JP2012209568A - Cmp polishing liquid, polishing method of substrate, and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CMP polishing liquid capable of improving the polishing speed of a silicon oxide film and a silicon nitride film to the polishing speed of a polysilicon film and capable of being applied to a polishing process for polishing a silicon oxide film and a silicon nitride film with a polysilicon film as a stopper film.SOLUTION: The CMP polishing liquid of the present invention is a CMP polishing liquid to be used by mixing a first liquid and a second liquid, where the first liquid contains cerium-based abrasive grains, a dispersant and water, the second liquid contains a polyacrylic acid compound, a surfactant, a phosphate compound and water, the pH of the second liquid is 6.5 or more, and the first liquid and the second liquid are mixed so that the content of the phosphate compound is in a prescribed range. In addition, the CMP polishing liquid of the present invention contains cerium-based abrasive grains, a dispersant, a polyacrylic acid compound, a surfactant, a phosphate compound and water, and the content of the phosphate compound is in a prescribed range.

Description

  The present invention relates to a CMP polishing liquid, a substrate polishing method, and an electronic component.

  In the present ultra-large scale integrated circuit, there is a tendency to further increase the mounting density, and various fine processing techniques have been researched and developed, and the design rule is on the order of sub-half micron. One of the technologies that have been developed in order to satisfy such demands for miniaturization is a CMP (chemical mechanical polishing) technology.

  This CMP technique can reduce the burden of the exposure technique by almost completely planarizing the layer to be exposed in the manufacturing process of the semiconductor device, and can stabilize the yield at a high level. Therefore, the CMP technique is an essential technique when performing, for example, planarization of an interlayer insulating film, a BPSG film, shallow trench isolation, and the like.

  Currently, the CMP polishing liquid that is generally used is a CMP polishing liquid whose main object is polishing a silicon oxide film, and a silicon oxide film or a polysilicon film is polished five times or more faster than a silicon nitride film. There is usually a characteristic.

  On the other hand, there was no polishing liquid capable of polishing the silicon nitride film at a practical speed. Therefore, as disclosed in Patent Document 1, there is a technique that increases the polishing rate of the silicon nitride film by adding phosphoric acid in an amount of 1.0% by mass or more, thereby enabling practical use of the polishing process of the silicon nitride film.

Japanese Patent No. 3190742

  In recent years, various circuit forming processes using CMP technology have been proposed. One of them is polishing a silicon oxide film and a silicon nitride film, and polishing when a polysilicon film as a stopper film is exposed. There is a process to terminate. More specifically, for example, a High-k / metal Gate process expected to be applied to a logic device after the 45 nm node (polishing a silicon oxide film and a silicon nitride film, and polishing when the polysilicon film is exposed). Process).

  The technique disclosed in Patent Document 1 enables practical use of such a polishing process in which a silicon oxide film and a silicon nitride film are polished at a practical polishing rate and a polysilicon film is used as a stopper film. It is not a thing. The technique disclosed in Patent Document 1 cannot be applied to a polishing process in which two types of films, a silicon oxide film and a silicon nitride film, are selectively polished with respect to a polysilicon film.

  The present invention can improve the polishing rate of the silicon oxide film and the silicon nitride film relative to the polishing rate of the polysilicon film, and polish the silicon oxide film and the silicon nitride film by using the polysilicon film as a stopper film. The present invention provides a CMP polishing liquid that can be applied to a process, a method for polishing a substrate using the CMP polishing liquid, and an electronic component that includes the substrate polished by the polishing method.

  That is, the present invention is a CMP polishing liquid used by mixing a first liquid and a second liquid, and the first liquid contains cerium-based abrasive grains, a dispersant, and water. The second liquid contains a polyacrylic acid compound, a surfactant, a pH adjuster, at least one phosphoric acid compound of phosphoric acid or a phosphoric acid derivative, and water, and the pH of the second liquid is 6.5 or more, and the first liquid and the second liquid are mixed so that the content of the phosphoric acid compound is 0.01 to 1.0% by mass based on the total mass of the CMP polishing liquid. A CMP polishing liquid is provided.

  Such a CMP polishing liquid of the present invention can improve the polishing rate of the silicon oxide film and the silicon nitride film with respect to the polishing rate of the polysilicon film, and the silicon oxide film using the polysilicon film as a stopper film, The present invention can be applied to a polishing process for polishing a silicon nitride film.

  The second liquid can contain a basic compound having a pKa of 8 or more as a pH adjuster.

  The second liquid preferably contains a nonionic surfactant as a surfactant. In this case, the polishing rate of the silicon oxide film and the silicon nitride film can be further improved with respect to the polishing rate of the polysilicon film.

  The pH of the first liquid is preferably 7.0 or higher.

  The first liquid preferably contains cerium oxide particles as cerium-based abrasive grains. More preferably, the first liquid contains cerium oxide particles as cerium-based abrasive grains, and the average particle diameter of the cerium-based abrasive grains is 0.01 to 2.0 μm.

  The first liquid preferably contains a polyacrylic acid-based dispersant as a dispersant. In this case, the polishing rate of the silicon oxide film and the silicon nitride film can be further improved with respect to the polishing rate of the polysilicon film.

  The present invention also includes a cerium-based abrasive, a dispersant, a polyacrylic acid compound, a surfactant, a pH adjuster, at least one phosphoric acid compound of phosphoric acid or a phosphoric acid derivative, and water. And a CMP polishing liquid in which the content of the phosphoric acid compound is 0.01 to 1.0% by mass based on the total mass of the CMP polishing liquid.

  Such a CMP polishing liquid of the present invention can improve the polishing rate of the silicon oxide film and the silicon nitride film with respect to the polishing rate of the polysilicon film, and the silicon oxide film using the polysilicon film as a stopper film, The present invention can be applied to a polishing process for polishing a silicon nitride film.

  The CMP polishing liquid of the present invention can contain a basic compound having a pKa of 8 or more as a pH adjuster.

  The CMP polishing liquid of the present invention preferably contains a nonionic surfactant as a surfactant. In this case, the polishing rate of the silicon oxide film and the silicon nitride film can be further improved with respect to the polishing rate of the polysilicon film.

  The CMP polishing liquid of the present invention preferably contains cerium oxide particles as cerium-based abrasive grains. Moreover, it is preferable that the CMP polishing liquid of this invention contains a cerium oxide particle as a cerium-type abrasive grain, and the average particle diameter of a cerium-type abrasive grain is 0.01-2.0 micrometers.

  The CMP polishing liquid of the present invention preferably contains a polyacrylic acid dispersant as a dispersant. In this case, the polishing rate of the silicon oxide film and the silicon nitride film can be further improved with respect to the polishing rate of the polysilicon film.

  In the present invention, the CMP polishing liquid is applied between the film to be polished and the polishing cloth in a state where the film to be polished on the substrate having the film to be polished on at least one surface is pressed against the polishing cloth of the polishing surface plate. Provided is a substrate polishing method comprising a polishing step of polishing a film to be polished by relatively moving a substrate and a polishing surface plate while supplying.

  Further, the present invention provides a first liquid containing cerium-based abrasive grains, a dispersant and water, and at least one phosphoric acid compound of a polyacrylic acid compound, a surfactant, a pH adjuster, phosphoric acid or a phosphoric acid derivative. And a second liquid containing water and having a pH of 6.5 or more, and the content of the phosphoric acid compound is 0.01 to 1.0% by mass based on the total mass of the CMP polishing liquid. Polishing of the substrate, comprising: a polishing liquid preparation step for obtaining a CMP polishing liquid; and a polishing step for polishing the polishing target film of the substrate having the polishing target film formed on at least one surface using the CMP polishing liquid. Provide a method.

  The substrate polishing method of the present invention can improve the polishing rate of the silicon oxide film and the silicon nitride film with respect to the polishing rate of the polysilicon film. The silicon oxide film and the silicon nitride are formed using the polysilicon film as a stopper film. The present invention can be applied to a polishing process for polishing a film.

  In the substrate polishing method of the present invention, the pH of the first liquid is preferably 7.0 or more. In the substrate polishing method of the present invention, the one surface of the substrate may have a step. In the substrate polishing method of the present invention, a polysilicon film is formed between the substrate and the film to be polished, and in the polishing step, the film to be polished may be polished using the polysilicon film as a stopper film. Further, in the substrate polishing method of the present invention, at least one of a silicon oxide film and a silicon nitride film may be formed on the substrate as a film to be polished.

  The present invention provides an electronic component including a substrate polished by the substrate polishing method. Such an electronic component according to the present invention has an excellent substrate corresponding to fine processing by providing a substrate capable of improving the polishing rate of the silicon oxide film and the silicon nitride film with respect to the polishing rate of the polysilicon film. Have good quality.

  The CMP polishing liquid and the substrate polishing method using the CMP polishing liquid of the present invention can polish the silicon oxide film and the silicon nitride film at a sufficiently practical speed while suppressing the polishing speed of the polysilicon film. It can be applied to a polishing process in which a silicon oxide film and a silicon nitride film are polished using a polysilicon film as a stopper film. Further, an electronic component including a substrate polished by the polishing method of the present invention has excellent quality corresponding to processing miniaturization.

It is a schematic cross section which shows the grinding | polishing method which concerns on one Embodiment of this invention. It is a schematic cross section which shows the pattern wafer used in the Example.

(CMP polishing liquid)
The CMP polishing liquid of this embodiment contains cerium-based abrasive grains, a dispersant, a polyacrylic acid compound, a surfactant, a pH adjuster, phosphoric acid or at least one phosphoric acid derivative, and water. . The CMP polishing liquid of this embodiment can be obtained by mixing a slurry (first liquid) and an additive liquid (second liquid).

{slurry}
First, the slurry will be described. The slurry contains cerium-based abrasive grains, a dispersant, and water. In the slurry, cerium-based abrasive particles are preferably dispersed in water with a dispersant.

<Cerium-based abrasive>
Cerium-based abrasive grains are defined as abrasive grains containing cerium as a constituent element. The CMP polishing liquid of this embodiment is cerium oxide, cerium hydroxide, ammonium cerium nitrate, cerium acetate, cerium sulfate hydrate, cerium bromate, cerium bromide, cerium chloride, cerium oxalate, cerium nitrate. And at least one abrasive selected from cerium carbonate, more preferably cerium oxide particles, and still more preferably cerium oxide particles. The method for producing the cerium oxide particles is not particularly limited, and for example, an oxidation method using baking or hydrogen peroxide can be used. The cerium oxide particles can be obtained, for example, by oxidizing a cerium compound such as carbonate, nitrate, sulfate, or oxalate. The firing temperature is preferably 350 to 900 ° C.

  The cerium-based abrasive preferably includes a polycrystalline cerium-based abrasive having a grain boundary. Since such polycrystalline cerium-based abrasive grains become fine during polishing and active surfaces appear one after another, a high polishing rate for a silicon oxide film can be maintained at a high level.

  The crystallite diameter of the cerium-based abrasive is preferably 1 to 400 nm. The crystallite diameter can be measured by a TEM photograph image or an SEM image. In a cerium oxide slurry (hereinafter also simply referred to as “slurry”) used for polishing a silicon oxide film formed by a TEOS-CVD method or the like, the smaller the crystallite diameter of the cerium oxide particles and the smaller the crystal distortion, The better the crystallinity, the faster the polishing is possible. The crystallite size is the size of a single crystal of a cerium-based abrasive grain, and in the case of a polycrystal having a crystal grain boundary, it means the size of a single particle constituting the polycrystal. .

  When the cerium-based abrasive is agglomerated, it is preferably mechanically pulverized. As the pulverization method, for example, dry pulverization using a jet mill or the like, or wet pulverization using a planetary bead mill or the like is preferable. As the jet mill, for example, those described in “Chemical Engineering Papers”, Vol. 6, No. 5, (1980), pages 527 to 532 can be used.

  Such a cerium-based abrasive is dispersed in water as a dispersion medium to obtain a slurry. As a dispersion method, for example, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to a dispersion treatment using a normal stirrer, using a dispersant described later.

  As a method for further micronizing the cerium-based abrasive particles dispersed by the above method, for example, a sedimentation classification method is used by forcibly sedimenting the slurry after centrifugation with a small centrifuge and taking out only the supernatant liquid. Can do. In addition, a high-pressure homogenizer that collides cerium-based abrasive grains in the dispersion medium with each other at high pressure may be used as a method for forming fine particles.

  The average particle size of the cerium-based abrasive grains in the slurry is preferably 0.01 to 2.0 μm, more preferably 0.08 to 0.5 μm, and still more preferably 0.08 to 0.4 μm. Moreover, it is preferable that the CMP polishing liquid of this embodiment contains a cerium oxide particle, and the average particle diameter of a cerium-type abrasive grain is 0.01-2.0 micrometers. When the average particle size is 0.01 μm or more, the polishing rate of the silicon oxide film and the silicon nitride film can be further improved. When the average particle size is 2.0 μm or less, it is possible to suppress the polishing film from being scratched.

  The average particle diameter of cerium-based abrasive grains refers to the median diameter of volume distribution measured with a laser diffraction particle size distribution meter. Specifically, such an average particle diameter can be obtained using LA-920 (trade name) manufactured by Horiba, Ltd. First, a sample containing cerium-based abrasive grains (which may be a slurry or a CMP polishing liquid) is diluted or concentrated so that the transmittance (H) during measurement with respect to a He—Ne laser is 60 to 70%. Get. And this measurement sample is thrown into LA-920 and measured, and it is set as the arithmetic mean diameter (mean size) obtained.

  The content of the cerium-based abrasive is preferably 0.2 to 3.0% by mass, more preferably 0.3 to 2.0% by mass, and 0.5 to 1.5% by mass based on the total mass of the CMP polishing liquid. % Is more preferable. When the content of the cerium-based abrasive is 3.0% by mass or less, the effect of adjusting the polishing rate by the additive liquid is further improved. Further, when the content of the cerium-based abrasive is 0.2% by mass or more, the polishing rate of the silicon oxide film is further improved, and a desired polishing rate can be easily obtained.

<Dispersant>
The dispersant used in the CMP polishing liquid of this embodiment is not limited as long as it is a compound that can be dissolved in water and can disperse the cerium-based abrasive grains. In general, the dispersant is preferably a compound having a water solubility of 0.1 to 99.9% by mass, such as a water-soluble anionic dispersant, a water-soluble nonionic dispersant, and a water-soluble compound. Examples thereof include a cationic dispersant and a water-soluble amphoteric dispersant, and a polycarboxylic acid type polymer dispersant described later is preferable.

  Examples of the water-soluble anionic dispersant described above include lauryl sulfate triethanolamine, ammonium lauryl sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and polycarboxylic acid type polymer dispersants.

  Examples of the polycarboxylic acid type polymer dispersant described above include polymers of carboxylic acid monomers having an unsaturated double bond such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid, and unsaturated dicarboxylic acids. Examples thereof include a copolymer of a carboxylic acid monomer having a heavy bond and another monomer having an unsaturated double bond, and an ammonium salt or an amine salt thereof. The polycarboxylic acid type polymer dispersant is preferably a polyacrylic acid type dispersant, and more preferably a polymer dispersant having an ammonium acrylate salt as a constituent unit as a copolymerization component.

  As the polymer dispersing agent having an acrylic acid ammonium salt as a structural unit as the copolymer component described above, for example, a polyacrylic acid ammonium salt, an ammonium salt of a copolymer of alkyl acrylate and acrylic acid, or the like is preferably used. it can. Further, it may be used as two or more kinds of dispersants including at least one kind of polymer dispersant having an acrylic acid ammonium salt as a structural unit as a copolymer component and at least one kind selected from other dispersants. it can.

The weight average molecular weight of the polycarboxylic acid type polymer dispersant is preferably 100,000 or less. In addition, a weight average molecular weight can be measured using GPC on the following conditions, for example.
(conditions)
Sample: 10 μL
Standard polystyrene: Standard polystyrene manufactured by Tosoh Corporation (molecular weight: 190000, 17900, 9100, 2980, 578, 474, 370, 266)
Detector: manufactured by Hitachi, Ltd., RI-monitor, trade name “L-3000”
Integrator: Hitachi, Ltd., GPC integrator, product name “D-2200”
Pump: manufactured by Hitachi, Ltd., trade name “L-6000”
Degassing device: Showa Denko Co., Ltd., trade name "Shodex DEGAS"
Column: Hitachi Chemical Co., Ltd., trade names “GL-R440”, “GL-R430”, “GL-R420” connected in this order and used as eluent: tetrahydrofuran (THF)
Measurement temperature: 23 ° C
Flow rate: 1.75 mL / min Measurement time: 45 minutes

  Examples of the water-soluble nonionic dispersant described above include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octylphenyl. Ether, polyoxyethylene nonylphenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate Rate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, tetraolei Acid polyoxyethylene sorbit, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, 2-hydroxyethyl methacrylate, alkyl And alkanolamides.

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

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

  The various dispersants described above can be used alone or in combination of two or more. In addition, the CMP polishing liquid obtained by mixing the slurry and the additive liquid can use the same material as the polyacrylic acid compound and surfactant described later as the dispersant. In this case, the CMP polishing liquid obtained by mixing the slurry and the additive liquid contains a substance derived from the slurry and a substance derived from the additive liquid.

  The content of the dispersant in the slurry is 1.0 to 5.0% by mass on the basis of the total mass of the abrasive grains in the slurry in that the abrasive grains can be sufficiently dispersed and the aggregation and settling during storage can be suppressed. Is preferable, and 1.0-4.0 mass% is more preferable.

  When using a CMP polishing liquid for polishing related to the manufacture of semiconductor elements, for example, the content of impurity ions (alkali metals such as sodium ions and potassium ions, halogen atoms and sulfur atoms) in the total dispersant, It is preferable to keep the mass ratio to 10 ppm or less based on the entire CMP polishing liquid.

<PH of slurry>
The pH of the slurry is preferably 7.0 or more, more preferably 7.0 to 12.0, and even more preferably 7.0 to 11.0. When the pH is 7.0 or more, aggregation of particles can be suppressed. When the pH is 12.0 or less, good flatness can be obtained.

<Water>
In the CMP polishing liquid of the present embodiment, the water used as a medium for diluting the slurry, additive liquid or concentrated liquid is not particularly limited, but deionized water and ultrapure water are preferable. The content of water is not particularly limited, and may be the remainder of the content of other components.

{Additive liquid}
Next, the additive solution will be described. The additive liquid contains a polyacrylic acid compound, a surfactant, a pH adjusting agent, at least one phosphoric acid compound of phosphoric acid or a phosphoric acid derivative, and water.

<Polyacrylic acid compound>
The additive solution contains a polyacrylic acid compound as one component of the additive solution component. Examples of the polyacrylic acid compound include polyacrylic acid formed from a polymer of acrylic acid alone and a copolymer of acrylic acid and a water-soluble alkyl acrylate. Examples of the polyacrylic acid compound include polyacrylic acid, a copolymer of acrylic acid and methyl acrylate, a copolymer of acrylic acid and methacrylic acid, and a copolymer of acrylic acid and ethyl acrylate. Among them, it is preferable to use polyacrylic acid. These can be used alone or in combination of two or more.

  The weight average molecular weight of the polyacrylic acid compound is preferably 500000 or less, and more preferably 50000 or less. When the weight average molecular weight is 500,000 or less, for example, when polyacrylic acid is used, the polyacrylic acid is easily adsorbed uniformly on the film to be polished. The weight average molecular weight can be measured using GPC under the same conditions as for the polycarboxylic acid type polymer dispersant.

  The content of the polyacrylic acid compound is preferably 0.05 to 2.0% by mass, more preferably 0.08 to 1.8% by mass, based on the total mass of the CMP polishing liquid, and 0.10 to 1.5 More preferred is mass%. When the content of the polyacrylic acid compound is 2.0% by mass or less, the polishing rate of the silicon oxide film can be further improved. Flatness can be improved as content of a polyacrylic acid compound is 0.05 mass% or more. In addition, when using a polyacrylic acid compound as the said dispersing agent, it is preferable that the total amount of the polyacrylic acid compound as a dispersing agent and the polyacrylic acid compound in an additive liquid satisfy | fills the said range.

<Surfactant>
The additive liquid contains a surfactant as one component of the additive liquid component. Examples of the surfactant include an anionic surfactant, a nonionic surfactant, a cationic surfactant, and a zwitterionic surfactant. These can be used alone or in combination of two or more. Among the above surfactants, nonionic surfactants are particularly preferable.

  Examples of the nonionic surfactant described above include polyoxypropylene, polyoxyethylene alkyl ether, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene polyoxypropylene ether derivatives, and polyoxypropylene glyceryl ether. , Ether type surfactants such as polyethylene glycol, methoxy polyethylene glycol, oxyethylene adducts of acetylenic diol, ester type surfactants such as sorbitan fatty acid ester and glycerol borate fatty acid ester, amino ethers such as polyoxyethylene alkylamine Type surfactant, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerol borate fatty acid ester, polyoxyethylene Ether ester type surfactants such as alkyl esters, fatty acid alkanolamides, alkanolamide type surfactants such as polyoxyethylene fatty acid alkanolamides, oxyethylene adducts of acetylenic diols, polyvinylpyrrolidone, polyacrylamide, polydimethylacrylamide, etc. Can be mentioned.

  The content of the surfactant is preferably 0.01 to 1.0% by mass, more preferably 0.02 to 0.7% by mass, and 0.03 to 0.5% by mass based on the total mass of the CMP polishing liquid. % Is more preferable. When the surfactant content is 1.0% by mass or less, the polishing rate of the silicon oxide film is further improved. When the surfactant content is 0.01% by mass or more, an increase in the polishing rate of the polysilicon film can be further suppressed. In addition, when using surfactant as the said dispersing agent, it is preferable that the total amount of surfactant as a dispersing agent and surfactant in an addition liquid satisfy | fills the said range.

<PH of additive solution>
The pH of the additive solution needs to be 6.5 or more, preferably 6.7 to 12.0, and more preferably 6.8 to 11.0. When the pH is 6.5 or more, it is possible to suppress aggregation of particles contained in the slurry when the additive solution and the slurry are mixed. When the pH is 12.0 or less, good flatness can be obtained when the additive solution and the slurry are mixed.

  The pH of the additive solution can be measured with a pH meter using a general glass electrode. Specifically, for example, trade name: Model (F-51) manufactured by HORIBA, Ltd. can be used for pH measurement. The pH of the additive solution is as follows: phthalate pH standard solution (pH: 4.01), neutral phosphate pH standard solution (pH: 6.86), and borate pH standard solution (pH: 9.18). ) Is used as a pH standard solution, the pH meter is calibrated at three points, the electrode of the pH meter is placed in the additive solution, and the value after 2 minutes has elapsed and stabilized is measured. At this time, the liquid temperature of the standard buffer solution and the additive solution can be both 25 ° C., for example. The pH of the slurry can be measured by the same method.

<PH adjuster>
The CMP polishing liquid of this embodiment contains a pH adjuster as one component of the additive liquid component. Examples of the pH adjuster include water-soluble basic compounds and water-soluble acid compounds. Examples of the basic compound include basic compounds having a pKa of 8 or more. Here, “pKa” means the acid dissociation constant of the first dissociable acidic group, and is the negative common logarithm of the equilibrium constant Ka of the group. Specifically, as the basic compound described above, water-soluble organic amines, aqueous ammonia and the like are preferably used. Moreover, pH of an additive liquid can also be adjusted with other containing components, such as the said polyacrylic acid compound.

  Examples of water-soluble organic amines include ethylamine, diethylamine, triethylamine, diphenylguanidine, piperidine, butylamine, dibutylamine, isopropylamine, tetramethylammonium oxide, tetramethylammonium chloride, tetramethylammonium bromide, and tetramethylammonium fluoride. , Tetrabutylammonium hydroxide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium fluoride, tetramethylammonium nitrate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium maleate, tetramethyl Examples thereof include ammonium sulfate.

  For example, when a basic compound is used, the content of the pH adjuster is preferably 0.01 to 10.0% by mass, more preferably 0.05 to 5.0% by mass, based on the total mass of the CMP polishing liquid. More preferably, it is 1 to 3.0% by mass. However, since the content of the pH adjuster is restricted by the pH to be adjusted, it is determined by the content of other components (strong acid, polyacrylic acid compound, etc.) and there is no particular limitation.

<Phosphate compound>
The additive liquid contains at least one phosphoric acid compound of phosphoric acid or a phosphoric acid derivative as one component of the additive liquid component. The “phosphoric acid compound” includes phosphoric acid and phosphoric acid derivatives. Examples of the phosphoric acid derivative include a polymer of phosphoric acid such as dimer and trimer (for example, pyrophosphoric acid, pyrophosphorous acid, and trimetaphosphoric acid), and a compound containing a phosphoric acid group (for example, sodium hydrogen phosphate, Sodium phosphate, ammonium phosphate, potassium phosphate, calcium phosphate, sodium pyrophosphate, polyphosphoric acid, sodium polyphosphate, metaphosphoric acid, sodium metaphosphate, ammonium phosphate, etc.).

  The content of the phosphoric acid compound is 0.01 to 1.0% by mass based on the total mass of the CMP polishing liquid, preferably 0.02 to 0.7% by mass, and 0.03 to 0.5% by mass. More preferred. When the content of the phosphoric acid compound is 1.0% by mass or less, the polishing rate of the silicon nitride film can be further improved. Similarly, when the content of the phosphoric acid compound is 0.01% by mass or more, the polishing rate of the silicon nitride film can be further improved. In addition, when using simultaneously phosphoric acid and a phosphoric acid derivative as a phosphoric acid compound, it is preferable that those total amount satisfy | fills the said range.

(CMP polishing liquid storage method)
The CMP polishing liquid of this embodiment is preferably stored as, for example, a two-part polishing liquid divided into a slurry in which cerium-based abrasive grains are dispersed in water with a dispersant and an additive liquid. When the slurry and additive are not mixed and stored as a two-component polishing liquid, the cerium-based abrasive grains can be prevented from agglomerating, and the effect of suppressing polishing flaws and the fluctuation of the polishing rate can be suppressed.

  The slurry and the additive solution may be mixed in advance or may be mixed immediately before use. In the case of using a two-component polishing liquid, for example, A method in which the slurry and the additive liquid are fed through separate pipes, these pipes are merged, mixed immediately before the supply pipe outlet, and supplied onto the polishing platen. Or B method of mixing the slurry and additive liquid immediately before polishing, C method of supplying the slurry and additive separately on the polishing surface plate and mixing both liquids on the polishing surface plate, and adding the slurry and the material in advance The D method etc. which supply what mixed the liquid with supply piping can be used. By arbitrarily changing the blend of these two liquids, it is possible to adjust the planarization characteristics and the polishing rate. The mixing ratio of the slurry and the additive liquid is preferably about 1:10 to 10: 1 (slurry: additive liquid) in mass ratio. In the case of Method A or Method B, the slurry or additive solution may be preliminarily concentrated in a reduced amount of water, and may be diluted with deionized water during mixing as necessary.

(Substrate polishing method)
The substrate polishing method of this embodiment is a method for polishing the above-described CMP polishing liquid in a state where the polishing target film of a substrate having a polishing target film formed on at least one surface is pressed against a polishing cloth of a polishing surface plate. A polishing step of polishing the film to be polished by relatively moving the substrate and the polishing surface plate while supplying the film between the film and the polishing cloth is provided. Further, the substrate polishing method of the present embodiment includes a polishing liquid preparation step of mixing the slurry and the additive liquid to obtain the CMP polishing liquid described above, and at least one surface using the obtained CMP polishing liquid. A polishing step of polishing the film to be polished of the substrate on which the polishing film is formed.

  The substrate polishing method of the present embodiment is particularly suitable for a polishing step of polishing the one surface of the substrate to flatten the step when the one surface on which the film to be polished of the substrate is formed has a step. is there.

  In the substrate polishing method of the present embodiment, when a polysilicon film is formed between the substrate and the film to be polished, the film to be polished can be polished using the polysilicon film as a stopper film in the polishing step. . For example, after forming a stopper film along the separation groove on the substrate on which the separation groove is formed, forming the film to be polished on the stopper film, the film to be polished can be removed until the stopper film is exposed. .

  More specifically, a polishing method for polishing the substrate 100 having a structure as shown in FIG. A substrate 100 shown in FIG. 1A has shallow trench isolation (STI) formed by embedding an insulator 2 such as silicon dioxide in a groove formed in silicon 1. An insulating film (High-k insulating film) 3 having high conductivity is stacked on the silicon 1. A dummy gate 4 made of a polysilicon film is formed at a predetermined position on the insulating film 3, and a side wall 5 made of a silicon nitride film is formed on the side of the dummy gate 4. Further, in order to apply stress to the diffusion layer to improve the transistor performance, a stress liner 6 of a silicon nitride film is laminated so as to cover the surface, and finally a silicon oxide film 7 is laminated. The silicon oxide film 7 and a part of the silicon nitride stress liner 6 on such a substrate are polished by using the CMP polishing liquid according to the present embodiment until the polysilicon dummy gate 4 is exposed. Thus, a substrate 200 having a structure as shown in FIG. 1B can be obtained. In this step, the polysilicon film as the dummy gate 4 functions as a stopper film for suppressing excessive polishing.

  Hereinafter, the polishing method will be further described by taking as an example a semiconductor substrate on which at least one of a silicon oxide film and a silicon nitride film is formed as a film to be polished.

  As a polishing apparatus used in the polishing method of the present embodiment, for example, a holder for holding a substrate having a film to be polished and a motor or the like capable of attaching a polishing cloth (pad) and capable of changing the number of rotations are attached. A general polishing apparatus or the like having a certain polishing surface plate can be used.

  Examples of the polishing apparatus include a polishing apparatus manufactured by Ebara Corporation, a model number: EPO-111, a polishing apparatus manufactured by AMAT (Applied Materials), a trade name: Mira3400, a Reflection polishing machine, and the like.

  There is no restriction | limiting in particular as abrasive cloth, For example, a general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. can be used. Moreover, it is preferable that the polishing cloth is subjected to groove processing so that a polishing liquid is accumulated.

  The polishing conditions are not particularly limited, but from the viewpoint of suppressing the semiconductor substrate from popping out, the rotation speed of the polishing platen is preferably a low rotation of 200 rpm or less. The pressure applied to the semiconductor substrate (processing load) is preferably 100 kPa or less from the viewpoint of suppressing the generation of scratches after polishing.

  During polishing, it is preferable to continuously supply the polishing liquid to the surface of 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.

  As described above, the supply method of the polishing liquid is the A method in which the two liquids are fed through separate pipes, these pipes are joined, mixed immediately before the supply pipe outlet, and supplied onto the polishing platen. B method for mixing the liquid just before polishing, C method for supplying the two liquids separately onto the polishing platen, and D method for supplying a mixture of slurry and additive liquid in advance through a supply pipe .

  The semiconductor substrate after the polishing is preferably washed in running water, and then dried after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like. Thus, by polishing the inorganic insulating layer, which is a film to be polished, with the above polishing liquid, surface irregularities can be eliminated and a smooth surface can be obtained over the entire surface of the semiconductor substrate. By repeating this step a predetermined number of times, a semiconductor substrate having a desired number of layers can be manufactured.

Examples of a method for manufacturing a silicon oxide film and a silicon nitride film that are films to be polished include a low-pressure CVD method, a plasma CVD method, and the like. When a silicon oxide film is formed by a low pressure CVD method, monosilane: SiH ₄ can be used as the Si source, and oxygen: O ₂ can be used as the oxygen source. The 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. The silicon oxide film may be heat-treated at a temperature of 1000 ° C. or lower after the film is formed by the CVD method.

The silicon oxide film may be doped with an element such as phosphorus or boron. 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 that requires a high temperature can be performed at a low temperature under normal thermal equilibrium. There are two plasma generation methods, a capacitive coupling type and an inductive coupling type. As a reactive gas, SiH ₄ -N ₂ O-based gas using SiH ₄ as an Si source, N ₂ O as an oxygen source, and TEOS-O ₂ -based gas (TEOS) using tetraethoxysilane (TEOS) as an Si source. -Plasma CVD method). The substrate temperature is preferably 250 to 400 ° C., and the reaction pressure is preferably 67 to 400 Pa.

When a silicon nitride film is formed by a low pressure CVD method, dichlorosilane: SiH ₂ Cl ₂ can be used as the Si source, and ammonia: NH ₃ can be used as the nitrogen source. The silicon nitride film can be obtained by performing a SiH ₂ Cl ₂ —NH ₃ oxidation reaction at a high temperature of 900 ° C.

Examples of the reactive gas in the plasma CVD method include SiH ₄ —NH ₃ gas using SiH ₄ as a Si source and NH ₃ as a nitrogen source. The substrate temperature is preferably 300 to 400 ° C.

  The substrate used in this embodiment includes individual semiconductors such as diodes, transistors, compound semiconductors, thermistors, varistors, thyristors, DRAMs (dynamic random access memories), SRAMs (static random access memories), EPROM (Erasable Programmable Read Only Memory), Mask ROM (Mask Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), Flash Memory and other Memory Elements, Microprocessor, Theoretical circuit elements such as DSP and ASIC, integrated circuit elements such as compound semiconductors represented by MMIC (monolithic microwave integrated circuit), hybrid integrated circuits (hybrid IC), Diodes include a substrate having a photoelectric conversion element such as a charge coupled device.

  The CMP polishing liquid of the present embodiment is not only a silicon nitride film and a silicon oxide film formed on a semiconductor substrate, but also an inorganic insulating film such as a silicon oxide film, glass, and silicon nitride formed on a wiring board having a predetermined wiring. A film mainly containing polysilicon, Al, Cu, Ti, TiN, W, Ta, TaN or the like can be polished.

(Electronic parts)
The electronic component of this embodiment uses a substrate polished by the above-described polishing method. Electronic components include not only semiconductor elements but also optical glasses such as photomasks, lenses, and prisms, inorganic conductive films such as ITO, optical integrated circuits, optical switching elements, optical waveguides, and optical fibers composed of glass and crystalline materials. It includes 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, and the like.

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

(Preparation of cerium oxide ground powder)
Cerium carbonate hydrate: 40 kg was put in an alumina container and calcined in air at 830 ° C. for 2 hours to obtain 20 kg of yellowish white powder. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. Moreover, as a result of measuring the particle diameter of the fired powder with a laser diffraction particle size distribution meter, 95% or more of the particle diameter of the fired powder was distributed between 1 and 100 μm.

Next, 20 kg of the cerium oxide powder was dry pulverized using a jet mill. As a result of measuring the specific surface area of the polycrystal by the BET method, it was 9.4 m ² / g.

(Preparation of cerium oxide slurry)
Cerium oxide powder: 10.0 kg and deionized water: 116.65 kg are mixed, and a commercially available ammonium polyacrylate aqueous solution (weight average molecular weight: 8000, 40% by mass): 228 g is added as a dispersant, and cerium oxide dispersion is added. Got. After stirring the cerium oxide dispersion for 10 minutes, ultrasonic irradiation was performed in the pipe for feeding the liquid while feeding it to another container. The ultrasonic frequency was 400 kHz, and the cerium oxide dispersion was fed over 30 minutes.

  Into 500 mL beakers, 500 g ± 20 g of the fed cerium oxide dispersion was put and centrifuged. Centrifugation was carried out for 2 minutes under the conditions set so that the centrifugal force applied to the outer periphery was 500 G, and cerium oxide settled on the bottom of the beaker was removed.

  The solid content concentration of the obtained cerium oxide dispersion (cerium oxide slurry) was measured and found to be 4.0% by mass. The pH of this slurry was measured and found to be 9.0.

  Further, using a laser diffraction particle size distribution analyzer (manufactured by Horiba, Ltd., trade name: LA-920), the average particle diameter of the cerium oxide particles in the slurry was measured with a refractive index of 1.93 and a transmittance of 68%. As a result, it was 0.11 μm.

  Impurity ions (Na, K, Fe, Al, Zr, Cu, Si, Ti) in the cerium oxide slurry measured using an atomic absorption photometer [manufactured by Shimadzu Corporation, trade name: AA-6650] are The mass ratio was 1 ppm or less.

(Preparation of additive solution)
<Example 1>
The additive solution was prepared by the following steps.
Ultrapure water: 900 g is weighed into a 1000 mL container a.
A 40 mass% polyacrylic acid aqueous solution (weight average molecular weight: 3000): 10.0 g is put in a container a.
Surfactant: Polyethoxylate of 2,4,7,9-tetramethyl-5-decyne-4,7-diol: 15.0 g is placed in a container a.
Phosphoric acid: 85 mass% phosphoric acid aqueous solution is put into the container a so that it may become 8.5g.
The amount of addition is adjusted so that the pH of the additive solution is 7.0, and ammonia water (25% by mass aqueous solution) is placed in the container a.
An appropriate amount of ultrapure water was added so that the total amount was 1000 g to prepare an additive solution.

<Examples 2 to 11>
In the same manner as in Example 1, an additive solution was prepared by blending as shown in Table 1.

<Comparative Examples 1-7>
In the same manner as in Example 1, an additive solution was prepared by blending as shown in Table 2.

(Preparation of polishing liquid)
The above-mentioned cerium oxide slurry: 500 g, the additive solution prepared in Examples 1 to 11 and Comparative Examples 1 to 7 described above: 500 g, and pure water: 1500 g are mixed to prepare a total of 2500 g of CMP polishing liquid. did.

(Polishing evaluation)
Regarding the test wafer for insulating film CMP evaluation, a blanket wafer without a pattern is formed as a silicon oxide film having a film thickness of 1000 nm on a Si substrate and a film having a film thickness of 200 nm on a Si substrate. A silicon nitride film and a polysilicon film formed with a thickness of 100 nm on a Si substrate were used.

Further, as a pattern wafer on which a simulated pattern was formed, an 864 wafer (trade name, diameter: 200 mm) manufactured by SEMATECH was used. As shown in FIG. 2, the pattern wafer includes a silicon substrate 8 having a trench on the surface, a silicon nitride film 9 stacked on the silicon substrate 8 so as to avoid the trench, and a silicon substrate 8 and And a silicon oxide (SiO ₂ ) film (insulating film) 10 laminated on the silicon nitride film 9. The silicon oxide film 10 is formed by HDP (High Density Plasma) method, and the film thickness is 600 nm on both the silicon substrate 8 and the silicon nitride film 9. Specifically, the film thickness of the silicon nitride film 9 is 150 nm, the film thickness of the convex part of the silicon oxide film 10 is 600 nm, the film thickness of the concave part of the silicon oxide film 10 is 600 nm, and the silicon oxide film 10 The recess depth is 500 nm (trench depth 350 nm + silicon nitride film thickness 150 nm). In the polishing evaluation, the wafer was polished using a known CMP polishing liquid capable of sufficiently selectively polishing the silicon oxide film with respect to the silicon nitride film, and the silicon nitride film was exposed ( Pattern wafer A).
Further, a wafer having a structure similar to that of the pattern wafer A and having a polysilicon film thickness of 150 nm was used instead of the silicon nitride film (pattern wafer B).

For pattern wafer evaluation, a line (convex portion) & space (concave portion) width of 200 μm pitch and a convex pattern density of 50% were used. The line & space is a simulated pattern in which an active portion masked with Si ₃ N ₄ that is a convex portion and a trench portion that is formed with a groove that is a concave portion are alternately arranged. For example, “the line and space has a pitch of 100 μm” means that the total width of the line portion and the space portion is 100 μm. For example, “the convex pattern density is 10%” means a pattern in which the convex width: 10 μm and the concave width: 90 μm are alternately arranged, and the convex pattern density of 90% A width: 90 μm and a recess width: 10 μm mean a pattern in which the rows are arranged alternately.

  The test wafer was set on a holder of a polishing apparatus (Applied Materials, trade name: MIRRA 3400) on which a suction pad for attaching a substrate was attached. In addition, a polishing pad made of porous urethane resin (Rodel, model number: IC-1010) was attached to a polishing surface plate for a 200 mm wafer.

  A holder with the insulating film surface down was placed on the polishing pad, and the membrane pressure was set to 31 kPa.

On the polishing platen, the above-mentioned cerium oxide slurry was simultaneously dropped at a rate of 160 mL / min, and the addition liquids of Examples 1 to 11 and Comparative Examples 1 to 7 were simultaneously dropped at a rate of 40 mL / min. And the wafer were operated at 123 rpm and 113 rpm, respectively, and a blanket wafer of silicon oxide film (P-TEOS film), silicon nitride film, and polysilicon film was polished for 1 minute.
The pattern wafers A and B were polished for 100 seconds.
The polished wafer was thoroughly washed with pure water and then dried.

Thereafter, for the blanket wafer of silicon oxide film, silicon nitride film, and polysilicon film, an in-wafer surface 55 is used by using an optical interference film thickness apparatus (trade name: RE-3000, manufactured by Dainippon Screen Mfg. Co., Ltd.). The residual film thickness at the point was measured, and the polishing rate per minute was calculated from the amount of film thickness reduction before polishing. Regarding the pattern wafer, the remaining film thickness of the silicon nitride film of the pattern wafer A and the concave portion of the pattern wafer B are obtained using an optical interference film thickness apparatus (Dainippon Screen Mfg. Co., Ltd., trade name: RE-3000). The remaining film thickness of the insulating film and the remaining film thickness of the insulating film at the convex portion were measured. And the difference of the residual film thickness of the insulating film of the convex part of the pattern wafer B and the insulating film of a recessed part was made into flatness.
The obtained measurement results are shown in Tables 1 and 2 above.

  As shown in Tables 1 and 2, in Examples 1 to 11, the polishing rate ratio is that the silicon oxide film / polysilicon film is 64 to 110, the silicon nitride film / polysilicon film is 18 or more, and polysilicon. It can be seen that the polishing rate of the film is suppressed to 40 Å / min or less, and the polishing rate of the silicon oxide film and the silicon nitride film is improved while suppressing the polishing rate of the polysilicon film.

  When Examples 1-11 are compared with Comparative Examples 1-7, it is clear that in Examples 1-11, the polishing rate of the silicon nitride film is particularly improved. Also, from the evaluation results on the pattern wafer A, it is clear that in Examples 1 to 11, the silicon nitride film was sufficiently polished. Furthermore, from the evaluation results on the pattern wafer B, it can be seen that Examples 1 to 11 all have a small flatness value and good flatness.

  DESCRIPTION OF SYMBOLS 1 ... Silicon, 2 ... Insulator, 3 ... Insulating film, 4 ... Dummy gate, 5 ... Side wall, 6 ... Stress liner, 7 ... Silicon oxide film, 8 ... Silicon substrate, 9 ... Silicon nitride film, 10 ... Silicon oxide Membrane, 100, 200 ... substrate.

Claims (17)

A CMP polishing liquid used by mixing a first liquid and a second liquid,
The first liquid contains cerium-based abrasive grains containing cerium oxide particles, a dispersant, and water,
The second liquid contains a polyacrylic acid compound, a surfactant, at least one phosphoric acid compound of phosphoric acid or a phosphoric acid derivative, and water;
The pH of the first liquid is 7.0 or more;
The pH of the second liquid is 6.5 or more,
A CMP polishing liquid, wherein the first liquid and the second liquid are mixed so that the content of the phosphoric acid compound is 0.01 to 1.0% by mass based on the total mass of the CMP polishing liquid.   The CMP polishing liquid according to claim 1, wherein the second liquid contains a nonionic surfactant as the surfactant.   The CMP polishing liquid according to claim 1 or 2, wherein the first liquid contains a polyacrylic acid-based dispersant as the dispersant.   The phosphoric acid derivative is a polymer of phosphoric acid, sodium hydrogen phosphate, sodium phosphate, ammonium phosphate, potassium phosphate, calcium phosphate, sodium pyrophosphate, polyphosphoric acid, sodium polyphosphate, metaphosphoric acid, sodium metaphosphate and phosphorous. The CMP polishing liquid according to claim 1, which is at least one selected from the group consisting of ammonium acid. A CMP polishing liquid obtained by mixing a first liquid and a second liquid,
The pH of the first liquid is 7.0 or more;
The pH of the second liquid is 6.5 or more,
Containing cerium-based abrasive grains containing cerium oxide particles, a dispersant, a polyacrylic acid compound, a surfactant, at least one phosphoric acid or phosphoric acid derivative, and water,
CMP polishing liquid whose content of the said phosphoric acid compound is 0.01-1.0 mass% on the basis of CMP polishing liquid total mass.   The CMP polishing liquid according to claim 5, which contains a nonionic surfactant as the surfactant.   The CMP polishing liquid according to claim 5 or 6, comprising a polyacrylic acid-based dispersant as the dispersant.   The phosphoric acid derivative is a polymer of phosphoric acid, sodium hydrogen phosphate, sodium phosphate, ammonium phosphate, potassium phosphate, calcium phosphate, sodium pyrophosphate, polyphosphoric acid, sodium polyphosphate, metaphosphoric acid, sodium metaphosphate and phosphorous. CMP polishing liquid as described in any one of Claims 5-7 which is at least 1 type chosen from the group which consists of ammonium acid.   In order to polish and remove at least a part of the film to be polished using the polysilicon film of the substrate on which at least one of the silicon oxide film or the silicon nitride film and the polysilicon film is formed as a stopper film CMP polishing liquid as described in any one of Claims 1-8 used for.   The CMP polishing liquid according to any one of claims 1 to 8, which is used for polishing and removing at least a part of a silicon nitride film.   The CMP polishing liquid according to any one of claims 1 to 8, which is used for polishing and removing at least a part of a silicon oxide film and at least a part of a silicon nitride film.   A polishing method for a substrate, comprising: a polishing step for polishing the polishing target film of the substrate having a polishing target film formed on at least one surface thereof using the CMP polishing liquid according to claim 1. . A cerium-based abrasive containing cerium oxide particles, a first liquid containing a dispersant and water and having a pH of 7.0 or more, and at least a polyacrylic acid compound, a surfactant, phosphoric acid or a phosphoric acid derivative One phosphoric acid compound and a second liquid containing water and having a pH of 6.5 or more are mixed, and the content of the phosphoric acid compound is 0.01 to based on the total mass of the CMP polishing liquid. A polishing liquid preparation step of obtaining a CMP polishing liquid of 1.0% by mass;
A polishing step of polishing the polishing target film of the substrate having the polishing target film formed on at least one surface using the CMP polishing liquid.   The method for polishing a substrate according to claim 12, wherein the one surface of the substrate has a step. At least one of a silicon oxide film or a silicon nitride film is formed as the film to be polished on the substrate,
A polysilicon film is formed between the substrate and the film to be polished,
The substrate polishing method according to any one of claims 12 to 14, wherein in the polishing step, at least a part of the film to be polished is polished and removed using the polysilicon film as a stopper film. A silicon nitride film is formed as the film to be polished on the substrate,
The method for polishing a substrate according to claim 12, wherein in the polishing step, at least a part of the silicon nitride film is polished and removed. A silicon oxide film and a silicon nitride film are formed as the film to be polished on the substrate,
The method for polishing a substrate according to any one of claims 12 to 14, wherein in the polishing step, at least a part of the silicon oxide film and at least a part of the silicon nitride film are polished and removed.

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