JP2010080864A - Polishing liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing liquid that employs a solid grain for use in chemical mechanical polishing in a planarization process of a semiconductor integrated circuit, and that inhibits an organic residue from adhering to a surface to be polished of an insulating film with low strength, such as a Low-k film, after the chemical mechanical polishing, even when using a substrate that has an insulating layer in which a usual TEOS insulating film and a Low-k film with a low dielectric constant are laminated as a body to be polished, and prevents scratches caused by cohesion of solid grain or the like. <P>SOLUTION: The polishing liquid is employed for chemical mechanical polishing of a barrier layer and/or an interlayer insulating film during a process of manufacturing a semiconductor integrated circuit. The polishing liquid includes quaternary ammonium salt, a corrosion inhibitor, an organic acid containing at least one nitrogen atom and two or more carboxyl groups, and an inorganic particle, and has a pH of 1 to 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polishing liquid used in a semiconductor device manufacturing process, and more particularly, to a polishing liquid used for chemical mechanical polishing for the purpose of planarization in a wiring process of a semiconductor device.

  In the development of semiconductor devices typified by semiconductor integrated circuits (hereinafter also referred to as LSIs), in recent years, there has been a demand for higher density and higher integration by miniaturization and lamination of wiring in order to reduce size and speed. Yes. For this purpose, various techniques such as chemical mechanical polishing (hereinafter also referred to as CMP) have been used. This CMP is an indispensable technique when performing surface planarization of a film to be processed such as an interlayer insulating film, plug formation, formation of embedded metal wiring, and the like. By this CMP, the substrate is smoothed, the excess metal thin film is removed during wiring formation, and the excess barrier layer on the insulating film is removed.

A general method of CMP is to apply a polishing pad on a circular polishing platen (platen), immerse the surface of the polishing pad with a polishing liquid, press the surface of the substrate (wafer) against the pad, In a state where pressure (polishing pressure) is applied, both the polishing platen and the substrate are rotated, and the surface of the substrate is flattened by the generated mechanical friction.
When manufacturing a semiconductor device such as an LSI, fine wiring is formed in multiple layers. When forming a metal wiring such as Cu in each layer, a barrier metal such as Ta, TaN, Ti, or TiN is used for the purpose of preventing the diffusion of the wiring material into the interlayer insulating film and improving the adhesion of the wiring material. Is formed in advance.

In order to form each wiring layer, first, CMP of a metal film (hereinafter, also referred to as metal film CMP) for removing excess wiring material stacked by plating or the like is performed in one or more stages. Next, CMP (hereinafter also referred to as “barrier metal CMP”) for removing the barrier metal material (barrier metal) exposed on the surface is generally performed.
However, since the barrier metal material is usually a material harder than the metal material for wiring such as copper wiring, in CMP, the soft wiring metal film is overpolished and the polished metal surface is not flat, but only in the center. (Dashing) where the surface of the metal wiring is polished more than necessary, and the surface of multiple metal surfaces forms dish-shaped recesses (erosion) ) Is a problem.

  In order to reduce this dishing and erosion, in the barrier metal CMP performed after the metal film CMP, the polishing rate of the metal wiring part and the polishing rate of the barrier metal part are adjusted, and finally there are steps such as dishing and erosion. There is a demand for forming a small number of wiring layers. That is, in the barrier metal CMP, when the polishing rate of the barrier metal or the interlayer insulating film is relatively small as compared with the metal wiring material, the wiring part is polished faster, and dishing or erosion occurs. In order to prevent this, it is desirable that the polishing rate of the barrier metal or the interlayer insulating film is appropriately high. The dishing described above often occurs in the metal film CMP. In the barrier metal CMP, the polishing rate of the barrier metal or the interlayer insulating film is made higher than the polishing rate of the metal wiring material. It is possible to reduce dishing. Note that such a high polishing rate also leads to an advantage of increasing the throughput of the barrier metal CMP.

Moreover, the metal polishing solution used for CMP generally contains abrasive grains (for example, alumina, silica) and an oxidizing agent (for example, hydrogen peroxide, persulfuric acid). As a basic polishing mechanism, it is considered that polishing is performed by first oxidizing a metal surface with an oxidizing agent and removing the oxide film with abrasive grains.
When CMP is performed using a polishing liquid containing such solid abrasive grains, a large number of scratches (scratches) are generated along with the above-described phenomenon that the entire polished surface is polished more than necessary (thinning), dishing, and erosion. was there. Furthermore, there is a problem in that the residue of each layer (also referred to as organic residue) generated during CMP adheres to the polished surface to form a concavo-convex portion and the flatness is impaired.

The following various studies have been made on the polishing liquid containing such solid abrasive grains.
For example, a CMP abrasive and a polishing method (Patent Document 1) intended to perform high-speed polishing with almost no polishing scratches (Patent Document 1), a polishing composition and a polishing method (Patent Document 2) with improved cleaning performance in CMP, In addition, a polishing composition (Patent Document 3) that prevents aggregation of abrasive grains has been proposed.

However, even these polishing liquids are not necessarily satisfactory in terms of coexistence of suppression of the amount of organic residue adhering to the polishing surface and suppression of scratches caused by aggregation of solid abrasive grains. Instead, further improvements were needed.
In particular, in recent years, with the further miniaturization of wiring, a low dielectric constant material having a lower relative dielectric constant than a generally used interlayer insulating film such as TEOS (tetraethoxysilane) is used as an insulating film. It has become. These insulating films are referred to as low-k films. For example, there are films made of organic polymer, SiOC, or SiOF materials, which are generally used by being laminated with an insulating film such as TEOS. Since these low-k films have lower strength than conventional insulating films, problems of organic residue and scratches have become more prominent in the CMP process.

JP 2003-17444 A JP 2003-142435 A JP 2000-84832 A

  Accordingly, in view of the above circumstances, the present invention is a polishing liquid using solid abrasive grains used for chemical mechanical polishing in a planarization process of a semiconductor integrated circuit, and is a normal TEOS insulating film as an object to be polished. Even when a substrate having an insulating film in which a low-k low-k film is laminated, an organic residue on the polished surface after CMP is applied to an insulating film having a low strength such as a low-k film. An object of the present invention is to provide a polishing liquid in which adhesion is suppressed and generation of scratches due to aggregation of solid abrasive grains is suppressed.

  As a result of intensive studies on the above problems, the present inventor has found that the above problems can be solved by using the following polishing liquid, and has achieved the object.

<1> A polishing liquid used for chemical mechanical polishing of a barrier layer and / or an interlayer insulating film in a manufacturing process of a semiconductor integrated circuit, comprising a quaternary ammonium salt, a corrosion inhibitor, at least one nitrogen atom, A polishing liquid comprising an organic acid containing two or more carboxyl groups, and inorganic particles, and having a pH of 1 to 7.
<2> The polishing liquid according to <1>, wherein the quaternary ammonium salt is a compound represented by the general formula (1) or the general formula (2).

(In General Formula (1), R ^{1 to} R ⁴ each independently represents an alkyl group, alkenyl group, cycloalkyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms. X ⁻ represents a monovalent group. It represents an anion. in addition, any two of R ¹ to R ^4, may form a cyclic structure bonded to each other.
In General Formula (2), R ^{5 to} R ¹⁰ each independently represent an alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, or an aralkyl group. M represents an alkylene group having 1 to 20 carbon atoms, an alkenylene group, a cycloalkylene group, an arylene group, or a group obtained by combining two or more thereof. X ⁻ represents a monovalent anion, and Y ²⁻ represents a divalent anion. Note that any two of R ^{5 to} R ¹⁰ may be bonded to each other to form a cyclic structure. )
<3> The polishing liquid according to <1> or <2>, wherein the inorganic particles are at least one inorganic particle selected from the group consisting of silica, alumina, ceria, zirconia, and titania.
<4> The polishing liquid according to any one of <1> to <3>, wherein the content of the inorganic particles in the polishing liquid is 0.5 to 15% by mass with respect to the total mass of the polishing liquid.
<5> The object to be polished is a metal layer made of at least one metal selected from the group consisting of Ta, TaN, Ti, TiN, Ru, CuMn, MnO ₂ , WN, W, and Co. <1> to <4> The polishing liquid according to any one of the above.

  According to the present invention, a polishing liquid using solid abrasive grains used for chemical mechanical polishing in a planarization process of a semiconductor integrated circuit, which is a normal TEOS insulating film and a low dielectric constant Low as an object to be polished. Even when a substrate having an insulating film laminated with a -k film is used, adhesion of organic residue on the polished surface after CMP is suppressed even for an insulating film with low strength such as a low-k film, Furthermore, it is possible to provide a polishing liquid in which generation of scratches due to aggregation of solid abrasive grains is suppressed.

Hereinafter, specific embodiments of the present invention will be described.
A polishing liquid according to the present invention is a polishing liquid used for chemical mechanical polishing of a barrier layer or an interlayer insulating film of a semiconductor integrated circuit, and includes a quaternary ammonium salt, a corrosion inhibitor, at least one nitrogen atom and two. It contains an organic acid containing at least one carboxyl group and inorganic particles, has a pH of 1 to 7, and may contain optional components as necessary.
Each component contained in the polishing liquid of the present invention may be used alone or in combination of two or more.

In the present invention, the “polishing liquid” means not only a polishing liquid used for polishing (that is, a polishing liquid diluted as necessary) but also a concentrated liquid of the polishing liquid. The concentrated liquid or the concentrated polishing liquid means a polishing liquid prepared with a higher solute concentration than the polishing liquid used for polishing, and is diluted with water or an aqueous solution when used for polishing. And used for polishing. The dilution factor is generally 1 to 20 volume times. In this specification, “concentration” and “concentrated liquid” are used in accordance with conventional expressions meaning “thick” and “thick liquid” rather than the state of use, and are generally accompanied by physical concentration operations such as evaporation. The term is used in a different way from the meaning of common terms.
Hereinafter, each component which comprises the polishing liquid of this invention is demonstrated in detail.

<Quaternary ammonium salt>
The polishing liquid of the present invention contains a quaternary ammonium salt (hereinafter also referred to as “specific cation salt”).
The quaternary ammonium salt in the present invention is not particularly limited as long as it contains a quaternary nitrogen in the molecular structure, but it is preferably a structure containing one or two quaternary nitrogens in the molecular structure. Especially, it is more preferable that it is a compound represented by General formula (1) or General formula (2) from a viewpoint of achieving the low amount of organic residue and a low scratch.

(In General Formula (1), R ^{1 to} R ⁴ each independently represents an alkyl group, alkenyl group, cycloalkyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms. X ⁻ is a monovalent group. It represents an anion. in addition, any two of R ¹ to R ^4, may form a cyclic structure bonded to each other.
In General Formula (2), R ^{5 to} R ¹⁰ each independently represent an alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, or an aralkyl group. M represents an alkylene group having 1 to 20 carbon atoms, an alkenylene group, a cycloalkylene group, an arylene group, or a group obtained by combining two or more thereof. X ⁻ represents a monovalent anion, and Y ²⁻ represents a divalent anion. Note that any two of R ^{5 to} R ¹⁰ may be bonded to each other to form a cyclic structure. )

In General Formula (1), R ^{1 to} R ⁴ each independently represents an alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, or an aralkyl group.
As a C1-C20 alkyl group, a C1-C10 alkyl group is more preferable, and a C1-C8 alkyl group is further more preferable. Specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group. Among them, a methyl group, an ethyl group, a propyl group, and a butyl group are preferable.
The alkenyl group preferably has 2 to 10 carbon atoms, and specific examples include ethynyl group and propyl group.
The cycloalkyl group preferably has 3 to 8 carbon atoms, and specifically includes a cyclohexyl group, a cyclopentyl group, etc. Among them, a cyclohexyl group is preferable.
As an aryl group, C6-C12 is preferable and a phenyl group, a naphthyl group, etc. are mentioned specifically, A phenyl group is preferable especially.
The aralkyl group preferably has 7 to 10 carbon atoms, and specifically includes a benzyl group.
Any two of R ^{1 to} R ⁴ may be bonded to each other to form a cyclic structure. Although it does not restrict | limit especially as a cyclic structure, The 5-7 membered ring structure containing the nitrogen atom in General formula (1) is preferable.

Each group represented by R ^{1 to} R ⁴ may further have a substituent. Examples of the substituent that can be introduced include a hydroxyl group, an amino group, a carboxyl group, a heterocyclic group, a pyridinium group, an aminoalkyl group, a phosphate group, an imino group, a thiol group, a sulfo group, and a nitro group.

In the general formula (1), X ^- represents a monovalent anion. Specifically, hydroxide ion, halide ion (fluorine ion, chlorine ion, bromine ion, iodine ion), nitrate ion, hydrocarbon ion, nitrite ion, acetate ion, glycolate ion, trifluoroacetate ion, Examples thereof include p-toluenesulfonic acid ion, benzenesulfonic acid ion, methanesulfonic acid ion, trifluoromethanesulfonic acid ion, ethanesulfonic acid ion, and 2-tetrahydrofurancarboxylic acid ion.

  Examples of the quaternary ammonium salt represented by the general formula (1) include, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraisopropylammonium hydroxide, tetracyclopropylammonium hydroxide, water Tetrabutylammonium oxide, tetraisobutylammonium hydroxide, tetra-tert-butylammonium hydroxide, tetra-sec-butylammonium hydroxide, tetracyclobutylammonium hydroxide, tetrapentylammonium hydroxide, tetracyclopentylammonium hydroxide, hydroxylation Examples include tetrahexyl ammonium and tetracyclohexyl ammonium hydroxide. The counter anions of these exemplary compounds are not limited to hydroxide ions, but may be chlorine ions or bromine ions.

In General Formula (2), R ^{5 to} R ¹⁰ each independently represent an alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, or an aralkyl group. Each group represented by R ^{5 to} R ¹⁰ is synonymous with each group represented by R ^{1 to} R ⁴ in the general formula (1), and the preferred range is also the same.
Note that any two of R ^{5 to} R ¹⁰ may be bonded to each other to form a cyclic structure. Although it does not restrict | limit especially as a cyclic structure, For example, the 5-7 membered ring structure containing the two nitrogen atoms in General formula (2) is preferable.

In the general formula (2), X ^- represents a monovalent anion, in general formula (1) X ^- as synonymous. Y ^2- represents a divalent anion. Examples of Y ^2- include oxalate ion, phthalate ion, maleate ion, fumarate ion, tartaric acid ion, malate ion, lactate ion, sulfate ion, diglycolate ion, and 2,5-furandicarboxylate ion. Etc.

In General Formula (2), M represents an alkylene group having 1 to 20 carbon atoms, an alkenylene group, a cycloalkylene group, an arylene group, or a group obtained by combining two or more of these. In addition to the organic linking group described above, the linking group represented by M includes —S—, —S (═O) ₂ —, —O—, —C (═O) — in the chain. May be included.
The alkylene group having 1 to 20 carbon atoms is more preferably an alkylene group having 1 to 10 carbon atoms. Specific examples include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, and an octylene group. Among them, an ethylene group and a pentylene group are preferable.
As an alkenylene group, C1-C20 is preferable. Specific examples include an ethynylene group and a propynylene group. Among them, a propynylene group is preferable.
As a cycloalkylene group, C3-C8 is preferable. Specific examples include a cyclohexylene group and a cyclopentylene group. Among them, a cyclohexylene group is preferable.
As an arylene group, C6-C10 is preferable. Specific examples include a phenylene group and a naphthylene group, and among them, a phenylene group is preferable.

  Each linking group represented by M may further have a substituent. Examples of the substituent that can be introduced include a hydroxyl group, an amino group, a sulfonyl group, a carboxyl group, a heterocyclic group, a pyridinium group, an aminoalkyl group, a phosphate group, an imino group, a thiol group, a sulfo group, and a nitro group.

  Hereinafter, although the specific example [Exemplary compound (A-1)-(A-32)] of the cation part (it is also called a specific cation) of the quaternary ammonium salt in this invention is shown, this invention is limited to these. is not.

  Among the cation parts (specific cations) of the quaternary ammonium salt as described above, A8, A10, A11, and A12 are preferable from the viewpoint of dispersion stability in the polishing liquid.

  The quaternary ammonium salt in the present invention can be synthesized, for example, by a substitution reaction in which ammonia, various amines and the like serve as a nucleophile. Moreover, the purchase as a general sale reagent is also possible.

  The content of the quaternary ammonium salt in the polishing liquid of the present invention is not particularly limited, but refers to the diluted polishing liquid when used for polishing (that is, when diluted with water or an aqueous solution). The following “polishing liquid for use in polishing” is also agreed.) Is preferably 0.0001 to 1.0% by mass, more preferably 0.001 to 0.3% by mass. The content of the quaternary ammonium salt is preferably 0.0001% by mass or more from the viewpoint of sufficiently improving the amount of low organic residue and low scratch, and 1.0% by mass or less from the viewpoint of sufficient slurry stability. Is preferred.

<Corrosion inhibitor>
The polishing liquid of the present invention contains a corrosion inhibitor that adsorbs to the surface to be polished to form a film and controls the corrosion of the metal surface. As the corrosion inhibitor in the present invention, a heteroaromatic ring compound having 3 or more nitrogen atoms in the molecule and having a condensed ring structure is preferable. Here, “three or more nitrogen atoms” are preferably atoms constituting a condensed ring. The heteroaromatic ring compound may have a functional group such as a carboxyl group, a sulfo group, a hydroxy group, or an alkoxy group.
Examples of such heteroaromatic ring compounds include imidazoles, triazoles, tetrazoles, and benzotriazoles. Among them, benzotriazoles and derivatives obtained by introducing various substituents into benzotriazole are more preferable. .

Examples of the corrosion inhibitor that can be used in the present invention include 1,2,3-benzotriazole, 5,4-dimethyl-1,2,3-benzotriazole, and 1- (1,2-dicarboxyethyl) benzotriazole. 1- [N, N-bis (hydroxyethyl) aminomethyl] benzotriazole, 1- (hydroxymethyl) benzotriazole, tolyltriazole, 1- (1,2-dicarboxyethyl) tolyltriazole, 1- [N, N-bis (hydroxyethyl) aminomethyl] tolyltriazole, 1- (2,3-dihydroxypropyl) benzotriazole, 1- (2,3-dihydroxypropyl) tolyltriazole, 1- (hydroxymethyl) benzotriazole, tetrazole, 5-aminotetrazole, tetrazole-5-acetic acid, 5-methyl Rutetrazole, 5-phenyltetrazole, 3-amino-1,2,4-triazole, 3-nitro-1,2,4-triazole, 1,2,3-triazole-4-acetic acid, 1,2,3- Examples include triazole-4,5-diacetic acid, 1-aminobenzotriazole, 1-hydroxybenzotriazole, 5-aminobenzotriazole, 1,2,4-triazole, 1,2,3-triazole and the like.
Among them, 1,2,3-benzotriazole, tetrazole, 5-aminotetrazole, tetrazole-5-acetic acid, 5-methyltetrazole, 5-phenyltetrazole, 3-amino-1,2,4-triazole, 3-nitro- 1,2,4-triazole, 1,2,3-triazole-4-acetic acid, 1,2,3-triazole-4,5-diacetic acid, 1-aminobenzotriazole, 1-hydroxybenzotriazole, 5-amino More preferably, it is selected from benzotriazole, tolyltriazole, 1,2,3-triazole, and 1,2,4-triazole.

  The content of the corrosion inhibitor in the polishing liquid of the present invention is preferably 0.001 to 0.2% by mass, and 0.05 to 0.2% by mass with respect to the total mass of the polishing liquid when used for polishing. % Is more preferable. That is, the content of such a corrosion inhibitor is preferably 0.001% by mass or more from the viewpoint of not expanding dishing, and is preferably 0.2% by mass or less from the viewpoint of storage stability.

<Organic acid>
The polishing liquid of the present invention contains an organic acid containing at least one nitrogen atom and two or more carboxyl groups (hereinafter also simply referred to as an organic acid). The number of nitrogen atoms contained in the organic acid is at least one, preferably 1 to 3. Moreover, the number of the carboxyl group contained in this organic acid is 2 or more, Preferably it is 2-4. Especially, it is more preferable that it is two from a viewpoint which can be used cheaply.

  Examples of such organic acids include aminomalonic acid, N-carboxyglycine, 2-aminosuccinic acid, iminodiacetic acid, 2-methylaminosuccinic acid, glutamic acid, 3-aminopentanediacetic acid, 2-amino-3- Methylsuccinic acid, 2-amino-2-methylsuccinic acid, 2,3-diaminosuccinic acid, carboxymethylhydrazinoacetic acid, 2-amino-3-hydroxysuccinic acid, methyleneglutamic acid, methylglutamic acid, 2-aminoadipic acid, 3- Aminoadipic acid, 4-methylglutamic acid, 2-methylglutamic acid, 2,4-diaminoglutaric acid, ethylenediaminediacetic acid, 2-hydroxymethyliminodiacetic acid, 2-acetylaminopentanediacetic acid, acetylglutamic acid, diaminopimeric acid, 1,3-diaminopropanediacetic acid, nito B triacetate or mixtures thereof, and the like. Of these, compounds having two or more carboxyl groups are preferred.

  Examples of the organic acid used in the present invention include compounds represented by the following structural formulas (organic acids B-1 to B-28).

  The content of the organic acid containing at least one nitrogen atom and two or more carboxyl groups in the polishing liquid of the present invention is 0.01 to 5. with respect to the total mass of the polishing liquid when used for polishing. 0 mass% is preferable and 0.05-2.0 mass% is more preferable. That is, the content of such an organic acid is preferably 0.01% by mass or more from the viewpoint of achieving a low organic residue amount and low scratch, and is preferably 5.0% by mass or less from the point of not causing excessive dishing.

<Inorganic particles>
The polishing liquid of the present invention contains inorganic particles.
The inorganic particles used in the present invention are those used as abrasive particles (solid abrasive grains), such as silica (precipitated silica, fumed silica, colloidal silica, synthetic silica), alumina, ceria, zirconia, titania, germania. , Manganese oxide, silicon carbide, and the like. Among these, silica, alumina, ceria, zirconia, and titania are preferable. In particular, silica is preferable, and colloidal silica is more preferable.

  The colloidal silica is preferably colloidal silica that does not contain impurities such as alkali metals inside the particles and is obtained by hydrolysis of alkoxysilane. On the other hand, colloidal silica produced by a method of removing an alkali metal from an aqueous alkali silicate solution can also be used. In this case, there is a concern that the alkali metal remaining in the particles gradually elutes and affects the polishing performance. From such a viewpoint, those obtained by hydrolysis of alkoxysilane are more preferable as raw materials. In addition, a commercial item may be used for colloidal silica.

  The size (particle size) of the inorganic particles is not particularly limited as long as the object of the present invention is not impaired, but is preferably 5 to 200 nm, more preferably 10 to 100 nm, and further preferably 20 to 70 nm. If it is in the said range, suppression of an organic substance residue and a low scratch number can be made to make compatible both in a more balanced manner.

  The content of inorganic particles in the polishing liquid of the present invention is preferably 0.5 to 15.0% by mass, and preferably 3.0 to 12.0% by mass with respect to the total mass of the polishing liquid when used for polishing. Is more preferable, and 5.0-12.0 mass% is further more preferable. That is, the content of the inorganic particles is preferably 0.5% by mass or more in terms of polishing the barrier layer and the interlayer insulating film at a sufficient polishing rate, and is preferably 15.0% by mass or less in terms of storage stability.

  Here, in the polishing liquid of the present invention, other inorganic particles can be used together with colloidal silica among the inorganic particles. In that case, the content of colloidal silica in the inorganic particles is preferably 50% by mass or more, and particularly preferably 80% by mass or more. All of the contained inorganic particles may be colloidal silica. Examples of abrasive grains that can be used in combination with colloidal silica include fumed silica, ceria, alumina, and titania. The size (particle diameter) of these combined abrasive grains is preferably equal to or more than that of colloidal silica, and preferably twice or less.

<PH of polishing liquid>
The pH of the polishing liquid of the present invention is 1-7. Especially, it is preferably 2-7, more preferably 2-5. Within the above range, the polishing rate of the interlayer insulating film and the barrier layer can be adjusted more easily, and the amount of organic residue and generation of scratches are further suppressed.
In order to adjust the pH, for example, alkali / acids or buffers are used.
Examples of the alkali / acid or buffering agent include non-metallic alkaline agents such as organic ammonium hydroxides such as ammonia, ammonium hydroxide and tetramethylammonium hydroxide, alkanolamines such as diethanolamine, triethanolamine and triisopropanolamine, Alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, inorganic acids such as nitric acid, sulfuric acid and phosphoric acid, carbonates such as sodium carbonate, phosphates and borates such as trisodium phosphate Preferred examples include tetraborate and hydroxybenzoate. Particularly preferred alkali agents include ammonium hydroxide, potassium hydroxide, lithium hydroxide, tetramethylammonium hydroxide and the like.

  The content of the alkali / acid or the buffer may be an amount that maintains the pH within a preferable range, and is preferably 0.0001 mol to 1.0 mol in 1 L of the polishing liquid when used for polishing. , 0.003 mol to 0.5 mol is more preferable.

<Other components>
The polishing liquid of the present invention may contain components such as a surfactant, an oxidizing agent, and a chelating agent within the range not impairing the effects of the present invention in addition to the above-described components.

<Surfactant>
In the polishing liquid of the present invention, a surfactant other than the nonionic surfactant can be used in combination. Examples of the surfactant that can be used in combination include an anionic surfactant and a cationic surfactant.

Specific examples of the anionic surfactant include compounds such as decylbenzenesulfonic acid, dodecylbenzenesulfonic acid, tetradecylbenzenesulfonic acid, hexadecylbenzenesulfonic acid, dodecylnaphthalenesulfonic acid, and tetradecylnaphthalenesulfonic acid. Can be mentioned.
Preferred examples of the anionic surfactant include carboxylic acid salts, sulfuric acid ester salts, and phosphoric acid ester salts in addition to the sulfonic acid salts.
Preferred examples of the carboxylate include soap, N-acyl amino acid salt, polyoxyethylene or polyoxypropylene alkyl ether carboxylate, and acylated peptide.
Preferable examples of sulfate salts include sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfates, and alkylamide sulfates.
Preferred examples of the phosphate ester salt include alkyl phosphates, polyoxyethylene or polyoxypropylene alkyl allyl ether phosphates.

  Specific examples of the cationic surfactant include compounds such as lauryltrimethylammonium, lauryltriethylammonium, stearyltrimethylammonium, palmityltrimethylammonium, octyltrimethylammonium, dodecylpyridinium, decylpyridinium, octylpyridinium, and the like.

  The total content of the surfactant in the polishing liquid of the present invention is preferably 0.001 to 10 g, more preferably 0.01 to 5.0 g in 1 liter of the polishing liquid when used for polishing. 0.01 to 1.0 g is particularly preferable. That is, the content of the surfactant is preferably 0.001 g or more for obtaining a sufficient effect, and is preferably 10 g or less from the viewpoint of preventing the CMP rate from being lowered.

<Oxidizing agent>
The polishing liquid of the present invention can contain a compound (oxidant) capable of oxidizing the metal to be polished.
Examples of the oxidizing agent include hydrogen peroxide, peroxide, nitrate, iodate, periodate, hypochlorite, chlorite, chlorate, perchlorate, persulfate, Examples thereof include dichromate, permanganate, ozone water, silver (II) salt, and iron (III) salt. Among them, hydrogen peroxide is preferably used.
Examples of the iron (III) salt include iron (III) in addition to inorganic iron (III) salts such as iron nitrate (III), iron chloride (III), iron sulfate (III) and iron bromide (III). Organic complex salts are preferably used.

  The content of the oxidizing agent in the polishing liquid of the present invention can be appropriately adjusted depending on the dishing amount at the initial stage of barrier CMP. When the dishing amount at the initial stage of the barrier CMP is large, that is, when it is not desired to polish the wiring material much in the barrier CMP, it is preferable to reduce the content of the oxidizing agent in the polishing liquid. When the dishing amount is sufficiently small and it is desired to polish the wiring material at a high speed, it is preferable to increase the content of the oxidizing agent in the polishing liquid. As described above, it is desirable to change the content of the oxidizing agent depending on the dishing state in the initial stage of the barrier CMP. Especially, it is preferable to set it as 0.01-1.0 mol in 1 L of polishing liquid at the time of using for oxidizing agent content, and it is more preferable to set it as 0.05-0.4 mol.

<Chelating agent>
The polishing liquid of the present invention preferably contains a chelating agent (that is, a hard water softening agent) as necessary in order to reduce adverse effects such as mixed polyvalent metal ions.
Chelating agents include general water softeners and related compounds that are calcium and magnesium precipitation inhibitors, such as nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, N, N, N-trimethylenephosphonic acid. , Ethylenediamine-N, N, N ′, N′-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-diaminopropanetetraacetic acid, glycol etherdiaminetetraacetic acid, ethylenediamine orthohydroxyphenylacetic acid, ethylenediamine disuccinic acid ( SS form), N- (2-carboxylateethyl) -L-aspartic acid, β-alanine diacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, N , N′-bis (2-hydroxyben Le) ethylenediamine -N, N'-diacetic acid, 1,2-dihydroxybenzene-4,4-disulfonic acid.
Two or more chelating agents may be used in combination as necessary.

  The content of the chelating agent in the polishing liquid of the present invention may be an amount sufficient to sequester metal ions such as mixed polyvalent metal ions, for example, in 1 L of the polishing liquid used for polishing. 0.0003 mol to 0.07 mol is preferable.

  The polishing liquid of the present invention contains various solvents as necessary. For example, water or organic solvents such as ethanol, ethylene glycol, and propylene glycol can be used.

  The polishing liquid of the present invention is made of copper or the like that exists between a wiring made of copper metal and / or copper alloy and the like, which is laminated on a semiconductor integrated circuit substrate (for example, a silicon substrate) and an interlayer insulating film. It is suitable for use in chemical mechanical polishing of a barrier layer made of a barrier metal material for preventing metal diffusion and / or an interlayer insulating film having a laminated structure of a low-k film and a TEOS insulating film described later. Normally, in a semiconductor device manufacturing process, after a metal wiring film is provided on a low dielectric constant interlayer insulating film covered with a barrier layer by metal plating, the metal wiring film is polished with a metal polishing liquid. Following the chemical mechanical polishing step, the barrier layer and the interlayer insulating film are polished, and at this time, the polishing liquid of the present invention is preferably used. At this time, it is preferable to insert a process such as cleaning after polishing the wiring metal and before polishing the barrier layer.

<Barrier metal material>
As a material constituting the barrier layer which is one of the objects to be polished (polishing object) of the polishing liquid of the present invention, a metal material having low resistance is generally good, and in particular, Ta, TaN, Ti, TiN, Ru, CuMn, Of MnO ₂ , WN, W and Co, at least one is preferable, and Ta and TaN are particularly preferable.

<Interlayer insulation film>
As an interlayer insulating film (insulating layer) that is one of the objects to be polished (substance to be polished) of the polishing liquid of the present invention, for example, a dielectric constant of 2.0 to An interlayer insulating film including a material having a low dielectric constant of about 3.5 (for example, an organic polymer material, a SiOC material, a SiOF material, etc., and is generally abbreviated as a low-k film) can be given.
Specifically, as a material used for forming a low dielectric constant interlayer insulating film, there are HSG-R7 (Hitachi Chemical Industries), BLACKDIAMOND (Applied Materials, Inc.) and the like in the SiOC system.
Such a Low-k film is usually located on the lower side (substrate side) of the TEOS insulating film, and a barrier layer and metal wiring are formed on the TEOS insulating film.
The polishing liquid of the present invention is suitable for polishing a barrier layer, and has excellent surface smoothness when applied to a substrate having a laminated structure of a low-k film and a TEOS insulating film. It is a great feature that a polished surface can be achieved in which the generation of the organic matter and the amount of organic residue are suppressed.

<Raw metal materials>
In the present invention, it is preferable that the object to be polished has a wiring made of copper metal and / or copper alloy as applied to a semiconductor device such as LSI. In particular, a copper alloy is preferable as a raw material for the wiring. Furthermore, the copper alloy containing silver is preferable among copper alloys.
In addition, the silver content contained in the copper alloy is preferably 40% by mass or less, particularly 10% by mass or less, more preferably 1% by mass or less, and a copper alloy in the range of 0.00001 to 0.1% by mass. The most excellent effect is exhibited.

<Thickness of wiring>
In the present invention, when the object to be polished is applied to, for example, a DRAM device system, it preferably has a wiring with a half pitch of 0.15 μm or less, more preferably 0.10 μm or less, and further Preferably it is 0.08 micrometer or less.
On the other hand, when the object to be polished is applied to, for example, an MPU device system, it is preferable to have a wiring of 0.12 μm or less, more preferably 0.09 μm or less, and still more preferably 0.07 μm or less.
The polishing liquid in the present invention described above exhibits a particularly excellent effect on the object to be polished having such wiring.

<Polishing method>
The polishing liquid of the present invention is 1. 1. A concentrated liquid that is diluted by adding water or an aqueous solution when used. 2. When each component is prepared in the form of an aqueous solution described in the next section, these are mixed, and if necessary diluted with water to make a working solution. Although it may be prepared as a use liquid, it is not limited to these.
The polishing liquid in any case can be applied to the polishing method of the present invention. In this polishing method (chemical mechanical polishing method), a polishing liquid is supplied to a polishing pad on a polishing surface plate and brought into contact with the surface to be polished of the object to be polished so that the surface to be polished and the polishing pad move relative to each other. Is the method.

  As an apparatus used for polishing, a holder for holding an object to be polished (for example, a wafer on which a conductive material film is formed) having a surface to be polished and a polishing pad are attached (a motor capable of changing the number of rotations). Etc.) and a general polishing apparatus having a polishing surface plate. As the polishing pad, a general nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used, and there is no particular limitation. The polishing conditions are not limited, but the rotation speed of the polishing surface plate is preferably a low rotation of 200 rpm or less so that the object to be polished does not pop out. The pressure applied to the polishing pad of the object having the surface to be polished (film to be polished) is preferably 0.48 to 34.5 KPa, and the in-plane uniformity of the object to be polished and the flatness of the pattern at the polishing rate In order to satisfy, 3.40-20.7 KPa is more preferable.

During polishing, it is preferable to continuously supply the polishing liquid to the polishing pad with a pump or the like.
After the polishing is finished, the object to be polished is thoroughly washed in running water, and then dried after removing water droplets adhering to the object to be polished using a spin dryer or the like.

In the present invention, the 1. When diluting the concentrated solution as in the above method, the following aqueous solutions can be used. For example, the aqueous solution is water containing at least one of an oxidizing agent, an organic acid, and a surfactant in advance, and the components contained in the aqueous solution and the concentrated solution to be diluted are contained. A component obtained by summing up the component and the component is used as a component of a polishing liquid (use liquid) used for polishing.
As described above, when the concentrated solution is diluted with an aqueous solution, components that are difficult to dissolve can be added later in the form of an aqueous solution, and a more concentrated concentrated solution can be prepared.

  In addition, as a method of diluting the concentrated liquid by adding water or an aqueous solution, the pipe for supplying the concentrated polishing liquid and the pipe for supplying the water or the aqueous solution are joined together and mixed, and mixed and diluted. There is a method of supplying the used liquid to the polishing pad. Mixing of concentrated liquid and water or aqueous solution is a method in which liquids collide with each other through a narrow passage under pressure, filling the pipe with a filling such as a glass tube, and separating and separating the liquid flow. Ordinary methods such as a method of repeatedly performing and a method of providing a blade rotating with power in the pipe can be adopted.

  The supply rate of the polishing liquid is preferably 10 to 1000 ml / min, and more preferably 170 to 800 ml / min in order to satisfy the uniformity of the polishing rate within the surface to be polished and the flatness of the pattern.

  Further, as a method of polishing while diluting the concentrated solution with water or an aqueous solution, a pipe for supplying the polishing liquid and a pipe for supplying the water or the aqueous solution are provided independently, and a predetermined amount of liquid is respectively applied to the polishing pad. There is a method of supplying and polishing while mixing by the relative motion of the polishing pad and the surface to be polished. It is also possible to use a method in which a predetermined amount of concentrated liquid and water or an aqueous solution are mixed in one container and then the mixed polishing liquid is supplied to the polishing pad to perform polishing.

As another polishing method, the components to be contained in the polishing liquid are divided into at least two components, and when these are used, they are diluted by adding water or an aqueous solution and supplied to the polishing pad on the polishing platen. Then, there is a method in which the surface to be polished and the polishing pad are moved relative to each other and brought into contact with the surface to be polished.
For example, an oxidant is used as the constituent component (A), inorganic particles, quaternary ammonium salts, corrosion inhibitors, organic acids, surfactants, various additives, and water are used as the constituent component (B), and they are used. In particular, the component (A) and the component (B) can be diluted with water or an aqueous solution.
Further, an additive having low solubility is divided into two constituent components (A) and (B). For example, an oxidizing agent, an additive, and a surfactant are used as the constituent component (A), and inorganic particles, quaternary ammonium salts are used. , A corrosion inhibitor, an organic acid, a surfactant, various additives, and water as a constituent component (B). When using them, water or an aqueous solution is added, and the constituent component (A) and the constituent component (B) are added. Dilute and use.

In the case of the above-described example, three pipes for supplying the component (A), the component (B), and water or an aqueous solution are required, and dilution mixing supplies the three pipes to the polishing pad. There is a method of combining in one pipe and mixing in the pipe. In this case, it is possible to combine two pipes and then connect another one pipe. Specifically, it is a method in which a constituent component containing an additive that is difficult to dissolve is mixed with another constituent component, a mixing path is lengthened to ensure a dissolution time, and a water or aqueous solution pipe is further combined. .
Other mixing methods include, as described above, directly connecting the three pipes to the polishing pad and mixing them by relative movement between the polishing pad and the surface to be polished, or mixing three components in one container. From there, there is a method of supplying a diluted polishing liquid to the polishing pad.

  In the above polishing method, when one constituent component containing an oxidizing agent is made 40 ° C. or lower and the other constituent components are heated in the range of room temperature to 100 ° C., one constituent component and another constituent component are mixed. Alternatively, there is also a method of setting the liquid temperature to 40 ° C. or lower when diluting by adding water or an aqueous solution. This method is a preferable method for increasing the solubility of the raw material having a low solubility of the polishing liquid by utilizing the phenomenon that the solubility becomes high when the temperature is high.

  The raw materials in which the above other components are dissolved by heating in the range of room temperature to 100 ° C. are precipitated in the solution when the temperature is lowered. It is necessary to dissolve the raw material deposited by heating. For this purpose, there are provided means for heating and feeding the other constituents in which the raw material is dissolved, and means for stirring and feeding the liquid containing the precipitate, and heating and dissolving the piping. Can be adopted. When the temperature of one component containing an oxidizing agent is increased to 40 ° C. or higher when other heated components are heated, the oxidizing agent may be decomposed. For this reason, when this other heated component and one component containing an oxidizing agent are mixed, it is preferable that the temperature be 40 ° C. or lower.

Thus, in the present invention, the components of the polishing liquid may be divided into two or more parts and supplied to the surface to be polished. In this case, it is preferable to divide and supply the component containing an oxide and the component containing an organic acid. Alternatively, the polishing liquid may be a concentrated liquid and supplied to the surface to be polished separately from the dilution water.
In the present invention, when a method of supplying a polishing liquid component into two or more parts and supplying it to the surface to be polished is applied, the supply amount represents the total supply amount from each pipe.

<Polishing pad>
The polishing pad for polishing applicable to the polishing method of the present invention may be a non-foamed structure pad or a foamed structure pad. The former uses a hard synthetic resin bulk material like a plastic plate for a pad. Further, the latter further includes three types of a closed foam (dry foam), a continuous foam (wet foam), and a two-layer composite (laminate), and a two-layer composite (laminate) is particularly preferable. Foaming may be uniform or non-uniform.
Further, it may contain inorganic particles generally used for polishing (abrasive grains: for example, ceria, silica, alumina, etc.). In addition, the hardness may be either soft or hard, and either may be used. In the laminated system, it is preferable to use a different hardness for each layer. As the material, non-woven fabric, artificial leather, polyamide, polyurethane, polyester, polycarbonate and the like are preferable. Further, the surface contacting the surface to be polished may be subjected to processing such as lattice grooves / holes / concentric grooves / helical grooves.

<Wafer>
The diameter of a wafer as an object to be polished by CMP using the polishing liquid of the present invention is preferably 200 mm or more, particularly preferably 300 mm or more. The effect of the present invention is remarkably exhibited when the thickness is 300 mm or more.

<Polishing device>
An apparatus capable of performing polishing using the polishing liquid of the present invention is not particularly limited, but is mira mesa CMP, reflexion CMP (Applied Materials), FREX200, FREX300 (Ebara Seisakusho), NPS3301, NPS2301 (Nikon), A-FP -310A, A-FP-210A (Tokyo Seimitsu), 2300 TERES (Ram Research), Momentum (Speedfam IPEC), etc. can be mentioned.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to them.

[Example 1]
A polishing liquid having the composition shown below was prepared and a polishing experiment was conducted. In addition, the organic acid B-1 in the following composition (1) is the organic acid B-1 illustrated as a specific example of the organic acid containing at least one nitrogen atom and two or more carboxyl groups. Applicable.
<Composition (1)>
・ Quaternary ammonium salt: Tetramethylammonium hydroxide 0.1 g / L
・ Corrosion inhibitor: Tetrazole 0.01 g / L
Inorganic particles: colloidal silica 3.7 wt% (content in the total amount of polishing liquid)
(Particle size: 45-70 nm)
Organic acid containing at least one nitrogen atom and two or more carboxyl groups: B-1
(Wako Pure Chemical Industries, Ltd.) 1g / L
・ Oxidizing agent: Hydrogen peroxide 10ml
・ Pure water is added and the total volume is 1000mL
pH (adjusted with ammonia water and nitric acid) 2.0

<Evaluation method>
The wafer film shown below was grind | polished, supplying the slurry (composition (1)) on the following conditions using the apparatus "LGP-412" by a lap master company as a grinding | polishing apparatus.
・ Table rotation speed: 90rpm
-Head rotation speed: 85rpm
Polishing pressure: 13.79 kPa
Polishing pad: Rotex Nitta Co., Ltd. Polotepad
Polishing liquid supply rate: 200 ml / min

<Scratch evaluation, organic residue amount evaluation: polishing object>
As an object to be polished, a low-k film (SiOC film (BLACKDIAMMOND (Applied Materials, Inc)) (thickness: 400 nm) on a Si substrate and a TEOS (tetraethoxysilane) film (on the low-K film) are formed. (Thickness: 50 nm) was formed by a CVD method and patterned by a photolithography process and a reactive ion etching process to form wiring grooves and connection holes having a width of 0.09 to 100 μm and a depth of 400 nm. Further, a Ta film having a thickness of 20 nm is formed on the laminated film and in the wiring groove by a sputtering method, and subsequently a copper film having a thickness of 50 nm is formed by a sputtering method, and then a copper film having a total thickness of 1000 nm is formed by a plating method. An 8-inch wafer on which a film was formed was used.

<Scratch evaluation>
Each layer laminated | stacked on the board | substrate was grind | polished on said grinding | polishing conditions using the said grinding | polishing target object for scratch evaluation. After polishing the copper film, Ta film, and TEOS layer, the SiOC film was polished (SiOC film was polished to 20 nm), and the polished surface was washed with pure water and dried. The dried polished surface was observed with an optical microscope, and scratches were evaluated based on the following evaluation criteria. In addition, it is judged that ○ is a level with no practical problem. The obtained results are shown in Table 2.
-Evaluation criteria-
○: No problem scratch is observed Δ: One or two problem scratches are observed in the wafer surface ×: Many problem scratches are observed in the wafer surface

<Evaluation of organic residue amount>
The polished surface used in the above scratch evaluation was observed with an optical microscope, and the amount of organic residue was evaluated based on the following evaluation criteria. In addition, it is judged that ○ is a level with no practical problem. The obtained results are shown in Table 2.
-Evaluation criteria-
○: No problematic organic residue is observed Δ: One or two problematic organic residues are observed in the wafer surface ×: Many problematic organic residues are observed in the wafer surface

[Examples 2-46 and Comparative Examples 1-3]
Polishing experiments were performed under the same polishing conditions as in Example 1 using a polishing liquid prepared by changing the composition (1) in Example 1 to the composition shown in Table 1 (total amount of 1000 mL by adding pure water). . The composition of the polishing liquid is shown in Table 1, and the results of using those polishing liquids (Examples 1 to 46, Comparative Examples 1 to 3) are shown in Table 2.
In addition, the types “A-1 to A-32” of the various quaternary ammonium salts used in Table 1 correspond to the specific examples A-1 to A-32 of the specific cation of the quaternary ammonium salt, respectively. Yes. Furthermore, the anions of these various quaternary ammonium salts are nitrate ions.
As the inorganic particles, inorganic particles such as zirconia, ceria, alumina, fumed silica and the like were used in addition to the colloidal silica.
Moreover, as a corrosion inhibitor, a commercially available product was used.
In addition, the organic acids “B-1 to B-28” used in Table 1 are examples of the organic acids B-1 to B-28 that include at least one nitrogen atom and two or more carboxyl groups, respectively. It corresponds.

From the above results, when the polishing liquid of the present invention is used, when polishing various films (Ta film (barrier layer), TEOS film, SiOC film (interlayer insulating film)), reduction in the amount of organic residue and low scratches are achieved. Could be achieved.
On the other hand, in the comparative example, it was impossible to achieve both reduction in the amount of organic residue and low scratch.

Claims (5)

  A polishing liquid used for chemical mechanical polishing of a barrier layer and / or an interlayer insulating film in a manufacturing process of a semiconductor integrated circuit, comprising a quaternary ammonium salt, a corrosion inhibitor, at least one nitrogen atom and two or more A polishing liquid comprising an organic acid containing a carboxyl group and inorganic particles, and having a pH of 1 to 7. The polishing liquid according to claim 1, wherein the quaternary ammonium salt is a compound represented by the general formula (1) or the general formula (2).

(In General Formula (1), R ^{1 to} R ⁴ each independently represents an alkyl group, alkenyl group, cycloalkyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms. X ⁻ represents a monovalent group. It represents an anion. in addition, any two of R ¹ to R ^4, may form a cyclic structure bonded to each other.
In General Formula (2), R ^{5 to} R ¹⁰ each independently represent an alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, or an aralkyl group. M represents an alkylene group having 1 to 20 carbon atoms, an alkenylene group, a cycloalkylene group, an arylene group, or a group obtained by combining two or more thereof. X ⁻ represents a monovalent anion, and Y ²⁻ represents a divalent anion. Note that any two of R ^{5 to} R ¹⁰ may be bonded to each other to form a cyclic structure. )   The polishing liquid according to claim 1 or 2, wherein the inorganic particles are at least one inorganic particle selected from the group consisting of silica, alumina, ceria, zirconia, and titania.   The polishing liquid according to any one of claims 1 to 3, wherein the content of the inorganic particles in the polishing liquid is 0.5 to 15% by mass with respect to the total mass of the polishing liquid. The object to be polished is a metal layer made of at least one metal selected from the group consisting of Ta, TaN, Ti, TiN, Ru, CuMn, MnO ₂ , WN, W, and Co. A polishing liquid according to any one of the above.