Semiconductor substrate manufacturing method and semiconductor substrate obtained by said manufacturing method

Abstract

To provide a semiconductor substrate manufacturing method arranged to have means for reducing a cleaning residue of a substrate surface and to use a polishing composition containing no less than a given amount of a water-soluble polymer having a lactam structure.SOLUTION: The method comprises: a chemical mechanical polishing step of polishing a target by chemical mechanical polishing means, using a polishing composition containing abrasive grains and a water-soluble polymer having a lactam structure; and a surface treatment step of performing a surface treatment on a polished target obtained by the chemical mechanical polishing step, using a surface treatment composition containing at least one kind of ammonia (salt). A content of the water-soluble polymer is 0.1 ppm or more and 500 ppm or less to a total mass of the polishing composition, a content of the ammonia (salt) is 100 ppm or more and 10000 ppm or less to a total mass of the surface treatment composition, and pH of the surface treatment composition is 8.0 or more and 12.0 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a semiconductor substrate and a semiconductor substrate obtained by the manufacturing method. [Background technology]

[0002] In recent years, new microfabrication technologies have been developed to accompany the high integration and high performance of LSI (Large Scale Integration). Chemical mechanical polishing (CMP) is one of these technologies, and is frequently used in the LSI manufacturing process, especially in the multi-layer wiring formation process, for planarizing interlayer insulating films, forming metal plugs, and forming buried wiring (damascene wiring).

[0003] CMP has been applied to various processes in semiconductor manufacturing, and one example of such application is the gate formation process in transistor fabrication. When fabricating a transistor, Si-containing materials such as silicon, silicon oxide film (silicon oxide), polycrystalline silicon (polysilicon), and silicon nitride (silicon nitride) may be polished, and depending on the transistor structure, it is necessary to control the polishing rate of each Si-containing material.

[0004] The polishing composition used in CMP may contain a water-soluble polymer for the purpose of protecting the surface of the object to be polished, etc. For example, Patent Document 1 describes a polishing method for polishing a polysilicon film provided on a silicon substrate having an isolation region, in which the content of the water-soluble polymer in the preliminary polishing composition and the finish polishing composition is controlled within a predetermined range in order to suppress dishing of the polysilicon. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-103515 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, according to the inventors' investigations, it was found that when CMP is performed using a polishing composition containing a water-soluble polymer having a lactam structure such as polyvinylpyrrolidone, a large amount of residue (impurities; defects) remains on the surface of the semiconductor substrate after CMP.

[0007] Therefore, an object of the present invention is to provide a means for reducing residues on the substrate surface in a method for producing a semiconductor substrate using a polishing composition containing a water-soluble polymer having a lactam structure. [Means for solving the problem]

[0008] In order to solve the above problems, the present inventors have conducted extensive research and have found that the above problems can be solved by chemically mechanically polishing an object to be polished using a polishing composition containing a water-soluble polymer having a lactam structure, and then performing surface treatment using an alkaline surface treatment composition containing a specific amount of ammonia (salt), thereby completing the present invention.

[0009] That is, the method for manufacturing a semiconductor substrate according to one embodiment of the present invention comprises a chemical mechanical polishing step of chemically and mechanically polishing an object to be polished using a polishing composition containing abrasive grains and a water-soluble polymer having a lactam structure, and a surface treatment step of surface-treating the polished object obtained in the chemical mechanical polishing step using a surface treatment composition containing at least one kind of ammonia (salt).The content of the water-soluble polymer is 0.1 ppm or more and 500 ppm or less with respect to the total mass of the polishing composition, the content of the ammonia (salt) is 100 ppm or more and 10,000 ppm or less with respect to the total mass of the surface treatment composition, and the pH of the surface treatment composition is 8.0 or more and 12.0 or less. Effect of the Invention

[0010] According to the present invention, in a method for producing a semiconductor substrate using a polishing composition containing a specific amount or more of a water-soluble polymer having a lactam structure, the amount of residue on the substrate surface can be reduced. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a polishing target (a silicon wafer having a poly-Si patterned wafer formed on its surface) used in evaluation of the polishing state (dishing). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention relates to a method for producing a semiconductor substrate, which comprises a chemical mechanical polishing step of chemically and mechanically polishing an object to be polished using a polishing composition containing an abrasive grain and a water-soluble polymer having a lactam structure, and a surface treatment step of surface treating the polished object obtained in the chemical mechanical polishing step using a surface treatment composition containing at least one kind of ammonia (salt). The content of the water-soluble polymer is 0.1 ppm or more and 500 ppm or less with respect to the total mass of the polishing composition, the content of the ammonia (salt) is 100 ppm or more and 10,000 ppm or less with respect to the total mass of the surface treatment composition, and the pH of the surface treatment composition is 8.0 or more and 12.0 or less. According to the production method of the present invention having such a configuration, residues on the substrate surface can be reduced. In addition, the polished state of the substrate can be maintained in a good condition.

[0013] The mechanism by which the above-mentioned effects are obtained is believed to be as follows: However, the following mechanism is merely speculation, and the scope of the present invention is not limited thereto.

[0014] According to the investigations conducted by the present inventors, it is believed that the following two types of residues are generated in the method for producing a semiconductor substrate of the present invention.

[0015] When the pH of the polishing composition is in the alkaline range (pH 8.0 to 12.0), Si contained in the object to be polished is dissolved as silicate ions into the polishing composition in the chemical mechanical polishing process. The silicate ions are then attracted to a water-soluble polymer (e.g., polyvinylpyrrolidone) having a lactam structure to form a water-soluble polymer-silicate ion complex. When the pH of the substrate surface becomes 7.5 or less in a subsequent process (e.g., a water washing process), the complex precipitates as a salt, and the precipitate remains as a residue on the surface of the polished object to be polished.

[0016] Furthermore, when the pH of the polishing composition is in the acidic to alkaline range (pH 2.0 or higher and 12.0 or lower), in the chemical mechanical polishing process, the abrasive grains contained in the polishing composition and a water-soluble polymer having a lactam structure (e.g., polyvinylpyrrolidone) form a water-soluble polymer-abrasive grain complex, and the complex remains as a residue on the surface of the polished object.

[0017] The ammonia (salt) contained in the surface treatment composition according to the present invention is ammonium ion (NH4 + ) and ammonia. The ammonium ions and ammonia penetrate between the water-soluble polymer and the wafer, and as a result, have the effect of making the water-soluble polymer easier to peel off. This action is thought to peel off the precipitate of the water-soluble polymer-silicate ion complex and the water-soluble polymer-abrasive grain complex from the surface of the polished object, reducing the residue.

[0018] Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited to the following embodiments.

[0019] In this specification, unless otherwise specified, operations and measurements of physical properties are performed under conditions of room temperature (20° C. or higher and 25° C. or lower) and relative humidity of 40% RH or higher and 50% RH or lower.

[0020] In addition, in this specification, "(meth)acrylic" is meant to collectively refer to acrylic and methacrylic, and "(meth)acrylate" is meant to collectively refer to acrylate and methacrylate.

[0021] <Chemical mechanical polishing process> In this step, an object to be polished is chemically and mechanically polished using a polishing composition containing abrasive grains and a water-soluble polymer having a lactam structure.

[0022] [Polished object] The object to be polished according to the present invention is not particularly limited as long as it is a material that constitutes a semiconductor substrate, for example, polysilicon (polycrystalline silicon), single crystal silicon, silicon nitride, silicon carbonitride (SiCN), silicon oxide, SiGe, or other silicon (Si)-containing material, and metal.

[0023] Examples of objects to be polished that contain silicon oxide include a TEOS-type silicon oxide surface (hereinafter simply referred to as "TEOS") produced using tetraethyl orthosilicate as a precursor, a high density plasma (HDP) film, an undoped silicate glass (USG) film, a phosphorus silicate glass (PSG) film, a boron-phosphorus silicate glass (BPSG) film, and a rapid thermal oxidation (RTO) film.

[0024] Examples of the metal include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

[0025] Among them, the object to be polished preferably contains at least one material containing silicon (Si), and more preferably contains polysilicon. As described above, the material containing silicon (Si) (particularly polysilicon) forms a water-soluble polymer-silicate ion complex, and the precipitate of the complex is likely to remain as a residue on the surface of the polished object. Therefore, the object to be polished containing a material containing silicon (Si) (particularly polysilicon) is more likely to cause the problem of the present invention. In other words, it can be said that the present invention is particularly suitable when the object to be polished contains a material containing silicon (Si) (particularly polysilicon). Therefore, according to a preferred embodiment of the present invention, the object to be polished contains polysilicon.

[0026] [Polishing composition] The polishing composition of the present invention contains abrasive grains and a water-soluble polymer having a lactam structure.

[0027] (Abrasive grain) The abrasive grains contained in the polishing composition of the present invention have the effect of mechanically polishing an object to be polished, and improve the polishing rate of the object to be polished by the polishing composition.

[0028] In the polishing composition according to the present invention, the abrasive grains are not particularly limited. The types of abrasive grains include particles made of metal oxides such as silica, alumina, zirconia, and titania. The abrasive grains may be used alone or in combination of two or more kinds. The abrasive grains may be commercially available products or synthetic products. Among these abrasive grains, silica is preferred, fumed silica and colloidal silica are more preferred, and colloidal silica is even more preferred. Thus, according to a preferred embodiment of the present invention, the abrasive grains include silica (silica particles). In a more preferred embodiment, the abrasive grains include colloidal silica (colloidal silica particles).

[0029] The colloidal silica can be produced by a method such as a sodium silicate method or a sol-gel method, and any method for producing the colloidal silica can be suitably used as the abrasive grains according to the present embodiment. Among them, the colloidal silica produced by the sol-gel method, which can produce the colloidal silica with high purity, is preferred.

[0030] The size of the abrasive grains is not particularly limited. For example, the average primary particle diameter of the abrasive grains is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. As the average primary particle diameter of the abrasive grains increases, the polishing speed of the object to be polished by the polishing composition increases. In addition, the average primary particle diameter of the abrasive grains is preferably 300 nm or less, more preferably 100 nm or less, even more preferably 50 nm or less, and most preferably 30 nm or less. As the average primary particle diameter of the abrasive grains decreases, it becomes easier to obtain a surface with fewer defects by polishing using the polishing composition. That is, the average primary particle diameter of the abrasive grains is preferably 10 nm or more and 300 nm or less, more preferably 15 nm or more and 100 nm or less, even more preferably 20 nm or more and 50 nm or less, and most preferably 20 nm or more and 30 nm or less. The average primary particle diameter of the abrasive grains can be calculated, for example, based on the specific surface area (SA) of the abrasive grains calculated by the BET method, assuming that the shape of the abrasive grains is a true sphere. In this specification, the average primary particle size of the abrasive grains is a value measured by the method described in the Examples.

[0031] In addition, the average secondary particle diameter of the abrasive grains is preferably 20 nm or more, more preferably 30 nm or more, and even more preferably 35 nm or more. As the average secondary particle diameter of the abrasive grains increases, the resistance during polishing decreases, enabling stable polishing. In addition, the average secondary particle diameter of the abrasive grains is preferably 400 nm or less, more preferably 250 nm or less, even more preferably 100 nm or less, and most preferably 70 nm or less. As the average secondary particle diameter of the abrasive grains decreases, the surface area per unit mass of the abrasive grains increases, the contact frequency with the object to be polished increases, and the polishing rate increases. That is, the average secondary particle diameter of the abrasive grains is preferably 20 nm or more and 400 nm or less, more preferably 30 nm or more and 250 nm or less, even more preferably 35 nm or more and 100 nm or less, and particularly preferably 35 nm or more and 70 nm or less. The average secondary particle diameter of the abrasive grains can be measured, for example, by dynamic light scattering. In this specification, the average secondary particle diameter of the abrasive grains is a value measured by the method described in the Examples.

[0032] In the polishing composition according to the present invention, the content (concentration) of the abrasive grains is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably more than 0.5% by mass, based on the total mass of the polishing composition. The upper limit of the content of the abrasive grains is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably less than 5% by mass, based on the total mass of the polishing composition. That is, the content of the abrasive grains is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.2% by mass or more and 10% by mass or less, even more preferably 0.5% by mass or more and 5% by mass or less, and particularly preferably more than 0.5% by mass and less than 5% by mass, based on the total mass of the polishing composition. Within such a range, a high polishing rate can be obtained while suppressing costs, and efficient processing can be achieved. In addition, when the polishing composition contains two or more types of abrasive grains, the content of the abrasive grains refers to the total amount of these.

[0033] (Water-soluble polymer) The polishing composition according to the present invention contains a water-soluble polymer having a lactam structure (cyclic amide structure). The water-soluble polymer adheres to the surface of the object to be polished and protects the surface of the object to be polished from uneven or excessive etching. This can improve the surface quality after polishing. In particular, when the object to be polished contains polysilicon, the bond distance of the Si-Si bond of the polysilicon is extended due to the nucleophilic action of the unshared electron pair present in the nitrogen atom of the lactam structure. This makes the Si-Si bond embrittled, facilitating the polishing of the polysilicon. As a result, steps and dishing in the polysilicon film can be suppressed.

[0034] In this specification, "water-soluble" means that the solubility in water (25°C) is 1 g / 100 mL or more, and "polymer" means a (co)polymer having a weight-average molecular weight of 1,000 or more. The weight-average molecular weight can be measured by gel permeation chromatography (GPC), and specifically, the value measured by the following measurement method is used.

[0035] (GPC measurement conditions) Measuring device: HLC-8320GPC (Tosoh) Sample concentration: 0.01% by mass Column: TSKgel GMPWXL Detector: Differential refractometer Eluent: 10 mM lithium bromide dissolved in N,N-dimethylformamide Flow rate: 1mL / min Measurement temperature: 40℃ Molecular weight conversion: Polyethylene glycol conversion Sample injection volume: 200 μL.

[0036] In addition, only when it is not possible to measure by GPC, the molecular weight calculated from the molecular formula is adopted as the weight average molecular weight.

[0037] The water-soluble polymer may contain structural units derived from N-vinyl lactam monomers at a ratio of more than 50% by mass relative to the total amount of structural units. The content of structural units derived from N-vinyl lactam monomers in the water-soluble polymer is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass (i.e., homopolymer of N-vinyl lactam monomers).

[0038] Examples of N-vinyl lactam monomers include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinyl-2-caprolactam, N-vinyl-2-piperidone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, etc. Among them, N-vinyl-2-pyrrolidone is preferred in terms of the balance between protection of the surface of the object to be polished and improvement of the polishing rate.

[0039] These N-vinyl lactam monomers may be used alone or in combination of two or more.

[0040] The N-vinyl lactam monomer may contain a structural unit derived from another copolymerizable monomer that is copolymerizable with the N-vinyl lactam monomer, if necessary.

[0041] Examples of other copolymerizable monomers include N-acryloylmorpholine, N-vinylpiperidine, N-vinylimidazole, N-vinylcarbazole, (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nn-butyl(meth)acrylamide, N-sec-butyl(meth)acrylamide, and N-tert-butyl(meth)acrylamide; N,N-dimethyl(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(tert-butyl)(meth)acrylamide; N-hydroxyalkyl(meth)acrylamides such as N-hydroxymethyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide; N-vinyl carboxylates such as N-vinylacetamide; carboxylic acid amides; N-hydroxyalkyl (meth)acrylamides such as N-(2-hydroxyethyl) (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, N-(1-hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, and N-(4-hydroxybutyl) (meth)acrylamide; N-alkoxyalkyl (meth)acrylamides such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide; nitrogen atom-containing monomers such as N,N-dimethylaminopropyl (meth)acrylamide; carboxy group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride;Alkyl (meth)acrylate monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; (meth)acrylate monomers having an alicyclic structure such as cyclohexyl (meth)acrylate, cyclohexyloxyalkyl (meth)acrylate, t-butylcyclohexyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, (Meth)acrylate monomers containing an alkoxy group or an oxyalkylene group, such as acrylate, methoxypolyethylene glycol (meth)acrylate, and polypropylene glycol mono(meth)acrylate; cyano group-containing monomers, such as acrylonitrile and methacrylonitrile; sulfur atom-containing monomers, such as allylsulfonic acid, styrenesulfonic acid, and vinylsulfonic acid; olefins, such as ethylene, propylene, butadiene, isoprene, and isobutylene; styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl stearate, alkyl vinyl ethers, vinyl toluene, vinyl pyridine, itaconic acid dialkyl esters, fumaric acid dialkyl esters, vinyl alcohol, allyl alcohol, methyl vinyl ketone, allyl trimethyl ammonium chloride, and dimethyl allyl vinyl ketone.

[0042] These other copolymerizable monomers may be used either individually or in combination of two or more.

[0043] Specific preferred examples of the water-soluble polymer include homopolymers such as poly(N-vinylpyrrolidone) (PVP) and polyvinylcaprolactam (PVC); and copolymers such as poly(1-vinylpyrrolidone-co-vinyl acetate), poly(vinylpyrrolidone-co-methacrylamide-co-n-vinylimidazole), and poly(vinylpyrrolidone-co-vinyl alcohol). Among these, taking into consideration the balance between protection of the surface of the object to be polished and improvement of the polishing rate, poly(N-vinylpyrrolidone) (PVP) and poly(1-vinylpyrrolidone-co-vinyl acetate) are more preferred, and poly(N-vinylpyrrolidone) (PVP) is even more preferred.

[0044] The lower limit of the weight average molecular weight (Mw) of the water-soluble polymer is not particularly limited, but is preferably 1000 or more, more preferably more than 1000, even more preferably 1500 or more, even more preferably more than 1500, particularly preferably 5000 or more, and most preferably more than 5000. The upper limit of the weight average molecular weight of the water-soluble polymer is not particularly limited, but is preferably 100,000 or less, more preferably less than 100,000, even more preferably 90,000 or less, even more preferably less than 90,000, even more preferably 80,000 or less, particularly preferably less than 80,000, and most preferably 55,000 or less. That is, the weight average molecular weight of the water-soluble polymer is preferably 1000 or more and 100000 or less, more preferably more than 1000 and less than 100000, even more preferably 1500 or more and 90000 or less, even more preferably more than 1500 and less than 90000, even more preferably 5000 or more and 80000 or less, particularly preferably more than 5000 and less than 80000, and most preferably more than 5000 and 55000 or less. A water-soluble polymer having a weight average molecular weight in the above range has excellent solubility and a good balance between protection of the surface of the object to be polished and improvement of the polishing rate.

[0045] The weight average molecular weight of the water-soluble polymer can be measured by gel permeation chromatography (GPC).

[0046] The content (concentration) of the water-soluble polymer is 0.1 ppm or more and 500 ppm or less with respect to the total mass of the polishing composition. If the content is less than 0.1 ppm, the protective effect of the water-soluble polymer on the surface of the object to be polished and the effect of improving the polishing rate are insufficient. If the content exceeds 500 ppm, the protective film of the water-soluble polymer becomes too thick, and the water-soluble polymer itself may remain on the substrate surface as a residue. In addition, the above-mentioned precipitate of the water-soluble polymer-silicic acid ion complex and the water-soluble polymer-abrasive grain complex may be excessively generated and may not be completely removed in the surface treatment process described below. From the same viewpoint, the content of the water-soluble polymer is preferably 0.1 ppm or more and 300 ppm or less, more preferably 1 ppm or more and 100 ppm or less, even more preferably 5 ppm or more and 70 ppm or less, and particularly preferably 10 ppm or more and 50 ppm or less. In addition, when the polishing composition contains two or more water-soluble polymers, the content of the water-soluble polymers refers to the total amount of these.

[0047] (dispersion medium) The polishing composition according to the present invention preferably contains a dispersion medium for dispersing each component. Examples of the dispersion medium include water; alcohols such as methanol, ethanol, and ethylene glycol; ketones such as acetone, and mixtures thereof. Of these, water is preferable as the dispersion medium. That is, according to a more preferred embodiment of the present invention, the dispersion medium contains water. According to a further preferred embodiment of the present invention, the dispersion medium is substantially composed of water. Note that the above "substantially" means that a dispersion medium other than water may be included as long as the objective effect of the present invention can be achieved, and more specifically, the dispersion medium is preferably composed of 90% by mass or more and 100% by mass or less of water and 0% by mass or more and 10% by mass or less of a dispersion medium other than water, and more preferably composed of 99% by mass or more and 100% by mass or less of water and 0% by mass or more and 1% by mass or less of a dispersion medium other than water. As described above, more preferably, the dispersion medium is composed of only water.

[0048] From the viewpoint of not inhibiting the action of the components contained in the polishing composition, it is preferable for the dispersion medium to be water that contains as few impurities as possible. Specifically, pure water or ultrapure water from which impurity ions have been removed with an ion exchange resin and then foreign matter has been removed through a filter, or distilled water is more preferable.

[0049] (Other Ingredients) The polishing composition of the present invention may further contain, as necessary, known additives that can be used in polishing compositions, such as surfactants, complexing agents, preservatives, and anti-fungal agents, to the extent that the effects of the present invention are not significantly impeded.

[0050] The polishing composition according to the present invention preferably does not substantially contain an oxidizing agent. If an oxidizing agent is contained in the polishing composition, the surface of the object to be polished (e.g., polysilicon) is oxidized to generate an oxide film, which may lengthen the polishing time. Specific examples of the oxidizing agent include hydrogen peroxide (H2O2), sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate. The polishing composition substantially does not contain an oxidizing agent means that the oxidizing agent is not intentionally contained at least. Therefore, a polishing composition that inevitably contains a small amount of an oxidizing agent due to raw materials, manufacturing method, etc. is included in the concept of a polishing composition that does not substantially contain an oxidizing agent. For example, the concentration of the oxidizing agent in the polishing composition is preferably 0.001% by mass or less, more preferably 0.0001% by mass or less, and even more preferably 0.00001% by mass or less (lower limit: 0% by mass).

[0051] (pH) The pH of the polishing composition of the present invention is not particularly limited, but is preferably 2.0 or more and 12.0 or less, more preferably 4.0 or more and 11.0 or less, and even more preferably 8.0 or more and 11.0 or less. If the pH is within the above range, good chemical mechanical polishing can be achieved. The pH of the polishing composition is measured by the method described in the examples below.

[0052] The polishing composition of the present invention may have a pH adjusted by adding a pH adjuster within a range that does not impair the effects of the present invention.

[0053] The pH adjuster may be either an acid or a base, and may be either an inorganic compound or an organic compound. The pH adjuster may be used alone or in combination of two or more kinds.

[0054] Specific examples of acids used as pH adjusters include inorganic acids such as sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid; carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, and lactic acid; and organic acids such as organic sulfuric acids such as methanesulfonic acid, ethanesulfonic acid, and isethionic acid.

[0055] Specific examples of the base used as the pH adjuster include hydroxides or salts of Group 1 elements, hydroxides or salts of Group 2 elements, quaternary ammonium hydroxide or its salt, etc. Specific examples of the salts include carbonates, hydrogen carbonates, sulfates, acetates, etc.

[0056] The amount of the pH adjuster added is not particularly limited, and may be appropriately adjusted so that the polishing composition has a desired pH.

[0057] (Method of manufacturing the polishing composition) The method for producing the polishing composition according to the present invention is not particularly limited, and can be obtained, for example, by stirring and mixing abrasive grains, a water-soluble polymer, and other additives in a dispersion medium (e.g., water). The details of each component are as described above.

[0058] The temperature at which the components are mixed is not particularly limited, but is preferably 10° C. to 40° C., and may be heated to increase the dissolution rate. The mixing time is also not particularly limited as long as the components can be mixed uniformly.

[0059] (chemical mechanical polishing) As a polishing apparatus for chemical mechanical polishing, a general polishing apparatus can be used which is equipped with a holder for holding a substrate having an object to be polished, a motor capable of changing the rotation speed, and the like, and has a polishing platen onto which a polishing pad (polishing cloth) can be attached.

[0060] The polishing pad may be made of any material, including general nonwoven fabric, polyurethane, and porous fluororesin, without any particular limitations. The polishing pad is preferably provided with grooves for retaining the polishing composition.

[0061] Regarding the polishing conditions, for example, the rotation speed of the polishing platen was 10 rpm (0.17 s -1 ) or more 500rpm (8.3s -1 ) or less. The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 psi (3.4 kPa) or more and 10 psi (68.9 kPa) or less. The method of supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying the composition using a pump or the like is used. There is no limit to the amount of supply, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.

[0062] <Surface treatment process> In this step, the polished object obtained in the chemical mechanical polishing step is surface-treated with a surface treatment composition containing at least one type of ammonia (salt).

[0063] [Surface treatment composition] The surface treatment composition according to the present invention contains at least one type of ammonia (salt), and may contain other components as necessary.

[0064] (Ammonia (salt)) In this specification, the term "ammonia (salt)" refers to ammonia (NH3) and its salts (ammonium salts) in a comprehensive sense. As described above, ammonia (salt) is a compound that converts ammonium ions (NH4 + ) and ammonia, and has the effect of facilitating the removal of water-soluble polymers with lactam structures. It is presumed that this effect allows the removal of residues such as precipitates of water-soluble polymer-silicate ion complexes and water-soluble polymer-abrasive grain complexes from the surface of a polished object.

[0065] The above-mentioned salt of ammonia (ammonium salt) may be either an ammonium salt of an inorganic acid or an ammonium salt of an organic acid. Examples of the ammonium salt of an inorganic acid include ammonium chloride, ammonium sulfate, ammonium amidosulfate, ammonium nitrate, monoammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium diphosphite, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfide, ammonium borate, and ammonium fluoroborate. Examples of the ammonium salt of an organic acid include ammonium formate, ammonium acetate, diammonium oxalate, ammonium hydrogen oxalate, ammonium benzoate, monoammonium citrate, diammonium citrate, triammonium citrate, ammonium lactate, ammonium phthalate, ammonium succinate, monoammonium tartrate, diammonium tartrate, and ammonium aspartate. Among them, ammonium acetate is preferred.

[0066] These ammonia (salts) can be used alone or in combination of two or more.

[0067] In the surface treatment composition according to the present invention, the content (concentration) of ammonia (salt) is 100 ppm or more and 10000 ppm or less with respect to the total mass of the surface treatment composition. If the content of ammonia (salt) is less than 100 ppm, the residue reduction effect of the present invention may not be fully exhibited. On the other hand, if the content of ammonia (salt) exceeds 10000 ppm, the polished object may be etched and a good polishing state may not be maintained. From the same viewpoint, the content of ammonia (salt) is preferably 100 ppm or more and 8000 ppm or less, more preferably 300 ppm or more and 3000 ppm or less. In addition, when the surface treatment composition contains two or more kinds of ammonia (salt), the content of ammonia (salt) refers to the total amount of these.

[0068] (Potassium compounds) The surface treatment composition according to the present invention preferably further contains at least one potassium compound selected from the group consisting of potassium hydroxide and potassium salts. The potassium compound in the surface treatment composition, like the above-mentioned ammonia (salt), has the effect of making it easier to peel off the water-soluble polymer having a lactam structure. It is presumed that this effect makes it possible to peel off residues such as precipitates of the water-soluble polymer-silicate ion complex and water-soluble polymer-abrasive grain complex from the surface of the polished object. As a result, the effect of reducing residues can be further improved.

[0069] The potassium salt is not particularly limited, and can be appropriately selected from inorganic salts of potassium and organic salts of potassium. Examples of inorganic salts of potassium include potassium chloride, potassium bromide, potassium iodide, potassium carbonate, potassium hydrogen carbonate, potassium nitrate, potassium sulfate, potassium hydrogen sulfate, potassium perchlorate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium phosphate, potassium pyrophosphate, potassium etidronate, etc. Examples of organic salts of potassium include potassium acetate, potassium propionate, potassium citrate, etc.

[0070] Among the potassium compounds, from the viewpoint of pH when dissolved in water, potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, dipotassium hydrogen phosphate, and potassium phosphate are preferred, and potassium hydroxide, potassium carbonate, and potassium hydrogen carbonate are more preferred.

[0071] These potassium compounds may be used alone or in combination of two or more.

[0072] In the surface treatment composition according to the present invention, the content (concentration) of the potassium compound is preferably 100 ppm or more and 10,000 ppm or less with respect to the total mass of the surface treatment composition. When the content of the potassium compound is 100 ppm or more, the residue reduction effect can be improved. On the other hand, when the content of the potassium compound is 10,000 ppm or less, etching of the polished object is suppressed. Therefore, according to a preferred embodiment of the present invention, the surface treatment composition further contains at least one potassium compound selected from the group consisting of potassium hydroxide and potassium salts, and the content of the potassium compound is 100 ppm or more and 10,000 ppm or less with respect to the total mass of the surface treatment composition. From the same viewpoint, the content of the potassium compound is more preferably 100 ppm or more and 1000 ppm or less. In addition, when the surface treatment composition contains two or more potassium compounds, the content of the potassium compound means the total amount of these.

[0073] (dispersion medium) The surface treatment composition according to the present invention preferably contains a dispersion medium for dispersing each component. The preferred form of the dispersion medium contained in the surface treatment composition is the same as the preferred form described in the section on the polishing composition, so detailed description is omitted here.

[0074] (Other ingredients) The surface treatment composition of the present invention may further contain known additives that can be used in surface treatment compositions as necessary, as long as the effect of the present invention is not significantly hindered. However, it is desirable to not contain as many components as possible other than the essential components of the surface treatment composition of the present invention, since they may cause residues, so it is preferable that the content is as low as possible, and more preferably that they are not contained at all. The other components are not particularly limited, but examples thereof include abrasive grains, preservatives, reducing agents, oxidizing agents, etc.

[0075] (pH) The pH of the surface treatment composition of the present invention is 8.0 or more and 12.0 or less. When the pH is 8.0 or more, the ammonium ion (NH4 + ) is present in an increased amount. As a result, the effect of reducing residues can be improved. If the pH is 12.0 or less, etching of the polished object is suppressed, and a good polishing state can be maintained. From the same viewpoint, the pH of the surface treatment composition is preferably 8.5 or more and 11.0 or less, more preferably 9.0 or more and 10.5 or less, and even more preferably 9.0 or more and 10.0 or less. The pH of the surface treatment composition is a value measured by the method described in the Examples below.

[0076] In the surface treatment composition of the present invention, ammonia (salt) and potassium compound also play the role of a pH adjuster. When it is difficult to obtain the desired pH with these components alone, a pH adjuster may be added to adjust the pH within a range that does not impair the effects of the present invention. The preferred form of the pH adjuster contained in the surface treatment composition is the same as the preferred form explained in the section on the polishing composition, so a detailed explanation is omitted here. However, among the pH adjusters explained in the section on the polishing composition, those corresponding to ammonia (salt) and potassium compound are not treated as pH adjusters in the surface treatment composition.

[0077] (Method of manufacturing surface treatment composition) The method for producing the surface treatment composition according to the present invention is not particularly limited, and can be obtained, for example, by stirring and mixing ammonia (salt), a potassium compound added as necessary, and other components in a dispersion medium (e.g., water). The details of each component are as described above.

[0078] The temperature at which the components are mixed is not particularly limited, but is preferably 10° C. to 40° C., and may be heated to increase the dissolution rate. The mixing time is also not particularly limited as long as the components can be mixed uniformly.

[0079] (Surface treatment) In this specification, the surface treatment refers to a treatment for removing residues on the surface of a polished object, and represents a treatment for performing cleaning in a broad sense. The surface treatment method according to one embodiment of the present invention is performed by a method in which a surface treatment composition is directly contacted with a polished object. The surface treatment is not particularly limited, but is preferably performed by, for example, a rinse polishing treatment or a cleaning treatment.

[0080] According to a preferred embodiment of the present invention, the surface treatment is preferably a rinse polishing treatment, because, although the details are unclear, the residue removing effect of the above-mentioned surface treatment composition is more pronounced in the rinse polishing treatment.

[0081] In this specification, the rinse polishing process refers to a process that is carried out on a polishing table (platen) on which a polishing pad is attached, and removes residues on the surface of a polished object by the frictional force (physical action) of the polishing pad and the action of a surface treatment composition. A specific example of the rinse polishing process is a process in which, after a final polishing (finish polishing) is carried out on the object to be polished, the polished object is placed on the polishing table (platen) of a polishing device, the polished object is brought into contact with the polishing pad, and the polished object and the polishing pad are made to slide relative to each other while supplying a surface treatment composition to the contact portion.

[0082] Therefore, according to a preferred embodiment of the present invention, there is provided a method for manufacturing a semiconductor substrate, in which the surface treatment step is performed by contacting at least one surface of a polished object placed on a polishing table (platen) to which a polishing pad is attached with the polishing pad, and treating the polished object by sliding the polished object against the polishing pad relative to one another while supplying a surface treatment composition to the contact portion.

[0083] The rinse polishing treatment is preferably carried out using a general polishing device, which is equipped with a holder for holding the object to be polished, a motor capable of changing the rotation speed, and a polishing platen to which a polishing pad (polishing cloth) can be attached, although there is no particular limitation. As the polishing device, either a single-sided polishing device or a double-sided polishing device may be used. As the polishing pad, general nonwoven fabric, polyurethane, porous fluororesin, etc. can be used without any particular limitation. The polishing pad is preferably grooved so that the surface treatment composition can be accumulated. In addition, when the chemical mechanical polishing and the rinse polishing treatment are carried out using the same polishing device, it is preferable that the polishing device is equipped with a nozzle for discharging the surface treatment composition according to the present invention in addition to a nozzle for discharging the polishing composition.

[0084] The rinse polishing conditions are not particularly limited, and appropriate conditions can be appropriately set according to the characteristics of the surface treatment composition and the polished object. The rinse polishing load is not particularly limited, but generally, it is preferably 0.1 psi or more and 10 psi or less per unit area of ​​the substrate, more preferably 0.5 psi or more and 8 psi or less, and even more preferably 1 psi or more and 6 psi or less. Within this range, it is possible to obtain a high residue removal effect while further suppressing damage to the substrate due to the load and the occurrence of defects such as scratches on the surface. Note that 1 psi = 6.9 kPa. The rotation speed of the platen and the rotation speed of the carrier are not particularly limited, but generally, it is preferably 10 rpm or more and 500 rpm or less, more preferably 20 rpm or more and 300 rpm or less, and even more preferably 30 rpm or more and 200 rpm or less. The rotation speed of the platen and the rotation speed of the carrier may be the same or different, but it is preferable that the rotation speed of the platen is greater than the rotation speed of the carrier. Note that 1 rpm = 0.017 s -1 The method for supplying the surface treatment composition is not particularly limited, and a method for continuously supplying the composition with a pump or the like (flowing over) may be used.

[0085] The amount of the surface treatment composition to be supplied (flow rate of the surface treatment composition) is not particularly limited as long as the entire polished object is covered, but is generally preferably 100 mL / min to 5000 mL / min. The rinse polishing time is not particularly limited as long as the desired residue removal effect is obtained, but is generally preferably 5 seconds to 180 seconds.

[0086] The surface treatment method may be a method using a cleaning treatment. In this specification, the cleaning treatment refers to a treatment performed in a state where the polished object is removed from the polishing table (platen), and the residue on the surface of the polished object is removed mainly by the chemical action of the surface treatment composition. A specific example of the cleaning treatment is a treatment in which the polished object is removed from the polishing table (platen) after the final polishing (finish polishing) of the object to be polished, or after the final polishing followed by a rinse polishing treatment, and the polished object is brought into contact with the surface treatment composition. In the contact state between the surface treatment composition and the polished object to be polished, a means for applying a frictional force (physical action) to the surface of the polished object to be polished may be further used.

[0087] The cleaning method, cleaning device, and cleaning conditions are not particularly limited, and known methods, devices, conditions, etc. can be appropriately used. The cleaning method is not particularly limited, and examples thereof include a method of immersing a ground object in a surface treatment composition and performing ultrasonic treatment as necessary, and a method of contacting a cleaning brush with the ground object while holding the ground object, and scrubbing the surface of the ground object with the brush while supplying the surface treatment composition to the contact area.

[0088] <Intermediate water washing process, final water washing process> Washing with water may be performed before or after the surface treatment process according to the present invention, or both. In this specification, washing with water before the surface treatment process is also referred to as an "intermediate water washing process", and washing with water after the surface treatment process is also referred to as a "final water washing process". The washing method in the intermediate water washing process and the final water washing process is not particularly limited, but it is preferable to wash with water in a polishing device such as that used in the above-mentioned chemical mechanical polishing process and surface treatment process. The intermediate water washing process may be, for example, a method in which after performing the chemical mechanical polishing process in a polishing device, the polishing object is fixed to the polishing table (platen) and polished using the same pad while supplying water to wash the object. In addition, the polishing may be performed on a polishing table (platen) other than the chemical mechanical polishing process by using a different pad while supplying water to wash the object. The final polishing process may be performed, for example, in a brush washing section inside the polishing device. In this case, the brush may be pressed against the object to be polished and washed with water, or it may be washed without pressing the brush against the object to be polished. Thereafter, water droplets adhering to the surface of the polished object may be removed by a spin dryer or an air blower, and the object may be dried.

[0089] However, when the pH of the polishing composition used in the chemical mechanical polishing step is in the alkaline region (pH 8.0 or more and 12.0 or less), silicon (Si) contained in the object to be polished is dissolved in the polishing composition as silicate ions, as described above. When the pH of the silicate ions drops to 7.5 or less, they precipitate as silicate salts. As a result, the water-soluble polymer-silicate ion complex also precipitates as a salt. However, by performing the surface treatment step while maintaining a pH higher than 7.5, the water-soluble polymer-silicate ion complex is prevented from being precipitated, and the water-soluble polymer-silicate ion complex can be easily removed from the substrate surface in the form of a complex. As a result, the effect of reducing residues in the subsequent surface treatment step can be further improved. Thus, according to a preferred embodiment of the present invention, there is provided a method for producing a semiconductor substrate, in which the pH of the polishing composition is 8.0 or more and 12.0 or less, and there is no step of making the pH of the surface of the polished object to be 7.5 or less between the chemical mechanical polishing step and the surface treatment step. More specifically, it is preferable that a water washing step is not included between the chemical mechanical polishing step and the surface treatment step.

[0090] Furthermore, the present invention provides a semiconductor substrate obtained by the method for producing a semiconductor substrate. EXAMPLES

[0091] The present invention will be described in more detail with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. In addition, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0092] <Abrasive grain size> The average primary particle size of the abrasive grains was calculated from the specific surface area of ​​the abrasive grains measured by the BET method using a Micromeritics "Flow SorbII 2300" and the density of the abrasive grains. The average secondary particle size of the abrasive grains was measured using a Nikkiso Co., Ltd. dynamic light scattering particle size and particle size distribution analyzer UPA-UT151.

[0093] <pH of the polishing composition and the surface treatment composition> The pH of the polishing composition (liquid temperature: 25° C.) and the surface treatment composition (liquid temperature: 25° C.) were each measured using a pH meter (manufactured by Horiba, Ltd., model number: LAQUA (registered trademark)).

[0094] [Example 1] <<Preparation of Polishing Composition>> Colloidal silica (average primary particle size: 35 nm, average secondary particle size: 70 nm) as abrasive grains was added to pure water as a dispersion medium at room temperature (25° C.) to a final concentration of 0.5 mass % and polyvinylpyrrolidone (PVP) (weight average molecular weight (Mw): 8000) as a water-soluble polymer was added to 0.1 ppm to obtain a mixture. Then, potassium hydroxide (KOH) as a pH adjuster was added to the mixture to adjust the pH to 11, and the mixture was stirred and mixed at room temperature (25° C.) for 30 minutes to prepare a polishing composition.

[0095] Preparation of Surface Treatment Composition Additive 1, 29% by mass of ammonia water, was added to the pure water dispersion medium at room temperature (25°C) so that the final concentration was 300 ppm in terms of ammonia (NH3), and the mixture was stirred and mixed at room temperature (25°C) for 30 minutes to prepare a surface treatment composition.

[0096] 《Chemical mechanical polishing process》 The above polishing composition was used to polish the following object under the following polishing conditions using the following polishing apparatus.

[0097] (Polishing equipment and polishing conditions) Polishing equipment: Applied Materials 200mm CMP single-sided polishing equipment Mirra (registered trademark) Polishing pad: Nitta DuPont hard polyurethane pad IC1010 Grinding pressure: 2psi (1psi=6894.76Pa) Polishing platen rotation speed: 103 rpm Head (carrier) rotation speed: 97 rpm Supply of polishing composition: free-flowing Polishing composition supply amount: 200mL / min Polishing time: 30 seconds for the object (1) to be polished below. The object (2) to be polished below was polished until the entire surface of the silicon nitride film was exposed.

[0098] (Object to be polished) (1) A 5,000 Å thick polysilicon (Poly-Si) film is formed on the surface of a silicon wafer (200 mm, blanket wafer, manufactured by Advantec Corporation). (2) An 8-inch Poly-Si pattern was formed on the surface of a silicon wafer (200 mm, blanket wafer, manufactured by Advantec Corporation).

[0099] The Poly-Si pattern consists of the following three layers: The first layer is a plasma TEOS-SiO film with a thickness of 1000 Å formed on a silicon wafer. The second layer is a 500 Å thick SiN film with a Sematech 854 pattern formed on top of the first layer. The third layer is a Poly-Si film having a thickness of 2000 Å formed on the second layer.

[0100] Fig. 1 is a cross-sectional view that shows a schematic representation of the object to be polished of (3) above. As shown in Fig. 1, the object to be polished 10 has three layers, a TEOS-SiO film 2, a patterned SiN film 3, and a Poly-Si film 4, laminated on a silicon wafer 1. In Fig. 1, H1 indicates the line width, and H2 indicates the space width. Also in Fig. 1, T1 indicates the thickness of the SiN film 3, and T2 indicates the thickness of the TEOS-SiO film 2 (the height from the surface of the TEOS-SiO film 2 to the surface of the SiN film 3 on the line of the SiN film 3).

[0101] 《Intermediate washing process》 The polished object that had been subjected to the above chemical mechanical polishing process was cleaned for 60 seconds using a single wafer cleaning device AS-2000 manufactured by SCREEN Holdings Co., Ltd., while spraying deionized water (DIW) using a polyvinyl alcohol (PVA) brush. It was then dried for 30 seconds using a spin dryer. The pH of the polished surface of the polished object after cleaning was 7.5 or less.

[0102] Surface treatment process The polished object that had been subjected to the above water washing step was polished using the above surface treatment composition with the following surface treatment polishing apparatus under the following polishing conditions.

[0103] (Surface treatment equipment and surface treatment conditions) Polishing equipment: Applied Materials 200mm CMP single-sided polishing equipment Mirra Polishing pad: Nitta Haas IC1010 hard polyurethane pad Polishing pressure: 1.0 psi (1 psi = 6894.76 Pa) Polishing platen rotation speed: 73 rpm Head (carrier) rotation speed: 67 rpm Supply of surface treatment composition: free-flowing Surface treatment composition supply amount: 200mL / min Surface treatment time: 30 seconds.

[0104] 《Final washing process》 The surface-treated polishing object that had undergone the above surface treatment process was cleaned for 60 seconds using a polyvinyl alcohol (PVA) brush while spraying deionized water (DIW) on it in a single-wafer cleaning device AS-2000 manufactured by SCREEN Holdings Co., Ltd. Then, it was dried for 30 seconds in a spin dryer.

[0105] [Examples 2 to 16, Comparative Examples 1 to 5] Examples 2 to 16 and Comparative Examples 1 to 5 were carried out in the same manner as Example 1, except that the weight average molecular weight (Mw) and amount of PVP, the type of pH adjuster, the pH of the polishing composition, the presence or absence of an intermediate water washing step, the type and amount of additive 1, the type and amount of additive 2, and the pH of the surface treatment composition were changed as shown in Table 1 below. In Table 1 below, "-" indicates that the agent was not included. In Example 9, nitric acid (HNO3) was used as the pH adjuster, and a nitric acid aqueous solution with a concentration of 60 mass% was added to the pure water, which was the dispersion medium, so as to reach the final concentration in Table 1. In Example 7, ammonium acetate was used as the additive 1, and ammonium acetate with a concentration of 99 mass% was added to the pure water, which was the dispersion medium, so as to reach the final concentration in Table 1. Examples 4 and 6 are examples that do not include an intermediate water washing step, but the pH of the polished object surface between the chemical mechanical polishing step and the surface treatment step was more than pH 7.5.

[0106] <Evaluation> For each surface-treated object to be polished after the final water washing step, the number of Si-containing residues and the polishing state were evaluated by the following methods.

[0107] (Number of Si-containing residues) The number of residues of 0.05 μm or more was measured for each surface-treated object to be polished (1) above. The number of residues was measured using SP-2 manufactured by KLA TENCOR. The measurement was carried out on the remaining part of the surface-treated object to be polished, excluding a part 5 mm wide from the outer peripheral edge of one side of the object to be polished.

[0108] Next, the number of Si-containing residues was measured for each surface-treated object to be polished. The number of Si-containing residues was measured by SEM observation using Review SEM RS6000 manufactured by Hitachi High-Tech Corporation. First, 100 residues present in the remaining part excluding a part with a width of 5 mm from the outer peripheral end of one side of the surface-treated object to be polished were sampled by SEM observation. Then, from among the 100 sampled residues, Si-containing residues (precipitates of water-soluble polymer-silicic acid ion complex, water-soluble polymer-abrasive grain complex) were identified by SEM observation, and the proportion (%) of Si-containing residues in the residues was calculated by confirming the number of residues. The number of Si-containing residues (pieces) of 0.05 μm or more was calculated as the product of the above-mentioned number (pieces) of residues or more and the proportion (%) of Si-containing residues in the residues.

[0109] The Si-containing residue was determined based on the peaks derived from Si (silicon) and C (carbon) measured by an energy dispersive X-ray analyzer (EDX) attached to the Review SEM. Examples of the residues having these two peaks include precipitates of water-soluble polymer-silicic acid ion complexes and water-soluble polymer-abrasive composites. In detail, the Review SEM was used to photograph the areas where the above-mentioned two peaks were measured by EDX, and those without abrasive grains (those smaller than the size of the observed abrasive grains) were counted as precipitates of water-soluble polymer-silicic acid ion complexes, and those with abrasive grains (those larger than the size of the observed abrasive grains) were counted as water-soluble polymer-abrasive composites, and the total number of these was taken as the number of Si-containing residues.

[0110] (Polished condition) For each of the surface-treated polishing objects (2) above, the dishing amount (dishing depth) of the silicon nitride film and the polysilicon film was measured using an atomic force microscope (INSIGHT-CAP, manufactured by Bruker Japan Co., Ltd.) at the wiring width parts (H1 and H2 parts in FIG. 1) of 100 μm silicon nitride and 100 μm polysilicon, and judged according to the following criteria.

[0111] Judgment criteria (Judgment): (Amount of dishing) Good: Less than 400 Å Defective: 400Å or more.

[0112] The evaluation results are shown in Table 1 below.

[0113] [Table 1]

[0114] As is clear from Table 1, the methods of Examples 1 to 16 were found to be able to reduce the number of residues (number of Si-containing residues) while maintaining a good polishing state. Among them, the methods of Examples 4 and 6, which did not include a water washing step, were even more effective in reducing the number of residues. Moreover, Examples 5 to 7, which included a potassium compound (potassium hydroxide) as additive 2, were even more effective in reducing the number of residues.

[0115] On the other hand, the method of Comparative Example 1 is an example in which the content of the water-soluble polymer (polyvinylpyrrolidone) in the polishing composition is less than 0.1 ppm, but this method is not suitable for practical use because dishing occurs in the chemical mechanical polishing process. The method of Comparative Example 5 is an example in which the content of the water-soluble polymer (polyvinylpyrrolidone) in the polishing composition is more than 500 ppm, but this method cannot sufficiently reduce the number of residues.

[0116] The methods of Comparative Examples 2 and 3 are examples in which the content of ammonia (salt) (ammonia) in the surface treatment composition is less than 100 ppm, but the number of residues cannot be sufficiently reduced by these methods. The method of Comparative Example 4 is an example in which the content of ammonia (salt) (ammonia) in the surface treatment composition is more than 10,000 ppm, but this method is not suitable for practical use because dishing occurs due to etching of polysilicon in the surface treatment process.

Claims

1. A chemical mechanical polishing step of chemically and mechanically polishing an object to be polished using a polishing composition containing abrasive grains and a water-soluble polymer having a lactam structure; and A surface treatment step of surface-treating the polished object obtained in the chemical mechanical polishing step with a surface treatment composition containing at least one type of ammonia (salt), The content of the water-soluble polymer is 0.1 ppm or more and 500 ppm or less based on the total mass of the polishing composition, The content of the ammonia (salt) is 100 ppm or more and 10,000 ppm or less based on the total mass of the surface treatment composition, A method for producing a semiconductor substrate, wherein the pH of the surface treatment composition is 8.0 or more and 12.0 or less (excluding those in which the surface treatment composition contains at least one of a water-soluble polymer and an abrasive grain).

2. The method according to claim 1 , wherein the polishing composition has a pH of 2.0 or more and 12.0 or less.

3. The pH of the polishing composition is 8.0 or more and 12.0 or less, 3. The method according to claim 1, further comprising the step of adjusting the pH of the polished surface of the object to 7.5 or less between the chemical mechanical polishing step and the surface treatment step.

4. The surface treatment composition further comprises at least one potassium compound selected from the group consisting of potassium hydroxide and potassium salts; The method according to any one of claims 1 to 3, wherein the content of the potassium compound is 100 ppm or more and 10,000 ppm or less based on the total mass of the surface treatment composition.

5. The method according to any one of claims 1 to 4, wherein the object to be polished contains polysilicon.

6. A semiconductor substrate obtained by the method for producing a semiconductor substrate according to any one of claims 1 to 5.

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