WO2017047307A1

WO2017047307A1 - Polishing composition

Info

Publication number: WO2017047307A1
Application number: PCT/JP2016/073745
Authority: WO
Inventors: 易民潘
Original assignee: 株式会社フジミインコーポレーテッド
Priority date: 2015-09-15
Filing date: 2016-08-12
Publication date: 2017-03-23
Also published as: TW201726880A; JP6533439B2; TWI683896B; JP2017057263A

Abstract

Provided is a polishing composition in which the ratio of the rate of polishing polysilicon or amorphous silicon to the rate of polishing silicon nitride is high, the rate of polishing polysilicon or amorphous silicon is high, and the rate of polishing silicon nitride is low. The polishing composition comprises abrasive grains, a quaternary ammonium salt having a benzene ring in the structure, and a water-soluble polymer and/or a surfactant. This polishing composition is for use in polishing a work which includes polysilicon and/or amorphous silicon and further includes silicon nitride.

Description

Polishing composition

The present invention relates to a polishing composition.

When the surface of a semiconductor substrate is planarized by chemical mechanical polishing (CMP), a polysilicon film that is relatively easy to polish or a silicon nitride film that is relatively difficult to polish is disposed below the amorphous silicon film. Then, the polysilicon film or the amorphous silicon film may be polished using this silicon nitride film as a stopper layer. In such polishing, it is ideal that the polysilicon film or the amorphous silicon film is polished efficiently and the silicon nitride film is hardly polished.

Accordingly, the polishing composition used for such polishing includes a ratio of the polishing rate of the polysilicon film and the amorphous silicon film to the polishing rate of the silicon nitride film (the polishing rate of the polysilicon film or the amorphous silicon film is changed to the silicon nitride film). Calculated by dividing by the polishing rate of (5), the polishing rate of the polysilicon film and the amorphous silicon film is high, and the polishing rate of the silicon nitride film is required to be close to zero.

For example, Patent Document 1 discloses a polishing composition in which the ratio of the polishing rate of the polysilicon film to the polishing rate of the silicon nitride film is large and the polishing rate of the polysilicon film is high. However, the polishing composition disclosed in Patent Document 1 cannot be said to have a sufficiently low polishing rate for the silicon nitride film. Therefore, after the polishing of the polysilicon film is completed, if the polishing operation is not properly finished, the silicon nitride film as the stopper layer may be polished.

Japanese Patent Publication No. 2004-266155

Therefore, the present invention solves the problems of the prior art as described above, the ratio of the polishing rate of polysilicon and amorphous silicon to the polishing rate of silicon nitride is large, the polishing rate of polysilicon and amorphous silicon is large, and An object of the present invention is to provide a polishing composition having a low polishing rate for silicon nitride.

In order to solve the above problems, a polishing composition according to one embodiment of the present invention is a polishing composition used for polishing a polishing object having at least one of polysilicon and amorphous silicon and silicon nitride, The gist is to contain abrasive grains, a quaternary ammonium salt having a benzene ring in the structure, and at least one of a water-soluble polymer and a surfactant.

The polishing composition of the present invention has a large ratio of the polishing rate of polysilicon and amorphous silicon to the polishing rate of silicon nitride, a high polishing rate of polysilicon and amorphous silicon, and a low polishing rate of silicon nitride.

It is sectional drawing explaining the structure of a silicon wafer.

An embodiment of the present invention will be described in detail below. In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. In addition, various changes or improvements can be added to the present embodiment, and forms to which such changes or improvements are added can also be included in the present invention. For example, in this embodiment, a polishing composition used for polishing a polishing object having polysilicon and silicon nitride will be described. This polishing composition is used for polishing objects having amorphous silicon and silicon nitride. It can also be used for polishing or polishing a polishing object having polysilicon, amorphous silicon, and silicon nitride.

The polishing composition of the present embodiment is a polishing composition used for polishing a polishing object having polysilicon and silicon nitride, and includes abrasive grains and a quaternary ammonium salt having a benzene ring in the structure. And at least one of a water-soluble polymer and a surfactant.
In the polishing composition of this embodiment, the ratio of the polishing rate of polysilicon to the polishing rate of silicon nitride when polished under the same conditions (hereinafter also referred to as “polishing rate ratio”) is large. It has the performance that the polishing rate of polysilicon is high and the polishing rate of silicon nitride is low. If the object to be polished has amorphous silicon, “polysilicon” may be read as “amorphous silicon” (the same applies to the following).

More specifically, since the polishing composition of this embodiment has high hydrolyzability, it is possible to polish polysilicon efficiently. Therefore, if polishing is performed using the polishing composition of the present embodiment, the polishing rate of polysilicon increases. Further, since the cation of the quaternary ammonium salt is adsorbed to the negatively charged silicon nitride, polishing of the silicon nitride is suppressed. Therefore, if polishing is performed using the polishing composition of the present embodiment, the polishing rate of silicon nitride is reduced. Further, since the polishing rate of polysilicon is kept large, the polishing rate ratio becomes large (that is, the polishing selectivity is high), and the polishing rate ratio can be 250 or more.

Therefore, if the polishing object having polysilicon and silicon nitride is polished using the polishing composition of the present embodiment, the polysilicon can be efficiently and selectively polished and removed. Further, since silicon nitride is difficult to polish, even if the polishing operation is not terminated immediately after the polishing of polysilicon is completed, the polishing amount of silicon nitride is small. For example, when a silicon wafer with a film in which a polysilicon film is deposited on a silicon nitride film is an object to be polished, the polysilicon film can be efficiently and selectively polished and removed. Even if the polishing operation is not terminated immediately after the polishing of the polysilicon film is completed, the silicon nitride film as the stopper layer is hardly polished.

Furthermore, the water-soluble polymer has an action of adsorbing to polysilicon and suppressing polishing. When there is a level difference on the surface of the polysilicon, the water-soluble polymer adsorbed on the convex part constituting the level difference is removed by polishing, so that the polishing rate of the polysilicon is maintained, while the high water solubility of the concave part constituting the level difference is maintained. The molecules are not removed and polishing is suppressed. Therefore, when polishing is performed using the polishing composition of the present embodiment, a difference occurs in the polishing rate between the convex portions and the concave portions on the surface of the polysilicon, and as a result, the level difference on the surface of the polysilicon is easily relaxed.
Furthermore, when a nitrogen-containing water-soluble polymer having nitrogen in its structure is used as the water-soluble polymer, the polishing rate of the convex portions is accelerated, and thus particularly excellent step relaxation performance can be obtained. This is because the presence of nitrogen atoms on the surface of the water-soluble polymer adsorbed on the surface of the polysilicon makes the abrasive particles hydrophilic and negatively charged due to the positive charge and hydrophilic action of the nitrogen atoms. This is considered to be because the affinity with the surface of the polysilicon is improved and scraping with abrasive grains is promoted.

Below, the polishing composition of this embodiment is demonstrated in detail.
1. Regarding the polishing object The polishing object applicable to polishing using the polishing composition of the present embodiment is not particularly limited as long as it has polysilicon and silicon nitride. Examples include a film formed with a polysilicon film and a silicon nitride film. The material of the substrate is not particularly limited, and examples thereof include simple silicon, silicon compound, metal, ceramic, and resin.

Examples of the single silicon include single crystal silicon, polysilicon (polycrystalline silicon), and amorphous silicon. Examples of the silicon compound include silicon nitride, silicon dioxide (for example, a silicon dioxide interlayer insulating film formed using tetraethoxysilane (TEOS)), silicon carbide, and the like.
Examples of the metal include tungsten, copper, aluminum, hafnium, cobalt, nickel, titanium, tantalum, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium and the like. These metals may be contained in the form of an alloy or a metal compound.
A specific example of such an object to be polished is a silicon wafer with a film in which a polysilicon film is deposited on a silicon nitride film.

2. About abrasive grains The kind of abrasive grains contained in the polishing composition of the present embodiment is not particularly limited, and may be any of inorganic particles, organic particles, and organic-inorganic composite particles, for example. Specific examples of the inorganic particles include particles made of a metal oxide such as silica, alumina, ceria, and titania, and particles made of ceramic such as silicon nitride, silicon carbide, and boron nitride. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles. These abrasive grains may be used alone or in combination of two or more.

Of these specific examples, silica is preferred. Specific examples of the silica include colloidal silica, fumed silica, sol-gel silica, and the like. Among these silicas, colloidal silica is more preferable, and in the colloidal silica, a cage shape (for example, an ellipse centering on the long axis) is used. The shape of a rotating body obtained by rotating the colloidal silica is more preferable. Furthermore, an organic acid may be immobilized on the surface of the silica. The organic acid is immobilized on the silica by chemically bonding a functional group of the organic acid to the surface of the silica. Examples of organic acids include sulfonic acid, carboxylic acid, sulfinic acid, and phosphonic acid.

The content of abrasive grains in the polishing composition can be 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 1% by mass or more. As the content of the abrasive grains increases, the removal rate (polishing rate) of the object to be polished by the polishing composition is improved.
The content of the abrasive grains in the polishing composition can be 15% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, and particularly preferably. Is 2.3 mass% or less. As the content of the abrasive grains decreases, the material cost of the polishing composition can be reduced, and in addition, the aggregation of the abrasive grains hardly occurs.

The average primary particle diameter of the abrasive grains can be 5 nm or more, preferably 10 nm or more, more preferably 30 nm or more. As the average primary particle diameter of the abrasive grains increases, the polishing rate of the object to be polished by the polishing composition increases.
The average primary particle diameter of the abrasive grains can be 200 nm or less, preferably 100 nm or less, more preferably 50 nm or less. As the average primary particle diameter of the abrasive grains decreases, a surface to be polished with few surface defects is easily obtained by polishing the object to be polished using the polishing composition.

Note that the value of the average primary particle diameter of the abrasive grains can be calculated based on, for example, the specific surface area of the abrasive grains measured by the BET method using nitrogen gas or the like. In the case of non-spherical abrasive grains such as bowl-shaped colloidal silica, the average primary particle diameter of virtual spherical particles is calculated based on the specific surface area of the abrasive grains measured by the BET method. The average primary particle diameter of typical spherical particles is defined as the average primary particle diameter of non-spherical abrasive grains.

3. Quaternary ammonium salt having a benzene ring in the structure The polishing composition of the present embodiment includes a quaternary ammonium salt having a benzene ring in the structure (hereinafter simply referred to as “quaternary ammonium salt”). Is also added). The kind of the quaternary ammonium salt is not particularly limited as long as it has a benzene ring in its structure. For example, the ammonium ion of the quaternary ammonium salt is represented by the following chemical formula 1. can give.
In the following chemical formula 1, x is an integer of 1 to 15, and y, z, and w are each independently an integer of 0 to 4. However, the smaller x, y, z, and w are preferable.

Examples of the quaternary ammonium salt having an ammonium ion represented by the chemical formula 1 include benzyltrimethylammonium chloride, benzyltriethylammonium chloride, benzyltributylammonium chloride represented by the following chemical formulas 2 to 4.

Examples of quaternary ammonium salts having ammonium ions other than those represented by Chemical Formula 1 include benzyldimethyltetradecylammonium chloride hydrate, benzyldimethylphenylammonium chloride represented by Chemical Formulas 5 to 12 below. , Trimethylphenylammonium chloride, triethylphenylammonium chloride, benzethonium chloride, benzoylcholine chloride, benzalkonium chloride, denatonium benzoate and the like.

One of these quaternary ammonium salts may be used alone, or two or more thereof may be used in combination.
The quaternary ammonium salts represented by Chemical Formulas 2 to 12 were salts of ammonium ions and chloride ions or benzoate ions, but ammonium ions and hydroxide ions, fluoride ions, bromide ions, iodine ions. It may be a chloride ion or a salt with an organic acid ion.
Further, in order to improve the ratio of the polishing rate of polysilicon and the polishing rate of polysilicon with respect to the polishing rate of polysilicon and the polishing rate of polysilicon, the ammonium ion of the quaternary ammonium salt is represented by the chemical formula 1 but represented by other chemical formulas. More preferred than the ammonium ion of the quaternary ammonium salt.
Further, as the anion of the quaternary ammonium salt, a hydroxide ion is most preferable from the viewpoint of residual anion on the surface after polishing.

The content of the quaternary ammonium salt in the polishing composition can be 0.0001% by mass or more, preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and still more preferably 0. 0.03 mass% or more. As the content of the quaternary ammonium salt increases, the polishing rate of polysilicon by the polishing composition and the ratio of the polishing rate of polysilicon to the polishing rate of silicon nitride improve.
Moreover, content of the quaternary ammonium salt in polishing composition can be 1 mass% or less, Preferably it is 0.5 mass% or less, More preferably, it is 0.3 mass% or less. Thereby, the outstanding level | step difference mitigation performance is obtained.

4). About Water-Soluble Polymer At least one of a water-soluble polymer and a surfactant is added to the polishing composition of this embodiment. The type of the water-soluble polymer is not particularly limited, and examples thereof include celluloses such as methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, and carboxymethyl hydroxyethyl cellulose. And polysaccharides such as chitosan, and polymers such as polyethylene glycol, polyethyleneimine, poly-N-vinylpyrrolidone, polyvinyl alcohol, polyacrylic acid (or a salt thereof), polyacrylamide, and polyethylene oxide. These water-soluble polymers may be used alone or in combination of two or more.

Among these water-soluble polymers, nitrogen-containing water-soluble polymers having nitrogen in their structure are preferable. The number of nitrogen atoms contained in the nitrogen-containing water-soluble polymer monomer may be one or more. Further, the nitrogen-containing water-soluble polymer may have a nitrogen atom in the main chain, or may have a nitrogen atom in the side chain. Furthermore, the nitrogen-containing water-soluble polymer may have a nitrogen atom as an amino group, imino group, amide group, imide group, carbodiimide group, hydrazide group, or urethane group.

Furthermore, the nitrogen-containing water-soluble polymer may have a nitrogen atom as a salt (for example, an ammonium salt) formed from a nitrogen cation and another anion. Examples of the nitrogen-containing water-soluble polymer having a salt structure include polycondensation polyamide such as water-soluble nylon, polycondensation polyester such as water-soluble polyester, polyaddition polyamine, polyaddition polyimine, polyaddition ( Examples thereof include meth) acrylamide, a water-soluble polymer having a nitrogen atom in at least a part of the alkyl main chain, and a water-soluble polymer having a nitrogen atom in at least a part of the side chain.

Specific examples of the polyaddition type nitrogen-containing water-soluble polymer include polyvinyl imidazole, polyvinyl carbazole, poly-N-vinyl pyrrolidone, polyvinyl caprolactam, and polyvinyl piperidine. Further, the nitrogen-containing water-soluble polymer may have a partially hydrophilic structure such as a vinyl alcohol structure, a methacrylic acid structure, a vinyl sulfonic acid structure, a vinyl alcohol carboxylic acid ester structure, or an oxyalkylene structure. Good. Moreover, the polymer which has multiple types of structures, such as these diblock type | molds, a triblock type | mold, a random type | mold, and an alternating type | mold, may be sufficient.

Further, the nitrogen-containing water-soluble polymer may be one having a cation in part or all of the molecule, one having an anion, one having both an anion and a cation, and one having a nonion.
Of these nitrogen-containing water-soluble polymers, poly-N-vinylpyrrolidone, polyethyleneimine, and polyacrylamide are more preferable.

The weight average molecular weight of the water-soluble polymer can be 5000 or more, preferably 10,000 or more, more preferably 30000 or more, and further preferably 40000 or more. Thereby, the ratio of the polishing rate of polysilicon by the polishing composition and the polishing rate of polysilicon with respect to the polishing rate of silicon nitride is improved.
Moreover, the weight average molecular weight of water-soluble polymer can be 3 million or less, Preferably it is 1 million or less, More preferably, it is 100,000 or less, More preferably, it is 60,000 or less. Thereby, the outstanding level | step difference mitigation performance is obtained.

Furthermore, the content of the water-soluble polymer in the polishing composition can be 0.0001% by mass or more, preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and still more preferably. It is 0.03 mass% or more. Thereby, the outstanding level | step difference mitigation performance is obtained.
Furthermore, the content of the water-soluble polymer in the polishing composition can be 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and still more preferably 0%. .1% by mass or less. Thereby, the ratio of the polishing rate of polysilicon by the polishing composition and the polishing rate of polysilicon with respect to the polishing rate of silicon nitride is improved.

Furthermore, the ratio of the content of the water-soluble polymer and the content of the abrasive grains in the polishing composition ([abrasive grain content] / [water-soluble polymer content]) should be 250 or less. Preferably, it is 150 or less, More preferably, it is 100 or less, More preferably, it is 50 or less.
Further, the ratio between the content of the water-soluble polymer and the content of the quaternary ammonium salt in the polishing composition ([quaternary ammonium salt content] / [water-soluble polymer content]) is 1 or more, preferably 2 or more.

5). Surfactant At least one of a water-soluble polymer and a surfactant is added to the polishing composition of the present embodiment. As the surfactant, any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant can be used.
Specific examples of the anionic surfactant include polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfuric acid ester, alkyl sulfuric acid ester, polyoxyethylene alkyl sulfuric acid, alkyl sulfuric acid, alkylbenzene sulfonic acid, alkyl phosphoric acid ester, polyoxyethylene Examples thereof include ethylene alkyl phosphate ester, polyoxyethylene sulfosuccinic acid, alkyl sulfosuccinic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether disulfonic acid, and salts thereof (for example, ammonium lauryl sulfate).

Specific examples of the cationic surfactant include alkyl trimethyl ammonium salt, alkyl dimethyl ammonium salt, alkyl benzyl dimethyl ammonium salt, and alkyl amine salt.
Furthermore, specific examples of amphoteric surfactants include alkyl betaines and alkyl amine oxides.

Furthermore, specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, and alkylalkanolamide. can give.
These surfactants may be used individually by 1 type, and may be used in combination of 2 or more type.

6). About other additives In order to improve the performance of the polishing composition of the present embodiment, a known additive contained in a general polishing composition may be further added as necessary. Good. For example, various additives such as a pH adjuster, an oxidizing agent, an anticorrosive, a chelating agent, a dispersion aid, an antiseptic, and an antifungal agent may be added.

6-1 About pH adjuster A pH adjuster may be added to the polishing composition of the present embodiment, if necessary, in order to adjust the pH to a desired value. The pH adjuster used may be either acid or alkali, and may be either an inorganic compound or an organic compound. As the pH adjuster, for example, nitric acid, phosphoric acid, hydrochloric acid, sulfuric acid, citric acid and the like can be used.
The pH of the polishing composition of the present embodiment is not particularly limited, but may be 7 or more and 11 or less.

6-2 Oxidizing agent An oxidizing agent may be added to the polishing composition of the present embodiment, if necessary, in order to oxidize the surface of the object to be polished. The oxidizing agent has an action of oxidizing the surface of the object to be polished, and when an oxidizing agent is added to the polishing composition, there is an effect of improving the polishing rate by the polishing composition.
An oxidizing agent that can be used is, for example, a peroxide. Specific examples of the peroxide include hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, perchloric acid, persulfate (for example, sodium persulfate, potassium persulfate, ammonium persulfate) and the like.

6-3 Anticorrosive Agent An anticorrosive agent may be added to the polishing composition of the present embodiment as necessary in order to suppress corrosion of the surface of the object to be polished. Specific examples of the anticorrosive include amines, pyridines, tetraphenylphosphonium salts, benzotriazoles, triazoles, tetrazoles, benzoic acid and the like.

6-4 Chelating Agent In the polishing composition of this embodiment, the metal contamination of the polishing object is suppressed by capturing metal impurity components in the polishing system to form a complex. A chelating agent may be added. Specific examples of the chelating agent include carboxylic acid, amine, organic phosphonic acid, amino acid and the like.

6-5 About Dispersion Aid To the polishing composition of the present embodiment, a dispersion aid may be added as necessary in order to facilitate redispersion of the aggregate of abrasive grains. Specific examples of the dispersion aid include condensed phosphates such as pyrophosphate and hexametaphosphate.

6-6 Preservative and Antifungal Agent An antiseptic and an antifungal agent may be added to the polishing composition of the present embodiment as necessary. Examples of antiseptics and fungicides include isothiazoline-based antiseptics such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, and paraoxybenzoic acid esters. And phenoxyethanol.

7). About a liquid medium The polishing composition of this embodiment may contain liquid media, such as water and an organic solvent. The liquid medium is a dispersion medium for dispersing or dissolving each component of the polishing composition (abrasive grains, quaternary ammonium salt having a benzene ring in the structure, water-soluble polymer, surfactant, additive, etc.). Or it functions as a solvent.

Examples of the liquid medium include water and organic solvents, and one kind can be used alone, or two or more kinds can be mixed and used, but preferably contains water. However, it is preferable to use water containing as little impurities as possible from the viewpoint of suppressing the inhibition of the action of each component. Specifically, pure water, ultrapure water, or distilled water from which foreign substances are removed through a filter after removing impurity ions with an ion exchange resin is preferable.

8). About the manufacturing method of polishing composition The manufacturing method of the polishing composition of this embodiment is not specifically limited, For example, an abrasive grain, a quaternary ammonium salt, water-soluble polymer, and surfactant At least one and optionally various additives can be produced by stirring and mixing in a liquid medium such as water. Although the temperature at the time of mixing is not specifically limited, 10 to 40 degreeC is preferable and you may heat in order to improve a dissolution rate. Further, the mixing time is not particularly limited.

9. Polishing method of polishing object The method and conditions for polishing the polishing object using the polishing composition of the present embodiment are not particularly limited, and the polishing object is within the range of general polishing methods and conditions. Polishing may be performed by appropriately selecting a method and conditions suitable for polishing an object. For example, a polishing composition is interposed between a polishing object (for example, a silicon wafer with a film in which a polysilicon film is deposited on a silicon nitride film) and a polishing pad, and a polishing apparatus (single-side polishing apparatus, double-side polishing) The object to be polished can be polished by polishing under general polishing conditions using an apparatus or the like.

For example, when a silicon wafer with a film in which a polysilicon film is deposited on a silicon nitride film is an object to be polished and is polished using a single-side polishing apparatus, the silicon wafer is held using a holder called a carrier. The surface of the silicon wafer is polished by rotating the surface plate while supplying the polishing composition by pressing the surface plate with the polishing pad affixed to the surface of the silicon wafer.
In addition, when polishing a silicon wafer using a double-side polishing apparatus, the silicon wafer is held using a holder called a carrier, and a surface plate with a polishing pad attached from both sides of the silicon wafer to both sides of the silicon wafer. Each surface of the silicon wafer is polished by rotating the surface plates on both sides while supplying the polishing composition.

The kind of the polishing pad is not particularly limited, and may be a foam or a non-foam such as a cloth or a non-woven fabric, and a general non-woven fabric, a polyurethane foam, a porous fluororesin, or the like can be used. Further, the polishing pad may be subjected to groove processing for forming a groove in which the polishing composition is accumulated. Polishing pad materials include polyurethane, acrylic, polyester, acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly-4-methylpentene, cellulose, cellulose ester, polyamide (nylon, aramid, etc.), polyimide, polyimide Resins such as amides, polysiloxane copolymers, oxirane compounds, phenol resins, polystyrenes, polycarbonates, and epoxy resins can be used.

Note that the polishing composition of the present embodiment can be recovered after being used for polishing the polishing object and reused for polishing the polishing object. As an example of the method of reusing the polishing composition, there is a method in which the polishing composition discharged from the polishing apparatus is collected in a tank and is circulated again into the polishing apparatus to be used for polishing. If the polishing composition is circulated, the amount of the polishing composition discharged as a waste liquid can be reduced, so that the environmental load can be reduced. Moreover, since the quantity of the polishing composition to be used can be reduced, the manufacturing cost required for grinding | polishing of a grinding | polishing target object can be suppressed.

When reusing the polishing composition of the present embodiment, the abrasive grains consumed, lost due to use in polishing, quaternary ammonium salts, water-soluble polymers, surfactants, additives, etc. It is good to reuse after adding a part or all as a composition regulator. As a composition regulator, what mixed abrasive grain, a quaternary ammonium salt, water-soluble polymer, surfactant, an additive, etc. by arbitrary mixing ratios can be used. By additionally adding a composition adjusting agent, the polishing composition is adjusted to a composition suitable for reuse and suitable polishing can be performed. Concentrations of abrasive grains, quaternary ammonium salts, water-soluble polymers, surfactants, and additives contained in the composition modifier are arbitrary and are not particularly limited, and are appropriately adjusted according to the size of the tank and polishing conditions. do it.

Further, the polishing composition of the present embodiment may be a one-component type, or a multi-component type such as a two-component type in which a part or all of the components of the polishing composition are mixed in an arbitrary ratio. Also good. Furthermore, the polishing composition of this embodiment may be used for polishing as it is, but a diluted composition obtained by diluting the stock solution with a liquid medium such as water may be used for polishing. .

〔Example〕
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
Example 1
Abrasive grains, a quaternary ammonium salt, a water-soluble polymer, and water were mixed to produce a polishing composition (see Table 1). The abrasive grains are bowl-shaped colloidal silica having an average primary particle diameter of 35 nm, and the concentration of the abrasive grains in the polishing composition is 2.0% by mass. The quaternary ammonium salt is benzyltrimethylammonium hydroxide (hereinafter referred to as “BTMAH”), and the concentration of BTMAH in the polishing composition is 0.05 mass%. The water-soluble polymer is poly-N-vinylpyrrolidone (hereinafter referred to as “PVP”) having a weight average molecular weight (Mw) of 45000, and the concentration of PVP in the polishing composition is 0.02% by mass. Moreover, pH of this polishing composition was 10.0.

(Examples 2 to 9)
Polishing composition in the same manner as in Example 1 except that the abrasive grains, BTMAH and PVP in the polishing composition, and the weight average molecular weight (Mw) of PVP were as shown in Table 1. Manufactured. The pH of these polishing compositions was as shown in Table 1.

(Example 10)
Except for using polyvinyl methyl ketone (hereinafter referred to as “PVMK”) having a weight average molecular weight of 500,000 instead of PVP as the water-soluble polymer, and setting the concentration of PVMK in the polishing composition to 0.05 mass%. A polishing composition was produced in the same manner as in Example 2. The polishing composition had a pH of 10.0.

(Example 11)
As a water-soluble polymer, a methyl vinyl ether / maleic anhydride alternating copolymer (hereinafter referred to as “PMVEMA”) having a weight average molecular weight of 216000 is used instead of PVP, and the concentration of PMVEMA in the polishing composition is 0.05 mass%. A polishing composition was produced in the same manner as in Example 2 except that. The polishing composition had a pH of 10.0.

Example 12
In this example, a surfactant is used in place of the water-soluble polymer. Example 2 was used except that a surfactant, ammonium lauryl sulfate (hereinafter referred to as “ALS”), was used instead of the water-soluble polymer, and the concentration of ALS in the polishing composition was 0.10% by mass. A polishing composition was produced in the same manner. The polishing composition had a pH of 10.0.

(Comparative Example 1)
Example 2 except that trimethylammonium hydroxide (hereinafter referred to as “TMAH”) was used instead of BTMAH as the quaternary ammonium salt, and the concentration of TMAH in the polishing composition was 0.07 mass%. A polishing composition was produced in the same manner. The polishing composition had a pH of 10.4.

(Comparative Example 2)
Example 4 except that triethylammonium hydroxide (hereinafter referred to as “TEAH”) was used as the quaternary ammonium salt instead of BTMAH, and the concentration of TEAH in the polishing composition was 0.08 mass%. A polishing composition was produced in the same manner. The polishing composition had a pH of 10.2.

(Comparative Example 3)
Example 4 except that tributylammonium hydroxide (hereinafter referred to as “TBAH”) was used as the quaternary ammonium salt instead of BTMAH, and the concentration of TBAH in the polishing composition was 0.12 mass%. A polishing composition was produced in the same manner. The polishing composition had a pH of 10.1.

(Comparative Example 4)
A polishing composition was produced in the same manner as in Example 2, except that ammonia was used as the base instead of the quaternary ammonium salt, and the concentration of ammonia in the polishing composition was 0.07% by mass. The polishing composition had a pH of 10.0.

(Comparative Example 5)
A polishing composition was produced in the same manner as in Example 4, except that ammonia was used as the base instead of the quaternary ammonium salt, and the concentration of ammonia in the polishing composition was 0.07% by mass. The polishing composition had a pH of 10.0.

(Comparative Example 6)
A polishing composition was produced in the same manner as in Example 6, except that ammonia was used as the base instead of the quaternary ammonium salt, and the concentration of ammonia in the polishing composition was 0.07% by mass. The polishing composition had a pH of 10.0.

(Comparative Example 7)
A polishing composition was produced in the same manner as in Example 10, except that ammonia was used as the base instead of the quaternary ammonium salt, and the concentration of ammonia in the polishing composition was 0.07% by mass. The polishing composition had a pH of 10.0.

(Comparative Example 8)
A polishing composition was produced in the same manner as in Example 11, except that ammonia was used as the base instead of the quaternary ammonium salt, and the concentration of ammonia in the polishing composition was 0.07% by mass. The polishing composition had a pH of 10.0.

(Comparative Example 9)
Instead of quaternary ammonium salt, ammonia is used as a base, the concentration of ammonia in the polishing composition is 0.07 mass%, and polyvinyl alcohol having a weight average molecular weight of 40000 instead of PVP as a water-soluble polymer (Hereinafter referred to as “PVA”), a polishing composition was produced in the same manner as in Example 2 except that the concentration of PVA in the polishing composition was 0.10% by mass. The polishing composition had a pH of 10.0.

(Comparative Example 10)
Hydroxyethyl cellulose having a weight average molecular weight of 250,000 instead of PVP as the water-soluble polymer, using ammonia as the base instead of the quaternary ammonium salt and setting the ammonia concentration in the polishing composition to 0.07% by mass. (Hereinafter referred to as “HEC”), and a polishing composition was produced in the same manner as in Example 2 except that the concentration of HEC in the polishing composition was 0.04 mass%. The polishing composition had a pH of 10.0.

(Comparative Example 11)
Instead of the quaternary ammonium salt, ammonia was used as the base, the concentration of ammonia in the polishing composition was 0.07% by mass, and the water-soluble polymer was polyoxy having a weight average molecular weight of 1100 instead of PVP. Except that ethylene (3) polyoxypropylene (17) glycol (hereinafter referred to as “POEPOP”) was used and the concentration of POEPOP in the polishing composition was 0.10% by mass, the same as in Example 2 A polishing composition was produced. The polishing composition had a pH of 10.0.
In addition, “(3)” of polyoxyethylene (3) polyoxypropylene (17) glycol means that the average number of repeating oxyethylene units is 3. Similarly, “(17)” means that the average number of repeating oxypropylene units is 17.

(Comparative Example 12)
A polishing composition was produced in the same manner as in Example 12, except that ammonia was used as the base in place of the quaternary ammonium salt, and the concentration of ammonia in the polishing composition was 0.07% by mass. The polishing composition had a pH of 10.0.

Next, the polishing object was polished using these polishing compositions. First, a silicon wafer (manufactured by SVM) having a polysilicon film on the surface and a silicon wafer (manufactured by SVM) having a silicon nitride film on the surface are polished, and polishing is performed under the same polishing method and polishing conditions. The polishing rates of polysilicon and silicon nitride were calculated. Then, the ratio of the polishing rate of polysilicon to the polishing rate of silicon nitride (polishing rate ratio) was calculated from the calculated polishing rate of polysilicon and the polishing rate of silicon nitride.

The values of each polishing rate and polishing rate ratio are shown in Table 1. The polishing rate was calculated by dividing the difference in film thickness before and after polishing the polysilicon film or silicon nitride film of the silicon wafer by the polishing time. Therefore, the unit of the polishing rate is nm / min. The film thickness of the polysilicon film or silicon nitride film was measured using a film thickness measuring device ASET-F5x (trade name) manufactured by KLA-Tencor Corporation.

The polishing conditions are as follows.
Polishing equipment: CMP equipment F-REX300E (trade name) manufactured by Ebara Manufacturing Co., Ltd.
Polishing pad: Polishing pad IC1010 (trade name) manufactured by Dow Electronic Materials
Polishing load: 10.3 kPa
Surface plate rotation speed: 60 rpm
Carrier rotation speed: 65rpm
Polishing time: 1 minute Supply rate of the polishing composition: 300 mL / min (using flowing)

Next, the silicon wafer on which the wiring was formed (see FIG. 1) was used as an object to be polished, and polishing was performed using the polishing compositions of Examples 1 to 12 and Comparative Examples 1 to 12, respectively. First, the configuration of a silicon wafer that is an object to be polished will be described with reference to FIG. This silicon wafer is a 300 mm diameter wafer manufactured by Advanced Material Technology Co., Ltd., and is obtained by forming a silicon oxide film 2, a silicon nitride film 3, and a polysilicon film 4 on a silicon substrate 1.

More specifically, a silicon oxide film 2 (thickness 12.5 nm) is formed on a silicon substrate 1 by thermal oxidation, and further a silicon nitride film 3 (by a low pressure chemical vapor deposition method) is formed on the silicon oxide film 2 ( A film thickness of 70.0 nm) is formed. The silicon oxide film 2 and the silicon nitride film 3 are partially removed to form a plurality of trenches (minimum width 0.18 μm). Furthermore, a polysilicon film 4 (film thickness 152.5 nm) is deposited on the silicon nitride film 3, and the trench is also filled with polysilicon.

A step (step) 4a is formed in the upper portion of the trench on the surface of the silicon wafer (the surface of the polysilicon film 4). The step height of the step 4a is 70 nm. Then, the surface of the silicon wafer was polished using the polishing compositions of Examples 1 to 12 and Comparative Examples 1 to 12, and the step height of the step 4a remaining after polishing was measured.

The polishing conditions are as follows.
Polishing equipment: Wrapping equipment EJ-380IN (trade name) manufactured by Engis Japan
Polishing pad: Polishing pad IC1010 (trade name) manufactured by Dow Electronic Materials
Polishing load: 6.9 kPa
Surface plate rotation speed: 70 rpm
Polishing time: 1 minute Supply rate of the polishing composition: 100 mL / min (using pouring)

In addition, for the measurement of the step height, a high-resolution surface topography profiling system HRP340 (trade name) manufactured by KLA-Tencor Corporation was used. The results are shown in Table 1. In Table 1, when the step height of the step 4a remaining after polishing is less than 8 nm, “A”, when the step height is 8 nm or more and less than 12 nm, “B”, when it exceeds 12 nm, “C”. ".

As can be seen from Table 1, in the polishing using the polishing compositions of Examples 1 to 12, the polishing rate ratio was large, the polishing rate of polysilicon was high, and the polishing rate of silicon nitride was low. Further, the step height was A or B, and the step 4a remaining after polishing was small.
On the other hand, in the polishing using the polishing compositions of Comparative Examples 1 to 12, although the polysilicon polishing rate is high and the silicon nitride polishing rate is low, the polishing rate ratio is small. , Less than 250. Some step heights were A or B, but some were C (the step 4a remaining after polishing was large).

1 silicon substrate 2 silicon oxide film 3 silicon nitride film 4 polysilicon film 4a step

Claims

A polishing composition used for polishing a polishing object having at least one of polysilicon and amorphous silicon and silicon nitride, comprising abrasive grains, a quaternary ammonium salt having a benzene ring in its structure, and water-soluble A polishing composition comprising at least one of a polymer and a surfactant.
The polishing composition according to claim 1, wherein the water-soluble polymer is a nitrogen-containing water-soluble polymer.
The ammonium ion of the quaternary ammonium salt is represented by the following chemical formula 1, wherein x in the following chemical formula 1 is an integer of 1 to 15, and y, z, and w are each independently 0 or more. The polishing composition according to claim 1, wherein the polishing composition is an integer of 4 or less.