JP7609683B2 - Semiconductor substrate manufacturing method and semiconductor substrate obtained by said manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor substrate and a semiconductor substrate obtained by the method.

In recent years, new microfabrication technologies have been developed in response to the increasing integration and performance of LSI (Large Scale Integration). Chemical mechanical polishing (CMP) is one such technology, and it is frequently used in the LSI manufacturing process, particularly in the multilayer wiring formation process, for planarizing the interlayer insulating film, forming metal plugs, and forming embedded wiring (damascene wiring).

CMP has been applied to various processes in semiconductor manufacturing, and one example of this 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.

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. 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.

JP 2007-103515 A

However, according to the study by the present inventors, 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.

Therefore, the object of the present invention is to provide a means for reducing residues on the substrate surface in a method for manufacturing a semiconductor substrate using a polishing composition containing a water-soluble polymer having a lactam structure.

In order to solve the above problems, the inventors have conducted extensive research. As a result, they have found that the above problems can be solved by chemically and 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.

That is, the method for manufacturing a semiconductor substrate according to one embodiment of the present invention includes a chemical mechanical polishing step of chemically 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 type 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 present invention, in a method for manufacturing a semiconductor substrate using a polishing composition containing a specific amount or more of a water-soluble polymer having a lactam structure, it is possible to reduce residues on the substrate surface.

FIG. 1 is a cross-sectional view that illustrates a polishing object (a silicon wafer having a Poly-Si patterned wafer formed on its surface) used in evaluation of the polishing state (dishing).

The present invention relates to a method for manufacturing a semiconductor substrate, which includes 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 type 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 manufacturing method of the present invention having such a configuration, it is possible to reduce residues on the surface of the substrate. In addition, it is possible to maintain the polished state of the substrate in a good condition.

The mechanism by which the above-mentioned effects are obtained is believed to be as follows. However, the following mechanism is merely speculation and does not limit the scope of the present invention.

According to the inventors' investigations, it is believed that the following two types of residues are generated in the semiconductor substrate manufacturing method of the present invention.

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

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

The ammonia (salt) contained in the surface treatment composition according to the present invention can exist as ammonium ions (NH ₄ ⁺ ) and ammonia in the surface treatment composition. 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. It is believed that this effect causes the precipitate of the water-soluble polymer-silicate ion complex and the water-soluble polymer-abrasive grain complex to be peeled off from the surface of the polished object, thereby reducing the residue.

The following describes an embodiment of the present invention. Note that the present invention is not limited to the following embodiment.

Unless otherwise specified in this specification, operations and measurements of physical properties are performed at room temperature (20°C or higher and 25°C or lower) and at a relative humidity of 40% RH or higher and 50% RH or lower.

In addition, in this specification, "(meth)acrylic" refers collectively to acrylic and methacrylic. Similarly, "(meth)acrylate" refers collectively to acrylate and methacrylate.

<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.

[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. Examples of materials that constitute a semiconductor substrate include polysilicon (polycrystalline silicon), single crystal silicon, silicon nitride, silicon carbonitride (SiCN), silicon oxide, materials containing silicon (Si) such as SiGe, and metals.

Examples of polishing objects containing silicon oxide include TEOS-type silicon oxide surfaces (hereinafter simply referred to as "TEOS") produced using tetraethyl orthosilicate as a precursor, HDP (High Density Plasma) films, USG (Undoped Silicate Glass) films, PSG (Phosphorus Silicate Glass) films, BPSG (Boron-Phospho Silicate Glass) films, and RTO (Rapid Thermal Oxidation) films.

Examples of the above metals include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium.

In particular, the object to be polished preferably contains at least one material containing silicon (Si), and more preferably contains polysilicon. As described above, materials containing silicon (Si) (particularly polysilicon) form a water-soluble polymer-silicate ion complex, and precipitates of this complex tend to remain as residues on the surface of the polished object after polishing. Therefore, the problem of the present invention is more likely to occur in objects to be polished that contain materials containing silicon (Si) (particularly polysilicon). In other words, the present invention is particularly suitable when the object to be polished contains materials containing silicon (Si) (particularly polysilicon). Therefore, according to a preferred embodiment of the present invention, the object to be polished contains polysilicon.

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

(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.

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 types. 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).

Colloidal silica can be produced by a method such as the sodium silicate method or the sol-gel method. Regardless of the method used, colloidal silica produced by this method can be suitably used as the abrasive grains in this embodiment. Among these, colloidal silica produced by the sol-gel method, which can produce high-purity colloidal silica, is preferred.

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 with 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 the value measured by the method described in the Examples.

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. 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 frequency of contact 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 measured by the method described in the Examples.

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 keeping costs down, 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.

(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 embrittles the Si-Si bond, facilitating polishing of the polysilicon. As a result, steps and dishing in the polysilicon film can be suppressed.

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 with 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.

(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: 1 mL/min Measurement temperature: 40°C
Molecular weight conversion: polyethylene glycol conversion Sample injection volume: 200 μL.

In cases where it is not possible to measure by GPC, the molecular weight calculated from the molecular formula is used as the weight average molecular weight.

The water-soluble polymer may contain structural units derived from N-vinyl lactam monomers in a proportion 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., a homopolymer of N-vinyl lactam monomers).

Examples of N-vinyl lactam type monomers include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinyl-2-caprolactam, N-vinyl-2-piperidone, N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholinedione. Among these, N-vinyl-2-pyrrolidone is preferred, taking into consideration the balance between protecting the surface of the object to be polished and improving the polishing speed.

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

The N-vinyl lactam monomer may contain structural units derived from other copolymerizable monomers that are copolymerizable with the monomer, as necessary.

Other copolymerizable monomers include, for example, 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, N-n-butyl (meth)acrylamide, N-sec-butyl (meth)acrylamide, and N-tert-butyl (meth)acrylamide; N,N-dialkyl (meth)acrylamides such as N,N-dimethyl (meth)acrylamide, 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-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide. N-hydroxyalkyl (meth)acrylamides such as N-vinyl carboxylic acid amides such as N-vinyl acetamide; 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; acrylic acid, methacrylic acid, carboxyethyl acrylate, Carboxy group-containing monomers such as 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-butyl cyclohexyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, Examples of (meth)acrylate monomers containing an alkoxy group or an oxyalkylene group include methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)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 trimethylammonium chloride, and dimethyl allyl vinyl ketone.

These other copolymerizable monomers can be used alone or in combination of two or more.

Specific preferred examples of water-soluble polymers 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 protecting the surface of the object to be polished and improving the polishing speed, poly(N-vinylpyrrolidone) (PVP) and poly(1-vinylpyrrolidone-co-vinyl acetate) are more preferred, and poly(N-vinylpyrrolidone) (PVP) is even more preferred.

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 100,000 or less, more preferably more than 1000 and less than 100,000, even more preferably 1500 or more and 90,000 or less, even more preferably more than 1500 and less than 90,000, even more preferably 5000 or more and 80,000 or less, particularly preferably more than 5000 and less than 80,000, and most preferably more than 5000 and 55,000 or less. A water-soluble polymer having a weight average molecular weight in the above range has excellent solubility and a good balance between protecting the surface of the object to be polished and improving the polishing speed.

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

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 speed will be 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 precipitates 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.

(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 preferred 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.

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

(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.

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 (H ₂ O ₂ ), 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 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).

(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.

The polishing composition of the present invention may be adjusted in pH by adding a pH adjuster within a range that does not impair the effects of the present invention.

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.

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.

Specific examples of bases used as pH adjusters include hydroxides or salts of Group 1 elements, hydroxides or salts of Group 2 elements, quaternary ammonium hydroxide or its salts, etc. Specific examples of salts include carbonates, hydrogen carbonates, sulfates, acetates, etc.

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

(Method for producing polishing composition)
The method for producing the polishing composition according to the present invention is not particularly limited, and the polishing composition 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.

The temperature at which the components are mixed is not particularly limited, but is preferably 10°C or higher and 40°C or lower, and may be heated to increase the dissolution rate. In addition, there is no particular limit to the mixing time as long as the components can be mixed uniformly.

(Chemical Mechanical Polishing)
As a polishing apparatus used 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 to which a polishing pad (polishing cloth) can be attached.

As the polishing pad, general nonwoven fabric, polyurethane, porous fluororesin, etc. can be used without any particular restrictions. It is preferable that the polishing pad has grooves so that the polishing composition can accumulate.

Regarding the polishing conditions, for example, the rotation speed of the polishing platen is preferably 10 rpm (0.17 s ^-1 ) or more and 500 rpm (8.3 s ^-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. There are no particular limitations on the method of supplying the polishing composition to the polishing pad, and for example, a method of continuously supplying the composition using a pump or the like is adopted. There is no limitation on 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.

<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).

[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 required.

(Ammonia (salt))
In this specification, "ammonia (salt)" is meant to collectively refer to ammonia (NH ₃ ) and its salts (ammonium salts). As described above, ammonia (salt) exists as ammonium ion (NH ₄ ⁺ ) and ammonia in the surface treatment composition, and has the effect of facilitating peeling off of water-soluble polymers having lactam structures. It is presumed that this effect makes it possible to peel off 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.

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 these, ammonium acetate is preferred.

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

In the surface treatment composition according to the present invention, the content (concentration) of ammonia (salt) is 100 ppm or more and 10,000 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 exerted. On the other hand, if the content of ammonia (salt) exceeds 10,000 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 8,000 ppm or less, more preferably 300 ppm or more and 3,000 ppm or less. In addition, when the surface treatment composition contains two or more types of ammonia (salt), the content of ammonia (salt) refers to the total amount of these.

(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 facilitating the peeling off of 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 the 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.

The potassium salt is not particularly limited, and inorganic salts of potassium and organic salts of potassium can be appropriately selected. 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.

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

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

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 refers to the total amount of these.

(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.

(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.

(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 amount of ammonium ion (NH ₄ ⁺ ) present in the surface treatment composition increases. As a result, the effect of reducing residues can be improved. When 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 measured by the method described in the examples below.

In the surface treatment composition of the present invention, ammonia (salt) and potassium compounds also function as pH adjusters. If 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 equivalent to ammonia (salt) and potassium compounds are not treated as pH adjusters in the surface treatment composition.

(Method for producing 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 (for example, water). The details of each component are as described above.

The temperature at which the components are mixed is not particularly limited, but is preferably 10°C or higher and 40°C or lower, and may be heated to increase the dissolution rate. In addition, there is no particular limit to the mixing time as long as the components can be mixed uniformly.

(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.

According to a preferred embodiment of the present invention, the surface treatment is preferably a rinse polishing treatment. The reason for this is that, although the details are unclear, the residue removal effect of the above-mentioned surface treatment composition is more pronounced in the rinse polishing treatment.

In this specification, rinse polishing refers to a process carried out on a polishing table (platen) to which a polishing pad is attached, in which residues on the surface of a polished object are removed by the frictional force (physical action) of the polishing pad and the action of a surface treatment composition. A specific example of a rinse polishing process is a process in which, after final polishing (finish polishing) of 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 slid relative to each other while the surface treatment composition is supplied to the contact area.

Therefore, according to a preferred embodiment of the present invention, a method for manufacturing a semiconductor substrate is provided 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 and the polishing pad relative to each other while supplying a surface treatment composition to the contact area.

The rinse polishing process is preferably carried out using a general polishing device, which is equipped with a holder for holding the object to be polished and a motor capable of changing the rotation speed, and has a polishing platen to which a polishing pad (polishing cloth) can be attached, although there is no particular restriction. Either a single-sided polishing device or a double-sided polishing device may be used as the polishing device. As the polishing pad, general nonwoven fabric, polyurethane, porous fluororesin, etc. can be used without any particular restriction. The polishing pad is preferably grooved so that the surface treatment composition can accumulate. In addition, when chemical mechanical polishing and the rinse polishing process 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.

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. In this range, it is possible to obtain a high residue removal effect while further suppressing the substrate from being damaged by 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. Here, 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 employed.

The amount of the surface treatment composition supplied (flow rate of the surface treatment composition) is not particularly limited as long as it covers the entire polished object, but is generally preferably 100 mL/min or more and 5000 mL/min or less. The rinse polishing process time is not particularly limited as long as it is appropriately set so as to obtain the desired residue removal effect, but is generally preferably 5 seconds or more and 180 seconds or less.

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 mainly removes residues on the surface of the polished object 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. A means for applying a frictional force (physical action) to the surface of the polished object to be polished while the surface treatment composition is in contact with the polished object to be polished may be further used.

The cleaning method, cleaning device, and cleaning conditions are not particularly limited, and known methods, devices, conditions, etc. can be used as appropriate. The cleaning method is not particularly limited, but examples include a method in which the ground object is immersed in a surface treatment composition and ultrasonic treatment is performed as necessary, and a method in which a cleaning brush is brought into contact with the ground object while holding the ground object, and the surface of the ground object is rubbed with the brush while supplying the surface treatment composition to the contact area.

<Intermediate water washing process, final water washing process>
Washing with water may be performed before or after the surface treatment step according to the present invention, or both. In this specification, washing with water before the surface treatment step is also referred to as an "intermediate water washing step", and washing with water after the surface treatment step is also referred to as an "intermediate water washing step". The washing with water after the step is also called the "final washing step". The washing method in the intermediate washing step and the final washing step is not particularly limited, but it is possible to use a washing method in a polishing device such as that used in the above-mentioned chemical mechanical polishing step or surface treatment step. The intermediate water washing step is preferably performed, for example, after the chemical mechanical polishing step is performed in a polishing apparatus, by washing the workpiece with water using the same pad while the workpiece is fixed on the polishing table (platen). A method of washing the surface by polishing the surface while supplying water is also available. In addition, a method of washing the surface by polishing the surface while supplying water using a separate pad on a separate polishing platen from the chemical mechanical polishing process is also available. The final polishing step may be performed, for example, in a brush cleaning section inside the polishing apparatus. In this case, the brush may be pressed against the object to be polished and then washed with water, or the brush may be pressed against the object to be polished and then washed with water. It is acceptable to rinse with water without 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.

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 above-mentioned 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 can be prevented from precipitating, and can be easily removed from the substrate surface in the form of a water-soluble polymer-silicate ion 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, a method for manufacturing a semiconductor substrate is provided in which the pH of the polishing composition is 8.0 or more and 12.0 or less, and there is no step between the chemical mechanical polishing step and the surface treatment step in which the liquidity of the surface of the polished object to be polished is pH 7.5 or less. More specifically, it is preferable not to include a water washing step between the chemical mechanical polishing step and the surface treatment step.

The present invention further provides a semiconductor substrate obtained by the semiconductor substrate manufacturing method.

The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

<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 dynamic light scattering particle size/particle size distribution device UPA-UT151 manufactured by Nikkiso Co., Ltd.

<pH of polishing composition and 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)).

[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 at 0.5 mass % and polyvinylpyrrolidone (PVP) (weight average molecular weight (Mw): 8000) as a water-soluble polymer was added at a final concentration of 0.1 ppm to pure water as a dispersion medium at room temperature (25°C) to obtain a mixed solution. Potassium hydroxide (KOH) was then added as a pH adjuster to the mixed solution so that the pH was 11, and the mixture was stirred and mixed at room temperature (25°C) for 30 minutes to prepare a polishing composition.

Preparation of Surface Treatment Composition
Additive 1 was prepared by adding 29% by mass of ammonia water to pure water, which was a dispersion medium, at room temperature (25°C) so as to give a final concentration of 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.

《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.

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

(Object to be polished)
(1) A silicon wafer (200 mm, blanket wafer, manufactured by Advantec Co., Ltd.) on whose surface a polysilicon (Poly-Si) film having a thickness of 5000 Å was formed.
(2) A silicon wafer (200 mm, blanket wafer, manufactured by Advantec Co., Ltd.) on whose surface an 8-inch Poly-Si pattern is formed.

The Poly-Si pattern is composed of the following three layers.
The first layer is a plasma TEOS-SiO film having 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.

Figure 1 is a cross-sectional view showing a schematic representation of the object to be polished in (3) above. As shown in Figure 1, the object to be polished 10 has three layers stacked on top of a silicon wafer 1: a TEOS-SiO film 2, a patterned SiN film 3, and a Poly-Si film 4. In Figure 1, H1 indicates the line width, and H2 indicates the space width. Also in Figure 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).

<Intermediate water washing process>
The polished object that had been subjected to the above chemical mechanical polishing process was washed 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 washing was 7.5 or less.

<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.

(Surface treatment device and surface treatment conditions)
Polishing equipment: Applied Materials 200mm CMP single-sided polishing equipment Mirra
Polishing pad: Nitta Haas Co., Ltd. Hard polyurethane pad IC1010
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: continuous flow Supply amount of surface treatment composition: 200 mL/min Surface treatment time: 30 seconds.

<Final washing process>
The surface-treated polishing object that had undergone the above surface treatment 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, and then dried for 30 seconds with a spin dryer.

[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 a 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 (HNO ₃ ) was used as the pH adjuster, and a nitric acid aqueous solution with a concentration of 60% by 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% by 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 a water washing step, but the pH of the polished surface of the object to be polished between the chemical mechanical polishing step and the surface treatment step was more than 7.5.

<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.

(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 Corporation. The measurement was carried out on the remaining part of one side of the surface-treated object to be polished, excluding a part with a width of 5 mm from the outer peripheral edge.

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 area excluding a 5 mm wide area from the outer peripheral edge of one side of the surface-treated object to be polished were sampled by SEM observation. Then, from among the 100 residues sampled, Si-containing residues (water-soluble polymer-silicic acid ion complex precipitates, water-soluble polymer-abrasive grain complexes) 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) was calculated as the product of the number of residues of 0.05 μm or more and the proportion (%) of Si-containing residues in the residues.

Whether or not the residue is Si-containing was determined based on the peaks derived from Si (silicon) and C (carbon) measured by the energy dispersive X-ray analyzer (EDX) attached to the Review SEM. Examples of substances that have these two types of peaks include precipitates of water-soluble polymer-silicic acid ion complexes and water-soluble polymer-abrasive grain complexes. In detail, photographs were observed with the Review SEM at the locations where the above two types of 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 grain complexes, and the total number of these was taken as the number of Si-containing residues.

(Polished condition)
For each of the surface-treated polishing objects (2), 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 portion (H1 and H2 portions in FIG. 1) of 100 μm silicon nitride and 100 μm polysilicon, and judged according to the following criteria.

Judgment criteria (judgment): (amount of dishing)
Good: less than 400 Å. Bad: 400 Å or more.

The evaluation results are shown in Table 1 below.

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 condition. 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. Furthermore, Examples 5 to 7, which included a potassium compound (potassium hydroxide) as additive 2, were even more effective in reducing the number of residues.

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 exceeds 500 ppm, but this method does not sufficiently reduce the number of residues.

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 these methods do not sufficiently reduce the number of residues. The method of Comparative Example 4 is an example in which the content of ammonia (salt) (ammonia) in the surface treatment composition exceeds 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 (6)

The method includes 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 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) . The manufacturing method according to claim 1, wherein the pH of the polishing composition is 2.0 or more and 12.0 or less. 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. 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. The manufacturing method according to any one of claims 1 to 4, wherein the object to be polished includes polysilicon. A semiconductor substrate obtained by the method for manufacturing a semiconductor substrate according to any one of claims 1 to 5.