JP7319190B2 - Polishing composition - Google Patents

Description

The present invention relates to polishing compositions. This application claims priority based on Japanese Patent Application No. 2017-191175 filed on September 29, 2017, the entire contents of which are incorporated herein by reference.

2. Description of the Related Art Conventionally, precision polishing using a polishing composition has been performed on the surfaces of materials such as metals, semi-metals, non-metals and their oxides. For example, the surface of a silicon substrate used as a component of semiconductor products is generally finished to a high-quality mirror surface through a lapping process (rough polishing process) and a polishing process (precise polishing process). The polishing process typically includes a preliminary polishing process (preliminary polishing process) and a final polishing process (final polishing process).

For the purpose of identification, the silicon substrate may be marked with barcodes, numbers, symbols (hard laser marks; hereinafter referred to as "HLM") by irradiating the surface of the silicon substrate with a laser beam. ) may be attached. Application of the HLM is generally performed after the lapping process of the silicon substrate and before starting the polishing process. In general, irradiation of a laser beam for attaching the HLM causes a bulge (swell) on the surface of the silicon substrate around the periphery of the HLM. Although the HLM portion of the silicon substrate itself is not used in the final product, the yield may unnecessarily decrease if the bumps are not properly removed in the polishing step after applying the HLM. However, since the protuberances are often hardened due to alteration such as polysiliconization due to the energy of the laser beam, conventional general polishing compositions for silicon wafers effectively eliminate the protuberances. was difficult to do.

Japanese Patent Application Publication No. 2015-233031 Japanese Patent Application Publication No. 2017-117917

Patent Documents 1 and 2 are cited as technical documents related to elimination of protuberances (hereinafter also simply referred to as “protuberances”) at the HLM periphery. However, there is still a desire to eliminate the bulge by a method different from the techniques disclosed in these documents or more effectively.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a polishing composition that is excellent in swelling elimination properties.

The present inventors have completed the present invention by discovering that the combination of tetramethylammonium hydroxide (TMAH) and other specific quaternary ammonium compounds can improve the swelling elimination property.

This specification provides a polishing composition comprising abrasive grains, a basic compound and water. The polishing composition contains a combination of two or more quaternary ammonium compounds as the basic compound. These quaternary ammonium compounds include tetramethylammonium hydroxide and one or more selected from compounds represented by the following general formula (1).

Here, ^X- in the formula is a monovalent anion, and R ¹ , R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrocarbon groups having 1 to 4 carbon atoms. . At least one of R ¹ , R ² , R ³ and R ⁴ is a hydrocarbon group having 2 to 4 carbon atoms.

Preferred examples of the compound represented by the general formula (1) (hereinafter also referred to as "compound (1)") include tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide. The use of tetraethylammonium hydroxide (TEAH) is particularly preferred because it is easy to achieve a good balance between a good swelling elimination property and a good polishing rate. The technology disclosed herein can be preferably implemented in a mode using a combination of TMAH and TEAH.

In some embodiments, the compound (1) accounts for 0% by weight of the total weight of tetramethylammonium hydroxide contained in the upper pre-polishing composition and the compound represented by the general formula (1). It is preferably used in the range of more than 85% by weight. According to such a configuration, it is easy to achieve a good balance between a good swelling resolving property and a good polishing rate.

Silica particles can be preferably used as the abrasive grains. The use of silica particles can prevent contamination of the silicon substrate due to abrasive grains.

In some aspects, the average primary particle size of the abrasive grains is preferably 20 nm or more and 150 nm or less. Abrasive grains having such an average primary particle diameter tend to achieve a good balance between the ability to eliminate bumps and the prevention of scratches.

The polishing composition disclosed herein may further contain a weak acid salt. By including the basic compound and the weak acid salt in combination, the bumps can be eliminated more effectively by utilizing the pH buffering action of the polishing composition.

The polishing composition disclosed herein can have excellent bulge elimination properties, that is, performance to eliminate bulges on the HLM periphery. Therefore, the polishing composition is suitable for polishing silicon substrates to which HLM has been applied.

Preferred embodiments of the present invention are described below. Matters other than those specifically mentioned in this specification, which are necessary for carrying out the present invention, can be grasped as design matters by those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field.

In this specification, the average primary particle size of the abrasive grains means that the average primary particle size (nm) = 6000/(true density (g/cm ³ ) x BET from the specific surface area (BET value) measured by the BET method. value (m ² /g)). For example, in the case of silica particles, the average primary particle size can be calculated by: average primary particle size (nm)=2727/BET value (m ² /g). The specific surface area can be measured, for example, using a surface area measuring device manufactured by Micromeritex, trade name "Flow Sorb II 2300".

In this specification, the aspect ratio of each particle that constitutes the abrasive grain is defined by the length of the short side of the smallest rectangular rectangle that circumscribes the image of the particle by a scanning electron microscope (SEM) and the length of the short side of the same rectangle. It can be obtained by dividing by The average aspect ratio and standard deviation of the aspect ratio of abrasive grains are the average value and standard deviation of the aspect ratio of multiple particles within the field of view of the scanning electron microscope, and these are obtained using general image analysis software. can be asked for.

In this specification, the circle-equivalent diameter of a particle refers to a value obtained by measuring the area of an image of the particle with a scanning electron microscope and determining the diameter of a circle having the same area. The average circle-equivalent diameter and standard deviation of the circle-equivalent diameter of the particles that make up the abrasive grains are the average value and standard deviation of the circle-equivalent diameter of multiple particles within the field of view of the scanning electron microscope, and these are also common can be obtained using a suitable image analysis software.

In this specification, the elimination of the HLM peripheral ridges means to reduce the height from the reference plane (reference plane) around the HLM on the surface of the object to be polished to the highest point of the ridges. The height from the reference plane to the highest point of the protrusion can be measured, for example, by the method described in Examples below.

<Abrasive>
The polishing composition disclosed herein contains abrasive grains. Abrasive grains serve to mechanically polish the surface of an object to be polished.

The material and properties of the abrasive grains are not particularly limited, and can be appropriately selected according to the purpose of use, mode of use, and the like. Abrasive grains may be used singly or in combination of two or more. Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of inorganic particles include silicon compound particles such as silica particles, silicon nitride particles and silicon carbide particles, and diamond particles. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles and polyacrylonitrile particles. Among them, inorganic particles are preferred.

Particularly preferred abrasive grains in the technology disclosed herein include silica particles. The technology disclosed herein can be preferably implemented, for example, in a mode in which the abrasive grains are substantially composed of silica particles. Here, "substantially" means that 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, and may be 100% by weight) of the particles constituting the abrasive grains It refers to silica particles.

Specific examples of silica particles include colloidal silica, fumed silica, precipitated silica, and the like. A silica particle can be used individually by 1 type or in combination of 2 or more types. Colloidal silica is particularly preferred because it is less likely to cause scratches on the surface of the object to be polished and can exhibit good polishing performance (performance to reduce surface roughness, ability to eliminate bumps, etc.). As the colloidal silica, for example, colloidal silica produced from water glass (sodium silicate) by an ion exchange method or colloidal silica by an alkoxide method can be preferably employed. Here, the alkoxide colloidal silica is colloidal silica produced by a hydrolytic condensation reaction of alkoxysilane. Colloidal silica can be used individually by 1 type or in combination of 2 or more types.

The true specific gravity of silica constituting the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and still more preferably 1.7 or more. The polishing rate tends to increase as the true specific gravity of silica increases. From this point of view, silica particles having a true specific gravity of 2.0 or more (for example, 2.1 or more) are particularly preferred. Although the upper limit of the true specific gravity of silica is not particularly limited, it is typically 2.3 or less, for example 2.2 or less. As the true specific gravity of silica, a value measured by a liquid replacement method using ethanol as a replacement liquid can be adopted.

The average primary particle size of the abrasive grains is not particularly limited, and can be appropriately selected, for example, from a range of approximately 10 nm to 200 nm. From the viewpoint of improving the ability to eliminate bumps, the average primary particle size is preferably 20 nm or more, more preferably 30 nm or more. In some embodiments, the average primary particle size can be, for example, greater than 40 nm, greater than 45 nm, greater than 50 nm. Also, from the viewpoint of preventing scratches, the average primary particle size is usually advantageously 150 nm or less, preferably 120 nm or less, and more preferably 100 nm or less. In some embodiments, the average primary particle size may be 75 nm or less, or 60 nm or less.

The shape (outer shape) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical particles include peanut-shaped, ie, peanut-shell-shaped, cocoon-shaped, confetti-shaped, and rugby ball-shaped.

The average aspect ratio of abrasive grains is not particularly limited. The average aspect ratio of the abrasive grains is theoretically 1.0 or more, and can be 1.05 or more and 1.1 or more. An increase in the average aspect ratio generally tends to improve the ability to eliminate bumps. Also, the average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, from the viewpoint of reducing scratches and improving the stability of polishing. In some aspects, the average aspect ratio of the abrasive grains can be, for example, 1.5 or less, 1.4 or less, or 1.3 or less.

In some embodiments, the abrasive grains may be those in which the volume ratio of grains having an equivalent circular diameter of 50 nm or more and an aspect ratio of 1.2 or more is 50% or more. The volume ratio can also be 60% or more. When the value of the volume ratio is 50% or more, or more specifically 60% or more, the abrasive grains may contain a relatively large amount of grains having a size and an aspect ratio that are particularly effective in eliminating bumps. For this reason, it is possible to further improve the ability to eliminate bumps due to the mechanical action of the abrasive grains.

In some aspects, the average circular equivalent diameter of the abrasive grains may be, for example, 25 nm or more, 40 nm or more, 55 nm or more, or 70 nm or more. Also, the average circular equivalent diameter of the abrasive grains may be, for example, 300 nm or less, 200 nm or less, 150 nm or less, or 100 nm or less. The polishing composition disclosed herein can be suitably practiced using abrasive grains having such an average circular diameter.

The content of abrasive grains is not particularly limited, and can be appropriately set according to the purpose. The content of abrasive grains relative to the total weight of the polishing composition may be, for example, 0.01% by weight or more, 0.05% by weight or more, or 0.1% by weight or more. An increase in the content of abrasive grains generally tends to improve the ability to eliminate bumps. In some embodiments, the abrasive content may be 0.2 wt% or greater, 0.3 wt% or greater, 0.5 wt% or greater, or 0.7 wt% or greater. In addition, from the viewpoint of scratch prevention and saving of the amount of abrasive grains used, in some embodiments, the content of abrasive grains may be, for example, 10% by weight or less, 5% by weight or less, or 3% by weight or less. Well, it may be 2% by weight or less. These contents can be preferably applied to the contents in the polishing liquid (working slurry) supplied to the object to be polished, for example.

<Basic compound>
The polishing composition disclosed herein contains a combination of two or more quaternary ammonium compounds as the basic compound. The two or more quaternary ammonium compounds are tetramethylammonium hydroxide (TMAH) and at least one selected from compounds represented by the following general formula (1) (i.e., compound (1)), including.

Here, X 1 ⁻ in the above general formula (1) is a monovalent anion. R ¹ , R ² , R ³ and R ⁴ in the general formula (1) are each independently selected from the group consisting of hydrocarbon groups having 1 to 4 carbon atoms. At least one of R ¹ , R ² , R ³ and R ⁴ is a hydrocarbon group having 2 to 4 carbon atoms.

By including TMAH and compound (1) in combination, the swelling dissolving property can be significantly improved compared to, for example, the case of using TMAH alone. Although not wishing to be bound by theory, the reason why such an effect is obtained is considered as follows, for example. That is, a hydrocarbon group having 2 to 4 carbon atoms exhibits higher hydrophobicity than a methyl group, which is a hydrocarbon group having 1 carbon atom. Therefore, the cationic moiety of compound (1), in which at least one of R ¹ , R ² , R ³ and R ⁴ is a hydrocarbon group having 2 to 4 carbon atoms, is more hydrophobic than the cationic moiety of TMAH. It can be said that it shows sexuality. Therefore, the cationic portion of compound (1) tends to have higher adsorption to hydrophobic surfaces such as silicon substrates than the cationic portion of TMAH. By using a combination of TMAH and compound (1), a relatively high portion of the surface of the object to be polished is efficiently polished by the mechanical action of abrasive grains and the chemical action of TMAH, while a relatively low It is believed that as a result of the appropriate protection of the portion by the adsorption of compound (1), the swelling resolvability is improved. However, the interpretation is not limited to this.

The hydrocarbon group having 2 to 4 carbon atoms may be an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, or the like. From the viewpoint of chemical stability, alkyl groups having 2 to 4 carbon atoms are preferred. Alkyl groups of 2 to 4 carbon atoms may be selected from the group consisting of ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl groups. Among these, ethyl group, n-propyl group and n-butyl group are more preferred. R ¹ , R ² , R ³ and R ⁴ in the above formula (1) may be the same group or different groups. Compound (1), in which R ¹ , R ² , R ³ and R ⁴ are the same group, can be preferably employed because of easy availability of high-purity materials.

X ^- in the above formula is a monovalent anion. Examples of X ⁻ include OH ⁻ , F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , BH ₄ ⁻ and the like. Among them, compound (1) in which X ^{1 -} is OH ^- is preferred.

Examples of preferred compounds (1) include tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide and tetrabutylammonium hydroxide. Tetrapropylammonium hydroxide is preferably tetra-n-propylammonium hydroxide, and tetrabutylammonium hydroxide is preferably tetra-n-butylammonium hydroxide. Among them, preferred compound (1) includes TEAH and tetra-n-butylammonium hydroxide.

Polishing compositions according to some preferred embodiments contain two or more quaternary ammonium compounds, including at least TMAH and TEAH. In this way, by using a combination of quaternary ammonium compounds having similar structures but different hydrophobicities, it is possible to accurately adjust the improvement in the ability to eliminate bumps and the maintenance of the polishing rate. The polishing composition may be a composition containing TEAH and another quaternary ammonium compound as compound (1), or may be a composition containing TEAH alone. In the polishing composition disclosed herein, for example, more than 50% by weight, more than 75% by weight, more than 90% by weight, or more than 95% by weight of compound (1) contained in the composition is TEAH. It can be preferably implemented in a mode.

In the polishing composition disclosed herein, the weight ratio of the content W _M of TMAH and the content W1 of compound ( ₁ ) can favorably balance the improvement of swelling elimination properties and the maintenance of the polishing rate. It can be set as follows, and is not particularly limited. Here, the content _W1 of compound (1) refers to the total content of compounds (1) in a polishing composition containing two or more compounds (1). The ratio of the content of compound (1) to the total content of TMAH and compound (1), that is, W ₁ /(W _M +W ₁ ), can be a value greater than 0 wt % and less than 100 wt %.

In some embodiments, W ₁ /(W _M +W ₁ ) can be, for example, 1 wt% or greater, 2 wt% or greater, 5 wt% or greater, 7 wt% or greater, 10 wt% or greater. % or more, 20% by weight or more, or 30% by weight or more. An increase in W ₁ /(W _M +W ₁ ) tends to improve the swelling resolvability. In addition, from the viewpoint of facilitating a suitable balance between the swelling elimination property and the polishing rate, in some embodiments, W ₁ /(W _M +W ₁ ) may be, for example, 98% by weight or less, and 90% by weight or less. , 85% by weight or less, or 80% by weight or less.

In some other embodiments, W ₁ /(W _M +W ₁ ) is the value after polishing using a polishing composition having a composition in which the entire amount of compound (1) is replaced with the same weight of TMAH. ₀ and the polishing rate R ₀ at that time are each converted to 100%. The polishing rate H _C can be set to, for example, 90% or less, preferably 70% or less, more preferably 50% or less, and the polishing rate R _C at that time can be set to, for example, 85% or more. Although it _is not particularly limited, W ₁ /( _{W M} +W ₁ ) can be grasped.

The total content of TMAH and compound (1) is not particularly limited, and can be appropriately set depending on the purpose. From the viewpoint of improving the polishing rate, in some embodiments, the total content may be, for example, 0.001% by weight or more, or 0.005% by weight or more, relative to the total weight of the polishing composition. , 0.01% by weight or more, 0.05% by weight or more, or 0.1% by weight or more. Further, from the viewpoint of facilitating obtaining higher swelling dissolving properties, in some embodiments, the total content may be, for example, 5% by weight or less, 2% by weight or less, or 1% by weight or less, It may be 0.7% by weight or less, or 0.5% by weight or less. These contents can be preferably applied to the contents in the polishing liquid (working slurry) supplied to the object to be polished, for example.

The polishing composition disclosed herein may optionally contain a basic compound other than TMAH and compound (1) as long as the effects of the present invention are not significantly hindered. Examples of basic compounds as such optional components include quaternary ammonium compounds other than TMAH and compound (1), alkali metal hydroxides, quaternary phosphonium hydroxides, amines, ammonia, and the like. When a basic compound is included as an optional component, its content is suitably 1/2 or less, preferably 1/4 or less, of the total content of TMAH and compound (1) on a weight basis. more preferably 1/10 or less, 1/20 or less, 1/50 or less, or even 1/100 or less. From the viewpoint of composition simplification and performance stability, the polishing composition disclosed herein does not substantially contain a base (in particular, strong bases such as potassium hydroxide and piperazine) as an optional component. It can be preferably implemented. Here, "substantially free from" means not to be contained in the polishing composition at least intentionally. For example, a polishing composition that does not substantially contain potassium hydroxide is preferred.

<Weak acid salt>
The polishing composition disclosed herein may optionally contain a weak acid salt. As the weak acid salt (typically a weak base), one that can exert a desired buffering action in combination with a quaternary ammonium compound can be appropriately selected. A polishing composition configured to exert such a buffering action can have less pH fluctuation during polishing and can be excellent in maintaining polishing efficiency. As a result, it is possible to more preferably achieve both improvement in the ability to eliminate bumps and maintenance of the polishing rate.

Specific examples of weak acid salts include sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium orthosilicate, potassium orthosilicate, sodium acetate, potassium acetate, sodium propionate, potassium propionate, calcium carbonate, calcium hydrogen carbonate. , calcium acetate, calcium propionate, magnesium acetate, magnesium propionate, zinc propionate, manganese acetate, cobalt acetate and the like. Weak acid salts in which the anion component is carbonate ion or hydrogen carbonate ion are preferred, and weak acid salts in which the anion component is carbonate ion are particularly preferred. As the cation component, alkali metal ions such as potassium and sodium are suitable. A weak acid salt can be used individually by 1 type or in combination of 2 or more types.

From the viewpoint of obtaining a polishing composition that exhibits a good buffering action in a pH range suitable for polishing silicon substrates, at least one acid dissociation constant (pKa) value should be 8.0 to 11.8 (e.g., 8.0 to 11.8). 11.5) are preferred. Suitable examples include carbonates, hydrogen carbonates, borates, phosphates and phenol salts. Particularly preferred weak acid salts include sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate. Among them, potassium carbonate (K ₂ CO ₃ ) is preferred. As the pKa value, the value of the acid dissociation constant at 25° C. described in publicly known documents can be used.

The content of the weak acid salt can be set so that the buffering action is preferably exhibited in relation to the quaternary ammonium compound. Although not particularly limited, in some embodiments, the content of the weak acid salt may be, for example, 0.001% by weight or more, and 0.005% by weight or more, based on the total weight of the polishing composition. 0.01% by weight or more, 0.05% by weight or more, or 0.1% by weight or more. Further, from the viewpoint of facilitating obtaining higher swelling dissolving properties, in some embodiments, the total content may be, for example, 5% by weight or less, 2% by weight or less, or 1% by weight or less, It may be 0.7% by weight or less, or 0.5% by weight or less. These contents can be preferably applied to the contents in the polishing liquid (working slurry) supplied to the object to be polished, for example.

<Water>
In the polishing composition disclosed herein, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water and the like can be preferably used as water. The water used preferably has a total transition metal ion content of, for example, 100 ppb or less, in order to avoid as much as possible inhibition of the functions of other components contained in the polishing composition. For example, the purity of water can be increased by removing impurity ions using an ion exchange resin, removing foreign substances using a filter, and performing operations such as distillation.

<Other ingredients>
The polishing composition disclosed herein contains chelating agents, acids, water-soluble polymers, surfactants, preservatives, antifungal agents, etc., as long as the effects of the present invention are not significantly hindered. Known additives that can be used in (typically, a polishing composition used in a polishing step of a silicon substrate) may be further contained as necessary.

Examples of the chelating agents include aminocarboxylic acid-based chelating agents and organic phosphonic acid-based chelating agents. Examples of aminocarboxylic acid-based chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid. , sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid and sodium triethylenetetraminehexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid , ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid and α-methylphosphonic acid. Contains nosuccinic acid. Among these, organic phosphonic acid-based chelating agents are more preferred. Preferred among these are ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid) and diethylenetriaminepentaacetic acid. Particularly preferred chelating agents include ethylenediaminetetrakis(methylenephosphonic acid) and diethylenetriaminepenta(methylenephosphonic acid). A chelating agent can be used individually by 1 type or in combination of 2 or more types. The amount of the chelating agent used is such that the content of the chelating agent in the working slurry is about 0.0001 to 1% by weight, about 0.001 to 0.5% by weight, or about 0.005 to 0.1% by weight. However, it is not limited to this.

Examples of the above acids include inorganic acids such as hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, boric acid; acetic acid, itaconic acid, succinic acid, tartaric acid, citric acid, maleic acid, glycolic acid, malonic acid , organic acids such as methanesulfonic acid, formic acid, malic acid, gluconic acid, alanine, glycine, lactic acid, hydroxyethylidene diphosphonic acid (HEDP), nitrilotris [methylene phosphonic acid] (NTMP), phosphonobutane tricarboxylic acid (PBTC); mentioned. Acids may be used in the form of their salts. The salt of the acid may be, for example, an alkali metal salt such as sodium salt or potassium salt, or an ammonium salt.

Examples of the water-soluble polymer include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, polymers containing nitrogen atoms, and vinyl alcohol-based polymers. Specific examples include hydroxyethyl cellulose, pullulan, random copolymers and block copolymers of ethylene oxide and propylene oxide, polyvinyl alcohol, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallylsulfonic acid, and polyisoamylene sulfonic acid. , polystyrene sulfonate, polyacrylate, polyvinyl acetate, polyethylene glycol, polyvinylimidazole, polyvinylcarbazole, polyvinylpyrrolidone, polyvinylcaprolactam, polyvinylpiperidine and the like. A water-soluble polymer can be used individually by 1 type or in combination of 2 or more types. The polishing composition disclosed herein can also preferably be practiced in a mode in which it does not substantially contain a water-soluble polymer, that is, in a mode in which it does not contain a water-soluble polymer at least intentionally.

Examples of the antiseptic and antifungal agents include isothiazoline compounds, paraoxybenzoic acid esters, phenoxyethanol, and the like.

The polishing composition disclosed herein is preferably substantially free of oxidizing agents. If the polishing composition contains an oxidizing agent, the supply of the composition oxidizes the surface of the silicon substrate to form an oxide film, which may reduce the polishing rate. It's for. Here, the phrase "the polishing composition substantially does not contain an oxidizing agent" means that the polishing composition does not contain an oxidizing agent at least intentionally. is acceptable. The above-mentioned trace amount means that the molar concentration of the oxidizing agent in the polishing composition is 0.0005 mol/L or less (preferably 0.0001 mol/L or less, more preferably 0.00001 mol/L or less, and particularly preferably 0.0001 mol/L or less). 000001 mol/L or less). A preferred embodiment of the polishing composition does not contain an oxidizing agent. The polishing composition disclosed herein can be preferably carried out in a mode containing none of hydrogen peroxide, sodium persulfate, ammonium persulfate and sodium dichloroisocyanurate, for example.

<Polishing composition>
The polishing composition disclosed herein is typically supplied to an object to be polished in the form of a polishing liquid (working slurry) containing the polishing composition and used for polishing the object to be polished. The polishing composition may be used as a polishing liquid after being diluted with a solvent such as water, or may be used as a polishing liquid as it is. That is, the concept of the polishing composition in the technology disclosed herein includes both a working slurry supplied to an object to be polished and used for polishing the object, and a concentrated solution (undiluted solution) of the working slurry. is included. The concentration ratio of the concentrated solution may be, for example, about 2 to 50 times by volume, usually about 5 to 30 times is appropriate, and about 5 to 20 times is preferable.

The pH of the polishing composition is typically 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher, still more preferably 9.5 or higher, for example 10.0 or higher. A higher pH tends to improve the polishing rate and the ability to eliminate bumps. On the other hand, from the viewpoint of preventing dissolution of abrasive grains (for example, silica particles) and suppressing deterioration of the mechanical polishing action due to the abrasive grains, the pH of the polishing composition is usually 12.0 or less. is preferably 11.8 or less, more preferably 11.5 or less, and even more preferably 11.0 or less. These pH values can be preferably applied to both the pH of the polishing liquid (working slurry) supplied to the object to be polished and the pH of its concentrated liquid.

The pH of the polishing composition is measured using a pH meter (for example, a glass electrode type hydrogen ion concentration indicator (model number F-23) manufactured by Horiba Ltd.) and a standard buffer solution (phthalate pH buffer solution pH: 4.01 (25°C), neutral phosphate pH buffer pH: 6.86 (25°C), carbonate pH buffer pH: 10.01 (25°C)) after three-point calibration can be grasped by placing the glass electrode in the polishing liquid composition and measuring the value after 2 minutes or more have passed and the value is stabilized.

The polishing composition disclosed herein may be a one-component type or a multi-component type including a two-component type. For example, the polishing liquid may be prepared by mixing part A containing at least abrasive grains and part B containing the remaining components, and diluting at appropriate timing as necessary.

The method for producing the polishing composition disclosed herein is not particularly limited. For example, each component contained in the polishing composition may be mixed using a well-known mixing device such as a blade stirrer, an ultrasonic disperser, or a homomixer. The manner in which these components are mixed is not particularly limited. For example, all the components may be mixed at once, or they may be mixed in an appropriately set order.

<Grinding>
The polishing composition disclosed herein can be used for polishing an object to be polished, for example, in a mode including the following operations.
That is, a working slurry containing any one of the polishing compositions disclosed herein is prepared. Then, the polishing composition is supplied to the object to be polished, and the object is polished by a conventional method. For example, an object to be polished is set in a general polishing apparatus, and the polishing composition is supplied to the surface of the object to be polished (surface to be polished) through the polishing pad of the polishing apparatus. Typically, while the polishing composition is continuously supplied, the polishing pad is pressed against the surface of the object to be polished, and the two are relatively moved (for example, rotationally moved). Polishing of the object to be polished is completed through such a polishing process.

The polishing pad used in the polishing step is not particularly limited. For example, any of polyurethane foam type, non-woven fabric type, suede type, containing abrasive grains, and containing no abrasive grains may be used. As the polishing apparatus, a double-side polishing apparatus that polishes both surfaces of the object to be polished may be used, or a single-side polishing apparatus that polishes only one side of the object may be used.

The above-mentioned polishing composition may be used in such a manner that once it is used for polishing, it is disposed of (so-called "spray"), or it may be circulated and used repeatedly. As an example of the method of recycling the polishing composition, there is a method of recovering the used polishing composition discharged from the polishing apparatus in a tank and supplying the recovered polishing composition to the polishing apparatus again. .

<Application>
The polishing composition disclosed herein is excellent in the ability to eliminate bumps on the HLM periphery (bump elimination ability). Taking advantage of these features, the polishing composition can be preferably applied to polishing an object to be polished with HLM. For example, it is suitable as a polishing composition used in a preliminary polishing step for silicon substrates with HLMs. It is desirable to eliminate the bulging of the HLM periphery at the beginning of the polishing process. Therefore, the polishing composition disclosed herein can be particularly preferably used in the first polishing step (primary polishing step) after HLM application. Prior to the polishing step using the polishing composition disclosed herein, the silicon substrate is subjected to general treatments applicable to silicon substrates, such as lapping, etching, and application of the HLM described above. good too.
The silicon substrate typically has a surface made of silicon. Such a silicon substrate is typically a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot. The polishing composition disclosed herein is suitable for use in polishing HLM-attached silicon single crystal wafers.
The polishing composition disclosed herein can also be suitably used for polishing an object to be polished that does not have an HLM, and can efficiently reduce the surface roughness of the surface of the object to be polished.

Several examples relating to the present invention are described below, but the present invention is not intended to be limited to those shown in such examples.

<Preparation of polishing composition>
(Examples 1 to 4)
colloidal silica as an abrasive grain, potassium carbonate, tetramethylammonium hydroxide (TMAH) and tetraethylammonium hydroxide (TEAH) as basic compounds, ethylenediaminetetrakis(methylenephosphonic acid) (EDTPO) as a chelating agent, A polishing composition containing TMAH and TEAH at the concentration ratio shown in Table 1 was prepared by stirring and mixing with ion-exchanged water at room temperature of about 25° C. for about 30 minutes. The colloidal silica has an average primary particle size of 55 nm, an average circular diameter by SEM observation of 92.5 nm, a standard deviation of the circular diameter of 38.5, and an average aspect ratio of 1.29. , the standard deviation of the aspect ratio is 0.320, the volume ratio of particles having a circle conversion diameter of 50 nm or more and an aspect ratio of 1.2 or more is 77%, and the volume content of particles having a circle conversion diameter of 1 to 300 nm was 100%.

By diluting the polishing composition according to each example 10 times with deionized water, 1.0% by weight of colloidal silica, 0.2% by weight of potassium carbonate, and 0.2% by weight of TMAH and TEAH in total. %, and EDTPO at a concentration of 0.01% by weight.

(Comparative example 1)
A polishing composition was prepared in the same manner as in Example 1 except that TMAH was used alone as the basic compound, diluted 10 times with deionized water, and added with 1.0% by weight of colloidal silica and carbonate. A polishing liquid containing 0.2% by weight of potassium, 0.2% by weight of TMAH, and 0.01% by weight of EDTPO was prepared.

(Comparative example 2)
A polishing composition was prepared in the same manner as in Example 1 except that TEAH was used alone as the basic compound, diluted 10 times with deionized water, and added with 1.0% by weight of colloidal silica and carbonate. A polishing liquid containing 0.2% by weight of potassium, 0.2% by weight of TEAH, and 0.01% by weight of EDTPO was prepared.

Each of these polishing liquids constitutes a buffer system of K ₂ CO ₃ and TMAH and/or TEAH. The pH of these polishing liquids was 10.6-10.7.

<Performance evaluation>
(polishing)
Using the polishing liquid according to each example as it is as a working slurry, the surface of an object to be polished (specimen) was polished under the following conditions. As a test piece, a commercially available silicon single crystal wafer with a diameter of 100 mm after lapping and etching (thickness: 525 μm, conductivity type: P type, crystal orientation: <100>, resistivity: 0.1 Ω cm or more, 100 Ω cm less than) was used. An HLM is attached to the wafer.

[Polishing conditions]
Polishing device: Single-sided polishing device manufactured by Nippon Engis Co., Ltd., model "EJ-380"
Polishing pressure: 12kPa
Surface plate rotation speed: 50 rpm
Head rotation speed: 40rpm
Polishing pad: manufactured by Nitta Haas, trade name "SUBA800"
Polishing liquid supply rate: 100 mL/min (using continuous flow)
Holding temperature of polishing environment: 25°C
Polishing allowance: 4 μm

(Evaluation of swelling resolvability)
For the silicon wafer after polishing, the surface shape of the site including the HLM was measured using a stylus type surface roughness shape measuring machine (SURFCOM 1500DX, manufactured by Tokyo Seimitsu Co., Ltd.), and the maximum protrusion from the reference surface around the HLM was measured. Measure the height to the point. The evaluation result indicates that the larger the protrusion height, the poorer the protrusion resolvability. The results obtained are shown in Table 1, column "height of protrusion".

(polishing rate)
The polishing rate [nm/min] in each example and comparative example was calculated based on the time required for the polishing, that is, the time required for the polishing removal to reach 4 μm. The obtained result was converted into a relative value (relative polishing rate) with the polishing rate of Comparative Example 1 as 100%, and the polishing rate was evaluated according to the following two levels based on the value. Table 1 shows the results. The evaluation result "G" means that a polishing rate substantially equal to or higher than that of Comparative Example 1 using TMAH alone was obtained.
G: relative polishing rate is 85% or more NG: relative polishing rate is less than 85%

As shown in Table 1, according to Examples 1 to 4 in which TMAH and TEAH were used in combination, the height of bumps was lower than that of Comparative Example 1 while maintaining the polishing rate. was able to improve On the other hand, in Comparative Example 2 in which TEAH was used alone, the polishing rate decreased significantly.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Claims (8)

A polishing composition used for polishing a surface made of silicon of a silicon substrate to which a hard laser mark is imparted ,
containing abrasive grains, a basic compound and water,
The basic compound comprises a combination of two or more quaternary ammonium compounds,
The two or more quaternary ammonium compounds are tetramethylammonium hydroxide and the following general formula (1):

(where ^X- in the formula is a monovalent anion, and R ¹ , R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrocarbon groups having 1 to 4 carbon atoms. provided that at least one of R ¹ , R ² , R ³ and R ⁴ is a hydrocarbon group having 2 to 4 carbon atoms);
and one or more selected from compounds represented by (excluding tetrapropylammonium hydroxide). 2. The polishing composition according to claim 1, wherein the compound represented by formula (1) contains at least one selected from tetraethylammonium hydroxide and tetrabutylammonium hydroxide. The polishing composition according to claim 1, comprising tetraethylammonium hydroxide as the compound represented by formula (1). The compound represented by the general formula (1) exceeds 0% by weight of the total weight of tetramethylammonium hydroxide contained in the polishing composition and the compound represented by the general formula (1). The polishing composition according to any one of claims 1 to 3, which is used in an amount of 85% by weight or less. The polishing composition according to any one of claims 1 to 4, wherein the abrasive grains are silica particles. The polishing composition according to any one of claims 1 to 5, wherein the abrasive grains have an average primary particle size of 20 nm or more and 150 nm or less. The polishing composition according to any one of claims 1 to 6, further comprising a weak acid salt. The polishing composition according to any one of claims 1 to 7, further comprising a chelating agent.