Polishing composition, polishing method, method for manufacturing a semiconductor substrate, and agent for inhibiting the polishing rate of a polishing target having silicon-nitrogen bonds.

Abstract

To provide a means by which it is possible to polish a low-k material at a high polishing speed and also increase a ratio of a polishing speed of the low-k material to a polishing speed of silicon nitride.SOLUTION: A composition for polishing includes: abrasive grains; a trialkylamine oxide compound having at least one straight-chain or branched-chain alkyl group having a carbon number of 6-17; and a straight-chain polyphosphoric acid or its salt having a condensation degree of 3 or more. The composition for polishing has a pH of less than 7.0. Zeta-potential of the abrasive grains in the composition for polishing is negative.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polishing composition, a polishing method, a method for manufacturing a semiconductor substrate, and an inhibitor for suppressing the polishing rate of an object to be polished having a silicon-nitrogen bond.

Background Art

[0002] In recent years, with the high integration and high performance of LSI (Large Scale Integration), new microfabrication technologies have been developed. The chemical mechanical polishing (CMP) method is one of them and is a technology frequently used in the LSI manufacturing process, particularly in the planarization of interlayer insulating films, the formation of metal plugs, and the formation of embedded wiring (damascene wiring) in the multilayer wiring formation process.

[0003] As a material for interlayer insulating films in the multilayer wiring formation process, in order to suppress the wiring capacitance, low dielectric constant (Low-k) materials are being adopted. SiOC (silicon oxide containing carbon, obtained by doping C into SiO2) formed by the plasma CVD method is widely adopted as a low dielectric constant (Low-k) material.

[0004] As a technique for polishing SiOC, Patent Document 1 discloses a polishing composition containing abrasive grains containing cerium and hydroxyalkyl cellulose and having a pH of 6.0 or higher. According to Patent Document 1, by adopting such a configuration, it is said that the polishing rate of SiOC can be improved.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Recently, substrates containing both low-k materials, such as SiOC, and silicon nitride (Si3N4) have come into use. In such substrates, there is a growing demand to increase the polishing speed of the low-k material and to increase the ratio of the polishing speed of the low-k material to the polishing speed of silicon nitride (for example, polishing speed of low-k material / polishing speed of silicon nitride = 40 or more). However, the polishing composition described in Patent Document 1 has the problem of not being able to satisfy such requirements.

[0007] Therefore, the present invention aims to provide a means that enables polishing of low-k materials at a high polishing rate and increases the ratio of the polishing rate of the low-k material to the polishing rate of silicon nitride. [Means for solving the problem]

[0008] The inventors diligently studied to solve the above problems. As a result, they found that the above problems can be solved by an abrasive composition containing abrasive grains, a trialkylamine oxide compound having at least one linear or branched alkyl group with 6 to 17 carbon atoms, and a linear polyphosphate or a salt thereof with a degree of condensation of 3 or more, wherein the pH is less than 7.0, and the zeta potential of the abrasive grains in the abrasive composition is negative, and thus completed the present invention. [Effects of the Invention]

[0009] According to the present invention, a means may be provided that enables polishing of low-k materials at a high polishing rate and increases the ratio of the polishing rate of the low-k material to the polishing rate of silicon nitride. [Modes for carrying out the invention]

[0010] According to one embodiment of the present invention, there is a polishing composition comprising abrasive grains, a trialkylamine oxide compound having at least one linear or branched alkyl group having 6 to 17 carbon atoms, and a linear polyphosphate or salt thereof having a degree of condensation of 3 or more, wherein the pH is less than 7.0, and the zeta potential of the abrasive grains in the polishing composition is negative. With such a polishing composition of the present invention, low-k materials can be polished at a high polishing rate, and the ratio of the polishing rate of the low-k material to the polishing rate of silicon nitride (hereinafter also simply referred to as the "polishing rate selectivity ratio") can be increased.

[0011] The exact reason why the polishing composition of the present invention produces the above-mentioned effects is unknown, but it is thought to be due to the following mechanism. It should be noted that this mechanism is speculative, and the technical scope of the present invention is not limited by this mechanism.

[0012] Trialkylamine oxide compounds readily adsorb to low-k materials. When trialkylamine oxide compounds adsorb to the surface of a low-k material, the chemical bonds of the low-k material are distorted, making the low-k material more brittle. Furthermore, while the zeta potential of the surface of a low-k material is close to zero under acidic conditions, the zeta potential of the surface of a low-k material with adsorbed trialkylamine oxide turns positive. As a result, due to electrostatic attraction, abrasive grains with a negative zeta potential contained in the polishing composition are more easily attracted to the surface of the low-k material, increasing the polishing speed. The polishing speed of the low-k material is increased by these two effects: distortion of the bonds in the low-k material and the conversion of the zeta potential of the low-k material surface to positive.

[0013] Furthermore, the polishing composition according to the present invention has a pH of less than 7.0, and under these conditions, the zeta potential of the silicon nitride surface is positive. Due to electrostatic attraction, abrasive grains with a negative zeta potential contained in the polishing composition are more easily attracted to the silicon nitride surface with a positive zeta potential, and the polishing speed of silicon nitride tends to increase. However, linear polyphosphate or its salts with a condensation degree of 3 or more contained in the polishing composition according to the present invention adsorb to the silicon nitride surface and act as a protective film on the silicon nitride, thereby suppressing the polishing speed of silicon nitride. From the above, the polishing composition according to the present invention can increase the polishing speed of low-k materials and also increase the selectivity ratio of the polishing speed.

[0014] The embodiments of the present invention will be described in detail below, but the present invention is not limited to the embodiments described below and can be modified in various ways within the scope of the claims. The embodiments described herein can be combined in any way to form other embodiments. Unless otherwise specified herein, operations and measurements of physical properties, etc., are performed under conditions of room temperature (20°C to 25°C) and relative humidity of 40% RH to 50% RH.

[0015] [Abrasive grains] The polishing composition according to the present invention contains abrasive grains. These abrasive grains have the effect of mechanically polishing the object to be polished, thereby improving the polishing speed of the object to be polished by the polishing composition.

[0016] In the polishing composition of the present invention, the abrasive grains have a negative zeta potential. Here, "zeta (ζ) potential" refers to the potential difference that occurs at the interface between a solid and a liquid when they are in relative motion. When the zeta potential of the abrasive grains is 0mV or higher (0mV or positive), the polishing speed of the low-k material decreases, and the selectivity ratio of the polishing speed decreases.

[0017] In the polishing composition of the present invention, the zeta potential of the abrasive grains is preferably -50mV or more and less than 0mV, more preferably -40mV or more and -5mV or less, even more preferably -30mV or more and -7mV or less, and particularly preferably -20mV or more and -10mV or less. Having a zeta potential within this range of abrasive grains allows for a further improvement in the selectivity ratio of the polishing speed. Here, the zeta potential of the abrasive grains in the polishing composition is the value measured by the method described in the examples. The zeta potential of the abrasive grains can be controlled by appropriately selecting the pH of the polishing composition, the type and amount of trialkylamine oxide compound and polyphosphate or its salt added, the type of abrasive grain, the amount of anionic groups on the abrasive grain, etc.

[0018] The type of abrasive grain is not particularly limited, and examples include metal oxides such as silica, alumina, zirconia, and titania. The abrasive grain can be used alone or in combination of two or more types. The abrasive grains may be commercially available or synthetic.

[0019] The abrasive grains are preferably silica, and more preferably colloidal silica. Methods for producing colloidal silica include the sodium silicate method and the sol-gel method. Colloidal silica produced by either method is suitable for use as the abrasive grains of the present invention. However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method, which can be produced with high purity, is preferred.

[0020] Colloidal silica can be produced by the sol-gel method using conventionally known techniques. Specifically, colloidal silica can be obtained by using a hydrolyzable silicon compound (e.g., alkoxysilane or its derivatives) as a raw material and carrying out a hydrolysis-condensation reaction.

[0021] In some embodiments of the present invention, the colloidal silica contained in the polishing composition is preferably anionic modified colloidal silica, more preferably colloidal silica having an organic acid immobilized on its surface. Colloidal silica having an organic acid immobilized on its surface tends to have a larger absolute value of the zeta potential in the polishing composition compared to ordinary colloidal silica on which no organic acid is immobilized. Therefore, it is easy to adjust the zeta potential of the colloidal silica in the polishing composition to a negative value.

[0022] Examples of the colloidal silica having an organic acid immobilized on its surface preferably include colloidal silica having an anionic group such as a carboxylic acid group, a sulfonic acid group, a phosphonic acid group, or an aluminate group immobilized on its surface. Among these, colloidal silica having a sulfonic acid group or a carboxylic acid group immobilized on its surface is preferable from the viewpoint of easy production, and colloidal silica having a sulfonic acid group immobilized on its surface (sulfonic acid-modified colloidal silica) is more preferable. <C

[0023] The immobilization of the organic acid on the surface of the colloidal silica cannot be achieved simply by coexisting the colloidal silica and the organic acid. For example, if a sulfonic acid group is to be immobilized on the colloidal silica, it can be carried out, for example, by the method described in “Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups”, Chem. Commun. 246-247 (2003). Specifically, after coupling a silane coupling agent having a thiol group such as 3-mercaptopropyltrimethoxysilane to the colloidal silica, the thiol group is oxidized with hydrogen peroxide to obtain colloidal silica having a sulfonic acid group immobilized on its surface (sulfonic acid-modified colloidal silica).

[0024] Alternatively, if the carboxylic acid group is to be immobilized 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 a carboxylic acid group immobilized on its surface (carboxylic acid-modified colloidal silica) can be obtained.

[0025] The shape 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 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 aggregate spherical shapes where multiple particles are integrated, so-called konpeito shapes with multiple protrusions on the surface, rugby ball shapes, and many other shapes, and are not particularly limited.

[0026] The size of the abrasive grains is not particularly limited. For example, the average primary particle diameter of the abrasive grains is preferably 5 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, and particularly preferably 12 nm or more. As the average primary particle diameter of the abrasive grains increases, the polishing speed of the object to be polished by the polishing composition improves. Also, the average primary particle diameter of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 30 nm or less, and particularly preferably 20 nm or less. As the average primary particle diameter of the abrasive grains decreases, it becomes easier to obtain a surface with fewer defects by polishing with the polishing composition. That is, the average primary particle diameter of the abrasive grains is preferably 5 nm or more and 100 nm or less, more preferably 8 nm or more and 50 nm or less, even more preferably 10 nm or more and 30 nm or less, and particularly preferably 12 nm or more and 20 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 from the BET method, assuming that the shape of the abrasive grains is a perfect sphere.

[0027] Furthermore, the average secondary particle diameter of the abrasive grains is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, and particularly preferably 25 nm or more. As the average secondary particle diameter of the abrasive grains increases, the resistance during polishing decreases, and stable polishing becomes possible. Furthermore, the average secondary particle diameter of the abrasive grains is preferably 400 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, particularly preferably 100 nm or less, and most preferably 50 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 workpiece improves, and the polishing speed improves further. That is, the average secondary particle diameter of the abrasive grains is preferably 10 nm or more and 400 nm or less, more preferably 15 nm or more and 300 nm or less, even more preferably 20 nm or more and 200 nm or less, particularly preferably 25 nm or more and 100 nm or less, and particularly preferably 25 nm or more and 50 nm or less. The average secondary particle size of abrasive grains can be measured using dynamic light scattering methods, such as laser diffraction scattering.

[0028] The average degree of abrasive particle aggregation is preferably 5.0 or less, more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 2.5 or less. As the average degree of abrasive particle aggregation decreases, defects can be reduced more effectively. The average degree of abrasive particle aggregation is also preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. This average degree of aggregation is obtained by dividing the average secondary particle diameter of the abrasive particle by the average primary particle diameter. As the average degree of abrasive particle aggregation increases, there is the advantageous effect of improving the polishing speed of the object being polished by the polishing composition.

[0029] The upper limit of the aspect ratio of abrasive grains in the polishing composition is not particularly limited, but it is preferably less than 2.0, more preferably 1.8 or less, and even more preferably 1.5 or less. Within this range, defects on the surface of the object to be polished can be further reduced. The aspect ratio is the average of the values ​​obtained by taking the smallest rectangle that circumscribes the image of the abrasive grains using a scanning electron microscope and dividing the length of the longer side of that rectangle by the length of the shorter side of the same rectangle, and can be determined using general image analysis software. The lower limit of the aspect ratio of abrasive grains in the polishing composition is not particularly limited, but it is preferably 1.0 or more, and more preferably 1.2 or more.

[0030] In the particle size distribution determined by laser diffraction scattering of abrasive grains, the lower limit of D90 / D10, which is the ratio of the particle diameter (D90) when the cumulative particle mass from the fine particles reaches 90% of the total particle mass to the particle diameter (D10) when the cumulative particle mass from the fine particles reaches 10% of the total particle mass, is not particularly limited, but is preferably 1.1 or higher, more preferably 1.4 or higher, even more preferably 1.7 or higher, and most preferably 2.0 or higher. Furthermore, in the particle size distribution determined by laser diffraction scattering of abrasive grains in a polishing composition, the upper limit of the ratio D90 / D10, which is the ratio of the particle diameter (D90) when the cumulative particle mass from the fine particles reaches 90% of the total particle mass to the particle diameter (D10) when the cumulative particle mass from the fine particles reaches 10% of the total particle mass, is not particularly limited, but is preferably 3.0 or lower, and more preferably 2.5 or lower. Within this range, defects on the surface of the object to be polished can be further reduced.

[0031] The size of the abrasive grains (average primary particle diameter, average secondary particle diameter, aspect ratio, D90 / D10, etc.) can be appropriately controlled by selecting the manufacturing method for the abrasive grains.

[0032] The lower limit of the concentration (content) of abrasive grains in the polishing composition is not particularly limited, but it is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 0.7% by mass or more, relative to the total mass of the polishing composition. Similarly, the upper limit of the concentration (content) of abrasive grains in the polishing composition is not particularly limited, but it is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less, relative to the total mass of the polishing composition. In other words, the concentration (content) of abrasive grains in the polishing composition is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.3% by mass or more and 15% by mass or less, even more preferably 0.5% by mass or more and 10% by mass or less, and particularly preferably 0.7% by mass or more and 5% by mass or less, relative to the total mass of the polishing composition. Within this range, the polishing speed can be further improved while keeping costs down. Furthermore, if the abrasive composition contains two or more types of abrasive grains, the concentration (content) of the abrasive grains refers to the total amount of these grains.

[0033] [Trialkylamine oxide compounds] The polishing composition according to the present invention contains a trialkylamine oxide compound (hereinafter also simply referred to as "trialkylamine oxide compound") having at least one linear or branched alkyl group with 6 to 17 carbon atoms. As described above, the trialkylamine oxide compound has two effects: it distorts the chemical bonds of the low-k material, causing the low-k material to become brittle, and it converts the zeta potential of the low-k material surface to positive, thereby improving the polishing speed of the low-k material.

[0034] The trialkylamine oxide compound according to the present invention has at least one linear or branched alkyl group having 6 to 17 carbon atoms. As long as it has at least one such alkyl group, it may also have alkyl groups having less than 6 carbon atoms and / or alkyl groups having more than 17 carbon atoms.

[0035] In the case of trialkylamine oxide compounds that do not have linear or branched alkyl groups with 6 to 17 carbon atoms, the effect of distorting the chemical bonds of the Low-k material and / or the effect of converting the zeta potential of the Low-k material surface to positive is reduced, and the polishing rate of the Low-k material decreases.

[0036] Examples of linear or branched alkyl groups having 6 to 17 carbon atoms include, for example, n-hexyl group, 3-methylpentan-2-yl group, 3-methylpentan-3-yl group, 4-methylpentyl group, 4-methylpentan-2-yl group, 1,3-dimethylbutyl group, 3,3-dimethylbutyl group, 3,3-dimethylbutan-2-yl group, n-heptyl group, 1-methylhexyl group, 3-methylhexyl group, 4-methylhexyl group, 5-methylhexyl group, 1-ethylpentyl group, 1-(n-propyl)butyl group, 1,1-dimethylpentyl group, 1, 4-dimethylpentyl group, 1,1-diethylpropyl group, 1,3,3-trimethylbutyl group, 1-ethyl-2,2-dimethylpropyl group, n-octyl group, 2-ethylhexyl group, 2-methylhexane-2-yl group, 2,4-dimethylpentan-3-yl group, 1,1-dimethylpentan-1-yl group, 2,2-dimethylhexane-3-yl group, 2,3-dimethylhexane-2-yl group, 2,5-dimethylhexane-2-yl group, 2,5-dimethylhexane-3-yl group, 3,4-dimethylhexane-3-yl group, 3,5-dimethylhexane- 3-yl group, 1-methylheptyl group, 2-methylheptyl group, 5-methylheptyl group, 2-methylheptan-2-yl group, 3-methylheptan-3-yl group, 4-methylheptan-3-yl group, 4-methylheptan-4-yl group, 1-ethylhexyl group, 2-ethylhexyl group, 1-propylpentyl group, 2-propylpentyl group, 1,1-dimethylhexyl group, 1,4-dimethylhexyl group, 1,5-dimethylhexyl group, 1-ethyl-1-methylpentyl group, 1-ethyl-4-methylpentyl group, 1,1,4-trimethylpentyl group, 2 ,4,4-trimethylpentyl group, 1-isopropyl-1,2-dimethylpropyl group, 1,1,3,3-tetramethylbutyl group, n-nonyl group, 1-methyloctyl group, 6-methyloctyl group, 1-ethylheptyl group, 1-(n-butyl)pentyl group, 4-methyl-1-(n-propyl)pentyl group, 1,5,5-trimethylhexyl group, 1,1,5-trimethylhexyl group, 2-methyloctan-3-yl group, n-decyl group, 1-methylnonyl group, 1-ethyloctyl group, 1-(n-butyl)hexyl group, 1,1-dimethyloctyl group, 3,Examples include 7-dimethyloctyl group, n-undecyl group, 1-methyldecyl group, 1-ethylnonyl group, n-dodecyl group, 1-methylundecyl group, n-tridecyl group, n-tetradecyl group, 1-methyltridecyl group, n-pentadecyl group, 1-methyltetradecyl group, n-hexadecyl group, 1-methylpentadecyl group, n-heptadecyl group, and 1-methylhexadecyl group. When there are two or more linear or branched alkyl groups with 6 to 17 carbon atoms, these alkyl groups may be the same or different.

[0037] More specific examples of trialkylamine oxide compounds include octyldimethylamine oxide, nonyldimethylamine oxide, decyldimethylamine oxide, undecyldimethylamine oxide, dodecyldimethylamine oxide, isododecyldimethylamine oxide, tridecyldimethylamine oxide, tetradecyldimethylamine oxide, pentadecyldimethylamine oxide, hexadecyldimethylamine oxide, heptadecyldimethylamine oxide, decyldiethylamine oxide, dodecyldiethylamine oxide, and tridecyldiethylamine oxide. Examples include decyldipropylamine oxide, dodecyldipropylamine oxide, tetradecyldipropylamine oxide, hexadecyldipropylamine oxide, tetradecyldibutylamine oxide, methyl didecylamine oxide, ethyl didecylamine oxide, propyl didecylamine oxide, methyl didecylamine oxide, ethyl didecylamine oxide, propyl didecylamine oxide, methyl ditridecylamine oxide, ethyl ditridecylamine oxide, tri(tridecyl)amine oxide, and decyldi(tridecyl)amine oxide. These trialkylamine oxide compounds may be used individually or in combination of two or more. Furthermore, commercially available or synthetic trialkylamine oxide compounds may be used.

[0038] From the viewpoint of further improving the effects of the present invention, it is preferable that the trialkylamine oxide compound has only one linear or branched alkyl group having 6 to 17 carbon atoms. Furthermore, it is more preferable that the number of carbon atoms in the linear or branched alkyl group of the trialkylamine oxide compound is 8 to 14. When using a trialkylamine compound having two or more linear or branched alkyl groups having 6 to 17 carbon atoms, or when using a trialkylamine compound having an alkyl group having 15 to 17 carbon atoms, abrasive grain aggregation tends to occur more easily.

[0039] Based on the above, the alkylamine compound according to the present invention is more preferably at least one monoalkylamine compound selected from the group consisting of octyldimethylamine oxide, nonyldimethylamine oxide, decyldimethylamine oxide, undecyldimethylamine oxide, dodecyldimethylamine oxide, isododecyldimethylamine oxide, tridecyldimethylamine oxide, and tetradecyldimethylamine oxide. The alkylamine compound according to the present invention is even more preferably at least one of decyldimethylamine oxide and dodecyldimethylamine oxide.

[0040] The lower limit of the concentration (content) of the trialkylamine oxide compound in the polishing composition is not particularly limited, but it is preferably 10 ppm by mass or more, more preferably 50 ppm by mass or more, even more preferably 70 ppm by mass or more, and particularly preferably 100 ppm by mass or more, relative to the total mass of the polishing composition. Furthermore, the upper limit of the concentration (content) of the trialkylamine oxide compound relative to the total mass of the polishing composition is not particularly limited, but it is preferably 2000 ppm by mass or less, more preferably 1000 ppm by mass or less, even more preferably 800 ppm by mass or less, and particularly preferably 500 ppm by mass or less, relative to the total mass of the polishing composition. In other words, the concentration (content) of the trialkylamine oxide compound in the polishing composition is preferably 10 ppm by mass or more and 2000 ppm by mass or less, more preferably 50 ppm by mass or more and 1000 ppm by mass or less, even more preferably 70 ppm by mass or more and 800 ppm by mass or less, and particularly preferably 100 ppm by mass or more and 500 ppm by mass or less, relative to the total mass of the polishing composition.

[0041] Furthermore, if the polishing composition contains two or more trialkylamine oxide compounds, the concentration (content) of the trialkylamine oxide compounds refers to their total amount.

[0042] [Polyphosphate or its salts] The polishing composition according to the present invention contains a linear polyphosphate or a salt thereof having a degree of condensation of 3 or more (hereinafter also simply referred to as "polyphosphate compound"). As described above, the polyphosphate compound has the effect of suppressing the polishing rate of silicon nitride.

[0043] The degree of condensation of the polyphosphate compound is 3 or higher. If the degree of condensation is less than 3, the effect of suppressing the polishing rate of silicon nitride becomes insufficient, and the selectivity ratio of the polishing rate decreases. The degree of condensation is preferably 4 or higher. There is no particular upper limit to the degree of condensation, but it is preferably 50 or less.

[0044] Furthermore, the polyphosphate compounds according to the present invention are linear in shape. In the case of cyclic polyphosphate compounds, the polishing rate of low-k materials is also suppressed, and the selectivity ratio of polishing rates decreases.

[0045] Examples of polyphosphate compounds include tripolyphosphate, tetrapolyphosphate, pentapolyphosphate, hexapolyphosphate, heptapolyphosphate, octapolyphosphate, nonapolyphosphate, and decapolyphosphate. Sodium salts, potassium salts, and ammonium salts of these polyphosphates can also be suitably used.

[0046] Polyphosphate compounds can be used individually or in combination of two or more. Furthermore, commercially available or synthetic polyphosphate compounds may be used.

[0047] It is preferable to use a mixture of polyphosphate compounds with different degrees of condensation as the polyphosphate compound according to the present invention. More preferably, it is a mixture of tetrapolyphosphate, pentapolyphosphate, hexapolyphosphate, heptapolyphosphate, octapolyphosphate, and nonapolyphosphate (hereinafter also referred to as "a mixture of polyphosphates with a degree of condensation of 4 to 9"). It is even more preferable that the mixture is a mixture of sodium tetrapolyphosphate, sodium pentapolyphosphate, sodium hexapolyphosphate, sodium heptapolyphosphate, sodium octapolyphosphate, and sodium nonapolyphosphate (hereinafter also referred to as "a mixture of sodium polyphosphates with a degree of condensation of 4 to 9").

[0048] The lower limit of the concentration (content) of the polyphosphate compound in the polishing composition is not particularly limited, but it is preferably 10 ppm by mass or more, more preferably 50 ppm by mass or more, even more preferably 150 ppm by mass or more, even more preferably 250 ppm by mass or more, particularly preferably 350 ppm by mass or more, and most preferably 450 ppm by mass or more, based on the total mass of the polishing composition. The upper limit of the concentration (content) of the polyphosphate compound in the polishing composition is not particularly limited, but it is preferably 2000 ppm by mass or less, more preferably 1500 ppm by mass or less, even more preferably 1200 ppm by mass or less, even more preferably 800 ppm by mass or less, and particularly preferably 700 ppm by mass or less, based on the total mass of the polishing composition. In other words, the concentration (content) of the polyphosphate compound in the polishing composition is preferably 10 ppm to 2000 ppm by mass, more preferably 50 ppm to 1500 ppm by mass, even more preferably 150 ppm to 1200 ppm by mass, even more preferably 250 ppm to 800 ppm by mass, particularly preferably 350 ppm to 700 ppm by mass, and most preferably 450 ppm to 700 ppm by mass, based on the total mass of the polishing composition.

[0049] Furthermore, if the abrasive composition contains two or more polyphosphate compounds, the concentration (content) of the polyphosphate compounds refers to their total amount.

[0050] <Ratio of concentration (content)> In the polishing composition according to the present invention, the ratio of the concentration (content) of the polyphosphate compound to the concentration (content) of the trialkylamine oxide compound (concentration of polyphosphate compound / concentration of trialkylamine oxide compound) is preferably 1.0 or higher, more preferably 1.5 or higher, even more preferably 2.0 or higher, and particularly preferably 2.5 or higher. Furthermore, the ratio of the concentration (content) of the polyphosphate compound to the concentration (content) of the trialkylamine oxide compound (concentration of polyphosphate compound / concentration of trialkylamine oxide compound) is preferably 100 or less, more preferably 50 or less, even more preferably 20 or less, particularly preferably 10 or less, and most preferably 5.0 or less. In other words, the ratio of the concentration (content) of the polyphosphate compound to the concentration (content) of the trialkylamine oxide compound (concentration of polyphosphate compound / concentration of trialkylamine oxide compound) is particularly preferably 2.5 or higher. Furthermore, the ratio of the concentration (content) of the polyphosphate compound to the concentration (content) of the trialkylamine oxide compound (concentration of polyphosphate compound / concentration of trialkylamine oxide compound) is preferably 1.0 to 100, more preferably 1.5 to 50, even more preferably 2.0 to 20, particularly preferably 2.5 to 10, and most preferably 2.5 to 5.0. Within this range of concentration ratios, the selectivity ratio of polishing speed is further improved. By appropriately selecting this ratio of the concentration (content) of the polyphosphate compound to the concentration (content) of the trialkylamine oxide compound (concentration of polyphosphate compound / concentration of trialkylamine oxide compound), it is possible to obtain the desired selectivity ratio of polishing speed.

[0051] [pH and pH adjusters] The pH of the polishing composition according to the present invention is less than 7.0. If the pH is 7.0 or higher, the polishing speed of the low-k material decreases, and the selectivity ratio of the polishing speed decreases. The pH is preferably 1.0 or higher, more preferably 1.5 or higher, and even more preferably 2.0 or higher. Furthermore, the pH is preferably 6.5 or lower, more preferably 6.0 or lower, and even more preferably 5.0 or lower. In other words, the pH of the polishing composition according to the present invention is preferably 1.0 or higher and 6.5 or lower, more preferably 1.5 or higher and 6.0 or lower, and even more preferably 2.0 or higher and 5.0 or lower.

[0052] The polishing composition according to the present invention preferably contains a pH adjusting agent for adjusting the pH. The pH adjusting agent may be either an acid or a base, and may be either an inorganic compound or an organic compound. The pH adjusting agent can be used alone or as a mixture of two or more.

[0053] Specific examples of acids that can be used as pH adjusters include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid; and organic acids such as 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, and phenoxyacetic acid.

[0054] Examples of bases that can be used as pH adjusters include amines such as aliphatic amines and aromatic amines, organic bases such as quaternary ammonium hydroxides, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, hydroxides of group 2 elements, and ammonia.

[0055] The amount of pH adjuster added is not particularly limited and can be adjusted as appropriate so that the polishing composition reaches the desired pH. The pH of the polishing composition can be measured, for example, by a pH meter, and specifically by the method described in the examples.

[0056] [Dispersion medium] The polishing composition according to the present invention preferably further contains a dispersion medium. Examples of dispersion mediums include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone, and mixtures thereof. Of these, water is preferred as the dispersion medium. That is, according to a more preferred embodiment of the present invention, the dispersion medium contains water. According to an even 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 objective effects of the present invention can be achieved. More specifically, it 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.

[0057] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, water containing as few impurities as possible is preferred as the dispersion medium. More specifically, pure water, ultrapure water, or distilled water obtained by removing impurity ions with an ion exchange resin and then removing foreign matter by passing it through a filter is more preferred.

[0058] [Electrical conductivity of abrasive compositions] The electrical conductivity (EC) of the polishing composition according to the present invention is not particularly limited, but is preferably 1 mS / cm or more, and more preferably 1.5 mS / cm or more. Furthermore, the electrical conductivity (EC) of the polishing composition according to the present invention is preferably 20 mS / cm or less, and more preferably 15 mS / cm or less. That is, the electrical conductivity (EC) of the polishing composition according to the present invention is preferably 1 mS / cm or more and 20 mS / cm or less, and more preferably 1.5 mS / cm or more and 15 mS / cm or less. If the electrical conductivity (EC) of the polishing composition is within this range, the polishing speed of low-k materials can be maintained at a high level, and the repulsion between abrasive grains can be appropriately adjusted to ensure stability. The electrical conductivity of the polishing composition can be adjusted by the type and amount of pH adjusters, etc., and the electrical conductivity can be measured by the method described in the examples.

[0059] [Other ingredients] The polishing composition of the present invention may further contain, if necessary, known additives that can be used in polishing compositions, such as water-soluble polymers, complexing agents, metal corrosion inhibitors, preservatives, fungicides, oxidizing agents, reducing agents, and surfactants. Among these, it is preferable that the polishing composition contains a fungicide. The polishing composition according to the present invention is acidic. 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, a trialkylamine oxide compound having at least one linear or branched alkyl group having 6 to 17 carbon atoms, a linear polyphosphate or a salt thereof with a degree of condensation of 3 or more, a dispersion medium, and at least one of a pH adjuster and a fungicide. Here, "the polishing composition is substantially composed of abrasive grains, a trialkylamine oxide compound having at least one linear or branched alkyl group having 6 to 17 carbon atoms, a linear polyphosphate or salt thereof with a degree of condensation of 3 or more, a dispersion medium, and at least one of a pH adjuster and an antifungal agent" means that the total content of abrasive grains, a trialkylamine oxide compound having at least one linear or branched alkyl group having 6 to 17 carbon atoms, a linear polyphosphate or salt thereof with a degree of condensation of 3 or more, a dispersion medium, and at least one of a pH adjuster and an antifungal agent exceeds 99% by mass (upper limit: 100% by mass) of the total mass of the polishing composition. Preferably, the polishing composition is composed of abrasive grains, a trialkylamine oxide compound having at least one linear or branched alkyl group having 6 to 17 carbon atoms, a linear polyphosphate or salt thereof with a degree of condensation of 3 or more, a dispersion medium, a pH adjuster, and an antifungal agent (total content = 100% by mass).

[0060] Below, we will discuss other desirable ingredients, such as fungicides (preservatives). We will also discuss oxidizing agents.

[0061] (Anti-mold agent) Examples of antifungal agents (preservatives) that can be added to the polishing composition according to the present invention include isothiazoline-based preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, parahydroxybenzoic acid esters, and phenoxyethanol. These antifungal agents (preservatives) may be used individually or in combination of two or more.

[0062] (Oxidizing agent) The polishing composition according to the present invention may contain an oxidizing agent. Examples of oxidizing agents include, but are not limited to, peroxides, nitrates, periodic acid or its salts, peroxoacid or its salts, permanganic acid or its salts, chromic acid or its salts, oxygen acids or their salts, metal salts, sulfuric acids, etc. The oxidizing agent can be used alone or in combination of two or more. Specific examples of oxidizing agents include hydrogen peroxide, sodium peroxide, barium peroxide, iron nitrate, aluminum nitrate, ammonium nitrate, peroxomonosulfate, ammonium peroxomonosulfate, metal peroxomonosulfate, peroxodisulfate, ammonium peroxodisulfate, metal peroxodisulfate, peroxolinic acid, peroxosulfate, sodium peroxoborate, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromous acid, hypoiodic acid, chloric acid, bromic acid, iodic acid, periodic acid, perchloric acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, potassium permanganate, metal chromate, metal dichromate, iron chloride, iron sulfate, iron citrate, iron ammonium sulfate, etc. Preferred oxidizing agents include hydrogen peroxide, iron nitrate, periodic acid, peroxomonosulfate, peroxodisulfate, and nitric acid. The concentration (content) of the oxidizing agent relative to the total mass of the polishing composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more. Furthermore, the upper limit of the concentration (content) of the oxidizing agent is preferably 5% by mass or less, and more preferably 3% by mass or less.

[0063] [Form of abrasive composition] The polishing composition according to the present invention is typically supplied to an object to be polished in the form of a polishing liquid containing the polishing composition and used to polish the object. The polishing composition according to the present invention may be used as a polishing liquid after being diluted (typically diluted with water), or it may be used as a polishing liquid as is. That is, the concept of the polishing composition according to the present invention encompasses both a polishing composition (working slurry) supplied to an object to be polished and used to polish the object, and a concentrated liquid (working slurry stock) that is diluted and used for polishing. The concentration ratio of the concentrated liquid can be, for example, about 2 to 100 times by volume, and usually about 3 to 50 times is appropriate.

[0064] [Object to be polished] The material to be polished according to the present invention is not particularly limited and includes, for example, single-crystal silicon, polycrystalline silicon (polysilicon), polycrystalline silicon doped with n-type or p-type impurities, amorphous silicon, amorphous silicon doped with n-type or p-type impurities, silicon oxide, materials having silicon-nitrogen bonds, metals, SiGe, carbon-containing materials, low-dielectric constant materials (low-k materials), and the like.

[0065] Examples of polishing targets containing silicon dioxide include, for example, TEOS-type silicon dioxide films (hereinafter also simply referred to as "TEOS" or "TEOS film") produced using tetraethyl orthosilicate as a precursor, HDP (High Density Plasma) films, USG (Undoped Silicate Glass) films, PSG (Phosphorus Silicate Glass) films, BPSG (Boron-Phospho Silicate Glass) films, and RTO (Rapid Thermal Oxidation) films.

[0066] Examples of materials containing silicon-nitrogen bonds include silicon nitride (Si3N4) and silicon carbonitride (Si3N4). x C y N z Examples include:

[0067] Examples of metals include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0068] Examples of carbon-containing materials include materials other than low-k materials such as amorphous carbon, spin-on carbon (SOC), diamond-like carbon (DLC), nanocrystalline diamond, and graphene.

[0069] Low-k materials are materials with a relative permittivity k lower than that of silicon oxide, preferably materials with a relative permittivity k of 3.0 or less. Specifically, examples include silicon carbide (SiC), carbon-containing silicon oxide (SiOC), silicon oxide containing methyl groups, benzocyclobutene (BCB), fluorinated silicon oxide (SiOF), HSQ (hydrogensilsesquioxane), MSQ (methylsilsesquioxane), HMSQ (hydride-methylsilsesquioxane), polyimide polymers, arylene ether polymers, cyclobutene polymers, perfluorocyclobutene (PFCB), and the like.

[0070] The object to be polished may be a commercially available product or may be manufactured by a known method.

[0071] Among these, polishing objects containing a low-k material and silicon nitride are preferred. Therefore, according to a preferred embodiment of the present invention, the polishing composition is used for polishing polishing objects containing a low-k material and silicon nitride. The low-k material is preferably carbon-containing silicon oxide (SiOC).

[0072] [Method for producing abrasive compositions] The method for producing the polishing composition according to this embodiment is not particularly limited and can be obtained, for example, by stirring and mixing abrasive grains, a trialkylamine oxide compound, a polyphosphate compound, a dispersion medium, and other additives added as needed. Details of each component are as described above.

[0073] The temperature at which each component is mixed is not particularly limited, but it is preferably between 10°C and 40°C, and heating may be used to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is achieved.

[0074] [Polishing method and method for manufacturing semiconductor substrates] As described above, the polishing composition according to this embodiment is particularly suitable for polishing objects having a low-k material and silicon nitride. Therefore, the present invention provides a polishing method comprising the step of polishing an object having a low-k material and silicon nitride with the polishing composition according to this embodiment. The present invention also provides a method for manufacturing a semiconductor substrate, comprising polishing a semiconductor substrate having a low-k material and silicon nitride by the above polishing method.

[0075] 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.

[0076] 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.

[0077] Regarding the polishing conditions, for example, the rotational speed of the polishing platen and carrier (head) should be 10 rpm (0.17 s). -1 ) or more 500rpm (8.33s -1 Preferably, the pressure applied to the substrate containing the object to be polished (polishing pressure) is between 0.5 psi (3.45 kPa) and 10 psi (68.9 kPa).

[0078] 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.

[0079] The polishing composition according to this embodiment 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, for example, three times or more.

[0080] [Polishing speed inhibitor] As described above, the polyphosphate compound according to the present invention has the effect of suppressing the polishing rate of silicon nitride. Therefore, the present invention provides a polishing rate inhibitor for a material to be polished that has silicon-nitrogen bonds, comprising a linear polyphosphate or a salt thereof having a condensation degree of 3 or more.

[0081] [Polishing speed] As described above, the polishing composition according to the present invention can increase the polishing speed of low-k materials and increase the ratio of the polishing speed of low-k materials to the polishing speed of silicon nitride (the selectivity ratio of the polishing speed).

[0082] In the present invention, the polishing speed of the Low-k material is preferably 600 Å / min or more, more preferably 800 Å / min or more, and even more preferably 1000 Å / min or more. The polishing speed of silicon nitride is preferably 30 Å / min or less, more preferably 20 Å / min or less, and even more preferably 15 Å / min or less. There is no particular lower limit to the polishing speed of silicon nitride, but in practice it is 5 Å / min or more.

[0083] [Selective ratio of polishing speed] In the present invention, the ratio of the polishing rate of the Low-k material to the polishing rate of silicon nitride (polishing rate selectivity ratio, polishing rate of Low-k material / polishing rate of silicon nitride) is preferably 40 or more, more preferably 60 or more, even more preferably 65 or more, even more preferably 70 or more, and particularly preferably 75 or more.

[0084] 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.

[0085] The present invention encompasses the following embodiments and forms. 1. An abrasive composition comprising abrasive grains, a trialkylamine oxide compound having at least one linear or branched alkyl group with 6 to 17 carbon atoms, and a linear polyphosphate or salt thereof having a degree of condensation of 3 or more, wherein the pH is less than 7.0, and the zeta potential of the abrasive grains in the abrasive composition is negative; 2. The polishing composition described in 1. above, wherein the trialkylamine oxide compound has only one linear or branched alkyl group having 6 to 17 carbon atoms; 3. The polishing composition according to 1. or 2. above, wherein the number of carbon atoms in the alkyl group is 8 or more and 14 or less; 4. The polishing composition according to any one of 1. to 3. above, wherein the trialkylamine oxide compound is at least one of decyldimethylamine oxide and dodecyldimethylamine oxide; 5. The polishing composition according to any one of 1. to 4. above, wherein the concentration of the polyphosphate or its salt relative to the total mass of the polishing composition is 10 ppm by mass or more and 2000 ppm by mass or less; 6. The abrasive grain is anionically modified colloidal silica, as described in any of items 1 to 5 above; 7. A polishing composition according to any one of items 1 to 6 above, further comprising a pH adjusting agent; 8. The polishing composition according to any one of items 1 to 7 above, further comprising a dispersion medium; 9. Polishing compositions according to any of items 1 to 8 above, used for polishing objects containing low-k materials and silicon nitride; 10. The polishing composition described in 9. above, wherein the Low-k material is OSiOC; 11. The polishing composition according to 9. or 10. above, wherein the ratio of the polishing rate of the Low-k material to the polishing rate of the silicon nitride (polishing rate of the Low-k material / polishing rate of silicon nitride) is 40 or more; 12. A polishing method comprising the step of polishing an object to be polished containing a low-k material and silicon nitride using any of the polishing compositions described in 1. to 11. above; 13. A method for manufacturing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing a low-k material and silicon nitride by the polishing method described in 12. above; 14. A polishing rate inhibitor for polishing objects having silicon-nitrogen bonds, comprising a linear polyphosphate or a salt thereof with a degree of condensation of 3 or more. [Examples]

[0086] 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. In the following examples, unless otherwise specified, the operations were carried out under conditions of room temperature (20°C to 25°C) and relative humidity of 40%RH to 50%RH. The physical properties were measured as follows.

[0087] <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.).

[0088] <Zeta potential (ζ potential) of abrasive grains> The zeta potential (ζ potential) of abrasive grains in the polishing composition was measured using a zeta potential measuring device (device name "ELS-Z2") manufactured by Otsuka Electronics Co., Ltd.

[0089] <pH of the abrasive composition> The pH of the polishing composition was measured using a pH meter (manufactured by Horiba, Ltd., model number: LAQUA).

[0090] <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®).

[0091] <Sulfonic acid-modified colloidal silica> [Manufacturing example] Sulfonic acid-modified colloidal silica was obtained as abrasive grains by following the procedure below.

[0092] (Preparation process of raw material colloidal silica dispersion (unmodified silica particles)) In a flask, 4080 g of methanol, 610 g of water, and 168 g of 29% by mass aqueous ammonia solution were mixed and the solution temperature was maintained at 20°C. A mixture of 135 g of methanol and 508 g of tetramethoxysilane (TMOS) was then added dropwise over a period of 25 minutes. Subsequently, the mixture was heated and concentrated by water substitution under conditions of pH 7 or higher to obtain 1000 g of 19.5% by mass silica sol (average secondary particle size: 34 nm).

[0093] (Surface modification process) Next, to 1000 g of the silica sol obtained above (195 g in terms of silica solids), 1.2 g of 3-mercaptopropyltrimethoxysilane (MPS, silane coupling agent, product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.), which had been mixed separately with 4.8 g of methanol (silane coupling agent concentration relative to the total mass of silica solids: 0.6% by mass), was added dropwise at a flow rate of 1 mL / min. After heating, the mixture was replaced with pure water for 3 hours after boiling.

[0094] Next, to allow it to cool, the reaction solution was left to stand overnight, and 0.0343 g of 30% hydrogen peroxide solution (3 moles per mole of silane coupling agent) was added, and it was brought to a boil again. After that, the mixture was replaced with pure water for 2 hours, and then cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silica.

[0095] (Example 1) <Preparation of polishing composition> To water as a dispersion medium, sulfonic acid-modified colloidal silica (average secondary particle size: 34 nm), which was obtained in the above manufacturing example, was added to a final concentration of 1% by mass. Furthermore, decyldimethylamine oxide (manufactured by Lion Specialty Chemicals Co., Ltd.) was added to a final concentration of 200 ppm by mass, and a mixture of polyphosphates with a condensation degree of 4 to 9 (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to a final concentration of 600 ppm by mass, and the mixture was stirred (stirring temperature: 25°C, stirring time: 20 minutes). Subsequently, the pH of the polishing composition was adjusted to 3.0 using ammonia as a pH adjuster to complete the polishing composition. The electrical conductivity of the obtained polishing composition was 2 mS / cm.

[0096] (Example 2) An abrasive composition was prepared in the same manner as in Example 1, except that tripolyphosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of a mixture of polyphosphates with a condensation degree of 4 to 9.

[0097] (Example 3) An abrasive composition was prepared in the same manner as in Example 1, except that dodecyldimethylamine oxide (manufactured by Lion Specialty Chemicals, Inc.) was used instead of decyldimethylamine oxide.

[0098] (Example 4) An abrasive composition was prepared in the same manner as in Example 1, except that a mixture of sodium polyphosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) with a condensation degree of 4 to 9 was used instead of a mixture of polyphosphates with a condensation degree of 4 to 9, and nitric acid was used instead of ammonia as a pH adjuster.

[0099] (Example 5) An abrasive composition was prepared in the same manner as in Example 4, except that sodium tripolyphosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of a mixture of sodium polyphosphates with a condensation degree of 4 to 9.

[0100] (Example 6) An abrasive composition was prepared in the same manner as in Example 1, except that hydrogen peroxide was further added to the abrasive composition so that its final concentration was 1% by mass.

[0101] (Example 7) The polishing composition was prepared in the same manner as in Example 1, except that the pH was adjusted to 5.0.

[0102] (Example 8) An abrasive composition was prepared in the same manner as in Example 1, except that a mixture of polyphosphates with a degree of condensation of 4 to 9 was added to the abrasive composition so that the final concentration in the abrasive composition was 1000 ppm by mass.

[0103] (Example 9) An abrasive composition was prepared in the same manner as in Example 1, except that a mixture of polyphosphates with a condensation degree of 4 to 9 was added to the abrasive composition so that the final concentration in the abrasive composition was 200 ppm by mass.

[0104] (Comparative Example 1) An abrasive composition was prepared in the same manner as in Example 1, except that a mixture of decyldimethylamine oxide and polyphosphate with a condensation degree of 4 to 9 was not used, and nitric acid was used instead of ammonia as a pH adjuster.

[0105] (Comparative Example 2) An abrasive composition was prepared in the same manner as in Example 1, except that a mixture of polyphosphates with a condensation degree of 4 to 9 was not used, and nitric acid was used instead of ammonia as a pH adjuster.

[0106] (Comparative Example 3) An abrasive composition was prepared in the same manner as in Example 1, except that decyldimethylamine oxide was not used.

[0107] (Comparative Example 4) An abrasive composition was prepared in the same manner as in Example 1, except that ethylenediaminetetramethylenephosphonic acid (EDTMP) was used instead of a mixture of polyphosphates with a condensation degree of 4 to 9.

[0108] (Comparative Example 5) An abrasive composition was prepared in the same manner as in Example 1, except that orthophosphoric acid was used instead of a mixture of polyphosphoric acids with a condensation degree of 4 to 9.

[0109] (Comparative Example 6) An abrasive composition was prepared in the same manner as in Example 1, except that pyrophosphate was used instead of a mixture of polyphosphates with a condensation degree of 4 to 9.

[0110] (Comparative Example 7) The polishing composition was prepared in the same manner as in Example 1, except that the pH was adjusted to 7.0.

[0111] (Comparative Example 8) The polishing composition was prepared in the same manner as in Example 1, except that the pH was adjusted to 9.0.

[0112] (Comparative Example 9) An abrasive composition was prepared in the same manner as in Example 1, except that colloidal ceria (average secondary particle size: 34 nm) was used instead of sulfonic acid-modified colloidal silica, and nitric acid was used instead of ammonia as a pH adjuster.

[0113] (Comparative Example 10) An abrasive composition was prepared in the same manner as in Example 1, except that dodecylbenzenesulfonic acid was used instead of a mixture of polyphosphates with a condensation degree of 4 to 9, and nitric acid was used instead of ammonia as a pH adjuster.

[0114] (Comparative Example 11) An abrasive composition was prepared in the same manner as in Example 1, except that sodium hexametaphosphate was used instead of a mixture of polyphosphates with a condensation degree of 4 to 9, and nitric acid was used instead of ammonia as a pH adjuster.

[0115] (Comparative Example 12) An abrasive composition was prepared in the same manner as in Example 1, except that trimethylamine oxide was used instead of decyldimethylamine oxide.

[0116] The composition of the polishing compositions for each example and comparative example is shown in Table 1 below. In Table 1, "-" indicates that the agent was not used. In Table 1, "Polyphosphate (n=4 or more)" refers to a mixture of polyphosphates with a condensation degree of 4 to 9, and "Sodium polyphosphate (n=4 or more)" refers to a mixture of sodium polyphosphates with a condensation degree of 4 to 9.

[0117] [Table 1]

[0118] [evaluation] For the polishing targets (substrates), we prepared coupons consisting of a 300mm wafer (SiOC film, manufactured by Advance Materials Technology Co., Ltd., product name: BD2x 5kA Blanket) and a 300mm wafer (Si3N4 (silicon nitride) film, manufactured by Advance Materials Technology Co., Ltd., product name: LP-SiN 3.5KA Blanket), each cut into 60mm x 60mm chips.

[0119] Using the polishing composition obtained above, the prepared substrate was polished under the following polishing conditions, and the polishing speed was measured: (polishing conditions) Grinding machine: EJ-380IN-CH (manufactured by Nippon Engis Co., Ltd.) Polishing pad: Hard polyurethane pad (manufactured by Nitta DuPont, IC1010) Polishing pressure: 2.0 psi (1 psi = 6894.76 Pa) Platen rotation speed: 60 rpm Head (carrier) rotation speed: 60 rpm Flow rate of polishing composition: 100 ml / min Polishing time: 30 seconds.

[0120] (polishing speed) The film thickness was determined using an optical interference film thickness measuring device (manufactured by SCREEN Holdings Co., Ltd., model number: Lambda Ace VM-2030), and the polishing speed was evaluated by dividing the difference in film thickness before and after polishing by the polishing time (see formula below). The polishing speed for SiOC films is preferably 600 Å / min or higher, and the polishing speed for Si3N4 (silicon nitride) films is preferably 30 Å / min or lower.

[0121]

number

[0122] (Selective ratio of polishing speed) The selectivity ratio for polishing speed was determined by dividing the polishing speed of the SiOC film obtained above by the polishing speed of the Si3N4 film (silicon nitride film). A higher selectivity ratio is preferable, but a value of 40 or higher is preferable.

[0123] The evaluation results are shown in Table 2 below.

[0124] [Table 2]

[0125] As is clear from Table 2 above, when the polishing composition of the example was used, the polishing rate of the low-k material, SiOC, increased, and the ratio of the polishing rate of SiOC to the polishing rate of silicon nitride (polishing rate selectivity ratio) was 40 or higher, indicating that a high value was obtained. On the other hand, when the polishing compositions of Comparative Examples 1, 3, and 7-12 were used, the polishing rate of SiOC decreased. Furthermore, in all comparative examples, the polishing rate selectivity ratio decreased to less than 40.

[0126] Table 2 above shows the results obtained by polishing objects containing low-k material (SiOC) and objects containing silicon nitride separately. However, it is presumed that similar polishing speed and polishing speed selectivity ratio results as in Table 2 can be obtained even when polishing objects containing both low-k material and silicon nitride.

Claims

1. Abrasive grains and A trialkylamine oxide compound having at least one linear or branched alkyl group with 6 to 17 carbon atoms, A linear polyphosphate or a salt thereof with a degree of condensation of 3 or more, An abrasive composition containing and having a pH of less than 7.0, An abrasive composition wherein the zeta potential of the abrasive grains in the abrasive composition is negative.

2. The polishing composition according to claim 1, wherein the trialkylamine oxide compound has only one linear or branched alkyl group having 6 to 17 carbon atoms.

3. The polishing composition according to claim 1, wherein the number of carbon atoms in the alkyl group is 8 or more and 14 or less.

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

5. The polishing composition according to claim 1, wherein the concentration of the polyphosphate or its salt relative to the total mass of the polishing composition is 10 ppm by mass or more and 2000 ppm by mass or less.

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

7. The polishing composition according to claim 1, further comprising a pH adjusting agent.

8. The polishing composition according to claim 1, further comprising a dispersion medium.

9. The polishing composition according to claim 1, used for polishing objects containing Low-k material and silicon nitride.

10. The polishing composition according to claim 9, wherein the Low-k material is SiOC.

11. The polishing composition according to claim 9, wherein the ratio of the polishing rate of the Low-k material to the polishing rate of the silicon nitride (polishing rate of the Low-k material / polishing rate of silicon nitride) is 40 or more.

12. A polishing method comprising the step of polishing an object to be polished containing a Low-k material and silicon nitride using the polishing composition described in any one of claims 1 to 11.

13. A method for manufacturing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing a Low-k material and silicon nitride by the polishing method described in claim 12.

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