JP2004311967A - Polymer and composition for cmp abrasive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an N-vinyl amide based polymer for a CMP abrasive which is superior in can-stability and hardly occurs abrasion scratches. <P>SOLUTION: In the polymer, the content of a nitrogen containing compound which is a hydrolysate of very small amounts of N-vinyl amide based monomer and/or N-vinyl amide based polymer is suppressed to a value equal to or less than 10,000ppm with respect to the N-vinyl amide based polymer, and the content of a nitrogen containing compound which is hydrolysis material of N-vinyl amide based monomer is suppressed to a value equal to or less than 5% with respect to the N-vinyl amide based polymer. Thus, when the polymer is used as a CMP abrasive, the dispersion stability of abrasive grains is improved and abrasion scratches are reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polymer suitable for a CMP abrasive, and relates to an N-vinylamide-based polymer having a residual monomer content of 10,000 ppm or less based on the polymer. Further, the present invention relates to an N-vinylamide-based polymer in which a nitrogen-containing compound, which is a hydrolyzate of a monomer, is 50,000 ppm or less based on the polymer.

  2. Description of the Related Art In recent years, various microfabrication techniques have been developed in accordance with higher integration and higher performance of semiconductor integrated circuits. CMP (Chemical Mechanical Polishing) is also one of such fine processing techniques, and is used in the manufacturing process of a semiconductor integrated circuit, particularly in the flattening of an interlayer insulating film, the formation of metal plugs, and the formation of embedded wiring in a multilayer wiring forming process. In the CMP technique, it is important what kind of CMP polishing agent is used for improving a polishing rate and achieving a higher level of planarization.

It is known to add water-soluble polymers to CMP abrasives for various purposes,
It is also known to use N-vinylamide polymers such as polyvinylpyrrolidone as the water-soluble polymer. (For example, Patent Documents 1 and 2)
It is known that by adding an N-vinylamide-based polymer such as polyvinylpyrrolidone as an insulating film protective agent to a CMP polishing agent, the selectivity between a metal and an interlayer insulating film is enhanced, and polishing with more excellent flatness can be performed. On the other hand, CMP abrasives using an N-vinylamide-based polymer have insufficient stability of the abrasive grains, and have problems such as the occurrence of sediments and the occurrence of polishing scratches when stored for a long time. In order to solve such a problem, a method of separately supplying an abrasive slurry and an N-vinylamide-based polymer aqueous solution to a polishing platen has been disclosed, but it has not been sufficiently satisfactory. (Patent Document 2)
JP-A-2000-129243 (page 1) JP-A-2002-134444 (page 1)

  The present invention has been made in view of the above-mentioned problems of the related art, and an object of the present invention is to provide an N-vinylpyrrolidone-based polymer suitable for a CMP abrasive. More specifically, it is an object of the present invention to provide an N-vinylamide-based polymer for a CMP polishing slurry which provides a CMP polishing slurry which has excellent storage stability and hardly generates polishing scratches.

  The present inventors have conducted intensive studies to solve the above conventional problems, and as a result, found that a trace amount of N-vinylamide-based monomer contained in N-vinylamide-based polymer and / or nitrogen-containing compound which is a hydrolyzate of N-vinylamide-based monomer Influences the dispersion stability of the abrasive grains and, consequently, the occurrence of polishing flaws.

  That is, the present invention relates to a polymer for a CMP polishing slurry, wherein the content of the N-vinylamide-based monomer is 10,000 ppm or less based on the N-vinylamide-based polymer. Further, the present invention relates to a polymer for a CMP abrasive, wherein the content of a nitrogen-containing compound which is a hydrolyzate of an N-vinylamide monomer is 50,000 ppm or less based on the N-vinylamide polymer.

  The use of the polymer for a CMP abrasive of the present invention can provide a CMP abrasive having excellent storage stability and less polishing scratches.

  The N-vinylamide-based polymer used in the present invention is a homopolymer or a copolymer obtained by polymerizing an N-vinylamide-based monomer. The N-vinylamide-based monomer is typically represented by the following general formula ( It is a monomer represented by 1).

(In the formula, R1 represents hydrogen or a methyl group. R2 and R3 are the same or different and each is a hydrogen, methyl group, or ethyl group, or a ring having 3 to 5 carbon atoms by combining R2 and R3. Are formed.).

  Specifically, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylformamide, N-methyl-N-vinylformamide, N-vinylpropionamide, and N-vinyl which is a cyclic N-vinylamide Examples thereof include N-vinyllactams such as vinylpyrrolidone, N-vinylpiperidone, and N-vinylcaprolactam, and one kind or two or more kinds can be used as needed. Preferably, it is N-vinylpyrrolidone.

  The N-vinylamide polymer may be a homopolymer or may optionally contain a copolymer component. Examples of such copolymer components include (1) methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) (Meth) acrylic esters such as glycidyl acrylate; (2) (meth) acrylic esters such as (meth) acrylamide, N-monomethyl (meth) acrylamide, N-monoethyl (meth) acrylamide and N, N-dimethyl (meth) acrylamide ) Acrylamide derivatives; (3) basic unsaturated monomers such as dimethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylamide, vinylpyridine, vinylimidazole and salts or quaternized products thereof; ) Vinylformamide, vinylacetamide, vinyloxazoline, Vinylamides such as propenyl oxazoline; (5) unsaturated monomers containing a carboxyl group such as (meth) acrylic acid, itaconic acid, maleic acid and fumaric acid and salts thereof; (6) maleic anhydride and itaconic anhydride; (7) vinyl esters such as vinyl acetate and vinyl propionate; (8) vinyl ethylene carbonate and derivatives thereof; (9) ethyl (meth) acrylate-2-ethyl sulfonate and derivatives thereof; 10) Vinyl sulfonic acid and derivatives thereof; (11) Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; and (12) Olefins such as ethylene, propylene, octene and butadiene.

  These may be used alone or in combination of two or more. The copolymerization amount of the N-vinylamide component in the N-vinylamide-based polymer chain is preferably 50% by mass, more preferably 80% by mass or more. If the content of the N-vinylamide component is less than 50% by mass, sufficient dispersibility of the filler and antistatic performance may not be obtained. The form of the copolymer is not particularly limited, and may be a random copolymer, and may be a graft copolymer or a block copolymer.

  The method of polymerizing the N-vinylamide polymer is not particularly limited, but is generally obtained by radical polymerization in an aqueous solution or an organic solvent using a radical generator such as an organic peroxide, an azo compound, or hydrogen peroxide. Can be

  It is important that the N-vinylamide-based polymer of the present invention has a N-vinylamide-based monomer content of 10,000 ppm or less based on the N-vinylamide-based polymer. The amount of the N-vinylamide-based monomer is preferably 1000 ppm or less, more preferably 100 ppm or less, and most preferably 10 ppm or less based on the N-vinylamide-based polymer. If the amount of the N-vinylamide-based monomer is larger than 10000 ppm, when added to a CMP abrasive, the dispersion stability of the abrasive grains is reduced and polishing scratches are likely to occur.

  Further, it is important that the N-vinylamide-based polymer of the present invention has a nitrogen-containing compound which is a hydrolyzate of the N-vinylamide-based monomer contained at 50,000 ppm or less based on the N-vinylamide-based polymer. The amount of the nitrogen-containing compound which is a hydrolyzate of the N-vinylamide monomer is preferably 30,000 ppm or less, more preferably 20,000 ppm or less, based on the N-vinylamide polymer. You. When the amount of the nitrogen-containing compound, which is a hydrolyzate of the N-vinylamide-based monomer, is more than 50,000 ppm, when added to a CMP abrasive, the dispersion stability of the abrasive grains is reduced, and polishing scratches are likely to occur. .

  Further, the N-vinylamide-based monomer is not more than 10,000 ppm based on the N-vinylamide-based polymer, and the nitrogen-containing compound which is a hydrolyzate of the N-vinylamide-based polymer is not more than 50,000 ppm based on the N-vinylamide-based polymer. Is particularly preferred.

  Specifically, the nitrogen-containing compound which is a hydrolyzate of the N-vinylamide-based monomer is 2-pyrrolidone when the N-vinylamide-based monomer is N-vinylpyrrolidone, and acetamido when the N-vinylamide-based monomer is N-vinylacetamide. -Methyl-N-vinylacetamide is N-methylacetamide; N-vinylformamide is formamide; and N-methyl-N-vinylformamide is N-methyl-formamide.

  The present invention is not limited by the method for reducing the residual monomer or the method for reducing the monomer hydrolyzate, but in order to reduce the residual monomer, it is necessary to take a sufficient reaction time or to reduce the reaction rate to 90% during the polymerization. After that, it can be achieved by further adding a radical generator such as an organic peroxide, an azo compound or hydrogen peroxide to the reaction system. Further, in order to reduce the amount of hydrolyzate of the monomer, the polymerization can be achieved by adjusting the pH of the system to 8 or more during the polymerization, or by performing the polymerization in an organic solvent.

The molecular weight of the N-vinylamide-based polymer of the present invention is preferably 1,000 to 2,000,000 as a weight average molecular weight. More preferably, the lower limit is 5000 or more,
It is particularly preferred that it is 10,000 or more. The upper limit is more preferably 1500000 or less, and particularly preferably 1,000,000 or less. If the weight average molecular weight is less than 1,000, the suppression of etching tends to be insufficient, and if it exceeds 2,000,000, the polishing rate tends to decrease.

  The CMP abrasive is generally a composition containing an oxidizing agent, fine particles, a water-soluble polymer, an insulating film dissolving agent and the like. The composition for a CMP polishing slurry of the present invention is not particularly limited with respect to other components as long as it contains the N-vinylamide-based polymer of the present invention. Components such as an oxidizing agent, fine particles, a water-soluble polymer, and an insulating film dissolving agent are included. May be included.

  Examples of the oxidizing agent include hydrogen peroxide, peracetic acid, perbenzoic acid, organic peroxides such as tert-butyl hydroperoxide, permanganate compounds such as potassium permanganate, and dichromate compounds such as potassium dichromate. , Halogen acid compounds such as potassium iodate, nitric acid compounds such as nitric acid and iron nitrate, perhalic acid compounds such as perchloric acid, transition metal salts such as potassium ferricyanide, persulfates such as ammonium persulfate, and heteropolyacids Is fisted. Among these oxidizing agents, hydrogen peroxide and organic peroxides which do not contain a metal element and whose decomposition products are harmless are particularly preferred. By including these oxidizing agents, the polishing rate can be further increased.

  As the fine particles, polymer fine particles, inorganic fine particles and the like can be used. Examples of the polymer particles include (1) polystyrene and styrene-based copolymers, (2) (meth) acrylic resins and acrylic-based copolymers such as polymethyl methacrylate, (3) polyvinyl chloride, polyacetal, and unsaturated polyester. , A polyamide, a polyimide, a polycarbonate, a phenoxy resin, and (4) a thermoplastic resin such as a polyolefin such as polyethylene, polypropylene, poly-1-butene and poly-4-methyl-1-pentene and an olefin-based copolymer. Coalescing particles can be used. Further, as the polymer particles, those composed of a polymer having a crosslinked structure, obtained by copolymerizing styrene, methyl methacrylate, etc., with divinylbenzene, ethylene glycol dimethacrylate, etc., can also be used. The hardness of the polymer particles can be adjusted by the degree of the crosslinking. In addition, polymer particles composed of a thermosetting resin such as a phenol resin, a urethane resin, a urea resin, a melamine resin, an epoxy resin, an alkyd resin, and an unsaturated polyester resin can also be used.

  As the polymer particles, those composed of a modified polymer obtained by polycondensing various polymers with alkoxysilane and metal alkoxide can also be used. As this alkoxysilane, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, or the like can be used. One type of these polymer particles may be used alone, or two or more types may be used in combination.

  Further, as the inorganic particles, inorganic particles made of oxides of silicon or a metal element such as alumina, titania, ceria, silica, zirconia, iron oxide and manganese oxide can be used. One kind of these inorganic particles may be used alone, or two or more kinds may be used in combination.

  As the water-soluble polymer, other polymers may be used in addition to the N-vinylamide-based polymer of the present invention. Examples of other water-soluble polymers include polyacrylic acid, ammonium polyacrylate, sodium polyacrylate, and polyacrylic acid. Potassium salt, polymethacrylic acid, ammonium polymethacrylate, sodium polymethacrylate, polyacrylamide, polyvinyl alcohol, and the like are included.

  Examples of the insulating film dissolving agent include strong alkalis such as potassium hydroxide, sodium hydroxide and ammonium hydroxide, strong acids such as sulfuric acid, nitric acid and hydrochloric acid, hydrofluoric acid, fluorinated acids such as F-butyric acid and trifluoroacetic acid, and formic acid. Organic acids such as acetic acid, propionic acid, butyric acid, valeric acid, benzoic acid, glycolic acid, salicylic acid, oxalic acid, lactic acid, succinic acid, glutaric acid, adipic acid, maleic acid, phthalic acid, malic acid, tartaric acid and citric acid No.

  It is not necessary for the CMP polishing slurry using the present invention to contain all of these oxidizing agents, fine particles, water-soluble polymers, and insulating film dissolving agents, and additives other than these may be added according to the purpose.

  The content of the N-vinylamide-based polymer of the present invention in the composition for a CMP abrasive is preferably 0.001% by mass to 10% by mass, more preferably 0.01% by mass to 1% by mass. preferable. If the amount is less than 0.001% by mass, the suppression of etching tends to be difficult, and if it exceeds 10% by mass, the polishing rate tends to decrease, which is not preferable.

  The composition for a CMP polishing slurry of the present invention may contain an oxidizing agent, and the content of the oxidizing agent is preferably at least 0.01 mol%, more preferably at least 0.05 mol%, based on the total amount. The upper limit is preferably at most 10 mol%, more preferably at most 5 mol%. If it is less than 0.01 mol%, the polishing rate tends to decrease, and if it exceeds 10 mol%, it tends to be difficult to suppress the etching.

  The composition for a CMP polishing slurry of the present invention may contain fine particles, and the content thereof is preferably at least 0.1% by mass, more preferably at least 0.5% by mass, based on the total amount. The upper limit is preferably 10% by mass or less, more preferably 5% by mass or less. If it is less than 0.1% by mass, the polishing rate tends to decrease, and if it exceeds 10% by mass, the effect of improving the polishing rate tends not to increase.

  The composition for CMP abrasives of the present invention may contain a water-soluble polymer other than the N-vinylamide-based polymer, and the content of the lower limit is preferably at least 0.001% by mass or more, and more preferably 0.01% by mass based on the total amount. The above is more preferred. The upper limit is preferably 1% by mass or less, more preferably 0.5% by mass. If it is less than 0.001% by mass, the effect of suppressing etching and stabilizing the dispersion of fine particles cannot be obtained. If it exceeds 1% by mass, the polishing rate tends to decrease.

  The composition for a CMP polishing slurry of the present invention may contain an insulating film dissolving agent, and the content thereof is preferably at least 0.001 mol%, more preferably at least 0.01 mol%, based on the total amount. preferable. The upper limit is preferably 0.5 mol% or less, more preferably 0.2 mol% or less. If it is less than 0.001 mol%, the polishing rate tends to decrease, and if it exceeds 0.5 mol%, suppression of etching tends to be difficult.

  Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

-Synthesis example 1-
A stirred pressure-resistant autoclave is charged with 110 parts of isopropanol, 350 parts of vinylpyrrolodone and 1 part of di-t-butyl peroxide in advance and heated to 120 ° C. to a pressure of about 2.5 × 10 ⁵ Pa. After that, a mixture of 40 parts of isopropanol and 1 part of di-t-butyl peroxide was dropped and mixed over 4 hours, and the mixture was heated for 4 hours after the completion of the dropping to complete the reaction. The mixture is cooled to 80 DEG C. by releasing pressure, and 100 parts of isopropanol are distilled off. The mixture was diluted with 200 parts of water, and all of isopropanol was distilled off by blowing steam to obtain an aqueous solution of polyvinylpyrrolidone. (Polymer 1)
The content of vinylpyrrolidone measured by the LC method was 8 ppm based on polyvinylpyrrolidone. Further, the content of 2-pyrrolidone measured by the LC method was 20 ppm based on polyvinylpyrrolidone.

-Synthesis example 2-
Acrylic acid neutralized with ammonia by heating 1800 parts of a solution prepared by adding water to the aqueous solution of polyvinylpyrrolidone obtained in Synthesis Example 1 to a polymer concentration of 30% to 85 ° C. in a stirring vessel under a weak nitrogen stream and neutralizing with ammonia 45 parts of an aqueous solution and 3 parts of a 20% aqueous solution of ammonium persulfate are added dropwise over 2 hours. 3 g of a 10% aqueous solution of 2,2′-azobis (2-methylpropionamidine) dihydrochloride was added, and the reaction was further reacted for 4 hours. Thus, an aqueous solution of a polyvinylpyrrolidone-polyacrylic acid graft copolymer (ammonium salt) was obtained. (Polymer 2)
The content of vinylpyrrolidone measured by the LC method was 4 ppm with respect to the copolymer, and the content of 2-pyrrolidone was 18 ppm.

-Synthesis example 3-
Air (oxygen concentration = 21%) was added to 400 parts of vinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd.) containing 10 ppm of N, N'-di-sec-butyl-p-phenylenediamine, which was obtained by a crystallization purification method. After blowing for 120 minutes, the mixture is dissolved in 1500 parts of water, charged in a stirred vessel, and heated to 70 ° C. under a weak nitrogen stream. 50 parts of 5% aqueous hydrogen peroxide and 50 parts of 5% aqueous ammonia were added dropwise over 1 hour, and the mixture was further reacted for 4 hours after completion of the addition to obtain a 20% by mass aqueous solution of polyvinylpyrrolidone. The aqueous pyrrolidone solution was stored in an atmosphere gas having an oxygen concentration of 10 Vol%. (Polymer 3)
The content of vinylpyrrolidone measured by the LC method was 10 ppm based on polyvinylpyrrolidone, and the content of 2-pyrrolidone was 1.5000 ppm based on polyvinylpyrrolidone.

-Synthesis example 4-
400 parts of vinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd.) obtained by crystallization purification method and containing 10 ppm of N, N'-di-sec-butyl-p-phenylenediamine is dissolved in 1500 parts of water and placed in a stirring vessel. And heated to 90 ° C. under a weak nitrogen stream. 50 parts of a 3% hydrogen peroxide solution and 50 parts of a 5% ammonia solution were added dropwise over 1 hour, and the mixture was further reacted for 1 hour from the completion of the addition to obtain a 20% aqueous solution of polyvinylpyrrolidone. A nitrogen gas containing 10 Vol% of oxygen was blown into the aqueous solution at 530 ml / min for 120 minutes, and then stored in an atmosphere gas having an oxygen concentration of 5 Vol%. (Polymer 4)
The content of vinylpyrrolidone measured by the LC method was 12000 ppm based on polyvinylpyrrolidone, and the content of 2-pyrrolidone was 52000 ppm based on polyvinylpyrrolidone.

(Example 1)
In ion-exchanged water, 3% by mass of colloidal alumina (manufactured by C-I Kasei Co., Ltd., trade name (Nanotech A12O3)) as an alumina component, 2% by mass of (Polymer 1) of Synthesis Example 1 as a resin component, and 1% by mass of hydrogen peroxide %, Salicylaldoxime 0.3% by mass, and ammonium lactate 1% by mass, and the pH was adjusted to 6 with a 25% aqueous ammonia solution to obtain an aqueous dispersion for CPM.

  Using this aqueous dispersion for CMP, a copper film (thickness: 15000Å) on a silicon wafer with an 8-inch thermal oxide film was set on a CMP apparatus (Lapmaster SFT, model “LPG510”), Polishing was performed for 1 minute using a polyurethane polishing pad (Rodel Nitta, product number “IC1000”) at a weight of 300 g / cm 2. The thickness of the copper film after polishing was measured by an electric conduction type film thickness measuring instrument, and the polishing rate was calculated. As a result, it was 5500 ° / min. Further, the silica film formed on the silicon substrate was polished, washed and dried under the same conditions, and polishing scratches were confirmed by KLA (manufactured by KLA Tencor, model “Surfscan SP-1”). Further, the same test was carried out by storing the slurry stored in the sealed container at 50 ° C. for 10 days, and the results are shown in Table 1.

(Examples 2 and 3)
An experiment was performed in the same manner as in Example 1 except that Polymer 1 was changed to Polymer 2 and Polymer 3. The results were as summarized in Table 1.

(Example 4)
The experiment was carried out in the same manner as in Example 1 except that 2% by mass of Polymer 1 in Example 1 was changed to 1.5% by mass, and 0.5% by mass of ammonium polyacrylate having a weight average molecular weight of 5,500 was added. The results were as summarized in Table 1.

(Comparative Example 1)
An experiment was performed in the same manner as in Example 1 except that Polymer 1 was changed to Polymer 4. The results were as summarized in Table 1.

According to the present invention, it is possible to obtain a CMP polishing slurry which is excellent in storage stability and hardly generates polishing scratches.

Claims (3)

An N-vinylamide-based polymer, wherein the content of the N-vinylamide-based monomer is 10,000 ppm or less based on the N-vinylamide-based polymer. An N-vinylamide-based polymer, wherein the content of a nitrogen-containing compound which is a hydrolyzate of the N-vinylamide-based monomer is 50,000 ppm or less based on the N-vinylamide-based polymer. For polymers. A composition for a CMP abrasive, comprising the polymer according to claim 1.