JP4448519B2 - Polishing liquid for metal and polishing method - Google Patents

Description

  The present invention relates to a metal polishing liquid and a polishing method particularly suitable for use in polishing in a wiring formation process of a semiconductor device.

  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 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. is there. This technique is disclosed in, for example, 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 a groove is formed in advance, and a copper alloy thin film other than the groove is removed by CMP to form a buried wiring. . This technique is disclosed, for example, in JP-A-2-278822.

  A general method of metal CMP is to apply a polishing pad on a circular polishing platen (platen), immerse the polishing pad surface with a metal polishing liquid, and press the surface on which the metal film of the substrate is formed. The polishing platen is rotated in a state where a predetermined pressure (hereinafter referred to as polishing pressure) is applied from the back surface, 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.

  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. It is considered that the basic mechanism is to first oxidize the surface of the metal film by oxidation 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 does not have the effect of scraping off by the solid abrasive grains, the metal layer of the projection is removed and the substrate surface is flattened with the progress of CMP. Details thereof are disclosed in pages 3460 to 3464 of Journal of Electrochemical Society, Vol. 138, No. 11 (published in 1991).

  If the metal oxide particles scraped by the solid abrasive grains are dissolved in the polishing liquid by the metal oxide dissolving agent, it is considered that the effect of scraping by the solid abrasive grains increases. However, if the oxide layer on the surface of the metal film in the recess is also dissolved (hereinafter referred to as etching) and the metal film surface is exposed, the surface of the metal film is further oxidized by the oxidizing agent, and if this is repeated, the etching of the metal film in the recess proceeds. Therefore, there is a concern that the flattening effect is impaired. In order to prevent this, a protective film forming agent is further added. It is important to balance the effects of the metal oxide solubilizer and the protective film forming agent. The oxide layer on the surface of the metal film is not etched so much, and the scraped oxide layer particles are efficiently dissolved, and the polishing rate by CMP is reduced. Is desirable to be large.

  In this way, by adding a metal oxide solubilizer and a protective film forming agent to add a chemical reaction effect, the CMP rate (that is, the polishing rate by CMP) is improved and the surface of the metal layer to be CMP is damaged (damage). Can also be obtained.

  However, when forming a buried wiring by CMP using a conventional metal polishing liquid containing solid abrasive grains, (1) the central portion of the surface of the buried metal wiring is isotropically corroded and looks like a dish. (2) Occurrence of scratches (scratches) derived from solid abrasive grains, (3) Cleaning to remove solid abrasive grains remaining on the substrate surface after polishing Problems such as complicated process and (4) cost increase due to solid abrasive grains themselves and waste liquid treatment arise.

  In order to suppress the corrosion of the copper alloy during dishing and polishing and to form a highly reliable LSI wiring, a metal oxide solubilizer and benzotriazole (hereinafter referred to as BTA) made of aminoacetic acid or amide sulfuric acid such as glycine are used. A method using a metal-containing polishing liquid is proposed. This technique is described in, for example, JP-A-8-83780.

  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, it is desired to use a protective film forming agent in the metal polishing liquid that sufficiently reduces the etching rate and does not decrease the CMP rate.

  The present invention provides a metal polishing liquid and a polishing method capable of forming a highly reliable embedded pattern of a metal film while sufficiently reducing an etching rate and maintaining a high CMP rate.

  The metal polishing liquid of the present invention comprises an oxidizing agent for oxidizing metal, a metal oxide solubilizer, a first protective film forming agent, a second protective film forming agent different from the first protective film forming agent, and water. Containing.

  The protective film forming agent forms a protective film on the metal surface.

  The first protective film forming agent is preferably at least one selected from nitrogen-containing compounds such as ammonia, alkylamines, amino acids, imines and azoles and salts thereof, and mercaptans, glucose and cellulose. These first protective film forming agents are compounds that form a protective film by forming physical adsorption and / or chemical bonds on the surface of the metal film.

  Examples of the second protective film forming agent include alcohols (that is, compounds having an alcoholic hydroxyl group), phenols (that is, compounds having a phenolic hydroxyl group), esters, ethers, polysaccharides, amino acid salts, polycarboxylic acids and salts thereof, At least one selected from vinyl polymers, sulfonic acids and salts thereof, aromatic amines, amides, azo compounds and molybdenum compounds is preferred. These second protective film forming agents are compounds that assist the first protective film forming agent to form a protective film.

  The oxidizing agent is preferably at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water.

  The metal oxide solubilizer is preferably at least one selected from organic acids, ammonium salts thereof and sulfuric acid.

  In the present invention, the concentration of the first protective film forming agent necessary for exhibiting the effect of suppressing the etching rate to 10 nm / min or less without including the second protective film forming agent of the protective film forming agent. By adding a second protective film forming agent to A, the first protective film forming agent having a concentration lower than the concentration A can be contained to exhibit an effect of suppressing the etching rate to 10 nm / min or less. A polished metal polishing liquid is provided. That is, in this case, the second protective film forming agent is a compound that reduces the amount of the first protective film forming agent added to suppress the etching rate to 10 nm / min or less.

  The polishing method of the present invention is a polishing method in which the metal film on the surface of the object to be polished is removed by polishing in the metal polishing liquid of the present invention described above. For the metal film to be removed, copper, copper alloy, copper oxide, copper alloy oxide and the like are suitable. Therefore, in the present invention, a metal film composed of a laminated film including at least one metal layer selected from copper, a copper alloy, a copper oxide, and a copper alloy oxide is obtained using the above-described metal polishing liquid. A polishing method is provided in which at least a part of the metal film is removed by the polishing step.

  In the present invention, a polishing liquid in which the etching rate is sufficiently reduced while maintaining the CMP rate by combining the first and second protective film forming agents having different properties and a polishing method using the same are provided. As the first protective film forming agent, one that easily forms a chelate complex with copper, for example, ethylenediaminetetraacetic acid, benzotriazole, or the like is used. These metal surface protective film forming effects are extremely strong. For example, when 0.5 wt% or more is contained in the metal polishing liquid, the copper alloy film is not etched or even CMPed.

  On the other hand, the present inventors use a second protective film forming agent different from the first protective film forming agent in combination, so that the etching is sufficiently low even if the addition concentration of the first protective film forming agent is low. It was found that the speed can be suppressed. Moreover, it has been found that when such a polishing liquid is used, a preferable characteristic is obtained that the CMP rate does not decrease so much even if the etching rate decreases. In addition, it has been found that by using the first protective film forming agent and the second protective film forming agent in combination, it is possible to perform polishing at a practical CMP rate without including solid abrasive grains in the polishing liquid. It was. This is considered to be due to the fact that the polishing by the friction of the polishing pad was manifested against the effect of the cutting by the friction of the conventional solid abrasive grains.

  It has been found that a preferable planarization effect can be obtained if the etching rate to be suppressed can be suppressed to 10 nm / min or less. If the decrease in the CMP rate is acceptable, the lower etching rate is desirable, and if it can be suppressed to 5 nm / min or less, for example, about 50% excess CMP (1.5 times the time required for removing the metal film by CMP) Even if CMP is performed, dishing does not become a problem. Further, if the etching rate can be suppressed to 1 nm / min or less, dishing does not cause a problem even if 100% or more of excess CMP is performed.

  Note that the etching rate in this specification refers to a metal film (formed by sputtering) on the surface of the object to be polished when the object to be polished is immersed in the polishing liquid and the polishing liquid is stirred at a liquid temperature of 25 ° C. and a stirring speed of 100 rpm. This is the rate at which the difference in metal film thickness before and after immersion is calculated from the electrical resistance value and is divided by the immersion time.

The CMP rate (namely, chemical mechanical polishing rate) is a metal film on the surface of the object to be polished under the conditions that the polishing pressure is 210 g / cm ² , the relative speed between the object to be polished and the polishing platen is 36 m / min, and the liquid temperature is 25 ° C. It is the speed | rate which grind | polished (copper film formed by sputtering), calculated | required by converting the metal film thickness difference before and behind grinding | polishing from an electrical resistance value, and divided this by processing time.

  According to the present invention, unlike the polishing liquid using only the first protective film forming agent, the CMP flattening can be performed by friction with a much softer polishing pad without relying on strong mechanical friction due to the solid abrasive grains. Can be realized.

  Further, in the present invention, polishing using the metal polishing liquid of the present invention polishes a substrate on which a metal film containing copper, copper alloy (copper / chromium, etc.) is formed and filled on a substrate having a recess on the surface. A method is provided. When such a substrate is subjected to CMP using the polishing liquid of the present invention, the metal film on the convex portion of the substrate is selectively CMPed, and the metal film is left in the concave portion to obtain a desired conductor pattern. In the polishing liquid of the present invention, the polishing scratches can be drastically reduced because CMP does not need to contain substantially solid abrasive grains, and CMP proceeds by friction with a polishing pad that is much mechanically softer than solid abrasive grains. .

  The metal-polishing liquid of the present invention contains an oxidizing agent, a metal oxide dissolving agent, a first protective film forming agent, a second protective film forming agent, and water as essential components. Solid abrasive grains need not be substantially contained, but can also be used.

  Next, specific examples of each component contained in the metal polishing liquid of the present invention will be described.

Examples of the metal oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), nitric acid, potassium periodate, hypochlorous acid, and ozone water. When the substrate is a silicon substrate including an integrated circuit element, contamination by alkali metal, alkaline earth metal, halide, etc. is not desirable, so an oxidizing agent that does not contain non-volatile components is desirable. Of these oxidizing agents listed above, hydrogen peroxide is most preferred. However, when the substrate to be applied is a glass substrate or the like that does not include a semiconductor element, an oxidizing agent that includes a nonvolatile component may be used.

The metal oxide solubilizer is preferably water-soluble. Water-soluble metal oxide solubilizers include 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, Organic acids such as maleic acid, phthalic acid, malic acid, tartaric acid, citric acid,
Ammonium salts of these organic acids and ammonium salts such as ammonium persulfate, ammonium nitrate, ammonium chloride,
Examples include inorganic acids such as sulfuric acid and chromic acid, and ammonia complexes. These may be used alone or in combination.

  Of these, formic acid, malonic acid, malic acid, tartaric acid, and citric acid are suitable for the laminated film including a metal layer made of copper, copper alloy, copper oxide, and / or copper alloy oxide. These are preferable in that a balance with the first and second protective film forming agents described later can be easily obtained. In particular, malic acid, tartaric acid, and citric acid are preferable in that the etching rate can be effectively suppressed while maintaining a practical CMP rate.

As the first protective film forming agent,
ammonia;
Alkylamines such as dimethylamine, trimethylamine, triethylamine, propylenediamine, and amines such as ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTA), sodium diethyldithiocarbamate, and chitosan;
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-allothreonine, 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- (carboxymethyl) -L-cysteine, 4-aminobutyric acid, L Asparagine, L-glutamine, azaserine, L-arginine, L-canavanine, L-citrulline, δ-hydroxy-L-lysine, creatine, L-quinurenin, L-histidine, 1-methyl-L-histidine, 3-methyl Amino acids such as L-histidine, ergothioneine, L-tryptophan, actinomycin C1, apamin, angiotensin I, angiotensin II and antipine;
Dithizone, cuproin (2,2′-biquinoline), neocuproin (2,9-dimethyl-1,10-phenanthroline), bathocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and cupelazone ( Imines such as biscyclohexanone oxalyl hydrazone);
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-hexylbenzotriazo N- (1,2,3-benzotriazolyl-1-methyl) -N- (1,2,4-triazolyl-1-methyl) -2-ethylhexylamine, tolyltriazole, naphthotriazole, bis [ Azoles such as (1-benzotriazolyl) methyl] phosphonic acid;
Mercaptans such as nonyl mercaptan, dodecyl mercaptan, triazine thiol, triazine dithiol, triazine trithiol; and
And sugars such as glucose and cellulose. These may be used alone or in appropriate combination.

  Among these, chitosan, ethylenediaminetetraacetic acid, L-tryptophan, cuperazone, triazinedithiol, benzotriazole, 4-hydroxybenzotriazole, 4-carboxyl-1H-benzotriazole butyl ester, tolyltriazole and naphthotriazole have high CMP rates. This is preferable for achieving both a low etching rate. In particular, benzotriazole and its derivatives are suitable. Examples of the benzotriazole derivative include the azoles described above.

As the second protective film forming agent,
1-propanol, 2-propanol, 2-propyn-1-ol, allyl alcohol, ethylene cyanohydrin, 1-butanol, 2-butanol, (S)-(+)-2-butanol, 2-methyl-1-propanol, t-butyl alcohol, perfluoro-t-butyl alcohol, crotyl alcohol, 1-pentanol, 2,2-dimethyl-1-propanol, 2-methyl-2-butanol, 3-methyl-1-butanol, S- Amyl alcohol, 1-hexanol, 4-hydroxy-4-methyl-2-pentanone, 4-methyl-2-pentanol, cyclohexanol, DL-3-hexyl alcohol, 1-heptanol, 2-ethylhexyl alcohol, (S) -(+)-2-octanol, 1-octanol, DL-3-octi Alcohol, 2-hydroxybenzyl alcohol, 2-nitrobenzyl alcohol, 3,5-dihydroxybenzyl alcohol, 3,5-dinitrobenzyl alcohol, 3-fluorobenzyl alcohol, 3-hydroxybenzyl alcohol, 4-fluorobenzyl alcohol, 4- Hydroxybenzyl alcohol, benzyl alcohol, m- (trifluoromethyl) benzyl alcohol, m-aminobenzyl alcohol, m-nitrobenzyl alcohol, o-aminobenzyl alcohol, o-hydroxybenzyl alcohol, p-hydroxybenzyl alcohol, p-nitro Benzyl alcohol, 2- (p-fluorophenyl) ethanol, 2-aminophenethyl alcohol, 2-methoxybenzyl alcohol, 2-methyl-3-nitro Benzyl alcohol, 2-methylbenzyl alcohol, 2-nitrophenethyl alcohol, 2-phenylethanol, 3,4-dimethylbenzyl alcohol, 3-methyl-2-nitrobenzyl alcohol, 3-methyl-4-nitrobenzyl alcohol, 3 -Methylbenzyl alcohol, 4-fluorophenethyl alcohol, 4-hydroxy-3-methoxybenzyl alcohol, 4-methoxybenzyl alcohol, 4-methyl-3-nitrobenzyl alcohol, 5-methyl-2-nitrobenzyl alcohol, DL-α -Hydroxyethylbenzene, o- (trifluoromethyl) benzyl alcohol, p- (trifluoromethyl) benzyl alcohol, p-aminophenethyl alcohol, p-hydroxyphenylethanol, p-methylbenzyl alcohol Call and S- pheneticillin alcohols such as chill alcohol;
Phenols such as 4-methylphenol, 4-ethylphenol and 4-propylphenol;
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 ether, polypropylene glycol alkenyl ether, alkyl polypropylene glycol, alkyl polypropylene glycol alkyl ether, alkyl polypropylene glycol alkenyl ether, alkenyl poly Propylene glycol, ethers such as alkenyl polypropylene glycol alkyl ethers and alkenyl polypropylene glycol alkenyl ethers;
Polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, curdlan and pullulan;
Amino acid salts such as glycine ammonium salt and glycine sodium salt;
Polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), poly Polycarboxylic acids such as acrylic acid, polyacrylamide, amino polyacrylamide, ammonium polyacrylate, sodium polyacrylate, polyamic acid, ammonium polyamic acid, sodium polyamic acid and polyglyoxylic acid and salts thereof;
Vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone and polyacrolein;
Methyl taurate ammonium salt, methyl taurate sodium salt, methyl sodium sulfate salt, ethyl ammonium sulfate, butyl ammonium sulfate, vinyl sulfonic acid sodium salt, 1-allyl sulfonic acid sodium salt, 2-allyl sulfonic acid sodium salt, methoxy Methylsulfonic acid sodium salt, ethoxymethylsulfonic acid ammonium salt, 3-ethoxypropylsulfonic acid sodium salt, methoxymethylsulfonic acid sodium salt, ethoxymethylsulfonic acid ammonium salt, 3-ethoxypropylsulfonic acid sodium salt, sulfosuccinic acid sodium salt, etc. Sulfonic acids and salts thereof;
Aromatic amines such as aniline, N, N-dimethylaniline and benzylamine;
Amides such as propionamide, acrylamide, methylurea, nicotinamide, succinic acid amide, phenylacetic acid amide, pyridine-4-carboxamide, N, N′-dibenzyl-L-tartaric acid amide and sulfanilamide;
1,1′-azobis (cyclohexane-1-carbonitrile), 1,1′-azobis (1-acetoxy-1-phenylethane), 2,2′-azobis (2,4-dimethylvaleronitrile), 2, 2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (isobutyric acid) dimethyl, 2,2′-azobis (isobutyronitrile), 2- [2- (3 , 5-Dibromopyridyl) azo] -5-dimethylaminobenzoic acid, 4,4′-azobis (4-cyanovaleric acid), 4,4′-azoxyanisole, azoxymethane, azobenzene, azoxybenzene, azodicarbonamide , Diisopropyl azodicarboxylate, di (t-butyl) azodicarboxylate, phenazine, malachite green, methyl orange, Congo-red and crystals Azo compounds such as Ioretto; and,
And molybdenum compounds such as disodium molybdate (VI) dihydrate and hexaammonium hexamolybdate (VI) tetrahydrate tetrahydrate. These may be used alone or in appropriate combination.

  In the case where the substrate to be applied is a silicon substrate for a semiconductor integrated circuit or the like, since contamination by alkali metal, alkaline earth metal, halide, etc. is not desirable, an acid or its ammonium salt is desirable. However, this is not the case when the substrate is a glass substrate or the like.

  Among these, 2-methyl-3-nitrobenzyl alcohol, polypropylene glycol, polyaspartic acid, polymalic acid, polyacrylic acid, polymethacrylic acid, ammonium polyacrylate, polyammonium methacrylate, polyamic acid, ammonium polyamic acid, poly Acrylamide, sodium methyltaurate, benzylamine, nicotinamide, sulfanilamide, Congo-red, hexamolybdenum (VI) hexaammonium tetrahydrate are preferred to achieve both a high CMP rate and a low etching rate, Polyacrylic acid, polymethacrylic acid, polyamic acid, ammonium polyacrylate, polyammonium methacrylate, ammonium polyamic acid and polyacrylamide are preferred.

  The metal film to which the present invention is applied is a laminated film containing at least one selected from copper, a copper alloy, a copper oxide, and a copper alloy oxide (hereinafter collectively referred to as a copper alloy).

  The present invention also provides a metal polishing liquid having a CMP rate of 100 nm / min or more and an etching rate of 10 nm / min or less. The polishing liquid having such characteristics is realized for the first time by the present invention, and includes a metal oxidizing agent, a metal oxide solubilizer, and water, and further includes a first protective film forming agent and the first protective film forming agent. This can be achieved by combining and combining a second protective film forming agent different from the protective film forming agent.

  Next, combinations of the first protective film forming agent and the second protective film forming agent that can be used will be shown as a first protective film forming agent / second protective film forming agent. These combinations are merely examples, and the present invention is not limited to these. Other combinations may be used as necessary.

  Examples of combinations in which the CMP rate is 100 nm / min or more and the etching rate is 10 nm / min or less include cuperazone / polymalic acid, cuperazone / polyaspartic acid, cuperazone / polyacrylamide, L-tryptophan / polyacrylamide, L-tryptophan / Ammonium polyacrylate, L-tryptophan / polymalic acid, benzotriazole / polyacrylamide, benzotriazole / ammonium polyacrylate, naphthotriazole / polymalic acid, naphthotriazole / 2-methyl-3-nitrobenzyl alcohol, triazine dithiol / polyasparagine Acid, triazine dithiol / polyacrylamide and the like.

  In addition, as combinations where the CMP rate is 100 nm / min or more and the etching rate is 1 nm / min or less, cuperazone / polyacrylamide, L-tryptophan / polyacrylamide, L-tryptophan / ammonium polyacrylate, benzotriazole / polyacrylamide, Examples include benzotriazole / ammonium polyacrylate, naphthotriazole / polymalic acid, triazine dithiol / polyaspartic acid, triazine dithiol / polyacrylamide, and the like.

  Examples of the combination in which the CMP rate is 250 nm / min or more and the etching rate is 10 nm / min or less include cuperazone / polymalic acid.

  Below, the compounding quantity of each component is demonstrated.

  The blending amount of the oxidizing agent component is 0.003 mol to 0.7 mol with respect to 100 g of the total amount of the oxidizing agent, the metal oxide dissolving agent, the first protective film forming agent, the second protective film forming agent, and water. Is preferable, 0.03 mol to 0.5 mol is more preferable, and 0.2 mol to 0.3 mol is particularly preferable. If the blending amount is less than 0.003 mol, metal oxidation is insufficient and the CMP rate is low, and if it exceeds 0.7 mol, the polished surface tends to be rough.

  The compounding amount of the metal oxide solubilizer component in the present invention is 0 to 0.005 mol with respect to 100 g of the total amount of the oxidizing agent, metal oxide solubilizer, first protective film forming agent, second protective film forming agent and water. It is preferable to be 0.00005 mol to 0.0025 mol, and it is particularly preferable to be 0.0005 mol to 0.0015 mol. If this amount exceeds 0.005 mol, it tends to be difficult to suppress etching.

  The blending amount of the first protective film forming agent is 0.0001 mol to 0.05 mol with respect to 100 g of the total amount of the oxidizing agent, the metal oxide solubilizer, the first protective film forming agent, the second protective film forming agent, and water. It is preferable to set it as 0.0003 mol-0.005 mol, and it is especially preferable to set it as 0.0005 mol-0.0035 mol. If this amount is less than 0.0001 mol, it tends to be difficult to suppress etching, and if it exceeds 0.05 mol, the CMP rate tends to be low.

  The blending amount of the second protective film forming agent is 0.001 to 0.3 with respect to 100 g of the total amount of the oxidizing agent, the metal oxide solubilizer, the first protective film forming agent, the second protective film forming agent, and water. % By weight is preferable, 0.003% by weight to 0.1% by weight is more preferable, and 0.01% by weight to 0.08% by weight is particularly preferable. If this blending amount is less than 0.001% by weight, the combined effect with the first protective film forming agent tends not to appear in etching suppression, and if it exceeds 0.3% by weight, the CMP rate tends to decrease. .

  Although the mechanism of action manifestation in the polishing liquid and polishing method of the present invention is not clear, the combined use of the first and second protective film forming agents suppresses etching, but against friction caused by the polishing pad. It is presumed that CMP proceeds without functioning as a metal surface protective film.

  In general, the degree of occurrence of polishing flaws in CMP depends on the particle size, particle size distribution and shape of solid abrasive grains, and the reduction in film thickness (hereinafter referred to as erosion) and the deterioration of the planarization effect due to the abrasion of the insulating film are Also, depending on the particle size of the solid abrasive grains and the physical properties of the polishing pad, when the metal film, especially the copper film surface, is treated with BTA, the dishing of the metal film depends on the hardness of the polishing pad and the chemical properties of the polishing liquid. It is thought that it depends. That is, hard solid abrasive grains are necessary for the progress of CMP, but are not desirable for improving the planarization effect in CMP and the integrity of the CMP surface (there is no damage such as polishing scratches). It can be seen that the planarization effect actually depends on the characteristics of the polishing pad that is softer than the solid abrasive grains.

  Thus, the present invention is considered to be extremely desirable for CMP of a copper alloy, and hence for the formation of a buried pattern using it, in that CMP can proceed without solid abrasive grains.

  The first protective film forming agent has an action of forming a strong protective film on the metal surface. For example, when the surface of a copper alloy film is exposed to a liquid containing BTA, a polymer having a structure of Cu (I) BTA or Cu (II) BTA as a main skeleton by reaction of copper (Cu) or an oxide thereof with BTA. It is thought that a complex compound film is formed. This film is quite strong, and when a metal polishing liquid containing 0.5% by weight of BTA is used, even if solid abrasive grains are contained in the polishing liquid, it is generally hardly polished.

  On the other hand, when the metal polishing liquid is prepared by using only the second protective film forming agent alone without using the first protective film forming agent, it becomes particularly difficult to suppress the etching rate, and the protective effect is not sufficient.

  In this way, the first protective film forming agent and the second protective film forming agent have different functions, and different types of protective films are formed depending on the type of protective film forming agent. In the present invention, by combining the first and second protective film forming agents described above, it is possible to achieve both the suppression of the etching rate and the maintenance of the CMP rate, and also eliminate the need for strong friction due to the solid abrasive grains. It is based on knowledge.

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

Examples 1-12, Comparative Examples 1-5
<< Method for preparing polishing liquid >>
A solution in which 70 parts by weight of water is added to 0.15 parts by weight of DL-malic acid (special reagent grade) and dissolved, and 0.2 parts by weight of the first protective film forming agent is dissolved in 0.8 parts by weight of methanol. After that, 0.05 parts by weight of a second protective film forming agent was further added, and finally 33.2 parts by weight of hydrogen peroxide (special grade, 30% aqueous solution) was added to obtain a metal polishing liquid. . In addition, Table 1 shows the protective film forming agents used in each Example and Comparative Example.

  Next, the object to be polished was polished using the obtained polishing liquid. The polishing conditions are as follows.

<Polishing conditions>
Substrate to be polished: silicon substrate on which a 1 μm thick copper film is formed Polishing pad: IC1000 (Rodel)
Polishing pressure: 210 g / cm ²
Relative speed between substrate and polishing surface plate: 36 m / min

《Abrasive product evaluation items》
CMP rate: The film thickness difference between before and after the CMP of the copper film was calculated from the electrical resistance value, and divided by the processing time. The processing time was 1 minute.

  Etching rate: A substrate similar to the substrate to be polished is prepared separately, and immersed in a polishing liquid while stirring (stirring speed: 100 rpm) at room temperature (25 ° C.). And calculated by dividing by the immersion time. The immersion time was 10 minutes.

  In addition, in order to evaluate actual CMP characteristics, a silicon substrate in which a groove having a depth of 0.5 μm is formed in an insulating layer, a copper film is formed by a known sputtering method, and buried by a known heat treatment is also used as a substrate. Then, CMP was performed. The presence or absence of erosion and polishing scratches was confirmed by visual inspection of the substrate after CMP, observation with an optical microscope, and observation with an electron microscope. As a result, neither erosion nor polishing scratches were observed. Table 1 shows the evaluation results of the CMP rate and the etching rate in Examples 1 to 12 and Comparative Examples 1 to 5.

Example 13
After adding 70 parts by weight of water to 0.15 parts by weight of DL-malic acid (special grade reagent), and adding a solution of 0.1 part by weight of BTA in 0.8 parts by weight of methanol, Further, 0.025 part by weight of ammonium polyacrylate was added as a 40% aqueous solution, and finally 33.2 parts by weight of hydrogen peroxide (special grade, 30% aqueous solution) was added to obtain a metal polishing liquid. In this example, DL-malic acid, which is a highly water-soluble organic acid, was used as the metal oxide solubilizer, and a water-soluble ammonium polyacrylate was used as the second protective film forming agent.

  Using this metal polishing liquid, a CMP experiment was conducted under the same conditions as in Example 1. As a result, the CMP rate was 287 nm / min and the etching rate was 3.6 nm / min. However, as for the substrate on which the groove pattern is formed, as a result of CMP polishing by 50% more than the CMP time required for removing the predetermined thickness by CMP and observation with an electron microscope, a groove portion (embedded wiring) having a width of 10 μm is obtained. The dishing at the portion) was about 200 nm. In order to suppress dishing to 100 nm or less, it was necessary to limit the excess CMP time to 20%. Erosion and polishing scratches did not occur.

Example 14
After adding 70 parts by weight of water to 0.15 parts by weight of DL-malic acid (special grade reagent), and then adding a solution of 0.2 parts by weight of BTA in 0.8 parts by weight of methanol, Further, 0.125 parts by weight of polyacrylic acid ammonium salt was added as a 40% aqueous solution, and finally 33.2 parts by weight of hydrogen peroxide (special grade, 30% aqueous solution) was added to obtain a metal polishing liquid. In this embodiment, DL-malic acid, which is a highly water-soluble organic acid, is used as the metal oxide solubilizer, and a water-soluble ammonium polyacrylate is used as the second protective film forming agent.

  Using this metal polishing liquid, a CMP experiment was conducted under the same conditions as in Example 1. As a result, the CMP rate was as high as 185 nm / min, and the etching rate was as low as 0.2 nm / min. Also, the substrate on which the groove pattern was actually formed was subjected to CMP in the same manner as in the above CMP conditions and observed as described above. As a result, even if excessive CMP was performed for a time corresponding to 50%, dishing was 50 nm or less. Thus, neither erosion nor polishing scratches occurred.

Example 15
A metal polishing slurry was prepared in the same manner as in Example 14 except that DL-tartaric acid was used instead of DL-malic acid, and a CMP experiment was conducted in the same manner as in Example 1. As a result, the polishing rate was as high as 194 nm / min, and the etching rate was 0.8 nm / min. Further, after CMP of the substrate on which the groove pattern similar to that of Example 13 was formed, the substrate was observed, and the dishing when excessive CMP polishing was performed for a time corresponding to 50% was about 70 nm. No polishing scratches were generated.

Example 16
A metal polishing slurry was prepared in the same manner as in Example 13 except that citric acid was used instead of DL-malic acid, and a CMP experiment was conducted in the same manner as in Example 1. As a result, the CMP rate was as high as 213 nm / min, but the etching rate was slightly inferior to 4.6 nm / min. Further, as a result of observation after excessive CMP for a time corresponding to 30% on the substrate on which the same groove pattern as in Example 13 was formed, dishing was about 150 nm or less, and no erosion and polishing scratches were generated.

Comparative Example 6
A metal polishing slurry was prepared in the same manner as in Example 13 except that ammonium polyacrylate was not added, and a CMP experiment was conducted in the same manner as in Example 1. As a result, the CMP rate was slightly inferior to 140 nm / min, but the etching rate was inferior to 10.3 nm / min. Further, the substrate on which the groove pattern similar to that of Example 13 was formed was excessively polished by CMP for 30%, and then the surface of the substrate was observed. As a result, dishing increased to about 300 nm. No erosion or abrasive scratches were observed.

Comparative Example 7
A metal polishing slurry was prepared in the same manner as in Example 13 except that ammonium polyacrylate was not used and the amount of benzotriazole added was increased from 0.1 parts by weight to 0.2 parts by weight. Using this, a CMP experiment was conducted in the same manner as in Example 1.

  As a result, the etching rate was good at 2.4 nm / min, but the CMP rate was inferior at 93 nm / min. Further, as a result of observing the surface of the substrate after CMP polishing for an amount equivalent to 30% with respect to the substrate on which the groove pattern similar to that of Example 13 was formed, dishing was sufficiently satisfactory at about 150 nm. It wasn't possible. This is probably because the etching rate was low, but the CMP rate was low, and the CMP took a long time. Erosion and scratches did not occur.

  According to these examples and comparative examples, the effect of suppressing only the first protective film forming agent to a predetermined concentration and suppressing the etching rate to 10 nm / min or less is obtained by using the second protective film forming agent together. Even if the concentration of one protective film forming agent was lower, the effect of maintaining a higher CMP rate was achieved. Thus, it has been found that it is possible to suppress the occurrence of dishing, erosion, and polishing scratches and to form a highly reliable embedded pattern at a high CMP rate.

  As described above, according to the present invention, it is possible to sufficiently reduce the etching rate, maintain a high CMP rate, and form a highly reliable embedded pattern.

Claims (6)

Metal oxidizer,
A metal oxide solubilizer which is at least one selected from organic acids, ammonium salts of organic acids, inorganic acids and ammonia complexes,
At least one first protective film forming agent selected from azoles,
Alcohol , phenol , ester , polysaccharide (excluding cellulose), amino acid salt, polycarboxylic acid, polycarboxylic acid salt (however, polyacrylic acid, polyacrylic acid ammonium salt, polymethacrylic acid and polymethacrylic acid ammonium salt Except), at least one second protective film forming agent selected from vinyl polymers, sulfonic acids, sulfonates, aromatic amines, amides, azo compounds and molybdenum compounds, and
water,
A polishing liquid for metals comprising Metal oxidizer,
A metal oxide solubilizer which is at least one selected from organic acids, ammonium salts of organic acids, inorganic acids and ammonia complexes,
At least one first protective film forming agent selected from benzotriazole and derivatives thereof;
Alcohol , phenol , ester , polysaccharide (excluding cellulose), amino acid salt, polycarboxylic acid, polycarboxylic acid salt (however, polyacrylic acid, polyacrylic acid ammonium salt, polymethacrylic acid and polymethacrylic acid ammonium salt Except), at least one second protective film forming agent selected from vinyl polymers, sulfonic acids, sulfonates, aromatic amines, amides, azo compounds and molybdenum compounds, and
water,
A polishing liquid for metals comprising   The azole is 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-hexyl Nzotriazole, N- (1,2,3-benzotriazolyl-1-methyl) -N- (1,2,4-triazolyl-1-methyl) -2-ethylhexylamine, tolyltriazole, naphthotriazole and The metal polishing slurry according to claim 1, which is at least one selected from bis [(1-benzotriazolyl) methyl] phosphonic acid. The metal polishing slurry according to any one of claims 1 to 3, wherein the metal oxide solubilizer is at least one organic acid selected from formic acid, malonic acid, malic acid, tartaric acid, and citric acid. The metal-polishing liquid according to any one of claims 1 to 4 , which is used for polishing a metal containing at least one of copper, a copper alloy, a copper oxide, and a copper alloy oxide. A polishing method comprising polishing a metal on a surface of an object to be polished with the metal polishing liquid according to any one of claims 1 to 5 .