JP2007116090A - Polishing solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing solution capable of suitably setting the polishing speeds of a barrier metal layer (barrier material), an insulating film layer (insulating material), and a metal wiring layer (metallic wiring material), in barrier CMP to be performed continuously to bulk polishing of metal wires in the case of manufacturing a semiconductor device; capable of suppressing the generation of final steps such as dishing and erosion; and capable of stably storing a polishing solution component while maintaining high dispersion. <P>SOLUTION: The polishing solution for polishing a barrier material on an inter-layer insulating material has pH of 5.5 to 8.5 and is an aqueous solution of a dicarboxylic acid compound in which silicon dioxide particles are dispersed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to the manufacture of semiconductor devices, and more particularly to a polishing liquid for polishing a barrier material in a wiring process of a semiconductor device.

  In the development of a semiconductor device represented by a semiconductor integrated circuit (hereinafter referred to as LSI), in recent years, in order to reduce the size and increase the speed, there has been a demand for higher density and higher integration by miniaturizing and stacking wiring. For this purpose, various techniques such as chemical mechanical polishing (hereinafter referred to as CMP) have been used. This CMP is an indispensable technique for surface flattening of a film to be processed such as an interlayer insulating film, plug formation, formation of a buried metal wiring, etc., and an extra metal thin film at the time of substrate smoothing or wiring formation. Removal or removal of an extra barrier metal layer (barrier material) on the insulating film is performed. This technique is disclosed in Patent Document 1, for example.

  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 semiconductor devices such as LSI, fine wiring is formed in multiple layers, and when forming metal wiring such as Cu in each layer, diffusion of wiring material to the interlayer insulating film In order to prevent this and to improve the adhesion of the wiring material, a barrier metal such as Ta, TaN, Ti, or TiN is formed in advance. In order to form each wiring layer, first, CMP of a metal film (hereinafter referred to as metal film CMP) for removing excess wiring material deposited by plating or the like is performed in one or more stages. In general, CMP for removing the barrier metal exposed on the surface (hereinafter referred to as barrier metal CMP) is generally performed. However, there is a problem that the metal film CMP causes so-called dishing in which the wiring portion is excessively polished and further causes erosion.

  In order to reduce this dishing, in the next barrier metal CMP, the polishing speed of the metal wiring portion and the polishing speed of the barrier metal portion are adjusted to finally form a wiring layer with few steps such as dishing and erosion. It has been demanded. That is, in the barrier metal CMP, if the polishing rate of the barrier metal or the interlayer insulating film is relatively small compared to the metal wiring material, dishing and erosion occur as a result of the wiring portion being polished faster. It is desirable that the polishing rate of the barrier metal or the insulating film layer is appropriately high. This has the advantage of increasing the throughput of barrier metal CMP, and in fact, dishing often occurs due to metal film CMP, and for the reasons described above, the polishing rate of the barrier metal or insulating film layer is relatively high. This is also desirable in that it is required to be higher.

In the polishing liquid as described above, it is necessary to adjust the polishing rate ratio of the barrier metal layer and insulating film layer to the metal wiring material to an appropriate selection ratio, and to reduce the final step such as dishing and erosion as much as possible. It has become.
US Pat. No. 4,944,836

  The present invention relates to a barrier CMP performed after bulk polishing of metal wiring in the manufacture of a semiconductor device, and includes a barrier metal layer (barrier material), an insulating film layer (insulating material), and a metal wiring layer (metal wiring material). It is based on the problem of providing a polishing liquid that can be stored stably for a long period of time while maintaining high dispersion while maintaining the high dispersion of the polishing liquid while suppressing the occurrence of final steps such as dishing and erosion. It is a thing.

As a result of intensive studies on the problems associated with the above-described barrier polishing liquid, the present inventors have found that the problem can be solved by using the following barrier polishing liquid, and have achieved the object.
That is, the present invention is as follows.
(1) A polishing liquid for polishing a barrier material on an insulating material, which is an aqueous solution containing a dicarboxylic acid compound and having a pH of 5.5 to 8.5 and in which silicon oxide particles are dispersed. .
A polishing liquid for polishing a barrier material on an insulating material, wherein the polishing liquid is an aqueous solution of a dicarboxylic acid compound having a pH of 5.5 to 8.5 and in which silicon oxide particles are dispersed.
(2) The polishing liquid according to (1), wherein the electric conductivity of the polishing liquid is 10 mS / cm or less.
(3) The polishing liquid according to (1) or (2), further comprising a heterocyclic compound in a range of 0.01 to 0.10% by weight.

(4) The silicon oxide particles include at least a colloidal silica having a primary particle diameter in a range of 15 to 70 nm when converted from a specific surface area to a true spherical particle model, or a colloidal silica having a primary particle diameter in the range. The polishing liquid according to any one of (1) to (3), wherein the polishing liquid is any one of the above.
(5) The barrier material is composed of at least one of tantalum, tantalum nitride, titanium, titanium nitride, tungsten, tungsten nitride, nickel, nickel nitride, ruthenium, and a compound thereof. The polishing liquid according to any one of 1) to (4).
(6) The polishing liquid according to any one of (1) to (5), further comprising an oxidizing agent.

  According to the present invention, a barrier metal layer (barrier material), an insulating film layer (insulating material), and a metal wiring layer (metal wiring material) in barrier CMP performed following bulk polishing of metal wiring in the manufacture of a semiconductor device. Thus, it is possible to provide a polishing liquid that can be stably stored for a long period of time while maintaining high dispersion of the polishing liquid component, while suppressing the occurrence of final steps such as dishing and erosion.

  The polishing liquid of the present invention is a polishing liquid (slurry) for polishing a barrier material on an interlayer insulating material, and has a pH of 5.5 to 8.5 and an aqueous solution of a dicarboxylic acid compound in which silicon oxide particles are dispersed. It is. That is, it is a polishing liquid comprising at least a dicarboxylic acid compound and silicon oxide particles as constituent components and comprising an aqueous solution having a pH of 5.5 to 8.5. More preferably, the dispersion stability of the contained particles can be maintained when the electric conductivity is 10 mS / cm or less.

  The polishing liquid of the present invention has a pH of 5.5 to 8.5 as described above, preferably a pH of 6.0 to 8.5, and more preferably a pH of 6.5 to 8.0. When the pH of the polishing liquid is too low, the polishing rate of the wiring portion is increased and dishing is likely to occur, and when the pH is too high, the polishing rate of the barrier layer is decreased and is inefficient. The range is suitable.

By setting the pH of the polishing liquid within the above range, and preferably by setting the electric conductivity to 10 mS / cm or less, the solids contained in the polishing liquid aggregate in a short time, and if this is remarkable, gelation occurs. Occurrence of such a phenomenon as to occur is suppressed, and a stable dispersed state can be maintained for a long period of time.
The electrical conductivity of the polishing liquid is preferably 10 mS / cm or less, more preferably 0.2 to 8.0 mS / cm, and still more preferably 0.2 to 7.0 mS / cm. desirable.
In addition, the polishing liquid of the present invention may cause aggregation or gelation depending on the ionic strength of the polishing liquid depending on the type of silicon oxide particles. From the viewpoint of suppressing the occurrence of such a phenomenon, The conductivity is preferably 10 mS / cm or less. The electric conductivity is more preferably 0.2 to 8.0 mS / cm, and more preferably 0.2 to 7.0 mS / cm.
In addition, electrical conductivity can be adjusted with the addition amount of the said dicarboxylic acid and the addition amount of pH adjusters, such as an acid and an alkali.
The electric conductivity in the present invention employs a value obtained by the following measurement method.
That is, it refers to a value measured using a commercially available electric conductivity meter (for example, DS-52 manufactured by Horiba, Ltd.) with respect to a polishing solution obtained by removing solids such as particles from the polishing solution by filtration or the like.

The polishing liquid of the present invention may contain other components in addition to the dicarboxylic acid compound and silicon oxide particles, and as preferred components, compounds added as so-called immobilization film forming agents, surfactants, water-soluble substances Mention may be made of polymers and additives.
Note that the polishing liquid of the present invention may contain components other than the substances described below depending on the purpose.
Each of the components contained in these metal polishing liquids may be used alone or in combination of two or more.

  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 a metal 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 generally involve physical concentration operations such as evaporation. The term is used in a different way from the meaning of common terms.

[Dicarboxylic acid compound]
The dicarboxylic acid compound used in the present invention is, for example, oxalic acid, malonic acid, succinic acid, glyoxylic acid, adipic acid, malonic acid, maleic acid, phthalic acid, fumaric acid, malic acid, citralmalic acid, tartaric acid, citric acid, Examples include iminodiacetic acid and hydroxyethyliminodiacetic acid.
The total amount of the dicarboxylic acid compound added is preferably 0.0005 to 3 mol, more preferably 0.01 to 0.5 mol in 1 L of the metal polishing liquid used for polishing.
Two different types of the above compounds can be used in combination. The ratio in this case is generally 100/1 to 1/100, preferably 10/1 to 1/10 as a mass ratio.

[Silicon oxide particles]
As the silicon oxide particles as the abrasive grains, for example, silicon oxide and composite particles containing the same can be used. Specifically, examples of the silicon oxide particles include colloidal silica, fumed silica, and plasma fused silica. Examples of the composite particles include core-shell particles containing the above silica species and composite particles in which guest particles are attached to the surface of the core particles. Etc.
For example, the silicon oxide particle particles have colloidal silica having a primary particle diameter in a range of 15 to 70 nm (preferably in a range of 25 to 70 nm) when converted from a specific surface area to a true spherical particle model, or a primary in this range. A composite particle containing at least colloidal silica having a particle size is preferable.

Here, the primary particle diameter when converted from a specific surface area to a true spherical particle model is measured as follows. When the primary particles are regarded as ideal spheres, the following relationship is approximately established between the surface area S, volume V, density ρ, and specific surface area SSA of each particle.
SSA = 1 / (V · ρ) × S
Here, since V and S are physical quantities that are uniquely determined by the particle diameter, the particle diameter can be determined from the specific surface area and density.
That is, the primary particle diameter of silicon oxide used as an abrasive grain in the present invention is determined based on the specific surface area SSA of silicon oxide particles used as a sample by using a specific surface area measuring device such as the BET method (for example, Tristar manufactured by Shimadzu Corporation). 3000), and the density ρ is obtained by, for example, a commercially available pycnometer, and a value calculated from these values is used.

  Silicon oxide particles can be obtained by well-known production methods. Colloidal particles are obtained, for example, by a method of hydrolyzing metal alkoxide as a starting material as a wet production method of metal oxide particles. Specifically, normal methyl silicate is added to an alkaline aqueous solution mixed with alcohol. Colloidal silica can be produced by dropping at a certain rate to cause hydrolysis, and through a period of grain growth and a period when grain growth is stopped by quenching. In addition, colloidal particles are made using alkoxides such as aluminum and titanium. In this case, the rate of hydrolysis is generally faster than when silicon alkoxide is used, which is convenient when producing ultrafine particles.

  As a dry process for producing metal oxides, fumed particles can be obtained by a reaction in which metal chloride is introduced into an oxyhydrogen flame and the dechlorinated metal is oxidized. Furthermore, the metal or alloy to be contained in the target substance is pulverized into a powder, which is put into an oxygen flame containing a combustion-supporting gas, causing a continuous reaction due to the heat of oxidation of the metal, and a fine A method for obtaining oxide particles has also been put into practical use. Particles created by these combustion methods are amorphized because they experience high heat in the manufacturing process, and generally have a higher solid density because there are fewer impurities such as hydroxyl groups inside compared to wet particles. The surface hydroxyl group density is also low.

[Immobilized film forming agent]
The polishing liquid of the present invention can contain at least one heterocyclic compound as a compound that forms a passive film on the metal surface to be polished.
A “heterocyclic compound” is a compound having a heterocyclic ring containing one or more heteroatoms. A hetero atom means an atom other than a carbon atom or a hydrogen atom. A heterocycle means a cyclic compound having at least one heteroatom. A heteroatom means only those atoms that form part of a heterocyclic ring system, either external to the ring system, separated from the ring system by at least one non-conjugated single bond, Atoms that are part of a further substituent of are not meant.

  A hetero atom is preferably a nitrogen atom, a sulfur atom, an oxygen atom, a selenium atom, a tellurium atom, a phosphorus atom, a silicon atom, and a boron atom, and more preferably a nitrogen atom, a sulfur atom, an oxygen atom, and a selenium atom. And particularly preferably a nitrogen atom, a sulfur atom and an oxygen atom, and most preferably a nitrogen atom and a sulfur atom.

First, the heterocyclic ring that is the mother nucleus is described.
The number of members of the heterocyclic ring of the heterocyclic compound used in the present invention is not particularly limited, and may be a monocyclic compound or a polycyclic compound having a condensed ring. The number of members in the case of a single ring is preferably 3 to 8, more preferably 5 to 7, and particularly preferably 5 and 6. The number of rings in the case of having a condensed ring is preferably 2 to 4, more preferably 2 or 3.
Specific examples of these heterocyclic rings include the following. However, it is not limited to these.

  Pyrrole ring, thiophene ring, furan ring, pyran ring, thiopyran ring, imidazole ring, pyrazole ring, thiazole ring, isothiazole ring, oxazole ring, isoxazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, pyrrolidine ring, Pyrazolidine ring, imidazolidine ring, isoxazolidine ring, isothiazolidine ring, piperidine ring, piperazine ring, morpholine ring, thiomorpholine ring, chroman ring, thiochroman ring, isochroman ring, isothiochroman ring, indoline ring, isoindoline ring, pyringin Ring, indolizine ring, indole ring, indazole ring, purine ring, quinolidine ring, isoquinoline ring, quinoline ring, naphthyridine ring, phthalazine ring, quinoxaline ring, quinazoline ring, cinnoline ring, pteridine ring, acridine Perimidine ring, phenanthroline ring, carbazole ring, carboline ring, phenazine ring, anti-lysine ring, thiadiazole ring, oxadiazole ring, triazine ring, triazole ring, tetrazole ring, benzimidazole ring, benzoxazole ring, benzthiazole ring, benz A thiadiazole ring, a benzfuroxan ring, a naphthimidazole ring, a benztriazole ring, a tetraazaindene ring and the like are mentioned, and a triazole ring and a tetrazole ring are more preferred.

Examples of the substituent that can be introduced into the heterocyclic compound used in the present invention include the following.
Examples of the substituent that the heterocyclic ring may have include, for example, a halogen atom, an alkyl group (a linear, branched or cyclic alkyl group, and an active methine group, even a polycyclic alkyl group such as a bicycloalkyl group). Or an alkenyl group, an alkynyl group, an aryl group, an amino group, or a heterocyclic group. Furthermore, two or more of a plurality of substituents may be bonded to each other to form a ring, and for example, an aromatic ring, an aliphatic hydrocarbon ring, a heterocyclic ring, or the like can be formed.

Specific examples of the heterocyclic compound that can be particularly preferably used in the present invention include, but are not limited to, the following.
That is, 1,2,3,4-tetrazole, 5-amino-1,2,3,4-tetrazole, 5-methyl-1,2,3,4-tetrazole, 1,2,3-triazole, 4- Amino-1,2,3-triazole, 4,5-diamino-1,2,3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 3,5-diamino- 1,2,4-triazole, benzotriazole and the like.

The heterocyclic compounds used in the present invention may be used alone or in combination of two or more. Moreover, the heterocyclic compound used by this invention can be synthesize | combined according to a conventional method, and may use a commercial item.
The total amount of the heterocyclic compound used in the present invention is the metal polishing liquid used for polishing (that is, the diluted metal polishing liquid when diluted with water or an aqueous solution. "The polishing liquid for metal" is also agreed.) Is preferably in the range of 0.01 to 0.10 wt%, more preferably in the range of 0.03 to 0.10 wt%. More preferably, it is in the range of 0.04 to 0.08% by weight.

〔Oxidant〕
The metal-polishing liquid of the present invention can contain a compound (oxidant) that can oxidize a metal (barrier material) 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.
Examples of iron (III) salts include inorganic iron (III) salts such as iron nitrate (III), iron chloride (III), iron sulfate (III), iron bromide (III), and organic iron (III) salts. Complex salts are preferably used.

The addition amount of the oxidizing agent is preferably 0.003 mol to 8 mol, more preferably 0.03 mol to 6 mol, and more preferably 0.1 mol to 4 mol in 1 liter of the metal polishing liquid used for polishing. It is particularly preferable to do this. That is, the addition amount of the oxidizing agent is preferably 0.003 mol or more from the viewpoint of sufficient metal oxidation and ensuring a high CMP rate, and is preferably 8 mol or less from the viewpoint of preventing roughening of the polished surface.
Moreover, an oxidizing agent is good also as a polishing liquid, adding to the composition containing another component just before use.

(PH adjuster)
The polishing liquid of the present invention is preferably added with an alkali / acid or a buffer so as to have a pH of 5.5 to 8.5. Within this range, the metal liquid of the present invention exhibits excellent effects.
Alkali / acid or buffering agents include organic ammonium hydroxides such as ammonium hydroxide and tetramethylammonium hydroxide, non-metallic alkaline agents such as alkanolamines such as diethanolamine, triethanolamine, triisopropanolamine, water Alkali metal hydroxides such as sodium oxide, 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, Preferable examples include tetraborate and hydroxybenzoate. Particularly preferred alkali agents are ammonium hydroxide, potassium hydroxide, lithium hydroxide and tetramethylammonium hydroxide.

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

[Chelating agent]
The metal 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.
Examples of chelating agents include general water softeners and related compounds that are calcium and magnesium precipitation inhibitors, such as nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid (EDTA), N, N, N-trile. Methylenephosphonic acid, ethylenediamine-N, N, N ', N'-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-diaminopropanetetraacetic acid, glycol etherdiaminetetraacetic acid, ethylenediamine orthohydroxyphenylacetic acid, ethylenediaminedi Succinic acid (SS form), N- (2-carboxylate ethyl) -L-aspartic acid, β-alanine diacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphone Acid, N, N′-bis (2 Hydroxybenzyl) ethylenediamine -N, N'-diacetic acid, 1,2-dihydroxy-4,6-disulfonic acid.

Two or more chelating agents may be used in combination as required.
The addition amount of the chelating agent may be an amount sufficient to sequester metal ions such as mixed polyvalent metal ions. For example, 0.0003 mol to 0 in 1 L of a metal polishing liquid used for polishing. 0.07 mol is added.

〔Additive〕
Moreover, it is also preferable to use the following additives for the polishing liquid of the present invention.
Ammonia; alkylamines such as dimethylamine, trimethylamine, triethylamine, and propylenediamine; amines such as ethylenediaminetetraacetic acid, sodium diethyldithiocarbamate, and chitosan; dithizone, cuproin (2,2′-biquinoline), neocuproine (2,9-dimethyl) -1,10-phenanthroline), bathocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and cuperazones (biscyclohexanone oxalylhydrazone); nonyl mercaptans, dodecyl mercaptans, triazine thiols, triazines Mercaptans such as dithiol and triazine trithiol; L-tryptophan, cuperazone.

  Among these, chitosan, ethylenediaminetetraacetic acid, L-tryptophan, cuperazone, and triazinedithiol are preferable for achieving both a high CMP rate and a low etching rate.

  The addition amount of these additives is preferably 0.0001 mol to 0.5 mol, more preferably 0.001 mol to 0.2 mol, in 1 L of the metal polishing liquid used for polishing. It is especially preferable to set it as 005 mol-0.1 mol. That is, the addition amount of the additive is preferably 0.0001 mol or more from the viewpoint of suppressing etching, and preferably 0.5 mol or less from the viewpoint of preventing a decrease in CMP rate.

(Surfactant / Hydrophilic polymer)
The polishing liquid of the present invention preferably contains a surfactant and a hydrophilic polymer.
Both the surfactant and the hydrophilic polymer have the action of reducing the contact angle of the surface to be polished and the action of promoting uniform polishing. As the surfactant and the hydrophilic polymer used, those selected from the following groups are suitable.
Examples of the anionic surfactant include carboxylate, sulfonate, sulfate ester salt and phosphate ester salt. Examples of the cationic surfactant include aliphatic amine salt, aliphatic quaternary ammonium salt, benzalkonium chloride. Salt, benzethonium chloride, pyridinium salt, imidazolinium salt, and amphoteric surfactants include carboxybetaine type, aminocarboxylate, imidazolinium betaine, lecithin, alkylamine oxide, nonionic interface Examples of the activator include an ether type, an ether ester type, an ester type, and a nitrogen-containing type, and also include a fluorine-based surfactant.
Furthermore, examples of the hydrophilic polymer include polyglycols such as polyethylene glycol, polysaccharides such as polyvinyl alcohol, polovinyl pyrrolidone, and alginic acid, and carboxylic acid-containing polymers such as polymethacrylic acid.

Of the above, the acid or its ammonium salt is preferably free from contamination by alkali metals, alkaline earth metals, halides and the like. Among the above exemplified compounds, cyclohexanol, polyacrylic acid ammonium salt, polyvinyl alcohol, succinic acid amide, polo vinyl pyrrolidone, polyethylene glycol, and polyoxyethylene polyoxypropylene block polymer are more preferable.
The weight average molecular weight of these surfactants and hydrophilic polymers is preferably from 500 to 100,000, particularly preferably from 2,000 to 50,000.

  Of the components added during the preparation of the concentrated concentrate of the polishing liquid, the blending amount of water having a solubility in water at room temperature of less than 5% is that at room temperature, in order to prevent precipitation when the concentrated liquid is cooled to 5 ° C. The solubility in water is preferably within 2 times, more preferably within 1.5 times.

[Barrier material (barrier metal layer)]
The polishing liquid of the present invention generally prevents diffusion of copper existing between a wiring made of copper metal and / or a copper alloy and an interlayer insulating film, and improves adhesion between the wiring and the interlayer insulating film to prevent peeling. Therefore, it is suitable for polishing a barrier metal layer (barrier material) and an interlayer insulating film provided for the purpose.
The barrier metal layer is generally made of tantalum (Ta), tantalum nitride (TaN), titanium (Ti), titanium nitride (TiN), tungsten (W), tungsten nitride (WN), nickel (Ni), nickel nitride (NiN), It is preferably composed of ruthenium (Ru) and at least one of these compounds. Titanium (Ti) and titanium tungsten (TiW: titanium-tungsten alloy) can also be applied. Among these, tantalum (Ta) and tantalum nitride (TaN) are particularly preferable.

[Raw metal materials]
In the present invention, the semiconductor device that is the object to be polished (target to be polished) is preferably an LSI having wiring made of copper metal and / or a copper alloy, and a copper alloy is particularly preferable. Furthermore, the copper alloy containing silver is preferable among copper alloys. The silver content contained in the copper alloy is preferably 40% by weight or less, particularly preferably 10% by weight or less, more preferably 1% by weight or less, most preferably in the range of 0.00001 to 0.1% by weight. Exhibits excellent effects.

[Wiring thickness]
In the present invention, a semiconductor device which is an object to be polished (object to be polished) is, for example, a DRAM device system having a half pitch of 0.15 μm or less, particularly 0.10 μm or less, further 0.08 μm or less, while MPU device In the system, an LSI having a wiring of 0.12 μm or less, particularly 0.09 μm or less, and further 0.07 μm or less is preferable. The polishing liquid of the present invention exhibits particularly excellent effects on these LSIs.

[Polishing method]
The polishing liquid of the present invention is a concentrated liquid and is diluted by adding water when used, or each component is mixed in the form of an aqueous solution described in the next section, and water is added if necessary. In addition, it may be diluted to give a working solution or may be prepared as a working solution. The polishing method using the metal polishing liquid of the present invention can be applied to any case, and the polishing liquid is supplied to the polishing pad on the polishing surface plate and brought into contact with the surface to be polished to thereby connect the surface to be polished and the polishing pad. This is a polishing method in which polishing is performed by relative movement.

As an apparatus for polishing, there is a general polishing apparatus having a polishing surface plate with a holder for holding a semiconductor substrate having a surface to be polished and a polishing pad attached (a motor etc. capable of changing the number of rotations is attached). Can be used. 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 substrate does not jump out. The pressure applied to the polishing pad of the semiconductor substrate having the surface to be polished (film to be polished) is preferably ⁵ to 500 g / cm ² in order to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern. Is more preferably 12 to 240 g / cm ² .

  During polishing, a polishing liquid for metal is continuously supplied to the polishing pad with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with polishing liquid. The semiconductor substrate after polishing is thoroughly washed in running water, and then dried after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like. In the polishing method of the present invention, the aqueous solution to be diluted is the same as the aqueous solution described below. The aqueous solution is water that contains at least one of an oxidizing agent, an acid, an additive, and a surfactant in advance, and the total amount of the components contained in the aqueous solution and the components of the metal polishing liquid to be diluted is a metal. It becomes the component at the time of grinding | polishing using the polishing liquid. When diluted with an aqueous solution and used, components that are difficult to dissolve can be blended in the form of an aqueous solution, and a more concentrated metal polishing liquid can be prepared.

  As a method of diluting by adding water or an aqueous solution to the concentrated polishing liquid, the pipe for supplying the concentrated metal polishing liquid and the pipe for supplying the water or the aqueous solution are merged and mixed, mixed and diluted. There is a method of supplying a metal polishing liquid to a polishing pad. Mixing is a method in which liquids collide with each other through a narrow passage under pressure, a method in which a filling such as a glass tube is filled in a pipe, and the flow of liquid is repeatedly separated and merged. Conventional methods such as a method of providing blades that rotate in the above can be employed.

  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 in-plane uniformity of the polishing target (wafer) and the flatness of the pattern. .

  As a method of diluting and polishing the concentrated polishing liquid with water or an aqueous solution, a pipe for supplying the polishing liquid and a pipe for supplying water or an aqueous solution are provided independently, and a predetermined amount of liquid is supplied from each to the polishing pad. In this method, the polishing pad and the surface to be polished are mixed while being mixed by relative movement. Alternatively, there is a method in which a predetermined amount of concentrated metal polishing liquid and water or an aqueous solution are mixed in one container, and then the mixed polishing liquid is supplied to a polishing pad for polishing.

  According to another polishing method of the present invention, the component to be contained in the polishing liquid is divided into at least two components, and when these components are used, they are diluted by adding water or an aqueous solution and supplied to the polishing pad on the polishing platen. In this method, 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 one component (A), an acid, an additive, a surfactant, and water are one component (B). The component (B) is diluted before use.
In addition, the low-solubility additive is divided into two components (A) and (B), and the oxidizing agent, additive and surfactant are one component (A), and the acid, additive, surfactant and Water is used as one component (B), and when these are used, water or an aqueous solution is added to dilute the component (A) and the component (B). In the case of this example, three pipes for supplying the component (A), the component (B), and water or an aqueous solution are required, and dilution mixing is performed on one pipe that supplies the three pads to the polishing pad. There is a method of combining and mixing in the pipe. In this case, it is also possible to combine two pipes and then connect another pipe.

  For example, 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 then a pipe of water or an aqueous solution is further combined. Other mixing methods are as described above, in which the three pipes are each guided directly to the polishing pad and mixed by the relative movement of the polishing pad and the surface to be polished, and the three components are mixed in one container. A method for supplying a diluted metal polishing liquid to a polishing pad. In the above polishing method, one constituent component containing an oxidizing agent is made 40 ° C. or lower, the other constituent components are heated in the range of room temperature to 100 ° C., and one constituent component and another constituent component or water or an aqueous solution When the mixture is diluted and used, it can be adjusted to 40 ° C. or lower after mixing. Since the solubility increases when the temperature is high, this is a preferable method for increasing the solubility of the raw material having a low solubility in the metal polishing slurry.

  A raw material in which other components not containing an oxidizing agent are heated and dissolved in the range of room temperature to 100 ° C. is precipitated in the solution when the temperature is lowered. It is necessary to dissolve what is deposited by heating. For this, a means for feeding a heated component solution and a means for stirring the liquid containing the precipitate, feeding the liquid, and heating and dissolving the pipe can be employed. When the temperature of one component containing an oxidant is increased to 40 ° C. or higher, the oxidant may be decomposed. Therefore, the heated component and the oxidation for cooling the heated component When mixed with one component containing an agent, the temperature is set to 40 ° C. or lower.

  In the present invention, as described above, the component of the metal polishing liquid may be divided into two or more parts and supplied to the polishing surface. In this case, it is preferable to divide and supply the component containing an oxide and the component containing an acid. Alternatively, the metal polishing liquid may be a concentrated liquid, and the diluted water may be separately supplied to the polishing surface.

[Polishing pad]
The polishing pad 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 system), a continuous foam (wet foam system), and a two-layer composite (laminated system), and a two-layer composite (laminated system) is particularly preferable. Foaming may be uniform or non-uniform.

  Further, it may contain abrasive grains (for example, ceria, silica, alumina, resin, etc.) used for polishing. 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. The material is preferably non-woven fabric, artificial leather, polyamide, polyurethane, polyester, polycarbonate or the like. In addition, the surface contacting the polishing surface may be subjected to processing such as lattice grooves / holes / concentric grooves / helical grooves.

[Wafer]
The target wafer (object to be polished) to be subjected to CMP with the polishing liquid of the present invention preferably has a diameter of 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 equipment)
An apparatus capable of carrying out the polishing method using the polishing liquid of the present invention is not particularly limited, but examples of commercially available products include Mirra Mesa CMP, Reflexion CMP (manufactured by Applied Materials), FREX200, FREX300 (manufactured by Ebara Corporation), Examples include NPS3301, NPS2301 (Nikon V), A-FP-310A, A-FP-210A (manufactured by Tokyo Seimitsu Co., Ltd.), 2300 TERES (manufactured by Ram Research), Momentum (manufactured by Speedfam IPEC), and the like.

(Average relative motion speed of polishing pad / object to be polished (wafer))
Since the relative motion between the polishing surface of the polishing pad and the surface to be polished is different depending on the part because of the rotational polishing, it is appropriate to represent the average relative motion speed (average relative speed). The average relative speed is obtained as an average value of the relative motion speed in the radial direction of a straight line passing through the center of the surface to be polished.

For example, when both the surface to be polished and the polishing surface are rotating bodies, the distance between the respective rotation centers is set as the center-to-center distance L. The relative motion speed of the surface to be polished on the line connecting the centers is obtained and used as the average relative speed. FIG. 1 is a plan view of a rotary polishing surface including a polishing surface and a surface to be polished for explaining the average relative speed. In FIG. 1, the distance between the center B of the surface to be polished and the center O of the surface to be polished is L [m], the radius of the surface to be polished is Rp [m], the radius of the surface to be polished is Rw [m], and the angular velocity of the surface to be polished is Let ωp [rad / s] and the angular velocity of the surface to be polished be ωw [rad / s].
The relative motion speeds Va, Vb, and Vc at points A, B, and C when Rp> Rw are expressed by the following equations.
A: Va = (L−Rw) * ωp + Rw * ωw
B: Vb = L * ωp
C: Vc = (L + Rw) * ωp−Rw * ωw
In the above manner, the velocity distribution in the radial direction A-C of the surface to be polished is obtained, and the average value obtained by dividing the sum by the number of measurement points is obtained as the average relative motion velocity.

  Hereinafter, the present invention will be described by way of examples. The present invention is not limited to these examples.

(Polishing test)
The conditions of the object to be polished and the polishing apparatus in the polishing test to which the polishing liquid is applied are as follows.
Object to be polished (work): With respect to a commercially available pattern wafer on which a TEOS insulating film, a tantalum barrier metal layer, and a copper-plated wiring layer have been applied, until the excess Cu plating above the insulating layer is completely cleared, A substrate in which a uniform Cu-CMP is performed under the same conditions, and a barrier metal layer is exposed on the surface of the insulating film over the entire wafer surface (commercially available pattern wafer: 854 mask pattern wafer (Sematech))
Polishing pad: IC1400 (Rohm & Haas)
Polishing machine: LGP-612 (Lapmaster)
Holding pressure: 14000Pa
Polishing liquid supply rate: 200 ml / min
Wafer size: 8 inches Relative motion speed of polishing pad / wafer: 1.0 m / sec (average relative motion speed in wafer surface)

(Evaluation methods)
<Liquid stability>
The stability of the polishing liquid was evaluated as follows. The polishing liquid is divided into sample tubes, which are irradiated with laser light, and the intensity of transmitted light is measured. When aggregation is observed in the contained particles, the transmitted light intensity decreases, and when gelling, the intensity becomes almost zero.
The evaluation standard is “◎” for samples that maintain almost the same transmitted light intensity after 6 months compared to the standard solution that maintains a highly dispersed state for at least half a year. Samples that maintained the light intensity were evaluated as “◯”, and samples less than this were evaluated as “x”.

<Removability of barrier metal layer (barrier film clear)>
In addition to visually confirming whether or not the barrier metal layer that must be removed on the insulating film remains on the patterned wafer after the barrier CMP, the four chips from the center to the edge of the wafer are observed with an electron microscope. It confirmed using the X-ray analyzer.
Evaluation device: Ultra-high resolution electron microscope + X-ray analyzer S4800 + Emax (manufactured by Hitachi High-Tech)
The evaluation standard is “○” when a metal element used for the barrier material is not detected when element mapping is performed on the insulating film of the pattern wafer using an X-ray analyzer, and is used for the barrier material. A case where a detection peak of a metallic element appeared was indicated as “x”.

<Dishing>
The height difference generated between the wiring (L) and the space (S) of the L / S = 100 (μm) / 100 (μm) portion on the pattern wafer after the barrier CMP is measured using a step gauge, The measured value was defined as the dishing amount (nm). The measurement location was performed on three equally spaced chips arranged in the radial direction of the pattern wafer, and the average value of these measurements was used.
Evaluation device: Contact level difference measuring device Dektak V320 (Veeco)

(Preparation method of barrier polishing liquid)
Solvent: Ultrapure water Oxidizing agent: Hydrogen peroxide (Wako Pure Chemical Industries, Ltd.): Addition 20g / L
Carboxylic acid compound: (compound shown in Table 1) Addition amount: 0.05 to 0.12 mol / L
Abrasive grains: silicon oxide particles (characteristics such as type and size used in the examples are shown in Table 1)
Addition amount: 5.0% by weight
Heterocyclic compound: (compound shown in Table 1) Addition amount: 0.5 to 0.75 g / L (content with respect to polishing composition: 0.01 to 0.10% by weight)
pH: adjusted as appropriate using acid and alkali so that the pH shown in Table 1 is obtained.

(Examples 1-13, Comparative Examples 1-7)
Based on the above, each polishing liquid was adjusted by changing to carboxylic acid (monocarboxylic acid or dicarboxylic acid), heterocyclic compound and pH shown in Table 1. The electrical conductivity is shown in Table 2. Further, the stability, erosion (barrier film clear), and dishing of the liquid were evaluated by the above-described experimental evaluation method for these adjusted polishing liquids. The results are shown in Table 2.

  From the above results, when the polishing liquids of Examples 1 to 13 are used, the polishing rate of the barrier metal layer and the insulating film layer and the metal wiring layer can be made appropriate, and the occurrence of final steps such as dishing and erosion can be suppressed. Recognize. It can also be seen that the stability of the polishing liquid can be improved.

It is a top view of the rotary polishing surface containing the grinding | polishing surface and to-be-polished surface for demonstrating an average relative speed.

Claims (6)

  A polishing liquid for polishing a barrier material on an insulating material, which is an aqueous solution having a pH of 5.5 to 8.5 containing a dicarboxylic acid compound, and in which silicon oxide particles are dispersed.   The polishing liquid according to claim 1, wherein the electric conductivity of the polishing liquid is 10 mS / cm or less.   The polishing liquid according to claim 1 or 2, further comprising a heterocyclic compound in a range of 0.01 to 0.10% by weight.   The silicon oxide particles are composite particles containing at least colloidal silica having a primary particle diameter in the range of 15 to 70 nm when converted from a specific surface area to a true spherical particle model, or colloidal silica having a primary particle diameter in the range. The polishing liquid according to any one of claims 1 to 3, wherein:   The barrier material is configured to include at least one of tantalum, tantalum nitride, titanium, titanium nitride, tungsten, tungsten nitride, nickel, nickel nitride, ruthenium, and a compound thereof. The polishing liquid according to claim 4.   Furthermore, an oxidizing agent is included, The polishing liquid of any one of Claims 1-5 characterized by the above-mentioned.

Images