JPWO2008117593A1 - Chemical mechanical polishing aqueous dispersion and semiconductor device chemical mechanical polishing method - Google Patents

Abstract

The chemical mechanical polishing aqueous dispersion according to the present invention has (A) an average particle diameter calculated from a specific surface area measured using the BET method, colloidal silica of 10 nm to 50 nm, (B) phosphoric acid, (C) Polyethyleneimine and (D) the quaternary ammonium compound shown by following General formula (1) are included, and pH is 3-5. (In the formula (1), R1 to R4 each independently represents a hydrocarbon group. M- represents an anion.)

Description

  The present invention relates to an aqueous dispersion for chemical mechanical polishing and a chemical mechanical polishing method for a semiconductor device using the same.

  In a conventional semiconductor element isolation process, the silicon oxide film formed on the silicon nitride film is removed by chemical mechanical polishing (hereinafter also referred to as “CMP”), and the silicon nitride film is dissolved by hot phosphoric acid and etched. The method is used. However, in the method of etching by dissolving the silicon nitride film with hot phosphoric acid, the etching process is controlled by time, so that a residual film may be generated or the lower layer of the silicon nitride film may be damaged. Therefore, it has been desired to remove the silicon nitride film by CMP.

  In order to simultaneously remove the silicon oxide film and the silicon nitride film by CMP, it is necessary to make the polishing rate ratio substantially equal. That is, the silicon oxide film is dished or eroded by setting the polishing rate ratio of the silicon nitride film to the silicon oxide film (hereinafter also simply referred to as “polishing rate ratio”) to 0.7 to 1.1. And can be polished flat. For example, JP-A-11-176773, JP-A-2001-7061, JP-A-2001-35820, JP-A-2002-190458, and JP-A-2004-269577 deal with such problems. Discloses an aqueous dispersion for chemical mechanical polishing in which the polishing rate ratio is controlled.

  In actual chemical mechanical polishing, the substrate embedded with silicon nitride film and silicon oxide film is pressed against the polishing cloth affixed on the surface plate and fixed, and an aqueous dispersion for chemical mechanical polishing is supplied onto the polishing cloth. However, this can be achieved by relatively moving the substrate and the surface plate. However, if the pressure from the substrate or the platen or the number of rotations thereof is changed during polishing, there is a problem that it is difficult to maintain the polishing rate ratio at 0.7 to 1.1. The chemical mechanical polishing aqueous dispersion disclosed in the above-mentioned patent document is also not practical because the polishing rate ratio cannot be sufficiently controlled.

  An object of the present invention is to provide an aqueous dispersion for chemical mechanical polishing capable of maintaining the polishing rate ratio of silicon oxide film and silicon nitride film substantially equal and maintaining the polishing rate ratio during polishing, and a chemical machine for a semiconductor device using the same. It is to provide a polishing method.

  The chemical mechanical polishing aqueous dispersion according to the present invention has (A) an average particle diameter calculated from a specific surface area measured using the BET method, colloidal silica of 10 nm to 50 nm, (B) phosphoric acid, (C) Polyethyleneimine and (D) the quaternary ammonium compound shown by following General formula (1) are included, and pH is 3-5.

(In formula (1), R ₁ to R ₄ each independently represent a hydrocarbon group. M ⁻ represents an anion.)
In the chemical mechanical polishing aqueous dispersion according to the invention, the mass ratio (C) / (A) of the component (A) to the component (C) may be 0.001 to 0.05.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the mass ratio (C) / (B) between the component (B) and the component (C) may be 0.002 to 0.2.

  In the chemical mechanical polishing aqueous dispersion according to the invention, the number average molecular weight of the component (C) may be 100 to 2,000.

  The chemical mechanical polishing aqueous dispersion according to the present invention may further contain at least one organic acid selected from tartaric acid, malic acid and citric acid.

  In the chemical mechanical polishing aqueous dispersion according to the present invention, the ratio (Rmax / Rmin) of the major axis (Rmax) and minor axis (Rmin) of the colloidal silica particles of the component (A) is greater than 1.2. be able to.

  In the chemical mechanical polishing aqueous dispersion according to the present invention, the polishing rate ratio (silicon nitride film / silicon oxide film) between the silicon nitride film and the silicon oxide film can be 0.9 or more and 1.1 or less.

  The chemical mechanical polishing aqueous dispersion according to the present invention can be used for polishing a surface to be polished of a semiconductor device in which a silicon nitride film and a silicon oxide film coexist.

  The chemical mechanical polishing method for a semiconductor device according to the present invention uses the above chemical mechanical polishing aqueous dispersion to polish a surface to be polished on which a silicon oxide film and a silicon nitride film coexist, and polishes with the silicon oxide film. It is characterized by being stopped.

  According to the above chemical mechanical polishing aqueous dispersion, the polishing rates of the silicon oxide film and the silicon nitride film can be made substantially equal. Further, the polishing rate ratio can be maintained even during polishing. Accordingly, in the CMP process in which the silicon oxide film and the silicon nitride film are simultaneously polished, the silicon oxide film and the silicon nitride film can be polished while suppressing the occurrence of dishing or erosion of the silicon oxide film.

  In this specification, the polishing rate ratio between the silicon oxide film and the silicon nitride film is “approximately equal” means that the polishing rate ratio of the silicon nitride film to the silicon oxide film is 0.7 to 1.1, preferably 0. It is within the range of 9 to 1.1.

  For example, there is a process in which a silicon oxide film and a silicon nitride film must be polished at the same time and a top surface portion of the silicon nitride film must be completely removed during a gate electrode forming process which is a part of a thin film transistor forming process. When the chemical mechanical polishing aqueous dispersion according to the present invention is applied to such a process, the effect is particularly exerted.

It is the conceptual diagram which showed typically the major axis and minor axis of colloidal silica particle. It is the conceptual diagram which showed typically the major axis and minor axis of colloidal silica particle. It is the conceptual diagram which showed typically the major axis and minor axis of colloidal silica particle. It is sectional drawing which showed typically the to-be-processed object used for the chemical mechanical polishing process of a 1st specific example. It is sectional drawing which showed typically the chemical mechanical polishing process of the 1st specific example. It is sectional drawing which showed typically the chemical mechanical polishing process of the 1st specific example. It is sectional drawing which showed typically the to-be-processed object used for the 1st experiment example. It is sectional drawing which showed typically the chemical mechanical polishing process of the 1st experiment example. It is sectional drawing which showed typically the chemical mechanical polishing process of the 1st experiment example. It is sectional drawing which showed typically the to-be-processed object used for the 2nd experiment example. It is sectional drawing which showed typically the chemical mechanical polishing process of the 2nd experiment example. It is sectional drawing which showed typically the chemical mechanical polishing process of the 2nd experiment example.

  Hereinafter, preferred embodiments of the present invention will be described.

  In addition, this invention is not limited to the following embodiment, Various modifications implemented in the range which does not change the summary of this invention are also included.

1. Chemical mechanical polishing aqueous dispersion The chemical mechanical polishing aqueous dispersion according to this embodiment comprises (A) colloidal silica having an average particle size calculated from a specific surface area measured using the BET method of 10 nm to 50 nm. , (B) phosphoric acid, (C) polyethyleneimine, and (D) a quaternary ammonium compound represented by the following general formula (1), and the pH is 3-5.

(In formula (1), R ₁ to R ₄ each independently represent a hydrocarbon group. M ⁻ represents an anion.)
Hereinafter, each component contained in the chemical mechanical polishing aqueous dispersion according to this embodiment will be described in detail.

1.1 (A) Colloidal silica The chemical mechanical polishing aqueous dispersion according to this embodiment includes colloidal silica as abrasive grains. The colloidal silica preferably has an average particle size calculated from a specific surface area measured using the BET method of 10 nm to 50 nm, more preferably 12 nm to 45 nm, and particularly preferably 15 nm to 35 nm. When the average particle size of the colloidal silica is in the range of 10 nm to 50 nm, the storage stability as an aqueous dispersion for chemical mechanical polishing is excellent, so that the performance (such as polishing rate) immediately after preparation can be maintained. If the average particle size of the colloidal silica is less than 10 nm, the polishing rate is too small for any film, which is not practical. On the other hand, when the average particle diameter of colloidal silica exceeds 50 nm, colloidal silica mechanically polishes the silicon oxide film, and the polishing rate of the silicon oxide film becomes too high, thereby causing dishing.

  The average particle diameter of colloidal silica is calculated from the specific surface area measured using the BET method with a flow-type specific surface area automatic measuring device “micrometrics FlowSorb II 2300 (manufactured by Shimadzu Corporation)”, for example.

  Hereinafter, a method for calculating the average particle diameter from the specific surface area of colloidal silica will be described.

Assuming that the shape of the colloidal silica particles is spherical, the diameter of the particles is d (nm) and the specific gravity is ρ (g / cm ³ ). The surface area A of n particles is A = nπd ² . N particles mass N becomes N = ρnπd ^3/6. The specific surface area S is represented by the surface area of all the constituent particles per unit mass of the powder. Then, the specific surface area S of n particles is S = A / N = 6 / ρd. By substituting the specific gravity ρ = 2.2 of colloidal silica into this equation and converting the unit, the following equation (2) can be derived.
Average particle diameter (nm) = 2727 / S (m ² / g) (2)
In addition, all the average particle diameters of the colloidal silica in this specification are calculated based on Formula (2).

  The amount of colloidal silica added is preferably 1 to 5% by mass, more preferably 1.25 to 4% by mass, and particularly preferably 1 with respect to the mass of the chemical mechanical polishing aqueous dispersion in use. 0.5-3 mass%. When the amount of colloidal silica added is less than 1% by mass, a sufficient polishing rate cannot be obtained, which is not practical. On the other hand, if the amount of colloidal silica added exceeds 5% by mass, the polishing rate increases for any film, but defects such as scratches may occur. In addition, the cost may increase and a stable chemical mechanical polishing aqueous dispersion may not be obtained.

  The ratio (Rmax / Rmin) between the major axis (Rmax) and minor axis (Rmin) of the colloidal silica particles is greater than 1.2, preferably 1.3 or more and 3 or less, more preferably 1.4 or more and 2.5 or less. In this case, the polishing rates of the silicon oxide film and the silicon nitride film can be made substantially equal, and the polishing rate ratio can be maintained even during polishing. Accordingly, in the CMP process in which the silicon oxide film and the silicon nitride film are simultaneously polished, the silicon oxide film and the silicon nitride film can be polished while suppressing the occurrence of dishing or erosion of the silicon oxide film.

  Here, the major axis (Rmax) of the colloidal silica particles means the longest distance among the distances connecting the end portions of the images of one independent colloidal silica particle image taken by a transmission electron microscope. means. The short diameter (Rmin) of the colloidal silica particle means the shortest distance among the distances connecting the end portions of the image with respect to one independent colloidal silica particle image taken by a transmission electron microscope. .

  For example, when the image of one independent colloidal silica particle 60a photographed by a transmission electron microscope is elliptical as shown in FIG. 1, the major axis a of the elliptical shape is determined as the major axis (Rmax) of the colloidal silica particle. Then, the minor axis b of the elliptical shape is determined as the minor diameter (Rmin) of the colloidal silica particles. As shown in FIG. 2, when an image of one independent colloidal silica particle 60b photographed by a transmission electron microscope is an aggregate of two particles, the longest distance c connecting the end portions of the image. Is determined as the long diameter (Rmax) of the colloidal silica particles, and the shortest distance d connecting the end portions of the image is determined as the short diameter (Rmin) of the colloidal silica particles. As shown in FIG. 3, when the image of one independent colloidal silica particle 60c photographed by a transmission electron microscope is an aggregate of three or more particles, the longest distance connecting the end portions of the image. e is determined as the long diameter (Rmax) of the colloidal silica particles, and the shortest distance f connecting the end portions of the image is determined as the short diameter (Rmin) of the colloidal silica particles.

  For example, by measuring the major axis (Rmax) and minor axis (Rmin) of 50 colloidal silica particles and calculating the average value of major axis (Rmax) and minor axis (Rmin) by the above-described determination method, And the ratio of the minor axis (Rmax / Rmin) can be calculated.

1.2 (B) Phosphoric acid The chemical mechanical polishing aqueous dispersion according to this embodiment contains phosphoric acid. When phosphoric acid is added, the polishing rate for the silicon nitride film can be increased. This is presumed to be achieved by a synergistic effect of the chemical polishing action of phosphoric acid on the silicon nitride film and the mechanical polishing action of colloidal silica.

  The addition amount of phosphoric acid is preferably 0.1 to 2% by mass, more preferably 0.2 to 1.5% by mass with respect to the mass of the chemical mechanical polishing aqueous dispersion at the time of use, Especially preferably, it is 0.3-1.2 mass%. If the addition amount of phosphoric acid is less than 0.1% by mass, a sufficient polishing rate for the silicon nitride film cannot be obtained, which is not practical. On the other hand, if the addition amount of phosphoric acid exceeds 2% by mass, the polishing rate for the silicon nitride film becomes almost constant, and adding more is not suitable because it only increases the cost.

1.3 (C) Polyethyleneimine The chemical mechanical polishing aqueous dispersion according to this embodiment includes polyethyleneimine. When polyethyleneimine is added, the polishing rate for the silicon oxide film can be increased.

  This mechanism will be described. Polyethyleneimine can be represented by the following general formula (3).

Polyethyleneimine is dissociated in an aqueous solution and exists in an ionized state. That is, —NH ₂ which is a functional group of [—CH ₂ CH ₃ N (CH ₂ CH ₂ NH ₂ ) —] _x receives H ⁺ in water and becomes —NH ₃ ⁺ . On the other hand, the —NH group which is a functional group of [—CH ₂ CH ₂ NH—] _y also receives H ^{+ in} an aqueous solution to become —NH ₂ ⁺ , and both are positively charged.

  At pH 3-5, the silicon oxide film tends to be negatively charged, and the silicon nitride film tends to be positively charged. Polyethyleneimine is preferentially adsorbed on the surface of the silicon oxide film by electrostatic interaction, and positively charges the surface of the silicon oxide film. Colloidal silica is negatively charged at pH 3-5. Then, colloidal silica can be attracted to the surface of the silicon oxide film by interposing polyethyleneimine, so that mechanical polishing of the silicon oxide film can be promoted.

  By the way, it is considered that the positively charged polyethyleneimine exists in a state of being adsorbed on the surface of the negatively charged colloidal silica. However, colloidal silica can prevent the adsorption of polyethyleneimine due to its own Brownian motion or surface irregularities. Accordingly, the polyethyleneimine is present in a state of being uniformly dissolved in the chemical mechanical polishing aqueous dispersion without being adsorbed on the colloidal silica.

  The amount of polyethyleneimine added is preferably 0.001 to 0.1% by mass, more preferably 0.0025 to 0.04% by mass, based on the mass of the chemical mechanical polishing aqueous dispersion at the time of use. It is particularly preferably 0.005 to 0.02% by mass. When the amount of polyethyleneimine added is less than 0.001% by mass, the polishing rate of the silicon oxide film is remarkably reduced, which is not practical. On the other hand, when the addition amount of polyethyleneimine exceeds 0.1% by mass, aggregation of colloidal silica is caused and dispersion stability is affected.

  The molecular weight of polyethyleneimine is preferably 100 to 2,000, more preferably 200 to 1,800, and particularly preferably 300 to 1,200. If the molecular weight is less than 100, the polishing rate of the silicon oxide film cannot be increased even if polyethyleneimine is added. On the other hand, if the molecular weight exceeds 2,000, the storage stability is impaired, so that it cannot be applied.

  In the chemical mechanical polishing aqueous dispersion according to this embodiment, the mass ratio (C) / (A) of (A) colloidal silica and (C) polyethyleneimine is preferably 0.001 to 0.05, and more. Preferably it is 0.002-0.03, Most preferably, it is 0.004-0.02. When the mass ratio is within this range, the polishing rates of the silicon oxide film and the silicon nitride film can be made substantially equal. Thus, the silicon nitride film can be polished while suppressing the occurrence of dishing of the silicon oxide film on the surface to be polished in which the silicon oxide film and the silicon nitride film coexist. If the mass ratio (C) / (A) is less than 0.001, the polishing rate of the silicon oxide film may become too high. On the other hand, if the mass ratio (C) / (A) exceeds 0.05, the colloidal silica may be aggregated and the dispersion stability may be affected. Further, it is not suitable because the polishing rate of both the silicon oxide film and the silicon nitride film becomes small.

  In the chemical mechanical polishing aqueous dispersion according to this embodiment, the mass ratio (C) / (B) of (B) phosphoric acid and (C) polyethyleneimine is preferably 0.002 to 0.2, More preferably, it is 0.003-0.1, Most preferably, it is 0.005-0.08. When the mass ratio is within this range, the polishing rates of the silicon oxide film and the silicon nitride film can be made substantially equal. Thus, the silicon nitride film can be polished while suppressing the occurrence of dishing of the silicon oxide film on the surface to be polished in which the silicon oxide film and the silicon nitride film coexist. When the mass ratio (C) / (B) is less than 0.002, the polishing rate of the silicon oxide film may become too small. On the other hand, if the mass ratio (C) / (B) exceeds 0.2, the colloidal silica may be aggregated and the dispersion stability may be affected. Further, it is not suitable because the polishing rate of both the silicon oxide film and the silicon nitride film becomes small.

1.4 (D) Quaternary ammonium compound The chemical mechanical polishing aqueous dispersion according to this embodiment includes a quaternary ammonium compound represented by the following general formula (1).

(In the formula (1), R ₁ to R ₄ each independently represent a hydrocarbon group. M ⁻ represents an anion.)
The quaternary ammonium compound is used for the purpose of adjusting the pH of the chemical mechanical polishing aqueous dispersion and suppressing the polishing rate for the silicon oxide film.

In the general formula (1), the hydrocarbon group represented by R ₁ to R ₄ may be aliphatic, aromatic, araliphatic, or alicyclic. In addition, aliphatics such as aliphatic and araliphatic may be saturated or unsaturated, and may be linear or branched. Examples of these hydrocarbon groups include linear, branched, and cyclic saturated or unsaturated alkyl groups, aralkyl groups, and aryl groups.

  As the alkyl group, a lower alkyl group having 1 to 6 carbon atoms is usually preferable, and a lower alkyl group having 1 to 4 carbon atoms is particularly preferable. Specifically, for example, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, iso- Pentyl group, sec-pentyl group, tert-pentyl group, neopentyl group, n-hexyl group, iso-hexyl group, sec-hexyl group, tert-hexyl group, cyclopentyl group, cyclohexyl group, vinyl group, n-propenyl group, Examples include iso-propenyl group, n-butenyl group, iso-butenyl group, sec-butenyl group, tert-butenyl group and the like.

  As the aralkyl group, those having 7 to 12 carbon atoms are usually preferred. Specific examples include a benzyl group, a phenethyl group, a phenylpropyl group, a phenylbutyl group, a phenylhexyl group, a methylbenzyl group, a methylphenethyl group, and an ethylbenzyl group.

  As an aryl group, a C6-C14 thing is preferable normally. Specifically, for example, phenyl group, o-tolyl group, m-tolyl group, p-tolyl group, 2,3-xylyl group, 2,4-xylyl group, 2,5-xylyl group, 2,6- Examples include xylyl group, 3,5-xylyl group, naphthyl group, anthryl group and the like.

  The aromatic ring of the aryl group or aralkyl group may have, for example, a lower alkyl group such as a methyl group or an ethyl group, a halogen atom, a nitro group, an amino group, or the like as a substituent.

Examples of the anion represented by M ⁻ include hydroxide ion (OH ⁻ ) and the like.

  Specific examples of the quaternary ammonium compound include the following. Tetramethylammonium hydroxide (TMAH), trimethyl-2-hydroxyethylammonium hydroxide (choline), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, monomethyltriethylammonium hydroxide, hydroxylated Dimethyldiethylammonium hydroxide, trimethylmonoethylammonium hydroxide, monomethyltripropylammonium hydroxide, dimethyldipropylammonium hydroxide, trimethylmonopropylammonium hydroxide, monomethyltributylammonium hydroxide, dimethyldibutylammonium hydroxide, trimethylmonobutylammonium hydroxide , Monoethyltripropylammonium hydroxide, diethyldipropylammonium hydroxide, triethyl hydroxide Nopropylammonium hydroxide, monoethyltributylammonium hydroxide, diethyldibutylammonium hydroxide, triethylmonobutylammonium hydroxide, monopropyltributylammonium hydroxide, dipropyldibutylammonium hydroxide, tripropylmonobutylammonium hydroxide, triethylhydroxide 2-hydroxyethylammonium hydroxide, tripropyl-2-hydroxyethylammonium hydroxide, tributyl-2-hydroxyethylammonium hydroxide, trimethyl-3-hydroxypropylammonium hydroxide, triethyl-3-hydroxypropylammonium hydroxide, trihydroxide hydroxide Propyl-3-hydroxypropylammonium, tributyl-3-hydroxypropylammonium hydroxide, trimethyl-4-hydride hydroxide Xibutylammonium hydroxide, triethyl-4-hydroxybutylammonium hydroxide, tripropyl-4-hydroxybutylammonium hydroxide, tributyl-4-hydroxybutylammonium hydroxide, trimethyl-3-hydroxybutylammonium hydroxide, triethyl-3 hydroxide -Hydroxybutylammonium, tripropyl-3-hydroxybutylammonium hydroxide, tributyl-3-hydroxybutylammonium hydroxide, dimethylethyl-2-hydroxyethylammonium hydroxide, methyldiethyl-2-hydroxyethylammonium hydroxide, hydroxylated Dimethylethyl-3-hydroxypropylammonium, methyldiethyl-3-hydroxypropylammonium hydroxide, dimethylethyl-4-hydroxybutylanhydride Monium, methyldiethyl-4-hydroxybutylammonium hydroxide, dimethylethyl-3-hydroxybutylammonium hydroxide, methyldiethyl-3-hydroxybutylammonium hydroxide, dimethyldi (2-hydroxyethyl) ammonium hydroxide, dimethyldihydroxide ( 3-hydroxypropyl) ammonium hydroxide, dimethyldi (3-hydroxybutyl) ammonium hydroxide, dimethyldi (4-hydroxybutyl) ammonium hydroxide, diethyldi (2-hydroxyethyl) ammonium hydroxide, diethyldi (3-hydroxypropyl) ammonium hydroxide Diethyldi (3-hydroxybutyl) ammonium hydroxide, diethyldi (4-hydroxybutyl) ammonium hydroxide, methylethyldi (2-hydroxyethyl) ammonium hydroxide , Methylethyldi (3-hydroxypropyl) ammonium hydroxide, diethyldi (3-hydroxybutyl) ammonium hydroxide, methylethyldi (4-hydroxybutyl) ammonium hydroxide, methyltri (2-hydroxyethyl) ammonium hydroxide, 2-hydroxyethyl) ammonium, propyltri (2-hydroxyethyl) ammonium hydroxide, butyltri (2-hydroxyethyl) ammonium hydroxide, methyltri (3-hydroxypropyl) ammonium hydroxide, ethyltri (3-hydroxybutyl) Ammonium, methyltri (4-hydroxybutyl) ammonium hydroxide, ethyltri (4-hydroxybutyl) ammonium hydroxide, methyltri (3-hydroxybutyl) ammonium hydroxide Hydroxide ethyltri (3-hydroxybutyl) ammonium. Among these, tetramethylammonium hydroxide (TMAH) is particularly preferable. These quaternary ammonium compounds can be used singly or in combination of two or more.

  The addition amount of the quaternary ammonium compound is preferably 0.1 to 5% by mass, more preferably 0.2 to 4% by mass, with respect to the mass of the chemical mechanical polishing aqueous dispersion at the time of use. Especially preferably, it is 0.3-3 mass%. When the addition amount of the quaternary ammonium compound is less than 0.1% by mass, the polishing rate ratio between the silicon oxide film and the silicon nitride film cannot be adjusted to an appropriate range. On the other hand, if the addition amount of the quaternary ammonium compound exceeds 5% by mass, the surface of the silicon nitride film or the silicon oxide film is damaged, and the surface may become uneven, which is not preferable.

1.5 pH
The pH of the chemical mechanical polishing aqueous dispersion according to this embodiment is 3 or more and 5 or less. When the pH is within this range, the polishing rate of the silicon nitride film can be increased. In addition, there is an advantage that the storage stability as an aqueous dispersion for chemical mechanical polishing is excellent. A more preferable pH range is 3.2 or more and 4.5 or less. If the pH is less than 3, the polishing rate of the silicon nitride film cannot be increased, and the object of the present invention cannot be achieved. On the other hand, when the pH is higher than 5, not only the polishing rate of the silicon nitride film is remarkably lowered, but also the storage stability as an aqueous dispersion for chemical mechanical polishing is not excellent.

1.6 Other Additives The following additives can be added to the chemical mechanical polishing aqueous dispersion according to this embodiment as necessary.

1.6.1 Surfactant A surfactant may be added to the chemical mechanical polishing aqueous dispersion according to this embodiment, if necessary. Examples of the surfactant include a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant.

  Examples of the cationic surfactant include aliphatic amine salts and aliphatic ammonium salts.

  Examples of the anionic surfactant include carboxylate, sulfonate, sulfate ester salt, phosphate ester salt and the like. Examples of the carboxylate include fatty acid soap and alkyl ether carboxylate. Examples of the sulfonate include alkyl benzene sulfonate, alkyl naphthalene sulfonate, and α-olefin sulfonate. Examples of the sulfate ester salt include higher alcohol sulfate ester salts and alkyl sulfate ester salts. Examples of phosphate esters include alkyl phosphate esters.

  Examples of nonionic surfactants include ether type surfactants, ether ester type surfactants, ester type surfactants, and acetylene type surfactants. Examples of the ether ester type surfactant include polyoxyethylene ether of glycerin ester. Examples of the ester type surfactant include polyethylene glycol fatty acid ester, glycerin ester, sorbitan ester and the like. Examples of the acetylenic surfactant include ethylene oxide adducts of acetylene alcohol, acetylene glycol, and acetylene diol.

  Examples of amphoteric surfactants include betaine surfactants.

  These surfactants can be used singly or in combination of two or more.

  Among these surfactants, anionic surfactants are preferable, and sulfonates are particularly preferable. Of the sulfonates, alkylbenzene sulfonates are preferred, and dodecylbenzene sulfonate is particularly preferred.

  The addition amount of the surfactant is preferably 1% by mass or less, more preferably 0.001 to 0.1% by mass with respect to the mass of the chemical mechanical polishing aqueous dispersion at the time of use. When the addition amount of the surfactant is within the above range, a smooth polished surface can be obtained after the silicon nitride film is removed by polishing.

1.6.2 Acid or Base The chemical mechanical polishing aqueous dispersion according to this embodiment may contain an acid or a base as necessary. The pH of the chemical mechanical polishing aqueous dispersion according to the present embodiment needs to be 3 or more and 5 or less as described above. The acid and base can be used for the purpose of adjusting the pH of the chemical mechanical polishing aqueous dispersion.

  Examples of the acid include organic acids and inorganic acids (excluding phosphoric acid).

  Examples of organic acids include tartaric acid, malic acid, citric acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, isoprenesulfonic acid, gluconic acid, lactic acid, glycolic acid, malonic acid, formic acid, oxalic acid, succinic acid, and fumaric acid. Maleic acid, phthalic acid and the like are preferable. Among these organic acids, tartaric acid, malic acid, and citric acid having two or more carboxyl groups and one or more hydroxyl groups in one molecule are particularly preferable. Since the hydroxyl group in the organic acid is hydrogen-bonded with a nitrogen atom existing in the silicon nitride film, a large amount of the organic acid is present on the surface of the silicon nitride film. Thereby, the carboxyl group in the organic acid exerts a chemical polishing action on the silicon nitride film, and the polishing rate of the silicon nitride film can be increased. These organic acids also have a buffering action for preventing a rapid change in pH due to the addition of phosphoric acid.

  Examples of inorganic acids include nitric acid and sulfuric acid.

  Examples of the base include organic bases and inorganic bases.

  Examples of the organic base include tetramethylammonium hydroxide (TMAH) and tetraethylammonium hydroxide (TEAH).

  Examples of the inorganic base include alkali metal hydroxides. Specific examples include sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide and the like.

1.6.3 Water-soluble polymer The chemical mechanical polishing aqueous dispersion according to this embodiment may contain a water-soluble polymer, if necessary. The water-soluble polymer has a function of adsorbing to the surface of the surface to be polished and reducing polishing friction. Thereby, when a water-soluble polymer is added, the occurrence of dishing and corrosion can be suppressed.

  Examples of the water-soluble polymer include polyacrylamide, polyacrylic acid, polyvinyl alcohol, polyvinyl pyrrolidone, and hydroxyethyl cellulose.

  The addition amount of the water-soluble polymer can be adjusted so that the viscosity of the chemical mechanical polishing aqueous dispersion is less than 2 mPa · s. Since the viscosity of the chemical mechanical polishing aqueous dispersion according to the present invention is substantially determined by the weight average molecular weight and the addition amount of the water-soluble polymer, it can be adjusted in consideration of the balance between them. When the viscosity of the chemical mechanical polishing aqueous dispersion exceeds 2 mPa · s, the polishing rate may decrease, and the viscosity becomes too high to stably supply the chemical mechanical polishing aqueous dispersion on the polishing cloth. There is. As a result, an increase in the temperature of the polishing cloth, uneven polishing (deterioration of in-plane uniformity), and the like may occur, resulting in variations in polishing rate and dishing.

1.6.4 Anticorrosive Agent Examples of the anticorrosive agent used in the chemical mechanical polishing aqueous dispersion according to this embodiment include benzotriazole and derivatives thereof. Here, the benzotriazole derivative means one obtained by substituting one or more hydrogen atoms of benzotriazole with, for example, a carboxyl group, a methyl group, an amino group, a hydroxyl group or the like. Examples of the benzotriazole derivatives include 4-carboxylbenzotriazole and its salt, 7-carboxybenzotriazole and its salt, benzotriazole butyl ester, 1-hydroxymethylbenzotriazole, 1-hydroxybenzotriazole and the like.

  The amount of the anticorrosive added is preferably 1% by mass or less, more preferably 0.001 to 0.1% by mass, based on the mass of the chemical mechanical polishing aqueous dispersion at the time of use.

1.7 Preparation Method of Chemical Mechanical Polishing Aqueous Dispersion The chemical mechanical polishing aqueous dispersion according to the present embodiment can be prepared by dissolving or dispersing each of the above components in a solvent such as water. The dissolution or dispersion method is not particularly limited, and any method may be applied as long as it can be uniformly dissolved and dispersed. Also, the mixing order and mixing method of each component are not particularly limited.

  The chemical mechanical polishing aqueous dispersion according to this embodiment can be prepared as a concentrated stock solution and diluted with a solvent such as water when used.

2. Chemical Mechanical Polishing Method and Semiconductor Device Manufacturing Method A chemical mechanical polishing method and a semiconductor device manufacturing method according to this embodiment will be described in detail with reference to the drawings.

2.1 Object to be treated FIG. 4 shows an example of an object to be treated 100 according to the chemical mechanical polishing method of the first specific example. First, a first silicon oxide film 20 as a stopper is formed on the silicon substrate 10 using a CVD method or a thermal oxidation method. Further, a silicon nitride film 30 is formed on the first silicon oxide film 20 by using the CVD method.

  Next, the silicon nitride film 30 is patterned. Using this as a mask, a trench 50 is formed to communicate the silicon substrate 10 or the silicon oxide film 20 by applying a photolithography method or an etching method.

  Finally, when silicon oxide is deposited so as to fill the trench 50, the workpiece 100 is obtained.

2.2 Chemical Mechanical Polishing Method (1) First, in order to remove the second silicon oxide film 40 deposited on the silicon nitride film 30 of the workpiece 100, the polishing rate ratio of the silicon oxide film to the silicon nitride film is Chemical mechanical polishing is performed using a large chemical mechanical polishing aqueous dispersion. Thereby, as shown in FIG. 5, most of the second silicon oxide film 40 can be removed.

  (2) As shown in FIG. 5, a chemical mechanical polishing can be performed on the surface to be polished in which the silicon oxide film and the silicon nitride film coexist using the chemical mechanical polishing aqueous dispersion according to this embodiment. . As the second silicon oxide film 40 is polished, the silicon nitride film 30 appears. Here, when polishing using a conventional chemical mechanical polishing aqueous dispersion, the polishing rate ratio of the silicon nitride film to the silicon oxide film is large, so that the occurrence of dishing of the silicon oxide film cannot be suppressed. It was.

  However, when polishing is performed using the chemical mechanical polishing aqueous dispersion according to the present embodiment, the polishing rate of the silicon oxide film and the silicon nitride film can be made substantially equal during polishing. The silicon nitride film can be polished while suppressing this. That is, the chemical mechanical polishing aqueous dispersion according to this embodiment can polish the entire surface to be polished while always maintaining a flat state.

  (3) Thus, a semiconductor device in which silicon oxide is embedded in the trench 50 as shown in FIG. 6 can be obtained. The chemical mechanical polishing method according to the present embodiment can be applied to, for example, trench isolation (STI).

3. Examples Hereinafter, the present invention will be described by way of examples. However, the present invention is not limited to the examples.

3.1 Preparation of Aqueous Dispersion Containing Inorganic Abrasive Grains 3.1.1 Preparation of Aqueous Dispersion Containing Colloidal Silica In a flask with a capacity of 2000 cm ³ , 70 g of 25% strength by weight ammonia water, 40 g of ion-exchanged water, and 175 g of ethanol Then, 21 g of tetraethoxysilane was added, and the temperature was raised to 60 ° C. while stirring at 180 rpm. The mixture was stirred at 60 ° C. for 1 hour and then cooled to obtain a colloidal silica / alcohol dispersion. Subsequently, the alcohol in the dispersion is removed by repeating the operation of removing the alcohol content several times while adding ion-exchanged water to the dispersion at 80 ° C. using an evaporator, and the aqueous dispersion having the solid content concentration shown in Table 1 is removed. The body was prepared. The average particle size calculated from the specific surface area measured using the BET method described above was 15 nm. In addition, the surface area measurement by BET method used for calculation used the value measured after removing the solution from colloidal silica and heat-processing at 800 degreeC. In addition, a particle image was taken with a transmission electron microscope (H-7650, manufactured by Hitachi High-Technologies Corporation) under the conditions of a photographing magnification of 20000 times, and 50 colloidal silica particles were measured by the method described above. The average value of the major axis and the minor axis was calculated, and the ratio of the major axis to the minor axis was calculated. Colloidal silica having other particle sizes was prepared by adjusting the addition amount of tetraethoxysilane and the stirring time in a timely manner by the same production method as described above.

  Similarly, using colloidal silica (product number; PL-1, PL-2, PL-2L, PL-3, PL-3L, PL-3H, PL-5, EXP-101) manufactured by Fuso Chemical Industry Co., Ltd. An aqueous dispersion was prepared.

3.1.2 Preparation of Aqueous Dispersion Containing Fumed Silica 2 kg of trade name “Aerosil # 90” (manufactured by Nippon Aerosil Co., Ltd.) was dispersed in 6.7 kg of ion-exchanged water using an ultrasonic disperser. . Then, it filtered using the filter of 5 micrometers of hole diameters, and obtained the water dispersion containing 23 mass% of fumed silica particles. In addition, the average particle diameter computed from the specific surface area measured using BET method mentioned above was 30 nm.

  An aqueous dispersion containing fumed silica having an average particle size of 54 nm was prepared by performing the same operation using the trade name “Aerosil # 50” (manufactured by Nippon Aerosil Co., Ltd.) instead of the above “Aerosil # 90”. did.

3.1.3 Preparation of aqueous dispersion containing fumed ceria Ceric oxide powder was obtained by baking cerium hydroxide at 900 ° C. for 2 hours. The obtained cerium oxide powder was dispersed in ion-exchanged water using a bead mill to obtain an aqueous dispersion containing 10% by mass of cerium oxide. The average particle size calculated from the specific surface area measured using the BET method described above was 45 nm.

  On the other hand, the powder of cerium oxide was obtained by baking cerium hydroxide at 700 ° C. for 2 hours. The obtained cerium oxide powder was dispersed in ion-exchanged water using a bead mill to obtain an aqueous dispersion containing 10% by mass of cerium oxide. The average particle size calculated from the specific surface area measured using the BET method described above was 20 nm.

3.2 Preparation of chemical mechanical polishing aqueous dispersion A predetermined amount of the aqueous dispersion prepared in “3.1 Preparation of aqueous dispersion containing inorganic abrasive grains” is put into a polyethylene bottle having a capacity of 1000 cm ³ , To this, phosphoric acid, polyethyleneimine, and other additives were respectively added so as to have a predetermined content, and sufficiently mixed and stirred. Polyethyleneimine used was a product (product number; SP-003, SP-006, SP-012, SP-018, SP-200) manufactured by Nippon Shokubai Co., Ltd. Then, surfactant aqueous solution was added as needed, stirring. Further, ion-exchanged water was added, and the quaternary ammonium compound was gradually added while confirming a predetermined pH within a range of 0.1 to 5% by mass, and the dispersion was adjusted to have a predetermined pH. Filtration was performed with a 5 μm filter to obtain an aqueous dispersion for chemical mechanical polishing used in Examples, Comparative Examples, and Reference Examples.

3.3 Chemical Mechanical Polishing Test Using the chemical mechanical polishing aqueous dispersion prepared in “3.2 Preparation of Chemical Mechanical Polishing Aqueous Dispersion”, a silicon substrate with a silicon nitride film or silicon oxide film having a diameter of 8 inches was used. As the object to be polished, chemical mechanical polishing was performed under the following <Polishing Conditions 1>.
<Polishing condition 1>
・ Polishing equipment: Model “EPO-112” manufactured by Ebara Corporation
・ Polishing pad: “IC1000 / K-Groove” manufactured by Rodel Nitta Co., Ltd.
・ Chemical mechanical polishing aqueous dispersion supply speed: 200 mL / min ・ Surface plate rotation speed: 90 rpm
・ Rotation speed of polishing head: 90 rpm
Polishing head pressing pressure: 280 hPa
3.3.1 Calculation of Polishing Rate For each of the 8-inch diameter silicon nitride film or the substrate with the silicon oxide film as the object to be polished, the film thickness before polishing is measured by the optical interference film thickness meter “NanoSpec 6100” (Nanometrics). -It measured beforehand by Japan Co., Ltd. and grind | polished for 1 minute on said conditions. The film thickness of the polished object after polishing was similarly measured using an optical interference film thickness meter, and the difference between the film thickness before and after polishing, that is, the film thickness decreased by chemical mechanical polishing was determined. Then, the polishing rate was calculated from the film thickness decreased by chemical mechanical polishing and the polishing time. The results are shown in Tables 1 to 4.

3.4 Examples 1 to 15 and Comparative Examples 1 to 15
Examples 1 to 15 and Comparative Examples 1 to 15 are obtained by partially changing the components or concentrations of the chemical mechanical polishing aqueous dispersion as described in Tables 1 to 4.

  In each of the chemical mechanical polishing aqueous dispersions of Examples 1 to 15, the polishing rate ratio of the silicon nitride film to the silicon oxide film is in the range of 0.7 to 1.1. Therefore, when chemical mechanical polishing is performed using the chemical mechanical polishing aqueous dispersions of Examples 1 to 15, dishing of the silicon oxide film occurs on the flat surface to be polished that shares the silicon oxide film and the silicon nitride film. The silicon nitride film can be polished while suppressing.

  Comparative Examples 1 and 2 are examples in which a slurry containing fumed silica as abrasive grains was applied. In either case, the polishing rate of the silicon nitride film is high and the object of the present invention cannot be achieved.

  Comparative Examples 3 and 4 are examples in which a slurry containing fumed ceria as abrasive grains was applied. In either case, since the polishing rate of the silicon oxide film is high and an appropriate polishing rate ratio cannot be obtained, the object of the present invention cannot be achieved.

  Comparative Example 5 is an example in which a slurry containing colloidal silica having an average particle diameter of 6 nm is applied as abrasive grains. Since the polishing rate of the silicon nitride film is high and an appropriate polishing rate ratio cannot be obtained, the object of the present invention cannot be achieved.

  Comparative Example 6 is an example in which colloidal silica having an average particle diameter of 70 nm was used as the abrasive grains. Since the polishing rate of the silicon oxide film is too high and an appropriate polishing rate ratio cannot be obtained, the object of the present invention cannot be achieved.

  Comparative Example 7 is an example in which a slurry having a pH of less than 3 was applied. Since the polishing rate of the silicon nitride film with respect to the silicon oxide film is reduced, the object of the present invention cannot be achieved.

  Comparative Example 8 is an example in which a slurry having a pH exceeding 5 was applied. Aggregation of colloidal silica was observed, and the evaluation test could not be performed.

  Comparative Example 9 is an example in which a slurry containing colloidal silica having an average particle diameter of 70 nm as an abrasive grain and having a pH exceeding 5 was applied. Aggregation of colloidal silica was observed, and the evaluation test could not be performed.

  Comparative Examples 10 to 13 are examples in which a slurry containing no polyethyleneimine was applied. In the slurry not containing polyethyleneimine, the tendency of not being able to maintain the balance between the polishing rate for the silicon oxide film and the polishing rate for the silicon nitride film is recognized, so the object of the present invention cannot be achieved.

  Comparative Example 14 is an example in which a slurry containing colloidal silica having an average particle diameter of 51.9 nm as an abrasive grain and having a pH of less than 3 was applied. Since the polishing rate of the silicon oxide film with respect to the silicon nitride film becomes too high, the object of the present invention cannot be achieved.

  Comparative Example 15 is an example in which a slurry containing polyethyleneimine containing no phosphoric acid and having a number average molecular weight of 20,000 is applied. Since it did not contain phosphoric acid and the molecular weight of polyethyleneimine was too large, precipitation derived from polyethyleneimine was confirmed in the chemical mechanical polishing aqueous dispersion. Therefore, it could not be evaluated.

  As described above, the chemical mechanical polishing aqueous dispersions of Comparative Examples 1 to 15 cannot achieve the object of the present invention.

3.5 Examples 16-19
In Examples 16 to 19, liquid A (4% by mass of phosphoric acid, polyethyleneimine [molecular weight 600] 0.05% by mass and tetramethylammonium hydroxide were added in an appropriate amount to adjust the pH to 3.7) and liquid B (12.5% by mass of colloidal silica having an average particle size of 15 nm is added to adjust the pH to 7) is prepared in advance, and A liquid, B liquid, and deionized water are mixed in the proportions shown in Table 5. This is an example in which the “3.3 chemical mechanical polishing test” was carried out using the obtained chemical mechanical polishing aqueous dispersion.

  Example 16 has the same composition as Example 1. The result of the chemical mechanical polishing test of Example 16 was exactly the same as that of Example 1. From this, it can be seen that if the compositions are the same, the order of addition of the additives has little influence on the polishing rate of the silicon oxide film or silicon nitride film.

  Examples 17 to 19 are examples in which “3.3 chemical mechanical polishing test” was performed using chemical mechanical polishing aqueous dispersions obtained by variously changing the ratios of liquid A, liquid B, and deionized water. It is. It can be seen that the polishing rate ratio can be controlled to 0.7 to 1.1 by adjusting the ratios of the A liquid, the B liquid, and the deionized water as in Examples 17 to 19.

  Examples 20 to 22 are examples in which the “3.3 chemical mechanical polishing test” was performed using the chemical mechanical polishing aqueous dispersion obtained in Example 15 and variously changing the polishing conditions. There were four polishing conditions: polishing load, flow rate of the chemical mechanical polishing aqueous dispersion, table rotation speed, and head rotation speed, and these conditions were variously changed. The chemical mechanical polishing aqueous dispersion obtained in Example 15 was able to achieve a polishing rate ratio of 0.7 to 1.1 under any polishing condition. This shows that the chemical mechanical polishing aqueous dispersion according to the present embodiment can provide a stable polishing rate ratio that does not vary depending on the polishing conditions.

3.6 Experimental Example 3.6.1 First Experimental Example Chemical mechanical polishing was performed using a test wafer embedded with a silicon nitride film in advance. Specifically, the object to be processed 200 is a test wafer manufactured by 864 CMP (advanced materials technology, having a cross-sectional structure as shown in FIG. 7, and the silicon nitride film 32 is formed from the bottom of the polysilicon film 12. The thickness up to the top is about 500 nm, the thickness of the silicon oxide film 22 is about 10 nm, and the thickness of the silicon nitride film 32 is about 150 nm.

The test wafer was previously subjected to chemical mechanical polishing for 100 seconds under the following <Polishing condition 2> using CMS4301 and 4302 manufactured by JSR.
<Polishing condition 2>
・ Polishing equipment: Model “EPO-112” manufactured by Ebara Corporation
・ Polishing pad: “IC1000 / K-Groove” manufactured by Rodel Nitta Co., Ltd.
・ Chemical mechanical polishing aqueous dispersion supply speed: 200 mL / min ・ Surface plate rotation speed: 100 rpm
-Polishing head rotation speed: 107 rpm
・ Polishing head pressing pressure: 350 hPa
As shown in FIG. 8, most of the silicon oxide film 42 on the silicon nitride film 32 has been removed from the polished surface after chemical mechanical polishing. When the thickness of the silicon oxide film 42 on the silicon nitride film 32 within a 100 μm pitch with a pattern density of 50% was measured by an optical interference type film thickness meter “NanoSpec 6100”, the thickness of the silicon oxide film 42 was about 100 nm. It was.

  Further, in order to measure the level difference of the silicon nitride film 32, the level difference was not confirmed when measured with a stylus type level difference measuring device “HRP240”.

  Next, the chemical mechanical polishing aqueous dispersion according to Example 1 was used for polishing for 180 seconds under the above <Polishing Condition 1>.

  As a result, a semiconductor device as shown in FIG. 9 was obtained. The thickness of the silicon nitride film 32 on the polished surface after polishing was approximately 0 nm. The dishing amount of the second silicon oxide film 42 in a 100 μm pitch with a pattern density of 50% was also almost 0 nm.

  For this reason, when the chemical mechanical polishing aqueous dispersion according to Example 1 is used, the polishing rates of the silicon nitride film and the silicon oxide film can be made substantially the same, so that the occurrence of dishing of the silicon oxide film is suppressed. It can be seen that it is effective in removing the silicon nitride film.

3.6.2 Second Experimental Example Chemical mechanical polishing was performed using a test wafer embedded with a silicon nitride film in advance. Specifically, the object to be processed 300 is a test wafer manufactured by 864 CMP (advanced materials technology) having a cross-sectional structure as shown in FIG. 10, and the top of the silicon nitride film 32 from the bottom of the silicon film 14. The thickness of the silicon oxide film 22 is about 10 nm, and the thickness of the silicon nitride film 32 is about 150 nm.

  The test wafer was previously subjected to chemical mechanical polishing for 100 seconds under the above <Polishing condition 2> using CMS4301 and 4302 manufactured by JSR.

  As shown in FIG. 11, most of the silicon oxide film 42 on the silicon nitride film 32 was removed from the surface to be polished after chemical mechanical polishing. When the thickness of the silicon oxide film 42 on the silicon nitride film 32 within a 100 μm pitch with a pattern density of 50% was measured by an optical interference type film thickness meter “NanoSpec 6100”, the thickness of the silicon oxide film 42 was about 100 nm. It was.

  Further, in order to measure the level difference of the silicon nitride film 32, the level difference was not confirmed when measured with a stylus type level difference measuring device “HRP240”.

  Next, the chemical mechanical polishing aqueous dispersion according to Example 9 was used for polishing for 180 seconds under the above <Polishing Condition 1>.

  As a result, a semiconductor device as shown in FIG. 12 was obtained. The thickness of the silicon nitride film 32 on the polished surface after polishing was approximately 0 nm. The dishing amount of the second silicon oxide film 42 in a 100 μm pitch with a pattern density of 50% was also almost 0 nm.

  From this, when the chemical mechanical polishing aqueous dispersion according to Example 9 is used, the polishing rate of the silicon nitride film and the silicon oxide film can be made substantially the same, so that the occurrence of dishing of the silicon oxide film is suppressed. It can be seen that it is effective in removing the silicon nitride film.

3.6.3 Third Experimental Example The workpiece 300 was subjected to chemical mechanical polishing by the same method as in Experimental Example 1.

  As shown in FIG. 11, most of the second silicon oxide film 42 on the silicon nitride film 32 was removed from the polished surface after chemical mechanical polishing. When the thickness of the silicon oxide film 42 on the silicon nitride film 32 within a 100 μm pitch with a pattern density of 50% was measured by an optical interference type film thickness meter “NanoSpec 6100”, the thickness of the silicon oxide film 42 was about 100 nm. It was.

  Further, in order to measure the level difference of the silicon nitride film 32, the level difference was not confirmed when measured with a stylus type level difference measuring device “HRP240”.

  Next, the chemical mechanical polishing aqueous dispersion according to Example 1 was used for polishing for 180 seconds under the above <Polishing Condition 1>.

  As a result, a semiconductor device as shown in FIG. 12 was obtained. The thickness of the silicon nitride film 32 on the polished surface after polishing was approximately 0 nm. The dishing amount of the second silicon oxide film 42 in a 100 μm pitch with a pattern density of 50% was also almost 0 nm.

  Therefore, when the chemical mechanical polishing aqueous dispersion according to Example 1 is used, the polishing rates of the silicon nitride film and the silicon oxide film can be made substantially the same, so that the occurrence of dishing of the silicon oxide film is suppressed. It can be seen that it is effective in removing the silicon nitride film.

Claims (9)

(A) The average particle size calculated from the specific surface area measured using the BET method is colloidal silica of 10 nm to 50 nm;
(B) phosphoric acid;
(C) polyethyleneimine;
(D) a quaternary ammonium compound represented by the following general formula (1);
And a chemical mechanical polishing aqueous dispersion having a pH of 3 to 5.

(In formula (1), R ₁ to R ₄ each independently represent a hydrocarbon group. M ⁻ represents an anion.) In claim 1,
The chemical mechanical polishing aqueous dispersion, wherein the mass ratio (C) / (A) of the component (A) to the component (C) is 0.001 to 0.05. In claim 1 or 2,
The chemical mechanical polishing aqueous dispersion, wherein the mass ratio (C) / (B) of the component (B) to the component (C) is 0.002 to 0.2. In any of claims 1 to 3,
The chemical mechanical polishing aqueous dispersion, wherein the number average molecular weight of the component (C) is 100 to 2,000. In any of claims 1 to 4,
An aqueous dispersion for chemical mechanical polishing further comprising at least one organic acid selected from tartaric acid, malic acid and citric acid. In any of claims 1 to 5,
The chemical mechanical polishing aqueous dispersion wherein the ratio (Rmax / Rmin) of the major axis (Rmax) to the minor axis (Rmin) of the colloidal silica particles of the component (A) is greater than 1.2. In any one of Claims 1 thru | or 6.
A chemical mechanical polishing aqueous dispersion having a polishing rate ratio of silicon nitride film to silicon oxide film (silicon nitride film / silicon oxide film) of 0.9 to 1.1. In any one of Claims 1 thru | or 7,
A chemical mechanical polishing aqueous dispersion for polishing a surface to be polished of a semiconductor device in which a silicon nitride film and a silicon oxide film coexist.   The chemical mechanical polishing aqueous dispersion according to claim 1 is used to polish a surface to be polished on which a silicon oxide film and a silicon nitride film coexist, and the polishing is stopped at the silicon oxide film. Chemical mechanical polishing method for semiconductor devices.

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