Polishing composition, polishing method, and method for manufacturing semiconductor substrates

Abstract

To provide a polishing composition that enables high-speed polishing of a polycrystalline silicon film while reducing the polishing rate for at least one of a silicon nitride film and a silicon oxide film.SOLUTION: A polishing composition contains abrasive grains and an amine oxide compound, and has a pH greater than 5 and less than or equal to 10. The abrasive grains have a negative zeta potential in the polishing composition, and has an average degree of association from 3.0 to 6.0 inclusive. The amine oxide compound has a structure represented by formula (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a polishing composition, a polishing method, and a method for manufacturing a semiconductor substrate. [Background technology]

[0002] In recent years, with the increasing use of multilayer wiring on semiconductor substrate surfaces, chemical mechanical polishing (CMP) technology, which involves polishing and planarizing semiconductor substrates, has been utilized during device manufacturing.

[0003] This CMP (Chemical Polishing) technique has been applied to various processes in semiconductor manufacturing, one example being its application to the gate formation process in transistor fabrication. During transistor fabrication, materials such as metals, silicon, silicon oxide, polycrystalline silicon, and silicon nitride are sometimes polished, and there is a demand to polish each material at high speed in order to improve productivity. To meet such demands, for example, Patent Document 1 describes a technique for improving the polishing speed of polycrystalline silicon. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2013-041992 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] While investigating the application of CMP to various processes in semiconductor manufacturing, the inventors discovered that in some cases it is preferable from a manufacturing perspective to polish polycrystalline silicon films at high speed in the presence of silicon nitride or silicon oxide films. On the other hand, they also discovered that in some cases it is preferable from a manufacturing perspective to keep the polishing speed of silicon nitride or silicon oxide films as low as possible. However, there is currently no polishing composition that can polish polycrystalline silicon films at high speed while simultaneously suppressing the polishing speed of silicon nitride or silicon oxide films.

[0006] Therefore, the present invention aims to provide a polishing composition that can polish a polycrystalline silicon film at high speed and suppress the polishing speed of at least one of the silicon nitride film and the silicon oxide film. [Means for solving the problem]

[0007] To solve the above problems, the inventors have diligently conducted research. As a result, they have developed an abrasive composition comprising abrasive grains and an amine oxide compound, wherein the pH is greater than 5 and less than or equal to 10, the abrasive grains having a negative zeta potential in the abrasive composition and an average degree of association of 3.0 or more and less than or equal to 6.0, and the amine oxide compound is given by the following formula (1):

[0008] [ka]

[0009] In equation (1), R 1 ~R 3 Each of these is an alkyl group having 1 or more carbon atoms and less than 14 carbon atoms, where R 1 ~R 3 At least one of them is an alkyl group having more than 8 carbon atoms but less than 14 carbon atoms. We have found that the above problems can be solved by an abrasive composition represented by [the formula shown], and have completed the present invention. [Effects of the Invention]

[0010] According to the present invention, there is provided a polishing composition capable of polishing a polycrystalline silicon film at a high rate and suppressing the polishing rate of at least one of a silicon nitride film and a silicon oxide film. MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, modes for carrying out the present invention will be described in detail. The embodiments shown herein are examples for embodying the technical idea of the present invention, and do not limit the present invention. Therefore, all other implementable modes, usage methods, and operation techniques that can be conceived by those skilled in the art without departing from the gist of the present invention are all included in the scope and gist of the present invention, and also included in the scope of the invention described in the claims and the equivalent scope thereof. The embodiments described in the present specification can be arbitrarily combined to form other embodiments. In addition, in this specification, unless otherwise specified, measurements of operations, physical properties, and the like are performed under conditions of room temperature (20°C or more and 25°C or less) / relative humidity of 40%RH or more and 60%RH or less.

[0012] The present invention is a polishing composition comprising abrasive grains and an amine oxide compound, and having a pH of more than 5 and 10 or less, wherein the abrasive grains have a negative zeta potential in the polishing composition and have an average aggregation degree of 3.0 or more and 6.0 or less, and the amine oxide compound is represented by the following formula (1):

[0013]

Chemical Formula

[0014] In formula (1), R 1 to R 3 are each independently an alkyl group having 1 or more and less than 14 carbon atoms, wherein at least one of R 1 to R 3 is an alkyl group having more than 8 and less than 14 carbon atoms, This is an abrasive composition represented by [formula]. Such an abrasive composition can polish polycrystalline silicon films at high speed and suppress the polishing rate of at least one of the silicon nitride film and silicon oxide film. The inventors hypothesize the mechanism by which such effects are obtained by the present invention as follows. However, the following mechanism is merely a hypothesis and does not limit the scope of the present invention.

[0015] In the present invention, it is preferable that the object to be polished 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 high speed, while the polishing speed of at least one of the silicon nitride film and the silicon oxide film is suppressed. Abrasive grains having a negative zeta potential in a polishing composition with a pH greater than 5 and less than or equal to 10 are easily adsorbed onto the polycrystalline silicon film, silicon nitride film and silicon oxide film, thereby increasing the number of abrasive grains present on the surfaces of the polycrystalline silicon film, silicon nitride film and silicon oxide film during polishing. In this case, if the degree of association of the abrasive grains is high (for example, if the degree of association of the abrasive grains is 3.0 or more and 6.0 or less), the shape of the abrasive grains becomes rod-shaped and tends to remain on the surface of the object to be polished. This further improves the polishing speed of the polycrystalline silicon film, silicon nitride film and silicon oxide film. However, if the polishing speed of silicon nitride films and silicon oxide films 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 decrease. The inventors have found that the polishing composition of the present invention, when the pH is greater than 5 and less than or equal to 10, contains a specific amine oxide compound, thereby increasing the polishing speed of polycrystalline silicon films while suppressing or maintaining the polishing speeds of silicon nitride films and silicon oxide films. Hereinafter, the ratio of the polishing speed of polycrystalline silicon to the polishing speed of silicon nitride or silicon oxide will also be referred to as the "polishing selectivity ratio of polycrystalline silicon".

[0016] In other words, it is thought that certain amine oxide compounds are more likely to adsorb onto polycrystalline silicon films at a specific pH. When amine oxide compounds adsorb onto a polycrystalline silicon film, the lone pair of electrons on the nitrogen atom of the amine oxide compound interacts with the silicon-silicon bonds on the surface of the polycrystalline silicon film, causing the surface to become brittle. This makes it easier for abrasive particles on the surface of the polycrystalline silicon film to act on the film, and is thought to improve the polishing speed of the polycrystalline silicon film.

[0017] On the other hand, certain amine oxide compounds do not interact with silicon nitride and silicon oxide films as strongly as they do with polycrystalline silicon films, and their effect of embrittlement of the silicon nitride and silicon oxide film surfaces is weak. In other words, silicon nitride and silicon oxide films are chemically stable in the presence of the polishing composition of the present invention, and pH and the potential of the abrasive grains are dominant. As a result, it is speculated that improving the polishing speed of polycrystalline silicon films can improve the polishing selectivity of polycrystalline silicon. Thus, it is believed that the polishing composition of the present invention can polish polycrystalline silicon films at high speed while suppressing the polishing speed of silicon nitride and silicon oxide films.

[0018] As described above, the inventors have found that a polishing composition having a pH greater than 5 and less than or equal to 10, comprising abrasive grains having a negative zeta potential and a degree of association of 3.0 to 6.0, and a specific amine oxide compound, solves the problem of high-speed polishing of polycrystalline silicon films and suppression of polishing speed for silicon nitride films and silicon oxide films.

[0019] It should be noted that the above mechanism is based on speculation, and the present invention is not limited in any way to the above mechanism.

[0020] [Object to be polished] Preferably, the object to be polished according to the present invention includes a polycrystalline silicon (polysilicon) film, and at least one of a silicon nitride (Si₃N₄) film and a silicon oxide (SiO₂) 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.

[0021] According to one embodiment of the present invention, the application of the object to be polished is not limited, and examples thereof include semiconductor substrates, solar cell substrates, TFTs for liquid crystal displays (LCDs), and the like. The polishing composition is also suitable for test wafers, monitor wafers, transfer check wafers, dummy wafers, and the like of these substrates.

[0022] The object to be polished according to the present invention may contain other materials in addition to the polycrystalline silicon film, the silicon nitride film, and the silicon oxide film. Examples of other materials include silicon carbonitride (Si x C y N z ), doped polycrystalline silicon (doped polysilicon), undoped amorphous silicon, metals, SiGe, and the like.

[0023] Examples of the film containing silicon oxide include a TEOS (Tetraethyl Orthosilicate) type silicon oxide film produced using tetraethyl orthosilicate as a precursor (hereinafter also simply referred to as "TEOS film"), an HDP (High Density Plasma) film, a USG (Undoped Silicate Glass) film, a PSG (Phosphorus Silicate Glass) film, a BPSG (Boron-Phospho Silicate Glass) film, an RTO (Rapid Thermal Oxidation) film, and the like.

[0024] Examples of metal-containing films include tungsten (W) films, titanium nitride (TiN) films, ruthenium (Ru) films, platinum (Pt) films, silver (Ag) films, gold (Au) films, hafnium (Hf) films, cobalt (Co) films, palladium (Pd), iridium (Ir), osmium (Os), nickel (Ni) films, copper (Cu) films, aluminum (Al) films, and tantalum (Ta) films.

[0025] Furthermore, the shape of the object to be polished is not particularly limited. In one embodiment of the present invention, the polishing composition can be preferably applied to polishing objects having flat surfaces, such as plates or polyhedrons.

[0026] [Abrasive grains] 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 rate of the polycrystalline silicon film becomes low, or the polishing rate of the silicon nitride film or silicon oxide film becomes high, and as a result the polishing rate of the polycrystalline silicon film becomes lower than the polishing rate of the silicon nitride film or silicon oxide film (the polishing selectivity ratio of polycrystalline silicon becomes low). The abrasive grains are preferably anionic modified silica (silica having anionic groups), and more preferably anionic modified colloidal silica (colloidal silica having anionic groups). The abrasive grains may be used alone or in combination of two or more types. Furthermore, the abrasive grains may be commercially available or synthetic.

[0027] The polishing composition according to the present invention preferably contains anionically modified colloidal silica as abrasive particles. Anionically 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.

[0028] Preferred anionically modified colloidal silica includes colloidal silica in which anionic groups such as carboxyl groups, sulfonic acid groups, phosphonic acid groups, and aluminic acid groups are immobilized on the surface. The method for producing such colloidal silica having anionic groups is not particularly limited, and one example is a method of reacting colloidal silica with a silane coupling agent having anionic groups at its terminals.

[0029] For example, if you want to immobilize sulfonic acid groups on colloidal silica, you can do so by the method described in “Sulfonic acid-functionalized silica through of thiol groups”, Chem.Commun. 246-247 (2003). Specifically, by coupling a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, to colloidal silica and then oxidizing the thiol group with hydrogen peroxide, you can obtain colloidal silica on which sulfonic acid groups are immobilized on the surface (sulfonic acid-modified colloidal silica).

[0030] If the goal is to immobilize a carboxyl group on colloidal silica, this can be done, for example, by 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, by coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to colloidal silica and then irradiating it with light, colloidal silica with an immobilized carboxyl group on its surface (carboxylic acid-modified colloidal silica) can be obtained.

[0031] The lower limit of the zeta potential of the abrasive grains in the polishing composition is preferably -50mV or higher, more preferably -45mV or higher, even more preferably -40mV or higher, particularly preferably -35mV or higher, and most preferably -30mV or higher. The upper limit of the zeta potential of the abrasive grains in the polishing composition is preferably -1mV or lower, more preferably -5mV or lower, even more preferably -10mV or lower, particularly preferably -15mV or lower, and most preferably -20mV or lower. In other words, the zeta potential of the abrasive grains in the polishing composition is preferably -50mV or higher and -1mV or lower, more preferably -45mV or higher and -5mV or lower, even more preferably -40mV or higher and -10mV or lower, particularly preferably -35mV or higher and -15mV or lower, and most preferably -30mV or higher and -20mV or lower.

[0032] Abrasive grains with the zeta potential described above can polish polycrystalline silicon films at a higher polishing rate, resulting in a higher polishing rate for polycrystalline silicon films compared to silicon nitride films or silicon oxide films (a higher polishing selectivity for polycrystalline silicon).

[0033] The average primary particle diameter of the abrasive grains is preferably 1 nm or larger, more preferably 3 nm or larger, and even more preferably 5 nm or larger. As the average primary particle diameter of the abrasive grains increases, the polishing speed of the polycrystalline silicon film improves. Furthermore, the average primary particle diameter of the abrasive grains is preferably 100 nm or smaller, more preferably 50 nm or smaller, and even more preferably 30 nm or smaller. As the average primary particle diameter of the abrasive grains decreases, the polishing speed of the polycrystalline silicon film becomes higher than that of the silicon nitride film or silicon oxide film (the polishing selectivity ratio of polycrystalline silicon becomes higher).

[0034] In other words, the average primary particle diameter 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 diameter 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.

[0035] Furthermore, 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. Furthermore, 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 improves, and the polishing speed of the polycrystalline silicon film improves further. 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 by dynamic light scattering methods, such as laser diffraction scattering, and specifically, the values ​​measured by the method described in the examples are adopted.

[0036] 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 "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 workpiece, and the abrasive grains escape from between the polishing pad and the workpiece, resulting in inefficient polishing and a reduction in the polishing speed 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 workpiece, improving the polishing speed of the silicon nitride film or silicon oxide film, and lowering the polishing speed of the polycrystalline silicon film relative to the polishing speed of the silicon nitride film or silicon oxide film (polishing selectivity ratio 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 improves. Furthermore, 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 that of the silicon nitride film or silicon oxide film (the polishing selectivity of polycrystalline silicon increases). 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.

[0037] The average degree of aggregation of abrasive grains can be obtained by dividing the average secondary particle diameter of the abrasive grains by the average primary particle diameter.

[0038] The shape of the primary abrasive particles is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular or square prisms, cylindrical shapes, cylindrical shapes with a bulge in the center, donut shapes with a hole in the center, plate shapes, so-called cocoon shapes with a constriction in the center, so-called konpeito shapes with multiple protrusions on the surface, rugby ball shapes, and many other shapes, and are not particularly limited.

[0039] The shape of the secondary abrasive particles is not particularly limited. They may be peanut-shaped, with two primary abrasive particles arranged in parallel; bead-shaped, with three or more primary abrasive particles arranged in parallel; spherical, aggregate-like, three or more primary particles integrated into a single unit; or polygonal, aggregate-like, planar, three or more primary particles integrated into a single unit (e.g., triangle, square, rhombus, hexagon, etc.). Of these, the bead-like 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.

[0040] The size of the abrasive grains (average primary particle diameter, average secondary particle diameter, aspect ratio, primary particle shape, secondary particle shape, etc.) can be appropriately controlled by selecting the manufacturing method for the abrasive grains.

[0041] In this specification, the zeta potential of the abrasive grains is the value obtained by the method described in the examples. The zeta potential of the abrasive grains can be adjusted by the amount of anionic groups present in the abrasive grains, the pH of the polishing composition, etc.

[0042] In the polishing composition according to the present invention, abrasive grains may be used alone or in a mixture of two or more types. Furthermore, commercially available abrasive grains may be used, or synthetic abrasive grains may be used.

[0043] The abrasive content (concentration) 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 greater than 0.5% by mass, relative to the total mass of the polishing composition. Furthermore, the upper limit of the abrasive content (concentration) 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, relative to the total mass of the polishing composition. In other words, the abrasive content (concentration) 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 greater than 0.5% by mass and less than 4% by mass, relative to the total mass of the polishing composition. In one embodiment, the abrasive content (concentration) in the polishing composition is 0.01% by mass or more and 3.0% by mass or less.

[0044] If the abrasive content is within this range, the polishing rate of the polycrystalline silicon film will be higher than that of the silicon nitride film or silicon oxide film (the polishing selectivity of polycrystalline silicon will be higher). If the polishing composition contains two or more types of abrasives, the abrasive content refers to the total amount of these abrasives.

[0045] The polishing composition according to the present invention may further contain other abrasive particles other than anion-modified silica, provided that the abrasive particles have a negative zeta potential in the polishing composition, within a range that does not hinder the effects of the present invention. Such other abrasive particles may be inorganic particles, organic particles, or organic-inorganic composite particles. Specific examples of inorganic particles include, for example, 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, for example, polymethyl methacrylate (PMMA) particles.

[0046] [Amine oxide compounds] The polishing composition according to the present invention contains an amine oxide compound represented by the following formula (1).

[0047] [ka]

[0048] In equation (1), R 1 ~R 3 Each of these is an alkyl group having 1 or more carbon atoms and less than 14 carbon atoms, where R 1 ~R 3 At least one of these is an alkyl group having more than 8 carbon atoms but less than 14 carbon atoms. The alkyl group having 1 or more carbon atoms but less than 14 carbon atoms may be a linear alkyl group, a branched alkyl group, or a cyclic alkyl group, but a linear alkyl group having 1 or more carbon atoms but less than 14 carbon atoms is preferred.

[0049] Specific examples of alkyl groups having 1 or more carbon atoms but less than 14 carbon atoms include, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tet-butyl group, pentyl group, isopentyl group, neopentyl group, 2-ethylhexyl group, hexyl group, heptyl group, octyl group, 3,7-dimethyloctyl group, nonyl group, decyl group, undecyl group, dodecyl group (lauryl group), tridecyl group, and the like.

[0050] Here, in equation (1), R 1 ~R 3At least one of these alkyl groups is an alkyl group having more than 8 but less than 14 carbon atoms. That is, the amine oxide compound according to the present invention has at least one alkyl group having more than 8 but less than 14 carbon atoms among its three alkyl groups. Having at least one alkyl group having more than 8 but less than 14 carbon atoms in the amine oxide compound makes it easier to act on polycrystalline silicon films and improves the polishing speed of the polycrystalline silicon films. The alkyl groups other than the alkyl group having more than 8 but less than 14 carbon atoms may be alkyl groups having 1 to 8 carbon atoms. The amine oxide compound only needs to have at least one alkyl group having more than 8 but less than 14 carbon atoms, and may have two or three alkyl groups having more than 8 but less than 14 carbon atoms, but it is preferable to have only one alkyl group having more than 8 but less than 14 carbon atoms.

[0051] Examples of alkyl groups having more than 8 but less than 14 carbon atoms include nonyl groups, decyl groups, undecyl groups, dodecyl groups (lauryl groups), and tridecyl groups. More preferably, alkyl groups having 9 to 13 carbon atoms are alkyl groups having 10 to 12 carbon atoms, and particularly preferably alkyl groups having 10 or 12 carbon atoms.

[0052] In one embodiment, the amine oxide compound has only one alkyl group having more than 8 but less than 14 carbon atoms. Therefore, the amine oxide compound in this form has one alkyl group having more than 8 but less than 14 carbon atoms and two alkyl groups having 1 or more carbon atoms and 8 or less carbon atoms. That is, in one embodiment, in formula (1), R 1 and R 2 Each of these is an alkyl group having 1 to 8 carbon atoms, and R 3 This is an alkyl group having more than 8 carbon atoms but less than 14 carbon atoms.

[0053] In one embodiment, the amine oxide compound has three alkyl groups having more than 8 carbon atoms and less than 14 carbon atoms. That is, in one embodiment, in formula (1), R 1 ~R 3 Each of these is an alkyl group having more than 8 carbon atoms and less than 14 carbon atoms.

[0054] In one embodiment, the amine oxide compound has two alkyl groups having more than 8 carbon atoms but less than 14 carbon atoms, and one alkyl group having 1 carbon atom or more but 8 carbon atoms. That is, in one embodiment, in formula (1), R 1 and R 2 Each of these is an alkyl group having more than 8 carbon atoms and less than 14 carbon atoms, and R 3 This is an alkyl group having 1 to 8 carbon atoms.

[0055] In a preferred configuration, the amine oxide compound has one alkyl group having more than 8 but less than 14 carbon atoms, and two alkyl groups having 1 to 8 carbon atoms. This configuration of the amine oxide compound 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.

[0056] Specific examples of amine oxide compounds include decyldimethylamine oxide, methyl didecylamine oxide, decyldiethylamine oxide, ethyl didecylamine oxide, decyldipropylamine oxide, propyl didecylamine oxide, dodecyldimethylamine oxide, methyl didecylamine oxide, dodecyldiethylamine oxide, ethyl didecylamine oxide, dodecyldipropylamine oxide, propyl didecylamine oxide, tridecyldimethylamine oxide, methyl ditridecylamine oxide, tridecyldiethylamine oxide, ethyl ditridecylamine oxide, tri(tridecyl)amine oxide, and decyldi(tridecyl)amine oxide. Of these, decyldimethylamine oxide, methyl didecylamine oxide, decyldiethylamine oxide, ethyl didecylamine oxide, dodecyldimethylamine oxide, methyl didodecylamine oxide, dodecyldiethylamine oxide, and ethyl didodecylamine oxide are preferred as amine oxide compounds from the viewpoint of polishing selectivity for polycrystalline silicon films. It is even more preferable that the amine oxide compound is at least one of decyldimethylamine oxide and dodecyldimethylamine oxide.

[0057] 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. Furthermore, the amine oxide compound may be a commercially available product or a synthetic product.

[0058] 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. Furthermore, 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. In other words, 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, based on 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.

[0059] If the amine oxide compound content (concentration) is within this range, the polishing rate of polycrystalline silicon films will be higher than that of silicon nitride films or silicon oxide films (the polishing selectivity of polycrystalline silicon will be higher). If the polishing composition contains two or more amine oxide compounds, the amine oxide compound content (concentration) refers to the total amount of these compounds.

[0060] [Compounds containing a nitrogen atom and a 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 ratio of the polycrystalline silicon.

[0061] Compounds having a nitrogen atom and a phosphonic acid group include, for example, at least one selected from the group consisting of nitrilotrismethylenephosphonic acid or its salts, alendronic acid or its salt trihydrate, alendronic acid or its salts, (1-aminoethyl)phosphonic acid or its salts, N,N,N,N-ethylenediaminetetrakis(methylenephosphonic acid) or its salts, and glycine N,N-bis(methylenephosphonic acid) or its salts. Of these, nitrilotrismethylenephosphonic acid or its salts, N,N,N,N-ethylenediaminetetrakis(methylenephosphonic acid) or its salts are preferred.

[0062] 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 a mixture of two or more. Furthermore, the compound having a nitrogen atom and a phosphonic acid group may be a commercially available product or a synthetic product.

[0063] 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. Furthermore, 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. In other words, 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.

[0064] [pH and pH adjusters] The pH of the polishing composition according to the present invention is greater than 5 and less than or equal to 10. When the pH of the polishing composition is 5 or less, the adsorption of abrasive particles to the object to be polished in the polishing composition decreases, and the polishing speed of the polycrystalline silicon film decreases. When the pH of the polishing composition is greater than 10, the polishing speed of the silicon nitride film and silicon oxide film increases, and the polishing selectivity ratio of polycrystalline silicon decreases. The pH of the polishing composition is preferably 5.5 or higher, more preferably 5.8 or higher, even more preferably 6.0 or higher, particularly preferably 6.5 or higher, and most preferably 6.8 or higher. The pH of the polishing composition is preferably 9.8 or lower, more preferably 9.5 or lower, even more preferably 8.0 or lower, particularly preferably 7.8 or lower, and most preferably 7.5 or lower. In other words, the pH of the polishing composition is preferably 5.5 to 9.8, more preferably 5.8 to 9.5, even more preferably 6.0 to 8.0, particularly preferably 6.5 to 7.8, and most preferably 6.8 to 7.5. In one embodiment, the pH of the polishing composition is 6 to less than 9. When the pH of the polishing composition is within this range, the polishing rate of the polycrystalline silicon film becomes higher than that of the silicon nitride film or silicon oxide film (the polishing selectivity of polycrystalline silicon becomes higher).

[0065] The polishing composition of the present invention may contain a pH adjusting agent to adjust the pH to be greater than 5 and less than or equal to 10. Examples of pH adjusting agents include inorganic acids, organic acids, alkalis, etc. These may be used individually or in combination of two or more.

[0066] 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, or phosphoric acid are preferred, with nitric acid being more preferred. By using nitric acid as a pH adjuster, the polishing selectivity for polycrystalline silicon films can be improved, and the polishing rate for polycrystalline silicon films can be suitably increased.

[0067] Specific examples of organic acids that can be used as pH adjusters include, for example, 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-furanic acid, 2,5-franic acid, 3-furanic acid, 2-tetrahydrofuranic acid, methoxyacetic acid, methoxyphenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid, 10-camphorsulfonic acid, and isethionic acid.

[0068] Alkali metal salts of inorganic or organic acids may be used as pH adjusters, either in place of or in combination with inorganic or organic acids. In combinations of weak acids and strong bases, strong acids and weak bases, or weak acids and weak bases, a pH buffering effect can be expected.

[0069] Specific examples of alkalis that can be used as pH adjusters include, for example, 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 their salts. Examples of salts include carbonates, bicarbonates, sulfates, and acetates. 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 increased.

[0070] In one embodiment, the polishing composition according to the present invention further contains one or more pH adjusting agents selected from nitric acid and ammonia. This improves the polishing selectivity for polycrystalline silicon films and allows for a favorable improvement in the polishing speed for polycrystalline silicon films.

[0071] The content of the pH adjusting agent can be selected by appropriately adjusting it within the range that achieves the effects of the present invention. The pH of the polishing composition can be measured, for example, using a pH meter (e.g., a pH meter manufactured by Horiba, Ltd. (model number: LAQUA)).

[0072] [Dispersion medium] The polishing composition according to the present invention preferably contains a dispersion medium for dispersing each component. Examples of dispersion media include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone; and mixtures thereof. Of these, water is preferred as the dispersion medium. That is, according to a preferred embodiment of the present invention, the dispersion medium contains water. According to a more preferred embodiment of the present invention, the dispersion medium consists substantially of water. The term "substantially" above means that a dispersion medium other than water may be included insofar as the effects of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% to 100% by mass of water and 0% to 10% by mass of a dispersion medium other than water, and more preferably consists of 99% to 100% by mass of water and 0% to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0073] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, the dispersion medium should preferably be water that contains as few impurities as possible. Specifically, pure water, ultrapure water, or distilled water is more preferable, which is obtained by removing impurity ions with an ion exchange resin and then removing foreign matter by passing it through a filter.

[0074] [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 solubilizers, within a range that does not impair the effects of the present invention. The pH of the polishing composition according to the present invention is greater than 5 and less than or equal to 10. 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 abrasive grains, an amine oxide compound and a dispersion medium, and at least one selected from the group consisting of 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 abrasive grains, an amine oxide compound, a dispersion medium, and at least one selected from the group consisting of 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 exceeds 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 (total content = 100% by mass).

[0075] The antifungal agent (preservative) is not particularly limited and can be appropriately selected according to the desired use and purpose. Specifically, examples include isothiazoline preservatives such as 1,2-benzoisothiazole-3(2H)-one (BIT), 2-methyl-4-isothiazolin-3-one, and 5-chloro-2-methyl-4-isothiazolin-3-one, as well as phenoxyethanol.

[0076] [Polishing method and method for manufacturing semiconductor substrates] The polishing composition according to the present invention is suitably used for polishing objects comprising, for example, polycrystalline silicon and at least one of silicon nitride and silicon oxide. Therefore, the present invention provides a polishing method comprising polishing an object using the polishing composition according to the present invention. The present invention also provides a method for manufacturing a semiconductor substrate comprising polishing the semiconductor substrate using the polishing composition according to the present invention. Furthermore, the present invention provides a method for manufacturing a semiconductor substrate comprising polishing the semiconductor substrate by the polishing method according to the present invention.

[0077] As a polishing device, a general polishing device can be used that has a holder for holding a substrate or the like with the object to be polished, a motor with adjustable rotation speed, and a polishing platen to which a polishing pad (abrasive cloth) can be attached.

[0078] As the polishing pad, general nonwoven fabrics, polyurethanes, and porous fluororesins can be used without any particular restrictions. Preferably, the polishing pad has grooves that allow the polishing liquid to accumulate.

[0079] Regarding the polishing conditions, for example, the rotational speed of the polishing platen and carrier should be 10 rpm (0.17 s). -1 ) or more 500rpm (8.33s -1 ) is preferable. The pressure applied to the substrate having the object to be polished (polishing pressure) is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa).

[0080] The method of supplying the polishing composition to the polishing pad is not particularly limited; for example, a method of continuous supply using a pump or the like can be employed. There is no limit to the amount supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition according to the present invention.

[0081] After polishing is complete, the substrate is washed with running water, and any water droplets adhering to the substrate are removed using a spin dryer or the like to dry it, thereby obtaining a substrate having a layer containing metal.

[0082] The polishing composition according to the present invention may be a one-component type or a multi-component type, including a two-component type. Furthermore, the polishing composition according to the present invention may be prepared by diluting the stock solution of the polishing composition with a diluent such as water to, for example, three times or more (or, for example, five times or more).

[0083] [Polishing speed] When polishing with the polishing composition according to the present invention, the polishing speed 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 with the polishing composition according to the present invention, the polishing speed 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. There is no particular lower limit to the polishing speed of the silicon nitride film and / or silicon oxide film, but in practice it is 5 Å / min or more.

[0084] [Polishing selectivity ratio] When the polishing composition according to the present invention is used to polish an object containing 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. Furthermore, when the polishing composition according to the present invention is used to polish an object containing 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.

[0085] While embodiments of the present invention have been described in detail, these are descriptive and illustrative, and not limiting, and it is clear that the scope of the present invention should be interpreted by the appended claims.

[0086] The present invention encompasses the following embodiments and forms.

[0087] [1] An abrasive composition comprising abrasive grains and an amine oxide compound, wherein the pH is greater than 5 and less than or equal to 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 given by the following formula (1):

[0088] [ka]

[0089] In equation (1), R 1 ~R 3 Each of these is an alkyl group having 1 to 12 carbon atoms, where R 1 ~R 3 At least one of them is an alkyl group having more than 8 carbon atoms but less than 14 carbon atoms. An abrasive composition represented by [formula].

[0090] [2] The polishing composition according to [1] above, wherein the amine oxide compound has only one alkyl group having more than 8 carbon atoms and less than 14 carbon atoms.

[0091] [3] The polishing composition according to [1] or [2] above, wherein the amine oxide compound is at least one of decyldimethylamine oxide and dodecyldimethylamine oxide.

[0092] [4] The polishing composition according to any one of [1] to [3] above, further comprising a compound having a nitrogen atom and a phosphonic acid group.

[0093] [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 trihydrate of a salt thereof, 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.

[0094] [6] The polishing composition according to any one of [1] to [5] above, wherein the abrasive grains are anionically modified colloidal silica.

[0095] [7] An abrasive composition according to any of [1] to [6] above, wherein the pH is 6 or greater and less than 9.

[0096] [8] The polishing composition according to any one of [1] to [7] above, further comprising one or more pH adjusting agents selected from nitric acid and ammonia.

[0097] [9] A polishing composition according to any one of [1] to [8] above, which is used for polishing an object to be polished, comprising polycrystalline silicon and at least one of silicon nitride and silicon oxide.

[0098]

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

[0099]

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

[0100]

[12] A polishing method comprising the step of polishing an object to be polished, which includes polycrystalline silicon and at least one of silicon nitride and silicon oxide, using the polishing composition described in any of [1] to

[11] above.

[0101]

[13] A method for manufacturing a semiconductor substrate, comprising the 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. [Examples]

[0102] 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 "mass%" and "parts by mass," respectively.

[0103] <Average primary particle size of abrasive grains> The average primary particle size of the abrasive grains was calculated from the specific surface area of ​​silica particles measured by the BET method using a "Flow Sorb II 2300" manufactured by Micromerities, and the density of the abrasive grains.

[0104] <Average secondary particle size of abrasive grains> The average secondary particle diameter of the abrasive grains was measured as the volume-average particle diameter (volume-based arithmetic mean diameter; Mv) using a dynamic light scattering particle size and particle size distribution analyzer UPA-UTI151 (manufactured by Nikkiso Co., Ltd.).

[0105] <Average degree of aggregation of abrasive grains> The average degree of abrasive particle aggregation was calculated by dividing the average secondary particle diameter of the abrasive particles by the average primary particle diameter of the abrasive particles.

[0106] <Zeta potential of abrasive grains> The zeta potential of abrasive grains in the polishing composition was calculated by subjecting the polishing composition to a Malvern Panalytical Zetasizer Nano and measuring it using laser Doppler (electrophoretic light scattering measurement) at a measurement temperature of 25°C. The obtained data was then analyzed using the Smoluchowski equation.

[0107] <Shape of abrasive grains> The shape of the abrasive grains was analyzed by observing images of the abrasive grains using an HD-2700 scanning transmission electron microscope (manufactured by Hitachi High-Tech Corporation) according to the following procedure.

[0108] After dispersing abrasive particles in alcohol (abrasive particle concentration 0.01 mass%), the dried material was placed in a transmission electron microscope (TEM), irradiated with an electron beam at 5.0 kV, and several points of the observation field were captured at magnifications ranging from 50,000x to 200,000x.

[0109] The shape of the abrasive grains was confirmed in the captured TEM images based on the following criteria. (Standards for abrasive grain shape) If more than 50% of the TEM image shows the shape described below, the abrasive grain will be identified as having that shape. • Bead-like: Spherical abrasive grains arranged in a chain of three or more, with the grains at the ends not being connected to each other. • Peanut-shaped… Spherical abrasive particles arranged in pairs, connected together.

[0110] <pH of the abrasive composition> The pH of the polishing composition was determined using a glass electrode type hydrogen ion concentration indicator (Horiba, Ltd., Model: F-23). ​​After three-point calibration using standard buffers (phthalate pH buffer pH: 4.01 (25°C), neutral phosphate pH buffer pH: 6.86 (25°C), carbonate pH buffer pH: 10.01 (25°C)), the glass electrode was placed in the polishing composition, and the pH value after stabilization for at least two minutes was taken as the pH value.

[0111] <Electrical conductivity of abrasive compositions> The electrical conductivity (EC) of the polishing composition was measured using a benchtop electrical conductivity meter (manufactured by Horiba, Ltd., model number: DS-71 LAQUA®).

[0112] [Preparation of abrasive grains] [Preparation of abrasive grains 1-3] As anionically modified colloidal silica, anionically modified colloidal silica particles 1-3 were prepared using the method described in "Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups", Chem. Commun. 246-247 (2003).

[0113] • Abrasive grain 1: Average primary particle diameter: 22 nm, average secondary particle diameter: 80 nm, average degree of aggregation: 3.6 • Abrasive grain 2: Average primary particle diameter: 11 nm, average secondary particle diameter: 50 nm, average degree of aggregation: 4.5 • Abrasive grain 3: Average primary particle diameter: 35 nm, average secondary particle diameter: 70 nm, average degree of aggregation: 2.

[0114] [Preparation of abrasive grains 4] In the same manner as described in Example 1 of Japanese Patent Publication No. 2005-162533, cation-modified colloidal silica abrasive grains 4 were prepared by using γ-aminopropyltriethoxysilane (APTES) at a concentration of 0.113 mmol (0.113 mM) as a silane coupling agent in 1 L of an aqueous dispersion of silica sol (silica concentration = 20% by mass), with an average primary particle diameter of 22 nm, an average secondary particle diameter of 80 nm, and an average degree of association of 3.6.

[0115] [Preparation of abrasive compositions] (Example 1) The abrasive grains 1 (anionically modified colloidal silica) obtained above were added to pure water, the dispersion medium, 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 obtain a mixture to a final concentration of 0.014 mM.

[0116] Subsequently, decyldimethylamine oxide (manufactured by Lion Specialty Chemicals, Inc.) was added as an amine oxide compound to a final concentration of 0.05% by mass, and ammonia was added as a pH adjuster to a pH of 9. The mixture was stirred and mixed at room temperature (25°C) for 30 minutes to prepare polishing composition A1. The pH of the obtained polishing composition A1 was measured to be 9, and the electrical conductivity was 2 mS / cm.

[0117] The zeta potential of abrasive grain 1 (anionically modified colloidal silica) in the obtained polishing composition was measured according to the method described above and was found to be -35 mV. Furthermore, the particle size of abrasive grain 1 (anionically modified colloidal silica) in the polishing composition was similar to that of the abrasive grain 1 (anionically modified colloidal silica) used.

[0118] (Examples 2-5, Comparative Examples 1-8) Polishing compositions A2 to A5 for Examples 2 to 5 and polishing compositions B1 to B8 for Comparative Examples 1 to 8 were prepared in the same manner as in Example 1, except that the types and concentrations of each component and the pH were changed as shown in Table 1 below. Compounds having a nitrogen atom and a phosphonic acid group (indicated as "additives" in Table 1) were added before the addition of the pH adjuster, and the pH was adjusted with the pH adjuster after the addition. Nitrilotrismethylenephosphonic acid (product name: Kirest PH-320, manufactured by Kirest 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 obtained the values ​​shown in Table 1.

[0119] [evaluation] <Evaluation of polishing speed of polishing compositions> The surface of each object to be polished was polished using polishing compositions A1-A5 and B1-B8 under the following conditions. The following (1)-(3) were prepared as objects to be polished.

[0120] (1) Polycrystalline silicon film (poly-Si film): A silicon wafer on which a polycrystalline silicon film with a thickness of 5000 Å is formed on the surface. (2) Silicon nitride film (Si3N4 film): A silicon wafer (200 mm, blanket wafer) with a silicon nitride film with a thickness of 2000 Å formed on its surface. (3) Silicon oxide film (TEOS film): A silicon wafer (200 mm, blanket wafer) with a TEOS-type silicon oxide (SiO2) film with a thickness of 10,000 Å formed on its surface.

[0121] (Polishing equipment and polishing conditions) Polishing equipment: Applied Materials Mirra 200mm CMP single-sided polishing machine Polishing pad: Nitta Haas Co., Ltd. Hard polyurethane pad IC1010 Polishing pressure: 4.0 psi (1 psi = 6894.76 Pa) Polishing plate rotation speed: 47 rpm Head (carrier) rotation speed: 43 rpm Supply of polishing composition: flow-through Polishing composition supply amount: 200mL / min Polishing time: 60 seconds.

[0122] (Calculation of polishing speed) For each object to be polished, the thickness before and after polishing was determined using an optical film thickness measuring instrument (ASET-f5x: manufactured by KLA-Tencor Co., Ltd.).

[0123] For each object to be polished, the polishing rate 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 films, a polishing rate of 1500 Å / min or higher is practical, but 2000 Å / min or higher is preferable. For the polishing rate ratio between polycrystalline silicon films and silicon nitride films, a ratio of the polishing rate of polycrystalline silicon films to the polishing rate of silicon nitride films (poly-Si / Si3N4 in Table 1) of 50 or higher is practical. For the polishing rate ratio between polycrystalline silicon films and silicon oxide films, a ratio of the polishing rate of polycrystalline silicon films to the polishing rate of silicon oxide films (poly-Si / TEOS in Table 1) of 40 or higher is practical.

[0124] The evaluation results are shown in Table 1. In Table 1, polycrystalline silicon films are indicated as "poly-Si", silicon nitride films as "Si3N4", and TEOS films as "SiO2".

[0125] [Table 1]

[0126] As is clear from Table 1 above, the polishing composition of the example yields a high polishing rate for the polycrystalline silicon film and suppresses the polishing rate of at least one of the silicon nitride film and silicon oxide film, resulting in a high polishing rate ratio for the polycrystalline silicon film. On the other hand, the polishing composition of the comparative example does not yield a high polishing rate ratio for the polycrystalline silicon film due to reasons such as a low polishing rate for the polycrystalline silicon film or an excessively high polishing rate for the silicon nitride film and / or silicon oxide film.

[0127] Therefore, it can be seen that the polishing composition according to the present invention can polish polycrystalline silicon films at high speed and suppress the polishing speed of at least one of the silicon nitride film and silicon oxide film.

[0128] Table 1 above shows the results obtained by separately polishing objects having a polycrystalline silicon film, a silicon nitride film, and a silicon oxide film. However, it is presumed that even when polishing objects having polycrystalline silicon and at least one of silicon nitride and silicon oxide, similar polishing speeds and polishing selectivity ratios for polycrystalline silicon will be obtained as shown in Table 1.

Claims

1. An abrasive composition comprising abrasive particles and an amine oxide compound, wherein the pH is greater than 5 and less than or equal to 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 given by the following formula (1): 【Chemistry 1】 In equation (1), R １ ~R ３ Each of these is an alkyl group having 1 or more carbon atoms and less than 14 carbon atoms, where R １ ~R ３ At least one of them is an alkyl group having more than 8 carbon atoms but less than 14 carbon atoms. It is represented as, It is used for polishing objects containing polycrystalline silicon and at least one of silicon nitride and silicon oxide. When used for polishing objects containing polycrystalline silicon and silicon nitride, The ratio of the polishing rate of polycrystalline silicon to the polishing rate of silicon nitride (polishing rate of polycrystalline silicon / polishing rate of silicon nitride) is 80 or more; or, When used for polishing objects containing polycrystalline silicon and silicon dioxide, The ratio of the polishing rate of polycrystalline silicon to the polishing rate of silicon oxide (polishing rate of polycrystalline silicon / polishing rate of silicon oxide) is 60 or more; polishing composition.

2. An abrasive composition comprising abrasive grains and an amine oxide compound, wherein the pH is greater than 5 and less than or equal to 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 given by the following formula (1): 【Chemistry 2】 In equation (1), R1 to R3 are each independently alkyl groups having 1 or more carbon atoms and less than 14 carbon atoms, where at least one of R1 to R3 is an alkyl group having more than 8 carbon atoms and less than 14 carbon atoms. It is represented as, An abrasive composition further containing a compound having a nitrogen atom and a phosphonic acid group.

3. The polishing composition according to claim 1 or 2, wherein the amine oxide compound has only one alkyl group having more than 8 carbon atoms and less than 14 carbon atoms.

4. The polishing composition according to claim 1 or 2, wherein the amine oxide compound is at least one of decyldimethylamine oxide and dodecyldimethylamine oxide.

5. The polishing composition according to claim 1, further comprising a compound having a nitrogen atom and a phosphonic acid group.

6. The polishing composition according to claim 2 or 5, 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 trihydrate of a salt thereof, 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.

7. The polishing composition according to claim 1 or 2, wherein the abrasive grains are anionically modified colloidal silica.

8. The polishing composition according to claim 1 or 2, wherein the pH is 6 or higher and less than 9.

9. The polishing composition according to claim 1 or 2, further comprising one or more pH adjusting agents selected from nitric acid and ammonia.

10. The polishing composition according to claim 2, used for polishing an object to be polished, comprising polycrystalline silicon and at least one of silicon nitride and silicon oxide.

11. It is used for polishing objects containing polycrystalline silicon and silicon nitride. The polishing composition according to claim 10, wherein the ratio of the polishing rate of polycrystalline silicon to the polishing rate of silicon nitride (polishing rate of polycrystalline silicon / polishing rate of silicon nitride) is 80 or more.

12. It is used for polishing objects containing polycrystalline silicon and silicon dioxide. The polishing composition according to claim 10, wherein the ratio of the polishing rate of polycrystalline silicon to the polishing rate of silicon oxide (polishing rate of polycrystalline silicon / polishing rate of silicon oxide) is 60 or more.

13. A polishing method comprising the step of polishing an object to be polished, which includes polycrystalline silicon and at least one of silicon nitride and silicon oxide, using the polishing composition according to claim 1 or 2.

14. A method for manufacturing a semiconductor substrate, comprising the 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 claim 13.

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