JP2015209485A - Method for producing polishing liquid, polishing liquid and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a method for producing a polishing liquid having small dependency on wiring and excellent surface flatness and over-polishing resistance after polishing in a CMP technique for polishing a polished film formed on the surface of a substrate; a polishing liquid; and a polishing method.SOLUTION: There is provided a method for producing a polishing liquid which comprises a step of obtaining a polishing liquid by mixing particles containing cerium oxide, a polymer compound A having a carboxylic acid group or a carboxylate group, an organic acid salt B and water. There is provided a polishing liquid which is used for removing at least a part of an insulation material by CMP and contains particles containing cerium oxide, a polymer compound A having a carboxylic acid group or a carboxylate group, an organic acid salt B and water.

Description

  The present invention relates to a polishing liquid production method, a polishing liquid, and a polishing method. More specifically, the present invention relates to a polishing liquid manufacturing method, a polishing liquid, and a polishing method used in a step of planarizing a substrate surface, which is a semiconductor element manufacturing technique.

  In the current ULSI (Ultra Large Scale Integration) manufacturing process, many processing techniques for high density and miniaturization of semiconductor elements are used. A planarization technique by CMP (Chemical Mechanical Polishing) is indispensable as one of the processing techniques.

  In the semiconductor element manufacturing process, CMP is performed a plurality of times. Specifically, the process includes planarization of an interlayer insulating film, STI (shallow trench isolation) formation process, plug formation process, buried metal wiring formation process (damascene process), and the like. The CMP process (planarization process using the CMP technique) is generally performed by supplying a CMP polishing liquid between a polishing pad (polishing cloth) and a material to be polished on a substrate, and removing unnecessary portions of the material to be polished. This is done by removing

  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. Patent Document 4 listed below describes that the planarity of a polished substrate surface is improved by a CMP polishing liquid containing cerium oxide particles, an organic acid having a predetermined condition, a polymer compound, and water. Yes.

Japanese Patent Laid-Open No. 10-106994 Japanese Patent No. 3278532 International Publication No. 2008/032794 International Publication No. 2012/086781

  As described above, in polishing an insulating material such as silicon oxide, in addition to having a predetermined polishing rate for the insulating material, the dependency on the wiring density is small (the difference in polishing is small even between wirings with different densities), and flatness. It is required to have excellent properties.

  In recent years, over-polishing is sometimes performed in STI formation in order to completely remove the silicon oxide film on the convex portion (active portion). At that time, the polishing of the silicon oxide film in the recess (trench) is likely to proceed. Therefore, it is also demanded that polishing of the silicon oxide film in the recess (trench portion) does not proceed easily during over polishing (hereinafter referred to as “over polishing resistance”).

  The present invention has been made to solve the above-described problems. In the CMP technology for polishing a material to be polished formed on the surface of a substrate, the present invention has flatness while having a predetermined polishing rate for the material to be polished. It is an object of the present invention to provide a polishing liquid production method, a polishing liquid, and a polishing method from which an excellent substrate can be obtained. More specifically, the present invention relates to a polishing liquid manufacturing method, a polishing liquid, and a polishing method that have a predetermined polishing rate for a material to be polished, have a low wiring density dependency, and have excellent overpolishing resistance. The purpose is to provide.

  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, a polymer compound A having a carboxylic acid group or a carboxylic acid group, an organic acid salt B, and water. Is provided.

  According to the above polishing liquid, a CMP technique for polishing a material to be polished (for example, an insulating material such as an interlayer insulating film, a BPSG film (silicon oxide film doped with boron or phosphorus), an STI film) formed on the surface of the substrate. However, it is possible to reduce the dependency on the wiring density and improve the over-polishing resistance while having a predetermined polishing rate for the material to be polished.

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

  The pH of the polishing liquid according to the present invention is preferably 4.0 to 6.0. As a result, the dependency on the wiring density can be reduced, and the over-polishing resistance can be further improved.

  The polishing liquid may further contain an organic acid C. By adding the organic acid C, better flatness can be obtained.

  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, a polymer compound A having a carboxylic acid group or a carboxylic acid group, and organic Contains acid salt B and water.

  According to the above polishing liquid, in CMP for polishing a material to be polished (for example, an insulating material) formed on the surface of the substrate, while having a predetermined polishing rate for the material to be polished, the dependency on the wiring density is small, and Over-polishing resistance can be improved.

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

  The pH of the polishing liquid according to the present invention is preferably 4.0 to 6.0. As a result, the dependency on the wiring density can be reduced, and the over-polishing resistance can be further improved.

  The polishing liquid may further contain an organic acid C. By adding the organic acid C, better flatness can be obtained.

  The polishing liquid of the present invention is a two-part polishing liquid composed of a first liquid containing particles containing cerium oxide and water, and a second liquid containing polymer compound A, organic acid salt B and water. You may save as. Thereby, since dispersion stability of cerium oxide particles can be kept better until just before using the polishing liquid, it is possible to obtain a more effective polishing rate and flatness.

  The present invention also relates to a polishing method in which at least a part of a material to be polished including an insulating material is removed by CMP using the polishing liquid. According to such a polishing method, the material to be polished can be polished at a predetermined polishing rate, and a surface having excellent flatness can be obtained.

  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 method for producing a polishing liquid, a 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 includes a step of obtaining abrasive grains containing cerium oxide particles, a step of obtaining a polymer compound A having a carboxylic acid group or a carboxylate group, and the abrasive grains, A step of mixing the polymer compound A, the organic acid salt B, and water to obtain a polishing liquid. Hereinafter, embodiments of the present invention will be described in detail.

(1. Step of obtaining polymer compound A)
In embodiment of this invention, the high molecular compound A which has a carboxylic acid group or a carboxylic acid group is contained. The high molecular compound A can be used individually by 1 type or in combination of 2 or more types. Such a polymer compound A is a polymer obtained by polymerizing a monomer component containing at least one selected from the group consisting of acrylic acid and methacrylic acid (hereinafter referred to as “acrylic acid polymer”). Preferably there is. The monomer component may contain other monomers (excluding acrylic acid and methacrylic acid) copolymerizable with acrylic acid or methacrylic acid.

  As the polymer compound A, 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 the above-mentioned It may be at least one selected from the group consisting of copolymers with other monomers, copolymers of acrylic acid and methacrylic acid with the other monomers. Above all, the acrylic acid polymer is preferably a homopolymer of acrylic acid (polyacrylic acid) from the viewpoint of good adsorption to a material to be polished (for example, a film made of an insulating material). 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.

  The content of the polymer compound A in the polishing liquid is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and still more preferably 0.1% by mass or more with respect to the total mass of the polishing liquid. 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 polymer compound A is 0.001% by mass or more and 2% by mass or less, the dishing amount and wiring density dependency can be reduced and the surface flatness after polishing can be improved. .

  Although the weight average molecular weight of the high molecular compound A does not have a restriction | limiting in particular, 100-150,000 are preferable and 1000-80000 are more preferable. When the polymer compound A has a weight average molecular weight of 100 or more, a good polishing rate tends to be easily obtained when a material to be polished such as a silicon oxide film or a silicon nitride film is polished. When the weight average molecular weight of the polymer compound A is 150,000 or less, the storage stability of the polishing liquid tends to be difficult to decrease.

(Weight average molecular weight of acrylic acid polymer)
The weight average molecular weight can be measured by the following method and reading the value obtained as “Mw”.
(Method)
Equipment used (detector): Hitachi, Ltd., “L-3300” differential refractometer for liquid chromatograph Pump: Hitachi, Ltd., “L-7100” for liquid chromatograph
Degas equipment: None Data processing: GPC integrator “D-2520” manufactured by Hitachi, Ltd.
Column: “Shodex Asahipak GF-710HQ” manufactured by Showa Denko KK, inner diameter 7.6 mm × 300 mm
Eluent: 50 mM Na ₂ HPO ₄ aqueous solution / acetonitrile = 90/10 (v / v)
Measurement temperature: 25 ° C
Flow rate: 0.6 mL / min Measurement time: 30 minutes Sample: Adjust the concentration with a solution having the same composition as the eluent so that the resin concentration is 2% by mass, and filter through a 0.45 μm polytetrafluoroethylene filter. Prepared sample Injection volume: 0.4 μL
Reference material: Polymer Laboratories, narrow molecular weight sodium polyacrylate

(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. A baking method is preferable in that a high polishing rate for an insulating material can be easily obtained, and a chemical oxidation method is preferable in that polishing scratches hardly occur on the surface after polishing.

  When cerium oxide particles are used for polishing an insulating material, high-speed polishing is possible when the crystallite diameter (crystallite diameter) of the cerium oxide particles is large and the crystal distortion is small (ie, the crystallinity is good). However, there is a tendency that polishing scratches are likely to enter the material to be polished.

  From the above viewpoint, preferable cerium oxide particles include particles composed of two or more crystallites and having a crystal grain boundary. Among these, particles having a crystallite diameter of 5 to 300 nm are more preferable. Another preferable cerium oxide particle includes colloidal ceria particles having a crystallite diameter of 5 to 300 nm (for example, colloidal ceria manufactured by Rhodia).

  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 is determined by a laser diffraction particle size distribution analyzer (for example, product name: LA-920, refractive index: 1.93, light source: He-Ne laser, absorption 0 manufactured by Horiba, Ltd.). It means the measured D50 value (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) with respect to the 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 method for producing a polishing liquid of the present invention includes a step of obtaining a polishing liquid by mixing abrasive grains containing cerium oxide particles, an organic acid salt, the polymer compound A, and water, Is provided.

  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 salt B)
The polishing liquid according to this embodiment contains an organic acid salt. As a result, the polishing rate of the material to be polished is improved, and the flatness of the material to be polished (eg, 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. . Further, the over-polishing resistance is remarkably improved. The organic acid salt can be used alone or in combination of two or more.

As the organic acid salt B, -COOM group, a phenolic -OM group, -SO ₃ M group, -O · SO ₃ H group, _-PO 4 _{M 2} group and _-PO 3 _{M 2} group (wherein, M is The cation and Ph are preferably a compound having at least one selected from the group consisting of a phenyl group which may have a substituent.

Examples of M include NH ₄ ; alkali metals such as Na and K; alkaline earth metals such as Ca and Mg; trivalent metals such as Al, Fe and Cr; and rare earths such as Ce. Of these, trivalent metals are preferable, and Al is more preferable.

  It is considered that the organic acid salt B interacts with the polymer compound A to form a strong film on the surface to be polished. More specifically, the carboxyl group (anionic) possessed by the polymer compound A is electrostatically attracted to M (cationic) in the organic acid salt, and the polymer compound A is formed using M as a nucleus. It is considered that the film is in a “rounded state” and is adsorbed on the surface of the film to be polished to form a protective film. This protective film is considered to be stronger and higher in flatness than the protective film formed by the polymer compound A that is not “round”. The organic acid moiety in the organic acid salt B is considered to suppress dissociation of the carboxyl group in the polymer compound A. Thereby, it is considered that the hydrophobicity of the polymer compound A is increased and the polymer compound A is easily adsorbed by the film to be polished.

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, anthraquinone carboxylic acid, anthracene carboxylic 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. Of these, phosphonic acids such as sulfonic acid, 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 salts B can be used alone or in combination of two or more.

  The content of the organic acid salt B is preferably 0.001% by mass or more with respect to the total mass of the polishing liquid, from the viewpoint of easily improving the flatness of the material to be polished (for example, a silicon oxide film) after polishing. 0.005 mass% or more is more preferable, and 0.01 mass% or more is still more preferable. The content of the organic acid salt B is preferably 1% by mass or less, more preferably 0.5% by mass or less, based on the total mass of the polishing liquid from the viewpoint of easily improving the polishing rate of the material to be polished. Preferably, 0.1% by mass or less is more preferable, 0.06% by mass or less is particularly preferable, and 0.05% by mass or less is very preferable.

(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.

(Other ingredients)
The polishing liquid may contain a compound other than the above components as an additive. Specific examples include an organic acid C, a water-soluble polymer compound, a water-soluble cationic compound, a water-soluble anionic compound, a water-soluble nonionic compound, and a water-soluble amphoteric compound. These additives can be used alone or in combination of two or more. The content of the other additives is preferably 0.001 to 5% by mass based on the total mass of the polishing liquid.

(Organic acid)
The polishing liquid can obtain better flatness by adding an organic acid C in addition to the organic acid salt B. The organic acid C is considered to suppress dissociation of the carboxyl group in the polymer compound A. Thereby, it is considered that the hydrophobicity of the polymer compound A is increased and the polymer compound A is easily adsorbed by the film to be polished.

The organic acid C is at least selected from the group consisting of —COOM group, phenolic —OM group, —SO ₃ M group, —O · SO ₃ H group, —PO ₄ M ₂ group and —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, anthraquinone carboxylic acid, anthracene carboxylic 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 C 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. Moreover, the effect of suppressing the dissociation of the carboxyl group in the polymer compound A is further enhanced, which is effective in improving flatness.

(PH adjuster)
The polishing liquid according to this embodiment can be adjusted to a desired pH by adding a pH adjuster as necessary. Although there is no restriction | limiting in particular as a pH adjuster, For example, inorganic acid components, such as nitric acid, a sulfuric acid, hydrochloric acid, phosphoric acid, boric acid, an acetic acid; Basic components, such as sodium hydroxide, ammonia, potassium hydroxide, calcium hydroxide Is mentioned. When the polishing liquid is used for semiconductor polishing, ammonia and an acid component are preferably used.

(PH)
The pH (25 ° C.) of the polishing liquid is preferably 4.0 to 6.0, and more preferably 4.5 to 5.5. When the pH is 4.0 or more and 6.0 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: 4.01 (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.

  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, and an additive solution containing other components (for example, polymer compound A and organic acid salt B described later) and water. You may obtain a polishing liquid by preserve | saving and mixing both. Each composition described in the “other additives” is preferably included in the additive solution.

<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 this embodiment contains particles containing the cerium oxide, the polymer compound A having the carboxylic acid group or the carboxylic acid group, the organic acid salt B, and water. The other components are as described above.

<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) 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, or a semiconductor substrate at a stage where a circuit element is formed A substrate on which is formed.

  Examples of the insulating material include inorganic insulating materials and organic insulating materials. Examples of inorganic insulating materials include silicon-based insulating materials. Examples of the silicon-based insulating material include silicon-based materials such as silicon oxide, fluorosilicate glass, organosilicate glass, silsesquioxane hydride, silicon carbide, and silicon nitride. The insulating material may be doped with an element such as phosphorus or boron. Examples of the organic insulating material include wholly aromatic low dielectric constant insulating materials. For example, an inorganic insulating material such as a silicon oxide film or a silicon nitride film can be given. The silicon oxide film may be doped with an element such as phosphorus or boron.

  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. The polishing method of the present invention can be used, for example, in a flattening step of an interlayer insulating film, a BPSG film (silicon oxide film doped with boron or phosphorus), a shallow trench isolation (STI) forming step, or the like.

  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, it is preferable that the dishing amount 6 shown in FIG. 1C 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.

  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 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 polymer compound A)
(Production of polyacrylic acid)
250 g of deionized water was charged into a 1 liter synthesis flask equipped with a stirrer, thermometer and nitrogen inlet. The temperature was raised to 90 ° C. with stirring in a nitrogen gas atmosphere. A solution prepared by dissolving 130 g of acrylic acid and 14 g of 2,2′-azobis [2- (2-imidazolin-2-yl) propane] sulfate in 130 g of methanol was poured into the flask over 2 hours. After keeping at 90 ° C. for 3 hours, the solution was cooled to 40 ° C. or lower. Deionized water was added to obtain a 40% by mass aqueous solution of polyacrylic acid B (a homopolymer of acrylic acid). 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 2500 (polyacrylic acid). Sodium acid equivalent value).

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 cerium oxide dispersion was placed in a 1 liter container (height: 170 mm) and allowed to stand, and sedimentation classification was performed. 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.

  0.15 g of aluminum lactate as the organic acid salt B, 1.5 g of p-toluenesulfonic acid as the organic acid C, and 800 g of deionized water are mixed, and the polymer compound A has a weight average molecular weight of 2500 at 40% by mass. 3.75 g of a certain polyacrylic acid 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 850 g as an additive solution.

  66 g of the above cerium oxide slurry is added, and ammonia water (25% by mass) is added to adjust the pH to 5.4. Further, deionized water is added to make the total amount 1000 g, and the polishing liquid (cerium oxide) Solid content: 0.5% 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.

(Examples 2 to 6 and Comparative Example 1)
A ceria-based polishing liquid was prepared in the same manner as in Example 1 except that the type and blending amount of the organic acid salt B were changed as shown in Table 1. Also in these polishing liquids, the average particle diameter 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. In Comparative Example 1, no organic acid salt B was added.

(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 a polishing surface plate with the insulating film (silicon oxide film) surface as the material to be polished facing down, and the processing load was set to 3 psi (about 20.7 kPa).

While dropping the ceria-based polishing liquid prepared above on the polishing surface plate at a rate of 150 ml / min, the polishing surface plate and the polishing test wafer were each operated at 90 min ⁻¹ to polish the polishing test wafer. .

  In this study, the polishing test wafer is first polished (roughened) using silica slurry (Cabot: SS-25) under the above conditions so that the thickness of the silicon oxide film 3 is about 200 nm. It was. Thereafter, the roughened polishing test wafer was polished with the above-prepared polishing liquid. 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 thicknesses of the trench portions of 20 μm / 80 μm and 80 μm / 20 μm are measured by the above-described film thickness measuring apparatus, and the absolute value of the difference between the remaining film thicknesses at the two locations is an index of wiring density dependency And the wiring density dependency was evaluated. In addition, it is better that the wiring density dependency is small.

  The polished test wafer after polishing was subjected to additional polishing (overpolishing) for 30% of the polishing time, and the polishing rate of the 100 μm / 100 μm trench during this overpolishing was evaluated as overpolishing resistance. In addition, it is better that the over-polishing resistance is small.

  From Table 1, the polishing liquid of the present invention can reduce the dependency on the wiring density and improve the over-polishing resistance while ensuring a predetermined value as the polishing rate of the silicon oxide film by adding an organic acid salt. It became clear.

  DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Silicon nitride film, 3 ... Silicon oxide film, 4 ... Depth of trench part, 5 ... Thickness of silicon oxide film in trench part after grinding | polishing, 6 ... Dishing amount, 100,200 ... Substrate.

Claims (10)

  A method for producing a polishing liquid comprising a step of mixing a particle containing cerium oxide, a polymer compound A having a carboxylic acid group or a carboxylic acid group, an organic acid salt B, and water to obtain a polishing liquid.   The manufacturing method of the polishing liquid of Claim 1 whose compounding quantity of the high molecular compound A is 0.001-2 mass% with respect to the total mass of polishing liquid.   The method for producing a polishing liquid according to claim 1 or 2, wherein the polishing liquid has a pH of 4.0 to 6.0.   The method for producing a polishing liquid according to claim 1, wherein the polishing liquid further contains an organic acid C. A polishing liquid for removing at least a part of an insulating material by chemical mechanical polishing (CMP),
A polishing liquid containing particles containing cerium oxide, a polymer compound A having a carboxylic acid group or a carboxylic acid group, an organic acid salt B, and water.   The polishing liquid according to claim 5, wherein the content of the polymer compound A is 0.001 to 2 mass% with respect to the total mass of the polishing liquid.   The polishing liquid according to claim 5 or 6, wherein the pH is 4.0 to 6.0.   The polishing liquid according to claim 5, wherein the polishing liquid further contains an organic acid C.   6. A two-part polishing liquid comprising a first liquid containing particles containing cerium oxide and water, and a second liquid containing polymer compound A, organic acid salt B and water. The polishing liquid in any one of -8.   A polishing method in which at least a part of an insulating material is removed by CMP using the polishing liquid according to claim 5.

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