JP2023131086A - Polishing composition, polishing method, and method for manufacturing semiconductor substrate - Google Patents

Abstract

To provide means for improving a ratio of an SiOC polishing rate to an SiN polishing rate.SOLUTION: A polishing composition contains: abrasive grains including at least one kind of zirconia particles; a selectivity improver which contains at least one kind of salt comprising a monovalent anion and a monovalent or higher cation and improves a ratio of an SiOC polishing rate to an SiN polishing rate; and a pH adjuster containing at least one kind of acid. The polishing composition has a pH higher than 3.0 and lower than 7.0. The zeta potential of the abrasive grains is a positive value.SELECTED DRAWING: None

Description

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

In recent years, new microfabrication techniques have been developed as LSIs (Large Scale Integration) become more highly integrated and performant. Chemical mechanical polishing (CMP) is one such method, and is frequently used in the LSI manufacturing process, especially in the flattening of interlayer insulating films in the multilayer wiring formation process, metal plug formation, and buried wiring (damascene wiring) formation. This is a technology that can be used.

Low dielectric constant (Low-k) materials are being adopted as materials for interlayer insulating films in multilayer wiring formation processes in order to suppress inter-wiring capacitance. SiOC (carbon-containing silicon oxide in which SiO ₂ is doped with C) formed by a plasma CVD method is widely used as a low dielectric constant (Low-k) material.

As a technique for polishing SiOC, Patent Document 1 discloses a polishing composition containing abrasive grains containing cerium and hydroxyalkylcellulose, and having a pH of 6.0 or more. According to Patent Document 1, with such a configuration, it is possible to improve the polishing rate of SiOC.

Japanese Patent Application Publication No. 2017-139349

Recently, substrates containing both SiOC and SiN (silicon nitride) have come into use, and there is an increasing demand for selectively polishing the SiOC in such substrates. However, the polishing composition described in Patent Document 1 has a problem in that the ratio (selectivity) of the polishing rate of SiOC to the polishing rate of SiN may be low.

Therefore, an object of the present invention is to provide means for improving the ratio of the polishing rate of SiOC to the polishing rate of SiN.

The present inventors conducted extensive studies to solve the above problems. As a result, in a polishing composition containing zirconia particles (abrasive grains), a salt consisting of a monovalent anion and a monovalent or higher cation (selectivity improver), and an acid (pH adjuster), pH and abrasive The inventors have discovered that the above problems can be solved by controlling the zeta potential of each grain within a specific range, and have completed the present invention.

That is, one embodiment of the present invention includes abrasive grains containing at least one kind of zirconia particles and at least one kind of salt consisting of a monovalent anion and a monovalent or higher cation, and the polishing rate of SiOC is lower than that of SiN. The abrasive grains include a selectivity improver that improves the speed ratio and a pH adjuster containing at least one type of acid, the pH is more than 3.0 and less than 7.0, and the zeta potential of the abrasive grains is positive. It is a polishing composition with a value.

According to the present invention, the ratio of the polishing rate of SiOC to the polishing rate of SiN can be improved.

Embodiments of the present invention will be described below, but the technical scope of the present invention should be determined based on the claims and is not limited to the following embodiments.

In this specification, unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20° C. or higher and 25° C. or lower)/relative humidity of 40% RH or higher and 50% RH or lower. In addition, in this specification, the ratio of the polishing rate of SiOC to the polishing rate of SiN is also simply referred to as "selectivity ratio", and a selectivity improver that improves the ratio of the polishing rate of SiOC to the polishing rate of SiN, It is also simply referred to as a "selectivity improver." The embodiments described in this specification can be combined arbitrarily to form other embodiments.

One embodiment of the present invention includes abrasive grains containing at least one type of zirconia particles and at least one type of salt consisting of a monovalent anion and a monovalent or higher cation, and the polishing rate of SiOC is lower than that of SiN. a selectivity improver that improves the ratio and a pH adjuster containing at least one type of acid, the pH is more than 3.0 and less than 7.0, and the zeta potential of the abrasive grains is a positive value. It is a polishing composition. With the above configuration, the ratio (selectivity) of the polishing rate of SiOC to the polishing rate of SiN can be improved.

The mechanism by which the above effects are obtained is thought to be as follows. However, the following mechanism is only a speculation, and the scope of the present invention is not limited thereby.

Zirconia particles as abrasive grains can polish SiOC at a higher speed than silica particles, ceria particles, and alumina particles.

In the salt consisting of a monovalent anion and a monovalent or higher cation as a selectivity improver, the monovalent anion adheres to the surface of the abrasive grains containing zirconia particles, reducing the hydrophilicity of the surface. This makes it easier for abrasive grains to approach the highly hydrophobic surface of SiOC, improving the polishing rate of SiOC. On the other hand, when a salt consisting of an anion with a valence of 2 or more and a cation with a valence of 1 or more is used, the anion adheres to the abrasive grain and the zeta potential of the abrasive grain becomes a negative (-) value. The surface of the abrasive grains can repel. As a result, the polishing rate of SiOC decreases, and there is a possibility that a sufficient selectivity may not be obtained.

In the acid as a pH adjuster, as described above, anions adhere to the surface of the abrasive grains containing zirconia particles, reducing the hydrophilicity of the surface. This makes it easier for abrasive grains to approach the highly hydrophobic surface of SiOC, improving the polishing rate of SiOC. Moreover, the pH of the polishing composition is controlled to be more than 3.0 and less than 7.0 by the pH adjuster. When the pH is within the above range, a sufficient selectivity improvement effect can be obtained. On the other hand, if the pH is below 3.0, the surface of the SiOC will be positively charged (+) and will repel the abrasive grains having a positive (+) zeta potential, which may reduce the polishing rate of the SiOC. be. When the pH is 7.0 or more, the zeta potential of the abrasive grains containing zirconia particles becomes near zero (0), and the repulsion between the abrasive grains becomes small and aggregation may occur (the isoelectric point of the zirconia particles is Usually the pH is 7.0 to 9.0 (around 8.0).

In addition, when the pH is within a range of more than 3.0 and less than 7.0, the abrasive grains containing zirconia particles have a positive (+) zeta potential in the polishing composition, so that the zeta potential becomes negative (-). Abrasive grains having a positive (+) zeta potential are attracted to the surface of the charged SiOC, improving the polishing rate of the SiOC.

As a result, by applying the polishing composition according to the present embodiment to an object to be polished containing SiOC and SiN, it becomes possible to polish SiOC at a high speed. As a result, it becomes possible to significantly improve the ratio of the polishing rate of SiOC to the polishing rate of SiN.

Hereinafter, the polishing composition according to this embodiment will be explained in detail.

[Object to be polished]
The object to be polished using the polishing composition of this embodiment preferably contains SiOC (carbon-added silicon oxide) and SiN (silicon nitride).

The object to be polished may further contain other materials than SiOC and SiN. Examples of other materials include silicon oxide, single crystal silicon, polycrystalline silicon (polysilicon), amorphous silicon (amorphous silicon), polycrystalline silicon doped with n-type or p-type impurities, n-type or p Amorphous silicon doped with type impurities, SiGe, elemental metals (e.g. tungsten, copper, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium, etc.), metal nitrides ( For example, tantalum nitride (TaN), titanium nitride (TiN), etc.), organic materials (for example, amorphous carbon, spin-on carbon (SOC), diamond-like carbon (DLC), nanocrystalline diamond, graphene, etc.), etc. Can be mentioned.

A film containing these materials can be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD), spin coating, or the like.

[Abrasive]
The polishing composition according to this embodiment includes zirconia particles as abrasive grains. Zirconia particles have the effect of mechanically polishing the object to be polished. Zirconia particles may be used alone or in combination of two or more. Furthermore, as the zirconia particles, commercially available products or synthetic products may be used. Note that zirconia usually contains hafnia (HfO ₂ ), which is an inevitable impurity. In this specification, numerical values related to composition such as content are calculated by regarding hafnia (HfO ₂ ), which is an inevitable impurity, as zirconia (ZrO ₂ ).

The zirconia particles are preferably colloidal zirconia particles or ground/calcined zirconia particles, and more preferably colloidal zirconia particles. The zirconia particles may also be undoped or doped, for example with yttrium (Y) or its oxide, calcium oxide, or magnesium oxide. Note that the crystal structure of the zirconia particles is not particularly limited, and may be monoclinic, tetragonal, or cubic.

The shape of the zirconia particles is not particularly limited, and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and square prisms, cylindrical shapes, bale-like shapes where the center of the cylinder bulges out more than the ends, donut-like shapes where the center of a disk penetrates through, plate-like shapes, There are various shapes such as the so-called cocoon-shaped shape with a constriction in the center, the so-called associative spherical shape where multiple particles are integrated, the so-called confetti-shaped shape with multiple protrusions on the surface, rod shape, diamond shape, square shape, rugby ball shape, etc. The shape is not particularly limited.

Zirconia particles are aggregates containing primary particles and/or secondary particles. Agglomerates may be formed from a combination of individual particles, which are known in the art as primary particles, whereas aggregated combinations of particles are known in the art as secondary particles. ing. The zirconia particles in the polishing composition can be in the form of primary particles or secondary particles that are aggregates of primary particles. Alternatively, zirconia particles may exist in both primary and secondary particle form. In a preferred embodiment, the zirconia particles are present in the polishing composition at least partially in the form of secondary particles.

The particle diameter of the zirconia particles according to this embodiment is preferably 5 nm or more and 200 nm or less, more preferably 10 nm or more and 150 nm or less, still more preferably 30 nm or more and 100 nm or less, and particularly preferably 50 nm or more and 90 nm or less. When the particle size of the zirconia particles is 5 nm or more, polishing becomes efficient and a sufficient polishing rate can be obtained. When the particle diameter of the zirconia particles is 200 nm or less, the dispersion stability of the polishing composition is excellent. In this specification, the particle diameter of zirconia particles is defined as the particle diameter (D50, hereinafter referred to as (also simply referred to as "D50"). The D50 of the zirconia particles in this specification employs the value measured by the method described in the Examples.

In this embodiment, one of the characteristics is that the abrasive grains (preferably zirconia particles) in the polishing composition have a positive zeta potential. As a result, abrasive grains having a positive (+) zeta potential are attracted to the negatively (-) charged surface of the SiOC, thereby improving the polishing rate of the SiOC. The zeta potential of the abrasive grains (preferably zirconia particles) in the polishing composition is preferably more than 0 mV and less than +70 mV, more preferably more than +10 mV and less than +60 mV, still more preferably more than +20 mV and less than +50 mV, Particularly preferably, it is +30 mV or more and +45 mV or less. When the zeta potential of the abrasive grains (preferably zirconia particles) in the polishing composition is +10 mV or more, the force with which the abrasive grains (preferably zirconia particles) are attracted to the negatively (-) charged surface of SiOC becomes large. Therefore, polishing becomes even more efficient. When the zeta potential of the abrasive grains (preferably zirconia particles) in the polishing composition is +70 mV or less, the abrasive grains can be easily removed by cleaning after polishing. The zeta potential of the abrasive grains in the polishing composition can be controlled by the type or amount of the pH adjuster or selectivity improver in the polishing composition. Note that the value measured by the method described in Examples is used as the zeta potential of the abrasive grain in this specification.

The content (concentration) of abrasive grains (preferably zirconia particles) in the polishing composition is not particularly limited. In the case of a polishing composition (typically a polishing liquid in the form of a slurry, sometimes referred to as a working slurry or polishing slurry) that is used as a polishing liquid to polish an object to be polished, the abrasive particles are The content is preferably 0.01% by mass or more and 10.0% by mass or less, more preferably 0.01% by mass or more and 5.0% by mass or less, based on the total mass of the polishing composition. More preferably 0.01% by mass or more and 1.0% by mass or less, even more preferably 0.05% by mass or more and 1.0% by mass or less, particularly preferably 0.06% by mass or more and 0.50% by mass. % or less, most preferably 0.07% by mass or more and 0.30% by mass or less. When the content of abrasive grains is within the above range, a sufficient polishing rate for SiOC can be obtained, and a polishing composition with excellent cost can be obtained.

In addition, in the case of a polishing composition that is diluted and used for polishing (i.e., concentrated solution, working slurry stock solution), the content of abrasive grains is usually 30% by mass from the viewpoint of storage stability and filterability. It is appropriate that the amount is not more than 25% by mass, preferably not more than 25% by mass. Further, from the viewpoint of taking advantage of the advantage of forming a concentrated solution, the content of abrasive grains is preferably 0.3% by mass or more, more preferably 0.5% by mass or more.

In addition, when the polishing composition contains two or more types of abrasive grains, the content of the abrasive grains is intended to be the total amount thereof.

The polishing composition according to this embodiment may further contain abrasive grains other than zirconia particles within a range that does not impede the effects of the present invention. Such other abrasive grains may be any of inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include unmodified silica, cation-modified 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 polymethyl methacrylate (PMMA) particles. These other abrasive grains may be used alone or in combination of two or more. Further, as the other abrasive grains, commercially available products or synthetic products may be used.

However, the content of the other abrasive grains is preferably 20% by mass or less, more preferably 10% by mass or less, and 5% by mass or less based on the total mass of the abrasive grains. It is more preferable that the content is 1% by mass or less, and particularly preferably 1% by mass or less. Most preferably, the content of other abrasive grains is 0% by mass, that is, the abrasive grains are composed only of zirconia particles.

[Selectivity improver]
The polishing composition of this embodiment includes a selectivity improver that improves the ratio of the polishing rate of SiOC to the polishing rate of SiN. The selectivity improver contains at least one salt consisting of a monovalent anion and a monovalent or higher cation. The salts may be used alone or in combination of two or more.

The anion constituting the salt must be monovalent. If an anion with a valence of two or more is used, the anion may adhere to the abrasive grains and the zeta potential of the abrasive grains may take a negative (-) value. As a result, the polishing rate of SiOC decreases, and there is a possibility that a sufficient selectivity may not be obtained. Monovalent anions include halide ions such as fluoride ion, chloride ion, bromide ion, and iodide ion, nitrate ion, acetate ion, formate ion, propionate ion, butyrate ion, valerate ion, and 2-methyl. Butyrate ion, n-hexanoate ion, 3,3-dimethylbutyrate ion, 2-ethylbutyrate ion, 4-methylpentanoate ion, n-heptanoate ion, 2-methylhexanoate ion, n-octanoate ion, 2 -Ethylhexanoate ion, benzoate ion, glycolic acid ion, salicylate ion, glycerate ion, lactic acid ion, 2-furoate ion, 3-furoate ion, 2-tetrahydrofurancarboxylate ion, methoxyacetate ion, methoxy Examples include phenylacetate ion, phenoxyacetate ion, methanesulfonate ion, ethanesulfonate ion, isethionate ion, and the like. Among them, from the viewpoint of further improving the selectivity, nitrate ion and acetate ion are preferred, and acetate ion is more preferred.

The valence of the cation constituting the salt is not particularly limited, and may be monovalent, divalent, trivalent, or the like. Examples of monovalent or higher cations include sodium ions, potassium ions, lithium ions, calcium ions, magnesium ions, ammonium ions, and the like. Among these, from the viewpoint of further improving the selectivity, sodium ions, potassium ions, and ammonium ions are preferred, and ammonium ions are more preferred.

Specific examples of salts include ammonium acetate, sodium acetate, potassium acetate, lithium acetate, magnesium acetate, calcium acetate, ammonium nitrate, sodium nitrate, potassium nitrate, lithium nitrate, magnesium nitrate, calcium nitrate, ammonium fluoride, sodium fluoride, and fluoride. Potassium chloride, lithium fluoride, magnesium fluoride, calcium fluoride, ammonium chloride, sodium chloride, potassium chloride, lithium chloride, magnesium chloride, calcium chloride, ammonium bromide, sodium bromide, potassium bromide, lithium bromide, odor Examples thereof include magnesium chloride, calcium bromide, ammonium iodide, sodium iodide, potassium iodide, lithium iodide, magnesium iodide, and calcium iodide. Among these, from the viewpoint of further improving the selectivity, ammonium acetate, sodium acetate, potassium acetate, and ammonium nitrate are preferred, ammonium acetate, sodium acetate, and potassium acetate are more preferred, and ammonium acetate is even more preferred. That is, according to a preferred embodiment of the invention, the selectivity improver comprises ammonium acetate. According to a preferred embodiment of the invention, the selectivity improver consists only of ammonium acetate.

The content (concentration) of the selectivity improver (preferably ammonium acetate) in the polishing composition is not particularly limited. In the case of polishing compositions (typically slurry-like polishing liquids, sometimes referred to as working slurries or polishing slurries) that are used directly as polishing liquids to polish objects to be polished, the selectivity can be improved. From the viewpoint of improving the selectivity, the content (concentration) of the agent is preferably 30 ppm or more and 2000 ppm or less, more preferably 50 ppm or more and 1000 ppm or less, and even more preferably 75 ppm, based on the total mass of the polishing composition. The content ranges from 100 ppm to 700 ppm, particularly preferably from 100 ppm to 700 ppm, and most preferably from 300 ppm to 600 ppm. When the content of the selectivity improver is within the above range, the selectivity can be further improved. In this specification, "ppm" means "mass ppm".

Further, from the viewpoint of further improving the stability of the polishing composition, the content (concentration) of the selectivity improver (preferably ammonium acetate) is preferably 50 ppm or more based on the total mass of the polishing composition. It is 500 ppm or less, more preferably 50 ppm or more and 200 ppm or less.

In addition, in the case of a polishing composition that is diluted and used for polishing (i.e., concentrated solution, working slurry stock solution), the content (concentration) of the selectivity improver (preferably ammonium acetate) is determined by the storage stability and filtration properties. From these viewpoints, it is usually appropriate that the content is 3% by mass (30,000 ppm) or less, preferably 2% by mass (20,000 ppm) or less. Further, from the viewpoint of taking advantage of the advantage of forming a concentrated solution, the content of the selectivity improver is preferably 100 ppm or more, more preferably 500 ppm or more.

In addition, when the polishing composition contains two or more types of selectivity improvers, the content of the selectivity improvers is intended to be the total amount thereof.

Further, the ratio of the amount of selectivity improver to the amount of abrasive grains (amount of selectivity improver/amount of abrasive grains) (mass ratio) is preferably 0.01 or more and 5 or less, more preferably 0.01 to 5. It is 0.05 or more and 1 or less, more preferably 0.1 or more and 0.8 or less, and even more preferably 0.3 or more and 0.7 or less. When the ratio of the amount of selectivity improver to the amount of abrasive grains is within the above range, the selectivity can be further improved.

The polishing composition according to the present embodiment includes a substance other than the above-mentioned salt consisting of the monovalent anion and monovalent or higher cation, which has the function of improving the selectivity within a range that does not impede the effects of the present invention. may further be included as a selectivity improver. However, the content of the other substance is preferably 20% by mass or less, more preferably 10% by mass or less, and 5% by mass or less based on the total mass of the selectivity improver. is more preferable, and particularly preferably 1% by mass or less. Most preferably, the content of other substances is 0% by mass, that is, the selectivity improver consists only of a salt consisting of a monovalent anion and a monovalent or higher cation.

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

From the viewpoint of not inhibiting the action of the components contained in the polishing composition, the dispersion medium is preferably water containing as few impurities as possible, and specifically, water containing as few impurities as possible is preferable. It is more preferable to use pure water, ultrapure water, or distilled water that has been filtered to remove foreign substances.

[pH and pH adjuster]
The polishing composition according to this embodiment has a pH of more than 3.0 and less than 7.0. If the pH is less than 3.0, the polishing rate of SiOC decreases as described above, and there is a possibility that the desired selectivity cannot be obtained. If the pH is 7.0 or higher, agglomeration of abrasive grains may occur as described above.

From the viewpoint of improving the selectivity, the pH of the polishing composition is preferably 3.5 or more and 6.5 or less, more preferably 4.0 or more and 6.0 or less, and even more preferably 4.5 or more. It is 5.5 or less. Note that the pH of the polishing composition can be measured with a pH meter. For pH in this specification, values measured by the method described in Examples are employed.

The polishing composition according to this embodiment includes a pH adjuster. The pH adjuster includes at least one acid. The acid may be either an inorganic acid or an organic acid. The acids may be used alone or in combination of two or more.

Specific examples of inorganic acids include hydrochloric acid, hydrofluoric acid, nitric acid, and the like. Specific examples of organic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n- Heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, lactic acid, 2-furancarboxylic acid, 3-furancarboxylic acid, 2-tetrahydrofurancarboxylic acid , methoxyacetic acid, methoxyphenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid, isethionic acid, and the like. Among these, nitric acid and acetic acid are preferred, and acetic acid is more preferred, from the viewpoint of further improving the selectivity. That is, according to a preferred embodiment of the invention, the pH adjusting agent includes acetic acid. According to a preferred embodiment of the invention, the pH adjusting agent consists only of acetic acid.

The amount of the pH adjuster added is not particularly limited, and may be adjusted as appropriate so that the polishing composition has a desired pH.

Note that a base may be used as the pH adjuster if necessary, but according to a preferred embodiment of the present invention, the pH adjuster consists of at least one type of acid.

[Additive]
The polishing composition according to the present embodiment may contain known materials that can be used in polishing compositions, such as a dispersant, an oxidizing agent, a complexing agent, a preservative, and a fungicide, within a range that does not impair the effects of the present invention. It may further contain additives. Since the polishing composition according to this embodiment is acidic, it preferably contains a fungicide. In addition, it is also a preferred embodiment to include a dispersant because it improves the dispersion stability of abrasive grains (especially zirconia particles). That is, in a preferred embodiment of the present invention, the polishing composition contains abrasive grains containing at least one type of zirconia particles, and at least one type of salt consisting of a monovalent anion and a monovalent or higher cation, and contains SiN. At least one selected from the group consisting of a selectivity improver that improves the ratio of the polishing rate of SiOC to the polishing rate, a pH adjuster containing at least one acid, a dispersion medium, a fungicide, and a dispersant. including. In a more preferred embodiment of the present invention, the polishing composition includes abrasive grains containing at least one type of zirconia particles and at least one type of salt consisting of a monovalent anion and a monovalent or higher cation, and polishes SiN. At least one selected from the group consisting of a selectivity improver that improves the ratio of the polishing rate of SiOC to the polishing speed, a pH adjuster containing at least one type of acid, a dispersion medium, a fungicide, and a dispersant. substantially consists of. Here, "the polishing composition contains abrasive grains containing at least one kind of zirconia particles and at least one kind of salt consisting of a monovalent anion and a monovalent or higher cation, and polishes SiOC at a polishing rate that is higher than that of SiN." Substantially composed of a selectivity improver that improves the speed ratio, a pH adjuster containing at least one acid, a dispersion medium, and at least one selected from the group consisting of a fungicide and a dispersant. "is used" means that the total content of abrasive grains, selectivity improver, pH adjuster, dispersion medium, and fungicide and/or dispersant exceeds 99% by mass based on the polishing composition. Upper limit: 100% by mass). Preferably, the polishing composition is composed of abrasive grains, a selectivity improver, a pH adjuster, a dispersion medium, and a fungicide and/or a dispersant (the above total content = 100% by mass).

The antifungal agent (preservative) is not particularly limited and can be appropriately selected depending on the desired use and purpose. Specifically, 1,2-benzisothiazol-3(2H)-one (BIT), 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one and phenoxyethanol.

Alternatively, the antifungal agent (preservative) may be a compound represented by the following chemical formula 1.

In the chemical formula 1, R ¹ to R ⁵ are each independently a hydrogen atom or a substituent composed of at least two atoms selected from the group consisting of carbon atoms, hydrogen atoms, and oxygen atoms. .

Examples of substituents composed of at least two atoms selected from the group consisting of carbon atoms, hydrogen atoms, and oxygen atoms include hydroxy groups, carboxy groups, alkyl groups having 1 to 20 carbon atoms, Hydroxyalkyl group having 1 to 20 carbon atoms, alkoxy group having 1 to 20 carbon atoms, hydroxyalkoxy group having 1 to 20 carbon atoms, alkoxycarbonyl group having 2 to 21 carbon atoms, 6 to 30 carbon atoms Aryl group, aralkyl group (arylalkyl group) having 7 to 31 carbon atoms, aryloxy group having 6 to 30 carbon atoms, aryloxycarbonyl group having 7 to 31 carbon atoms, aralkyloxy having 8 to 32 carbon atoms Examples include a carbonyl group, an acyl group having 1 to 20 carbon atoms, and an acyloxy group having 1 to 20 carbon atoms.

More specifically, examples of alkyl groups having 1 to 20 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group. , linear alkyl groups such as n-octyl group, n-nonyl group, n-decyl group; isopropyl group, isobutyl group, s-butyl group, t-butyl group, t-amyl group, neopentyl group, 3- Methylpentyl group, 1,1-diethylpropyl group, 1,1-dimethylbutyl group, 1-methyl-1-propylbutyl group, 1,1-dipropylbutyl group, 1,1-dimethyl-2-methylpropyl group Branched alkyl groups such as , 1-methyl-1-isopropyl-2-methylpropyl group; cyclic alkyl groups such as cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, norbornenyl group, etc. It will be done.

Examples of the hydroxyalkyl group having 1 to 20 carbon atoms include hydroxymethyl group, 2-hydroxyethyl group, 2-hydroxy-n-propyl group, 3-hydroxy-n-propyl group, and 2-hydroxy-n-butyl group. group, 3-hydroxy-n-butyl group, 4-hydroxy-n-butyl group, 2-hydroxy-n-pentyl group, 3-hydroxy-n-pentyl group, 4-hydroxy-n-pentyl group, 5-hydroxy -n-pentyl group, 2-hydroxy-n-hexyl group, 3-hydroxy-n-hexyl group, 4-hydroxy-n-hexyl group, 5-hydroxy-n-hexyl group, 6-hydroxy-n-hexyl group etc.

Examples of alkoxy groups having 1 to 20 carbon atoms include methoxy group, ethoxy group, n-propyloxy group, n-butyloxy group, n-pentyloxy group, n-hexyloxy group, n-heptyloxy group, n-heptyloxy group, - Straight chain alkoxy groups such as octyloxy, n-nonyloxy, n-decyloxy groups; isopropyloxy, isobutyloxy, s-butyloxy, t-butyloxy, t-amyloxy, neopentyloxy groups , 3-methylpentyloxy group, 1,1-diethylpropyloxy group, 1,1-dimethylbutyloxy group, 1-methyl-1-propylbutyloxy group, 1,1-dipropylbutyloxy group, 1,1 - Branched alkoxy groups such as dimethyl-2-methylpropyloxy group, 1-methyl-1-isopropyl-2-methylpropyloxy group; cyclobutyloxy group, cyclopentyloxy group, cyclohexyloxy group, cycloheptyloxy group, Examples include cyclic alkoxy groups such as a cyclooctyloxy group and a norbornenyloxy group.

Examples of the hydroxyalkoxy group having 1 to 20 carbon atoms include hydroxymethoxy group, 2-hydroxyethoxy group, 2-hydroxy-n-propyloxy group, 3-hydroxy-n-propyloxy group, and 2-hydroxy-n-propyloxy group. -butyloxy group, 3-hydroxy-n-butyloxy group, 4-hydroxy-n-butyloxy group, 2-hydroxy-n-pentyloxy group, 3-hydroxy-n-pentyloxy group, 4-hydroxy-n-pentyloxy group group, 5-hydroxy-n-pentyloxy group, 2-hydroxy-n-hexyloxy group, 3-hydroxy-n-hexyloxy group, 4-hydroxy-n-hexyloxy group, 5-hydroxy-n-hexyloxy group group, 6-hydroxy-n-hexyloxy group, and the like.

Examples of alkoxycarbonyl groups having 2 to 21 carbon atoms include methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, butoxycarbonyl group, pentyloxycarbonyl group, hexyloxycarbonyl group, octyloxycarbonyl group, and decyloxycarbonyl group. etc.

Examples of the aryl group having 6 or more and 30 or less carbon atoms include a phenyl group, a naphthyl group, an anthranyl group, a pyrenyl group, and the like.

Examples of aralkyl groups (arylalkyl groups) having 7 to 31 carbon atoms include benzyl group, phenethyl group (phenylethyl group), and examples of aryloxy groups having 6 to 30 carbon atoms include phenyl Examples include oxy group (phenoxy group), naphthyloxy group, anthranyloxy group, and pyrenyloxy group.

Examples of the aryloxycarbonyl group having 7 to 31 carbon atoms include phenyloxycarbonyl group, naphthyloxycarbonyl group, anthranyloxycarbonyl group, pyrenyloxycarbonyl group, and the like.

Examples of the aralkyloxycarbonyl group having 8 to 32 carbon atoms include a benzyloxycarbonyl group and a phenethyloxycarbonyl group.

Examples of acyl groups having 1 to 20 carbon atoms include methanoyl group (formyl group), ethanoyl group (acetyl group), propanoyl group, butanoyl group, pentanoyl group, hexanoyl group, octanoyl group, decanoyl group, benzoyl group, etc. Can be mentioned.

Examples of acyloxy groups having 1 to 20 carbon atoms include formyloxy group, acetyloxy group, propanoyloxy group, butanoyloxy group, pentanoyloxy group, hexanoyloxy group, octanoyloxy group, and decanoyloxy group. group, benzoyloxy group, and the like.

Further, the fungicidal agent represented by the above chemical formula 1 is preferably at least one selected from the group consisting of compounds represented by the following chemical formulas 1-a to 1-c.

In the chemical formula 1, R ¹ to R ³ are each independently a substituent composed of at least two types of atoms selected from the group consisting of carbon atoms, hydrogen atoms, and oxygen atoms.

Examples of the substituent consisting of at least two types of atoms selected from the group consisting of carbon atoms, hydrogen atoms, and oxygen atoms are the same as those described above, and therefore description thereof will be omitted here.

More specific examples of the compound represented by the above chemical formula 1 include methyl parahydroxybenzoate (methyl parahydroxybenzoate), ethyl parahydroxybenzoate (ethyl parahydroxybenzoate), butyl parahydroxybenzoate (methyl parahydroxybenzoate), butyl), parahydroxybenzoic acid esters (parahydroxybenzoic acid esters) such as benzyl parahydroxybenzoate (benzyl parahydroxybenzoate); salicylic acid, methyl salicylate, phenol, catechol, resorcinol, hydroquinone, isopropylphenol, cresol, thymol, phenoxyethanol, Examples include phenylphenol (2-phenylphenol, 3-phenylphenol, 4-phenylphenol), 2-phenylethyl alcohol (phenethyl alcohol), and the like. Among these, from the viewpoint that the desired effects of the present invention can be more effectively achieved, the compound represented by the above chemical formula 1 is selected from the group consisting of ethyl paraoxybenzoate, butyl paraoxybenzoate, and phenylphenol. At least one selected from the above is preferred, and butyl paraoxybenzoate is more preferred.

Alternatively, the fungicide (preservative) can be an unsaturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, and ricinoleic acid; diunsaturated fatty acids such as sorbic acid, linoleic acid, and eicosadienoic acid; linolenic acid, and pinolenic acid. , triunsaturated fatty acids such as eleostearic acid; tetraunsaturated fatty acids such as stearidonic acid and arachidonic acid; pentaunsaturated fatty acids such as boseopentaenoic acid and eicosapentaenoic acid; hexaunsaturated fatty acids such as docosahexaenoic acid and nisic acid; etc. can be mentioned. Among these, sorbic acid is preferable as the unsaturated fatty acid from the viewpoint that the desired effects of the present invention are more effectively achieved.

In addition to the above, 1,2-alkanediols such as 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol; alkylglyceryl ethers such as 2-ethylhexylglyceryl ether (ethylhexylglycerin); Compounds such as capric acid and dehydroacetic acid may be used as antifungal agents (preservatives).

The above fungicides (preservatives) may be used alone or in combination of two or more.

When the polishing composition contains a fungicide (preservative), the content (concentration) of the fungicide (preservative) in the polishing composition is not particularly limited. For example, in the case of a polishing composition (typically a polishing liquid in the form of a slurry, sometimes referred to as a working slurry or a polishing slurry) that is used as a polishing liquid to polish an object to be polished, The lower limit of the content (concentration) of the antifungal agent (preservative) in the composition for use is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, and 0.01% by mass or more. More preferably, it is at least % by mass. Further, the upper limit of the content (concentration) of the antifungal agent (preservative) is preferably 3% by mass or less, and more preferably less than 1% by mass. That is, the content (concentration) of the fungicide (preservative) in the polishing composition is preferably 0.0001% by mass or more and 3% by mass or less, more preferably 0.001% by mass or more and 3% by mass or less, More preferably, it is 0.01% by mass or more and less than 1% by mass. Within this range, a sufficient effect to inactivate or destroy microorganisms can be obtained.

In addition, in the case of polishing compositions that are diluted and used for polishing (i.e. concentrated liquids, working slurry undiluted solutions), the content of antifungal agents (preservatives) is usually determined from the viewpoint of improving polishing speed, etc. It is suitably 10% by mass or less, more preferably 5% by mass or less. In addition, from the viewpoint of reducing the burden of processing the polishing composition after polishing use, that is, processing waste liquid, the content of the antifungal agent (preservative) is preferably 0.03% by mass or more, more preferably 0. .3% by mass or more.

In addition, when the polishing composition contains two or more types of fungicides (preservatives), the above content is intended to be the total amount of these.

The dispersant is not particularly limited and can be appropriately selected depending on the desired use and purpose. From the viewpoint of dispersibility after storage (particularly dispersibility of zirconia particles), it is preferable to use sugar alcohol. The surface of zirconia particles (abrasive grains) is usually hydrophobic, and the abrasive grains tend to aggregate with each other. In addition, the polishing composition according to the present invention improves electrical conductivity (EC) by containing at least one salt consisting of a monovalent anion and a monovalent or higher cation as a selectivity improver, and improves the electrical conductivity (EC) of zirconia. Since the electrostatic repulsion between particles (abrasive grains) is reduced, the abrasive grains are more likely to aggregate with each other. When sugar alcohol is mixed with zirconia particles (abrasive grains), the hydrophobic groups (hydrocarbon groups) of the sugar alcohol attach to the hydrophobic surface of the zirconia particles, the hydroxyl groups of the sugar alcohol are oriented to the outside of the zirconia particles, and the zirconia particle surface becomes hydrophilic. Due to this hydrophilization, the zirconia particles can easily mix with the dispersion medium (particularly water) and can exist separately as particles. In addition, sugar alcohol adheres to the surface of the abrasive grains, causing steric hindrance, and aggregation of the abrasive grains can be suppressed. Note that the dispersibility improvement mechanism of the zirconia particles described above is a speculation, and the present invention is not limited to the above speculation.

That is, in one embodiment of the present invention, the polishing composition further includes at least one dispersant selected from the group consisting of sugar alcohols.

The sugar alcohol is not particularly limited, but preferably has three or more hydroxy groups in the molecule. Specifically, pentaerythritol, dipentaerythritol, sorbitan, adonitol, maltitol, threitol, erythritol, arabinitol, ribitol, xylitol, iditol, sorbitol, mannitol, lactitol, galactitol, dulcitol, talitol, allitol, perseitol, boremitol , D-erythro-L-galaoctitol, D-erythro-L-talooctitol, erythromannooctitol, D-threo-L-galaoctitol, D-arabo-D-mannononitol, D-gluco-D - Galadesitol, bornesitol, conduritol, inositol, ononitol, pinitol, pinpolitol, quebrachytol, valienol, biscumitol, etc. Among them, sugar alcohols with a linear structure are more preferable, and specifically, xylitol, sorbitol, adonitol, threitol, erythritol, arabinitol, ribitol, iditol, mannitol, galactitol, talitol, allitol, and perseitol are preferable, and xylitol and sorbitol are more preferable. Preferably, sorbitol is more preferable. These sugar alcohols can be used alone or in combination of two or more.

The molecular weight of the sugar alcohol is not particularly limited, but is preferably 80 or more, more preferably 100 or more, and even more preferably 120 or more. The molecular weight of the sugar alcohol is not particularly limited, but is preferably less than 1000, more preferably 600 or less, even more preferably 400 or less, and particularly preferably 200 or less. That is, the molecular weight of the sugar alcohol is preferably 80 or more and less than 1000, more preferably 100 or more and 600 or less, even more preferably 120 or more and 400 or less, particularly preferably 120 or more and 200 or less.

When the polishing composition of the present invention further contains a dispersant (especially sugar alcohol), the content (concentration) of the dispersant (especially sugar alcohol) is not particularly limited and is appropriate depending on the desired use and purpose. can be selected. For example, in the working slurry (polishing slurry), the content (concentration) of the dispersant (especially sugar alcohol) in the polishing composition is, for example, 10 ppm or more, preferably 50 ppm, based on the total mass of the polishing composition. Above, it is more preferably 80 ppm or more, still more preferably 90 ppm or more. Further, the upper limit of the content (concentration) of the dispersant (especially sugar alcohol) in the polishing composition is, for example, 500 ppm or less, preferably 300 ppm or less, and more preferably 300 ppm or less, based on the total mass of the polishing composition. is 200 ppm or less, more preferably less than 200 ppm. That is, the content (concentration) of the dispersant (especially sugar alcohol) in the polishing composition is, for example, from 10 ppm to 500 ppm, preferably from 50 ppm to 500 ppm, more preferably from 50 ppm to 500 ppm, based on the total mass of the polishing composition. is 80 ppm or more and 500 ppm or less, more preferably 90 ppm or more and 300 ppm or less, particularly preferably 90 ppm or more and 200 ppm or less, and most preferably 90 ppm or more and less than 200 ppm. If the content of the dispersant is within this range, good dispersibility can be maintained even after abrasive grains (especially zirconia particles) are stored for a long period of time.

The polishing composition according to this embodiment may be of a one-component type or a multi-component type such as a two-component type. Further, the polishing composition according to the present embodiment can be prepared by diluting the stock solution of the polishing composition with a diluent such as water, for example, 2 to 100 times, preferably 2 to 50 times, more preferably 3 to 5 times, on a volume basis. May be prepared by diluting 10 times.

[Method for producing polishing composition]
The method for producing the polishing composition according to the present embodiment is not particularly limited, and for example, abrasive grains, a selectivity improver, a pH adjuster, and optionally additives are mixed in a dispersion medium (preferably in water). It can be obtained by stirring and mixing. Details of each component are as described above.

The temperature at which each component is mixed is not particularly limited, but is preferably 10° C. or higher and 40° C. or lower, and heating may be used to increase the dissolution rate. Further, the mixing time is not particularly limited as long as uniform mixing can be achieved.

[Polishing method and semiconductor substrate manufacturing method]
The polishing composition described above is suitably used for polishing objects to be polished containing SiOC and SiN. Therefore, according to another aspect of the present invention, there is provided a polishing method including the step of polishing a SiOC and SiN polishing target using the polishing composition described above. According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor substrate, which includes the step of polishing a semiconductor substrate containing SiOC and SiN using the polishing method described above.

The polishing device is a general-purpose polishing device that is equipped with a holder that holds a substrate, etc. that has the object to be polished, a motor that can change the rotation speed, and a polishing surface plate to which a polishing pad (polishing cloth) can be attached. Polishing equipment can be used.

As the polishing pad, general nonwoven fabrics, polyurethane, porous fluororesins, and the like can be used without particular limitations. Preferably, the polishing pad is provided with grooves that allow the polishing liquid to collect therein.

Regarding the polishing conditions, for example, the rotation speed of the polishing surface plate and carrier is preferably 10 rpm (0.17 s ^-1 ) or more and 500 rpm (8.33 s ^-1 ) or less. The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa).

The method of supplying the polishing composition to the polishing pad is also not particularly limited, and for example, a method of continuously supplying it with a pump or the like may be employed. Although there is no limit to the amount supplied, it is preferable that the surface of the polishing pad is always covered with the polishing composition according to the present invention.

After polishing, the substrate is washed under running water, water droplets adhering to the substrate are removed using a spin dryer, and the substrate is dried to obtain a substrate having a layer containing metal.

Although embodiments of the invention have been described in detail, it is to be understood that this is intended to be illustrative and exemplary, and not restrictive, and that the scope of the invention is to be construed in accordance with the appended claims. It is.

The present invention includes the following aspects and forms.
1. Abrasive grains containing at least one kind of zirconia particles;
A selectivity improver that includes at least one kind of salt consisting of a monovalent anion and a monovalent or higher cation, and improves the ratio of the polishing rate of SiOC to the polishing rate of SiN;
a pH adjuster containing at least one type of acid;
including;
pH is more than 3.0 and less than 7.0,
A polishing composition, wherein the abrasive grains have a positive zeta potential.
2. 1 above, wherein the concentration of the selectivity improver is 50 ppm or more and 1000 ppm or less. The polishing composition described in .
3. The above 1. has a pH of 4.0 or more and 6.0 or less. or 2. The polishing composition described in .
4. The pH adjuster includes acetic acid, as described in 1. above. ~3 above. The polishing composition according to any one of the above.
5. The selectivity improver includes ammonium acetate, as described in 1. above. ~4 above. The polishing composition according to any one of the above.
6. 1 above, wherein the content of the abrasive grains is 0.01% by mass or more and 1.0% by mass or less. ~5 above. The polishing composition according to any one of the above.
7. 1. further comprising at least one dispersant selected from the group consisting of sugar alcohols; ~6 above. The polishing composition according to any one of the above.
8. Above 1. ~7 above. A polishing method comprising the step of polishing an object to be polished containing SiOC and SiN using the polishing composition according to any one of the above.
9. A semiconductor substrate containing SiOC and SiN is prepared in 8. above. A method for manufacturing a semiconductor substrate, comprising the step of polishing by the polishing method described in .

The present invention will be explained in further detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. In addition, unless otherwise specified, "%" and "parts" mean "mass %" and "mass parts", respectively.

[Methods for measuring various physical properties]
In this example, various physical properties were measured by the following methods.

<Measurement of particle diameter (D50)>
For the D50 value of the zirconia particles, a value measured as a volume average particle diameter was adopted by a dynamic light scattering method using a particle size distribution measuring device (Nanotrac UPA-UT151, manufactured by Microtrac Bell Co., Ltd.). More specifically, a dispersion of zirconia particles in water was used to measure the particle diameter of the zirconia particles. By analysis using a measuring device, the particle diameter (D50) when the cumulative particle volume from the fine particle side reaches 50% of the total particle volume in the particle size distribution of the zirconia particles was calculated.

<Measurement of zeta potential>
The zeta potential of the zirconia particles was measured using a zeta potential measuring device manufactured by Malvern Panalytical (trade name: "Zetasizer Nano ZSP").

<Measurement of pH>
The pH of the polishing composition was measured using a pH meter (manufactured by Horiba, Ltd., model number: F-71).

[Preparation of polishing composition]
(Example 1)
Colloidal zirconia (manufactured by Dai-ichi Kigenso Kagaku Kogyo Co., Ltd., ZSL-20N (ZrO ₂ sol)) was used as the abrasive grain at a final concentration of 0.10% by mass, and ammonium acetate was used as a selectivity improver at a final concentration of 50 ppm. Each was added to pure water as a dispersion medium at room temperature (25°C) so that the concentration would be the same.Furthermore, BIT (1, 2-Benzisothiazol-3(2H)-one (manufactured by San-Ai Sekiyu Co., Ltd.) was added to obtain a mixed solution.Acetic acid was added to the obtained mixed solution as a pH adjuster to adjust the pH to 5.0. In addition, the polishing composition was prepared by stirring and mixing at room temperature (25° C.) for 30 minutes.The zeta potential of colloidal zirconia in the polishing composition obtained was +35 mV. The particle size of the colloidal zirconia was similar to the particle size of the colloidal zirconia described above.

(Example 2)
A polishing composition was prepared in the same manner as in Example 1, except that ammonium acetate was added to pure water to a final concentration of 100 ppm. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 3)
A polishing composition was prepared in the same manner as in Example 1, except that ammonium acetate was added to pure water to a final concentration of 200 ppm. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 4)
A polishing composition was prepared in the same manner as in Example 1, except that ammonium acetate was added to pure water to a final concentration of 500 ppm. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 5)
A polishing composition was prepared in the same manner as in Example 1, except that ammonium acetate was added to pure water to a final concentration of 1000 ppm. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 6)
A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixture so that the pH was 4.0. The zeta potential of colloidal zirconia in the resulting polishing composition was +37 mV.

(Example 7)
A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixture so that the pH was 4.5. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 8)
A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixture so that the pH was 6.0. The zeta potential of colloidal zirconia in the resulting polishing composition was +30 mV.

(Example 9)
A polishing composition was prepared in the same manner as in Example 4, except that ammonium nitrate was used as a selectivity improver instead of ammonium acetate, and nitric acid was used as a pH adjuster instead of acetic acid. . The zeta potential of colloidal zirconia in the resulting polishing composition was +36 mV.

(Example 10)
A polishing composition was prepared in the same manner as in Example 4, except that nitric acid was used as a pH adjuster instead of acetic acid. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 11)
A polishing composition was prepared in the same manner as in Example 4, except that potassium acetate was used as a selectivity improver instead of ammonium acetate. The zeta potential of colloidal zirconia in the resulting polishing composition was +36 mV.

(Example 12)
Colloidal zirconia (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., ZSL-20N (ZrO ₂ sol)) was used as the abrasive grain at a final concentration of 0.10% by mass, and ammonium acetate was used as the selectivity ratio improver at a final concentration of 500 ppm. Sorbitol as a dispersant was added to pure water as a dispersion medium at room temperature (25°C) to a final concentration of 10 ppm.Furthermore, the final concentration was 0.3 g/kg (0.03 mass %) as a fungicidal agent (1,2-benziisothiazol-3(2H)-one, manufactured by San-Ai Sekiyu Co., Ltd.) was added to obtain a mixed solution. Acetic acid was added as an adjusting agent so that the pH was 5.0, and the mixture was stirred for 30 minutes at room temperature (25°C) to prepare a polishing composition. Zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.The particle size of the colloidal zirconia in the polishing composition was the same as the particle size of the colloidal zirconia described above.

(Example 13)
A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 50 ppm. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 14)
A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 80 ppm. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 15)
A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 100 ppm. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 16)
A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 200 ppm. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 17)
A polishing composition was prepared in the same manner as in Example 12, except that sorbitol was added to pure water to a final concentration of 500 ppm. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Example 18)
A polishing composition was prepared in the same manner as in Example 15, except that xylitol was used as a dispersant instead of sorbitol. The zeta potential of colloidal zirconia in the resulting polishing composition was +35 mV.

(Comparative example 1)
A polishing composition was prepared in the same manner as in Example 1, except that no selectivity improver was added and nitric acid was used as a pH adjuster instead of acetic acid. The zeta potential of colloidal zirconia in the resulting polishing composition was +34 mV.

(Comparative example 2)
A polishing composition was prepared in the same manner as in Example 1, except that no selectivity improver was added. The zeta potential of colloidal zirconia in the resulting polishing composition was +36 mV.

(Comparative example 3)
A polishing composition was prepared in the same manner as in Example 4, except that ammonium oxalate monohydrate was used instead of ammonium acetate. The zeta potential of colloidal zirconia in the resulting polishing composition was -32 mV.

(Comparative example 4)
A polishing composition was prepared in the same manner as in Example 4, except that triammonium citrate was used instead of ammonium acetate. The zeta potential of colloidal zirconia in the resulting polishing composition was -39 mV.

(Comparative example 5)
A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixture so that the pH was 3.0. The zeta potential of colloidal zirconia in the resulting polishing composition was +39 mV.

(Comparative example 6)
A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixture so that the pH was 7.0. The zeta potential of the colloidal zirconia in the resulting polishing composition could not be measured because the colloidal zirconia aggregated.

(Comparative example 7)
A polishing composition was prepared in the same manner as in Example 4, except that acetic acid was added to the mixture so that the pH was 8.0. The zeta potential of the colloidal zirconia in the resulting polishing composition could not be measured because the colloidal zirconia aggregated.

(Comparative example 8)
Instead of colloidal zirconia (ZSL-20N), colloidal zirconia (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., ZSL00014 (ZrO ₂ sol), D50 of zirconia particles: 15 nm) was used as an abrasive grain at a final concentration of 1.0% by mass. A polishing composition was prepared in the same manner as in Example 4, except that it was added to pure water so that the following composition was added. The zeta potential of colloidal zirconia in the resulting polishing composition was -23 mV.

(Comparative example 9)
A polishing composition was prepared in the same manner as in Comparative Example 1, except that colloidal silica (D50: 70 nm) with amino groups immobilized on the surface was used as the abrasive grains instead of colloidal zirconia (ZSL-20N). Prepared. The zeta potential of colloidal zirconia in the resulting polishing composition was +24 mV.

(Comparative Example 10)
A polishing composition was prepared in the same manner as in Comparative Example 1, except that colloidal ceria (D50: 70 nm) was used as the abrasive grain in place of colloidal zirconia (ZSL-20N). The zeta potential of colloidal zirconia in the resulting polishing composition was +33 mV.

(Comparative Example 11)
A polishing composition was prepared in the same manner as in Comparative Example 1, except that colloidal alumina (D50: 300 nm) was used as the abrasive instead of colloidal zirconia (ZSL-20N). The zeta potential of colloidal zirconia in the resulting polishing composition was +29 mV.

[Polishing speed]
The objects to be polished (substrates) were a 300 mm wafer ((SiOC film), manufactured by Advance Materials Technology Co., Ltd., product name: BD2x 5kA Blanket), and a 300 mm wafer (SiN (silicon nitride film), manufactured by Advance Materials Technology Co., Ltd.). , product name: LP-SiN 3.5KA Blanket) were prepared.

Using the polishing composition obtained above, each of the prepared substrates was polished under the following polishing conditions, and the polishing rate was measured:
(polishing conditions)
Polishing machine: EJ-380IN-CH (manufactured by Nippon Engis Co., Ltd.)
Polishing pad: Hard polyurethane pad (manufactured by Nitta DuPont Co., Ltd., IC1010)
Polishing pressure: 3.0psi (1psi=6894.76Pa)
Platen (surface plate) rotation speed: 60 rpm
Head (carrier) rotation speed: 60 rpm
Flow rate of polishing composition: 100ml/min
Polishing time: 30 seconds.

(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 rate was evaluated by dividing the difference in film thickness before and after polishing by the polishing time. (See formula below). The polishing rate for SiOC is preferably 1700 Å/min or more, and the polishing rate for SiN is preferably less than 30 Å/min.

(selectivity ratio)
The selectivity was determined by dividing the polishing rate of the SiOC substrate obtained above by the polishing rate of the SiN substrate. The selection ratio is preferably 100 or more.

[Storage stability]
The average secondary particle size (D50) of the zirconia particles in each polishing composition was measured at room temperature by dynamic light scattering using a particle size distribution measuring device (Nanotrac UPA-UT151, manufactured by Microtrac Bell Co., Ltd.). (25°C). In detail, the diameter D50 (nm) of the particle when the cumulative particle volume reaches 50% of the total particle volume from the fine particle side in the particle size distribution of the zirconia particles is calculated by analysis using a measuring device, and this is The average secondary particle diameter ( _D50A ) of zirconia particles is defined as (nm).

Separately, 100 g of each polishing composition was weighed into a plastic bottle. Next, each plastic bottle was placed in a constant temperature bath set at 80°C and left for two weeks. After standing for a predetermined period of time, the average secondary particle diameter (D50 _B ) (nm) of the zirconia particles in each polishing composition is measured in the same manner as above.

Based on the average secondary particle diameters (D50 _A (nm) and D50 _B (nm)) of the zirconia particles before and after standing, the increase rate (%) of the average secondary particle diameter was calculated according to the following formula, and this was calculated as follows: This was used as an indicator of storage stability. Storage stability (increase rate of average secondary particle size) (%) indicates that the smaller the absolute value, the better the storage stability. The absolute value of storage stability (increase rate of average secondary particle size) (%) is acceptable if it is 40% or less, preferably 35% or less, more preferably 25% or less, and 10% or less. %, particularly preferably less than 5%.

The evaluation results of the polishing compositions of each Example and each Comparative Example are shown in Table 1 below. Note that "-" in Table 1 indicates that the agent was not used.

As shown in Table 1, the polishing composition of the example can polish SiOC at a high polishing rate while keeping the polishing rate of SiN low, so the ratio of the polishing rate of SiOC to the polishing rate of SiN is It can be seen that (selectivity ratio) can be improved.

Claims (9)

Abrasive grains containing at least one kind of zirconia particles;
A selectivity improver that includes at least one kind of salt consisting of a monovalent anion and a monovalent or higher cation, and improves the ratio of the polishing rate of SiOC to the polishing rate of SiN;
a pH adjuster containing at least one type of acid;
including;
pH is more than 3.0 and less than 7.0,
A polishing composition, wherein the abrasive grains have a positive zeta potential. The polishing composition according to claim 1, wherein the concentration of the selectivity improver is 50 ppm or more and 1000 ppm or less. The polishing composition according to claim 1, having a pH of 4.0 or more and 6.0 or less. The polishing composition according to claim 1, wherein the pH adjuster includes acetic acid. The polishing composition according to claim 1, wherein the selectivity improver includes ammonium acetate. The polishing composition according to claim 1, wherein the content of the abrasive grains is 0.01% by mass or more and 1.0% by mass or less. The polishing composition according to claim 1, further comprising at least one dispersant selected from the group consisting of sugar alcohols. A polishing method comprising the step of polishing an object to be polished containing SiOC and SiN using the polishing composition according to any one of claims 1 to 7. A method for manufacturing a semiconductor substrate, comprising the step of polishing a semiconductor substrate containing SiOC and SiN by the polishing method according to claim 8.