WO2010143579A1 - Abrasive slurry, abrasive set, and method for grinding substrate - Google Patents

Abstract

Provided is an abrasive slurry comprising water, abrasive grains, and one or more additives, wherein the abrasive grains comprise particles of the hydroxide of a tetravalent metal and at least one of the additives is polyvinyl alcohol having a degree of saponification of 95 mol% or lower. Also provided are: an abrasive set that comprises portions of the abrasive slurry, one of which is a slurry containing particles and the other of which is an additive liquid containing an additive, the portions being separately stored; and a method for grinding a substrate, wherein a film to be ground is ground using the abrasive slurry. With the abrasive slurry, the abrasive set, and the substrate-grinding method, it is possible to rapidly grind an insulating film, e.g., a silicon oxide film, while minimizing scratches, in the CMP technique for making STI dielectric films, pre-metal dielectric films, interlayer dielectrics, etc. planar. The abrasive slurry has a high insulating film/polysilicon film grinding rate ratio.

Description

Abrasive, abrasive set and substrate polishing method

The present invention relates to a polishing agent used in a planarization step of a substrate surface, particularly a planarization step of an STI insulating film, a premetal insulating film, an interlayer insulating film, etc., which is a semiconductor element manufacturing technique, and polishing for storing this polishing agent. The present invention relates to an agent set and a method for polishing a substrate using an abrasive.

In recent semiconductor element manufacturing processes, the importance of processing technology for higher density and miniaturization is increasing. CMP (Chemical Mechanical Polishing) technology, which is one of them, is the formation of shallow trench isolation, planarization of premetal insulating films and interlayer insulating films, plugs and embeddings in the manufacturing process of semiconductor devices. This technology is essential for forming metal wiring.

The most frequently used abrasives for CMP are abrasives containing silica (silicon oxide) abrasive grains such as fumed silica and colloidal silica. Silica-based abrasives are characterized by high versatility, and a wide variety of films can be polished regardless of whether they are insulating films or conductive films by appropriately selecting the abrasive concentration, pH, additives, etc. .

On the other hand, the demand for abrasives containing cerium compound abrasive grains, mainly for insulating films such as silicon oxide films, is also expanding. For example, a cerium oxide-based abrasive containing cerium oxide (ceria) particles as an abrasive grain is characterized in that it can polish a silicon oxide film at a high speed even with a lower abrasive grain concentration than a silica-based abrasive.

Also, it is known that the flatness and polishing selectivity can be improved by adding an appropriate additive to the cerium oxide-based abrasive. For example, in a step of forming STI (shallow trench isolation), it is common to provide a silicon nitride film as a polishing stopper layer under the silicon oxide film. Here, when the silicon oxide film is polished, the ratio of the polishing rate of the silicon oxide film to the silicon nitride film (polishing selectivity) can be increased by appropriately selecting an additive to be added to the polishing agent.

As a result, it becomes easy to stop the polishing when the silicon nitride film is exposed, and it is possible to prevent the polishing from proceeding excessively. The cerium oxide type abrasive | polishing agent used for a CMP process is disclosed by patent document 1 and patent document 2, for example.

In recent years, the semiconductor element manufacturing process has been further miniaturized, and the demand for polishing scratches generated during polishing has become stricter. In response to this problem, attempts have been made to reduce the average particle diameter of the cerium oxide particles of the abrasive using cerium oxide as described above. However, when the average particle size is reduced, the mechanical action is lowered, and therefore there is a problem that the polishing rate is lowered.

For this problem, abrasives using tetravalent metal hydroxide particles have been studied, and this technique is disclosed in Patent Document 3. This technology takes advantage of the chemical action of tetravalent metal hydroxide particles and minimizes the mechanical action, thereby achieving both reduction of polishing scratches caused by the particles and improvement of the polishing rate. .

Japanese Unexamined Patent Publication No. 10-106994 Japanese Unexamined Patent Publication No. 08-022970 International Publication No. 02/067309

In recent years, for example, in the step of forming STI, a polysilicon film is also used as a polishing stopper layer. In this case, it was necessary to improve the polishing selectivity of the silicon oxide film with respect to the polysilicon film.

The present invention is capable of polishing an insulating film such as a silicon oxide film at a high speed and with low polishing scratches in a CMP technique for flattening an STI insulating film, a premetal insulating film, an interlayer insulating film, and the like. It is an object to provide an abrasive having polishing selectivity. Furthermore, it aims at providing the abrasive | polishing agent set which stores this abrasive | polishing agent, and the grinding | polishing method of the board | substrate using this abrasive | polishing agent.

The abrasive of the present invention is characterized by containing, as an additive, abrasive grains containing tetravalent metal hydroxide particles, and polyvinyl alcohol having a saponification degree of 95 mol% or less. Thereby, a high polishing rate ratio of the insulating film to the polysilicon film can be obtained. The case where a silicon oxide film is used as the insulating film will be described as an example. With the above structure, the silicon oxide film can be polished with priority over polysilicon.

The present invention is (1) an abrasive containing water, abrasive grains and additives,
The abrasive grains contain tetravalent metal hydroxide particles,
The present invention relates to an abrasive in which at least one of the additives is polyvinyl alcohol having a saponification degree of 95 mol% or less.

The present invention also relates to (2) the abrasive according to (1) above, wherein the abrasive has an average particle size of 1 nm to 400 nm.

The present invention also relates to (3) the abrasive according to (1) or (2) above, wherein the pH of the abrasive is 3.0 or more and 12.0 or less.

Further, the present invention provides (4) the polishing according to any one of (1) to (3), wherein the content of the abrasive grains is 0.01 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the abrasive. It relates to the agent.

The present invention also relates to (5) the abrasive according to any one of (1) to (4) above, wherein the zeta potential of the abrasive grains in the abrasive is −20 mV to +20 mV.

The present invention also relates to (6) the abrasive according to any one of (1) to (5) above, wherein the polyvinyl alcohol content is 0.01 parts by mass or more with respect to 100 parts by mass of the abrasive.

The present invention also relates to (7) the abrasive according to any one of the above (1) to (6) used for polishing a surface to be polished containing at least silicon oxide on the surface.

The present invention also relates to (8) the abrasive according to any one of (1) to (7) above, wherein the tetravalent metal hydroxide is at least one of a rare earth metal hydroxide and zirconium hydroxide.

In the present invention, (9) the substrate on which the film to be polished is formed is pressed against the polishing pad of the polishing platen and pressed, and the polishing agent of any of the above (1) to (8) is applied to the film to be polished and the polishing pad. The substrate and the polishing surface plate are relatively moved while polishing the film to be polished.

The present invention also relates to (10) the method for polishing a substrate according to (9) above, wherein the Shore D hardness of the polishing pad is 70 or more.

Furthermore, the present invention is an abrasive set that is stored separately as (11) slurry and an additive solution, and is mixed immediately before polishing or at the time of polishing to be any of the above-mentioned abrasives (1) to (8). The slurry includes abrasive grains and water, and the additive liquid relates to an abrasive set including the additive and water.

The disclosure of the present invention relates to the subject matter described in Japanese Patent Application No. 2009-138124 filed on June 9, 2009 and Japanese Patent Application No. 2009-236488 filed on October 13, 2009. The disclosure is incorporated herein by reference.

The present invention provides a CMP technique for planarizing an STI insulating film, a premetal insulating film, an interlayer insulating film, and the like. An insulating film such as a silicon oxide film can be polished at high speed with low polishing scratches, and the insulating film and the polysilicon film can be polished. An abrasive having a high polishing rate ratio, an abrasive set for storing the abrasive, and a method for polishing a substrate using the abrasive can be provided.

FIG. 1 is a graph showing the relationship between the degree of saponification of polyvinyl alcohol and the selectivity of the insulating film to the polysilicon film in the examples of the present application.

In the present invention, “high selectivity of insulating film relative to polysilicon film” means that the polishing rate of the insulating film is higher than the polishing rate of the polysilicon film. “Insulating film” may be omitted, and simply “high selectivity for polysilicon film”. Hereinafter, unless otherwise specified, a case where a silicon oxide film is applied as an insulating film will be described as an example. For example, “the selectivity to a polysilicon film is excellent” means that the selectivity of the silicon oxide film to the polysilicon film is Means high.

Although the mechanism of action for obtaining such an effect is not necessarily clear, the present inventors presume as follows. That is, the polyvinyl alcohol is considered to act on abrasive grains such as tetravalent metal hydroxide particles and / or a film to be polished. In particular, it is estimated that a high polishing rate ratio with respect to the polysilicon film is brought about by the difference in the degree of interaction between the silicon oxide film and polyvinyl alcohol and the interaction between the polysilicon film and polyvinyl alcohol. More specifically, it is considered that the interaction between the polysilicon film and the polyvinyl alcohol is strengthened. That is, it is presumed that the polyvinyl alcohol is effectively adsorbed on the hydrophobic polysilicon film and becomes a protective film to inhibit polishing, resulting in a difference in polishing rate.

This reason is considered as follows. That is, since a vinyl alcohol monomer cannot be theoretically synthesized, polyvinyl alcohol is generally obtained by polymerizing a vinyl carboxylate monomer such as a vinyl acetate monomer to obtain vinyl carboxylate, and then (Hydrolysis).

Therefore, for example, polyvinyl alcohol obtained using a vinyl acetate monomer as a raw material has —OCOCH ₃ as a functional group and —OH hydrolyzed in the molecule, and is a ratio of —OH. Is defined as the degree of saponification. When the degree of saponification is 95 mol% or less, -OCOCH _{3 that} is more hydrophobic than -OH is effectively adsorbed on the hydrophobic polysilicon film, and becomes a protective film that inhibits polishing, resulting in polishing. It is estimated that there will be a difference in speed.

In the present invention, the abrasive refers to a composition that is brought into contact with the film to be polished at the time of polishing, and specifically includes water, abrasive grains, and additives. Hereafter, each component and the component which can be added arbitrarily are demonstrated in order.

(Abrasive grains)
One of the specific aspects of the abrasive | polishing agent of this invention contains a tetravalent metal hydroxide particle as said abrasive grain. The tetravalent metal hydroxide particles are preferable in terms of high reactivity with silicon oxide and high polishing rate compared to conventional abrasive grains such as silica and cerium oxide. Examples of other abrasive grains that can be used in the abrasive of the present invention include silica, alumina, cerium oxide, and the like.

In the abrasive grains, the content of the tetravalent metal hydroxide particles is preferably 80% by mass or more, more preferably 90% by mass or more, and 95% by mass or more based on the whole abrasive grains. Is more preferably 98% by mass or more, and particularly preferably 99% by mass or more. The abrasive grains are composed of the tetravalent metal hydroxide particles in terms of easy adjustment of the abrasive and excellent polishing characteristics (100% by mass of the abrasive grains are the tetravalent metal hydroxide particles). Is most preferred.

As the tetravalent metal hydroxide particles, it is preferable to use at least one of rare earth metal hydroxide and zirconium hydroxide, but two or more kinds selected from rare earth metal hydroxide and zirconium hydroxide are used. There is no problem. Among them, it is preferable to use cerium hydroxide Ce (OH) ₄ as the rare earth metal hydroxide because it has a high polishing rate.

As a method for producing tetravalent metal hydroxide particles, a method of mixing a tetravalent metal salt and an alkali solution can be used. This method is described in, for example, “Science of rare earths” (edited by Adiya Ginya, Kagaku Dojin, 1999), pages 304-305.

Examples of the tetravalent metal salt include M (SO ₄ ) ₂ , M (NH ₄ ) ₂ (NO ₃ ) ₆ , M (NH ₄ ) ₄ (SO ₄ ) ₄ (M represents a rare earth element), Zr (SO ₄ ) ₂ .4H ₂ O and the like can be mentioned. As mentioned above, M is more preferably chemically active cerium (Ce).

As the alkaline solution, for example, aqueous ammonia, potassium hydroxide, sodium hydroxide and the like can be used, among which aqueous ammonia is preferable. The tetravalent metal hydroxide particles synthesized by the above method can be washed to remove metal impurities. For washing the metal hydroxide, a method of repeating solid-liquid separation several times by centrifugation or the like can be used.

When the tetravalent metal hydroxide particles obtained above are aggregated, it is preferably dispersed in water by an appropriate method. As a method for dispersing the tetravalent metal hydroxide particles in water, which is a main dispersion medium, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to the dispersion treatment using a normal stirrer. Regarding the dispersion method and the particle size control method, for example, the method described in “The Complete Collection of Dispersion Technology” [Information Organization Co., Ltd., July 2005] Chapter 3, “Latest Development Trends and Selection Criteria of Various Dispersers” Can be used.

The average particle diameter of the abrasive grains in the abrasive is preferably 1 nm or more, more preferably 2 nm or more, and more preferably 10 nm or more as a lower limit in order to avoid the polishing rate becoming too low. Is more preferable.

Further, the upper limit of the average grain size of the abrasive grains is preferably 400 nm or less, more preferably 300 nm or less, and further preferably 250 nm or less in that the film to be polished is less likely to be damaged. .

In the present invention, the average grain size of abrasive grains refers to Z-average Size obtained by cumulant analysis using a dynamic light scattering method. For example, a product name: Zetasizer Nano S manufactured by Malvern Co., Ltd. can be used.

As a more specific example, the measurement sample is adjusted by diluting the abrasive with water so that the concentration of the abrasive grains becomes 0.1 parts by mass. About 1 mL of the obtained measurement sample is placed in a 1 cm square cell, and placed on the Zetasizer Nano S. The refractive index of the dispersion medium is 1.33, the viscosity is 0.887, measurement is performed at 25 ° C., and the value displayed as Z-average Size is read.

The specific surface area of the abrasive grains is preferably 100 m ² / g or more from the viewpoint of increasing the chemical action with the film to be polished and improving the polishing rate. The specific surface area of the particles can be measured by the BET method.

As a method for measuring the specific surface area by the BET method, for example, an abrasive is dried at 150 ° C. for 3 hours and further vacuum degassed and dried at 150 ° C. for 1 hour to obtain a measurement sample. This was measured by using a gas adsorption amount measuring device AUTOSORB-1MP type manufactured by QUANTACHROME, and measuring the adsorption amount relative to the relative pressure and analyzing the data by the BET method based on the multimolecular adsorption theory. (BET three-point method using data of 1, 0.2 and 0.3).

The concentration of the abrasive grains is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more with respect to 100 parts by mass of the abrasive, in that a suitable polishing rate can be obtained. More preferably, the amount is 0.05 parts by mass or more. Further, the upper limit is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 2 parts by mass or less, and particularly preferably 1 part by mass or less from the viewpoint that the storage stability of the abrasive can be increased.

(Additive)
The abrasive | polishing agent of this invention contains an additive. Here, the additive refers to a substance contained other than water and abrasive grains in order to adjust the dispersibility, polishing characteristics, storage stability and the like of the abrasive grains.

(Polyvinyl alcohol)
One of the specific embodiments of the abrasive of the present invention is characterized in that it contains polyvinyl alcohol as the additive. Polyvinyl alcohol has the effect of improving the stability of the abrasive. When the hydroxyl group of polyvinyl alcohol interacts with the abrasive grains, aggregation can be suppressed, and changes in the particle size of the abrasive can be suppressed to improve stability.

As described above, since a vinyl alcohol monomer cannot be theoretically synthesized, polyvinyl alcohol is generally obtained by polymerizing a vinyl carboxylate monomer such as a vinyl acetate monomer. Thereafter, it is obtained by saponification (hydrolysis). Thus, for example, polyvinyl alcohol obtained using a vinyl acetate monomer as a raw material has —OCOCH ₃ and hydrolyzed —OH as functional groups in the molecule. In the present invention, polyvinyl alcohol is defined to include not only a homopolymer of vinyl alcohol (degree of saponification 100%) but also a copolymer of vinyl carboxylate and vinyl alcohol.

In addition, a polyvinyl alcohol derivative obtained by introducing a functional group into polyvinyl alcohol can also be used. In the present invention, such a polyvinyl alcohol derivative is also defined as polyvinyl alcohol.

Examples of the polyvinyl alcohol derivative include reactive polyvinyl alcohol (for example, Goseifamer (registered trademark) Z, etc., manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and cationized polyvinyl alcohol (for example, GOGO Synthetic Chemical Co., Ltd., Go Cefaimer (registered trademark) K, etc.), anionized polyvinyl alcohol (for example, Goseiran (registered trademark) L, Gosenal (registered trademark) T, etc., manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), hydrophilic group-modified polyvinyl alcohol (for example, Japan Synthetic Chemical Industry Co., Ltd., Ecomate (registered trademark), etc.).

Each compound defined as polyvinyl alcohol in the abrasive of the present invention can be used alone or in combination of two or more for the purpose of adjusting selectivity and flatness. A plurality of polyvinyl alcohols having different saponification degrees, polymerization degrees, etc., which will be described later, can also be used in combination.

(Saponification degree)
As described above, in general, polyvinyl alcohol has —OCOCH ₃ and hydrolyzed —OH as functional groups in the molecule, and the ratio of —OH is defined as the degree of saponification. Defined. When the saponification degree is not more than a predetermined value, -OCOCH _{3 that} is more hydrophobic than -OH is effectively adsorbed on the hydrophobic polysilicon film and becomes a protective film, which hinders polishing. It is estimated that a difference occurs in the polishing rate. This tends to increase the polishing rate ratio (hereinafter also referred to as selectivity) of the silicon oxide film to the polysilicon film. In this respect, the upper limit of the saponification degree of polyvinyl alcohol is preferably 95 mol% or less, more preferably 90 mol% or less, still more preferably 88 mol% or less, particularly preferably 85 mol% or less, and 83 mol%. % Or less is very preferable, and 80 mol% or less is very preferable.

The lower limit of the degree of saponification is not particularly limited, but is preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more from the viewpoint of solubility in water. The degree of saponification of polyvinyl alcohol can be measured in accordance with JIS K 6726 (Japanese Industrial Standard, polyvinyl alcohol test method).

Moreover, when using several polyvinyl alcohol from which a saponification degree differs, the saponification degree of at least 1 sort (s) of polyvinyl alcohol should just be 95 mol% or less, and from a viewpoint which can improve selectivity, each saponification degree and It is more preferable that the average degree of saponification calculated from the blending ratio is 95 mol% or less.

(Degree of polymerization)
The average degree of polymerization of polyvinyl alcohol is not particularly limited, but the upper limit is preferably 3000 or less, more preferably 2000 or less, and most preferably 1000 or less from the viewpoint of increasing the polishing rate of the silicon oxide film.

Further, from the viewpoint of enhancing the selectivity, the lower limit is preferably 50 or more, more preferably 100 or more, and further preferably 150 or more. In addition, the average degree of polymerization of polyvinyl alcohol can be measured based on the above-mentioned JIS K 6726 (polyvinyl alcohol test method).

The total concentration of polyvinyl alcohol having a saponification degree of 95 mol% or less used as an additive is preferably 0.001 part by mass or more with respect to 100 parts by mass of the polishing agent from the viewpoint of improving selectivity. 0.01 parts by mass or more is more preferable, and 0.1 parts by mass or more is more preferable.

Also, from the viewpoint of increasing the polishing rate of the silicon oxide film, the upper limit is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 3 parts by mass or less with respect to 100 parts by mass of the abrasive.

(Second additive)
The abrasive of the present invention may further contain another additive (hereinafter also referred to as “second additive”) in addition to the polyvinyl alcohol for the purpose of adjusting polishing characteristics. Specific examples of such additives include carboxylic acids, amino acids, amphoteric surfactants, anionic surfactants, nonionic surfactants, cationic surfactants, and the like. Can be used alone or in combination of two or more. Of these, carboxylic acids, amino acids, and amphoteric surfactants are preferable from the viewpoint of the balance between abrasive dispersibility and polishing characteristics.

Among the above, carboxylic acid has an effect of stabilizing pH, and specific examples include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and lactic acid.

Amino acids have the effect of improving the dispersibility of abrasive grains such as the tetravalent metal hydroxide particles and improving the polishing rate. Specifically, for example, arginine, lysine, aspartic acid, glutamic acid, asparagine, glutamine Histidine, proline, tyrosine, tryptophan, serine, threonine, glycine, alanine, β-alanine, methionine, cysteine, phenylalanine, leucine, valine, isoleucine and the like.

The amphoteric surfactant has the effect of improving the dispersibility of abrasive grains such as the tetravalent metal hydroxide particles and improving the polishing rate. Specifically, for example, betaine, β-alanine betaine, lauryl Examples include betaine, stearyl betaine, lauryl dimethylamine oxide, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, lauric acid amidopropyl betaine, coconut oil fatty acid amidopropyl betaine, and lauryl hydroxysulfobetaine. Of these, betaine, β-alanine betaine, and amide amidopropyl betaine are more preferable from the viewpoint of improving dispersibility stability.

Anionic surfactants have the effect of adjusting the flatness and in-plane uniformity of the surface to be polished after polishing. For example, lauryl sulfate triethanolamine, lauryl ammonium sulfate, polyoxyethylene alkyl ether sulfate triethanolamine And special polycarboxylic acid type polymer dispersants.

The nonionic surfactant has an effect of adjusting the flatness and in-plane uniformity of the surface to be polished after polishing, for example, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, Polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan Monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, poly Oxyethylene sorbitan trioleate, polyoxyethylene sorbite tetraoleate, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil , 2-hydroxyethyl methacrylate, alkyl alkanolamides and the like.

The cationic surfactant has an effect of adjusting the flatness and in-plane uniformity of the surface to be polished after completion of polishing, and examples thereof include coconut amine acetate and stearyl amine acetate.

When using these second additives, the addition amount is 0.01 parts by mass or more with respect to 100 parts by mass of the abrasive in terms of obtaining the additive effect while suppressing the sedimentation of the abrasive grains. The range is preferably 10 parts by mass or less.

(Water-soluble polymer)
The abrasive of the present invention may contain a water-soluble polymer other than polyvinyl alcohol for the purpose of adjusting the flatness and in-plane uniformity of the polishing characteristics. Here, the water-soluble polymer is defined as a polymer that dissolves 0.1 g or more with respect to 100 g of water.

Specific examples of the water-soluble polymer are not particularly limited. For example, polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan, and pullulan;
Polycarboxylic acids such as polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), polyamic acid, polyglyoxylic acid, and salts thereof;
Vinyl polymers such as polyvinylpyrrolidone and polyacrolein;
Acrylic polymers such as polyacrylamide and polydimethylacrylamide;
Examples thereof include polyethylene glycol, polyoxypropylene, polyoxyethylene-polyoxypropylene condensate, and polyoxyethylene-polyoxypropylene block polymer of ethylenediamine. The polycarboxylic acid may be a copolymer. Moreover, as the salt, ammonium salt, sodium salt, etc. are mentioned, for example.

When these water-soluble polymers are used, the addition amount is 0.01 parts by mass or more with respect to 100 parts by mass of the abrasive because the effect of adding the water-soluble polymer is obtained while suppressing sedimentation of abrasive grains. The amount is preferably 5 parts by mass or less.

(Abrasive properties)
(PH)
The pH of the abrasive of the present invention is preferably in the range of 3.0 or more and 12.0 or less in terms of excellent storage stability and polishing rate of the abrasive. The lower limit of the pH mainly affects the polishing rate, is preferably 3.0 or more, more preferably 4.0 or more, and further preferably 5.0 or more. Further, the upper limit mainly affects the polishing rate, is preferably 12.0 or less, more preferably 11.0 or less, and still more preferably 10.0 or less.

The pH can be adjusted by adding an acid component such as an inorganic acid or an organic acid, an alkali component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH), or imidazole. A buffer may be added to stabilize the pH. Examples of such a buffer include acetate buffer and phthalate buffer.

The pH of the abrasive of the present invention can be measured with a pH meter (for example, Model PH81 manufactured by Yokogawa Electric Corporation). Specifically, for example, the pH meter is calibrated at two points using a phthalate pH buffer solution (pH 4.01) and a neutral phosphate pH buffer solution (pH 6.86) as standard buffers, and then the pH meter The value after the electrode was stabilized after 2 minutes or more had passed was measured. At this time, the liquid temperature of the standard buffer and the abrasive is both 25 ° C.

(Zeta potential)
The zeta potential of the abrasive grains in the abrasive is preferably −20 mV to +20 mV, more preferably 0 mV to +20 mV, from the viewpoint of enhancing the selectivity to polysilicon. For the zeta potential measurement, for example, a product name: Zeta Sizer 3000HS manufactured by Malvern can be used. For example, the abrasive is diluted with water so that the amount of scattered light recommended for the Zeta Sizer 3000HS is measured. Can do.

The abrasive according to the present invention may be stored as a one-component abrasive containing the abrasive, the additive, and water, and includes at least a slurry containing abrasive and water, and at least an additive and water. You may preserve | save as a two-pack type abrasive | polishing agent set which separated the additive liquid.

The polyvinyl alcohol and the water-soluble polymer are preferably contained in the additive liquid out of the two liquids. Moreover, it is preferable that the said buffer solution is contained in an addition liquid among two liquids.

The abrasive set is mixed immediately before or at the time of polishing to become an abrasive. In either case, the slurry may be stored as a concentrated slurry, a concentrated additive solution, or a concentrated abrasive with reduced water content, and diluted with water during polishing.

When storing the slurry and the additive solution as a two-component abrasive, the polishing rate can be adjusted by arbitrarily changing the composition of these two components. In the case of polishing with a two-pack type abrasive, the method for supplying the abrasive onto the polishing surface plate includes the following methods. For example, the slurry and the additive solution are sent through separate pipes, and these pipes are joined, mixed and supplied, the concentrated slurry, the concentrated additive solution, and water are sent through separate pipes, and these are joined. A method of supplying the mixture by mixing, a method of mixing and supplying the slurry and the additive liquid in advance, a method of mixing and supplying the concentrated slurry, the concentrated additive liquid, and water in advance can be used.

In the case of a one-part abrasive containing abrasive grains, additives, and water, as a method of supplying the abrasive onto the polishing surface plate, for example, a method of supplying the abrasive directly by feeding, a concentrated abrasive, A method of feeding water through separate pipes and joining and mixing them, a method of feeding concentrated abrasives and water in advance, and the like can be used.

In the polishing method of the present invention, the substrate on which the film to be polished is formed is pressed against the polishing pad of the polishing platen and pressed, and the polishing agent of the present invention is supplied between the film to be polished and the polishing pad, The film to be polished is polished by relatively moving the polishing platen.

Examples of the substrate include a substrate in which a semiconductor element is manufactured, for example, a substrate in which an insulating film is formed on a semiconductor substrate on which an STI pattern, a gate pattern, a wiring pattern, and the like are formed. Examples of the film to be polished include an insulating film formed on these patterns, such as a silicon oxide film and a polysilicon film. In the present invention, the film to be polished may be a single film or a plurality of films. When a plurality of films are exposed on the substrate surface, they can be regarded as films to be polished.

By polishing a silicon oxide film or a polysilicon film formed on such a semiconductor substrate with the above-described abrasive, unevenness on the surface of the silicon oxide film layer can be eliminated and a smooth surface can be obtained over the entire surface of the semiconductor substrate. . Thus, the abrasive of the present invention is preferably used for polishing a surface to be polished containing at least silicon oxide on the surface.

When at least the surface of the film to be polished contains silicon oxide and further provided with a polishing stopper layer below it, the polishing stopper layer is preferably a polysilicon film, a silicon nitride film or the like. By stopping polishing when a polishing stopper layer having a lower polishing rate than silicon oxide is exposed, it is possible to prevent excessive polishing of the silicon oxide film as the film to be polished, and the flatness after polishing of the film to be polished Can be improved.

Also, the abrasive of the present invention can be suitably used for STI (shallow trench isolation). For use in STI, the selectivity of the silicon oxide film to the polishing stopper layer is preferably 100 or more. This is because if the selectivity is less than 100, the difference between the silicon oxide film polishing rate and the polysilicon film polishing rate is small, and it is difficult to stop polishing at a predetermined position when performing STI. If the selectivity is 100 or more, polishing can be easily stopped, and STI is preferable.

Furthermore, it can also be used for polishing premetal insulating films. As the premetal insulating film, in addition to silicon oxide, for example, phosphorus-silicate glass or boron-phosphorus-silicate glass is used, and silicon oxyfluoride, fluorinated amorphous carbon, or the like can also be used.

Hereinafter, the polishing method will be described by taking as an example the case of a semiconductor substrate on which an insulating film is formed.

In the polishing method of the present invention, as a polishing apparatus, a general polishing apparatus having a holder capable of holding a substrate having a film to be polished such as a semiconductor substrate and a polishing surface plate to which a polishing pad can be attached is used. it can.

The motor and the like whose rotation speed can be changed are attached to the holder and the polishing surface plate, respectively. For example, a polishing apparatus: model number EPO-111 manufactured by Ebara Corporation can be used.

As the polishing pad, general nonwoven fabrics, foams, non-foams and the like can be used. As materials, polyurethane, acrylic, polyester, acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly-4- Polyamides such as methylpentene, cellulose, cellulose ester, nylon (trade name) and aramid, resins such as polyimide, polyimideamide, polysiloxane copolymer, oxirane compound, phenol resin, polystyrene, polycarbonate and epoxy resin can be used.

In particular, foamed polyurethane and non-foamed polyurethane are preferred from the viewpoint of polishing speed and flatness.

The Shore D hardness of the polishing pad is preferably 70 or more, more preferably 75 or more, and still more preferably 80 or more, from the viewpoint of improving flatness. Shore D hardness can be measured with a Shore D hardness meter [for example, Polymer Instruments Co., Ltd. Asker Rubber Hardness Tester Type D].

Further, it is preferable that the polishing pad is grooved so that the abrasive is accumulated. The polishing conditions are not limited, but the rotation speed of the surface plate is preferably 200 min ⁻¹ or less so that the semiconductor substrate does not jump out, and the pressure (working load) applied to the semiconductor substrate is preferably 100 kPa or less so as not to cause polishing scratches. . During polishing, a polishing agent is continuously supplied to the polishing pad by a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with the abrasive | polishing agent.

The semiconductor substrate after polishing is preferably washed well under running water to remove particles adhering to the substrate. In addition to pure water, dilute hydrofluoric acid or aqueous ammonia may be used for cleaning, and a brush may be used in combination to increase cleaning efficiency.

Further, after washing, it is preferable to dry after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like.

As a method for producing an insulating film using the abrasive of the present invention, a CVD method represented by a low pressure CVD method, a quasi-atmospheric pressure CVD method, a plasma CVD method, etc., or a spin coating method in which a liquid material is applied to a rotating substrate Etc.

The silicon oxide film formed by the low pressure CVD method is obtained, for example, by causing a thermal reaction between monosilane (SiH ₄ ) and oxygen (O ₂ ).

Moreover, the silicon oxide film by the quasi-atmospheric pressure CVD method can be obtained, for example, by thermally reacting tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) and ozone (O ₃ ).

As another example, a silicon oxide film can be similarly obtained even when tetraethoxysilane and oxygen are subjected to plasma reaction.

The silicon oxide film formed by the spin coating method can be obtained, for example, by applying a liquid raw material containing inorganic polysilazane, inorganic siloxane or the like on a substrate and performing a thermosetting reaction in a furnace body or the like.

Examples of the method for forming a polysilicon film include a low pressure CVD method in which monosilane is thermally reacted, a plasma CVD method in which monosilane is plasma-reacted, and the like.

In order to stabilize the film quality of the silicon oxide film, polysilicon film, etc. obtained by the above method, heat treatment may be performed at a temperature of 200 to 1000 ° C. as necessary.

In addition, the silicon oxide film obtained by the above method may contain a small amount of boron (B), phosphorus (P), carbon (C) or the like in order to improve the embedding property.

The abrasive and polishing method of the present invention can also be applied to films other than insulating films such as silicon oxide films. For example, high dielectric constant films such as Hf-based, Ti-based, and Ta-based oxides, semiconductor films such as silicon, amorphous silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, and organic semiconductors, phase change films such as GeSbTe, Examples thereof include inorganic conductive films such as ITO, polyimide-based, polybenzoxazole-based, acrylic-based, epoxy-based, phenol-based polymer resin films, and the like.

Further, the abrasive and polishing method of the present invention can be applied not only to film-like materials but also to various substrate materials such as glass, silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, sapphire, and plastic.

Furthermore, according to the polishing agent and polishing method of the present invention, not only the manufacture of semiconductor elements, but also image display devices such as TFT and organic EL, photomasks, lenses, prisms, optical fibers, optical components such as single crystal scintillators, optical It can be used for the manufacture of magnetic storage devices such as switching elements, optical elements such as optical waveguides, light emitting elements such as solid state lasers and blue laser LEDs, magnetic disks, and magnetic heads.

(Synthesis of tetravalent metal hydroxide)
430 g of Ce (NH ₄ ) ₂ (NO ₃ ) ₆ was dissolved in 7300 g of pure water. Then, while stirring this solution, 240 g of ammonia water (25% by mass aqueous solution) was added dropwise to add 160 g of hydroxylated water. A dispersion (yellowish white) containing cerium was obtained.

The resulting cerium hydroxide dispersion was subjected to solid-liquid separation by centrifugation (4000 min ⁻¹ , 5 minutes). The liquid was removed, pure water was newly added, and centrifugation was again performed under the above conditions. Such an operation was repeated 4 times for washing. When the specific surface area of the obtained particles was measured by the BET method, it was 200 m ² / g.

Further, 10 g of the obtained particles and 990 g of water were mixed and dispersed using an ultrasonic cleaner to prepare concentrated cerium hydroxide slurry (cerium hydroxide concentration 1 mass%).

The concentrated cerium hydroxide slurry was diluted with water, and the average particle size (Z-average Size) was measured using a product name Zeta Sizer Nano S manufactured by Malvern, Inc., and found to be 115 nm. As a measuring method, the concentration of the tetravalent metal hydroxide particles is diluted with water so as to be 0.1 part by mass, and about 1 mL is put into a 1 cm square cell and installed in the Zetasizer Nano S. The refractive index of the dispersion medium was 1.33, the viscosity was 0.887, measurement was performed at 25 ° C., and the value displayed as Z-average Size was read.

In addition, in order to measure the zeta potential of the particles in the concentrated cerium hydroxide slurry, the product was diluted with water to an appropriate concentration and then measured using a product name Zeta Sizer 3000HS manufactured by Malvern, and found to be +43 mV. The measurement was performed at 25 ° C. by diluting the concentrated cerium hydroxide slurry with water so that the amount of scattered light recommended by the Zetasizer 3000HS was obtained.

Example 1
5% by mass of polyvinyl alcohol [PVA-203 manufactured by Kuraray Co., Ltd., average polymerization degree 300, saponification degree 88 mol%], acetic acid 0.4% by mass, imidazole 0.66% by mass and water 93.94% by mass. 100 g of the concentrated additive solution, 100 g of the concentrated cerium hydroxide slurry obtained above and 800 g of water were mixed to prepare an abrasive containing 0.1% by mass of cerium hydroxide and 0.5% by mass of polyvinyl alcohol. The pH of the abrasive was 6.6, the average particle size was 140 nm, and the zeta potential was +6 mV. The average particle size and zeta potential were measured in the same manner as described above.

(Example 2)
The concentration of cerium hydroxide was set to be the same as in Example 1 except that 5% by mass of PVA-403 manufactured by Kuraray Co., Ltd., an average polymerization degree of 300 and a saponification degree of 80 mol% was used as the polyvinyl alcohol used in the concentrated additive solution. An abrasive containing 1% by mass and a polyvinyl alcohol concentration of 0.5% by mass was prepared.

(Example 3)
A cerium hydroxide concentration of 0.1 was used in the same manner as in Example 1 except that PVA-205 manufactured by Kuraray Co., Ltd., an average polymerization degree of 500, and a saponification degree of 88 mol% were used as polyvinyl alcohol for the concentrated additive solution. An abrasive containing 5% by mass and a polyvinyl alcohol concentration of 0.5% by mass was prepared.

Example 4
A cerium hydroxide concentration of 0.1 was used in the same manner as in Example 1 except that 5% by mass of PVA-405 manufactured by Kuraray Co., Ltd., an average polymerization degree of 500 and a saponification degree of 80 mol% was used as the polyvinyl alcohol used in the concentrated additive solution. An abrasive containing 5% by mass and a polyvinyl alcohol concentration of 0.5% by mass was prepared.

(Example 5)
A cerium hydroxide concentration of 0.1 was used in the same manner as in Example 1 except that 5% by mass of PVA-505 manufactured by Kuraray Co., Ltd., an average polymerization degree of 500, and a saponification degree of 73 mol% was used as the polyvinyl alcohol used in the concentrated additive solution. An abrasive containing 5% by mass and a polyvinyl alcohol concentration of 0.5% by mass was prepared.

(Example 6)
2% by mass of polyvinyl alcohol (PVA-217 manufactured by Kuraray Co., Ltd., average degree of polymerization 1700, degree of saponification 88 mol%), 0.4% by mass of acetic acid, 0.66% by mass of imidazole and 96.94% by mass of water 100 g of the concentrated additive solution, 200 g of the concentrated cerium hydroxide slurry obtained above and 700 g of water were mixed to prepare an abrasive containing a cerium hydroxide concentration of 0.2 mass% and a polyvinyl alcohol concentration of 0.2 mass%.

(Example 7)
Polyvinyl alcohol (Kuraray Co., Ltd. C-506, cation modification, average polymerization degree 600, saponification degree 77 mol%) 10% by mass, acetic acid 0.4% by mass, imidazole 0.66% by mass and water 88.94% by mass 100 g of the concentrated additive solution containing, 200 g of the concentrated cerium hydroxide slurry obtained above and 700 g of water were mixed to prepare an abrasive containing 0.2% by mass of cerium hydroxide and 1% by mass of polyvinyl alcohol.

(Comparative Example 1)
100 g of the concentrated cerium hydroxide slurry and 900 g of water were mixed, and a 5 mass% imidazole aqueous solution was added until the pH reached 6.6 to prepare an abrasive.

(Comparative Example 2)
A cerium hydroxide concentration of 0.1 was used in the same manner as in Example 1 except that 5% by mass of PVA-103 manufactured by Kuraray Co., Ltd., an average degree of polymerization of 300 and a degree of saponification of 98 mol% was used as the polyvinyl alcohol used in the concentrated additive solution. An abrasive containing 5% by mass and a polyvinyl alcohol concentration of 0.5% by mass was prepared.

(Comparative Example 3)
A cerium hydroxide concentration of 0.1 was used in the same manner as in Example 1 except that 5% by mass of PVA-105 manufactured by Kuraray Co., Ltd., an average polymerization degree of 500 and a saponification degree of 98 mol% was used as the polyvinyl alcohol used in the concentrated additive solution. An abrasive containing 5% by mass and a polyvinyl alcohol concentration of 0.5% by mass was prepared.

(Comparative Example 4)
1 kg of cerium oxide particles, 23 g of a commercially available ammonium polyacrylate salt solution (40% by mass) and 8977 g of deionized water were mixed and subjected to ultrasonic dispersion while stirring.

After filtration through a 1 micron filter, deionized water was further added to obtain a concentrated cerium oxide slurry having 5% by mass of cerium oxide.

100 g of the concentrated cerium oxide slurry and 900 g of water were mixed, and 1N nitric acid was added until the pH reached 4.2 to prepare an abrasive (cerium oxide particle concentration: 0.5 mass%).

(Comparative Example 5)
Contains 2% by weight of polyvinyl alcohol (PVA-117 manufactured by Kuraray Co., Ltd., average polymerization degree 1700, saponification degree 98 mol%), acetic acid 0.4% by weight, imidazole 0.66% by weight and water 96.94% by weight. 100 g of the concentrated additive solution, 200 g of the concentrated cerium hydroxide slurry obtained above and 700 g of water were mixed to prepare an abrasive containing a cerium hydroxide concentration of 0.2 mass% and a polyvinyl alcohol concentration of 0.2 mass%.

The pH, average particle diameter, and zeta potential of each of the abrasives of Examples 2 to 6 and Comparative Examples 1 to 5 were measured in the same manner as in Example 1.

(Insulating film polishing)
An evaluation wafer 1 in which silicon oxide (SiO ₂ ) having a film thickness of 1000 nm is formed on a silicon (Si) substrate having a diameter of 200 mm is fixed to a substrate holder of a polishing apparatus (model number EPO-111 manufactured by Ebara Corporation). did. Further, a polishing pad IC-1000 made of porous urethane resin (model number, groove shape: perforate manufactured by Rodel) was attached to a polishing surface plate having a diameter of 600 mm.

The substrate holder was pressed against the polishing pad so that the silicon oxide film of the evaluation wafer 1 was in contact with the polishing pad, and the processing load was set to 30 kPa. While dropping the above-prepared abrasive on the polishing pad at a rate of 200 mL / min, the polishing platen and the substrate holder were operated at 50 min ⁻¹ to polish the evaluation wafer for 60 seconds.

The polished evaluation wafer 1 was thoroughly washed with pure water and dried. Thereafter, the residual film thickness of silicon oxide was measured using an optical interference film thickness apparatus (trade name: Nanospec AFT-5100, manufactured by Nanometrics). Here, the silicon oxide polishing rate [RR (SiO ₂ )] per minute was determined from (the amount of reduction of the silicon oxide film) / (polishing time).

Further, an evaluation wafer 2 in which polysilicon (poly-Si) having a film thickness of 250 nm was formed on the entire surface of a silicon (Si) substrate having a diameter of 200 mm was prepared and polished for 60 seconds by the same method as described above. The polished evaluation wafer 2 was thoroughly washed with pure water and dried. Thereafter, the remaining film thickness of the polysilicon was measured in the same manner as described above to determine the polysilicon polishing rate [RR (poly-Si)] per minute.

From the obtained value, the selectivity between the silicon oxide film and the polysilicon was calculated from RR (SiO ₂ ) / RR (poly-Si).

Further, an evaluation wafer 3 in which silicon oxide (SiO ₂ ) having a film thickness of 1000 nm was formed on the entire surface of a silicon (Si) substrate having a diameter of 200 mm was prepared and polished for 60 seconds by the same method as described above. The polished evaluation wafer 3 was thoroughly washed with pure water, hydrofluoric acid, and aqueous ammonia, then dried, and the number of polishing flaws was counted with a scanning electron microscope type defect inspection apparatus. The relative number of polishing flaws was calculated with the number of polishing flaws of Comparative Example 4 being 1.

Table 1 summarizes the results of the above Examples and Comparative Examples.

As is apparent from Table 1, the polishing agents of Examples 1 to 6 containing cerium hydroxide and polyvinyl alcohol having a saponification degree of 95 mol% or less are excellent in the polishing rate of the silicon oxide film and the selectivity to polysilicon. Recognize. The comparative examples 1 and 4 which do not contain the polyvinyl alcohol are inferior in selectivity to polysilicon. As is clear from comparison with Comparative Example 4, the use of cerium hydroxide particles can greatly reduce polishing scratches.

Further, a graph in which the saponification degree of polyvinyl alcohol in each Example and Comparative Examples 2, 3, and 5 is plotted on the horizontal axis and the selectivity on the vertical axis is shown in FIG. From this figure, it can be read that the selectivity tends to increase as the saponification degree of polyvinyl alcohol decreases, and it can be seen that the saponification degree of polyvinyl alcohol is an important factor for the selectivity.

Industrial applicability

According to the present invention, in a CMP technique for planarizing an STI insulating film, a premetal insulating film, an interlayer insulating film, etc., an insulating film such as a silicon oxide film can be polished at high speed with low polishing scratches. An abrasive having a high polishing rate ratio, an abrasive set for storing the abrasive, and a method for polishing a substrate using the abrasive can be provided.

Claims (11)

1. An abrasive containing water, abrasive grains and additives,
   The abrasive grains contain tetravalent metal hydroxide particles,
   An abrasive in which at least one of the additives is polyvinyl alcohol having a saponification degree of 95 mol% or less.
2. The abrasive according to claim 1, wherein the abrasive has an average particle size of 1 nm to 400 nm.
3. The polishing agent according to claim 1 or 2, wherein the polishing agent has a pH of 3.0 or more and 12.0 or less.
4. The abrasive according to any one of claims 1 to 3, wherein a content of the abrasive grains is 0.01 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the abrasive.
5. The abrasive according to any one of claims 1 to 4, wherein a zeta potential of the abrasive grains in the abrasive is -20 mV or more and +20 mV or less.
6. The abrasive according to any one of claims 1 to 5, wherein a content of the polyvinyl alcohol is 0.01 parts by mass or more with respect to 100 parts by mass of the abrasive.
7. The abrasive according to any one of claims 1 to 6, which is used for polishing a surface to be polished containing at least silicon oxide on the surface.
8. The abrasive according to any one of claims 1 to 7, wherein the tetravalent metal hydroxide is at least one of a rare earth metal hydroxide and zirconium hydroxide.
9. A substrate on which a film to be polished is formed is pressed against a polishing pad of a polishing platen and pressurized, and the polishing agent according to any one of claims 1 to 8 is supplied between the film to be polished and the polishing pad, A substrate polishing method for polishing a film to be polished by relatively moving a polishing platen.
10. The method for polishing a substrate according to claim 9, wherein the Shore D hardness of the polishing pad is 70 or more.
11. 9. An abrasive set which is stored separately as a slurry and an additive solution and is mixed immediately before or during polishing to form the abrasive according to any one of claims 1 to 8, wherein the slurry contains abrasive grains and water. A polishing agent set containing an additive and water.

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