JP2007173370A - Polishing solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing solution which can provide the optimal polishing speed and polishing selectivity for a metal interconnection material/barrier metal material/insulation material, during the polishing of the barrier metal material which is conducted following the bulk polishing of the metal interconnection material in the manufacture of a semiconductor device, and thereby can reduce dishing and which never turns into a gel during long time storage and has a superior dispersion stability of a solid content. <P>SOLUTION: This polishing solution is for polishing the barrier metal material on an interlayer insulation material. It contains silicon oxide particles, at least one kind of carboxylic acid compound selected among a group of tricarboxylic acid compounds and tetracarboxylic acid compounds, and water, and has a pH value ranging between 8.0 and 10.5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing liquid used for manufacturing a semiconductor device, and more particularly to a polishing liquid suitably used for polishing a barrier metal material in planarization in a wiring process in the manufacturing 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 embedded metal wiring, etc., and smoothing of a substrate, extra metal thin film at the time of wiring formation Removal or removal of an excess barrier layer on the insulating film can be performed.

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 metal wiring material for an interlayer insulating film is used. In order to prevent the diffusion of metal and to improve the adhesion of the metal wiring material, a layer (barrier metal layer) made of a barrier metal material such as Ta, TaN, Ti, or TiN is formed in advance. It has been broken.

In order to form each wiring layer, first, CMP (hereinafter referred to as metal film CMP) for removing excess metal wiring material deposited by plating or the like is performed in one or more stages, and then In general, CMP (hereinafter referred to as “barrier metal CMP”) for removing the barrier metal material (barrier metal) exposed on the surface is generally performed.
However, there is a problem that the metal wiring CMP causes the metal wiring portion to be overpolished, so-called dishing, 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. Is required. That is, in the barrier metal CMP, when the polishing rate of the insulating material constituting the barrier metal and the interlayer insulating film is relatively low compared to the metal wiring material, the metal wiring portion is polished faster, and the dishing and the result As a result, erosion occurs. For this reason, it is desirable that the polishing rate of the barrier metal or the insulating material is appropriately high. In addition to the advantage of increasing the throughput of barrier metal CMP, in practice, dishing often occurs due to metal film CMP. For the above-mentioned reasons, the polishing rate of barrier metal and insulating material is increased. This is also desirable in that it is required to be relatively high.

Further, various studies have been made on the polishing liquid used in CMP as follows.
For example, Patent Document 1 discloses a CMP polishing agent and a polishing method that are intended to perform high-speed polishing with almost no polishing scratches. Patent Document 2 discloses a polishing composition with improved cleaning performance in CMP and A polishing method and, further, Patent Document 3 proposes a polishing composition that prevents aggregation of abrasive grains.
However, even in the various polishing liquids as described above, the polishing rate ratio between the barrier metal and the insulating material and the metal wiring material should be adjusted to an appropriate selection ratio so that the final steps such as dishing and erosion can be made as small as possible. Has become an issue.
JP 2003-17446 A JP 2003-142435 A JP 2000-84832 A

The objects of the present invention made in view of the above problems are as follows.
That is, an object of the present invention is to provide an optimal polishing rate and polishing selection for a metal wiring material / barrier metal material / insulating material in the polishing of a barrier metal material that is performed following the bulk polishing of the metal wiring material in the manufacture of a semiconductor device. An object of the present invention is to provide a polishing liquid in which the ratio can be adjusted, dishing can be reduced, gelation does not occur even when stored for a long period of time, and the solid content is excellent in dispersion stability.

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 metal material polishing liquid, and have achieved the object.
That is, the present invention is as follows.

<1> A polishing liquid for polishing a barrier metal material on an interlayer insulating material,
It contains silicon oxide particles, at least one carboxylic acid compound selected from the group consisting of tricarboxylic acid compounds and tetracarboxylic acid compounds, and water, and has a pH in the range of 8.0 to 10.5. A characteristic polishing liquid.

<2> The polishing liquid according to <1>, wherein the electrical conductivity is 17 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 mass.

<4> Any one of <1> to <3>, wherein the silicon oxide particles are colloidal silica having a primary particle diameter in a range of 15 to 80 nm when converted from a specific surface area to a true spherical particle model. The polishing liquid according to item 1.

<5> The barrier metal material is at least one selected from the group consisting of tantalum, tantalum nitride, titanium, titanium nitride, tungsten, tungsten nitride, nickel, nickel nitride, ruthenium, ruthenium nitride, and a titanium-tungsten alloy. The polishing liquid according to any one of <1> to <4>, wherein the polishing liquid is configured to include.

<6> The polishing liquid according to any one of <1> to <5>, further comprising an oxidizing agent.

According to the present invention, in the manufacture of a semiconductor device, in the polishing of the barrier metal material performed following the bulk polishing of the metal wiring material, the optimum polishing rate and polishing selectivity for the metal wiring material / barrier metal material / insulating material are increased. The polishing liquid can be adjusted, dishing can be reduced, gelation does not occur even when stored for a long period of time, and a solid dispersion having excellent dispersion stability can be provided.
By using the above polishing liquid, a semiconductor device having a wiring layer with few final steps such as dishing and erosion can be obtained.

Hereinafter, specific embodiments of the polishing liquid of the present invention will be described.
The polishing liquid of the present invention is a polishing liquid for polishing a barrier metal material, and includes, as essential components, at least one carboxylic acid compound selected from the group consisting of a tricarboxylic acid compound and a tetracarboxylic acid compound, and water. It is characterized by including these.
In addition, by setting the pH of the polishing liquid in the range of 8.0 to 10.5, and more preferably by setting the electric conductivity to 17 mS / cm or less, the solid matter contained in the polishing liquid can be obtained in a short time. Occurrence of a phenomenon such as agglomeration and, if it is remarkable, gelation is suppressed, and a stable dispersion state can be maintained for a long period of time.
The cause of solid aggregation that occurs when the electrical conductivity is high is that the ionic strength of the polishing liquid is increased, so that the electric double layer of the solid particles contained is compressed and the particles are easily accessible. This is probably because of this. Therefore, it is preferable to maintain the electric conductivity in the above range from the viewpoint of the dispersion stability of the solid content in the polishing liquid.
In addition, electric conductivity can be adjusted with the addition amount of the said carboxylic acid compound, and the addition amount of pH adjusters, such as an acid and an alkali.

Further, the lower limit of the electrical conductivity of the polishing liquid of the present invention is preferably 0.1 mS / cm, taking into account the effective concentration of the additive, and in the range of 0.1 to 1.5 mS / cm. More preferably.
Here, the electrical conductivity in the present invention can be easily measured by an EC meter (CM-60G manufactured by Toa DKK).

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 generally involve physical concentration operations such as evaporation. The term is used in a different way from the meaning of common terms.
Hereinafter, each component contained in the polishing liquid of the present invention will be described.

[Tricarboxylic acid compound and tetracarboxylic acid compound]
Specific examples of the tricarboxylic acid compound and tetracarboxylic acid compound used in the present invention include citric acid, propane-1,2,3-tricarboxylic acid, aconitic acid, diphenylsulfonetetracarboxylic acid, trimellitic acid, trimesic acid, Hemimellitic acid, merophanic acid, planitic acid, pyromellitic acid, biphenyltetracarboxylic acid and the like are preferable.
The tricarboxylic acid compound and the tetracarboxylic acid compound can be synthesized by a known method, but commercially available products may be used.

  In the present invention, two types of tricarboxylic acid compounds and tetracarboxylic acid compounds having different structures can be used in combination. Thus, when two types of carboxylic acid compounds having different structures are used in combination, the combination ratio can be arbitrarily selected as a mass ratio, generally in the range of 100/1 to 1/100. However, it is preferably in the range of 10/1 to 1/10.

  In the present invention, the addition amount of the tricarboxylic acid compound and the tetracarboxylic acid compound as described above refers to the polishing liquid when used for polishing as a total amount (that is, the diluted polishing liquid when diluted with water or an aqueous solution). In the subsequent 1 L of “polishing liquid for use in polishing”, it is preferably 0.0005 to 3 mol, more preferably 0.01 to 0.5 mol.

[Silicon oxide particles]
The polishing liquid of the present invention contains silicon oxide particles as abrasive particles (abrasive grains). Here, the silicon oxide particles include particles made of silicon oxide and composite particles containing these particles.
Examples of composite particles containing silicon oxide particles (hereinafter sometimes referred to as silicon oxide composite particles) include core-shell-like particles in which the surfaces of core particles made of other materials are coated with silicon oxide particles, and core particles Examples include those with silicon oxide particles attached to the surface, or composed of a plurality of materials, one of which is contained in a plurality of particles made of either material. As described above, it can be produced by applying a well-known method for forming silicon oxide particles by hydrolysis of alkoxysilane.

Thus, both the silicon oxide particles and the silicon oxide composite particles used as the abrasive particles preferably have a primary particle diameter in the range of 15 to 80 nm when converted from a specific surface area by the BET method to a true spherical particle model. The primary particle size is preferably colloidal silica, and composite particles containing at least such primary particle size colloidal silica can also be preferably used.
Here, the primary particle diameter when converted from the specific surface area to the true spherical particle model can be calculated by the following relational expression. When primary particles are regarded as ideal spheres, the relationship represented by the following formula 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 obtained from the specific surface area and density. The density can be easily determined by, for example, a commercially available pycnometer.

Abrasive particles containing silicon oxide can be obtained by well-known manufacturing methods.
As a wet manufacturing method of metal oxide particles, for example, a method in which colloidal particles are obtained by a method of hydrolyzing a metal alkoxide as a starting material is known. Specifically, in an aqueous alkali solution mixed with alcohol, methyl silicate is dropped at a certain rate to cause hydrolysis, and after colloidal silica is passed through the period of grain growth and the period when grain growth is stopped by quenching. There is a method of manufacturing.
In addition, a method for producing colloidal particles using an alkoxide such as aluminum or titanium is also known. 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 oxide particles, a method is known in which fumed particles are obtained by introducing a metal chloride into an oxyhydrogen flame and oxidizing the dechlorinated metal. Furthermore, the metal or alloy desired to be contained in the target substance is pulverized into a powder, which is put into an oxygen flame containing a combustion-supporting gas, and a continuous reaction is caused by the heat of oxidation of the metal, A method for obtaining fine oxide particles has also been put into practical use. Particles produced by these combustion methods are amorphized because they experience high heat during the manufacturing process, and generally have a higher solid density because there are fewer impurities such as hydroxyl groups inside compared to wet particles. Furthermore, the density of hydroxyl groups on the surface is also low.

In the present invention, the silicon oxide particles may be used alone or in combination of two or more.
The content of silicon oxide particles (abrasive particles) contained in the polishing liquid is appropriately selected according to the purpose, but is generally preferably 0.01 to 20% by mass, and preferably 0.1 to 10%. More preferably, it is mass%.

Thus, in addition to the above-mentioned carboxylic acid compound and silicon oxide particles, the polishing liquid of the present invention can be obtained by using water (for example, ultrapure water).
The polishing liquid of the present invention preferably contains each component contained in a known CMP polishing liquid in addition to these essential components.
These components will be described sequentially.

[Immobilized film forming agent]
The polishing liquid of the present invention contains at least one heterocyclic compound as a compound (passivating film forming agent) that forms a passive film on the metal surface to be polished.
Here, the “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.
The heteroatom 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, 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.

  In addition, as for the heterocyclic ring serving as the mother nucleus, the number of members of the heterocyclic ring of the heterocyclic compound 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 5 to 7, particularly preferably 5. When it has a condensed ring, the number of rings is 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.

Next, substituents that the heterocyclic ring may have will be described.
Examples of the substituent that can be introduced into the heterocyclic ring include the following. However, it is not limited to these.
That is, for example, a halogen atom, an alkyl group (a linear, branched or cyclic alkyl group, which may be a polycyclic alkyl group such as a bicycloalkyl group or an active methine group), an alkenyl group, an alkynyl group Group, aryl group, amino group and heterocyclic group.
Further, two or more of the plurality of substituents may be bonded to each other to form a ring. For example, an aromatic ring, an aliphatic hydrocarbon ring, a heterocyclic ring, or the like may be formed, or these may be further combined. Thus, a polycyclic fused ring may be formed. Specific examples of the ring formed include a benzene ring, naphthalene ring, anthracene ring, pyrrole ring, furan ring, thiophene ring, imidazole ring, oxazole ring, and thiazole ring.

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 compound in this invention may be used independently and may be used together 2 or more types.
In addition, the heterocyclic compound in the present invention can be synthesized according to a conventional method, or a commercially available product may be used.

  The total amount of the heterocyclic compound added in the present invention is preferably in the range of 0.01 to 0.10% by mass, more preferably 0.03%, based on the polishing liquid used for polishing. It is the range of -0.10 mass%, More preferably, it is the range of 0.04-0.08 mass%.

〔Oxidant〕
The polishing liquid of the present invention preferably contains a compound (oxidant) that can oxidize 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.
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 addition amount of the oxidizing agent can be adjusted by the dishing amount at the initial stage of the barrier metal CMP. When the amount of dishing at the initial stage of the barrier metal CMP is large, that is, when it is not desired to polish the metal wiring material so much in the barrier metal CMP, it is desirable to add a small amount of oxidizing agent, and the amount of dishing is sufficiently small. When it is desired to polish the metal wiring material at a high speed, it is desirable to increase the amount of the oxidizing agent added.
As described above, it is desirable to change the addition amount of the oxidizing agent depending on the dishing state in the initial stage of the barrier metal CMP, but it is usually preferable to set the amount to 0.01 mol to 1 mol in 1 L of the polishing liquid used for polishing. 0.05 mol to 0.6 mol is particularly preferable.

The polishing liquid of the present invention may further contain other components. Preferred components include pH adjusters, chelating agents, surfactants, water-soluble polymers, and additives.
Each of these components may be used alone or in combination of two or more.

[PH adjuster]
The polishing liquid of the present invention needs to have a pH of 8.0 to 10.5, preferably in the range of pH 8.0 to 9.5. The polishing liquid of the present invention exhibits an excellent effect when the pH is in this range. Therefore, in order to adjust the pH of the polishing liquid of the present invention to a preferable range, a pH adjusting agent such as an alkali / acid or a buffering agent is used.
Alkali / acid, buffering agents include ammonia; ammonium hydroxide; organic ammonium hydroxide such as tetramethylammonium hydroxide; nonmetallic alkaline agents such as alkanolamines such as diethanolamine, triethanolamine, 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 such as trisodium phosphate; boric acid Preferred examples include salts, tetraborate, hydroxybenzoate; and the like.
Particularly preferred alkaline agents are ammonia, ammonium hydroxide, potassium hydroxide, lithium hydroxide, and tetramethylammonium hydroxide.

  The addition amount of the alkali / acid or buffering agent may be an amount that maintains the pH within a preferable range as long as it is equal to or less than the above-described electrical conductivity value. In 1 L of a polishing liquid used for polishing, It is preferable to set it as 0.0001 mol-1.0 mol, and it is more preferable to set it as 0.003 mol-0.5 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.
Examples of chelating agents include general water softeners and related compounds that are calcium and magnesium precipitation inhibitors, such as diethylenetriaminepentaacetic acid, N, N, N-trimethylenephosphonic acid, ethylenediamine-N, N, N. ', N'-tetramethylenesulfonic acid, ethylenediamine orthohydroxyphenylacetic acid, ethylenediamine disuccinic acid (SS form), N- (2-carboxylateethyl) -L-aspartic acid, β-alanine diacetic acid, 1-hydroxyethylidene- Examples include 1,1-diphosphonic acid, N, N′-bis (2-hydroxybenzyl) ethylenediamine-N, N′-diacetic acid, 1,2-dihydroxybenzene-4,6-disulfonic acid, and the like.

These chelating agents may be used in combination of two or more as required.
In the present invention, the addition amount of the chelating agent may be an amount sufficient to sequester metal ions such as mixed multivalent metal ions. For example, 0.0003 mol in 1 L of a polishing liquid used for polishing Add to 0.07 mol.

[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 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 salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, and imidazolinium salts.
Examples of amphoteric surfactants include carboxybetaine type, aminocarboxylate, imidazolinium betaine, lecithin, and alkylamine oxide.
Nonionic surfactants include ether type, ether ester type, ester type, and nitrogen-containing type.
Moreover, a fluorine-type surfactant etc. can also be used.

  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.

In addition, it is desirable that the above-mentioned substances are contained in the form of an acid or an ammonium salt thereof from the point of being free from contamination by alkali metals, alkaline earth metals, halides and the like.
Preferred specific examples of the surfactant and the hydrophilic polymer include cyclohexanol, ammonium polyacrylate, polyvinyl alcohol, succinic acid amide, polo vinyl pyrrolidone, polyethylene glycol, and polyoxyethylene polyoxypropylene block polymer. .

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.
In addition, these surfactants and hydrophilic polymers can be added in amounts that do not impair the effects of the present invention, and are usually 0.003 to 60 g in 1 L of a polishing liquid used for polishing. It is preferable to add so that it becomes.

〔Additive〕
Moreover, it is also preferable to use the following additives for the polishing liquid of the present invention.
That is, alkylamines such as dimethylamine, trimethylamine, triethylamine, propylenediamine, and amines such as sodium diethyldithiocarbamate and chitosan; dithizone, cuproin (2,2′-biquinoline), neocuproine (2,9-dimethyl-1,10) -Imine such as phenanthroline), bathocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), cuperazone (biscyclohexanone oxalylhydrazone); nonyl mercaptan, dodecyl mercaptan, triazine thiol, triazine dithiol, triazine tri Mercaptans such as thiol; and the like.

  Among these, chitosan, 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 in 1 L of a polishing liquid used for polishing, from the viewpoint of suppressing etching and preventing a decrease in CMP rate. More preferably, the amount is 0.2 mol, and particularly preferably 0.005 mol to 0.1 mol.

  In the present invention, among the components added at the time of preparing the concentrate of the polishing liquid, the blending amount of water having a solubility in water at room temperature of less than 5% prevents precipitation when the concentrate is cooled to 5 ° C. Thus, it is preferably within 2 times the solubility in water at room temperature, and more preferably within 1.5 times.

  The polishing liquid of the present invention is generally suitable for polishing a barrier metal layer for preventing diffusion of copper and / or a copper alloy, which is present between a metal wiring made of copper and / or a copper alloy and an interlayer insulating film. ing.

[Barrier metal materials]
In the present invention, the barrier metal material constituting the barrier metal layer of the object to be polished (target to be polished) is generally preferably a low-resistance metal material, and in particular, tantalum (Ta), tantalum nitride (TaN), titanium (Ti). , Titanium nitride (TiN), tungsten (W), tungsten nitride (WN), nickel (Ni), nickel nitride (NiN), ruthenium (Ru), ruthenium nitride (RuN), and titanium-tungsten alloy (Ti-W) It is preferable that at least one selected from the group consisting of:
Among these, TiN, Ti-W, Ta, TaN, W, and WN are preferable, and Ta and TaN are particularly preferable.

[Metal wiring materials]
In the present invention, the metal wiring material constituting the metal wiring of the object to be polished (the object to be polished) is preferably a copper metal and / or a copper alloy, more preferably a copper alloy, and further contains silver among the copper alloys. A copper alloy is preferred.
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, most preferably in the range of 0.00001 to 0.1% by mass. Exhibits excellent effects.

[Polishing method]
The polishing liquid of the present invention is 1. 1. A concentrated liquid which 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. It may be prepared as a working solution.
The polishing method using the polishing liquid of the present invention can be applied to any case, supplying the polishing liquid to the polishing pad on the polishing surface plate, and bringing the polishing surface and the polishing pad into relative motion by bringing them into contact with the surface to be polished. This is a polishing method for polishing.

As an apparatus used for polishing, a holder for holding a semiconductor substrate (wafer) having a surface to be polished, a polishing plate with a polishing pad attached (a motor etc. capable of changing the number of rotations), A general polishing apparatus having the following 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 integrated circuit substrate having the surface to be polished (film to be polished) is preferably ⁵ to 500 g / cm ² , and the uniformity of the polishing rate within the wafer surface and the flatness of the pattern are improved. In order to satisfy, it is more preferable that it is 12-240 g / cm < ² >.

During polishing, a polishing liquid 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. After the polishing, the semiconductor substrate 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.
The supply rate of the polishing liquid to the polishing pad is preferably 10 to 1000 ml / min, more preferably 170 to 800 ml / min, in order to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern.

In the present invention, the 1. When diluting the concentrated solution as in the above method, the following aqueous solutions can be used. The aqueous solution is water containing at least one of an oxidizing agent, an organic acid, an additive, 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.
Thus, when the concentrate is diluted with an aqueous solution and used, components that are difficult to dissolve can be added later in the form of an aqueous solution, so that a more concentrated concentrate can be prepared.

  In addition, as a method of diluting by adding water or an aqueous solution to the concentrated liquid, 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 with 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 filler 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 employed.

  Further, as a method of polishing while diluting the concentrated liquid 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 for polishing.

As another polishing method using the polishing liquid of the present invention, 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. There is a method of polishing by supplying the upper polishing pad and bringing the surface to be polished into contact with the surface to be polished and moving the surface to be polished and the polishing pad relative to each other.
For example, an oxidant is used as the component (A), an organic acid, an additive, a surfactant, and water are used as the component (B). A component (B) can be diluted and used.
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 an organic acid, an additive, and a surfactant are used. An agent and water are used as the component (B), and when they are used, water or an aqueous solution is added to dilute the component (A) and the component (B).

In the case of the above 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 connecting to one pipe and mixing in the pipe. In this case, it is possible to connect two pipes and then connect another pipe. Specifically, this 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 water or aqueous solution pipe is further coupled. .
As described above, the other mixing methods are as follows. The three pipes are directly guided to the polishing pad and mixed by the relative movement of the polishing pad and the surface to be polished, or the three components are mixed in one container. There is a method of supplying diluted polishing liquid to the polishing pad from there.

  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, when diluting by adding water or an aqueous solution, the liquid temperature can be set to 40 ° C. or lower. 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 constituent component containing an oxidizing agent is increased to 40 ° C. or higher, the other constituent components that have been heated may be decomposed. When two components 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 polishing surface. 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 diluted water may be separately supplied to the polishing surface.

〔pad〕
In the present invention, 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.
Furthermore, the pad 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, epoxy 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.

(Polishing equipment)
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.

Hereinafter, the present invention will be described by way of examples. The present invention is not limited to these examples.
(Polishing test)
-Work: Excess copper plating above the interlayer insulation film is completely removed from commercially available pattern wafers with TEOS interlayer insulation film, tantalum barrier metal layer, and copper-plated metal wiring. Until now, obtained by performing uniform metal CMP under the same conditions, a substrate in which the barrier metal layer is exposed on the surface of the interlayer insulating film over the entire surface of the wafer. Commercially available pattern wafer: 854 mask pattern wafer (Sematech)
・ Polishing pad: IC1400 (Rohm & Haas)
・ Polisher: LGP-612 (Lapmaster)
・ Pressing pressure: 14000 Pa
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 the wafer surface)

(Evaluation methods)
<Removability of barrier metal layer>
The polishing test is performed as described above, and it is visually confirmed whether or not the barrier metal layer that must be removed on the interlayer insulating film remains on the pattern wafer after the barrier metal CMP. The four chips from the center to the edge were confirmed by elemental mapping using an electron microscope observation and an X-ray analyzer.
As an evaluation apparatus, an ultra-high resolution electron microscope + X-ray analyzer S4800 + EMAX (Hitachi High-Tech) was used.
The evaluation standard is “◯” if the metal element used for the barrier metal layer is not detected when element mapping is performed on the interlayer insulating film of the pattern wafer using an X-ray analyzer. When the detection peak of the metal element used appeared, it was set as “x”.

<Evaluation of dishing (measurement of level difference in metal wiring part)>
The polishing test is performed as described above, and the height difference generated between the metal wiring of L / S = 100 μm / 100 μm and the space on the pattern wafer after the barrier metal CMP is measured using a step gauge, and dishing is performed. The amount was measured.
Measurement was performed on three equally spaced chips arranged in the radial direction of the pattern wafer, and the measurement result value was the average of these values.
A contact-type level difference measuring device Dektak V320 (Veeco) was used as the level difference measuring device.

<Dispersion stability of solid content in polishing liquid>
The dispersion stability of the solid content in the polishing liquid was evaluated by the following method.
That is, the polishing liquid was divided into sample tubes, irradiated with laser light, and the intensity of transmitted light was measured. At this time, when aggregation is observed in the solid particles contained in the polishing liquid, the transmitted light intensity decreases, and when the gel is gelled, the intensity becomes almost zero.
The evaluation standard is “◎” for samples that maintain almost the same transmitted light intensity at the end of 6 months against the standard solution that maintains a highly dispersed state for at least half a year. Samples that maintained the transmitted light intensity were evaluated as “◯”, and samples that did not satisfy this were evaluated as “x”.

[Examples 1-11, Comparative Examples 1-5]
(Preparation of polishing liquid for barrier metal materials)
・ Solvent: Ultra pure water ・ Residual amount ・ Oxidizing agent: Hydrogen peroxide (manufactured by Wako Pure Chemical Industries, Ltd.) ・ ・ ・ ・
Carboxylic acid compound: Compounds shown in Table 1 below: 0.2 mol / L
・ Abrasive particles: Silicon oxide particles: 5.0% by mass
Heterocyclic compound: Compound shown in Table 1 below ... 0.6 g / L
Here, the silicon oxide particles used as the abrasive particles were colloidal silica, and the primary particle diameter when converted from a specific surface area to a true spherical particle model was 71 nm.
The pH of the polishing liquid was appropriately adjusted using nitric acid and ammonia so as to have the values shown in Table 1 below.

Using the carboxylic acid compounds and heterocyclic compounds shown in Table 1, and further adjusting the pH shown in Table 1 using acids and alkalis, the polishing liquids of Examples 1 to 11 and Comparative Examples 1 to 5 were prepared. did.
The electrical conductivity of each polishing liquid was measured with an EC meter (CM-60G manufactured by Toa DKK), and the results are also shown in Table 1.
Using these polishing liquids, the removal properties of the barrier metal layer, dishing (steps in the metal wiring portion), and solid dispersion stability in the polishing liquid were evaluated by the above evaluation methods.
The results are shown in Table 1.

As is apparent from Table 1, it contains silicon oxide particles, a tricarboxylic acid compound or a tetracarboxylic acid compound, and water, the pH is adjusted in the range of 8.0 to 10.5, and the electrical conductivity is further increased. The polishing liquid for the barrier metal material adjusted to show 17 mS / cm or less (the polishing liquid of the example) is excellent in the removal property of the barrier metal, and the dishing is reduced as compared with the polishing liquid of the comparative example. I understand that. Moreover, it turns out that the polishing liquid of an Example is excellent in the dispersion stability of solid content, and excellent in storage stability, without gelatinizing.
In addition, in the polishing liquid of Comparative Example 1, since the abrasive grains aggregated because the pH was high and the electrical conductivity was high, the dispersion stability of the solid content was poor. As a result, the polishing test itself could not be performed, and the barrier metal The removal property could not be evaluated.
Moreover, since the polishing liquid of Comparative Example 2 did not contain the carboxylic acid compound or organic acid in the present invention, the polishing hardly progressed (the polishing rate was too low), and the polishing test was not completed. For this reason, the removal property of the barrier metal is poor, and furthermore, evaluation for dishing cannot be performed.

Claims (6)

A polishing liquid for polishing a barrier metal material on an interlayer insulating material,
It contains silicon oxide particles, at least one carboxylic acid compound selected from the group consisting of tricarboxylic acid compounds and tetracarboxylic acid compounds, and water, and has a pH in the range of 8.0 to 10.5. A characteristic polishing liquid.   The polishing liquid according to claim 1, wherein the electric conductivity is 17 mS / cm or less.   The polishing liquid according to claim 1, further comprising a heterocyclic compound in a range of 0.01 to 0.10% by mass.   4. The colloidal silica according to claim 1, wherein the silicon oxide particles are colloidal silica having a primary particle diameter in a range of 15 to 80 nm when converted from a specific surface area to a true spherical particle model. The polishing liquid described in 1.   The barrier metal material includes at least one selected from the group consisting of tantalum, tantalum nitride, titanium, titanium nitride, tungsten, tungsten nitride, nickel, nickel nitride, ruthenium, ruthenium nitride, and titanium-tungsten alloy. The polishing liquid according to any one of claims 1 to 4, wherein the polishing liquid is provided.   The polishing liquid according to claim 1, further comprising an oxidizing agent.