WO2019065357A1

WO2019065357A1 - Polishing composition

Info

Publication number: WO2019065357A1
Application number: PCT/JP2018/034401
Authority: WO
Inventors: 恵谷口; 貴俊向井; 公亮土屋
Original assignee: 株式会社フジミインコーポレーテッド
Priority date: 2017-09-29
Filing date: 2018-09-18
Publication date: 2019-04-04
Also published as: JP7319190B2; TW201920587A; JPWO2019065357A1

Abstract

Provided is a polishing composition having excellent capability for removing protrusions at the hard laser mark periphery. This polishing composition contains abrasive grains, a basic compound, and water. The basic compound includes a combination of two or more types of quaternary ammonium compounds. The two or more types of quaternary ammonium compounds include tetramethyl ammonium hydroxide and one or more types selected from compounds represented by general formula (1). (In the formula, X- is a monovalent anion and R1, R2, R3, and R4 are each independently selected from the group consisting of C1-4 hydrocarbon groups. However, at least one of R1, R2, R3 and R4 is a C2-4 hydrocarbon group.)

Description

Polishing composition

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

Heretofore, precision polishing using a polishing composition has been performed on the surface of materials such as metals, metalloids, nonmetals and oxides thereof. For example, the surface of a silicon substrate used as a component of a semiconductor product or the like is generally finished into a high quality mirror surface through a lapping step (rough polishing step) and a polishing step (precision polishing step). The polishing step typically includes a pre-polishing step (pre-polishing step) and a final polishing step (final-polishing step).

A mark such as a bar code, a numeral or a symbol (hard laser mark; hereinafter referred to as “HLM”) may be written on a silicon substrate by irradiating a laser beam on the surface of the silicon substrate for the purpose of identification and the like. May be attached. The application of the HLM is generally performed after finishing the lapping process of the silicon substrate but before starting the polishing process. Usually, the irradiation of the laser beam for applying the HLM causes a bump (swell) on the silicon substrate surface at the periphery of the HLM. Although the HLM portion of the silicon substrate itself is not used for the final product, the yield may be lowered more than necessary if the above-mentioned bumps are not properly eliminated in the polishing step after the HLM application. However, since the above-mentioned raised portion is often hardened due to deterioration such as conversion to polysilicon due to the energy of laser light, the polishing composition for conventional general silicon wafer is effectively eliminated the above-mentioned raised portion. It was difficult to do.

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

Patent documents 1 and 2 are mentioned as technical literature related to eliminating a ridge (hereinafter, also simply referred to as a "ridge") at the periphery of HLM. However, there is still a desire to eliminate the above-mentioned bumps by means different from the techniques disclosed in these documents or more effectively.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a polishing composition having an excellent ability to eliminate bumps.

The present inventors have completed the present invention by finding that the bump removability can be improved by using tetramethylammonium hydroxide (TMAH) in combination with other specific quaternary ammonium compounds.

According to this specification, a polishing composition comprising an abrasive, a basic compound, and water is provided. The polishing composition contains, as the basic compound, a combination of two or more types of quaternary ammonium compounds. Those quaternary ammonium compounds include tetramethylammonium hydroxide and one or more selected from the compounds represented by the following general formula (1).

Here, in the formula, X ^- 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 . However, 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 above 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 both good bump elimination and a good polishing rate in a well-balanced manner. The technology disclosed herein can be preferably implemented in a mode in which TMAH and TEAH are used in combination.

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 preferable to use in the range of more than 85 weight%. According to such a configuration, it is easy to achieve both good rise elimination and good polishing rate in a well-balanced manner.

As the above-mentioned abrasive, silica particles can be preferably used. The use of silica particles can prevent the contamination of the silicon substrate due to the abrasive grains.

In some embodiments, the average primary particle size of the abrasive grains is preferably 20 nm or more and 150 nm or less. According to the abrasive grain having such an average primary particle diameter, it is easy to achieve both the bump elimination property and the prevention of the occurrence of scratches in a well-balanced manner.

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

The polishing composition disclosed herein can be excellent in the ability to eliminate bumps, that is, the ability to eliminate the bumps on the periphery of the HLM. Therefore, the polishing composition is suitable for use in polishing a silicon substrate to which HLM has been applied.

Hereinafter, preferred embodiments of the present invention will be described. The matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be understood as the design matters of 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 the present specification and common technical knowledge in the field.

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

In this specification, the aspect ratio of each particle constituting the abrasive grain is the same as the length of the long side of the smallest rectangle circumscribing the image of the particles by scanning electron microscopy (SEM). It can be determined by dividing by. The average aspect ratio of the abrasive grains and the standard deviation of the aspect ratio are the average value and standard deviation of the aspect ratios of a plurality of particles within the field of view of the scanning electron microscope, and these are obtained using general image analysis software. Can be asked.

In this specification, the circle-converted diameter of a particle means a value obtained by measuring the area of the image of the particle by a scanning electron microscope and determining the diameter of a circle having the same area. The average circle-converted diameter and the standard deviation of the circle-converted diameter of the particles constituting the abrasive grains are the average value and the standard deviation of the circle-converted diameters of a plurality of particles within the field of view of the scanning electron microscope. Image analysis software.

In this specification, to eliminate the bumps on the periphery of the HLM 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 bumps. The height from the reference surface to the highest point of the ridge can be measured, for example, by the method described in the examples described later.

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

The material and properties of the abrasive 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 alone or in combination of two or more. Examples of the abrasive include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include silicon particles such as silica particles, silicon nitride particles and silicon carbide particles, and diamond particles. Specific examples of the organic particles include poly (methyl methacrylate) (PMMA) particles, polyacrylonitrile particles and the like. Among them, inorganic particles are preferable.

Particularly preferred abrasives in the art disclosed herein include silica particles. The technique disclosed herein can be preferably practiced, for example, in a mode in which the abrasive grains substantially consist 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 says that it is a silica particle.

Specific examples of the silica particles include colloidal silica, fumed silica, precipitated silica and the like. The silica particles can be used alone or in combination of two or more. Colloidal silica is particularly preferable because it is less likely to cause scratches on the surface of the object to be polished and can exhibit good polishing performance (such as the ability to reduce surface roughness and the ability to eliminate bumps). As the colloidal silica, for example, colloidal silica prepared using water glass (Na silicate) as a raw material by an ion exchange method, or alkoxide method colloidal silica can be preferably employed. Here, the alkoxide method colloidal silica is colloidal silica produced by the hydrolysis condensation reaction of an alkoxysilane. Colloidal silica can be used singly or in combination of two or more.

The true specific gravity of the 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 be high due to the increase of the true specific gravity of silica. From this viewpoint, silica particles having a true specific gravity of 2.0 or more (for example, 2.1 or more) are particularly preferable. The upper limit of the true specific gravity of silica is not particularly limited, but 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 displacement method using ethanol as a displacement liquid can be adopted.

The average primary particle diameter of the abrasive grains is not particularly limited, and can be appropriately selected, for example, from the range of about 10 nm to about 200 nm. The average primary particle diameter is preferably 20 nm or more, and more preferably 30 nm or more, from the viewpoint of improving the protrusion removability. In some embodiments, the average primary particle size may be, for example, greater than 40 nm, greater than 45 nm, or greater than 50 nm. Also, from the viewpoint of preventing the occurrence of scratches, the average primary particle diameter 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 may be spherical or non-spherical. Specific examples of non-spherical particles include peanut-like shapes, such as peanut-like shell shapes, wedge-like shapes, and projections with a shape such as a bell-and-loop sugar shape, and rugby ball shapes.

The average aspect ratio of the abrasive is not particularly limited. The average aspect ratio of the abrasive grains is, in principle, 1.0 or more, and can be 1.05 or more and 1.1 or more. With the increase of the average aspect ratio, the relief property tends to be generally improved. The average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, from the viewpoints of scratch reduction, polishing stability improvement and the like. In some embodiments, the average aspect ratio of the abrasive may be, for example, 1.5 or less, 1.4 or less, or 1.3 or less.

In some embodiments, as the abrasive, one having a volume ratio of particles having a circle-converted diameter of 50 nm or more and an aspect ratio of 1.2 or more of 50% or more can be employed. The volume ratio can be 60% or more. When the value of the volume ratio is 50% or more, and more specifically 60% or more, relatively large particles having a size and aspect ratio effective for eliminating bumps can be contained in the abrasive grains. 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 embodiments, the average circle-converted diameter of the abrasive may be, for example, 25 nm or more, 40 nm or more, 55 nm or more, or 70 nm or more. The average circle-converted 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 carried out using an abrasive having such an average circle-converted diameter.

The content of the abrasive is not particularly limited, and may be appropriately set according to the purpose. The content of the 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. By increasing the content of abrasive grains, the tendency to eliminate bumps tends to be generally improved. In some embodiments, the abrasive content may be 0.2 wt% or more, 0.3 wt% or more, 0.5 wt% or more, or 0.7 wt% or more. In addition, from the viewpoint of scratch prevention and saving of the usage amount of abrasive grains, in some embodiments, the content of abrasive grains may be, for example, 10% by weight or less, may be 5% by weight or less, or 3% by weight or less It may be 2% by weight or less. These contents can be preferably applied, for example, to the contents in the polishing liquid (working slurry) supplied to the object to be polished.

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

Here, X in the general formula (1) ^- is a monovalent anion. R ¹ , R ² , R ³ and R ⁴ in the above general formula (1) are each independently selected from the group consisting of hydrocarbon groups having 1 to 4 carbon atoms. However, 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 the compound (1) in combination, for example, as compared with the case where TMAH is used alone, the ridge removability can be significantly improved. Although not wishing to be bound by theory, the reason why such an effect is obtained is considered, for example, as follows. That is, the hydrocarbon group having 2 to 4 carbon atoms exhibits higher hydrophobicity than the methyl group which is a hydrocarbon group having 1 carbon atom. Therefore, the cation moiety of the 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 has higher hydrophobicity than that of TMAH. It can be said that it shows sex. For this reason, the cation moiety of the compound (1) tends to be more adsorptive to a hydrophobic surface such as a silicon substrate or the like than the cation moiety of TMAH. By using TMAH and the compound (1) in combination, a relatively high portion of the surface of the object to be polished is efficiently polished by the mechanical action of the abrasive grains or the chemical action of TMAH, but it is relatively low. As a result of the portion being appropriately protected by the adsorption of the compound (1), it is considered that the bump eliminating property is improved. However, this should not be construed as limiting.

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. The C 2-4 alkyl group may be selected from the group consisting of ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl. Among these, ethyl, n-propyl and n-butyl are more preferable. R ¹ , R ² , R ³ and R ⁴ in the above formula (1) may be the same group or different groups. The compound (1) in which R ¹ , R ² , R ³ and R ⁴ are the same group can be preferably employed since high purity materials are easily available.

X in the above formula ^- is a monovalent anion. X ^- it includes examples ^{^{^{^{of, OH -, F -, Cl}}}} -, Br -, I -, ClO 4 -, BH 4 - and the like. Among them, X ^- is OH ^-, Compound (1) is preferred.

Examples of preferred compounds (1) include tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide and tetrabutylammonium hydroxide. As tetrapropyl ammonium hydroxide, tetra n-propyl ammonium hydroxide is preferable, and as tetrabutyl ammonium hydroxide, tetra n-butyl ammonium hydroxide is preferable. Among them, TEAH and tetra n-butylammonium hydroxide are mentioned as preferable compound (1).

The polishing composition according to some preferred embodiments contains two or more quaternary ammonium compounds containing at least TMAH and TEAH. As described above, by using quaternary ammonium compounds having similar structures but different hydrophobicities in combination, it is possible to accurately adjust the improvement of the ridge removal property and the maintenance of the polishing rate. The composition for polishing may have a composition containing TEAH and another quaternary ammonium compound as the compound (1), or may have 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 the compound (1) contained in the composition is TEAH. It can be preferably implemented in an aspect.

In the polishing composition disclosed herein, the weight ratio of the TMAH content W _M to the compound (1) content W ₁ can suitably balance the improvement of the protrusion removal property and the maintenance of the polishing rate. It can be set as such and is not particularly limited. Here, in the polishing composition containing two or more types of compounds (1), the content W ₁ of the compound (1) refers to the total content of those 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 ) may have a value of more than 0% by weight and less than 100% by weight.

In some embodiments, W ₁ / (W _M + W ₁ ) may be, for example, 1 wt% or more, 2 wt% or more, 5 wt% or more, 7 wt% or more, 10 wt% % Or more, 20% by weight or more, or 30% by weight or more. The increase in W ₁ / (W _M + W ₁ ) tends to improve the ridge-eliminating property. In addition, from the viewpoint of facilitating balance between the bump removal 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 It may be 85 wt% or less, or 80 wt% or less.

In some other embodiments, W ₁ / (W _M + W ₁ ) is determined after polishing when polishing is performed using a polishing composition having a composition in which the total amount of compound (1) is replaced with the same weight of TMAH. When the polishing is performed using a polishing composition containing TMAH and the compound (1) in combination at a reduced value where the bump height H ₀ and the polishing rate R ₀ at that time are respectively 100% For example, the _HC can be set to 90% or less, preferably 70% or less, more preferably 50% or less, and the polishing rate _{RC at} that time can be set to 85% or more. Although not particularly limited, for example, W ₁ / (W _M) satisfying the above-described protrusion height H _C and the removal rate R _C by evaluating the removal rate and removal of protrusions under the conditions described in the examples to be described later. The range of + W ₁ ) can be grasped.

The total content of TMAH and compound (1) is not particularly limited, and may 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 based on the total weight of the polishing composition. 0.01% by weight or more, 0.05% by weight or more, 0.1% by weight or more. Also, from the viewpoint of making it easier to obtain higher bump removal property, 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 wt% or less, or 0.5 wt% or less. These contents can be preferably applied, for example, to the contents in the polishing liquid (working slurry) supplied to the object to be polished.

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

<Weak acid salt>
The polishing composition disclosed herein can contain a weak acid salt, if necessary. As a weak acid salt (typically a weak base), one which can exhibit a desired buffering action in combination with a quaternary ammonium compound can be appropriately selected. The polishing composition configured to exhibit such a buffer action has less fluctuation in pH of the polishing composition during polishing, and can be excellent in maintainability of the polishing efficiency. This makes it possible to more preferably achieve both the improvement of the bump removal property and the maintenance of the polishing rate.

Specific examples of weak acid salts include sodium carbonate, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, sodium orthosilicate, potassium orthosilicate, sodium acetate, potassium acetate, sodium propionate, sodium propionate, potassium propionate, calcium carbonate, calcium hydrogencarbonate And calcium acetate, calcium propionate, magnesium acetate, magnesium propionate, zinc propionate, manganese acetate, cobalt acetate and the like. A weak acid salt in which the anion component is a carbonate ion or a hydrogen carbonate ion is preferred, and a weak acid salt in which the anion component is a carbonate ion is particularly preferred. Moreover, as a 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 exhibiting a good buffer action in a pH range suitable for polishing a silicon substrate, at least one of the acid dissociation constant (pKa) values is 8.0 to 11.8 (for example, 8.0 to 8) Weak salts in the range of 11.5) are preferred. Preferred examples include carbonates, bicarbonates, borates, phosphates and phenol salts. Particularly preferred weak acid salts include sodium carbonate, potassium carbonate, sodium hydrogen carbonate and potassium hydrogen carbonate. Among them, potassium carbonate (K ₂ CO ₃ ) is preferable. As the value of pKa, the value of the acid dissociation constant at 25 ° C. described in the known data can be adopted.

The content of the weak acid salt can be set so that the buffering action is suitably exerted 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. It may be 0.01% by weight or more, 0.05% by weight or more, and 0.1% by weight or more. Also, from the viewpoint of making it easier to obtain higher bump removal property, 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 wt% or less, or 0.5 wt% or less. These contents can be preferably applied, for example, to the contents in the polishing liquid (working slurry) supplied to the object to be polished.

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

<Other ingredients>
The polishing composition disclosed herein is a polishing composition such as a chelating agent, an acid, a water-soluble polymer, a surfactant, an antiseptic agent, an antifungal agent, etc., to the extent that the effects of the present invention are not significantly impaired. A known additive that may be used in (the polishing composition typically used in a polishing process of a silicon substrate) may further be contained, as needed.

Examples of the above-mentioned chelating agents include aminocarboxylic acid-based chelating agents and organic phosphonic acid-based chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, ammonium hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid Sodium diethylene triamine pentaacetate, triethylene tetramine hexaacetic acid and sodium triethylene tetramine hexaacetate. Examples of organic phosphonic acid type chelating agents include 2-aminoethyl phosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylene phosphonic acid), ethylene diamine tetrakis (methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) 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-methylphosphorous Includes nosuccinic acid. Among these, organic phosphonic acid type chelating agents are more preferable. Among them, preferred are ethylenediaminetetrakis (methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) and diethylene triamine pentaacetic acid. Particularly preferred chelating agents include ethylenediamine tetrakis (methylene phosphonic acid) and diethylene triamine penta (methylene phosphonic acid). The chelating agents can be used alone or in combination of two or more. The amount of the chelating agent used is, for example, about 0.0001 to 1% by weight, about 0.001 to 0.5% by weight, or about 0.005 to 0.1% by weight of the content of the chelating agent in the working slurry. Can be set to be, but not limited to.

Examples of the acid include inorganic acids such as hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid and 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, hydroxyethylenediphosphonic acid (HEDP), nitrilotris [methylene phosphonic acid] (NTMP), phosphonobutane tricarboxylic acid (PBTC), etc. It can be mentioned. The acid may be used in the form of a salt of the acid. The salts of the acids may be, for example, alkali metal salts such as sodium salts and potassium salts, ammonium salts and the like.

Examples of the water-soluble polymer include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, polymers containing nitrogen atoms, and vinyl alcohol polymers. Specific examples thereof include hydroxyethyl cellulose, pullulan, random copolymer or block copolymer of ethylene oxide and propylene oxide, polyvinyl alcohol, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid And polystyrene sulfonate, polyacrylate, polyvinyl acetate, polyethylene glycol, polyvinyl imidazole, polyvinyl carbazole, polyvinyl pyrrolidone, polyvinyl caprolactam, polyvinyl piperidine and the like. The water-soluble polymers can be used alone or in combination of two or more. The polishing composition disclosed herein can be preferably practiced even in an embodiment substantially free of a water-soluble polymer, that is, an embodiment not at least intentionally containing a water-soluble polymer.

Examples of the above preservatives and fungicides include isothiazoline compounds, p-hydroxybenzoic acid esters, phenoxyethanol and the like.

The polishing composition disclosed herein preferably contains substantially no oxidizing agent. If an oxidizing agent is contained in the polishing composition, the composition is supplied to oxidize the surface of the silicon substrate to form an oxide film, which may lower the polishing rate. It is for. Here, that the polishing composition does not substantially contain an oxidizing agent means that at least the oxidizing agent is not intentionally added, and a trace amount of oxidizing agent is unavoidably contained due to the raw materials, the manufacturing method, etc. Being acceptable. The above 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, particularly preferably 0. It means that it is 000001 mol / L or less. The polishing composition according to a preferred embodiment does not contain an oxidizing agent. The polishing composition disclosed herein can be preferably practiced, for example, in a mode that does not contain any of hydrogen peroxide, sodium persulfate, ammonium persulfate and sodium dichloroisocyanurate.

<Composition for polishing>
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 above polishing composition may be, for example, one that is diluted with a solvent such as water and used as a polishing liquid, or may be used as it is as a polishing liquid. That is, the concept of the polishing composition in the art disclosed herein includes both a working slurry which is supplied to a polishing object and used for polishing the polishing object, and a concentrated solution (stock solution) of the working slurry. Is included. The concentration ratio of the concentrated solution may be, for example, about 2 to 50 times on a volume basis, usually about 5 to 30 times, and preferably about 5 to 20 times.

The pH of the polishing composition is typically 8.0 or more, preferably 8.5 or more, more preferably 9.0 or more, still more preferably 9.5 or more, for example 10.0 or more. When the pH is high, the polishing rate and the tendency to eliminate bumps tend to be improved. On the other hand, from the viewpoint of preventing the dissolution of the abrasive grains (for example, silica particles) and suppressing the decrease in mechanical polishing action by the abrasive grains, the pH of the polishing composition is usually appropriate to be 12.0 or less And is preferably 11.8 or less, more preferably 11.5 or less, and still more preferably 11.0 or less. These pHs can be preferably applied to any of the polishing solution (working slurry) supplied to the object to be polished and the pH of the concentrate.

The pH of the polishing composition is determined using a pH meter (for example, a glass electrode type hydrogen ion concentration indicator manufactured by Horiba, Ltd. (Model No. F-23)), and a standard buffer (phthalate pH buffer solution pH: After three-point calibration using 4.01 (25 ° C), neutral phosphate pH buffer pH: 6.86 (25 ° C), carbonate pH buffer pH: 10.01 (25 ° C)) The composition can be grasped by putting a glass electrode into a composition for polishing liquid and measuring a value after being stabilized for 2 minutes or more.

The polishing composition disclosed herein may be of one-part type or multi-part type such as two-part 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 as needed at an appropriate timing.

The method for producing the polishing composition disclosed herein is not particularly limited. For example, the respective components contained in the polishing composition may be mixed using a known mixing device such as a wing stirrer, an ultrasonic disperser, a homomixer or the like. The aspect which mixes these components is not specifically limited, For example, all the components may be mixed at once, and you may mix in the order set suitably.

<Polishing>
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 of the polishing compositions disclosed herein is prepared. Then, the polishing composition is supplied to the object to be polished and polished by a conventional method. For example, the object to be polished is set in a general polishing apparatus, and the polishing composition is supplied to the surface (surface to be polished) of the object to be polished through the polishing pad of the polishing apparatus. Typically, while continuously supplying the above-mentioned polishing composition, the polishing pad is pressed against the surface of the object to be polished and both are moved (for example, rotationally moved) relative to each other. Polishing of the object to be polished is completed through this polishing process.

The polishing pad used in the polishing step is not particularly limited. For example, any of polyurethane foam type, non-woven type, suede type, one containing abrasive grains, one not containing abrasive grains, etc. may be used. Moreover, as said polishing apparatus, you may use the double-sided polish apparatus which grind | polishes both surfaces of a polishing target simultaneously, and may use the single-sided polish apparatus which grind | polishes only the single side of a polishing target.

The above-mentioned polishing composition may be used in a mode (so-called "deep flow") which is disposable once used for polishing, or may be used repeatedly in circulation. As an example of a method of circulating and using the polishing composition, there is a method of recovering the used polishing composition discharged from the polishing apparatus into a tank and supplying the recovered polishing composition to the polishing apparatus again. .

<Use>
The polishing composition disclosed herein is excellent in the ability to eliminate the bumps on the periphery of the HLM (bump removability). Taking advantage of such features, the above-mentioned polishing composition can be preferably applied to the polishing of an object to be polished to which HLM has been applied. For example, it is suitable as a polishing composition used in the pre-polishing step of a silicon substrate to which HLM has been applied. It is desirable that the bumps on the HLM rim be eliminated early in the polishing process. For this reason, the polishing composition disclosed herein can be particularly preferably used in the first polishing step (primary polishing step) after the application of HLM. Prior to the polishing step using the polishing composition disclosed herein, the silicon substrate is subjected to general processing that can be applied to the silicon substrate, such as lapping and etching, and the application of the above-described HLM. It is also good.
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-applied silicon single crystal wafers.
In addition, the polishing composition disclosed herein can also be suitably used for polishing an object to be polished that does not have HLM, and the surface roughness of the surface of the object to be polished can be efficiently reduced.

The following examples illustrate some of the embodiments of the present invention, but are not intended to limit the present invention to those shown.

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

By diluting the polishing composition according to each example to 10 times with ion-exchanged water, 1.0 wt% of colloidal silica, 0.2 wt% of potassium carbonate, and 0.2 wt% in total of TMAH and TEAH A polishing solution was prepared which contained at a concentration of 0.01% by weight of EDTPO.

(Comparative example 1)
A polishing composition is prepared in the same manner as in Example 1 except that TMAH is used alone as a basic compound, and this is diluted 10-fold with ion-exchanged water to obtain 1.0% by weight of colloidal silica, carbonated A polishing solution was prepared containing 0.2% by weight of potassium, 0.2% by weight of TMAH, and 0.01% by weight of EDTPO.

(Comparative example 2)
A polishing composition was prepared in the same manner as in Example 1 except that TEAH was used alone as a basic compound, and this was diluted 10-fold with ion-exchanged water to obtain 1.0% by weight of colloidal silica, and carbonated A polishing solution was prepared containing 0.2% by weight of potassium, 0.2% by weight of TEAH, and 0.01% by weight of EDTPO.

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 to 10.7.

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

[Polishing conditions]
Polishing device: Single-side polishing device manufactured by Nihon Engis Co., Ltd., model "EJ-380"
Polishing pressure: 12 kPa
Plate rotation speed: 50 rpm
Head rotation speed: 40 rpm
Polishing pad: manufactured by Nitta Hearth, trade name "SUBA 800"
Abrasive fluid supply rate: 100 mL / min (over flow use)
Holding temperature of polishing environment: 25 ° C
Polishing allowance: 4 μm

(Evaluation of ridge removability)
For the silicon wafer after polishing, the surface shape of the site containing HLM is measured using a stylus surface roughness profile measurement machine (SURFCOM 1500DX, made by Tokyo Seimitsu Co., Ltd.), and the maximum height of the ridge from the reference surface around HLM The height to the point was measured. As the height of the bumps is larger, the evaluation result shows that the bump removability is worse. The obtained results are shown in the column of "Bump height" in Table 1.

(Polishing rate)
The polishing rate [nm / min] in each example and comparative example was calculated based on the time required for the above polishing, that is, the time required for the removal amount to reach 4 μm. The obtained result was converted to a relative value (relative polishing rate) in which the polishing rate of Comparative Example 1 was 100%, and the polishing rate was evaluated based on the values in the following two levels. The results are shown in Table 1. The evaluation result "G" means that a polishing rate substantially equal to or higher than that of Comparative Example 1 in which TMAH was used 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 are used in combination, the height of the bumps is lower than that of Comparative Example 1 while maintaining the polishing rate, and the bump eliminating property is evident. Could be improved. On the other hand, in Comparative Example 2 in which TEAH was used alone, the polishing rate was significantly reduced.

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

Claims

Containing abrasive grains, basic compounds and water,
The basic compound contains a combination of two or more quaternary ammonium compounds,
The two or more types of quaternary ammonium compounds are tetramethylammonium hydroxide and the following general formula (1):

(Wherein, X - 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.
The polishing composition containing 1 or more types selected from the compound represented by these.
The polishing according to claim 1, wherein the compound represented by the general formula (1) contains one or more selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide. Composition.
The compound represented by the general formula (1) is more than 0% by weight in the total weight of tetramethyl ammonium hydroxide contained in the polishing composition and the compound represented by the general formula (1). The polishing composition according to claim 1, which is used in a range of 85% by weight or less.
The polishing composition according to any one of claims 1 to 3, wherein the abrasive is a silica particle.
The polishing composition according to any one of claims 1 to 4, wherein an average primary particle diameter of the abrasive grains is 20 nm or more and 150 nm or less.
The polishing composition according to any one of claims 1 to 5, further comprising a weak acid salt.
The polishing composition according to any one of claims 1 to 6, further comprising a chelating agent.
The polishing composition according to any one of claims 1 to 7, which is used for polishing a silicon substrate having a hard laser mark.