JP7609585B2 - Polishing composition - Google Patents

Description

The present invention relates to a polishing composition.

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 its application to the gate formation process in transistor fabrication. When fabricating a transistor, Si-containing materials such as silicon, polycrystalline silicon (polysilicon), silicon oxide (silicon oxide), 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.

For example, Patent Document 1 discloses a polishing composition that contains a water-soluble polymer and at least one type of abrasive grain selected from colloidal silica and fumed silica, does not contain an oxidizing agent, and has a pH of 1 to 8. Such a polishing composition can polish polysilicon at a high polishing rate.

JP 2013-251561 A

Among the demands for controlling the polishing rate of each Si-containing material, there is also a demand to polish polysilicon at a high polishing rate while suppressing increases in the polishing rate for silicon oxide, silicon nitride, etc.

Therefore, the present invention aims to provide a polishing composition that can polish polysilicon at a high polishing rate and suppress an increase in the polishing rate for silicon oxide and silicon nitride.

The present inventors have conducted extensive research to solve the above problems. As a result, they have found that the above problems can be solved by a polishing composition that contains abrasive grains having a negative zeta potential and a peptide bond-containing compound having at least one peptide bond and a molecular weight of 100 or more and less than 2400, and has a pH of 6.0 or less.

The present invention provides a polishing composition that can polish polysilicon at a high polishing rate and suppresses an increase in the polishing rate for silicon oxide and silicon nitride.

The following describes one embodiment of the present invention. The present invention is not limited to the following embodiment.

In this specification, the range "X-Y" means "X or more and Y or less." In addition, unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20-25°C) and a relative humidity of 40-50% RH.

<Polishing Composition>
One aspect of the present invention is a polishing composition having a pH of 6.0 or less, comprising abrasive grains having a negative zeta potential and a peptide bond-containing compound having at least one peptide bond and a molecular weight of 100 or more and less than 2400. With this configuration, polysilicon can be polished at a high polishing rate, and an increase in the polishing rate for silicon oxide and silicon nitride can be suppressed.

The reason why the polishing composition of this embodiment exhibits the above-mentioned effects is not necessarily clear, but it is believed that the electrons on the nitrogen atoms in the peptide bonds of the peptide bond-containing compound nucleophilically attack the polysilicon and hydrophilize the polysilicon surface, thereby improving the polishing rate of the polysilicon. On the other hand, the peptide bond-containing compound functions as a protective film against silicon oxide and silicon nitride, and is therefore believed to be able to suppress an increase in the polishing rate of silicon oxide and silicon nitride. This mechanism is based on speculation, and the present invention is not limited to the above mechanism in any way.

[Abrasive grains having a negative zeta potential]
The polishing composition of the present embodiment contains abrasive grains having a negative zeta potential (also referred to simply as "abrasive grains according to the present invention" in this specification). Here, the "zeta potential" refers to the potential difference that occurs at the interface between a solid and a liquid that are in contact with each other when they undergo relative motion.

The zeta potential of the abrasive grains is, for example, from -80 mV to -5 mV, preferably from -70 mV to -10 mV, more preferably from -60 mV to -20 mV, and most preferably from -50 mV to -30 mV. The effects of the present invention can be achieved by the abrasive grains having a zeta potential in this range.

The zeta potential of the abrasive grains in the polishing composition is calculated by subjecting the polishing composition to an ELS-Z2 manufactured by Otsuka Electronics Co., Ltd., measuring it at a measurement temperature of 25°C using a flow cell by the laser Doppler method (electrophoretic light scattering measurement method), and analyzing the obtained data using the Smoluchowski formula.

In one embodiment, specific examples of the abrasive grains according to the present invention 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 particularly preferred. Therefore, in a preferred embodiment, the abrasive grains according to the present invention contain colloidal silica.

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 can be suitably used as the abrasive grains according to the present invention. Among these, colloidal silica produced by the sol-gel method, which can produce high-purity colloidal silica, is preferred.

The abrasive grains according to the present invention may have a surface modified to have a negative zeta potential at pH 6.0 or less. Such abrasive grains can be obtained by, for example, mixing a metal such as aluminum, titanium or zirconium or an oxide thereof with the abrasive grains and doping the surface of the abrasive grains, or by immobilizing an organic acid. Among them, abrasive grains having an organic acid immobilized on the surface are preferred. More preferred is silica having an organic acid chemically bonded to the surface. In such a form, a negative zeta potential can be obtained at pH 6.0 or less. The organic acid is not particularly limited, but examples include sulfonic acid, carboxylic acid, phosphoric acid, and the like, and is preferably sulfonic acid. In addition, silica having an organic acid immobilized on its surface has an acidic group derived from the organic acid (e.g., a sulfo group, a carboxyl group, a phosphoric acid group, etc.) immobilized on the surface of the silica by covalent bonding (in some cases via a linker structure). Here, the linker structure means any structure interposed between the surface of the silica and the organic acid. Therefore, in silica with an organic acid fixed to its surface, the acidic group derived from the organic acid may be fixed to the silica surface by a direct covalent bond, or may be fixed by a covalent bond via a linker structure. The method of introducing these organic acids to the silica surface is not particularly limited, and there is a method of introducing the organic acid to the silica surface in the form of a mercapto group or an alkyl group, etc., and then oxidizing it to a sulfonic acid or a carboxylic acid, as well as a method of introducing the organic acid to the silica surface in the form of a protecting group bonded to the organic acid group, and then removing the protecting group.

As a specific method for synthesizing silica with an organic acid fixed on its surface, if sulfonic acid, which is a type of organic acid, is fixed on the surface of silica, it can be performed, for example, by the method described in "Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups", Chem. Commun. 246-247 (2003). Specifically, silica with sulfonic acid fixed on its surface can be obtained by coupling a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, to silica and then oxidizing the thiol group with hydrogen peroxide. Colloidal silica modified with sulfonic acid on its surface in the examples of the present invention is also produced in the same manner.

To fix a carboxylic acid on the surface of silica, for example, the method described in "Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel", Chemistry Letters, 3, 228-229 (2000) can be used. Specifically, a silane coupling agent containing a photoreactive 2-nitrobenzyl ester is coupled to silica, and then the silica is irradiated with light to obtain silica with a carboxylic acid fixed on its surface.

The lower limit of the average primary particle size of the abrasive grains according to the present invention is preferably 1 nm or more, more preferably 5 nm or more, even more preferably 7 nm or more, and most preferably 10 nm or more. The upper limit of the average primary particle size of the abrasive grains according to the present invention is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 30 nm or less, and most preferably 20 nm or less. Within such a range, polysilicon can be polished at a high polishing rate. The average primary particle size of the abrasive grains is calculated, for example, based on the specific surface area of the abrasive grains measured by the BET method.

The lower limit of the average secondary particle diameter of the abrasive grains according to the present invention is preferably 2 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more. The upper limit of the average secondary particle diameter of the abrasive grains according to the present invention is preferably 200 nm or less, more preferably 150 nm or less, even more preferably 100 nm or less, and most preferably 50 nm or less. Within such a range, polysilicon can be polished at a high polishing rate. The average secondary particle diameter of the abrasive grains can be measured, for example, by a dynamic light scattering method, such as a laser diffraction scattering method.

The shape of the abrasive grains according to the present invention is not particularly limited, and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular prisms and square prisms, cylinders, bale shapes in which the center of a cylinder is more bulging than the ends, donut shapes with a disk penetrating the center, plates, cocoon shapes (shapes with a constriction in the center), associative sphere shapes (shapes in which multiple particles are integrated), confetti shapes (shapes with multiple protrusions on the surface), and rugby ball shapes.

The content (concentration) of the abrasive grains according to the present invention is, for example, 0.1% by mass or more and 25% by mass or less, preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass or less, and most preferably 2% by mass or more and 5% by mass or less, relative to the polishing composition. When the content is within such a range, the polishing rate for polysilicon can be further improved. When the polishing composition contains two or more types of abrasive grains, the content of the abrasive grains means the total amount of these.

[Peptide bond-containing compounds]
The polishing composition of this embodiment contains a peptide bond-containing compound having at least one peptide bond and a molecular weight of 100 or more and less than 2,400 (also referred to simply as a "peptide bond-containing compound" in this specification).

In this specification, the term "peptide bond" refers to an amide bond formed between two amino acid molecules by dehydration condensation between a carboxyl group of one molecule and an amino group of the other.

From the viewpoint of further improving the polishing speed of polysilicon, the molecular weight of the peptide bond-containing compound is preferably 110 or more and 1500 or less, more preferably 120 or more and 1000 or less, even more preferably 130 or more and 500 or less, even more preferably 150 or more and 500 or less, and most preferably 200 or more and 500 or less.

The molecular weight of a peptide bond-containing compound can be determined by known methods such as SDS-PAGE, amino acid analysis, and size exclusion chromatography.

In one embodiment, from the viewpoint of being able to more effectively exert the effects of the present invention, the peptide-containing compound is preferably a peptide containing 2 to 10 amino acids, more preferably selected from the group consisting of dipeptides, tripeptides, tetrapeptides, pentapeptides, hexapeptides, heptapeptides, and octapeptides, even more preferably selected from the group consisting of dipeptides, tripeptides, and tetrapeptides, and particularly preferably selected from tripeptides and tetrapeptides.

Examples of amino acid units that make up peptides include glycine, alanine, valine, leucine, isoleucine, serine, threonine, tyrosine, cysteine, methionine, asparagine, glutamine, aspartic acid, glutamic acid, lysine, arginine, histidine, proline, phenylalanine, tryptophan, and analogs thereof. Specific examples of analogs include 2-aminoadipic acid, 3-aminoadipic acid, β-alanine, 2-aminobutyric acid, 4-aminobutyric acid, 6-aminocaproic acid, 2-aminoheptanoic acid, 2-aminoisobutyric acid, 3-aminoisobutyric acid, 2-aminopimelic acid, 2,4-diaminobutyric acid, desmosine, 2,2'-diaminopimelic acid, 2,3-diaminopropionic acid, N-ethylglycine, 2-ethylasparagine, hydroxylysine, allo-hydroxylysine, 3-hydroxyproline, 4-hydroxyproline, isodesmosine, allo-isoleucine, N-methylglycine, N-methylisoleucine, 6-N-methyllysine, N-methylvaline, norvaline, norleucine, and ornithine.

Examples of peptides obtained from the above amino acid units include glycylglycine, alanylalanine, glycylalanine, alanylglycine, glutamylglutamic acid, glycylglycylglycine, alanylalanylalanine, glycylalanylserine, glycylphenylalanine, alanylcystinylglycine, glycylalanylvaline, glutamylcystinylglycine, leucylglycylglycine, aspartame, glycyl-DL-phenylalanine, DL-alanyl-DL-phenylalanine, N-L-α-aspartyl-L-phenylalanine-1-methyl, and carnosine.

In one embodiment, the peptide bond-containing compound preferably comprises a peptide selected from the group consisting of glycylglycine, alanylalanine, glycylalanine, alanylglycine, glycylglycylglycine, alanylalanylalanine, and combinations thereof, more preferably a peptide selected from the group consisting of glycylglycine, glycylglycylglycine, and tetraglycine.

The peptide bond-containing compound may be synthesized by conventional methods including chemical synthesis and recombinant technology using the above amino acids as raw materials, or a commercially available product may be used.

The content (concentration) of the peptide bond-containing compound is, for example, 0.01% by mass or more and 20% by mass or less, preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, even more preferably 0.2% by mass or more and 1% by mass or less, and most preferably 0.2% by mass or more and 0.5% by mass or less.

[Dispersion medium]
The polishing composition of this embodiment may contain a dispersion medium. As the dispersion medium, water is preferred. From the viewpoint of preventing the influence of impurities on other components of the polishing composition, it is preferred to use water with as high purity as possible. As such water, for example, water with a total content of transition metal ions of 100 ppb or less is preferred. Here, the purity of water can be increased by, for example, removing impurity ions using ion exchange resin, removing foreign matter with a filter, distillation, and other operations. Specifically, as water, for example, deionized water (ion-exchanged water), pure water, ultrapure water, distilled water, etc. are preferably used. Usually, 90% by volume or more of the dispersion medium contained in the polishing composition is preferably water, more preferably 95% by volume or more of water, even more preferably 99% by volume or more of water, and particularly preferably 100% by volume of water.

The dispersion medium may be a mixed solvent of water and an organic solvent to disperse or dissolve each component. In this case, examples of organic solvents that can be used include acetone, acetonitrile, ethanol, methanol, isopropanol, glycerin, ethylene glycol, and propylene glycol, which are organic solvents that are miscible with water. These organic solvents may be used without being mixed with water, and then the components may be dispersed or dissolved, and then mixed with water. These organic solvents may be used alone or in combination of two or more kinds.

[pH adjuster]
The polishing composition of this embodiment can contain a pH adjuster to adjust the pH to 6.0 or less.

The pH adjuster is not particularly limited as long as it is a compound that has a pH adjusting function, and known compounds can be used. The pH adjuster is not particularly limited as long as it has a pH adjusting function, and examples of the pH adjuster include acids and alkalis.

Either inorganic or organic acids may be used as the acid. Inorganic acids are not particularly limited, but examples thereof include sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Organic acids are not particularly limited, but examples thereof include 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, as well as methanesulfonic acid, ethanesulfonic acid, and isethionic acid. Among these, inorganic acids are preferred, and maleic acid is more preferred.

The alkali is not particularly limited, but examples include alkali metal hydroxides such as potassium hydroxide, ammonia, quaternary ammonium salts such as tetramethylammonium and tetraethylammonium, and amines such as ethylenediamine and piperazine.

The pH adjusters can be used alone or in combination of two or more.

The content of the pH adjuster is not particularly limited, and is preferably an amount that can adjust the pH value to a value within the preferred range described below.

[Other ingredients]
The polishing composition of the present invention may further contain known additives such as chelating agents, thickeners, oxidizing agents, dispersants, surface protective agents, wetting agents, surfactants, rust inhibitors, preservatives, and fungicides, within the range that does not impair the effects of the present invention. The content of the additives may be appropriately set depending on the purpose of their addition.

[pH of polishing composition]
The pH of the polishing composition of this embodiment is not particularly limited as long as it is 6.0 or less, and can be appropriately adjusted according to the combination of the abrasive grain and peptide bond-containing composition used.The lower limit of pH is, for example, 1.0 or more, preferably 2.0 or more, more preferably 2.5 or more.The upper limit of pH is preferably 5.5 or less, and may be 5.0 or less or 4.5 or less.

The pH value can be confirmed using a pH meter (manufactured by Horiba Ltd., model number: LAQUA (registered trademark)).

[Electrical Conductivity of Polishing Composition]
The upper limit of the electrical conductivity of the polishing composition of this embodiment is preferably 4.0 mS/cm or less, more preferably 2.0 mS/cm or less, from the viewpoint of further suppressing aggregation of abrasive grains. The lower limit of the electrical conductivity of the polishing composition of this embodiment is preferably 0.1 mS/cm or more, more preferably 0.5 mS/cm or more, from the viewpoint of solubility. The electrical conductivity can be confirmed by a tabletop electrical conductivity meter (manufactured by Horiba, Ltd., model number: DS-71).

As the electrical conductivity regulator, although there is no particular limitation, a salt compound can be used. Examples of salt compounds include acid salts and base salts, such as potassium nitrate, ammonium nitrate, potassium hydrogen carbonate, ammonium carbonate, ammonium hydrogen carbonate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium sulfate, potassium chloride, sodium chloride, potassium bromide, potassium iodide, ammonium citrate, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide, and among these, ammonium sulfate is preferred. The salt compounds may be used alone or in combination of two or more.

The content (concentration) of the electrical conductivity adjuster can be adjusted appropriately depending on the desired electrical conductivity.

[Polished object]
The object to be polished using the polishing composition of this embodiment is not particularly limited, and examples thereof include silicon oxide (SiO ₂ ), silicon nitride (SiN), silicon carbonitride (SiCN), polycrystalline silicon (polysilicon), non-crystalline silicon (amorphous silicon), metals, SiGe, and the like.

The object to be polished according to the present embodiment preferably contains polycrystalline silicon (polysilicon), more preferably contains polycrystalline silicon (polysilicon), silicon oxide (SiO ₂ ), and silicon nitride (SiN). Therefore, the polishing composition according to the present embodiment is preferably used for polishing an object to be polished that contains polysilicon, more preferably used for polishing an object to be polished that contains polysilicon, and more preferably used for polishing an object to be polished that contains polysilicon, silicon oxide, and silicon nitride.

Examples of films containing silicon oxide include TEOS (Tetraethyl Orthosilicate) type silicon oxide films (hereinafter simply referred to as "TEOS films") 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 metal-containing film include a tungsten (W) film, a titanium nitride (TiN) film, a ruthenium (Ru) film, a platinum (Pt) film, a gold (Au) film, a hafnium (Hf) film, a cobalt (Co) film, a nickel (Ni) film, a copper (Cu) film, an aluminum (Al) film, a tantalum (
Ta) film and the like.

<Method of producing polishing composition>
The method for producing the polishing composition of this embodiment is not particularly limited, and can be obtained, for example, by stirring and mixing the abrasive grains and the peptide bond-containing compound, and other components as necessary, in a dispersion medium. The pH adjuster can be appropriately used to adjust the pH of the polishing composition to 6.0 or less. Therefore, the present invention provides a method for producing a polishing composition, which comprises mixing the abrasive grains and the peptide bond-containing compound.

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.

<Polishing method and semiconductor substrate manufacturing method>
One aspect of the present invention is a polishing method including a step of polishing an object to be polished with the polishing composition.

Another aspect of the present invention is a method for manufacturing a semiconductor substrate using the above polishing method.

As a polishing device, a general polishing device can be used that is equipped with a holder for holding a substrate or the like having an object to be polished, a motor whose rotation speed can be changed, and a polishing platen onto 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 to allow the polishing liquid to 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 ). 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 according to one embodiment of the present invention.

After polishing is complete, the substrate is washed with running water, and the water droplets adhering to the substrate are removed using a spin dryer or the like, followed by drying to obtain a substrate having a metal-containing layer.

The polishing composition according to one embodiment of the present invention may be a one-component type or a multi-component type, such as a two-component type. The polishing composition according to one embodiment of the present invention may also be prepared by diluting the stock solution of the polishing composition, for example, 10 times or more, with a diluent such as water.

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. In the following examples, unless otherwise specified, the operations were carried out under the conditions of room temperature (20-25°C) and relative humidity of 40-50% RH.

[Preparation of Polishing Composition]
Example 1
As an abrasive grain, sulfonic acid-modified colloidal silica (average primary particle size 14 nm, average secondary particle size 33 nm) was added to ion-exchanged water at a final concentration of 3 mass % and as a peptide-containing compound, tetraglycine was added to 0.3 mass %. The mixture was then stirred and mixed at room temperature (25°C) for 30 minutes, and the pH was adjusted to 2.5 using maleic acid as a pH adjuster to prepare a polishing composition.

Example 2
A polishing composition was prepared in the same manner as in Example 1, except that tetraglycine was changed to glycylglycylglycine.

Example 3
A polishing composition was prepared in the same manner as in Example 1, except that tetraglycine was changed to glycylglycine.

Example 4
A polishing composition was prepared in the same manner as in Example 1, except that the sulfonic acid-modified colloidal silica was changed to unmodified colloidal silica (average primary particle diameter 15 nm, average secondary particle diameter 35 nm) and the pH was adjusted to 4.5.

Example 5
A polishing composition was prepared in the same manner as in Example 4, except that tetraglycine was changed to glycylglycylglycine.

Example 6
A polishing composition was prepared in the same manner as in Example 4, except that tetraglycine was changed to glycylglycine.

(Example 7)
A polishing composition was prepared in the same manner as in Example 6, except that the pH was adjusted to 5.5.

(Comparative Example 1)
A polishing composition was prepared in the same manner as in Example 4, except that tetraglycine was replaced with collagen peptide (weight average molecular weight 4000).

The polishing composition of Comparative Example 1 showed aggregation of abrasive grains.

(Comparative Example 2)
A polishing composition was prepared in the same manner as in Example 4, except that tetraglycine was changed to glycine.

(Comparative Example 3)
As an abrasive, sulfonic acid-modified colloidal silica (average primary particle size: 14 nm, average secondary particle size: 33 nm) was added to ion-exchanged water to a final concentration of 3 mass %. The mixture was then stirred and mixed at room temperature (25° C.) for 30 minutes, and the pH was adjusted to 2.5 using maleic acid as a pH adjuster to prepare a polishing composition.

(Comparative Example 4)
A polishing composition was prepared in the same manner as in Comparative Example 3, except that the pH was adjusted to 4.5.

(Comparative Example 5)
A polishing composition was prepared in the same manner as in Example 1, except that tetraglycine was changed to glycine.

(Comparative Example 6)
A polishing composition was prepared in the same manner as in Example 6, except that the pH was adjusted to 7.0.

The composition of the polishing composition prepared above is shown in Table 1.

[Zeta potential measurement]
The polishing compositions of Examples 1 to 7 and Comparative Examples 1 to 6 prepared above were subjected to measurement by the laser Doppler method (electrophoretic light scattering measurement method) using an ELS-Z2 manufactured by Otsuka Electronics Co., Ltd. and a flow cell at a measurement temperature of 25° C. The obtained data was analyzed by the Smoluchowski formula to calculate the zeta potential of the sulfonic acid-modified colloidal silica or unmodified colloidal silica contained in the polishing composition. The results are shown in Table 2.

[Measurement of pH of polishing composition]
The pH of the polishing composition (liquid temperature: 25° C.) was confirmed with a pH meter (manufactured by Horiba, Ltd., model number: LAQUA).

[Measurement of Electrical Conductivity of Polishing Composition]
The electrical conductivity of the polishing composition after preparation was measured using a tabletop electrical conductivity meter (manufactured by Horiba, Ltd., model number: DS-71). The results are shown in Table 2.

[Evaluation of Polishing Rate]
The object to be polished is
・200mm wafer (Poly-Si)
・200 mm wafer (SiN (silicon nitride film)),
・200 mm wafer (TEOS (silicon oxide film)),
Each wafer was polished using the polishing composition obtained above under the following polishing conditions, and the polishing rate was measured. Also, the selectivity was calculated.

Polishing conditions Polishing machine: CMP single-sided polishing machine for 200 mm wafers Polishing pad: Polyurethane pad (IC1010: manufactured by Rohm and Haas)
Pressure: 4.0 psi (approximately 27.6 kPa)
Platen (surface plate) rotation speed: 90 rpm
Head (carrier) rotation speed: 87 rpm
Flow rate of polishing composition: 200 ml/min
Polishing time: 1 minute.

Polishing Speed The polishing speed (polishing rate) was calculated according to the following formula.

The film thickness was measured using an optical interference type film thickness measuring device (Model: ASET, manufactured by KLA Tencor Corporation) and evaluated by dividing the difference by the polishing time. The results are shown in Table 2.

As shown in Table 2, the polishing compositions of the examples can polish polysilicon at a higher polishing rate and suppress the increase in the polishing rate for TEOS and SiN compared to the polishing compositions of the comparative examples.

Claims (8)

an abrasive having a negative zeta potential;
A peptide selected from the group consisting of dipeptides, tripeptides, tetrapeptides, pentapeptides, hexapeptides, heptapeptides and octapeptides, the peptide having a molecular weight of 100 or more and less than 2400;
The amino acid units constituting the peptides include glycine, alanine, valine, leucine, isoleucine, serine, threonine, tyrosine, cysteine, methionine, asparagine, glutamine, aspartic acid, glutamic acid, lysine, arginine, histidine, proline, phenylalanine, tryptophan, 2-aminoadipic acid, 3-aminoadipic acid, β-alanine, 2-aminobutyric acid, 4-aminobutyric acid, 6-aminocaproic acid, 2-aminoheptanoic acid, 2-aminoisobutyric acid, 3-aminoisopropylacid, 5-amino ... isobutyric acid, 2-aminopimelic acid, 2,4-diaminobutyric acid, desmosine, 2,2'-diaminopimelic acid, 2,3-diaminopropionic acid, N-ethylglycine, 2-ethylasparagine, hydroxylysine, allo-hydroxylysine, 3-hydroxyproline, 4-hydroxyproline, isodesmosine, allo-isoleucine, N-methylglycine, N-methylisoleucine, 6-N-methyllysine, N-methylvaline, norvaline, norleucine, and ornithine;
The pH is 6.0 or less ,
A polishing composition used for polishing an object to be polished that contains polysilicon . 2. The polishing composition according to claim 1, wherein the peptide is selected from the group consisting of glycylglycine, alanylalanine, glycylalanine, alanylglycine, glutamylglutamic acid, glycylglycylglycine, alanylalanylalanine, glycylalanylserine, glycylphenylalanine, alanylcystinylglycine, glycylalanylvaline, glutamylcystinylglycine, leucylglycylglycine, aspartame, glycyl-DL-phenylalanine, DL-alanyl-DL-phenylalanine, N-L-α-aspartyl-L-phenylalanine-1-methyl, and carnosine. 3. The polishing composition according to claim 1, wherein the peptide is selected from the group consisting of glycylglycine, alanylalanine, glycylalanine, alanylglycine, glycylglycylglycine, and alanylalanylalanine. The polishing composition according to any one of claims 1 to 3, wherein the abrasive grains contain colloidal silica. 5. The polishing composition according to claim 1, which is used for polishing an object containing polysilicon and silicon oxide and/or silicon nitride. The polishing composition according to claim 5 , which is used for polishing an object containing polysilicon, silicon oxide, or silicon nitride. A polishing method comprising a step of polishing an object containing polysilicon with the polishing composition according to any one of claims 1 to 4 . A method for producing a semiconductor substrate containing polysilicon , comprising the polishing method according to claim 7 .