JP2018157164A - Polishing composition, manufacturing method thereof, polishing method and method for manufacturing semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition which enables polishing of a metal/an insulating film with a low selection ratio as to a polishing speed thereof while suppressing dissolution or corrosion of a metal such as cobalt.SOLUTION: A polishing composition comprises abrasive grains, an acid having the first acid dissociation constant (pKa1) of two or more or a salt thereof, a corrosion prevention agent, and a dispersant, which has an electric conductivity of 3 mS/cm or more and is pH6.5 or higher.SELECTED DRAWING: None

Description

  The present invention relates to a polishing composition, a method for producing a polishing composition, a polishing method, and a method for producing a semiconductor substrate.

  In recent years, a new fine processing technology has been developed along with the high integration and high performance of LSI (Large Scale Integration). Chemical mechanical polishing (hereinafter also simply referred to as CMP) is one of them, such as planarization of an interlayer insulating film, formation of a metal plug, embedded wiring (damascene wiring) in an LSI manufacturing process, particularly a multilayer wiring forming process. It is a technique that is frequently used in formation.

  A general method of CMP is to apply a polishing pad on a circular polishing platen (platen), immerse the polishing pad surface with an abrasive, press the surface on which the metal film of the substrate is formed, The polishing platen is rotated with pressure (polishing pressure) applied, and the metal film (for example, cobalt) is removed by mechanical friction between the abrasive and the metal film.

  In general, a metal plug or wiring in a semiconductor device is formed by forming a metal conductor layer as described above on a base layer made of an insulating film (for example, silicon dioxide) having recesses, and then forming the metal layer on the base layer. This is performed by removing a part of the conductive layer by polishing until the underlying layer is exposed.

  When using cobalt etc. as a metal for a metal plug or wiring, the polishing composition which can remove cobalt etc. and silicon dioxide is required. As a conventional polishing composition for removing cobalt, for example, Patent Document 1 discloses a cobalt chemical machine containing an inhibitor, an oxidizing agent, an abrasive, a complexing agent, and the balance of water, and having a pH value of 3 to 5. A polishing slurry is disclosed. Further, as a polishing composition for polishing an underlayer made of silicon dioxide, for example, Patent Document 2 contains abrasive grains and at least one of polyacrylic acid and a polyacrylic acid derivative, and has an electric conductivity of 2. Polishing composition which is 0 mS / cm or more is disclosed.

Special table 2014-509064 gazette JP, 2006-056292, A

  However, when polishing a semiconductor substrate in which both a metal such as cobalt and an insulating film such as silicon dioxide are exposed, the polishing for the insulating film such as silicon dioxide is performed when the slurry for chemical mechanical polishing as in Patent Document 1 is used. It was found that the speed was insufficient and the metal / insulating film polishing rate selectivity was high. In addition, when a polishing composition such as that of Patent Document 2 is used, a ground layer made of an insulating film such as silicon dioxide can be polished at a high polishing rate, but a problem such as dissolution or corrosion of a metal such as cobalt occurs. was there.

  Accordingly, the present invention is intended to solve such a problem, and provides a polishing composition capable of polishing a metal / insulating film at a low selectivity while suppressing dissolution and corrosion of a metal such as cobalt. The purpose is to do.

  Another object of the present invention is to provide a method for producing the polishing composition.

  Furthermore, this invention aims at providing the grinding | polishing method using the said polishing composition.

  As a result of intensive studies, the present inventors have found that the above problem can be solved by the following means, and have completed the present invention.

  That is, the present invention includes abrasive grains, an acid having a first acid dissociation constant (pKa1) of 2 or more, or a salt thereof, an anticorrosive, and a dispersion medium, and has an electrical conductivity of 3 mS / cm or more. And a polishing composition having a pH of 6.5 or more.

  Furthermore, this invention relates also to the manufacturing method of the said polishing composition.

  Furthermore, this invention relates also to the grinding | polishing method using the said polishing composition.

  Furthermore, the present invention relates to a method for manufacturing a semiconductor substrate using the polishing method.

  ADVANTAGE OF THE INVENTION According to this invention, the polishing composition which can grind | polish the grinding | polishing speed | rate of a metal / insulating film with a low selection ratio is provided, suppressing melt | dissolution and corrosion of metals, such as cobalt.

  Moreover, according to this invention, the manufacturing method of the said polishing composition is provided.

  Furthermore, according to the present invention, a polishing method using the polishing composition is provided.

  Furthermore, according to this invention, the manufacturing method of the semiconductor substrate using the said grinding | polishing method is provided.

  The present invention includes abrasive grains, an acid having a first acid dissociation constant (pKa1) of 2 or more, or a salt thereof, an anticorrosive, and a dispersion medium, and has an electrical conductivity of 3 mS / cm or more, and The polishing composition has a pH of 6.5 or higher. The polishing composition of the present invention having such a configuration can polish a metal / insulating film at a low selectivity while suppressing dissolution and corrosion of a metal such as cobalt.

  Further, in the present invention, polishing the metal / insulating film with a low selectivity means that the polishing speed of the metal contained in the polishing object and the polishing speed of the insulating film when polishing the polishing object. And the ratio is 1.8 or less, preferably 1.6 or less. When the metal / insulating film selection ratio is within the above range, the step shape of the object to be polished can be improved (step difference can be reduced). That is, the closer the polishing rate of the metal and the polishing rate of the insulating layer, the more advantageous for eliminating the step difference in the pattern.

  The mechanism for obtaining such an effect is considered as follows. However, the following mechanism is just a guess, and this does not limit the scope of the present invention.

  The polishing composition of the present invention contains an acid or a salt thereof, and has an electric conductivity of 3 mS / cm or more. By having an electric conductivity in such a range, the charge double layer of the abrasive grains is reduced. For example, when the object to be polished is silicon dioxide, the electrical repulsion between the abrasive grains and silicon dioxide is reduced. It is considered that the polishing rate is improved. On the other hand, since metals such as cobalt are easily ionized and dissolved in an acidic environment, the pH of the polishing composition is adjusted to 6.5 or more, so that the dissolution of the metal can be suppressed and the etching rate of the metal can be increased. Can be reduced. Furthermore, since the polishing composition of the present invention contains an anticorrosive agent, the metal etching rate can be reduced by covering the metal surface with the anticorrosion film. Furthermore, since an acid or salt thereof (so-called weak acid or salt thereof) having a first acid dissociation constant (pKa1) of 2 or more is used as the acid or salt thereof for adjusting electric conductivity, the metal surface Even if the anticorrosive film is peeled off, it is considered that the exposed metal is hardly corroded. Therefore, dissolution and corrosion of metals such as cobalt can be suppressed, and the etching rate and polishing rate of metals such as cobalt can be suppressed. As a result, when the polishing composition of the present invention is used, an insulating film such as silicon dioxide can be polished at a high polishing rate while suppressing the dissolution and corrosion of metals such as cobalt, and the metal / insulating film polishing rate can be selected low. Can be polished at a ratio. In addition, when the polishing composition of the present invention is used to polish a polishing object containing a metal-containing layer and silicon dioxide, for example, the step shape of the polishing object can be improved (step difference can be reduced). .

  Embodiments of the present invention will be described below. In addition, this invention is not limited only to the following embodiment.

  In the present specification, unless otherwise specified, measurement of operation and physical properties is performed under conditions of room temperature (20 to 25 ° C.) / Relative humidity 40 to 50% RH. In this specification, “X to Y” indicating a range includes X and Y, and means “X or more and Y or less”. Hereinafter, each structure of the polishing composition of this invention is demonstrated.

<Polishing object>
The polishing composition of the present invention is not particularly limited, but is suitably used for polishing a polishing object having a metal-containing layer. Examples of the metal include tungsten, copper, aluminum, hafnium, cobalt, nickel, titanium, tantalum, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium, and the like. These metals may be contained in the form of an alloy or a metal compound. Of these metals, cobalt, copper, tungsten, and aluminum are preferable, and cobalt is more preferable.

  The object to be polished may contain a material other than metal. Examples of materials other than metal include single crystal silicon, polycrystalline silicon (polysilicon, Poly-Si), amorphous silicon, silicon dioxide, silicon nitride, silicon carbide, and the like.

<Abrasive>
The polishing composition of the present invention contains abrasive grains. The abrasive grains contained in the polishing composition have an action of mechanically polishing the object to be polished.

  The abrasive used may be any of inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include particles made of metal oxides such as silica, alumina, ceria, titania, silicon nitride particles, silicon carbide particles, and boron nitride particles. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles. These abrasive grains may be used alone or in combination of two or more. The abrasive grains may be commercially available products or synthetic products.

  Among these abrasive grains, silica is preferable, and colloidal silica is particularly preferable.

  The abrasive grains may be surface-modified. Since ordinary colloidal silica has a zeta potential value close to zero under acidic conditions, silica particles are not electrically repelled with each other under acidic conditions and are likely to agglomerate. In contrast, abrasive grains whose surfaces are modified so that the zeta potential has a relatively large negative value even under acidic conditions are strongly repelled from each other and dispersed well even under acidic conditions. As a result, the storage stability of the polishing composition can be improved. That is, in the present invention, the abrasive grains are preferably colloidal silica having an anionic functional group on the surface. Such surface-modified abrasive grains can be obtained, for example, by mixing a metal such as aluminum, titanium or zirconium or an oxide thereof with the abrasive grains and doping the surface of the abrasive grains.

  Of these, colloidal silica having an organic acid immobilized thereon is more preferred, and colloidal silica having a sulfonic acid immobilized thereon is particularly preferred. The organic acid is immobilized on the surface of the colloidal silica contained in the polishing composition, for example, by chemically bonding the organic acid to the surface of the colloidal silica. If the colloidal silica and the organic acid are simply allowed to coexist, the organic acid is not fixed to the colloidal silica. For immobilizing sulfonic acid, which is a kind of organic acid, on colloidal silica, see, for example, “Sulphonic acid-functionalized silica through quantitative oxides of thiol groups”, Chem. Commun. 246-247 (2003). Specifically, a silane coupling agent having a thiol group such as 3-mercaptopropyltrimethoxysilane is coupled to colloidal silica, and then the sulfonic acid is immobilized on the surface by oxidizing the thiol group with hydrogen peroxide. The colloidal silica thus obtained can be obtained. Alternatively, if the carboxylic acid is immobilized on colloidal silica, for example, “Novel Silene Coupling Agents Containing a Photolabile 2-Nitrobenzoyl Ether for the Introducing the Carboxy Group” 229 (2000). Specifically, colloidal silica having a carboxylic acid immobilized on the surface can be obtained by irradiating light after coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to colloidal silica. .

  The average degree of association of the abrasive grains is also less than 5.0, more preferably 3.0 or less, and even more preferably 2.5 or less. As the average degree of association of the abrasive grains becomes smaller, the surface roughness due to the shape of the abrasive grains can be improved within such a range. The average degree of association of the abrasive grains is also preferably 1.0 or more, and more preferably 1.05 or more. This average degree of association is obtained by dividing the value of the average secondary particle diameter of the abrasive grains by the value of the average primary particle diameter. As the average degree of association of the abrasive grains increases, there is an advantageous effect that the polishing rate of the object to be polished by the polishing composition is improved.

  The lower limit of the average primary particle diameter of the abrasive grains is preferably 10 nm or more, more preferably 15 nm or more, and further preferably 20 nm or more. Further, the upper limit of the average primary particle diameter of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, and further preferably 100 nm or less. Within such a range, the polishing rate of the object to be polished by the polishing composition is further improved, and the occurrence of defects on the surface of the object to be polished after polishing with the polishing composition is further suppressed. be able to. In addition, the average primary particle diameter of an abrasive grain is calculated based on the specific surface area of the abrasive grain measured by BET method, for example.

  The lower limit of the average secondary particle diameter of the abrasive grains is preferably 15 nm or more, more preferably 20 nm or more, and further preferably 30 nm or more. Further, the upper limit of the average secondary particle diameter of the abrasive grains is preferably 300 nm or less, more preferably 260 nm or less, further preferably 220 nm or less, particularly preferably 150 nm, and 100 nm or less. It is particularly preferred that Within such a range, the polishing rate of the object to be polished by the polishing composition is further improved, and the occurrence of defects on the surface of the object to be polished after polishing with the polishing composition is further suppressed. be able to. The secondary particles referred to here are particles formed by association of abrasive grains in the polishing composition, and the average particle size (average secondary particle size) of the secondary particles is, for example, dynamic light It can be measured by a scattering method.

  The content of abrasive grains in the polishing composition according to the present invention is not particularly limited. The content of abrasive grains relative to the polishing composition is preferably 1% by mass or more, more preferably 2% by mass or more, and further preferably 3% by mass or more. As the content of abrasive grains increases, the polishing rate tends to be higher. Further, from the viewpoint of preventing scratches, the content of abrasive grains is usually suitably 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less. Reducing the content of abrasive grains is also preferable from the viewpoint of economy.

<Dispersion medium>
The polishing composition according to the present invention contains a dispersion medium in order to disperse or dissolve each component. A preferable example of the dispersion medium is water. It is preferable that water does not contain impurities as much as possible from the viewpoint of inhibiting the contamination of the object to be cleaned and the action of other components. As such water, for example, water having a total content of transition metal ions of 100 ppb or less is preferable. Here, the purity of water can be increased by operations such as removal of impurity ions using an ion exchange resin, removal of foreign matters by a filter, distillation, and the like. Specifically, as the water, for example, deionized water (ion exchange water), pure water, ultrapure water, distilled water, or the like is preferably used.

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

<Anticorrosive>
The polishing composition according to the present invention contains an anticorrosive agent. The anticorrosive agent has an action of suppressing the metal polishing rate and improving the step shape of the object to be polished by preventing dissolution and corrosion of the metal. In the present invention, usable anticorrosives are not particularly limited, but are preferably heterocyclic compounds or surfactants. The number of heterocyclic rings in the heterocyclic compound is not particularly limited. The heterocyclic compound may be a monocyclic compound or a polycyclic compound having a condensed ring. These metal anticorrosives may be used alone or in combination of two or more. In addition, as the metal anticorrosive, a commercially available product or a synthetic product may be used.

  Specific examples of heterocyclic compounds that can be used as anticorrosives include, for example, pyrrole compounds, pyrazole compounds, imidazole compounds, triazole compounds, tetrazole compounds, pyridine compounds, pyrazine compounds, pyridazine compounds, pyridine compounds, indolizine compounds, indole compounds. , Isoindole compound, indazole compound, purine compound, quinolidine compound, quinoline compound, isoquinoline compound, naphthyridine compound, phthalazine compound, quinoxaline compound, quinazoline compound, cinnoline compound, buteridine compound, thiazole compound, isothiazole compound, oxazole compound, isoxazole And nitrogen-containing heterocyclic compounds such as compounds and furazane compounds.

  More specific examples include pyrazole compounds such as 1H-pyrazole, 4-nitro-3-pyrazolecarboxylic acid, 3,5-pyrazolecarboxylic acid, 3-amino-5-phenylpyrazole, 5 -Amino-3-phenylpyrazole, 3,4,5-tribromopyrazole, 3-aminopyrazole, 3,5-dimethylpyrazole, 3,5-dimethyl-1-hydroxymethylpyrazole, 3-methylpyrazole, 1-methyl Examples include pyrazole, 3-amino-5-methylpyrazole, 4-amino-pyrazolo [3,4-d] pyrimidine, and allopurinol.

  Examples of imidazole compounds include, for example, imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, 1,2-dimethylpyrazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, benzimidazole, 5,6-dimethylbenzimidazole, 2-aminobenzimidazole, 2-chlorobenzimidazole, 2-methylbenzimidazole, 2- (1-hydroxyethyl) benzimidazole, 2-hydroxybenzimidazole, 2-phenylbenzimidazole, 2 , 5-dimethylbenzimidazole, 5-methylbenzimidazole, 5-nitrobenzimidazole and the like.

  Examples of triazole compounds include, for example, 1,2,3-triazole, 1,2,4-triazole, methyl-1H-1,2,4-triazole-3-carboxylate, 1H-1,2,4- Triazole-3-thiol, 3,5-diamino-1H-1,2,4-triazole, 3-amino-1,2,4-triazole-5-thiol, 3-amino-1H-1,2,4- Triazole, 3-amino-5-benzyl-4H-1,2,4-triazole, 3-amino-5-methyl-4H-1,2,4-triazole, 3-nitro-1,2,4-triazole, 4- (1,2,4-triazol-1-yl) phenol, 4-amino-1,2,4-triazole, 1H-benzotriazole, 1-hydroxybenzotriazole, 1-aminobenzo Riazole, 1-carboxybenzotriazole, 5-chloro-1H-benzotriazole, 5-nitro-1H-benzotriazole, 5-carboxy-1H-benzotriazole, 5-methyl-1H-benzotriazole, 5,6-dimethyl- 1H-benzotriazole, 1- (1 ′, 2′-dicarboxyethyl) benzotriazole, 1- [N, N-bis (hydroxyethyl) aminomethyl] benzotriazole, and the like can be given.

  Examples of the tetrazole compound include 1H-tetrazole, 5-methyltetrazole, 5-aminotetrazole, and 5-phenyltetrazole.

  Examples of indazole compounds include 1H-indazole, 5-amino-1H-indazole, 5-nitro-1H-indazole, 6-amino-1H-indazole, and the like.

  Examples of indole compounds include 1H-indole, 1-methyl-1H-indole, 2-methyl-1H-indole, 3-methyl-1H-indole, 4-methyl-1H-indole, 5-methyl-1H- Indole, 6-methyl-1H-indole, 7-methyl-1H-indole, 4-amino-1H-indole, 5-amino-1H-indole, 6-amino-1H-indole, 4-hydroxy-1H-indole, 5-hydroxy-1H-indole, 5-methoxy-1H-indole, 5-chloro-1H-indole, 5-carboxy-1H-indole, 4-nitro-1H-indole, 5-nitro-1H-indole, 1, 2-dimethyl-1H-indole, 2,3-dimethyl-1H-indole, 5- (aminomethyl) ) Indole, and 5-chloro-2-methyl -1H- indole and the like.

  Among these, azole compounds such as pyrazole compounds, imidazole compounds, triazole compounds, tetrazole compounds, indazole compounds, thiazole compounds, isothiazole compounds, oxazole compounds, isoxazole compounds are preferable, triazole compounds or tetrazole compounds are more preferable, 2,3-triazole, 1H-benzotriazole, and 1H-tetrazole are more preferable. Since these heterocyclic compounds have high chemical or physical adsorptive power to the surface of the object to be polished, a stronger anticorrosive film can be formed on the surface of the object to be polished. This is advantageous in improving the smoothness of the surface of the object to be polished after polishing with the polishing composition of the present invention.

  Examples of the surfactant used as the anticorrosive include a cationic surfactant, an anionic surfactant, an amphoteric surfactant, and a nonionic surfactant.

  Examples of anionic surfactants include, for example, polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfate, alkyl sulfate, polyoxyethylene alkyl ether sulfate, alkyl ether phosphate, alkyl ether sulfate, higher fatty acid, alkyl benzene Examples thereof include sulfonic acid, alkyl phosphate ester, polyoxyethylene alkyl phosphate ester, polyoxyethylene sulfosuccinic acid, alkyl sulfosuccinic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether disulfonic acid, and salts thereof.

  Examples of the cationic surfactant include alkyl trimethyl ammonium salt, alkyl dimethyl ammonium salt, alkyl benzyl dimethyl ammonium salt, alkyl amine salt and the like.

  Examples of amphoteric surfactants include alkyl betaines and alkyl amine oxides.

  Specific examples of nonionic surfactants include, for example, polyoxyalkylene alkyl ethers such as polyoxyethylene alkyl ether, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkyl amines, and alkyl alkanols. Amides are mentioned. Of these, polyoxyalkylene alkyl ether is preferred.

  Among these, anionic surfactants are preferable, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl phosphates, alkyl ether sulfates, alkyl ether phosphates, higher fatty acids, and salts thereof are more preferable, lauric acid, Lauryl sulfate ether, lauryl phosphate ether and their salts are particularly preferred. Since these surfactants have a high chemical or physical adsorption force to the surface of the object to be polished, it is possible to form a stronger anticorrosive film on the surface of the object to be polished. This is advantageous in improving the step shape of the object to be polished after polishing using the polishing composition of the present invention.

  The content (concentration) of the anticorrosive agent in the polishing composition is not particularly limited. For example, the lower limit of the content (concentration) of the anticorrosive is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, and further preferably 0.01% by mass or more. preferable. Further, the upper limit of the content (concentration) of the anticorrosive is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 2% by mass or less. If it is such a range, melt | dissolution and corrosion of a metal can be prevented, the metal grinding | polishing rate can be reduced, and the level | step difference shape of a grinding | polishing target object can be improved.

<Acid or its salt>
The polishing composition according to the present invention contains an acid having a first acid dissociation constant (pKa1) of 2 or more or a salt thereof. The acid or salt thereof is used to adjust electric conductivity, but by using an acid or salt thereof (so-called weak acid or salt thereof) having a first acid dissociation constant (pKa1) of 2 or more. It is thought that corrosion by metals such as cobalt can be suppressed. In the present specification, the “first acid dissociation constant (pKa1)” is also simply referred to as “first acid dissociation constant” or “pKa1”. The “acid or salt thereof having a first acid dissociation constant (pKa1) of 2 or more” is also simply referred to as “acid or salt thereof”.

In the present specification, the first acid dissociation constant (pKa1) is an index of acidity, and is obtained by taking the common logarithm of the reciprocal of the acid dissociation constant (Ka1). That is, the acid dissociation constant (pKa1) of the first acid is obtained by measuring the acid dissociation constant Ka = [H ₃ O ⁺ ] [B ⁻ ] / [BH] under dilute aqueous solution conditions, and calculating by pKa = −logKa1. It is done. In the above formula, BH represents an acid, and B ⁻ represents a conjugate base of the acid. The measuring method of pKa can be calculated from the concentration of the relevant substance and the hydrogen ion concentration by measuring the hydrogen ion concentration using a pH meter. The acid or salt thereof in the present invention may be used alone or in the form of a mixture of two or more. In addition, the 1st acid dissociation constant (pKa1) of an acid in the case of using an acid by 2 or more types can be measured by the said method.

  Here, the acid or salt thereof that can be used for the polishing composition is not particularly limited as long as the first acid dissociation constant (pKa1) is 2 or more, and may be an organic acid or an inorganic acid. From the viewpoint of ease of handling, the acid or salt thereof is at least one functional group selected from the group consisting of a carboxyl group or a salt group thereof, a phosphate group or a salt group thereof, and a carbonate group or a salt group thereof. A compound having a group is preferable.

  More specifically, the compound having a carboxyl group or a salt thereof includes citric acid, succinic acid, malonic acid, glutaric acid, adipic acid, tartaric acid, lactic acid, malic acid, acetic acid, carbonic acid, phosphoric acid, propionic acid. Phthalic acid, glycolic acid, crotonic acid, benzoic acid, butyric acid, n-hexanoic acid, 2-methylhexanoic acid, salicylic acid, pimelic acid, fumaric acid or salts thereof.

  Examples of the compound having a phosphoric acid group or a salt group thereof include phosphoric acid, polyphosphoric acid, metaphosphoric acid, derivatives of these compounds, and salts thereof.

  Examples of the compound having a carbonate group or a salt thereof include carbonic acid such as carbonic acid, potassium carbonate, sodium carbonate, or a salt thereof.

  Furthermore, specific examples of the acid or a salt thereof include, for example, ammonium formate, ammonium acetate, diammonium oxalate, ammonium hydrogen oxalate, ammonium benzoate, monoammonium citrate, diammonium citrate, triammonium citrate, and lactic acid. Ammonium, ammonium phthalate, ammonium succinate, monoammonium tartrate, diammonium tartrate, ammonium aspartate, ammonium carbonate, ammonium hydrogen carbonate, monoammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, etc. . These acids or salts thereof can be used alone or in combination of two or more.

  Of these acids or salts thereof, a compound having a carboxyl group or a salt group thereof is preferred, and the compound having a carboxyl group or a salt group thereof is selected from the group consisting of succinic acid, acetic acid, citric acid and salts thereof. At least one selected from the above is preferred. Such an acid or a salt thereof can more effectively suppress corrosion of the metal contained in the object to be polished during polishing.

  The content of the acid or the salt thereof in the polishing composition is not particularly limited as long as the electrical conductivity of the polishing composition is 3 mS / cm or more as described below. For example, the lower limit of the content of the acid or salt thereof is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further preferably 0.3% by mass or more. . Further, the upper limit of the content of the acid or salt thereof is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 2% by mass or less.

[Electric conductivity]
The electrical conductivity of the polishing composition according to the present invention is 3 mS / cm or more. When the electrical conductivity is high, the electrostatic repulsive force between the abrasive grains becomes small and the range covered by the electrostatic repulsive force becomes narrow, so that the abrasive grains are close to each other and the secondary particle diameter becomes large, and mechanical polishing is performed. It is thought that power increases. Therefore, the polishing rate of silicon dioxide can be increased. When the electrical conductivity is less than 3 mS / cm, the polishing rate of silicon dioxide is low. The electrical conductivity is preferably 4 mS / cm or more, more preferably 5 mS / cm or more. On the other hand, the upper limit value of electric conductivity is not particularly limited, but is preferably 20 mS / cm or less.

  The means for setting the electrical conductivity of the polishing composition to 3 mS / cm or more is not particularly limited, but the polishing composition contains an acid or salt thereof having a first acid dissociation constant (pKa1) of 2 or more ( Adding a so-called weak acid or a salt thereof). The use of the acid or a salt thereof is preferable because a metal such as cobalt can suppress corrosion due to the acid and at the same time the electrical conductivity of the polishing composition can be adjusted to 3 mS / cm or more.

  The electrical conductivity can be controlled by appropriately selecting the type and content of the acid or salt thereof. Moreover, this electrical conductivity can be measured by the method as described in an Example.

<Other ingredients>
The polishing composition according to the present invention can be used for a polishing composition such as an oxidizing agent, a complexing agent, a pH adjuster, an antiseptic, and an antifungal agent as long as the effects of the present invention are not significantly hindered. You may further contain a well-known additive as needed.

Oxidizing agents that can be included if necessary in the polishing composition include hydrogen peroxide, peracetic acid, percarbonate, urea peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, potassium monopersulfate and oxone, Halogenous acid such as chlorous acid (HClO ₂ ), bromous acid (HBrO ₂ ), iodic acid (HIO ₂ ) or salts thereof; chloric acid (HClO ₃ ), bromic acid (HBrO ₃ ), iodic acid ( HIO ₃ ) and other halogen acids or salts thereof; perchloric acid (HClO ₄ ), perbromate (HBrO ₄ ), periodate (HIO ₄ ), and other perhalogen acids or salts thereof; hypofluorite and Hypochlorous acid and its salts; Hypobromous acid; Hypohalous acid such as hypoiodous acid and its salts or salts thereof. These oxidizing agents can be used alone or in combination of two or more. Among these oxidizing agents, hydrogen peroxide, peracetic acid, percarbonate, and urea peroxide are preferable from the viewpoint of inhibiting corrosion on the metal film, and hydrogen peroxide is more preferable from the viewpoint that a good step shape can be obtained. .

  With respect to the polishing composition, the content of the oxidizing agent during use is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and 0.5% by mass or more. It is particularly preferred that Further, the content of the oxidizing agent during use is usually suitably 5% by mass or less, more preferably less than 1% by mass, and particularly preferably less than 0.5% by mass. When the content of the oxidizing agent is within the above range, excessive oxidation of the surface of the object to be polished is less likely to occur, and a polished surface with less surface roughness can be obtained.

  Examples of complexing agents that can be included in the polishing composition include aminocarboxylic acid complexing agents and organic phosphonic acid complexing agents. Examples of aminocarboxylic acid complexing agents include ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid, nitrilotriacetic acid sodium, nitrilotriacetic acid ammonium, hydroxyethylethylenediaminetriacetic acid, hydroxyethylethylenediamine sodium triacetate, diethylenetriamine Acetic acid, sodium diethylenetriaminepentaacetate, triethylenetetramine hexaacetic acid and sodium triethylenetetramine hexaacetate are included. Examples of organic phosphonic acid complexing agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylene Phosphonic 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-methyl Phosphononosuccinic acid is included. Of these, organic phosphonic acid complexing agents are more preferred. Of these, ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and diethylenetriaminepentaacetic acid are preferable. Particularly preferred complexing agents include ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid). Complexing agents can be used alone or in combination of two or more.

  In the case where the polishing composition contains a complexing agent, the content (concentration) of the complexing agent is not particularly limited. For example, the lower limit of the content (concentration) of the complexing agent is not particularly limited because the effect is exhibited even in a small amount, but is preferably 0.001% by mass or more, and 0.005% by mass or more. More preferably, it is more preferably 0.01% by mass or more. The upper limit of the content (concentration) of the complexing agent is preferably 2% by mass or less, more preferably 1.5% by mass or less, and further preferably 1% by mass or less. If it is such a range, the grinding | polishing speed | rate of a grinding | polishing target object will improve, and it is advantageous when improving the smoothness of the surface of a grinding | polishing target object after grind | polishing using a polishing composition.

  Examples of antiseptics and fungicides that can be included in the polishing composition include 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one. And the like, isothiazoline-based preservatives such as paraoxybenzoates, and phenoxyethanol. These preservatives and fungicides can be used alone or in combination of two or more.

[PH]
The polishing composition according to the present invention has a pH of 6.5 or more. When the pH is less than 6.5, the dissolution of the metal cannot be suppressed, and the etching rate of the metal becomes high. The pH is preferably 6.6 or more, more preferably 6.9 or more. When pH of polishing composition becomes high, it exists in the tendency for melt | dissolution of a metal to be suppressed. On the other hand, the pH of the polishing composition is preferably 12.0 or less, preferably 11.8 or less, from the viewpoint of preventing dissolution of the abrasive grains and suppressing a decrease in mechanical polishing action by the abrasive grains. Is more preferably 11.5 or less, and particularly preferably 11.0 or less.

  In addition, pH of polishing composition uses pH meter (For example, the glass electrode type hydrogen ion concentration indicator (model number: F-23) by Horiba, Ltd.), standard buffer solution (phthalate pH buffer) Three-point calibration using solution pH: 4.01 (25 ° C.), neutral phosphate pH buffer solution pH: 6.86 (25 ° C., carbonate pH buffer solution pH: 0.011 (25 ° C.)) After that, the glass electrode is put into the polishing composition, and it can be grasped by measuring the value after 2 minutes or more have passed and stabilized.

  The pH of the polishing composition according to the present invention can be adjusted by adding an appropriate amount of a pH adjusting agent if necessary. The pH adjuster may be either acid or alkali, and may be either an inorganic compound or an organic compound. A pH adjuster can be used individually or in mixture of 2 or more types.

  As the pH adjuster, known acids, bases, or salts thereof can be used. Specific examples of the acid include inorganic acids such as sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid and phosphoric acid; formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid , N-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycol Acids, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid and lactic acid and other carboxylic acids, and methanesulfonic acid, And organic acids such as organic sulfuric acid such as ethanesulfonic acid and isethionic acid.

  Specific examples of the base that can be used as the pH adjusting agent include alkali metal hydroxides or salts, Group 2 element hydroxides or salts, quaternary ammonium hydroxide or salts thereof, ammonia, amines, and the like. . Specific examples of the alkali metal include potassium and sodium. Specific examples of the salt include carbonate, hydrogen carbonate, sulfate, acetate, and the like. Among these bases, ammonia, ammonium salts, alkali metal hydroxides, alkali metal salts, quaternary ammonium hydroxide compounds, and amines are preferable. More preferably, ammonia, potassium compound, sodium hydroxide, quaternary ammonium hydroxide compound, ammonium hydrogen carbonate, ammonium carbonate, sodium hydrogen carbonate, and sodium carbonate are applied. Moreover, it is more preferable that the polishing composition contains a potassium compound as a base from the viewpoint of preventing metal contamination. Examples of the potassium compound include potassium hydroxide or salt, and specific examples include potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, potassium sulfate, potassium acetate, potassium chloride and the like.

  The addition amount of the pH adjusting agent is not particularly limited, and may be appropriately adjusted so that the polishing composition has a desired pH.

<Polishing composition>
As described above, the polishing composition according to the present invention is suitably used for polishing a polishing object having a metal-containing layer. The metal is preferably cobalt. The polishing composition according to the present invention is typically supplied to a polishing object in the form of a polishing liquid containing the polishing composition, and used for polishing the polishing object. The polishing composition according to the present invention may be used, for example, as a polishing liquid after being diluted (typically diluted with water), or may be used as a polishing liquid as it is. Good. That is, the concept of the polishing composition in the technology according to the present invention is used for polishing by being diluted with a polishing composition (working slurry) that is supplied to the polishing object and used for polishing the polishing object. Both concentrates (working slurry stock solutions) are included. The concentration ratio of the concentrated liquid can be, for example, about 2 to 100 times on a volume basis, and usually about 5 to 50 times is appropriate. However, content of each component in the said polishing composition points out content in the case of being used as polishing liquid as it is.

<Method for producing polishing composition>
In this invention, the manufacturing method which manufactures the said polishing composition is provided. The manufacturing method of the polishing composition which concerns on this invention is not specifically limited. For example, it can be obtained by stirring and mixing abrasive grains, water-soluble polymer, basic compound and other additives as required. The manufacturing method of the polishing composition by one Embodiment of this invention is a manufacturing method of polishing composition including mixing an abrasive grain, an acid or its salt, anticorrosive, and a dispersion medium. In addition, from the viewpoint of the storage stability of the oxidizer, the production includes a step of mixing abrasive grains and a basic compound in water to obtain a mixture, and a step of adding and mixing the oxidizer to the mixture immediately before polishing. The method is more preferred.

  Although the temperature at the time of mixing is not specifically limited, 10-40 degreeC is preferable and you may heat in order to raise a melt | dissolution rate. Further, the mixing time is not particularly limited as long as uniform mixing can be performed. As the stirring device, for example, a well-known mixing device such as a blade-type stirrer, an ultrasonic disperser, or a homomixer is used. The aspect which mixes these components is not specifically limited, For example, all the components may be mixed at once and may be mixed in the order set suitably.

<Polishing method>
As described above, the polishing composition of the present invention is suitably used for polishing a polishing object having a metal-containing layer. Therefore, this invention also provides the grinding | polishing method including grind | polishing the grinding | polishing target object which has a layer containing a metal using polishing composition. The polishing composition of the present invention is particularly preferably used in the step of polishing a polishing object having a layer containing cobalt. That is, this invention also provides the grinding | polishing method including grind | polishing the grinding | polishing target object which has a layer containing cobalt using polishing composition.

  In addition, the polishing composition according to the present invention can be used for polishing a polishing object, for example, in an embodiment including the following operations.

  That is, a working slurry containing the polishing composition according to the present invention is prepared. Next, the polishing composition is supplied to the object to be polished and polished by a conventional method. For example, a polishing object is set in a general polishing apparatus, and the polishing composition is supplied to the surface (polishing object surface) of the polishing object through a polishing pad of the polishing apparatus. Typically, while continuously supplying the polishing composition, the polishing pad is pressed against the surface of the object to be polished, and both are relatively moved (for example, rotated). The polishing of the object to be polished is completed through this polishing step.

  The polishing pad used in the polishing step is not particularly limited. For example, any of polyurethane foam type, non-woven fabric type, suede type, those containing abrasive grains, and those not containing abrasive grains may be used. Further, as the polishing apparatus, a double-side polishing apparatus that simultaneously polishes both surfaces of an object to be polished, or a single-side polishing apparatus that polishes only one surface of the object to be polished may be used.

As for polishing conditions, for example, the rotational speed of the polishing platen is preferably 10 to 500 rpm. The pressure (polishing pressure) applied to the substrate having the object to be polished is preferably 0.5 to 10 psi. The method of supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuously supplying with a pump or the like is employed. Although the supply amount is not limited, it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention.
<Semiconductor substrate manufacturing method>
The polishing composition of the present invention is suitably used for polishing a metal-containing layer (polishing object). Therefore, this invention also provides the grinding | polishing method which grind | polishes the grinding | polishing target object which has a layer containing a metal with the polishing composition of this invention. Moreover, this invention provides the manufacturing method of a board | substrate including the process of grind | polishing the layer (polishing target object) containing a metal with the said grinding | polishing method.

  The present invention will be described in further detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. Unless otherwise specified, “%” and “part” mean “% by mass” and “part by mass”, respectively. In the following examples, unless otherwise specified, the operation was performed under conditions of room temperature (25 ° C.) / Relative humidity 40 to 50% RH.

<Preparation of polishing composition>
(Preparation of polishing composition A1-A15, polishing composition C1-C9)
To the water as the solvent, the abrasive grains, acid (or salt thereof) and anticorrosive shown in Table 1 were added so as to have the contents shown in Table 1, and the pH was adjusted to 8 using 48% potassium hydroxide. Then, the kind and content of oxidizing agents shown in Table 1 were added and mixed by stirring to prepare each polishing composition (mixing temperature: about 25 ° C., mixing time: about 10 minutes).

  In Table 1, abrasive grain A is colloidal silica having a sulfonic acid group on the surface (sulfonic acid-modified colloidal silica, primary particle diameter 35 nm, average secondary particle diameter 70 nm), and abrasive grain B is anionic on the surface. Colloidal silica having no functional group (unmodified colloidal silica, primary particle diameter 35 nm, average secondary particle diameter 70 nm).

<Electrical conductivity of polishing composition>
The electrical conductivity after adjusting the polishing composition was measured with a desktop electrical conductivity meter (model number: DS-71, manufactured by Horiba, Ltd.).

<Polishing>
Using each polishing composition, the surface of the polishing object (test piece) was polished under the following conditions. In Examples 1 to 15 and Comparative Examples 1 to 9, a silicon wafer (200 mm, blanket wafer) in which a cobalt film having a thickness of 2000 mm or a TEOS film (silicon dioxide film) having a thickness of 10,000 mm was formed on the surface was used as a test piece. did. In Example 16, a silicon wafer (200 mm, blanket wafer) in which a copper film having a thickness of 10,000 mm or a TEOS film (silicon dioxide film) having a thickness of 10,000 mm was formed on the surface was used as a test piece.

  The polishing rate of cobalt and copper is measured by using a sheet resistance measuring instrument (model number: VR-120, manufactured by Kokusai Electric System Service Co., Ltd.) based on the DC 4 probe method. The difference in thickness was determined by dividing by the polishing time and entered in Table 2.

  The polishing rate of the TEOS layer is obtained by dividing the difference in thickness of the TEOS film before and after polishing measured by using an optical film thickness measuring instrument (model number: ASET-f5x manufactured by KLA-Tencor Corporation) by the polishing time. , Filled in Table 2. Note that the closer the polishing rate of cobalt or copper and the polishing rate of TEOS is, the more advantageous it is for eliminating the level difference between the patterns. Therefore, the ratio of the polishing rate of cobalt to the polishing rate of TEOS (Co / TEOS) or the polishing rate of copper The ratio of the TEOS to the polishing rate (Cu / TEOS) closer to 1 is a better result.

(Polishing conditions)
Polishing machine: Single-side CMP polishing machine for 200mm wafers (Mirra, manufactured by Applied Materials)
Polishing pressure: 2 psi
Pad: Hard polyurethane pad IC1010 pad (Dow Chemical Co.)
Rotating speed of polishing surface plate: 93rpm
Carrier rotation speed: 87rpm
Supply of polishing composition: pouring Supply amount of polishing composition: 200 mL / min
Polishing time: 60 seconds <Cobalt or copper etching rate>
A coupon obtained by cutting a cobalt blanket wafer or a copper blanket wafer into 30 × 30 mm chips was immersed in a polishing composition for 10 minutes at 40 ° C., and the film thickness before and after immersion was determined. The film thickness before and after immersion was measured using a sheet resistance measuring instrument (model number: VR-120 manufactured by Kokusai Electric System Service Co., Ltd.), and the difference in film thickness before and after immersion was defined as the etching rate of cobalt or copper. Specifically, it can be said that the lower the value is, the more preferable the result is because the dissolution assumed to occur during the polishing of cobalt or copper is suppressed. The results are entered in Table 2.

<Anode current measurement by electrochemistry (chronoamperometry)>
200 mL of each polishing composition shown in Table 1 was prepared and used as a sample for electrochemical measurement (chronoamperometry). The reference electrode, the working electrode, and the counter electrode were immersed in the polishing composition, and the maximum value of the current that flowed when a certain voltage was applied to cobalt or copper as the working electrode was measured under the following conditions.

Electrochemical measuring device: Solartron potentiostat Model: 1280Z
Reference electrode: Silver-silver chloride electrode Working electrode: Cobalt or copper Counter electrode: Platinum Applied voltage: 1V
Voltage application time: 30 seconds Test temperature: 25 ° C
Stirrer rotation speed: 300rpm
Specifically, the smaller the current after 1 V is applied, the more the corrosion of cobalt or copper is suppressed. The results are entered in Table 2.

○: Less than 10 ⁻³ A / cm ² Δ: 10 ⁻³ A / cm ² or more, less than 10 ⁻² A / cm ² ×: 10 ⁻² A / cm ² or more.

<Colloidal stability>
The polishing composition shown in Table 1 was stored at 80 ° C. for 1 week, and the average secondary particle diameter of the abrasive grains before and after storage was measured. The average secondary particle diameter was measured as a volume average particle diameter (volume-based arithmetic average diameter; Mv) using a dynamic light scattering particle diameter / particle size distribution device (manufactured by Nikkiso Co., Ltd., model number: (UPA-UT151)). Specifically, the smaller the amount of change in the average secondary particle diameter before and after storage, the better the storage stability, and the better the results. did.

○: Change amount of average secondary particle size before and after storage is less than 10 nm Δ: 10 nm or more and less than 12 nm ×: 12 nm or more

  As shown in Table 2, according to the polishing compositions of the present invention in Examples 1 to 15, the cobalt etching rate is low, the current after 1V is applied is small, and the cobalt is dissolved and corroded. It can be seen that TEOS can be polished at a high polishing rate, and the selection ratio of cobalt / TEOS was close to 1. In Example 16, even when copper was used by changing the type of metal, the copper etching rate was low, indicating that the current after 1V was applied was small, and that it was effective for polishing copper. I can say that.

  On the other hand, since the anticorrosive agent was not used in Comparative Example 1, dissolution of cobalt was observed. In Comparative Example 2, an acid having a pKa of 2 or more or a salt thereof was not used, and the electrical conductivity was less than 3 mS / cm. Therefore, the selection ratio of cobalt / TEOS was high. In Comparative Example 3, since the electric conductivity was less than 3 mS / cm, the selection ratio of cobalt / TEOS was high. In Comparative Examples 4 to 6, since a strong acid salt having a pKa of less than 2 was used, corrosion of cobalt proceeded. In Comparative Examples 7 to 9, since the pH was less than 7.5, cobalt was dissolved, and the etching rate of cobalt was increased.

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

  According to the polishing composition of the present invention, it is possible to polish the metal / insulating film at a low selectivity while suppressing the dissolution and corrosion of metals such as cobalt.

Claims (13)

Abrasive grains,
An acid or salt thereof having a first acid dissociation constant (pKa1) of 2 or more;
Anticorrosive,
A dispersion medium,
A polishing composition having an electric conductivity of 3 mS / cm or more and a pH of 6.5 or more.   The acid or a salt thereof is a compound having at least one functional group selected from the group consisting of a carboxyl group or a salt group, a phosphoric acid group or a salt group thereof, and a carbonate group or a salt group thereof. The polishing composition according to claim 1.   The polishing composition according to claim 1, wherein the acid or a salt thereof is a compound having a carboxyl group or a salt group thereof.   The polishing composition according to claim 2 or 3, wherein the compound having a carboxyl group or a salt thereof is at least one selected from the group consisting of succinic acid, acetic acid, citric acid, and salts thereof.   The polishing composition according to any one of claims 1 to 4, wherein the anticorrosive is an azole compound or an anionic surfactant.   The polishing composition according to claim 5, wherein the azole compound is a triazole compound or a tetrazole compound.   The polishing composition according to any one of claims 1 to 6, wherein the abrasive grains are colloidal silica having an anionic functional group on the surface.   The polishing composition according to any one of claims 1 to 7, which is used for polishing a polishing object having a layer containing a metal.   The polishing composition according to claim 8, wherein the metal is cobalt.   The manufacturing method of the polishing composition of any one of Claims 1-9 including the process of mixing the said abrasive grain, the said acid or its salt, the said anticorrosive, and the said dispersion medium.   The grinding | polishing method including the process of grind | polishing the grinding | polishing target object which has a layer containing a metal using the polishing composition of any one of Claims 1-10.   The polishing method according to claim 11, wherein the metal is cobalt. The manufacturing method of a semiconductor substrate including the process of grind | polishing the semiconductor substrate which has a layer containing a metal on the surface with the grinding | polishing method of Claim 11.