JP2007095713A - Polishing liquid for barrier layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a barrier layer polishing liquid capable of reducing dishing while achieving a high polishing rate for a barrier layer metal film.
A polishing liquid for polishing a barrier layer of a semiconductor integrated circuit, the polishing liquid for a barrier layer containing persulfate, colloidal silica, and an amine derivative.
[Selection figure] None

Description

  The present invention relates to a chemical mechanical polishing liquid and a method for producing a semiconductor device using the same. More specifically, the present invention relates to a barrier layer polishing liquid that can achieve barrier polishing in the manufacture of semiconductor devices at a high polishing rate.

In the development of a semiconductor device represented by a semiconductor integrated circuit (hereinafter referred to as LSI), in order to reduce the size and increase the speed, there is a demand for higher density and higher integration by miniaturization and lamination of wiring. LSIs using copper having low wiring resistance as a metal for wiring have been developed, and various techniques such as chemical mechanical polishing (hereinafter referred to as CMP) have been used as techniques for this purpose.
CMP is a technique for flattening the unevenness of the wafer surface caused by lamination. A general method is to attach a polishing pad on a circular polishing platen and immerse the polishing pad surface with a polishing liquid. Then, press the surface of the substrate (wafer) against the pad, apply a predetermined pressure (polishing pressure) from the back side, rotate both the polishing platen and the substrate, and the surface of the substrate is caused by the generated mechanical friction. Flattening.

  A metal polishing liquid used in CMP generally contains abrasive grains (eg, alumina, silica) and an oxidizing agent (eg, hydrogen peroxide). The metal surface is oxidized with an oxidizing agent, and the oxide film is polished. It is thought that it is grind | polishing by removing with a grain.

  However, when CMP is carried out using such a metal polishing liquid, polishing scratches (scratches), a phenomenon in which the entire polishing surface is polished more than necessary (thinning), the polishing metal surface is not flat, only the center. Phenomena that is deeply polished to produce dish-like dents (dishing), insulators between metal wires are polished more than necessary, and the surface of multiple metal wires forms dish-shaped recesses (erosion), etc. May occur. In particular, in recent years, since higher density and higher integration have been achieved, the demand for reducing dishing has been increasing. In recent years, the diameter of wafers during the manufacture of LSIs has increased in order to improve productivity. Currently, the diameter of 200 mm or more is widely used, and the manufacture of 300 mm or more has started. With such an increase in size, the difference in polishing rate between the wafer center and the periphery has increased, and the demand for improvement in in-plane uniformity has increased. Furthermore, recently, there is a demand for a method capable of obtaining a sufficient polishing rate even when polishing is performed under a low pressure so that film peeling does not occur even when an insulating material having low mechanical strength is used.

  In order to solve such a problem, a metal-polishing liquid which does not contain abrasive grains and is composed of hydrogen peroxide / malic acid / benzotriazole / ammonium polyacrylate and water is disclosed (for example, Patent Document 1). reference.). According to this method, although a conductor pattern in which the metal film is left in the concave portion can be obtained, there is a problem that it is difficult to obtain a sufficient polishing rate. Moreover, although the chemical mechanical polishing aqueous dispersion containing an organic compound that suppresses the deterioration of the polishing pad has been disclosed (for example, see Patent Document 2), there is still concern about the dishing phenomenon. As a dishing suppression method, a method is described in which first-stage polishing is first performed at room temperature, and then the system temperature is lowered to perform second-stage polishing to suppress dishing (for example, Patent Documents). 3)), but the process cost is high and the versatility is lacking.

  On the other hand, tungsten and aluminum have been widely used for interconnect structures as wiring metals. However, LSIs using copper, which has lower wiring resistance than these metals, have been developed with the aim of achieving higher performance. As a method for wiring this copper, a damascene method is known (for example, see Patent Document 4). Further, a dual damascene method in which a contact hole and a wiring trench are simultaneously formed in an interlayer insulating film and a metal is embedded in both has been widely used. As a target material for copper wiring, a high-purity copper target of five nines or more has been shipped. However, in recent years, with the miniaturization of wiring aiming at further higher density, it has become necessary to improve the conductivity and electronic characteristics of copper wiring, and accordingly, a copper alloy in which a third component is added to high-purity copper is required. It is also beginning to be considered for use. At the same time, there is a need for high-speed metal polishing means that can exhibit high productivity without contaminating these high-definition and high-purity materials.

  In addition, when copper wiring is used, a diffusion preventing layer called a barrier layer is generally provided between the wiring portion and the insulating layer for the purpose of preventing copper ions from diffusing into the insulating material, which includes TaN, TaSiN, It is made of one layer or two or more layers selected from Ta, TiN, Ti, Nb, W, WN, Co, Zr, ZrN, and CuTa alloy. However, since these barrier materials themselves have conductive properties, the barrier material on the insulating layer must be completely removed to prevent the occurrence of errors such as leakage current. This is achieved by a method similar to bulk polishing (barrier CMP). At the same time, there is a need for high-speed metal polishing means that can exhibit high productivity without contaminating these bulk materials.

For example, a method is disclosed in which a barrier layer metal film can be polished at high speed with a persulfate (see, for example, Patent Document 5). However, there is a problem that dishing increases with high-speed polishing.
JP 2001-127019 A JP 2001-279231 A JP-A-8-83780 JP-A-2-278822 JP-A-6-313164

  The present invention is based on the background of processing the barrier layer metal at a higher speed and with a low dishing in order to increase the CMP speed in order to increase the productivity of the LSI. Accordingly, an object of the present invention is to provide a barrier layer polishing liquid capable of reducing dishing while achieving a high polishing rate for a barrier layer metal film.

  As a result of intensive studies, the present inventor has found that the above problem can be solved by using the following polishing liquid, and has achieved the object. That is, the present invention is as follows.

<1> A polishing liquid for polishing a barrier layer of a semiconductor integrated circuit, which is a polishing liquid for a barrier layer containing persulfate, colloidal silica, and an amine derivative.

<2> The amine derivative is at least one selected from the group consisting of methylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, hydrazine, ethanolamine, piperazine, pyridine, polyamine, and polyallylamine. It is a polishing liquid for barrier layers as described in <1>.

<3> The polishing liquid for a barrier layer according to <1>, wherein the amine derivative is an amino acid having one carboxyl group.

<4> The amino acid is L-alanine, β-alanine, glycylglycine, L-glutamine, L-asparagine, L-arginine, L-phenylalanine, L-tryptophan, tricine, L-lysine, and L-methionine. The polishing liquid for a barrier layer according to <3>, wherein the polishing liquid is at least one selected from the group consisting of:

<5> The barrier layer polishing liquid according to any one of <1> to <4>, wherein the persulfate is ammonium persulfate, sodium persulfate, or potassium persulfate.

<6> The barrier layer polishing slurry according to any one of <1> to <5>, wherein the concentration of the persulfate is 0.001 to 10% by mass.

<7> The polishing liquid for a barrier layer according to any one of <1> to <6>, wherein the concentration of the abrasive particles is 0.001 to 5% by mass.

  With the barrier layer polishing liquid of the present invention, the barrier layer metal film can be polished at a high polishing rate and low dishing.

Hereinafter, specific embodiments of the present invention will be described.
When persulfuric acid is used, it has been known so far that the barrier layer can be polished at a sufficient polishing rate. However, when the barrier layer is polished at a high speed using persulfuric acid, there is a problem that dishing increases. However, in the process leading to the present invention, the present inventors have found that dishing using an amine derivative is unexpectedly reduced. This is probably because the amine derivative adsorbed on the surface to be polished to suppress the progress of dishing.

  In addition, in the description of substituents (atomic groups) in the compounds in the present specification, when neither substituted nor unsubstituted is described, it includes those having no substituent and those having a substituent. is there. For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).

  The polishing liquid of the present invention contains at least a persulfate as a constituent, colloidal silica as an abrasive particle, and an amine derivative. The polishing liquid of the present invention may further contain other components, and preferred components include organic acids, inorganic acids, surfactants, water-soluble polymers, and additives. The above components contained in the polishing liquid may be used alone or in combination of two or more.

Hereinafter, each component will be described.
[Persulfate]
The polishing liquid for a barrier layer of the present invention contains a persulfate. Such persulfate oxidizes the barrier metal.
For example, ammonium persulfate, sodium persulfate, or potassium persulfate is preferably used as the persulfate. From the viewpoint of preventing contamination of the polishing liquid, ammonium persulfate is particularly preferable.

  The amount of persulfate added is preferably 0.001 to 10% by mass, more preferably 0.01 to 10% by mass in the metal polishing liquid used for polishing. It is especially preferable to set it as the mass%. That is, the addition amount of the persulfate is preferably 0.001% by mass or more from the viewpoint of sufficiently oxidizing the barrier metal layer, and is preferably 10% by mass or less from the viewpoint of preventing the polishing surface from being roughened.

[Abrasive particles]
The barrier layer polishing liquid of the present invention contains colloidal silica as polishing particles for polishing the barrier metal.

  The average particle diameter of the abrasive particles contained for the purpose of reducing scratches after polishing of the surface to be polished is preferably 10 to 70 nm, and more preferably 10 to 45 nm.

The concentration of abrasive particles contained for the purpose of reducing scratches after polishing of the surface to be polished is preferably 0.001 to 5% by mass and preferably 0.01 to 3% by mass in the slurry. More preferably.
A commercial item can be used for the colloidal silica used by this invention.

[Amine derivative]
The barrier layer polishing liquid of the present invention contains an amine derivative. The amine derivative may be, for example, an amine such as methylamine or an amino acid having an amino group and a carboxyl group. When the amine derivative in the present invention is an amino acid, it is preferably an amino acid having one carboxyl group.

When the amine derivative in the present invention is an amino acid, it is preferably an amino acid having one carboxyl group.
The amino acid is preferably water-soluble, and those selected from the following group are more suitable. For example, L-alanine, β-alanine, glycylglycine, L-glutamine, L-asparagine, L-arginine, L-phenylalanine, L-tryptophan tricine, L-lysine, and L-methionine are preferable.

  The amines are preferably water-soluble, and those selected from the following group are more suitable. For example, methylamine, ethylamine, butylamine, hexylamine, benzylamine, allylamine, diethylamine, benzylethylamine, triethylamine, ethanolamine, diethanolamine, triethanolamine, 2-amino-1,3-propanediol, morpholine, pyridine, piperazine, It is desirable to include at least one selected from piperidine, amine, hydrazine, ethylenediamine, hexamethylenediamine, polyallylamine and the like. In particular, methylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, hydrazine, ethanolamine, piperazine, pyridine, and polyallylamine are preferable.

  A single type of amine derivative may be added to the polishing slurry for a barrier layer of the present invention, or two or more types may be used in combination. The amine derivative used in the present invention can be synthesized according to a conventional method, or a commercially available product may be used.

  As an added amount of the amine derivative, the total amount is preferably 0.0005 to 5 mol / L, more preferably 0.01 to 0.5 mol / L in 1 L of the polishing liquid used for polishing. Is preferred.

[Passive film forming agent]
The metal polishing liquid of the present invention contains at least one heterocyclic compound as a compound (passive film forming agent) that forms a passive film on the surface of the metal to be polished and suppresses a chemical reaction on the substrate. May be.
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.

  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-H-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.

  The heterocyclic compound 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 0. In 1 L of a metal polishing liquid used for polishing (that is, a metal polishing liquid after dilution when diluted with water or an aqueous solution). 0001-1.0 mol / L is preferable, More preferably, it is 0.0005-0.5 mol / L, More preferably, it is 0.0005-0.05 mol / L.

〔acid〕
The polishing liquid of the present invention preferably contains an acid. The acid here is a compound having a structure different from that of the oxidizing agent for oxidizing the metal, and does not include an acid that functions as the above-mentioned oxidizing agent. The acid here has an action of promoting oxidation, adjusting pH, and buffering agent. Examples of the acid include inorganic acids and organic acids within the range. Examples of the inorganic acid include sulfuric acid, nitric acid, boric acid, phosphoric acid, and carbonic acid. Among inorganic acids, phosphoric acid and carbonic acid are preferable.
In the present invention, an organic acid is preferably present, and an amino acid is more preferable. As the organic acid, one selected from the following group is more suitable. Formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid , N-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, Examples thereof include tartaric acid, citric acid, lactic acid, and salts thereof such as ammonium salt and alkali metal salt, sulfuric acid, nitric acid, ammonia, ammonium salts, or a mixture thereof. Among these, formic acid, malonic acid, malic acid, tartaric acid, and citric acid are suitable for a laminated film including at least one metal layer selected from copper, a copper alloy, and an oxide of copper or a copper alloy. In particular, malic acid, tartaric acid, citric acid, and lactic acid are preferable in that a higher CMP rate can be achieved.

  The addition amount of the acid is preferably 0.0005 mol to 0.5 mol / L, more preferably 0.005 mol to 0.3 mol / L in 1 L of the polishing liquid used for polishing. It is especially preferable to set it as 0.01 mol-0.1 mol / L.

[Chelating agent]
The polishing liquid of the present invention preferably contains a chelating agent (that is, a hard water softening agent) as necessary in order to reduce adverse effects such as mixed polyvalent metal ions. Chelating agents include general water softeners and related compounds that are calcium and magnesium precipitation inhibitors, such as nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, N, N, N-trimethylenephosphonic acid. , Ethylenediamine-N, N, N ′, N′-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-diaminopropanetetraacetic acid, glycol etherdiaminetetraacetic acid, ethylenediamine orthohydroxyphenylacetic acid, ethylenediamine disuccinic acid ( SS form), N- (2-carboxylateethyl) -L-aspartic acid, β-alanine diacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, N , N′-bis (2-hydroxyben Le) ethylenediamine -N, N'-diacetic acid, 1,2-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 0.07 mol in 1 L of a polishing liquid used for polishing. Add to be.

[Surfactant and / or hydrophilic polymer]
The polishing liquid of the present invention preferably contains a surfactant and / or 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 / or hydrophilic polymer to be used, those selected from the following group are suitable.
Examples of the anionic surfactant include carboxylate, sulfonate, sulfate ester salt and phosphate ester salt. As the carboxylate salt, soap, N-acyl amino acid salt, polyoxyethylene or polyoxypropylene alkyl ether carboxyl Acid salt, acylated peptide; as sulfonate, alkyl sulfonate, alkyl benzene and alkyl naphthalene sulfonate, naphthalene sulfonate, sulfosuccinate, α-olefin sulfonate, N-acyl sulfonate; sulfate ester Salts include sulfated oil, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfates, alkyl amide sulfates; phosphate ester salts such as alkyl phosphates, polyoxyethylene or polyoxy B pyrene alkyl allyl ether phosphate can be exemplified.

As cationic surfactant, aliphatic amine salt, aliphatic quaternary ammonium salt, benzalkonium chloride salt, benzethonium chloride, pyridinium salt, imidazolinium salt; carboxybetaine type, aminocarboxylate as amphoteric surfactant And imidazolinium betaine, lecithin, and alkylamine oxide.
Nonionic surfactants include ether type, ether ester type, ester type and nitrogen-containing type. Ether type includes polyoxyethylene alkyl and alkylphenyl ether, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene poly Examples include oxypropylene block polymer, polyoxyethylene polyoxypropylene alkyl ether, ether ester type, glycerin ester polyoxyethylene ether, sorbitan ester polyoxyethylene ether, sorbitol ester polyoxyethylene ether, ester type, Polyethylene glycol fatty acid ester, glycerin ester, polyglycerin ester, sorbitan ester, propylene glycol ester Le, sucrose esters, nitrogen-containing type, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amide, and the like. Moreover, a fluorine-type surfactant etc. are mentioned.

  Furthermore, other surfactants, hydrophilic compounds, hydrophilic polymers and the like include esters such as glycerin ester, sorbitan ester, methoxyacetic acid, ethoxyacetic acid, 3-ethoxypropionic acid and alanine ethyl ester; polyethylene glycol, polypropylene glycol, Polytetramethylene glycol, polyethylene glycol alkyl ether, polyethylene glycol alkenyl ether, alkyl polyethylene glycol, alkyl polyethylene glycol alkyl ether, alkyl polyethylene glycol alkenyl ether, alkenyl polyethylene glycol, alkenyl polyethylene glycol alkyl ether, alkenyl polyethylene glycol alkenyl ether, polypropylene glycol alkyl Ete , Polypropylene glycol alkenyl ethers, alkyl polypropylene glycols, alkyl polypropylene glycol alkyl ethers, alkyl polypropylene glycol alkenyl ethers, alkenyl polypropylene glycols, alkenyl polypropylene glycol alkyl ethers and alkenyl polypropylene glycol alkenyl ethers; alginic acid, pectinic acid, carboxymethylcellulose, curd Polysaccharides such as orchid and pullulan; amino acid salts such as glycine ammonium salt and glycine sodium salt; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid,

Polymethacrylic acid, poly (ammonium methacrylate), poly (methacrylic acid sodium salt), polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, polyacrylic Ammonium acid salt, polyacrylic acid sodium salt, polyamic acid, polyamic acid ammonium salt, polyamic acid sodium salt and polyglyoxylic acid and other salts thereof; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein; methyl Tauric acid ammonium salt, methyl tauric acid sodium salt, methyl sodium sulfate salt, ethylammonium sulfate salt, butylammonium sulfate salt, vinylsulfonic acid sodium salt, 1- Rylsulfonic acid sodium salt, 2-allylsulfonic acid sodium salt, methoxymethylsulfonic acid sodium salt, ethoxymethylsulfonic acid ammonium salt, 3-ethoxypropylsulfonic acid sodium salt, methoxymethylsulfonic acid sodium salt, ethoxymethylsulfonic acid ammonium salt, Examples include sulfonic acids such as 3-ethoxypropylsulfonic acid sodium salt and sulfosuccinic acid sodium salt and amides such as propionamide, acrylamide, methylurea, nicotinamide, succinic acid amide, and sulfanilamide.

  However, when the substrate to be applied is a silicon substrate for a semiconductor integrated circuit or the like, contamination with an alkali metal, an alkaline earth metal, a halide, or the like is not desirable, so an acid or an ammonium salt thereof is desirable. This is not the case when the substrate is a glass substrate or 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 total amount of the surfactant and / or hydrophilic polymer added is preferably 0.001 g to 10 g and more preferably 0.01 g to 5 g in 1 L of a polishing liquid used for polishing. It is particularly preferably 0.1 to 3 g. That is, the addition amount of the surfactant and / or the hydrophilic polymer is preferably 0.001 g or more for obtaining a sufficient effect, and is preferably 10 g or less from the viewpoint of preventing the CMP rate from being lowered. Moreover, as a weight average molecular weight of these surfactant and / or hydrophilic polymer, 500-100,000 are preferable, and 2,000-50,000 are especially preferable.

[Alkaline agent and buffer]
The polishing liquid of the present invention can contain an alkali agent for pH adjustment and further a buffering agent from the viewpoint of suppressing fluctuations in pH, if necessary.

  Alkaline agents and buffering agents include organic ammonium hydroxides such as ammonium hydroxide and tetramethylammonium hydroxide, nonmetallic alkali agents such as alkanolamines such as diethanolamine, triethanolamine, triisopropanolamine, and the like. Alkali metal hydroxides such as sodium, potassium hydroxide and lithium hydroxide, carbonate, phosphate, borate, tetraborate, hydroxybenzoate, glycyl salt, N, N-dimethylglycine salt, leucine Salt, norleucine salt, guanine salt, 3,4-dihydroxyphenylalanine salt, alanine salt, aminobutyrate, 2-amino-2-methyl-1,3-propanediol salt, valine salt, proline salt, trishydroxyaminomethane salt Lysine salt etc. can be used .

  Specific examples of the alkali agent and buffer include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, trisodium phosphate, tripotassium phosphate, diphosphate phosphate. Sodium, dipotassium phosphate, sodium borate, potassium borate, sodium tetraborate (borax), potassium tetraborate, sodium O-hydroxybenzoate (sodium salicylate), potassium O-hydroxybenzoate, 5-sulfo Examples include sodium 2-hydroxybenzoate (sodium 5-sulfosalicylate), potassium 5-sulfo-2-hydroxybenzoate (potassium 5-sulfosalicylate), ammonium hydroxide, and the like.

  Particularly preferred alkali agents are ammonium hydroxide, potassium hydroxide, lithium hydroxide and tetramethylammonium hydroxide.

  The addition amount of the alkaline agent and the buffering agent may be an amount that maintains the pH within a preferable range, and may be 0.0001 to 1.0 mol / L in 1 L of the polishing liquid used for polishing. Preferably it is 0.003 mol-0.5 mol / L. 2-14 are preferable and, as for pH of the polishing liquid at the time of using for grinding | polishing, 3-12 are more preferable. Within this range, the polishing liquid of the present invention exhibits particularly excellent effects.

[Dispersion medium]
As the polishing dispersion medium of the present invention, water alone or water as a main component (in the dispersion medium, 50 to 99% by mass), and a water-soluble organic solvent such as alcohol or glycol as a minor component (1 to 30 mass). %) Can be used. The water is preferably pure water or ion-exchanged water that does not contain macro particles as much as possible. Examples of the alcohol include methyl alcohol, ethyl alcohol, and isopropyl alcohol, and examples of the glycol include ethylene glycol, tetramethylene glycol, diethylene glycol, propylene glycol, and polyethylene glycol. The content of the dispersion medium in the polishing liquid is 75 to 95% by mass, preferably 85 to 90% by mass. 75 mass% or more is preferable from a viewpoint of the supply property to the board | substrate of polishing liquid.

  In the present invention, depending on the adsorptivity and reactivity to the polishing surface, the solubility of the polishing metal, the electrochemical properties of the surface to be polished, the dissociation state of the compound functional group, the stability as a liquid, etc. It is preferable to set the amount, pH, and dispersion medium.

  In addition, it is preferable that the compounding quantity of the thing with the solubility with respect to the solvent in room temperature among the components added at the time of preparation of the concentrate of polishing liquid is less than 2 times the solubility with respect to the solvent at room temperature is 1 More preferably, it is within 5 times. If this addition amount is twice or more, it becomes difficult to prevent precipitation when the concentrate is cooled to 5 ° C.

[Polishing method]
The polishing liquid is a concentrated liquid that is diluted by adding water when used, or mixed in the form of an aqueous solution described in the next section for each component, and diluted by adding water as necessary. In some cases, it may be used as a working solution or 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 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 0.68 to 34.5 kPa, which satisfies the uniformity of the polishing rate within the wafer surface and the flatness of the pattern. Therefore, it is more preferable that it is 3.40-20.7 kPa.

  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. 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 containing 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 polishing liquid to be diluted is the polishing liquid. Use it as a component when polishing. 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 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 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 a polishing pad 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 uniformity of the polishing rate within the wafer surface and the flatness of the pattern.

  As a method of diluting the concentrated polishing liquid with water or an aqueous solution and polishing, 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 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 oxidizing agent is one component (A), an acid, an additive, a surfactant, and water are one component (B), and when they are used, the component (A) 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 component containing an additive that is difficult to dissolve is mixed with another component, a mixing path is lengthened to ensure a dissolution time, and then a pipe for 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. The diluted polishing liquid is supplied to the 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 of the polishing liquid.

  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 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 acid. Alternatively, the polishing liquid may be a concentrated liquid, and diluted water may be separately supplied to the polishing surface.

〔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 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.

[Barrier metal]
In the present invention, the object to be polished is a barrier layer provided between a semiconductor wiring and an interlayer insulating film. As the barrier layer, a low-resistance metal material is preferable, and TiN, TiW, Ta, TaN, W, and WN are particularly preferable, and Ta and TaN are particularly preferable.
The polishing liquid of the present invention polishes the metal used for semiconductor wiring and the metal used for the barrier layer to smooth the surface. While polishing and removing the barrier metal, the metal used for the wiring is also polished at the same time. In general, the wiring metal has a higher polishing rate, which causes problems such as dishing and erosion. However, the polishing liquid of the present invention has a good balance between the polishing rate of the barrier metal and the wiring metal. Therefore, problems such as dishing are unlikely to occur.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

<Example 1>
The polishing liquid shown below was prepared, and the polishing test was conducted and evaluated.

(Preparation of polishing liquid)
・ Ammonium persulfate (oxidant) 30g / L
・ L-alanine (amine derivative, manufactured by Wako Pure Chemical Industries, Ltd.) 6 g / L
・ Colloidal silica (abrasive grains, manufactured by Fuso Chemical Industries) 10 g / L
・ Pure water is added and the total volume is 1000mL
・ PH (adjusted with ammonia water and sulfuric acid) 7.0

(Evaluation methods)
Under the following conditions, the slurry was supplied onto the polishing cloth of the polishing surface plate of the polishing apparatus, and the metal film was polished by relatively moving the polishing surface plate and the base while pressing the base against the polishing cloth.

-Base: A silicon oxide film is patterned by a photolithography process and a reactive ion etching process to form wiring grooves and connection holes having a width of 0.09 to 100 μm and a depth of 600 nm, and a thickness of 20 nm by a sputtering method. After forming a Ta film of 50 nm in thickness by a sputtering method, a wafer on which a copper film having a total thickness of 1000 nm was formed by a plating method was cut into 4 × 4 cm and used. Further, a wafer in which the copper film was separately polished with slurry until the Ta surface appeared was used as a base wafer (the initial steps of the used wafer were all 10 nm or less).
Table rotation speed: 50 rpm
-Head rotation speed: 50 rpm
Polishing pressure: 168 hPa
・ Polishing pad: Product number IC-1400 manufactured by Rodel Nitta Co., Ltd.
・ Slurry supply rate: 50 ml / min

-Evaluation of dishing-
The polishing was completed when all the Ta surfaces were removed in the polishing. The processed wafer was measured for a step of 100 μm / 100 μm line / space using a stylus type level difference meter. Here, dishing refers to the final step after polishing the barrier layer.

-Measurement of polishing rate-
In the above polishing, the time until all Ta surfaces were removed was measured.

<Examples 2-26 and Comparative Examples 1-3>
In the same manner as in Example 1, using the compounds shown in Table 2, the polishing liquids of Examples 2-28 and Comparative Examples 1-3 were prepared and subjected to a polishing test. Here, when the protective film forming material was used, it was added to 1 mg of the polishing liquid so as to be 500 mg. The results are shown in Tables 1 and 2.

  According to the results of Tables 1 and 2, in the slurries of Examples 1 to 28 in which at least one oxidizing agent selected from persulfates, colloidal silica as an abrasive particle, and an amine derivative were added, the barrier was After polishing the metal layer, the dishing was low and the polishing rate was fast. On the other hand, in Comparative Examples 1 to 5 that do not contain an amine derivative, it can be seen that dishing proceeds greatly.

Claims (7)

  A polishing liquid for polishing a barrier layer of a semiconductor integrated circuit, the polishing liquid for a barrier layer comprising persulfate, colloidal silica, and an amine derivative.   The amine derivative is at least one selected from the group consisting of methylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, hydrazine, ethanolamine, piperazine, pyridine, polyamine, and polyallylamine. The polishing liquid for barrier layers as described.   The polishing liquid for a barrier layer according to claim 1, wherein the amine derivative is an amino acid having one carboxyl group.   The amino acid is selected from the group consisting of L-alanine, β-alanine, glycylglycine, L-glutamine, L-asparagine, L-arginine, L-phenylalanine, L-tryptophan, tricine, L-lysine, and L-methionine. The polishing liquid for a barrier layer according to claim 3, wherein the polishing liquid is at least one selected.   The polishing liquid for a barrier layer according to any one of claims 1 to 4, wherein the persulfate is ammonium persulfate, sodium persulfate, or potassium persulfate.   The polishing liquid for barrier layers according to any one of claims 1 to 5, wherein a concentration of the persulfate is 0.001 to 10 mass%.   7. The barrier layer polishing liquid according to claim 1, wherein the concentration of the abrasive particles is 0.001 to 5 mass%.