JP4448787B2 - Polishing liquid for metal and polishing method - Google Patents

Description

The present invention relates to the manufacture of semiconductor devices, and more particularly to a metal polishing liquid in a wiring process of a semiconductor device and a polishing method using the same.
In particular, the present invention relates to a metal polishing aqueous solution that has a high polishing rate in copper flattening CMP technology and that has good level difference elimination performance (that can realize characteristics with a small dishing amount).

  In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor integrated circuits (hereinafter referred to as LSIs). The chemical mechanical polishing (hereinafter referred to as CMP) method is one of them, and is a technique that is frequently used in the LSI manufacturing process, particularly in the multilayer wiring formation process, planarization of the interlayer insulating film, metal plug formation, and embedded wiring formation. . This technique is disclosed in, for example, Patent Document 1 (US Pat. No. 4,944,836). Recently, in order to improve the performance of LSIs, the use of copper alloys as wiring materials has been attempted. However, it is difficult to finely process the copper alloy by the dry etching method frequently used in the formation of the conventional aluminum alloy wiring. Therefore, a so-called damascene method is mainly employed in which a copper alloy thin film is deposited and embedded on an insulating film in which grooves have been formed in advance, and the copper alloy thin film other than the grooves is removed by CMP to form embedded wiring. . This technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-278822. A general method of metal CMP for copper alloys is to apply a polishing pad on a circular polishing platen (platen), immerse the surface of the polishing pad in a metal polishing solution, and press the surface on which the base metal film is formed. Then, with a predetermined pressure (hereinafter referred to as polishing pressure) applied from the back surface, the polishing platen is rotated, and the metal film on the convex portion is removed by mechanical friction between the polishing liquid and the convex portion of the metal film. is there.

  The metal polishing liquid used in CMP is generally composed of an oxidizing agent and solid abrasive grains, and a metal oxide dissolving agent and a protective film forming agent are further added as necessary. First, it is considered that the basic mechanism is to oxidize the surface of a metal film with an oxidizing agent and scrape the oxidized layer with solid abrasive grains. Since the oxide layer on the metal surface of the recess does not touch the polishing pad so much and the effect of scraping off by the solid abrasive grains does not reach, the metal layer of the projection is removed and the substrate surface is flattened with the progress of CMP. This is disclosed in Non-Patent Document 1 (Journal of Electrochemical Society, Vol. 138, No. 11 (1991), pages 3460 to 3464).

  As a method for increasing the polishing rate by CMP, it is effective to add a metal oxide dissolving agent. It can be interpreted that the metal oxide particles scraped off by the solid abrasive grains are dissolved in the polishing liquid (hereinafter referred to as etching) because the effect of scraping off by the solid abrasive grains is increased. The addition of the metal oxide solubilizer increases the polishing rate by CMP. On the other hand, if the oxide layer on the metal film surface in the recess is also etched (dissolved) and the metal film surface is exposed, the metal film surface is further oxidized by the oxidant. If this is repeated, etching of the metal film in the recesses proceeds. For this reason, a phenomenon that the central portion of the surface of the metal wiring embedded after polishing is depressed like a dish (hereinafter referred to as “dicing”) occurs, and the planarization effect is impaired. In order to prevent this, a protective film forming agent is further added. The protective film forming agent forms a protective film on the oxide layer on the surface of the metal film, and prevents dissolution of the oxide layer in the polishing liquid. This protective film can be easily scraped off by solid abrasive grains, and it is desirable not to decrease the polishing rate by CMP. BTA (benzotriazole) as a metal oxide solubilizer and protective film forming agent consisting of aminoacetic acid or amidosulfuric acid such as glycine to suppress corrosion during dishing and polishing of copper alloys and to form highly reliable LSI wiring There has been proposed a method using a metal-polishing liquid containing bismuth. This technique is described in, for example, Patent Document 3 (Japanese Patent Laid-Open No. 8-83780).

  Patent Document 4 (Japanese Patent Laid-Open No. 2002-222782) includes a metal polishing liquid containing two types of protective film forming agents, and Patent Document 5 (Japanese Patent Laid-Open No. 2001-31953) includes an organic acid that forms a complex with a metal. No abrasive, Patent Document 6 (Japanese Patent Laid-Open No. 2002-299292) is a polishing composition containing heteropolyacetic acid as abrasive particles, and Patent Document 7 (Japanese Patent Laid-Open No. 2003-100216) contains no oxidizing agent. A polishing liquid for metal having a conductivity of 0.5 to 5.0 mS / cm, Patent Document 8 (Japanese Patent Laid-Open No. 2001-144045) has a polishing rate ratio of a metal to its barrier layer of 1 or more, and a barrier layer And a polishing liquid for metal having a polishing rate ratio of the insulating film layer of 10 or more.

US Pat. No. 4,944,836 JP-A-2-278822 JP-A-8-83780 JP 2002-222782 A JP 2001-31953 A JP 2002-299292 A JP 2003-100216 A JP 2001-1444045 A Journal of Electrochemical Society, 1991, Vol. 138, No. 11, pp. 3460-3464

However, since the protective film formation effect of BTA is very high, not only the etching rate but also the polishing rate is significantly reduced. Therefore, there has been a demand for a metal polishing liquid that sufficiently reduces the etching rate and does not decrease the polishing rate by CMP.
By using a water-soluble polymer protective film forming agent, the present invention maintains a high polishing rate by CMP, sufficiently reduces the etching rate, suppresses the occurrence of dishing, and has a highly reliable metal film embedding pattern. A metal polishing liquid and a polishing method are provided.

(1) oxidizing agent, a water-soluble polymer protective film forming agent, an organic acid, and a Rukin genus polishing slurry to contain abrasives, water-soluble polymer protective film forming agent is the structural formula (1) A metal polishing slurry comprising: a repeating unit of:

(R ₁ is, - NH- heterocycle, -O- heterocycle, or, -CH ₂ - Represents a heterocyclic ring,
The heterocyclic ring is substituted or unsubstituted benzotriazole (BTA), benzimidazole, triazole or imidazole. n represents an integer of 2 or more. )

(2) The metal polishing slurry according to (1) above, wherein the water-soluble polymer protective film forming agent has a molecular weight of 500 or more.
(3) The metal according to (1 ) or (2) , wherein the oxidizing agent is at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water. Polishing fluid.
(4) A chemical characterized in that the metal polishing liquid according to any one of the above (1) to (3) is brought into contact with the surface to be polished, and the surface to be polished and the polishing surface are moved relative to each other for polishing. Mechanical polishing method.
Although this invention is invention which concerns on said (1)-(4), hereafter, other matters are also described.

  By using the metal polishing liquid of the present invention as a polishing liquid used for chemical mechanical polishing in the manufacture of semiconductor devices, a significant improvement in the chemical mechanical polishing rate is achieved, and the occurrence of dishing is low. Can be made possible.

Hereinafter, specific embodiments of the present invention will be described.
The metal polishing liquid of the present invention is an aqueous solution containing an oxidizing agent, a water-soluble polymer protective film forming agent, an organic acid, and abrasive grains.
The metal polishing slurry of the present invention may further contain other components, and preferred components include surfactants, water-soluble polymers, and additives.
Each component contained in the metal polishing slurry may be used alone or in combination of two or more.

In addition, among the components added at the time of preparing the concentrate for the metal polishing liquid, the blending amount of water having a solubility in water at room temperature of less than 5% is to prevent precipitation when the concentrate is cooled to 5 ° C. The solubility in water at room temperature is preferably within 2 times, more preferably within 1.5 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 physical concentration operations such as evaporation are performed. It is used in a different way from the meaning of the general terms involved.

That is, 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 when used for polishing, water or an aqueous solution is used. It is diluted and used for polishing. The dilution factor is generally 1 to 20 volume times.
In the present invention, the “metal 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 metal polishing liquid.

  Hereinafter, each component will be described.

[Water-soluble polymer protective film forming agent]
The water-soluble polymer protective film forming agent is a polymer compound that is dissolved in an aqueous polishing liquid and forms a film on the oxidized surface of a metal to be polished during polishing, and has a molecular weight of 500 or more. It is preferable that it is 1000 or more.
Moreover, it is preferable that a polymeric protective film forming agent has 2 or more repeating units (dimer or more), and it is more preferable to have 5 or more repeating units (pentamer or more). Here, the repeating unit means a structure in which two or more of the same structures are bonded.

  It is particularly preferred that the water-soluble polymer protective film forming agent has a repeating unit of the structural formula (1).

R ₁ is —OH, —NH ₂ , an alkyl group, —NH-alkyl group, —O-alkyl group (eg, —OCH ₃ ), allyl group, —NH-allyl group, —O-allyl group, —CH ₂ - allyl group, an aryl group, -NH- aryl, -O- aryl group _{(e.g., -OC 6 H 5), -} CH 2 - aryl group, a heterocyclic, -NH- heterocycle, -O- heterocycle or, -CH ₂ - or a heterocyclic.
n represents an integer of 2 or more.

R ₁ is preferably —NH-alkyl group, —O-alkyl group, —NH-allyl group, —O-allyl group, —NH-aryl group, —O-aryl group (preferably —OC ₆ H ₅ ), -NH-heterocycle or -O-heterocycle.
R ₁ particularly preferably has a heterocyclic ring, and as the heterocyclic ring, substituted or unsubstituted benzotriazole (BTA), benzimidazole, triazole, imidazole, and tolyltriazole are particularly preferable.

For example, specific examples of R ₁ include the following, but are not limited thereto.

The water-soluble polymer protective film forming agent can be synthesized by a known method, but a commercially available product may be used.
For example, a water-soluble polymeric protective film-forming agent having a repeating unit of the structural formula (1) can be obtained by a polymerization method described in Synthesis and application of coating polymers (practical version of coating polymer design in 1993). Can be synthesized. The most general method is solution polymerization, but various methods such as suspension polymerization can be adopted without being limited thereto.

  Synthesis examples of the water-soluble polymer protective film forming agent represented by the following formula (I-1) are shown below.

A 1 L three-necked flask was charged with 500 ml of water, 20.7 g of 5-aminobenzotriazole dihydrochloride and 30 g of sodium hydrogen carbonate, and cooled to 10 ° C. or lower in an ice bath with good stirring. To this solution, 10 g of acrylic acid chloride was slowly added dropwise. After stirring for 1 hour, the temperature was raised to 15 ° C., and the precipitate was separated by filtration. The precipitate was dissolved in 100 ml of dimethylformamide, and 500 ml of hot water was slowly added dropwise with stirring. The resulting precipitate was filtered while hot and washed with water. Vacuum drying gave 11 g of A (yield 59%). Mp 248-253 ° C (decomposition).
Next, 20 ml of acetic anhydride was placed in a 200 ml three-necked flask, and 9.4 g of A was slowly added with good stirring. Thereafter, 4 ml of triethylamine was added, and the temperature was raised to 60 ° C. over 30 minutes. After reacting at 60 ° C. for 2 hours, 100 ml of water was added. The precipitated crystals were collected by filtration and washed with water. 7.3 g of B was obtained (63% yield).

  In a 300 ml three-necked flask, 170 ml of tetrahydrofuran was placed, and 4.6 g of B and 12.8 g of acrylamide were added thereto. The temperature was raised to 60 ° C., 500 mg of 2,2′-azobis (2,4-dimethylvaleronitrile) was added and reacted for 5 hours. The reaction solution was cooled to room temperature, and the precipitate was collected by filtration. The obtained precipitate was put in a beaker, 20 ml of tetrahydrofuran was added and stirred well, and then the precipitate was collected by filtration. Alkaline water (NaOH 5 g + water 100 ml) was added to the precipitate and stirred well. After 3 hours, the reaction was acidified with concentrated hydrochloric acid and the supernatant was discarded. 100 ml of water was added, decanted, 100 ml of water was added, and the pH was adjusted to 10 with 1N KOH aqueous solution. After desalting by dialysis, the solvent was distilled off under reduced pressure, methanol was added, and the mixture was collected by filtration. 4 g of the desired product (I-1) was obtained.

  The addition amount of the water-soluble polymer protective film forming agent is preferably 0.0001 to 5% by mass, more preferably 0.01 to 0.5% by mass in the metal polishing liquid at the time of polishing.

〔Oxidant〕
The metal polishing liquid of the present invention contains a compound (oxidant) that can oxidize a metal to be polished. Examples of the oxidizing agent include hydrogen peroxide, peroxide, nitrate, iodate, periodate, hypochlorite, chlorite, chlorate, perchlorate, persulfate, Bichromate, permanganate, ozone water and silver (II) salt, iron (III) salt are mentioned.
Among these, hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid and ozone water are preferable.

  Examples of iron (III) salts include inorganic iron (III) salts such as iron nitrate (III), iron chloride (III), iron sulfate (III), iron bromide (III), and organic iron (III) salts. Complex salts are preferably used.

  When an organic complex salt of iron (III) is used, examples of complex-forming compounds constituting the iron (III) complex salt include acetic acid, citric acid, oxalic acid, salicylic acid, diethyldithiocarbamic acid, succinic acid, tartaric acid, glycolic acid, glycine , Alanine, aspartic acid, thioglycolic acid, ethylenediamine, trimethylenediamine, diethylene glycol, triethylene glycol, 1,2-ethanedithiol, malonic acid, glutaric acid, 3-hydroxybutyric acid, propionic acid, phthalic acid, isophthalic acid, 3 Aminopolycarboxylic acid and its salt are mentioned other than -hydroxy salicylic acid, 3,5-dihydroxy salicylic acid, gallic acid, benzoic acid, maleic acid, etc. and these salts.

  Aminopolycarboxylic acids and their salts include ethylenediamine-N, N, N ′, N′-tetraacetic acid, diethylenetriaminepentaacetic acid, 1,3-diaminopropane-N, N, N ′, N′-tetraacetic acid, , 2-Diaminopropane-N, N, N ′, N′-tetraacetic acid, ethylenediamine-N, N′-disuccinic acid (racemic), ethylenediamine disuccinic acid (SS), N- (2-carboxylate ethyl) ) -L-aspartic acid, N- (carboxymethyl) -L-aspartic acid, β-alanine diacetic acid, methyliminodiacetic acid, nitrilotriacetic acid, cyclohexanediaminetetraacetic acid, iminodiacetic acid, glycol etherdiaminetetraacetic acid, ethylenediamine 1-N, N'-diacetic acid, ethylenediamine orthohydroxyphenylacetic acid, N, N-bis (2-hydroxybenzyl) ethylenediamine-N, N-divine Like and salts thereof. The kind of the counter salt is preferably an alkali metal salt or an ammonium salt, and particularly preferably an ammonium salt.

  The addition amount of the oxidizing agent is preferably 0.003 mol to 8 mol, more preferably 0.03 mol to 6 mol, and more preferably 0.1 mol to 4 mol in 1 liter of the metal polishing liquid used for polishing. It is particularly preferable to do this. That is, the addition amount of the oxidizing agent is preferably 0.003 mol or more from the viewpoint of sufficient metal oxidation and ensuring a high CMP rate, and is preferably 8 mol or less from the viewpoint of preventing roughening of the polished surface.

〔acid〕
The polishing liquid of the present invention preferably further 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 acids include, in that range, inorganic acids, organic acids, and amino acids.
Examples of the inorganic acid include sulfuric acid, nitric acid, boric acid, phosphoric acid, etc. Among the inorganic acids, phosphoric acid is preferable.
In the present invention, organic acids and amino acids are particularly preferably present, and amino acids are more preferable.
The organic acid is preferably water-soluble. Those selected from the following group are 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.

The amino acid is preferably water-soluble. Those selected from the following group are more suitable.
Glycine, L-alanine, β-alanine, L-2-aminobutyric acid, L-norvaline, L-
Valine, L-leucine, L-norleucine, L-isoleucine, L-alloisoleucine, L-phenylalanine, L-proline, sarcosine, L-ornithine, L-lysine, taurine, L-serine, L-threonine, L-alloin Threonine, L-homoserine, L-tyrosine, 3,5-diiodo-L-tyrosine, β- (3,4-dihydroxyphenyl) -L-alanine, L-thyroxine,

4-hydroxy-L-proline, L-cystine, L-methionine, L-ethionine, L-lanthionine, L-cystathionine, L-cystine, L-cysteic acid, L-aspartic acid, L-glutamic acid, S- (carboxy Methyl) -L-cystine, 4-aminobutyric acid, L-asparagine, L-glutamine, azaserine, L-arginine, L-canavanine, L-citrulline, δ-hydroxy-L-lysine, creatine, L-quinurenin, L- Amino acids such as histidine, 1-methyl-L-histidine, 3-methyl-L-histidine, ergothioneine, L-tryptophan, actinomycin C1, apamin, angiotensin I, angiotensin II and antipine.
In particular, malic acid, tartaric acid, citric acid, glycine, and glycolic acid are preferable in that the etching rate can be effectively suppressed while maintaining a practical CMP rate.

  The amount of acid added is preferably 0.0005 to 0.5 mol, more preferably 0.005 mol to 0.3 mol, in 1 L of the metal polishing liquid used for polishing, and 0.01 mol. It is especially preferable to set it to -0.1 mol. That is, the amount of acid added is preferably 0.5 mol or less from the viewpoint of suppressing etching, and 0.0005 mol or more is preferable for obtaining a sufficient effect.

[Chelating agent]
The metal polishing liquid of the present invention preferably contains a chelating agent (that is, a hard water softening agent) as necessary in order to reduce adverse effects such as mixed polyvalent metal ions.
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-hydroxy Njiru) ethylenediamine -N, N'-diacetic acid, 1,2-dihydroxy-4,6-disulfonic acid.

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

〔Additive〕
Moreover, it is preferable to use the following additives for the metal polishing slurry of the present invention.
Ammonia: alkylamines such as dimethylamine, trimethylamine, triethylamine, propylenediamine, amines such as ethylenediaminetetraacetic acid (EDTA), sodium diethyldithiocarbamate and chitosan; dithizone, cuproin (2,2′-biquinoline), neocuproin (2, Imines such as 9-dimethyl-1,10-phenanthroline), bathocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and cuperazone (biscyclohexanone oxalylhydrazone); benzimidazole-2-thiol, 2- [2- (benzothiazolyl)] thiopropionic acid, 2- [2- (benzothiazolyl)] thiobutyric acid, 2-mercaptobenzothiazole, 1,2,3-triazole, 1,2,4- Triazole, 3-amino-1H-1,2,4-triazole, benzotriazole, 1-hydroxybenzotriazole, 1-dihydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotriazole, 4- Carboxyl-1H-benzotriazole,

4-methoxycarbonyl-1H-benzotriazole, 4-butoxycarbonyl-1H-benzotriazole, 4-octyloxycarbonyl-1H-benzotriazole, 5-hexylbenzotriazole, N- (1,2,3-benzotriazolyl) Azoles such as -1-methyl) -N- (1,2,4-triazolyl-1-methyl) -2-ethylhexylamine, tolyltriazole, naphthotriazole, bis [(1-benzotriazolyl) methyl] phosphonic acid ; Mercaptans such as nonyl mercaptan, dodecyl mercaptan, triazine thiol, triazine dithiol, triazine trithiol, and others, anthranilic acid, aminotoluic acid, quinaldic acid and the like. Among these, chitosan, ethylenediaminetetraacetic acid, L-tryptophan, cuperazone, triazinedithiol, benzotriazole, 4-hydroxybenzotriazole, 4-carboxyl-1H-benzotriazole butyl ester, tolyltriazole, naphthotriazole have high CMP rate and low etching It is preferable for achieving both speeds.

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

[Surfactant and / or hydrophilic polymer]
The metal polishing slurry 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 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-a Sulfonic 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 to 10 g and preferably 0.01 to 5 g in 1 liter of the metal polishing slurry used for polishing. Is more 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, 500-100000 are preferable, and 2000-50000 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 salt, 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 buffer may be an amount that maintains the pH within a preferable range, and is preferably 0.0001 mol to 1.0 mol in 1 L of the polishing liquid used for polishing. More preferably, it is 0.003 mol to 0.5 mol.
The pH of the polishing liquid when used for polishing is preferably 2 to 14, more preferably 3 to 12, and most preferably 3.5 to 8. Within this range, the metal liquid of the present invention exhibits particularly excellent effects.

  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 and pH.

[Abrasive]
The metal polishing liquid of the present invention contains abrasive grains. Examples of preferable abrasive grains include silica (precipitated silica, fumed silica, colloidal silica, synthetic silica), ceria, alumina, titania, zirconia, germania, manganese oxide, silicon carbide, polystyrene, polyacryl, polyterephthalate, and the like. It is done.
The average grain size of the abrasive grains is preferably 5 to 1000 nm, and particularly preferably 10 to 200 nm.
As addition amount of an abrasive grain, it is preferable that an abrasive grain is 0.01-20 mass% with respect to the total mass of the polishing liquid for metals at the time of use, and is the range of 0.05-5 mass%. It is more preferable. 0.01% by mass or more is preferable for obtaining a sufficient effect in improving the polishing rate and reducing variation in the polishing rate within the wafer surface, and 20% by mass or less is preferable because the polishing rate by CMP is saturated.

[Raw metal materials]
In the present invention, the semiconductor to be polished is preferably an LSI having wiring made of copper metal and / or copper alloy, and particularly preferably a copper alloy. Furthermore, the copper alloy containing silver is preferable among copper alloys. The silver content contained in the copper alloy is preferably 40% by mass or less, particularly preferably 10% by mass or less, more preferably 1% by mass or less, and most preferably in the range of 0.0001 to 0.1% by mass. Exhibits excellent effects.

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

[Barrier metal]
In the present invention, it is preferable to provide a barrier layer for preventing the diffusion of copper between the wiring in which the semiconductor is made of copper metal and / or a copper alloy and the 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.

[Polishing method]
The metal polishing liquid is a concentrated liquid, and when used, it is diluted with water to make a working liquid, or each component is mixed in the form of an aqueous solution described in the next section, and water is added if necessary. In some cases, it is used as a working solution after dilution. The polishing method using the metal polishing liquid of the present invention can be applied to any case, and the polishing liquid is supplied to the polishing pad on the polishing surface plate and brought into contact with the surface to be polished to thereby connect the surface to be polished and the polishing pad. This is a polishing method in which polishing is performed by relative movement.
As an apparatus for polishing, there is a general polishing apparatus having a polishing surface plate with a holder for holding a semiconductor substrate having a surface to be polished and a polishing pad attached (a motor etc. capable of changing the number of rotations is attached). Can be used. As the polishing pad, a general nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used, and there is no particular limitation. The polishing conditions are not limited, but the rotation speed of the polishing surface plate is preferably a low rotation of 200 rpm or less so that the substrate does not jump out. The pressure applied to the polishing pad of the semiconductor substrate having the surface to be polished (film to be polished) is preferably ⁵ to 500 g / cm ² in order to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern. Is more preferably 12 to 240 g / cm ² .

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

  As a method of diluting by adding water or an aqueous solution to the concentrated metal polishing liquid, the pipe for supplying the concentrated metal polishing liquid and the pipe for supplying the water or aqueous solution are joined together, mixed, mixed and diluted. There is a method of supplying the polished metal polishing liquid to the 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 the 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 metal 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 and polishing the concentrated metal polishing liquid with water or an aqueous solution, a pipe for supplying the metal 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. This is a method of polishing while supplying to the polishing pad and mixing by the relative movement of the polishing pad and the surface to be polished. Alternatively, there is a method in which a predetermined amount of concentrated metal polishing liquid and water or an aqueous solution are mixed in one container, and then the mixed metal polishing liquid is supplied to a polishing pad for polishing.

According to another polishing method of the present invention, a component to be contained in a metal polishing liquid is divided into at least two components, and when using them, a water or aqueous solution is added to dilute the polishing pad on a polishing platen. The surface to be polished is brought into contact with the surface to be polished, and the surface to be polished and the polishing pad are moved relative to each other for polishing.
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. A method for supplying a diluted metal polishing liquid to a polishing pad. In the above polishing method, one constituent component containing an oxidizing agent is made 40 ° C. or lower, the other constituent components are heated in the range of room temperature to 100 ° C., and one constituent component and another constituent component or water or an aqueous solution When the mixture is diluted and used, it can be adjusted to 40 ° C. or lower after mixing. Since the solubility increases when the temperature is high, this is a preferable method for increasing the solubility of the raw material having a low solubility in the metal polishing slurry.

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

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

〔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 metal polishing liquid of the present invention preferably has a diameter of 200 mm or more, and particularly preferably 300 mm or more. The effect of the present invention is remarkably exhibited when the thickness is 300 mm or more.

Hereinafter, the present invention will be described specifically by way of examples. The present invention is not limited to these examples. The polishing conditions are as follows.
[Polishing conditions]
The polishing substrate and the substrate were rotated while supplying the metal polishing liquid to the polishing pad on the polishing surface plate in the polishing apparatus using a metering pump, and the substrate to be polished was polished under the following polishing conditions. The polishing liquid was prepared in advance before polishing and held in one container (polishing liquid reservoir) and supplied to a metering pump unless otherwise specified. The polishing work was performed using BC-15 manufactured by MTT.

Substrate: Silicon substrate on which a copper film having a thickness of 1000 nm is formed Polishing pad: IC1400 (trade name, manufactured by Rodel)
Polishing pressure: 1.2 (psi)
Relative speed between substrate and polishing surface plate: 1.0 m / min
Metal polishing liquid flow rate: 50 ml / min Polishing time: 60 sec.

(Evaluation item)
[Polishing speed]
The film thickness difference before and after the CMP of the copper film was calculated from the electric resistance value. The film thickness difference measurement was performed using VR-200 manufactured by Kokusai Denki Alpha Co., Ltd.

[Dishing]
Further, in order to evaluate actual CMP characteristics, a trench having a depth of 5000 nm is formed in an insulating layer, a copper film is formed by a known sputtering method, and a silicon substrate embedded by a known heat treatment is used as a base. Went. The planarization characteristics of the substrate after CMP were examined. The level difference was measured using P-15 manufactured by KLA.

[Example 1]
Preparation of Metal Polishing Liquid Material First, 10 parts by mass of glycine, which is a metal oxide solubilizer, and a protective film forming agent represented by structural formula (1), which is a protective film forming agent (R ₁ is a heterocyclic structure shown in Table 1. And 0.03 parts by weight of a weight average molecular weight of about 2000) was added to 600 parts by weight of water and dissolved to obtain a solution A. Next, 250 parts by mass of colloidal silica PL-3 (19.5 mass% aqueous solution) manufactured by Fuso Science Co., Ltd. was dissolved in Solution A to obtain Solution B. The solution B was adjusted to a pH of 7.2 using 25% by mass of ammonia water, and pure water was added to make the total amount 1000 ml, thereby obtaining a metal polishing liquid as a metal polishing liquid material. A polishing test was conducted by adding 30 ml of hydrogen peroxide to 1 L of the polishing liquid. The polishing test was conducted within 10 hours from the addition of hydrogen peroxide.

  The protective film forming agent was synthesized according to the synthesis method described above.

  As shown in Table 1, it was confirmed that the polishing rate was high and the dishing amount was small.

[Example 2]
As a protective film forming agent, a polymer protective film forming agent represented by structural formula (1) (provided that R ₁ has a group (a) having a heterocyclic structure shown in Table 1 and —NH ₂ (b) The test was conducted in the same manner as in Example 1 except that the ratio (a: b) was 5:95 and the weight average molecular weight was about 3000).
It was confirmed that the polishing rate was high and the dishing amount was small.

Example 3
As the protective film forming agent, a polymer protective film forming agent represented by the structural formula (1) (R ₁ is a group having a heterocyclic structure shown in Table 1 and the weight average molecular weight is about 1200) is used. The test was performed in the same manner as in Example 1.
It was confirmed that the polishing rate was high and the dishing amount was small.

Example 4
As the protective film forming agent, a polymer protective film forming agent represented by the structural formula (1) (R ₁ is a group having a heterocyclic structure shown in Table 1 and the weight average molecular weight is about 1500) is used. The test was performed in the same manner as in Example 1.
It was confirmed that the polishing rate was high and the dishing amount was small.

Example 5
As the protective film forming agent, a polymer protective film forming agent represented by the structural formula (1) (R ₁ is a group having a heterocyclic structure shown in Table 1, and the weight average molecular weight is about 2200) is used. The test was performed in the same manner as in Example 1.
It was confirmed that the polishing rate was high and the dishing amount was small.

[Comparative Example 1]
Except for using the polymer protective film forming agent represented by the structural formula (1) (R ₁ is a group having a heterocyclic structure shown in Table 1 and the weight average molecular weight is about 10,000) as the protective film forming agent. The test was performed in the same manner as in Example 1. When the protective film forming agent had a high molecular weight, it was not dissolved in an aqueous medium and became a polymer aqueous dispersion.
Compared with the result of Example 1, the polishing rate was low.

[Comparative Examples 2 to 5]
The test was performed in the same manner as in Example 1 except that the low molecular weight protective film forming agent shown in Table 1 was used as the protective film forming agent.
Compared with the result of Example 1, the dishing amount was large in all cases.

  It can be seen that the metal polishing liquid of the present invention has an excellent performance with a high polishing rate and small dishing.

Claims (4)

Oxidizing agent, a water-soluble polymer protective film forming agent, an organic acid, and a Rukin genus polishing slurry to contain abrasives, repeating units of the water-soluble polymer protective film forming agent is the structural formula (1) A metal-polishing liquid characterized by comprising:

(R ₁ represents —NH-heterocycle, —O-heterocycle, or —CH ₂ -heterocycle,
The heterocycle is a substituted or unsubstituted benzotriazole, benzimidazole, triazole or imidazole. n represents an integer of 2 or more. ) The metal polishing slurry according to claim 1, the molecular weight of the water-soluble polymer protective film forming agent is characterized in that 500 or more. The metal polishing slurry according to claim 1 or 2 , wherein the oxidizing agent is at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water. A chemical mechanical polishing method comprising polishing the metal polishing liquid according to any one of claims 1 to 3 in contact with a surface to be polished and moving the surface to be polished and the polishing surface relative to each other.