If the content of abrasive grains is within this range, the polishing speed of the polycrystalline silicon film will be higher than the polishing speed of the silicon nitride film or silicon oxide film (the polishing selectivity of polycrystalline silicon will be higher). When the polishing composition contains two or more types of abrasive grains, the content of the abrasive grains refers to the total amount of these.

The polishing composition of the present invention may further contain other abrasive grains besides anion-modified silica, so long as the abrasive grains have a negative zeta potential in the polishing composition, within a range that does not impair the effects of the present invention. Such other abrasive grains may be any of inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of inorganic particles include unmodified silica, particles made of metal oxides such as alumina, ceria, and titania, silicon nitride particles, silicon carbide particles, and boron nitride particles. Specific examples of organic particles include polymethylmethacrylate (PMMA) particles.

[Amine oxide compounds]
The polishing composition of the present invention contains an amine oxide compound represented by the following formula (1).

In formula (1), R ¹ to R ³ are each independently an alkyl group having 1 or more and less than 14 carbon atoms, and at least one of R ¹ to R ³ is an alkyl group having more than 8 and less than 14 carbon atoms. The alkyl group having 1 or more and less than 14 carbon atoms may be any of a linear alkyl group, branched alkyl group, or cyclic alkyl group having 1 or more and less than 14 carbon atoms, but a linear alkyl group having 1 or more and less than 14 carbon atoms is preferred.

Specific examples of alkyl groups having 1 or more and less than 14 carbon atoms include, for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tet-butyl, pentyl, isopentyl, neopentyl, 2-ethylhexyl, hexyl, heptyl, octyl, 3,7-dimethyloctyl, nonyl, decyl, undecyl, dodecyl (lauryl), and tridecyl groups.

Here, in formula (1), at least one of R ¹ to R ³ is an alkyl group having more than 8 and less than 14 carbon atoms. That is, in the amine oxide compound according to the present invention, at least one of the three alkyl groups has more than 8 and less than 14 carbon atoms. By having at least one alkyl group having more than 8 and less than 14 carbon atoms, the amine oxide compound can easily act on the polycrystalline silicon film, and the polishing rate of the polycrystalline silicon film can be improved. The alkyl group other than the alkyl group having more than 8 and less than 14 carbon atoms may be an alkyl group having 1 to 8 carbon atoms. The amine oxide compound is required to have at least one alkyl group having more than 8 and less than 14 carbon atoms, and may have two or three alkyl groups having more than 8 and less than 14 carbon atoms, but preferably has only one alkyl group having more than 8 and less than 14 carbon atoms.

Examples of alkyl groups having more than 8 and less than 14 carbon atoms include nonyl, decyl, undecyl, dodecyl (lauryl), and tridecyl groups. As alkyl groups having more than 8 and less than 14 carbon atoms, alkyl groups having 9 to 13 carbon atoms are more preferred, alkyl groups having 10 to 12 carbon atoms are even more preferred, and alkyl groups having 10 or 12 carbon atoms are particularly preferred.

In one embodiment, the amine oxide compound has only one alkyl group having more than 8 and less than 14 carbon atoms. Thus, this form of amine oxide compound has one alkyl group having more than 8 and less than 14 carbon atoms and two alkyl groups having from 1 to 8 carbon atoms. That is, in one embodiment, in formula (1), R ¹ and R ² are each independently an alkyl group having from 1 to 8 carbon atoms, and R ³ is an alkyl group having more than 8 and less than 14 carbon atoms.

In one embodiment, the amine oxide compound has three alkyl groups having more than 8 and less than 14 carbon atoms. That is, in one embodiment, in formula (1), R ¹ to R ³ are each independently an alkyl group having more than 8 and less than 14 carbon atoms.

In one embodiment, the amine oxide compound has two alkyl groups having more than 8 and less than 14 carbon atoms and one alkyl group having from 1 to 8 carbon atoms. That is, in one embodiment, in formula (1), ^R1 and ^R2 are each independently an alkyl group having more than 8 and less than 14 carbon atoms, and ^R3 is an alkyl group having from 1 to 8 carbon atoms.

In a preferred embodiment, the amine oxide compound has one alkyl group having more than 8 and less than 14 carbon atoms, and two alkyl groups having 1 to 8 carbon atoms. The amine oxide compound has the above composition, which provides a good balance between the polishing speed of the polycrystalline silicon film and the polishing speed of the silicon nitride film or silicon oxide film.

Specific examples of amine oxide compounds include decyl dimethylamine oxide, methyl didecylamine oxide, decyl diethylamine oxide, ethyl didecylamine oxide, decyl dipropylamine oxide, propyl didecylamine oxide, dodecyl dimethylamine oxide, methyl didodecylamine oxide, dodecyl diethylamine oxide, ethyl didodecylamine oxide, dodecyl dipropylamine oxide, propyl didodecylamine oxide, tridecyl dimethylamine oxide, methyl ditridecylamine oxide, tridecyl diethylamine oxide, ethyl ditridecylamine oxide, tri(tridecyl)amine oxide, and decyl di(tridecyl)amine oxide. Among these, the amine oxide compound is preferably decyl dimethylamine oxide, methyl didecylamine oxide, decyl diethylamine oxide, ethyl didecylamine oxide, dodecyl dimethylamine oxide, methyl didodecylamine oxide, dodecyl diethylamine oxide, or ethyl didodecylamine oxide, from the viewpoint of the polishing selectivity of the polycrystalline silicon film. The amine oxide compound is more preferably at least one of decyl dimethylamine oxide and dodecyl dimethylamine oxide.

In the polishing composition according to the present invention, the amine oxide compound may be used alone or in a mixture of two or more kinds. In addition, the amine oxide compound may be a commercially available product or a synthetic product.

The content (concentration) of the amine oxide compound in the polishing composition is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, even more preferably 0.005% by mass or more, particularly preferably 0.01% by mass or more, and most preferably 0.03% by mass or more, based on the total mass of the polishing composition. The upper limit of the content (concentration) of the amine oxide compound in the polishing composition is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, particularly preferably 0.2% by mass or less, and most preferably 0.1% by mass or less, based on the total mass of the polishing composition. That is, the content (concentration) of the amine oxide compound is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.002% by mass or more and 1% by mass or less, even more preferably 0.005% by mass or more and 0.5% by mass or less, particularly preferably 0.01% by mass or more and 0.2% by mass or less, and most preferably 0.03% by mass or less and 0.1% by mass or less, relative to the total mass of the polishing composition. In one embodiment, the content (concentration) of the amine oxide compound in the polishing composition is 0.01% by mass or more and 0.1% by mass or less.

When the content (concentration) of the amine oxide compound is within this range, the polishing speed of the polycrystalline silicon film is higher than the polishing speed of the silicon nitride film or silicon oxide film (the polishing selectivity of polycrystalline silicon is higher). When the polishing composition contains two or more types of amine oxide compounds, the content (concentration) of the amine oxide compound refers to the total amount of these.

[Compound Having Nitrogen Atom and Phosphonic Acid Group]
The polishing composition according to the present invention may further contain a compound having a nitrogen atom and a phosphonic acid group. The compound having a nitrogen atom and a phosphonic acid group can embrittle the polycrystalline silicon film, further improve the polishing speed of the polycrystalline silicon film, and further improve the polishing selectivity of the polycrystalline silicon.

The compound having a nitrogen atom and a phosphonic acid group is, for example, at least one selected from the group consisting of nitrilotrismethylenephosphonic acid or a salt thereof, alendronic acid or a salt thereof trihydrate, alendronic acid or a salt thereof, (1-aminoethyl)phosphonic acid or a salt thereof, N,N,N,N-ethylenediaminetetrakis(methylenephosphonic acid) or a salt thereof, and glycine N,N-bis(methylenephosphonic acid) or a salt thereof. Of these, nitrilotrismethylenephosphonic acid or a salt thereof, and N,N,N,N-ethylenediaminetetrakis(methylenephosphonic acid) or a salt thereof are preferred.

In the polishing composition according to the present invention, the compound having a nitrogen atom and a phosphonic acid group may be used alone or in combination of two or more kinds. In addition, the compound having a nitrogen atom and a phosphonic acid group may be a commercially available product or a synthetic product.

The content (concentration) of the compound having a nitrogen atom and a phosphonic acid group in the polishing composition is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, even more preferably 0.005% by mass or more, particularly preferably 0.01% by mass or more, and most preferably 0.03% by mass or more, based on the total mass of the polishing composition. The upper limit of the content (concentration) of the compound having a nitrogen atom and a phosphonic acid group in the polishing composition is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, particularly preferably 0.2% by mass or less, and most preferably 0.1% by mass or less, based on the total mass of the polishing composition. That is, the content (concentration) of the compound having a nitrogen atom and a phosphonic acid group is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.002% by mass or more and 1% by mass or less, even more preferably 0.005% by mass or more and 0.5% by mass or less, particularly preferably 0.01% by mass or more and 0.2% by mass or less, and most preferably 0.03% by mass or less and 0.1% by mass or less, based on the total mass of the polishing composition. In one embodiment, the content (concentration) of the compound having a nitrogen atom and a phosphonic acid group in the polishing composition is 0.01% by mass or more and 0.1% by mass or less.

[pH and pH adjusters]
The pH of the polishing composition according to the present invention is more than 5 and 10 or less. When the pH of the polishing composition is 5 or less, the adsorption of the abrasive grains to the object to be polished in the polishing composition is reduced, and the polishing rate of the polycrystalline silicon film is reduced. When the pH of the polishing composition is more than 10, the polishing rate of the silicon nitride film and the silicon oxide film is increased, and the polishing selectivity of the polycrystalline silicon is reduced. The pH of the polishing composition is preferably 5.5 or more, more preferably 5.8 or more, even more preferably 6.0 or more, particularly preferably 6.5 or more, and most preferably 6.8 or more. The pH of the polishing composition is preferably 9.8 or less, more preferably 9.5 or less, even more preferably 8.0 or less, particularly preferably 7.8 or less, and most preferably 7.5 or less. That is, the pH of the polishing composition is preferably 5.5 or more and 9.8 or less, more preferably 5.8 or more and 9.5 or less, even more preferably 6.0 or more and 8.0 or less, particularly preferably 6.5 or more and 7.8 or less, and most preferably 6.8 or more and 7.5 or less. In one embodiment, the pH of the polishing composition is 6 or more and less than 9. If the pH of the polishing composition is in such a range, the polishing rate of the polycrystalline silicon film becomes higher than the polishing rate of the silicon nitride film or the silicon oxide film (the polishing selectivity of the polycrystalline silicon becomes higher).

The polishing composition of the present invention may contain a pH adjuster to adjust the pH to more than 5 and not more than 10. Examples of pH adjusters include inorganic acids, organic acids, and alkalis. These may be used alone or in combination of two or more.

Specific examples of inorganic acids that can be used as pH adjusters include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Of these, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid are preferred, and nitric acid is more preferred. By using nitric acid as a pH adjuster, the polishing selectivity for the polycrystalline silicon film can be improved, and the polishing speed for the polycrystalline silicon film can be suitably improved.

Specific examples of organic acids that can be used as pH adjusters include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid, methoxyacetic acid, methoxyphenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid, 10-camphorsulfonic acid, and isethionic acid.

In place of or in combination with an inorganic or organic acid, a salt such as an alkali metal salt of an inorganic or organic acid may be used as a pH adjuster. In the case of a combination of a weak acid and a strong base, a strong acid and a weak base, or a weak acid and a weak base, a pH buffering effect can be expected.

Specific examples of alkalis that can be used as pH adjusters include ammonia, hydroxides of Group 1 elements (e.g., sodium hydroxide, potassium hydroxide), hydroxides of Group 2 elements (e.g., barium hydroxide), quaternary ammonium hydroxides (e.g., tetramethylammonium hydroxide), or salts thereof. Examples of salts include carbonates, hydrogen carbonates, sulfates, acetates, and the like. Of these, ammonia and hydroxides of Group 1 elements are preferred, and ammonia is more preferred. By using ammonia as a pH adjuster, the polishing selectivity for polycrystalline silicon films can be improved, and the polishing speed for polycrystalline silicon films can be suitably improved.

In one embodiment, the polishing composition of the present invention further contains one or more pH adjusters selected from nitric acid and ammonia. This can improve the polishing selectivity for the polycrystalline silicon film and can favorably improve the polishing rate for the polycrystalline silicon film.

The content of the pH adjuster can be selected by appropriately adjusting it within the range in which the effects of the present invention are achieved. The pH of the polishing composition can be measured, for example, with a pH meter (for example, a pH meter (model number: LAQUA) manufactured by Horiba, Ltd.).

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

From the viewpoint of not inhibiting the action of the components contained in the polishing composition, it is preferable that the dispersion medium contains as few impurities as possible. Specifically, it is more preferable to use pure water or ultrapure water that has been filtered to remove foreign matter after removing impurity ions with an ion exchange resin, or distilled water.

[Other ingredients]
The polishing composition according to the present invention may further contain known additives that can be used in polishing compositions, such as complexing agents, preservatives, fungicides, oxidizing agents, surfactants, water-soluble polymers, and dissolution aids, within the range that does not inhibit the effects of the present invention. The pH of the polishing composition according to the present invention is more than 5 and 10 or less. For this reason, it is more preferable that the polishing composition contains a fungicide. That is, in one embodiment of the present invention, the polishing composition is substantially composed of at least one selected from the group consisting of abrasive grains, an amine oxide compound, a dispersion medium, and a compound having a nitrogen atom and a phosphonic acid group, a pH adjuster, and a fungicide. In one embodiment of the present invention, the polishing composition is substantially composed of at least one selected from the group consisting of abrasive grains, an amine oxide compound, a dispersion medium, and a compound having a nitrogen atom and a phosphonic acid group, a pH adjuster, and a fungicide. Here, "the polishing composition is substantially composed of at least one selected from the group consisting of abrasive grains, an amine oxide compound, a dispersion medium, and a compound having a nitrogen atom and a phosphonic acid group, a pH adjuster, and an antifungal agent" means that the total content of at least one selected from the group consisting of abrasive grains, an amine oxide compound, a dispersion medium, a compound having a nitrogen atom and a phosphonic acid group, a pH adjuster, and an antifungal agent is more than 99% by mass (upper limit: 100% by mass) relative to the polishing composition. Preferably, the polishing composition is composed of abrasive grains, an amine oxide compound, a dispersion medium, a compound having a nitrogen atom and a phosphonic acid group, a pH adjuster, and an antifungal agent (the total content = 100% by mass).

There are no particular limitations on the antifungal agent (preservative), and it can be appropriately selected according to the desired use and purpose. Specific examples include isothiazoline preservatives such as 1,2-benzisothiazol-3(2H)-one (BIT), 2-methyl-4-isothiazolin-3-one, and 5-chloro-2-methyl-4-isothiazolin-3-one, as well as phenoxyethanol.

[Polishing method and manufacturing method of semiconductor substrate]
The polishing composition according to the present invention is preferably used for polishing an object to be polished, for example, containing polycrystalline silicon and at least one of silicon nitride and silicon oxide. Thus, the present invention provides a polishing method comprising polishing an object to be polished with the polishing composition according to the present invention. The present invention also provides a method for producing a semiconductor substrate comprising polishing a semiconductor substrate with the polishing composition according to the present invention. The present invention also provides a method for producing a semiconductor substrate comprising polishing a semiconductor substrate by the polishing method according to the present invention.

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

As the polishing pad, general nonwoven fabric, polyurethane, porous fluororesin, etc. can be used without any particular restrictions. It is preferable that the polishing pad has grooves to allow the polishing liquid to accumulate.

Regarding the polishing conditions, for example, the rotation speed of the polishing platen and carrier is preferably 10 rpm (0.17 s ⁻¹ ) to 500 rpm (8.33 s ⁻¹ ), and the pressure applied to the substrate having the object to be polished (polishing pressure) is preferably 0.5 psi (3.4 kPa) to 10 psi (68.9 kPa).

There are no particular limitations on the method of supplying the polishing composition to the polishing pad, and for example, a method of continuously supplying it using a pump or the like is used. There is no limit to the amount of supply, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

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

The polishing composition of the present invention may be a one-component type or a multi-component type, such as a two-component type. The polishing composition of the present invention may also be prepared by diluting the stock solution of the polishing composition, for example, 3 times or more (or, for example, 5 times or more) with a diluent such as water.

[Polishing speed]
When polishing is performed using the polishing composition of the present invention, the polishing rate of the polycrystalline silicon film is preferably 1500 Å/min to 7000 Å/min, more preferably 2000 Å/min to 6800 Å/min, even more preferably 2200 Å/min to 6500 Å/min, and particularly preferably 2500 Å/min to 6000 Å/min. When polishing is performed using the polishing composition of the present invention, the polishing rate of the silicon nitride film and/or silicon oxide film is preferably 150 Å/min or less, more preferably 100 Å/min or less, even more preferably 50 Å/min or less, and particularly preferably 40 Å/min or less. The lower limit of the polishing rate of the silicon nitride film and/or silicon oxide film is not particularly limited, but is practically 5 Å/min or more.

[Polishing selectivity]
When the polishing composition according to the present invention is used for polishing an object to be polished that contains polycrystalline silicon and silicon nitride, the ratio of the polishing rate of polycrystalline silicon to the polishing rate of silicon nitride (polycrystalline silicon/silicon nitride) is preferably 50 or more, more preferably 60 or more, even more preferably 70 or more, particularly preferably 75 or more, and most preferably 80 or more. When the polishing composition according to the present invention is used for polishing an object to be polished that contains polycrystalline silicon and silicon oxide, the ratio of the polishing rate of polycrystalline silicon to the polishing rate of silicon oxide (polycrystalline silicon/silicon oxide) is preferably 40 or more, more preferably 50 or more, even more preferably 55 or more, particularly preferably 60 or more, and most preferably 70 or more.

Although the embodiments of the present invention have been described in detail, it is clear that the same are illustrative and exemplary and are not limiting, and the scope of the present invention should be interpreted by the appended claims.

The present invention includes the following aspects and configurations:

[1] A polishing composition comprising an abrasive grain and an amine oxide compound, and having a pH of more than 5 and not more than 10,
the abrasive grains have a negative zeta potential in the polishing composition and an average degree of association of 3.0 or more and 6.0 or less;
The amine oxide compound is represented by the following formula (1):

In formula (1),
R ¹ to R ³ are each independently an alkyl group having 1 to 12 carbon atoms, and at least one of R ¹ to R ³ is an alkyl group having more than 8 and less than 14 carbon atoms;
The polishing composition represented by the formula:

[2] The polishing composition according to [1] above, in which the amine oxide compound has only one alkyl group having more than 8 and less than 14 carbon atoms.

[3] The polishing composition according to [1] or [2] above, wherein the amine oxide compound is at least one of decyl dimethylamine oxide and dodecyl dimethylamine oxide.

[4] The polishing composition according to any one of [1] to [3] above, further containing a compound having a nitrogen atom and a phosphonic acid group.

[5] The polishing composition according to any one of [1] to [4] above, wherein the compound having a nitrogen atom and a phosphonic acid group is at least one selected from the group consisting of nitrilotrismethylenephosphonic acid or a salt thereof, alendronic acid or a salt thereof trihydrate, alendronic acid or a salt thereof, (1-aminoethyl)phosphonic acid or a salt thereof, N,N,N,N-ethylenediaminetetrakis(methylenephosphonic acid) or a salt thereof, and glycine N,N-bis(methylenephosphonic acid) or a salt thereof.

[6] The polishing composition according to any one of [1] to [5] above, wherein the abrasive grains are anion-modified colloidal silica.

[7] The polishing composition according to any one of [1] to [6] above, having a pH of 6 or more and less than 9.

[8] The polishing composition according to any one of [1] to [7] above, further comprising one or more pH adjusters selected from nitric acid and ammonia.

[9] The polishing composition according to any one of [1] to [8] above, which is used for polishing an object to be polished that contains polycrystalline silicon and at least one of silicon nitride and silicon oxide.

[10] The polishing composition according to [9] above, which is used for polishing an object containing polycrystalline silicon and silicon nitride, and the ratio of the polishing speed of the polycrystalline silicon to the polishing speed of the silicon nitride (polishing speed of polycrystalline silicon/polishing speed of silicon nitride) is 80 or more.

[11] The polishing composition according to [9] above, which is used for polishing an object containing polycrystalline silicon and silicon oxide, and the ratio of the polishing rate of the polycrystalline silicon to the polishing rate of the silicon oxide (polishing rate of polycrystalline silicon/polishing rate of silicon oxide) is 60 or more.

[12] A polishing method comprising a step of polishing an object containing polycrystalline silicon and at least one of silicon nitride and silicon oxide using the polishing composition described in any one of [1] to [11] above.

[13] A method for manufacturing a semiconductor substrate, comprising a step of polishing a semiconductor substrate containing polycrystalline silicon and at least one of silicon nitride and silicon oxide by the polishing method described in [12] above.

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.

<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 silica particles measured by the BET method using "Flow Sorb II 2300" manufactured by Micromeritics, and the density of the abrasive grains.

<Average secondary particle size of abrasive grains>
The average secondary particle diameter of the abrasive grains was measured as the volume average particle diameter (arithmetic mean diameter based on volume; Mv) using a dynamic light scattering particle diameter/particle size distribution device UPA-UTI151 (manufactured by Nikkiso Co., Ltd.).

<Average degree of association of abrasive grains>
The average degree of association of the abrasive grains was calculated by dividing the value of the average secondary particle size of the abrasive grains by the value of the average primary particle size of the abrasive grains.

<Zeta potential of abrasive grains>
The zeta potential of the abrasive grains in the polishing composition was measured by subjecting the polishing composition to a Zetasizer Nano manufactured by Malvern Panalytical and measuring it by a laser Doppler method (electrophoretic light scattering measurement method) at a measurement temperature of 25°C, and calculating it by analyzing the obtained data using the Smoluchowski formula.

<Shape of abrasive grain>
The shape of the abrasive grains was analyzed by observing images of the abrasive grains using a HD-2700 scanning transmission electron microscope (manufactured by Hitachi High-Tech Corporation) according to the following procedure.

After dispersing the abrasive grains in alcohol (abrasive grain concentration 0.01% by mass), the dried sample was placed in a transmission electron microscope (TEM) and irradiated with an electron beam at 5.0 kV. Several observation fields were photographed at magnifications from 50,000 to 200,000 times.

In the TEM images taken, the shape of the abrasive grains was confirmed based on the following criteria.
(Standards for abrasive grain shape)
When grains having the following shapes are observed in TEM images at 50% or more by number, the grains are judged to have that shape.
- Bead-shaped: Three or more spherical abrasive grains are connected together in a row, with the grains at the ends not connected to each other. - Peanut-shaped: Two spherical abrasive grains are connected together in a row.

<pH of Polishing Composition>
The pH of the polishing composition was measured using a glass electrode type hydrogen ion concentration indicator (Model No. F-23, manufactured by Horiba, Ltd.) and three-point calibration was performed 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)). The glass electrode was then placed in the polishing composition and the value after stabilization for at least 2 minutes was recorded as the pH value.

<Electrical Conductivity of Polishing Composition>
The electrical conductivity (EC) of the polishing composition was measured using a tabletop electrical conductivity meter (manufactured by Horiba, Ltd., model number: DS-71 LAQUA (registered trademark)).

[Preparation of abrasive grains]
[Preparation of Abrasive Grains 1 to 3]
As the anion-modified colloidal silica, sulfonic acid-modified colloidal silica was used (Abrasive grains 1 to 3 were prepared by the method described in “Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups”, Chem. Commun. 246-247 (2003)).

Abrasive grain 1: average primary particle size: 22 nm, average secondary particle size: 80 nm, average degree of association: 3.6
Abrasive grain 2: average primary particle size: 11 nm, average secondary particle size: 50 nm, average degree of association: 4.5
Abrasive grain 3: average primary particle size: 35 nm, average secondary particle size: 70 nm, average degree of association: 2.

[Preparation of Abrasive Grain 4]
In the same manner as in Example 1 of JP 2005-162533 A, cation-modified colloidal silica as abrasive grains 4 (average primary particle size: 22 nm, average secondary particle size: 80 nm, average degree of association: 3.6) was prepared using γ-aminopropyltriethoxysilane (APTES) at a concentration of 0.113 mmol (0.113 mM) as a silane coupling agent per 1 L of an aqueous dispersion of silica sol (silica concentration=20% by mass).

[Preparation of Polishing Composition]
Example 1
The above-obtained abrasive grain 1 (anion-modified colloidal silica) was added to the dispersion medium, pure water, at room temperature (25° C.) to a final concentration of 2% by mass. Furthermore, 2-methyl-4-isothiazolin-3-one (manufactured by THE DOW CHEMICAL COMPANY) was added as an antifungal agent to a final concentration of 0.014 mM to obtain a mixed solution.

Then, decyldimethylamine oxide (manufactured by Lion Specialty Chemical Co., Ltd.) was added as an amine oxide compound to a final concentration of 0.05 mass%, and ammonia was added as a pH adjuster to a pH of 9, followed by stirring and mixing for 30 minutes at room temperature (25°C) to prepare polishing composition A1. The pH of the resulting polishing composition A1 was measured to be 9, and the electrical conductivity was 2 mS/cm.

The zeta potential of the abrasive grain 1 (anion-modified colloidal silica) in the resulting polishing composition was measured according to the method described above and found to be -35 mV. Furthermore, the particle size of the abrasive grain 1 (anion-modified colloidal silica) in the polishing composition was the same as the particle size of the abrasive grain 1 (anion-modified colloidal silica) used.

(Examples 2 to 5, Comparative Examples 1 to 8)
Polishing compositions A2 to A5 of Examples 2 to 5 and polishing compositions B1 to B8 of Comparative Examples 1 to 8 were prepared in the same manner as in Example 1, except that the type and concentration of each component, and the pH were changed as shown in Table 1 below. The compound having a nitrogen atom and a phosphonic acid group (shown as "additive" in Table 1) was added before the addition of the pH adjuster, and the pH was adjusted with the pH adjuster after the addition. Nitrilotrismethylenephosphonic acid (product name: Chelest PH-320, manufactured by Chelest Co., Ltd.) was used as the compound having a nitrogen atom and a phosphonic acid group. The composition of each polishing composition is shown in Table 1 below. "-" in Table 1 below indicates that the agent was not used. The pH of each polishing composition and the particle size of the abrasive grains in each polishing composition were measured, and the values shown in Table 1 were obtained.

[evaluation]
<Evaluation of Polishing Rate of Polishing Composition>
Using each of the Polishing Compositions A1 to A5 and B1 to B8, the surface of each object to be polished was polished under the following conditions. The following objects to be polished (1) to (3) were prepared.

(1) Polycrystalline silicon film (poly-Si film): A silicon wafer with a 5000 Å thick polycrystalline silicon film formed on the surface. (2) Silicon nitride film (Si ₃ N ₄ film): A silicon wafer (200 mm, blanket wafer) with a 2000 Å thick silicon nitride film formed on the surface.
(3) Silicon oxide film (TEOS film): A silicon wafer (200 mm, blanket wafer) having a TEOS type silicon oxide (SiO ₂ ) film formed on its surface to a thickness of 10,000 Å.

(Polishing Equipment and Polishing Conditions)
Polishing equipment: Applied Materials 200mm CMP single-sided polishing equipment Mirra
Polishing pad: Nitta Haas Co., Ltd. Hard polyurethane pad IC1010
Polishing pressure: 4.0 psi (1 psi = 6894.76 Pa)
Polishing platen rotation speed: 47 rpm
Head (carrier) rotation speed: 43 rpm
Supply of polishing composition: flowing Polishing composition supply amount: 200 mL/min Polishing time: 60 seconds.

(Calculation of Polishing Rate)
The thickness of each object to be polished before and after polishing was measured using an optical film thickness measuring device (ASET-f5x: manufactured by KLA Tencor Co., Ltd.) The film thickness was measured using an optical film thickness measuring device (ASET-f5x: manufactured by KLA Tencor Co., Ltd.).

The polishing rate for each object to be polished was calculated by dividing the difference in film thickness before and after polishing [(thickness before polishing)-(thickness after polishing)] by the polishing time. For polycrystalline silicon film, a polishing rate of 1500 Å/min or more is practical, but 2000 Å/min or more is preferable. For the polishing rate ratio between polycrystalline silicon film and silicon nitride film, a polishing rate of polycrystalline silicon film/polishing rate of silicon nitride film (poly-Si/Si ₃ N ₄ in Table 1) of 50 or more is practical. For the polishing rate ratio between polycrystalline silicon film and silicon oxide film, a polishing rate of polycrystalline silicon film/polishing rate of silicon oxide film (poly-Si/TEOS in Table 1) of 40 or more is practical.

The above evaluation results are also shown in Table 1. In Table 1, the polycrystalline silicon film is indicated as "poly-Si", the silicon nitride film is indicated as "Si ₃ N ₄ ", and the TEOS film is indicated as "SiO ₂ ".

As is clear from Table 1 above, the polishing compositions of the Examples have a high polishing rate for polycrystalline silicon films and can suppress the polishing rate for at least one of silicon nitride films and silicon oxide films, resulting in a high polishing rate ratio for polycrystalline silicon films. On the other hand, the polishing compositions of the Comparative Examples do not provide a high polishing rate ratio for polycrystalline silicon films because the polishing rate for polycrystalline silicon films is low or the polishing rate for silicon nitride films and/or silicon oxide films is too high.

Therefore, it can be seen that the polishing composition of the present invention can polish polycrystalline silicon films at high speeds and suppress the polishing rate of at least one of silicon nitride films and silicon oxide films.

The above Table 1 shows the results obtained by separately polishing an object having a polycrystalline silicon film, an object having a silicon nitride film, and an object having a silicon oxide film. However, it is presumed that the same polishing speed and polishing selectivity of polycrystalline silicon as those in Table 1 above will be obtained even when polishing an object having polycrystalline silicon and at least one of silicon nitride and silicon oxide.

Claims (13)

A polishing composition comprising an abrasive grain and an amine oxide compound, the polishing composition having a pH of more than 5 and not more than 10,
the abrasive grains have a negative zeta potential in the polishing composition and an average degree of association of 3.0 or more and 6.0 or less;
The amine oxide compound is represented by the following formula (1):
In formula (1),
R ¹ to R ³ are each independently an alkyl group having 1 to less than 14 carbon atoms, and at least one of R ¹ to R ³ is an alkyl group having more than 8 and less than 14 carbon atoms;
Represented by
Polishing composition. The polishing composition according to claim 1, wherein the amine oxide compound has only one alkyl group having more than 8 and less than 14 carbon atoms. The polishing composition according to claim 1 or 2, wherein the amine oxide compound is at least one of decyl dimethylamine oxide and dodecyl dimethylamine oxide. The polishing composition according to claim 1 or 2, further comprising a compound having a nitrogen atom and a phosphonic acid group. The polishing composition according to claim 4, wherein the compound having a nitrogen atom and a phosphonic acid group is at least one selected from the group consisting of nitrilotrismethylenephosphonic acid or a salt thereof, alendronic acid or a salt thereof trihydrate, alendronic acid or a salt thereof, (1-aminoethyl)phosphonic acid or a salt thereof, N,N,N,N-ethylenediaminetetrakis(methylenephosphonic acid) or a salt thereof, and glycine N,N-bis(methylenephosphonic acid) or a salt thereof. The polishing composition according to claim 1 or 2, wherein the abrasive grains are anion-modified colloidal silica. The polishing composition according to claim 1 or 2, having a pH of 6 or more and less than 9. The polishing composition according to claim 1 or 2, further comprising one or more pH adjusters selected from nitric acid and ammonia. The polishing composition according to claim 1 or 2, which is used for polishing an object to be polished that contains polycrystalline silicon and at least one of silicon nitride and silicon oxide. Used to polish objects including polycrystalline silicon and silicon nitride,
10. The polishing composition according to claim 9, wherein the ratio of the polishing rate of the polycrystalline silicon to the polishing rate of the silicon nitride (polishing rate of the polycrystalline silicon/polishing rate of the silicon nitride) is 80 or more. It is used to polish objects containing polycrystalline silicon and silicon oxide.
10. The polishing composition according to claim 9, wherein a ratio of a polishing rate of the polycrystalline silicon to a polishing rate of the silicon oxide (polishing rate of the polycrystalline silicon/polishing rate of the silicon oxide) is 60 or more. A polishing method comprising a step of polishing an object containing polycrystalline silicon and at least one of silicon nitride and silicon oxide using the polishing composition according to claim 1. A method for manufacturing a semiconductor substrate, comprising a step of polishing a semiconductor substrate containing polycrystalline silicon and at least one of silicon nitride and silicon oxide by the polishing method according to claim 12.