JP2015023122A - Polishing liquid and production method therefor, and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid having small dependency on the wiring and excellent in surface planarity and over-polishing tolerance after polishing, CMP technique for polishing a polished film formed on the surface of a substrate.SOLUTION: A polishing liquid contains cerium oxide particles, an acrylic acid-based polymer, an organic compound, a pH adjustment agent, and water. The acrylic acid-based polymer is obtained by polymerizing monomer components containing at least one kind selected from acrylic acid and methacrylic acid. The polymer has at least one kind selected from a group consisting of nitric acid group, a nitric acid base, a nitrous acid group, and a nitrous acid base, as a terminal group, and the pH is 4.0-5.5.

Description

  The present invention relates to a polishing liquid, a method for producing the same, and a polishing method. More specifically, the present invention relates to a polishing liquid for polishing a substance used as an insulating material, a manufacturing method thereof, and a polishing method.

  In the current ULSI semiconductor device manufacturing process, processing technology for high density and miniaturization of semiconductor devices has been researched and developed. One of the processing techniques, planarization technology by CMP (Chemical Mechanical Polishing), is a planarization of an interlayer insulating film, a STI (Shallow Trench Isolation) formation process in a semiconductor element manufacturing process, It has become an indispensable technique when performing a plug formation process, a buried metal wiring formation process (damascene process), and the like. In the CMP process (planarization process using the CMP technique), the polishing material is generally polished while supplying a polishing slurry for CMP between the polishing pad (polishing cloth) and the polishing material on the substrate. Is done by.

  Various polishing liquids for CMP used in the CMP are known. When classified according to abrasive grains (polishing particles) contained in the polishing liquid for CMP, a ceria-based polishing liquid containing cerium oxide (ceria) particles as abrasive grains, a silica-based polishing liquid containing silicon oxide (silica) particles as abrasive grains, and An alumina-based polishing liquid containing aluminum oxide (alumina) particles as abrasive grains, a resin particle-based polishing liquid containing organic resin particles as abrasive grains, and the like are known.

  As a polishing liquid for polishing an insulating material such as silicon oxide in a semiconductor element manufacturing process, a ceria-based polishing liquid has attracted attention because it has a higher polishing rate for an inorganic insulating material than a silica-based polishing liquid. .

  As a ceria-based polishing liquid, the following Patent Document 1 describes a semiconductor CMP polishing liquid using high-purity cerium oxide abrasive grains. Patent Document 2 listed below describes a technique of adding a polymer additive to control the polishing rate of a ceria-based polishing liquid and improve global flatness. Patent Document 3 below discloses a polymer obtained by polymerizing a monomer containing at least one of a carboxylic acid having an unsaturated double bond and a salt thereof using a reducing inorganic acid salt and oxygen as a redox polymerization initiator. It is described that by using coalescence as an additive, it is possible to achieve uniform polishing with little influence due to the difference in density of wiring patterns.

Japanese Patent Laid-Open No. 10-106994 Japanese Patent No. 3278532 International Publication No. 2008/032794

  The technique described in Patent Document 3 is said to be able to reduce the dependency on the wiring density by uniformly polishing the wirings having different densities. However, in recent years, with the progress of miniaturization of design rules of wiring and STI, further improvement of characteristics is required for ceria-based polishing liquid. One of such characteristics is improvement of flatness, and as an indicator thereof, reduction of dishing (a phenomenon in which a part of the surface after polishing is dented like a dish) is required.

  In recent years, in the STI formation, over-polishing is sometimes performed in order to completely remove the silicon oxide film in the convex portion (active portion). At that time, polishing of the silicon oxide film in the concave portion (trench portion) also proceeds. It is easy to end up. Therefore, improvement of over-polishing resistance (no polishing of the silicon oxide film in the recess (trench) during over-polishing) is also required.

  The present invention has been made to solve the above problems, and in CMP technology for polishing a film to be polished formed on the surface of a substrate, the dependency on the surface flatness after polishing and the dependence on wiring density are small. It aims at providing the polishing liquid which is excellent in over-polishing tolerance.

  The method for producing a polishing liquid according to the present invention comprises a step of obtaining a polishing liquid by mixing particles containing cerium oxide, an acrylic acid polymer, an organic acid compound, a pH adjuster, and water, The acrylic acid polymer is a polymer obtained by polymerizing a monomer component containing at least one selected from the group consisting of acrylic acid and methacrylic acid, and the polymer is a nitrate group, nitrate group, nitrous acid The polishing liquid has at least one selected from the group consisting of a group and a nitrite group as a terminal group, and the polishing liquid has a pH of 4.0 or more and 5.5 or less.

  According to the polishing liquid, in the CMP technique for polishing a film to be polished (for example, an interlayer insulating film, a BPSG film (boron, silicon dioxide film doped with phosphorus), an STI film) formed on the surface of the substrate, Wiring density dependency can be reduced, over-polishing resistance can be improved, and surface flatness after polishing can be improved.

  The blending amount of the acrylic acid polymer is preferably 0.001 to 2% by mass with respect to the total mass of the polishing liquid.

  The acrylic acid polymer may be a homopolymer of acrylic acid or methacrylic acid, a copolymer of acrylic acid and methacrylic acid, and another copolymerizable monomer of acrylic acid or methacrylic acid It may be at least one selected from the group consisting of copolymers.

  The polymer may have a nitrate or nitrite group as a terminal group.

  A polishing liquid according to the present invention is a polishing liquid for removing at least a part of an insulating material by CMP, and includes particles containing cerium oxide, an acrylic acid polymer, an organic acid compound, and a pH adjuster. Water, and an acrylic acid polymer is a polymer obtained by polymerizing at least one selected from the group consisting of acrylic acid and methacrylic acid, and the polymer is a nitrate group, nitrate group, nitrous acid And at least one selected from the group consisting of a group and a nitrite group as a terminal group.

  The pH of the polishing liquid according to the present invention is preferably 4.0 to 5.5.

  According to the present invention, it is possible to improve surface flatness after polishing in a substrate surface flattening step, which is a semiconductor element manufacturing technique, in particular, a CMP technique for flattening an interlayer insulating film, a BPSG film, and an STI film. A possible polishing liquid and a method for polishing a substrate using the polishing liquid can be provided.

It is a schematic cross section showing an example of a polishing method according to the present invention.

  One embodiment of the method for producing a polishing liquid of the present invention comprises a step of obtaining abrasive grains containing cerium oxide particles and a monomer component containing at least one selected from the group consisting of acrylic acid compounds and methacrylic acid compounds. And a step of obtaining a polishing liquid by mixing the abrasive grains, the acrylic acid polymer, an organic acid compound, and water. The polishing liquid has at least one selected from the group consisting of nitrate group, nitrate group, nitrite group and nitrite group as a terminal group, and the polishing liquid has a pH of 4.0 or more and 5.5 or less. It is a manufacturing method. Hereinafter, embodiments of the present invention will be described in detail.

(1. Step of obtaining an acrylic acid polymer)
In the embodiment of the present invention, the acrylic acid polymer is a polymer obtained by polymerizing a monomer component containing at least one selected from the group consisting of acrylic acid and methacrylic acid. The monomer component may contain other monomers (excluding acrylic acid and methacrylic acid) that can be copolymerized with acrylic acid or methacrylic acid.

  Examples of the acrylic polymer include a homopolymer of acrylic acid (polyacrylic acid), a homopolymer of methacrylic acid (polymethacrylic acid), a copolymer of acrylic acid and methacrylic acid, acrylic acid or methacrylic acid and It may be at least one selected from the group consisting of a copolymer with the other monomer, a copolymer of acrylic acid and methacrylic acid and the other monomer. In particular, the acrylic acid polymer is preferably an acrylic acid homopolymer (polyacrylic acid) from the viewpoint of good adsorption to a film to be polished (for example, interlayer insulating film, BPSG film, STI film). In addition, an acrylic acid polymer can be used individually by 1 type or in combination of 2 or more types.

  Examples of the other monomer (a monomer copolymerizable with acrylic acid or methacrylic acid) include, for example, crotonic acid, pentenoic acid, hexenoic acid, heptenoic acid, octenoic acid, nonenoic acid, decenoic acid, and undecene. Examples thereof include unsaturated carboxylic acids such as acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid and heptadecenoic acid; vinyl compounds such as ethylene, propylene and styrene.

  In the method for producing a polishing liquid of the present invention, the polymer has at least one selected from the group consisting of nitrate group, nitrate group, nitrite group and nitrite group as a terminal group. Examples of the nitrate base include ammonium nitrate base, potassium nitrate base, and sodium nitrate base. Examples of the nitrite base include diammonium nitrite base, dipotassium nitrite base, and disodium nitrite base.

  The terminal group is preferably a nitrate group or a nitrate group, more preferably a nitrate group, and more preferably at least one selected from the group consisting of an ammonium nitrate group, a sodium nitrate group and a potassium nitrate group, Ammonium nitrate base is particularly preferred.

  As a method for obtaining a polymer having as a terminal group at least one selected from the group consisting of nitrate groups and nitrite groups, using at least one polymerization initiator selected from the group consisting of nitrates and nitrites, A method of polymerizing the monomer component is preferred.

  Examples of the polymerization initiator that is nitrate include 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] nitrate, 2,2′-azobis [2- (2- Imidazolin-2-yl) propane] nitrate, 2,2'-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] nitrate, 2,2'-azobis [2-amidinopropane Nitrate, and in particular, 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] nitrate, 2,2 'because of its good reactivity at low temperatures. -Azobis [2- (2-imidazolin-2-yl) propane] nitrate is preferred.

  Examples of the polymerization initiator that is the nitrite include 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] nitrite, 2,2′-azobis [2- ( 2-Imidazolin-2-yl) propane] nitrite, 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] nitrite, 2,2′-azobis [ 2-amidinopropane] nitrite, and 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] nitrite in that the reactivity is good even at low temperatures. 2,2'-azobis [2- (2-imidazolin-2-yl) propane] nitrite is preferred.

(2. Step of obtaining cerium oxide particles)
There is no restriction | limiting in particular as a cerium oxide particle, A well-known thing can be used. Among these, cerium oxide particles are preferably obtained by oxidizing cerium salts such as carbonates, nitrates, sulfates, and oxalates. Examples of the oxidation method include a firing method in which the cerium salt is fired at 600 to 900 ° C., a chemical oxidation method in which the cerium salt is oxidized using an oxidizing agent such as hydrogen peroxide, and the like. preferable.

  When cerium oxide particles are used for polishing a silicon oxide film formed by TEOS-CVD using tetraethoxysilane (TEOS) as a Si source, the crystallite diameter (crystallite diameter) of the cerium oxide particles is large. In addition, the smaller the crystal distortion (that is, the better the crystallinity), the faster the polishing is possible, but the material to be polished tends to be subject to polishing scratches. 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 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. If the average particle size of the cerium oxide particles is 10 nm or more, a good polishing rate tends to be obtained, and if it is 500 nm or less, the material to be polished tends to be hardly damaged.

  Here, the average particle diameter of the cerium oxide particles was measured with a laser diffraction particle size distribution meter (for example, product name: LA-920, refractive index: 1.93, light source: He—Ne laser, absorption 0, manufactured by Horiba Seisakusho). It means the value of D50 (median diameter of volume distribution, cumulative median value). For the measurement of the average particle diameter, a sample in which the polishing liquid is diluted 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 polishing liquid containing cerium oxide particles is stored separately in a cerium oxide slurry in which cerium oxide particles are dispersed in water and an additive liquid, measurement is performed by diluting the cerium oxide slurry to an appropriate concentration. can do.

  It is preferable that the manufacturing method of the polishing liquid according to this embodiment includes a dispersion step of abrasive grains containing the cerium oxide particles. In the dispersion step, the abrasive grains containing the cerium oxide particles, the dispersant, and water are mixed to disperse the abrasive grains containing the cerium oxide particles in water to obtain a cerium oxide slurry. The blending amount of the dispersant is adjusted so that a polishing liquid having the above-described content of the dispersant is obtained, and is preferably 0.001 to 4% by mass with respect to the total mass of the abrasive grains including the cerium oxide particles.

  In addition, the manufacturing method of the polishing liquid which concerns on this embodiment may contain another kind of particle | grain within the range which does not impair the characteristic of polishing liquid, For example, a silica, an alumina, and a zirconia are mentioned.

(3. Step of obtaining polishing liquid)
One of the embodiments of the polishing liquid production method of the present invention is a process of obtaining a polishing liquid by mixing abrasive grains containing cerium oxide particles, an organic acid compound, the acrylic polymer, and water. .

  In the manufacturing method of the polishing liquid of this embodiment, the constituents of the polishing liquid may be stored in two or more liquids so as to be the polishing liquid. For example, it is divided into a cerium oxide slurry containing cerium oxide particles and water, an additive containing other components (for example, an acrylic acid polymer, an organic acid compound and water), and an additive solution containing water. You may obtain a polishing liquid by preserve | saving and mixing both.

  The method for producing a polishing liquid of the present embodiment may further include a step of mixing a dispersant. In this case, the dispersant is preferably added in the step of obtaining the cerium oxide slurry. That is, the cerium oxide slurry preferably contains a dispersant.

  Examples of the dispersant include a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant, and a water-soluble amphoteric dispersant. Among them, the electrostatic repulsion is large and the dispersibility is good. Therefore, a water-soluble anionic dispersant is preferable.

  The content of the cerium oxide particles in the polishing liquid is preferably 0.1 to 20% by mass, more preferably 0.1 to 15% by mass, and still more preferably 0.5 to 10% by mass based on the total mass of the polishing liquid. If the content of the cerium oxide particles is 0.1% by mass or more, a good polishing rate tends to be obtained. If the content is 20% by mass or less, the aggregation of particles is suppressed and the material to be polished is damaged. There is a tendency to become difficult.

(Organic acid compound)
The polishing liquid according to this embodiment contains at least one selected from the group consisting of organic acids and salts thereof as the organic acid compound. Thereby, the polishing rate of the curtain to be polished is improved, and the flatness of the material to be polished (for example, silicon oxide film) after polishing is easily improved. More specifically, in addition to shortening the polishing time when polishing a surface to be polished having irregularities, it becomes easy to suppress the phenomenon that a part is excessively polished and recessed like a dish, so-called dishing. .

The organic acid compound is at least selected from the group consisting of a —COOM group, a phenolic —OM group, a —SO ₃ M group, a —O · SO ₃ H group, a —PO ₄ M ₂ group, and a —PO ₃ M ₂ group. A water-soluble organic compound having one type (M is H, NH ₄ , Na or K) is preferable. Specific examples of the organic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, o-toluic acid, m-toluic acid, p-toluic acid, o-methoxybenzoic acid. , M-methoxybenzoic 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, tetradecene Acid, pentadecenoic acid, hexadecenoic acid, heptadecenoic acid, isobutyric acid, isovaleric acid, 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, glucose Phosphoric 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, 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, quinolinic acid Quinic acid, naphthalic acid, phthalic acid, isophthalic acid, terephthalic 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, aconi Tolic acid, ascorbic acid, acetylsalicylic acid, acetylmalic acid, acetylenedicarboxylic acid, acetoxysuccinic acid, acetoacetic acid, 3-oxoglutaric acid, atropic acid, atrolactic acid, anthraquinonecarboxylic acid, anthracenecarboxylic acid, isocaproic acid, isocamphoronic 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 , Desoxalic acid, Tetrahydroxysuccinic acid, Tetramethylsuccinic acid, Tetronic acid, Dehydroacetic acid, Television acid, Tropaic acid, Vanillic acid, Paraconic acid, Hydroxyisophthalic acid, Hydroxycinnamic acid, Hydroxynaphthoic acid, o-Hydroxyphenyl Acetic 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, phenylacetic acid, phenyllactic acid, propiolic acid, sorbic acid, 2,4-hexadienedioic acid, 2-benzylidenepropionic acid, 3-benzylidenepropionic acid, benzylidenemalonic acid, benzylic acid, benzenetricarboxylic acid, 1,2 − Zendiacetic 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-methylsilicic acid Cinnamic 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, Rhodonic acid, rosoleic acid, α-ketoglutaric acid, L-alcorbic acid, iduronic acid, galacturonic acid, glucuronic acid, pyroglutamic acid, ethylenediaminetetraacetic acid, triacetic acid cyanide, aspartic acid, glutamic acid, N′-hydroxyethyl-N, N, N'-triacetic acid, nitrilo Carboxylic acids such as Li acetate;
phenols such as o-aminophenol, m-aminophenol, p-aminophenol;
Methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, heptanesulfonic acid, octanesulfonic acid, nonanesulfonic acid, decanesulfonic acid, undecanesulfonic acid, dodecanesulfonic acid, tridecane Sulfonic acid, tetradecanesulfonic acid, pentadecanesulfonic acid, hexadecanesulfonic acid, heptadecanesulfonic acid, octadecanesulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid, toluenesulfonic acid, hydroxyethanesulfonic acid, hydroxyphenolsulfonic acid, anthracenesulfonic acid, etc. Sulfonic acids of
Phosphonic acids such as decylphosphonic acid and phenylphosphonic acid are preferred.

In addition, a derivative in which one or more protons in the main chain of the above carboxylic acid, sulfonic acid, and phosphonic acid are substituted with atoms or atomic groups such as F, Cl, Br, I, OH, CN, NO _2, etc. There may be.

  These organic acid compounds can be used alone or in combination of two or more.

  The content of the organic acid compound is preferably 0.001 to 2% by mass, more preferably 0.005 to 1% by mass, and still more preferably 0.01 to 0.5% by mass with respect to the total mass of the polishing liquid. If the content of the organic acid compound is 0.001% by mass or more, the flatness of the material to be polished (eg, silicon oxide film) after polishing tends to be improved, and if it is 1% by mass or less, There is a tendency to sufficiently improve the polishing rate of the material to be polished.

  The pKa of the organic acid compound is preferably less than 9, more preferably less than 8, further preferably less than 7, particularly preferably less than 6, and extremely preferably less than 5. . If the pKa of the organic acid compound is less than 9, at least part of the organic acid compound becomes an organic acid ion in the polishing liquid, and hydrogen ions are released, making it easy to maintain the pH in a desired pH region.

  0.001 mass% or more is preferable with respect to the total mass of polishing liquid, 0.001 mass% or more is more preferable, and 0.1 mass% or more is still more preferable. The content of the dispersant is preferably 2% by mass or less, more preferably 1% by mass or less, and still more preferably 0.5% by mass or less with respect to the total mass of the polishing liquid. If the content of the acrylic acid polymer is 0.001% by mass or more and 2% by mass or less, the dishing amount, wiring density dependency, etc. can be reduced, and the surface flatness after polishing can be improved. .

  Although there is no restriction | limiting in particular in the weight average molecular weight of an acrylic acid polymer, 100-150,000 are preferable and 1000-80000 are more preferable. When the weight average molecular weight of the acrylic polymer is 100 or more, a good polishing rate tends to be easily obtained when polishing a material to be polished such as a silicon oxide film or a silicon nitride film. When the weight average molecular weight of the acrylic acid polymer is 150,000 or less, the storage stability of the polishing liquid tends to be difficult to decrease. In addition, a weight average molecular weight is the value converted into sodium polyacrylate, measured by a size exclusion chromatograph method using a calibration curve prepared with a sodium polyacrylate standard substance manufactured by Polymer Laboratories.

<Polishing liquid>
The polishing liquid according to the present embodiment is a polishing liquid for removing at least a part of the insulating material by CMP. The polishing liquid according to the present embodiment contains particles containing cerium oxide (hereinafter referred to as “cerium oxide particles”), an acrylic acid polymer, an organic acid compound, a pH adjuster, and water. The acrylic polymer is a polymer obtained by polymerizing at least one selected from the group consisting of acrylic acid and methacrylic acid, and the polymer comprises a nitrate group, a nitrate group, a nitrite group, and a nitrite group. It has at least one selected from the group as a terminal group, and has a pH of 4.0 or more and 5.5 or less. Hereinafter, each component contained in the polishing liquid according to the present embodiment will be described in detail.

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

(PH adjuster)
The polishing liquid according to this embodiment can be adjusted to a desired pH by adding a pH adjuster as necessary. The pH adjuster is not particularly limited, and examples thereof include acid components such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, boric acid, and acetic acid; and basic components such as sodium hydroxide, ammonia, potassium hydroxide, and calcium hydroxide. Can be mentioned. When the polishing liquid is used for semiconductor polishing, ammonia and an acid component are preferably used. As the pH adjuster, an ammonium salt of a water-soluble polymer that has been partially neutralized with ammonia in advance can also be used.

(PH)
The pH (25 ° C.) of the polishing liquid is preferably 4.0 to 5.5, more preferably 4.3 to 5.2. If the pH is 4.0 or more and 5.5 or less, surface flatness after polishing such as dishing amount and wiring density dependency can be improved.

  The pH of the polishing liquid can be measured using a pH meter (for example, Model PH81 (trade name) 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 Is put into a polishing liquid, and the value after being stabilized at 25 ° C. for 2 minutes or more is measured.

(Other additives)
The polishing liquid according to this embodiment can contain a compound other than the acrylic acid polymer, the pH adjuster, and the organic acid compound as an additive. Examples of such additives include water-soluble polymer compounds, water-soluble cationic compounds, water-soluble anionic compounds, water-soluble nonionic compounds, and water-soluble amphoteric compounds. When the polishing liquid is stored separately in the cerium oxide slurry and the additive liquid, these other additives are preferably included in the additive liquid.

  Examples of water-soluble polymer compounds include polysaccharides such as alginic acid, pectinic acid, carboxymethylcellulose, agar, curdlan and pullulan; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polyamic acid, polyamic acid ammonium salt, polyamic acid sodium salt Examples thereof include salts and polycarboxylic acids such as polyglyoxylic acid and salts thereof; vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone and polyacrolein.

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

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

  Examples of water-soluble nonionic compounds include polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, 2-hydroxyethyl Methacrylate, alkyl alkanolamide and the like can be mentioned.

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

  These additives can be used alone or in combination of two or more.

  The content of the other additives is preferably 0.01 to 5% by mass based on the total mass of the polishing liquid.

<Polishing method>
In the polishing method according to this embodiment, at least a part of the insulating material is removed by CMP using the polishing liquid. In the polishing method according to the present embodiment, for example, a substrate having an insulating material on the surface is polished (substrate polishing method). The polishing method according to the present embodiment includes, for example, a preparation process, a substrate arrangement process, and a polishing process. In the preparation step, a substrate having an insulating material on the surface is prepared. In the substrate placement step, the substrate is placed so that the insulating material faces the polishing cloth. In the polishing step, for example, at least a part of the insulating material is removed. In the polishing step, for example, a polishing liquid is supplied between the polishing cloth and the insulating material in a state where the insulating material of the substrate on which the insulating material is formed is pressed against the polishing cloth of the polishing surface plate, so that the substrate and the polishing plate are fixed. At least a part of the insulating material is polished by moving the board relatively. The shape of the insulating material is not particularly limited, and is, for example, a film shape (insulating film).

  As a substrate, an insulating material (for example, an inorganic insulating material) is provided on a semiconductor substrate such as a substrate related to semiconductor element manufacture, for example, a semiconductor substrate at a stage where a circuit element and a wiring pattern are formed, A substrate on which is formed. Examples of the insulating material include inorganic insulating materials such as a silicon oxide film, a silicon nitride film, and a composite film of a silicon oxide film. By polishing the insulating material formed on such a semiconductor substrate with the polishing liquid according to the present embodiment, unevenness on the surface of the insulating material can be eliminated, and a smooth surface can be obtained over the entire surface of the semiconductor substrate. Further, the polishing liquid according to this embodiment can also be used for STI.

  Hereinafter, the polishing method according to the present embodiment will be described in more detail by taking the case of a semiconductor substrate on which an insulating material is formed as an example. FIG. 1 is a schematic cross-sectional view showing an example of a polishing method. First, as shown in FIG. 1 (A), a substrate 100 having a wafer 1 having concave and convex portions formed on its surface and a silicon nitride film 2 formed on the convex portion of the wafer 1. Prepare. Next, as shown in FIG. 1B, a silicon oxide film 3 is deposited by plasma TEOS or the like so as to fill the irregularities on the surface of the wafer 1 to obtain a substrate 200.

  Then, using the polishing liquid, the silicon oxide film 3 is polished and removed until the silicon nitride film 2 on the convex portion of the wafer 1 is exposed. In the substrate after polishing, as shown in FIG. 1C, it is preferable that the dishing amount 6 that 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 is small. .

  The polishing apparatus generally includes a holder for holding a semiconductor substrate having a material to be polished and a polishing surface plate to which a motor capable of changing the number of rotations is attached and to which a polishing cloth (pad) can be attached. A typical polishing apparatus can be used. As the polishing apparatus, for example, model number: EPO-111 manufactured by Ebara Manufacturing Co., Ltd., and product names: MIRRA, Reflexion (“MIRRA” and “Reflexion” are registered trademarks) manufactured by Applied Materials, Inc. can be used.

  As the polishing cloth, a general nonwoven fabric, foamed polyurethane, porous fluororesin and the like can be used without particular limitation. Moreover, it is preferable that the polishing cloth is subjected to groove processing so that the polishing liquid is accumulated.

Although there is no limitation on polishing conditions, the rotation speed of the surface plate is preferably low rotation of 200 min ⁻¹ or less so that the semiconductor substrate does not pop out, and the pressure (working load) applied to the semiconductor substrate does not cause scratches after polishing. Thus, 100 kPa or less is preferable. During polishing, the polishing liquid is continuously supplied to the polishing cloth with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of polishing cloth is always covered with 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 insulating material, which is the material to be polished, with the polishing liquid in this manner, surface irregularities can be eliminated and a smooth surface can be obtained over the entire surface of the semiconductor substrate. After the flattened shallow trench is formed, aluminum wiring is formed on the insulating material, the insulating material is formed again between the wirings and on the wiring, and then the insulating material is polished using the polishing liquid. Get 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 insulating material polished by the polishing liquid according to the present embodiment include inorganic insulating materials such as 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 material, 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. A silicon nitride film is obtained by performing this SiH ₂ Cl ₂ —NH ₃ -based oxidation reaction 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 polishing liquid and the polishing method according to the present embodiment can be applied not only to the insulating material formed on the semiconductor substrate but also to various semiconductor device manufacturing processes. The polishing liquid and the 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 material such as glass and silicon nitride, polysilicon, Al, Cu, Ti, TiN, Optical integrated circuit / light composed of films mainly containing W, Ta, TaN, etc., optical glass such as photomask / lens / prism, inorganic conductive film such as ITO (indium tin oxide), glass and crystalline material Switching elements / optical waveguides, optical fiber end faces, optical single crystals such as scintillators, solid state laser single crystals, blue laser LED sapphire substrates, semiconductor single crystals such as SiC, GaP, and GaAs, glass substrates for magnetic disks, magnetic heads, etc. It can also be applied to polishing.

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

(Production of cerium oxide powder)
40 kg of commercially available cerium carbonate hydrate 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 the X-ray diffraction method, it was confirmed to be cerium oxide. 20 kg of the obtained cerium oxide powder was dry-ground using a jet mill to obtain a cerium oxide powder containing cerium oxide particles.

(Preparation of acrylic acid polymer)
(Preparation of polyacrylic acid A)
140 g of deionized water and 140 g of 2-propanol were put into a 1 liter synthesis flask equipped with a stirrer, a thermometer, and a nitrogen inlet, and the temperature was raised to 80 ° C. while stirring. A solution obtained by mixing 36 g of azobis [2- (imidazolin-2-yl) propane], 30 g of 60% by mass nitric acid and 168 g of deionized water was simultaneously added dropwise into the flask over 120 minutes in a nitrogen atmosphere. Thereafter, the mixture was stirred at 85 ° C. for 120 minutes, and then cooled to 40 ° C. or lower to adjust the non-volatile content to 40% by mass to obtain polyacrylic acid A (acrylic acid homopolymer) having a nitrate group at the terminal. The molecular weight of the obtained polyacrylic acid was measured by size exclusion chromatography using a calibration curve prepared with a sodium polyacrylate standard substance manufactured by Polymer Laboratories. The weight average molecular weight was 2400 (polyacrylic acid). Sodium equivalent value).

(Preparation of polyacrylic acid B)
250 g of deionized water was put into a 1 liter synthesis flask equipped with a stirrer, a thermometer and a nitrogen inlet, and the temperature was raised to 90 ° C. while stirring in a nitrogen gas atmosphere. Then, 130 g of acrylic acid and 2,2′- A solution prepared by dissolving 14 g of azobis [2- (2-imidazolin-2-yl) propane] sulfate in 130 g of methanol was poured into the flask over 2 hours. Thereafter, the mixture was kept at 90 ° C. for 3 hours, and then cooled to 40 ° C. or lower to adjust the non-volatile content to 40% by mass to obtain polyacrylic acid B (a homopolymer of acrylic acid) having a sulfate group at the terminal. When the molecular weight of the obtained polyacrylic acid was measured, the weight average molecular weight was 2500 (as converted to sodium polyacrylate).

Example 1
Mixing 200.0 g of the cerium oxide prepared above and 795.0 g of deionized water, adding 5 g of an ammonium polyacrylate aqueous solution (weight average molecular weight: 8000, 40% by mass) as a dispersing agent, and stirring. Ultrasonic dispersion was performed to obtain a cerium oxide dispersion. 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. After 15 hours of classification time, 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 measurement transmittance (H) with respect to the He—Ne laser was 60 to 70%, did. When this measurement sample was measured with a laser diffraction particle size distribution meter Mastersizer Microplus (product name of Malvern, trade name ("Mastersizer" is a registered trademark)) as a refractive index of 1.93 and absorption of 0, the value of D50 is It was 150 nm.

  2 g of p-toluenesulfonic acid as an organic acid compound and 700 g of deionized water are mixed, and an acrylic acid polymer is polyacrylic acid having a weight average molecular weight of 2400 and a terminal group of 40% by mass as a nitrate group (the above poly 6.25 g of acrylic acid A) aqueous solution was added, and aqueous ammonia (25% by mass) was added to adjust the pH to 4.5. Further, deionized water was added to make the total amount of 750 g as an additive solution.

  200 g of the above cerium oxide slurry is added, and ammonia water (25% by mass) is added to adjust the pH to 5.0. Further, deionized water is added to make the total amount 1000 g, and the polishing liquid (cerium oxide) Solid content: 1.0% by mass).

  Further, a measurement sample was prepared in the same manner as described above, and the average particle size of the particles in the polishing liquid was measured with a laser diffraction particle size distribution meter. As a result, the value of D50 was 150 nm.

(Insulating film polishing)
As the polishing test wafer, a trade name: pattern wafer 864 (diameter: 200 mm) manufactured by SEMATECH was used. The polishing test wafer and a method for evaluating polishing characteristics using the wafer will be described with reference to FIG.

  FIG. 1A is an enlarged schematic cross-sectional view of a part of the wafer 1. A plurality of grooves are formed on the surface of the wafer 1, and a silicon nitride film 2 having a thickness of 150 nm is formed on the convex surface of the wafer 1. The depth of the groove (step difference 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 1 is formed with trench / active portions of 100 μm / 100 μm, 20 μm / 80 μm, and 80 μm / 20 μm.

  FIG. 1B is an enlarged schematic cross-sectional view of a part of a 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 in which a part of a polishing test wafer after polishing the silicon oxide film 3 is enlarged. Polishing is completed on the surface of the silicon nitride film 2 in the active region, and the time required for polishing at this time is defined as polishing time, and a value obtained by subtracting the thickness 5 of the silicon oxide film 3 in the trench from the depth 4 of the trench. The dishing amount is 6. It should be noted that the polishing time should be shorter and the dishing amount 6 should be smaller.

  A polishing apparatus (manufactured by Applied Materials, trade name: MIRRA) 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 cloth made of porous urethane resin (groove shape = perforate type: manufactured by Rohm and Haas, model number: IC1010) was attached to the polishing surface plate of the polishing apparatus. Further, the holder was placed on the polishing surface plate with the insulating film (silicon oxide film) surface as the film to be polished facing down, and the processing load was set to 5 psi (about 34.5 kPa).

While dropping the ceria-based polishing liquid at a rate of 150 ml / min on the polishing platen, the polishing platen and the polishing test wafer were each operated at 90 min ⁻¹ to polish the polishing test wafer. The polished test wafer after polishing was thoroughly washed with pure water and then dried.

  With respect to the polished test wafer after polishing, the remaining film thickness of the 100 μm / 100 μm trench portion was measured using an interference type film thickness measuring device Nanospec / AFT5100 (trade name) manufactured by Nanometrics, and the dishing amount was evaluated.

  For the polished test wafer after polishing, the remaining film thickness of the 20 μm / 80 μm and 80 μm / 20 μm trench portions was measured with the above film pressure measuring device, and the absolute value of the difference between the remaining film thicknesses at the two locations was used as an index of wiring density dependency And the wiring density dependency was evaluated.

  The polished test wafer after polishing is subjected to additional polishing (over polishing) for 30% of the polishing time when the remaining film thickness of the active part of 100 μm / 100 μm becomes 0 mm, and the trench part of 100 μm / 100 μm at the time of over polishing is subjected to The polishing rate of the silicon oxide film was defined as over-polishing resistance, and over-polishing resistance was evaluated.

(Examples 2-3 and Comparative Examples 1-3)
A ceria-based polishing liquid was prepared so that the blending amount and pH shown in Table 1 were obtained in the same manner as in Example 1. The evaluation results are shown in Table 1. From Table 1, it became clear that the polishing liquid provided by the present invention achieves improved dishing, wiring density dependency and over-polishing resistance.

  DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Silicon nitride film, 3 ... Silicon oxide film, 4 ... Groove depth of trench part, 5 ... Trench part silicon oxide film thickness after grinding | polishing, 6 ... Dishing amount.

Claims (12)

A method for producing a polishing liquid comprising a step of mixing a particle containing cerium oxide, an acrylic acid polymer, an organic acid compound, a pH adjuster, and water to obtain a polishing liquid,
The acrylic acid polymer is a polymer obtained by polymerizing a monomer component containing at least one selected from the group consisting of acrylic acid and methacrylic acid,
The acrylic polymer has at least one selected from the group consisting of nitrate group, nitrate group, nitrite group and nitrite group as a terminal group,
The method for producing a polishing liquid, wherein the polishing liquid has a pH of 4.0 or more and 5.5 or less.   The manufacturing method of the polishing liquid of Claim 1 whose compounding quantity of an acrylic acid polymer is 0.001-2 mass% with respect to the total mass of polishing liquid.   The manufacturing method of the polishing liquid of Claim 1 or 2 whose acrylic acid polymer is a homopolymer of acrylic acid or methacrylic acid.   The acrylic polymer is at least one selected from the group consisting of a copolymer of acrylic acid and methacrylic acid, and a copolymer of acrylic acid or methacrylic acid and another copolymerizable monomer. The manufacturing method of the polishing liquid of Claim 1 or 2.   The method for producing a polishing liquid according to any one of claims 1 to 4, wherein the acrylic polymer has a nitrate group as a terminal group. A polishing liquid for removing at least a part of an insulating material by CMP,
Containing particles containing cerium oxide, an acrylic acid polymer, an organic acid compound, a pH adjuster, and water;
The acrylic acid polymer is a polymer obtained by polymerizing at least one selected from the group consisting of acrylic acid and methacrylic acid,
Polishing liquid in which the acrylic acid polymer has at least one selected from the group consisting of nitrate group, nitrate group, nitrite group and nitrite group as a terminal group.   The polishing liquid according to claim 6, wherein the content of the acrylic acid polymer is 0.001 to 2 mass% with respect to the total mass of the polishing liquid.   The polishing liquid according to claim 6 or 7, wherein the acrylic polymer is a homopolymer of acrylic acid or methacrylic acid.   The acrylic polymer is at least one selected from the group consisting of a copolymer of acrylic acid and methacrylic acid, and a copolymer of acrylic acid or methacrylic acid and another copolymerizable monomer. The polishing liquid according to claim 6 or 7.   The polishing liquid according to any one of claims 6 to 9, wherein the acrylic acid polymer has a nitrate group as a terminal group.   The polishing liquid according to any one of claims 6 to 10, wherein the pH is 4.0 to 5.5.   A polishing method wherein at least a part of an insulating material is removed by CMP using the polishing liquid according to claim 6.

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