JP2013045944A - Polishing method of substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing method capable of enhancing planarity of the surface after polishing, while maintaining the polishing speed for an inorganic insulating film, in the CMP technique for polishing an inorganic insulating film formed on the surface of a substrate.SOLUTION: In the polishing method of a substrate, at least a part of a polished film provided on the substrate is removed by polishing, by using a CMP polishing liquid containing a cerium oxide, an organic acid having at least one group selected from -COOM group, -Ph-OM group, -SOM group, -OSOH group, -POMgroup, and -POMgroup (In the formula, M is any one kind selected from H, NH, Na, and K, and Ph represents a phenyl group which may have a substituent group), a polymer compound having a carboxyl group, and water, having pH of 4.5-7.0, and containing 0.01-0.30 mass% of polymer compound for total mass, and a polishing pad in which multiple grooves and holes are formed.

Description

  The present invention relates to a method for polishing a substrate. More specifically, the present invention is a semiconductor device manufacturing technique, a planarization process of a substrate surface, in particular, a planarization process of an interlayer insulating film, a BPSG film (silicon dioxide film doped with boron or phosphorus), a shallow trench. The present invention relates to a substrate polishing method used in a separation (hereinafter referred to as “STI”) formation process or the like.

  In the current ULSI semiconductor device manufacturing process, processing technology for high density and miniaturization of semiconductor devices has been researched and developed. CMP (Chemical Mechanical Polishing) technology, which is one of the processing technologies, is indispensable when performing planarization of interlayer insulation films, STI formation, plugs and buried metal wiring formation, etc. in the semiconductor device manufacturing process. Has become a technology.

  Conventionally, in a semiconductor device manufacturing process, an inorganic insulating film such as a silicon oxide film is formed by a method such as plasma-CVD (chemical vapor deposition) or low-pressure CVD (chemical vapor deposition). As a chemical mechanical polishing method for planarizing the inorganic insulating film, it is generally studied to use a fumed silica-based CMP polishing liquid. A fumed silica-based CMP polishing liquid is produced by adjusting the pH of a slurry containing particles obtained by grain growth by a method such as thermal decomposition of silicon tetrachloride. However, such a fumed silica-based CMP polishing liquid has a technical problem that the polishing rate is low.

  In the generations after the design rule 0.25 μm, STI is used for element isolation in the integrated circuit. In STI, CMP technology is used to remove excess inorganic insulating film formed on a substrate. In this case, in order to stop the polishing at an arbitrary depth, a stopper film such as a silicon nitride film that is difficult to polish is formed under the inorganic insulating film.

  In such a structure, it is desirable that the polishing rate ratio between the inorganic insulating film and the stopper film is large in order to efficiently remove the excess inorganic insulating film and sufficiently suppress the progress of the subsequent polishing. However, the conventional colloidal silica-based CMP polishing liquid has a polishing rate ratio as small as about 3 between the inorganic insulating film and the stopper film, and does not have a characteristic that can be practically used for STI.

  On the other hand, a cerium oxide CMP polishing liquid containing cerium oxide particles is used as a CMP polishing liquid for glass surfaces such as photomasks and lenses. Cerium oxide particles have a lower hardness than silica particles and alumina particles, and are difficult to scratch on the polished surface during polishing, and thus are useful for finish mirror polishing. Further, the cerium oxide CMP polishing liquid has an advantage that the polishing rate is faster than that of fumed silica-based or colloidal silica-based silica CMP polishing liquid.

  As a cerium oxide CMP polishing liquid, the following Patent Document 1 describes a semiconductor CMP polishing liquid using high-purity cerium oxide abrasive grains. Patent Document 2 described below describes a technique of adding an additive to control the polishing rate of a cerium oxide CMP polishing liquid and improve global flatness.

Japanese Patent Laid-Open No. 10-106994 Japanese Patent No. 3278532

  In recent years, with the progress of miniaturization of STI design rules, a polishing method capable of achieving further improvement in flatness has been demanded.

  The STI formation process using CMP generally includes an inorganic insulating film so as to bury the irregularities and cover the entire substrate on a substrate on which an active portion (convex portion) and a trench portion (concave portion) are formed. Then, the excess inorganic insulating film is removed by polishing using a CMP polishing liquid. At this time, a phenomenon called dishing may occur in which the inorganic insulating film in the trench is excessively polished and recessed in a dish shape. On the other hand, if it is attempted to improve the flatness by eliminating the dishing by devising the composition of the CMP polishing liquid, the polishing rate for the inorganic insulating film decreases, and the polishing time until the stopper film is exposed is prolonged. There is a problem.

  The present invention has been made in view of the above circumstances, and in a CMP technique for polishing an inorganic insulating film formed on the surface of a substrate, the surface after polishing while maintaining a practical polishing rate for the inorganic insulating film. An object of the present invention is to provide a polishing method capable of improving the flatness of the substrate.

  The present invention has found that, in a polishing method using a CMP polishing liquid and a polishing pad, a combination of a CMP polishing liquid having a predetermined composition and a polishing pad having a predetermined surface shape is effective in solving the above problems. It is a thing.

Specifically, the present invention uses a CMP polishing liquid containing cerium oxide, an organic acid A, a polymer compound B, and water, and a polishing pad C, and at least a part of a film to be polished provided on a substrate. In the polishing method for removal by polishing, the organic acid A includes a —COOM group, a —Ph—OM group, a —SO ₃ M group, a —OSO ₃ H group, a —PO ₄ M ₂ group, and a —PO ₃ M _2. At least selected from the group consisting of groups (wherein M is any one selected from H, NH ₄ , Na and K, and Ph represents a phenyl group which may have a substituent). An organic acid having one group, the polymer compound B is a polymer compound having a carboxyl group, and the CMP polishing liquid has a pH of 4.5 to 7.0; Is contained in an amount of 0.01-0. 0 is the mass%, wherein the polishing pad C, a polishing method in which a plurality of grooves and a plurality of holes formed by formed.

  According to such a polishing method, the flatness of the polished surface can be improved while polishing the inorganic insulating film formed on the surface of the substrate at a practical polishing rate.

  The polishing method of the present invention supplies the CMP polishing liquid between the film to be polished and the polishing pad in a state where the film to be polished of the substrate on which the film to be polished is pressed against the polishing pad of the polishing platen. However, it is preferable to polish the film to be polished by relatively moving the substrate and the polishing pad.

  The groove includes: an X groove constituted by a plurality of grooves parallel to each other on the polishing pad plane; and a Y groove constituted by a plurality of grooves perpendicular to the X groove on the polishing pad plane. It is preferable to have a configured XY groove. By using a polishing pad having such grooves and holes, the flatness can be further improved.

  From the viewpoint of achieving both flatness and polishing rate, it is preferable that the plurality of X grooves in the polishing pad are provided with a plurality of grooves at equal intervals. Further, it is preferable that the plurality of X grooves and the Y grooves are each provided with a plurality of grooves at equal intervals. Furthermore, it is preferable that the polishing pad has a grid-like groove in which the gap between the X grooves and the gap between the Y grooves are formed to be equal. Further, the pad preferably has a circular hole.

  The content of the organic acid compound is preferably 0.0001 to 5% by mass based on the total mass of the CMP polishing liquid. As a result, it is possible to achieve both the surface flatness after polishing and the maintenance of the polishing rate and the suppression of cerium oxide aggregation.

  According to the present invention, in a CMP technique for polishing a film to be polished (for example, an STI film) formed on the surface of a substrate, polishing of the substrate capable of improving surface flatness after polishing of the film to be polished A method can be provided.

It is a schematic cross section showing an evaluation substrate for polishing characteristics.

Hereinafter, embodiments of the present invention will be described in detail. The polishing method according to this embodiment uses a CMP polishing liquid containing cerium oxide, an organic acid A, a polymer compound B, and water, and a polishing pad C, and at least a part of a film to be polished provided on the substrate. In the polishing method for removal by polishing, the organic acid A includes a —COOM group, a —Ph—OM group, a —SO ₃ M group, a —OSO ₃ H group, a —PO ₄ M ₂ group, and a —PO ₃ M _2. At least selected from the group consisting of groups (wherein M is any one selected from H, NH ₄ , Na and K, and Ph represents a phenyl group which may have a substituent). An organic acid having one group, the polymer compound B is a polymer compound having a carboxyl group, and the CMP polishing liquid has a pH of 4.5 to 7.0; The content of 0.01 relative to the total mass of the CMP polishing liquid 0.30 wt%, wherein the polishing pad C, a polishing method in which a plurality of grooves and a plurality of holes formed by formed. Hereinafter, the polishing method according to the present embodiment will be described in detail.

(1) Polishing Pad The polishing method of the present invention uses a polishing pad formed with a plurality of grooves and a plurality of holes as a polishing pad. Conventionally, various types of polishing pads have been used, and the most commonly used in CMP polishing is a Groove pad in which grooves are formed to hold the polishing liquid over the entire pad. However, in the polishing method of the present invention, not only such a groove but also a polishing pad in which both a groove and a hole are formed is used. As a result, an appropriate amount of slurry can be held, so that both flatness and polishing rate can be achieved.

  In the polishing pad, examples of the groove include a plurality of linear grooves parallel to each other, a plurality of concentric grooves, a radial groove, a spiral groove, and the like. Among these, a plurality of linear grooves parallel to each other is preferable. In addition, the X groove is composed of a plurality of grooves parallel to each other on the polishing pad plane, and the Y groove is composed of a plurality of grooves perpendicular to the X groove on the polishing pad plane. It is more preferable to use a polishing pad having an XY groove (XY-Groove) in that both surface flatness after polishing and maintenance of the polishing rate can be achieved.

  Examples of the polishing pad having XY-Groove as described above and a plurality of holes include a two-layer structure pad manufactured by Rohm and Haas, trade name: IC1000 / Suba400, and the like. The pad is not limited to the above as long as it has a shape and performance.

(2) CMP polishing liquid The CMP polishing liquid used in the polishing method of the present invention contains cerium oxide, organic acid A, polymer compound B, and water.

(2.1: Cerium oxide particles)
There is no restriction | limiting in particular as a cerium oxide particle, A well-known thing can be used. In general, cerium oxide is obtained by oxidizing a cerium compound such as carbonate, nitrate, sulfate, or oxalate. Examples of the method for producing the cerium oxide particles include firing or oxidation using hydrogen peroxide.

  When cerium oxide particles are used for polishing a silicon oxide film formed by TEOS-CVD method or the like using tetraethoxysilane (hereinafter referred to as “TEOS”) as a Si source, the crystallite diameter of the cerium oxide particles (crystallite The larger the diameter) and the smaller the crystal distortion, that is, the better the crystallinity, the faster the polishing is possible, but there is a tendency that polishing scratches are likely to enter the film to be polished. From this point of view, the cerium oxide particles are preferably composed of two or more crystallites, particles having a crystal grain boundary, and more preferably particles having a crystallite diameter of 5 to 300 nm.

  The content of alkali metal and halogens in the cerium oxide particles is preferably 10 ppm or less because it is suitably used for polishing in the manufacture of semiconductor elements.

  The average particle diameter of the cerium oxide particles is preferably 10 to 500 nm, more preferably 20 to 400 nm, and still more preferably 50 to 300 nm. When the average particle diameter of the cerium oxide particles is 10 nm or more, a good polishing rate tends to be obtained, and when it is 500 nm or less, the film to be polished tends to be hardly damaged.

  Here, the average particle diameter of the cerium oxide particles is a laser diffraction particle size distribution analyzer (for example, product name: Master Sizer Microplus, refractive index: 1.93, light source: He-Ne laser, absorption: 0, manufactured by Malvern). It means the measured D50 value (median diameter of volume distribution, cumulative median value). For the measurement of the average particle diameter, a sample obtained by diluting the CMP polishing liquid to an appropriate concentration (for example, a concentration at which the measurement transmittance (H) for a He—Ne laser is 60 to 70%) is used. In addition, when the cerium oxide CMP polishing liquid is stored separately as a cerium oxide slurry in which cerium oxide particles are dispersed in water and an additive solution in which an additive is dissolved in water, as will be described later, The slurry can be measured by diluting to an appropriate concentration.

  The content of the cerium oxide particles is preferably 0.1 to 20% by mass, more preferably 0.1 to 5% by mass, and still more preferably 0.5 to 1.5% by mass based on the total mass of the CMP polishing liquid. When the content of the cerium oxide particles is 0.1% by mass or more, a good polishing rate tends to be obtained. When the content is 20% by mass or less, aggregation of the particles is suppressed and the film to be polished is damaged. There is a tendency to become difficult.

(2.2: Organic acid A)
[Organic acid compound and / or salt thereof]
The CMP polishing liquid used in the polishing method according to the present invention contains an organic acid A as an additive. As a result, the flatness of the film to be polished (for example, a silicon oxide film) after polishing can be improved. More specifically, when a surface to be polished having irregularities is polished, it is possible to suppress the phenomenon that a part of the surface is excessively polished and recessed like a dish, so-called dishing. This effect can be obtained more efficiently by using an organic acid compound and / or a salt thereof and cerium oxide particles in combination with a polishing pad having a predetermined shape described later.

The organic acid A includes a —COOM group, a —Ph—OM group, a —SO ₃ M group, a —OSO ₃ H group, a —PO ₄ M ₂ group, and a —PO ₃ M ₂ group (wherein M is H, NH ₄ , an organic acid having at least one group selected from the group consisting of any one selected from Na and K, and Ph being a phenyl group which may have a substituent.

Specific examples include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, mytilic acid, pentadecanoic acid, palmitic acid, Heptadecanoic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, o-toluic acid, m-toluic acid, p-toluic acid, o-methoxybenzoic acid, m-methoxybenzoic acid Acid, p-methoxybenzoic acid, acrylic acid, methacrylic acid, crotonic acid, pentenoic acid, hexenoic acid, heptenoic acid, octenoic acid, nonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, Hexadecenoic acid, heptadecenoic acid, isobutyric acid, isovaleric acid, keto Cinnamic acid, quinaldic acid, nicotinic acid, 1-naphthoic acid, 2-naphthoic acid, picolinic acid, vinylacetic acid, phenylacetic acid, phenoxyacetic acid, 2-furancarboxylic acid, mercaptoacetic acid, levulinic acid, oxalic acid, malonic acid, succinic acid Acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid Acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,15-pentadecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, Quinolic acid, quinic acid, naphthalic acid, phthalic acid, isophthalic acid, terephthalic acid Acid, glycolic acid, lactic acid, 3-hydroxypropionic acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 5-hydroxyvaleric acid, quinic acid, kynurenic acid, salicylic acid, tartaric acid, Aconitic acid, ascorbic acid, acetylsalicylic acid, acetylmalic acid, acetylenedicarboxylic acid, acetoxysuccinic acid, acetoacetic acid, 3-oxoglutaric acid, atropaic acid, atrolactic acid, anthraquinone carboxylic acid, anthracene carboxylic acid, isocaproic acid, isocamphoric acid, Isocrotonic acid, 2-ethyl-2-hydroxybutyric acid, ethylmalonic acid, ethoxyacetic acid, oxaloacetic acid, oxydiacetic acid, 2-oxobutyric acid, camphoric acid, citric acid, glyoxylic acid, glycidic acid, glyceric acid, glucaric acid, glucone acid , Croconic acid, cyclobutanecarboxylic acid, cyclohexanedicarboxylic acid, diphenylacetic acid, di-O-benzoyltartaric acid, dimethylsuccinic acid, dimethoxyphthalic acid, tartronic acid, tannic acid, thiophenecarboxylic acid, tiglic acid, desoxolic acid, tetrahydroxysuccinic acid , Tetramethylsuccinic acid, tetronic acid, dehydroacetic acid, terevic acid, tropic acid, vanillic acid, paraconic acid, hydroxyisophthalic acid, hydroxycinnamic acid, hydroxynaphthoic acid, o-hydroxyphenylacetic acid, m-hydroxyphenylacetic acid, p-hydroxyphenylacetic acid, 3-hydroxy-3-phenylpropionic acid, pivalic acid, pyridinedicarboxylic acid, pyridinetricarboxylic acid, pyruvic acid, α-phenylcinnamic acid, phenylglycidic acid, phenylsuccinic acid, Nyl acetic acid, phenyl lactic acid, propiolic acid, sorbic acid, 2,4-hexadienedioic acid, 2-benzylidenepropionic acid, 3-benzylidenepropionic acid, benzylidenemalonic acid, benzylic acid, benzenetricarboxylic acid, 1,2-benzenediacetic acid, Benzoyloxyacetic acid, benzoyloxypropionic acid, benzoylformic acid, benzoylacetic acid, O-benzoyllactic acid, 3-benzoylpropionic acid, gallic acid, mesooxalic acid, 5-methylisophthalic acid, 2-methylcrotonic acid, α-methylcinnamic acid, Methylsuccinic acid, methylmalonic acid, 2-methylbutyric acid, o-methoxycinnamic acid, p-methoxycinnamic acid, mercaptosuccinic acid, mercaptoacetic acid, o-lactoyllactic acid, malic acid, leuconic acid, leucine acid, rosinic acid, Rosoleic acid, α-ketoglutaric acid, -Alcorbic acid, iduronic acid, galacturonic acid, glucuronic acid, pyroglutamic acid, ethylenediaminetetraacetic acid, cyanided triacetic acid, aspartic acid, glutamic acid, N'-hydroxyethyl-N, N, N'-triacetic acid, nitrilotriacetic acid, etc. Carboxylic acid or phenol, o-cresol, m-cresol, p-cresol, o-chlorophenol, m-chlorophenol, p-chlorophenol, o-aminophenol, m-aminophenol, p-aminophenol, o -Phenols such as nitrophenol, m-nitrophenol, p-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol, catechol, resorcinol, hydroquinone, methanesulfonic acid, ethanesulfonic acid Propane sul Phosphonic acid, butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, heptanesulfonic acid, octanesulfonic acid, nonanesulfonic acid, decanesulfonic acid, undecanesulfonic acid, dodecanesulfonic acid, tridecanesulfonic acid, tetradecanesulfonic acid, pentadecanesulfone Acid, hexadecane sulfonic acid, heptadecane sulfonic acid, octadecane sulfonic acid, benzene sulfonic acid, naphthalene sulfonic acid, toluene sulfonic acid, hydroxyethane sulfonic acid, hydroxyphenol sulfonic acid, sulfonic acid such as anthracene sulfonic acid, or decylphosphonic acid Phosphonic acids such as phenylphosphonic acid are preferred. Further, it is a derivative in which one or more protons in the main chain of the carboxylic acid, sulfonic acid, and phosphonic acid are substituted with atoms or atomic groups such as F, Cl, Br, I, OH, CN, and NO _2. May be.

  Furthermore, N-acyl amino acids such as N-acyl-N-methylglycine, N-acyl-N-methyl-β-alanine, N-acyl glutamic acid, polyoxyethylene alkyl ether carboxylic acid, acylated peptide, alkylbenzene sulfonic acid, Linear alkylbenzene sulfonic acid, alkyl naphthalene sulfonic acid, naphthalene sulfonic acid formalin polycondensate, melamine sulfonic acid formalin polycondensate, dialkyl sulfosuccinate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfosuccinic acid, alkyl sulfoacetic acid, α- Olefin sulfonic acid, N-acylmethyl taurine, dimethyl-5-sulfoisophthalate, sulfated oil, higher alcohol sulfate, secondary higher alcohol sulfate, polyoxyethylene alkyl ether Terusulfuric acid, secondary alcohol ethoxysulfate, polyoxyethylene alkylphenyl ether sulfuric acid, monoglycolate, fatty acid alkylol amide sulfate, polyoxyethylene alkyl ether phosphoric acid, polyoxyethylene alkyl phenyl ether phosphoric acid, alkyl phosphoric acid, etc. Can also be preferably used. The organic acid A may be a salt. These can be used alone or in combination of two or more.

Among them, an organic acid having a —SO ₃ M group is preferable, a sulfonic acid in which M is H is more preferable, an aromatic sulfonic acid is further preferable, and a toluenesulfonic acid is particularly preferable. -Toluenesulfonic acid is very particularly preferred.

  The content of the organic acid A is preferably 0.0001 to 5% by mass, more preferably 0.001 to 2% by mass, and still more preferably 0.01 to 0.5% by mass based on the total mass of the CMP polishing liquid. When the content of the organic acid is 0.0001% by mass or more, the flatness of the film to be polished (eg, a silicon oxide film) after polishing tends to be improved, and the content is 5% by mass or less. And, there is a tendency to sufficiently improve the polishing rate of the film to be polished.

(2.3: Polymer compound B)
[Water-soluble organic polymer having a carboxylic acid group or a carboxylic acid group]
The CMP polishing liquid used in the polishing method according to the present invention contains a polymer compound B having a carboxylic acid group or a carboxylic acid group. Here, the polymer compound B may be a salt. Thereby, the flatness of the film to be polished (for example, a silicon oxide film) after completion of polishing can be improved. More specifically, when a surface to be polished having irregularities is polished, it is possible to suppress the phenomenon that a part of the surface is excessively polished and recessed like a dish, so-called dishing. This effect can be obtained more efficiently by using the polymer compound B, the organic acid A, and the cerium oxide particles in combination.
Content of the high molecular compound B is 0.01-0.30 mass% with respect to CMP polishing liquid total mass. When the content of the polymer compound B is 0.01% by mass or more, dishing tends to be suppressed, and when the content is 0.30% by mass or less, the stability of the abrasive grains contained in the CMP polishing liquid. Tend to improve.

  Specific examples of such a high molecular compound B include a homopolymer of a monomer having a carboxylic acid group such as acrylic acid, methacrylic acid, and maleic acid, and a carboxylic acid group portion of the polymer being a single salt such as an ammonium salt. A polymer is mentioned. A copolymer of a monomer having a carboxylic acid group, a monomer having a carboxylic acid group, and a derivative such as an alkyl ester of carboxylic acid is also preferred. More specifically, polyacrylic acid or a polymer in which a part of the carboxylic acid group of the polyacrylic acid is substituted with an ammonium carboxylate base (hereinafter referred to as “polyammonium acrylate”) and the like can be mentioned.

(Other additives)
The CMP polishing liquid used in the polishing method according to the present invention includes a water-soluble polymer as an additive different from the water-soluble organic polymer having an organic acid compound and / or a salt thereof, and a carboxylic acid group or a carboxylic acid group. Can be used. Examples of such water-soluble polymers include polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan and pullulan; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polyamic acid, polyamic acid ammonium salt And polycarboxylic acids such as polyamic acid sodium salt and polyglyoxylic acid and salts thereof; and vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone and polyacrolein.

  These water-soluble polymers preferably have a weight average molecular weight of 500 or more. The weight average molecular weight is a value obtained by measuring with GPC (Gel Permeation Chromatography) and converting to standard polyoxyethylene. Further, the content of these water-soluble polymers is preferably 0.03 to 0.08% by mass based on the total mass of the CMP polishing liquid.

(water)
Although it does not restrict | limit especially as water, Deionized water, ion-exchange water, ultrapure water, etc. are preferable. The water content may be the remainder of the content of each of the above-described components, and is not particularly limited as long as it is contained in the CMP polishing liquid. The CMP polishing liquid may further contain a solvent other than water, for example, a polar solvent such as ethanol or acetone, if necessary.

(Dispersant)
In the CMP polishing liquid used in the polishing method according to the present invention, a dispersing agent for dispersing cerium oxide particles can be used. Examples of the dispersant include a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant, a water-soluble amphoteric dispersant, and the like, among others, a water-soluble anionic dispersant. Is preferred. These can be used alone or in combination of two or more.

  As the water-soluble anionic dispersant, a polymer containing acrylic acid as a copolymerization component and a salt thereof are preferable, and a salt of the polymer is more preferable. Polymers containing acrylic acid as a copolymerization component and salts thereof include, for example, polyacrylic acid and ammonium salts thereof, copolymers of acrylic acid and methacrylic acid and ammonium salts thereof, and acrylic amides and acrylic acids. And copolymers thereof and ammonium salts thereof.

  Examples of other water-soluble anionic dispersants include lauryl sulfate triethanolamine, lauryl ammonium sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and special polycarboxylic acid type polymer dispersants.

  Examples of the water-soluble nonionic dispersant include polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, and polyoxyethylene hydrogenated castor oil. , 2-hydroxyethyl methacrylate, alkyl alkanolamide and the like.

  Examples of the water-soluble cationic dispersant include polyvinyl pyrrolidone, coconut amine acetate, stearyl amine acetate and the like.

  Examples of the water-soluble amphoteric dispersant include lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine and the like.

  The content of the dispersant is in the range of 0.01 to 10% by mass based on the total mass of the CMP polishing liquid from the viewpoint of improving the dispersibility of the cerium oxide particles to suppress sedimentation and further reducing polishing scratches on the polishing target film. Is preferred.

  Although the weight average molecular weight of a dispersing agent does not have a restriction | limiting in particular, 100-150,000 are preferable and 1000-20000 are more preferable. When the molecular weight of the dispersant is 100 or more, a good polishing rate tends to be easily obtained when a film to be polished such as a silicon oxide film or a silicon nitride film is polished. When the molecular weight of the dispersant is 150,000 or less, the storage stability of the CMP polishing liquid tends to be difficult to decrease. The weight average molecular weight is a value measured by GPC and converted to standard polyoxyethylene.

  When the CMP polishing liquid used in the polishing method according to the present invention is used for polishing in the production of semiconductor elements, the content of alkali metals such as sodium ions, halogen, and sulfur in the dispersant is 10 ppm or less. Preferably there is.

(Preparation / preservation / polishing method of CMP polishing liquid)
The CMP polishing liquid used in the polishing method according to the present invention includes, for example, a mixture of cerium oxide particles and water to disperse the particles, and further, an organic acid compound and / or a salt thereof, and a carboxylic acid group or a carboxylic acid base. It can be obtained by adding a water-soluble organic polymer. The CMP polishing liquid according to this embodiment includes cerium oxide particles, an organic acid compound and / or a salt thereof, a water-soluble organic polymer having a carboxylic acid group or a carboxylate group, water, and optionally a water-soluble polymer. A cerium oxide slurry (first liquid) containing cerium oxide particles and water, an organic acid compound and / or a salt thereof, and a water solution having a carboxylic acid group or a carboxylic acid base may be stored as a one-part CMP polishing liquid. It may be stored as a two-component CMP polishing liquid in which components are separated into an additive liquid (second liquid) containing a conductive organic polymer and water.

  In the case of a two-component CMP polishing liquid, the dispersant is preferably contained in the cerium oxide slurry. Additives other than the water-soluble organic polymer having an organic acid compound and / or a salt thereof, and a carboxylic acid group or a carboxylic acid group may be included in either the cerium oxide slurry or the additive solution, but the dispersion of the cerium oxide particles It is preferable to be contained in the additive liquid in that it does not affect the stability.

  When storing as a two-component CMP polishing liquid in which the cerium oxide slurry and the additive liquid are separated, the planarization characteristics and polishing rate can be adjusted by arbitrarily changing the combination of these two liquids. When polishing with a two-component CMP polishing solution, the cerium oxide slurry and additive solution are sent through separate pipes, and these pipes are joined just before the supply pipe outlet to mix the two solutions and polish the polishing. A method of supplying on a board or a method of mixing a cerium oxide slurry and an additive solution immediately before polishing can be used.

  The CMP polishing liquid used in the polishing method according to the present invention can be adjusted to a desired pH and used for polishing. Although there is no restriction | limiting in particular as a pH adjuster, Alkali metals, ammonia water, and an acid component are mentioned. When the CMP polishing liquid is used for semiconductor polishing, ammonia water and an acid component are preferably used rather than alkali metals. As the pH adjuster, an ammonium salt of a water-soluble polymer that has been partially neutralized with ammonia in advance can be used.

  The pH of the CMP polishing liquid is 4.5 to 7.0, preferably 4.5 to 6.0, and more preferably 4.9 to 5.5. If the pH is 4.5 or more, the storage stability of the CMP polishing liquid tends to be improved, and if it is 7.0 or less, the number of scratches on the film to be polished tends to decrease. The pH of the CMP polishing liquid can be measured with a pH meter (for example, trade name: Model PH81 manufactured by Yokogawa Electric Corporation). For example, after calibrating two points using a standard buffer solution (phthalate pH buffer solution pH: 4.21 (25 ° C.), neutral phosphate pH buffer solution pH: 6.86 (25 ° C.)), the electrode In a CMP polishing liquid, and the value after 2 minutes or more has been stabilized is measured.

  In the method for polishing a substrate according to the present invention, the CMP polishing liquid is applied between the film to be polished and the polishing pad in a state where the film to be polished on the substrate on which the film to be polished is pressed against the polishing pad of the polishing surface plate. While supplying, the film to be polished is polished by relatively moving the substrate and the polishing surface plate.

  As a substrate, a substrate related to semiconductor element manufacture, for example, a substrate having a circuit element and a wiring pattern formed thereon, a substrate having an inorganic insulating film formed on a semiconductor substrate such as a semiconductor substrate in which a circuit element is formed, etc. Is mentioned. Examples of the film to be polished include an inorganic insulating film such as a silicon oxide film or a composite film of a silicon nitride film and a silicon oxide film. By polishing the inorganic insulating film formed on such a semiconductor substrate with the CMP polishing liquid used in the polishing method according to the present invention, unevenness on the surface of the inorganic insulating film is eliminated, and the entire surface of the semiconductor substrate is smooth. It can be a surface. Further, the CMP polishing liquid used in the polishing method according to the present invention can also be used for shallow trench isolation.

  Hereinafter, the method for polishing a substrate will be described in more detail by taking the case of a semiconductor substrate on which an inorganic insulating film is formed as an example.

  The polishing apparatus generally includes a holder for holding a substrate having a film to be polished, such as a semiconductor substrate, and a polishing surface plate to which a motor capable of changing the number of rotations is attached and a polishing pad can be attached. A simple polishing apparatus can be used. As a polishing apparatus, for example, a polishing apparatus manufactured by Ebara Corporation, model number: EPO-111, or the like can be used.

  As the polishing pad, a general nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used without particular limitation. Further, it is preferable that the polishing pad is grooved so as to collect the CMP polishing liquid.

  The polishing conditions are not limited, but the rotation speed of the surface plate is preferably low rotation of 200 rotations / minute or less so that the semiconductor substrate does not pop out, and the pressure (working load) applied to the semiconductor substrate is scratched after polishing. 100 kPa or less is preferable. During polishing, a CMP polishing liquid is continuously supplied onto the polishing pad by a pump or the like. Although the supply amount is not limited, it is preferable that the surface of the polishing pad is always covered with a CMP polishing liquid.

  The semiconductor substrate after polishing is preferably washed in running water, and then dried by removing water droplets adhering to the semiconductor substrate using a spin dryer or the like.

  By polishing the inorganic insulating film, which is the film to be polished, with the CMP polishing liquid in this way, surface irregularities are eliminated and a smooth surface can be obtained over the entire surface of the semiconductor substrate. After the planarized shallow trench is formed, an aluminum wiring is formed on the inorganic insulating film, an inorganic insulating film is formed again between and on the wiring, and the inorganic insulating film is then formed using a CMP polishing liquid. To obtain a smooth surface. By repeating this step a predetermined number of times, a semiconductor substrate having a desired number of layers can be manufactured.

  Examples of the inorganic insulating film polished by the CMP polishing liquid according to this embodiment include a silicon oxide film and a silicon nitride film. The silicon oxide film may be doped with an element such as phosphorus or boron. As a method for manufacturing the inorganic insulating film, a low pressure CVD method, a plasma CVD method, or the like can be given.

The silicon oxide film formation by the low pressure CVD method uses monosilane: SiH ₄ as the Si source and oxygen: O ₂ as the oxygen source. A silicon oxide film can be obtained by performing this SiH ₄ —O ₂ -based oxidation reaction at a low temperature of 400 ° C. or lower. In some cases, the silicon oxide film obtained by CVD is heat-treated at a temperature of 1000 ° C. or lower. In order to planarize the surface by high-temperature reflow, when doping silicon: P with phosphorus: P, it is preferable to use a SiH ₄ —O ₂ —PH ₃ -based reactive gas.

The plasma CVD method has an advantage that a chemical reaction requiring a high temperature can be performed at a low temperature under normal thermal equilibrium. There are two plasma generation methods, capacitive coupling type and inductive coupling type. The reaction gases, SiH ₄ as an Si source, an oxygen source as _{N 2} O was used was _SiH 4 -N ₂ O-based gas and TEOS-O-based gas using tetraethoxysilane (TEOS) in an Si source (TEOS-plasma CVD method). The substrate temperature is preferably 250 to 400 ° C., and the reaction pressure is preferably 67 to 400 Pa.

Silicon nitride film formation by the low pressure CVD method uses dichlorosilane: SiH ₂ Cl ₂ as a Si source and ammonia: NH ₃ as a nitrogen source. This SiH ₂ Cl ₂ —NH ₃ -based oxidation reaction can be obtained by carrying out at a high temperature of 900 ° C. In the formation of a silicon nitride film by the plasma CVD method, examples of the reactive gas include SiH ₄ —NH ₃ based gas using SiH ₄ as the Si source and NH ₃ as the nitrogen source. The substrate temperature is preferably 300 to 400 ° C.

  The CMP polishing liquid and the substrate polishing method according to the present embodiment can be applied not only to the inorganic insulating film formed on the semiconductor substrate but also to manufacturing processes of various semiconductor devices. The CMP polishing liquid and the substrate polishing method according to the present embodiment include, for example, a silicon oxide film formed on a wiring board having a predetermined wiring, an inorganic insulating film such as glass and silicon nitride, polysilicon, Al, Cu, and Ti. , TiN, W, Ta, TaN and other films, optical glasses such as photomasks, lenses, and prisms, inorganic conductive films such as ITO (indium tin oxide), glass, and crystalline integrated circuits Optical switching elements, optical waveguides, optical fiber end faces, scintillator and other optical single crystals, solid state laser single crystals, blue laser LED sapphire substrates, SiC, GaP, GaAs and other semiconductor single crystals, magnetic disk glass substrates, magnetic It can also be applied to polishing a head or the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not restrict | limited to these Examples.

(Production of cerium oxide powder)
Commercially available cerium carbonate hydrate: 40 kg was placed in an alumina container and baked in air at 830 ° C. for 2 hours to obtain 20 kg of yellowish white powder. When the phase of this powder was identified by X-ray diffraction, it was confirmed that the powder was cerium oxide. The obtained cerium oxide powder: 20 kg was dry pulverized using a jet mill to obtain powdered cerium oxide.

Example 1
The cerium oxide prepared above: 200.0 g and deionized water: 795.0 g were mixed, and an aqueous solution of ammonium polyacrylate (weight average molecular weight: 8000, 40% by mass): 5 g was added with stirring. Ultrasonic dispersion was performed to obtain a cerium oxide dispersion. The ultrasonic dispersion was performed at an ultrasonic frequency of 400 kHz and a dispersion time of 20 minutes.

  Thereafter, 1 kg of a cerium oxide dispersion was placed in a 1 liter container (height: 170 mm) and allowed to stand to perform sedimentation classification. Classification time: After 15 hours, the supernatant above a depth of 130 mm from the water surface was pumped up. The obtained supernatant cerium oxide dispersion was then diluted with deionized water to obtain a cerium oxide slurry so that the solid content concentration was 5% by mass.

  In order to measure the average particle diameter (D50) of cerium oxide in the cerium oxide slurry, the slurry was diluted so that the transmittance (H) at the time of measurement with respect to the He—Ne laser was 60 to 70%. did. When this measurement sample was measured using a laser diffraction particle size distribution meter manufactured by Malvern, trade name: Master Sizer Microplus, with a refractive index of 1.93 and an absorption of 0, the value of D50 was 200 nm.

  P-Toluenesulfonic acid: 0.83 g as an organic acid, and polyacrylic acid (weight average molecular weight: 4000, solid content: 40% by mass): 10 g and deionized water: 9000 g as a polymer compound are mixed to obtain 25 mass. % Aqueous ammonia was added to adjust the pH to 4.5. In addition, pH was measured using a pH meter (trade name: Model PH81 manufactured by Yokogawa Electric Corporation), standard buffer solution (phthalate pH buffer solution pH: 4.21 (25 ° C.), neutral phosphate. After calibrating two points using a pH buffer solution (pH: 6.86 (25 ° C.)), the electrode was placed in the measurement object, and the value after 2 minutes had passed and stabilized was measured. After adding 660 g of the cerium oxide slurry, an aqueous ammonia solution was added again to adjust the pH to 5.0. Finally, in order to adjust the concentration, deionized water was added so that the total amount became 10,000 g to obtain a CMP polishing liquid.

  Further, a measurement sample was prepared in the same manner as described above, and the average particle size of the particles in the CMP polishing liquid was measured with a laser diffraction particle size distribution meter. As a result, the value of D50 was 200 nm.

(Insulating film polishing)
As a polishing test wafer, trade name: pattern wafer 864 (diameter: 200 mm) manufactured by SEMATECH and TEOS blanket wafer (diameter: 200 mm, initial film thickness: 1000 nm) manufactured by Advantech Co., Ltd. were used. A pattern wafer 864 and a polishing characteristic evaluation method using the pattern wafer 864 will be described with reference to FIG.

  FIG. 1A is a schematic cross-sectional view in which a part of the wafer 2 is enlarged. A plurality of grooves are formed on the surface of the wafer 2, and a silicon nitride film 1 having a thickness of 150 nm is formed on the surface of the convex portion of the wafer 2. The depth of the groove (depth from the surface of the convex portion to the bottom surface of the concave portion) is 500 nm. Hereinafter, the convex portion is referred to as an active portion, and the concave portion is referred to as a trench portion. The wafer 2 has a trench / active part of 100 μm / 100 μm and a trench / active part of 20 μm / 80 μm and 80 μm / 20 μm.

  FIG. 1B is an enlarged schematic cross-sectional view of a part of the polishing test wafer. In the polishing test wafer, the silicon oxide film 3 is formed in the active region and the trench portion by the plasma TEOS method so that the thickness of the silicon oxide film 3 from the surface of the active region becomes 600 nm. In the polishing test, the silicon oxide film 3 of the polishing test wafer is polished and planarized.

  FIG. 1C is a schematic cross-sectional view showing an enlarged part of a polishing test wafer after polishing the silicon oxide film 3. Polishing is finished on the surface of the silicon nitride film 1 in the active region, and the dishing amount 6 is a value obtained by subtracting the thickness 5 of the silicon oxide film 3 in the trench portion from the depth 4 of the trench portion at this time. The dishing amount 6 should be small.

A polishing apparatus (manufactured by Ebara Corporation, model number: EPO-111) was used for polishing the polishing test wafer. A polishing test wafer was set in a holder on which a suction pad for mounting the substrate was attached. A polishing pad (groove shape = XY-Performation, manufactured by Rohm and Haas, model number: IC1000 / Suba400) was attached to a polishing platen having a diameter of 600 mm of the polishing apparatus. Further, the holder was placed on a polishing surface plate with the insulating film (silicon oxide film) surface, which is a film to be polished, facing down, and the processing load was set to 350 gf / cm ² (34.3 kPa).

  While the cerium oxide CMP polishing solution is dropped on the polishing platen at a rate of 300 ml / min, the polishing platen and the polishing test wafer are operated at 60 revolutions / min. Polishing was performed until the film thickness of the active part in the active part / trench part of 100 μm / 100 μm existing in the substrate became 600 nm to 0 nm. The polished test wafer after polishing was thoroughly washed with ammonia water and pure water and then dried.

  About the polishing test wafer after polishing, the remaining film thickness of the trench part in the active part / trench part of 100 μm / 100 μm is measured using an interference-type film thickness measuring device manufactured by Nanometrics, Inc., trade name: Nanospec / AFT5100 The dishing amount was evaluated.

  The TEOS blanket wafer was polished under the same conditions as the pattern wafer 864 except that the polishing time was 60 seconds, and the polishing rate was calculated from the amount of decrease in film thickness.

  In Examples 2 to 11 and Comparative Examples 1 to 5, CMP polishing liquids were prepared by adjusting the polyacrylic acid amount and pH so that the concentrations shown in Table 1 were obtained by the same operation as in Example 1. The amount of cerium oxide slurry and the amount of p-toluenesulfonic acid are all constant. These CMP polishing liquids were subjected to a polishing test in the same manner as the CMP polishing liquid of Example 1, and the dishing amount and polishing rate were measured.

  As shown in Table 1, in Examples 1 to 11, it is clear that the dishing amount is smaller than Comparative Examples 1, 2 and 4 while maintaining a polishing rate of 180 nm / min or more and a sufficient polishing rate. It was confirmed that the flatness of the surface after polishing can be improved by the polishing method of the invention.

DESCRIPTION OF SYMBOLS 1 Silicon nitride film 2 Wafer 3 Silicon oxide film 4 Depth of trench part 5 Thickness of silicon oxide film in trench after polishing 6 Dishing amount

Claims (9)

A polishing method in which at least a part of a film to be polished provided on a substrate is removed by polishing using a CMP polishing liquid containing cerium oxide, an organic acid A, a polymer compound B and water and a polishing pad C. ,
The organic acid A includes a —COOM group, a —Ph—OM group, a —SO ₃ M group, a —OSO ₃ H group, a —PO ₄ M ₂ group, and a —PO ₃ M ₂ group (wherein M is H, NH ₄ , an organic acid having at least one group selected from the group consisting of any one selected from Na and K, and Ph representing a phenyl group which may have a substituent.
The polymer compound B is a polymer compound having a carboxyl group,
The CMP polishing liquid has a pH of 4.5 to 7.0,
The content of the polymer compound B is 0.01 to 0.30% by mass with respect to the total mass of the polishing liquid,
The polishing pad C is formed with a plurality of grooves and a plurality of holes.
Polishing method.   While the polishing film of the substrate on which the film to be polished is pressed against the polishing pad, the substrate and the polishing pad are moved relatively while supplying the CMP polishing liquid between the film to be polished and the polishing pad. The polishing method according to claim 1, wherein the film to be polished is polished.   The groove is composed of an X groove composed of a plurality of grooves parallel to each other on the polishing pad plane, and a Y groove composed of a plurality of grooves perpendicular to the X groove on the polishing pad plane. The polishing method according to claim 1, further comprising an XY groove.   The polishing method according to claim 3, wherein the plurality of X grooves on the polishing pad are provided with a plurality of grooves at equal intervals.   The polishing method according to claim 3 or 4, wherein each of the plurality of X grooves and Y grooves on the polishing pad is provided with a plurality of grooves at equal intervals.   6. The polishing method according to claim 5, wherein the polishing pad has a lattice-like groove in which the interval between the X grooves and the interval between the Y grooves are formed to be equal.   The polishing method according to claim 1, wherein the film to be polished is a film containing silicon oxide.   The polishing film according to claim 1, wherein the film to be polished is a film containing silicon oxide formed on a circuit element and / or a wiring pattern on a substrate or formed in a shallow trench isolation layer. Method.   The polishing method according to any one of claims 1 to 8, wherein the content of the organic acid A is 0.0001 to 5% by mass based on the total mass of the polishing liquid.

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