JP2009147267A - Polishing compound for chemical mechanical polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing compound for chemical mechanical polishing (CMP), with which a high-reliability metal film embedding pattern can be formed efficiently, by obtaining a high CMP speed, while maintaining a low etching speed. <P>SOLUTION: The polishing compound for CMP contains a polymer obtained by graft-polymerizing NVP to PVA. The polishing compound for CMP preferably contain a polymer, for which the degree of polymerization is 100 to 4,000 and the K factor is 12 to 150 in grafting NVP to PVA of which the degree of saponification is 70 to 100 mol%, and the polymer is obtained by blending NVP in a PVA solution and polymerizing it, while using hydrogen peroxide, organic peroxide, or azo compound as an initiator. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a chemical mechanical polishing abrasive suitable for polishing a wiring forming process of a semiconductor device or the like.

  In recent years, along with higher integration and higher performance of semiconductor integrated circuits (LSIs), new microfabrication techniques have been developed, and chemical mechanical polishing (hereinafter sometimes referred to as CMP) is one of them. is there. CMP is frequently used in planarization of an interlayer insulating film, formation of a metal plug, and formation of a buried wiring in an LSI manufacturing process, particularly in a multilayer wiring forming process. This technique is disclosed, for example, in US Pat. No. 4,944,836.

  The polishing agent used in the CMP is composed of an oxidizing agent and solid abrasive grains such as silica and alumina, and an aqueous dispersion containing a metal oxide dissolving agent, a protective film forming agent, and a water-soluble polymer as necessary. It is used a lot.

  However, the conventional CMP polishing agent has a drawback that it lowers not only the etching rate but also the CMP rate. Therefore, a CMP polishing agent that can sufficiently reduce the etching rate but does not decrease the CMP rate is desired. It is rare.

Therefore, as a polishing agent for CMP that efficiently forms an embedded pattern of a highly reliable metal film by sufficiently reducing the etching rate while maintaining a high CMP rate, an oxidizing agent, a metal oxide dissolving agent, a protective film Various polishing agents for CMP containing a forming agent, a water-soluble polymer, and the like have been proposed (for example, Patent Documents 1 to 3).
JP 2007-180568 A JP 2006-191132 A JP 2003-347245 A

  However, the CMP polishing agents described in Patent Documents 1 to 3 can maintain a low etching rate, but have not yet achieved a sufficiently high CMP rate, and further improvements are required.

  Therefore, the present invention provides a chemical mechanical polishing abrasive capable of efficiently forming a highly reliable embedded pattern of a metal film by obtaining a high CMP rate while maintaining a low etching rate. Objective.

  The present inventor finds that the polymer obtained by grafting vinyl pyrrolidone to polyvinyl alcohol is extremely useful in producing the intended abrasive for chemical mechanical polishing in order to solve the above problems, and completes the present invention. It came to.

  That is, the present invention is an abrasive for chemical mechanical polishing characterized by containing a polymer obtained by graft polymerization of vinyl pyrrolidone to polyvinyl alcohol.

  The abrasive for chemical mechanical polishing contains a polymer having a K value of 12 to 150 obtained by grafting vinylpyrrolidone to polyvinyl alcohol having a polymerization degree of 100 to 4000 and a saponification degree of 70 to 100 mol%. Is preferred.

  The above polymer is obtained by polymerizing a polymer obtained by grafting vinyl pyrrolidone on the polyvinyl alcohol, blending vinyl pyrrolidone in a polyvinyl alcohol solution, and using hydrogen peroxide, an organic peroxide or an azo compound as an initiator. Can do.

  The chemical mechanical polishing abrasive may contain abrasive grains, and the abrasive grains are preferably at least one selected from silica, alumina, titania, zirconia and germania. More preferably, the abrasive grains are colloidal silica or colloidal alumina.

  According to the polishing slurry for CMP of the present invention, a highly reliable embedded pattern of a metal film can be efficiently formed by obtaining a sufficiently high CMP rate while maintaining a low etching rate.

  The polymer contained in the polishing slurry for CMP of the present invention is obtained by adding vinylpyrrolidone (N-vinyl-2-pyrrolidone) (hereinafter sometimes referred to as NVP) to polyvinyl alcohol (hereinafter sometimes referred to as PVA). Graft polymerized.

  PVA used as a raw material for the graft polymer used in the present invention preferably has a degree of polymerization of 100 to 4000, and more preferably 100 to 3000. If the degree of polymerization is less than 100, a sufficient CMP rate cannot be obtained, and if it exceeds 4000, it is difficult to efficiently produce a graft polymer.

  The degree of saponification of PVA is preferably 70 to 100 mol%. When the saponification degree is less than 70 mol%, a sufficient CMP rate tends not to be obtained.

  It is preferable that K value of the obtained graft polymer is 12-150. The K value is a constant that represents the degree of polymerization proposed by the German chemist Fikencher. If the K value of the graft polymer is less than 12, a sufficient CMP rate cannot be obtained. The working efficiency is also lowered.

  The amount of NVP in the graft polymer is preferably 5 to 900% by weight based on PVA, and within this range, a high CMP rate and a low etching rate can be obtained.

  The graft polymer can be obtained by a production method in which NVP is blended in a PVA solution, and NVP is graft-polymerized to a PVA chain using an appropriate polymerization initiator. As the initiator, hydrogen peroxide, an organic peroxide, an azo-based initiator or the like that is usually used for radical polymerization can be used. What is necessary is just to select the reaction method and reaction conditions according to the example of general radical polymerization.

  As the polymerization initiator, hydrogen peroxide, an organic peroxide, an azo initiator, or the like that is usually used for radical polymerization can be used. Examples of the organic peroxide include tert-butyl hydroperoxide, di-tert-butyl peroxide, benzoyl peroxide and the like. As the azo compound, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2, And 2'-azobis (4-methoxy-2,4-dimethylvaleronitrile). What is necessary is just to select the reaction method and reaction conditions according to the example of general radical polymerization.

  The abrasive for CMP according to the present invention can contain abrasive grains.

  Examples of the abrasive grains include silica, alumina, titania, zirconia, and germania. At least one selected from these can be used, and colloidal silica or colloidal alumina is more preferable.

  The grain size of the abrasive grains is not particularly limited, but those having an average grain size of 50 nm or less are preferable, and the average grain size is particularly preferably 30 nm or less. Further, the content of the abrasive grains is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and 0.2 to 3% by weight with respect to 100 parts by weight of the polishing slurry for CMP. It is particularly preferred.

  Further, the polishing slurry for CMP according to the present invention may contain an oxidizing agent for the object to be polished, a protective film forming agent for the metal surface, and a metal oxide dissolving agent.

  Examples of the oxidizing agent include hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, ozone water, and the like, and at least one selected from these is preferable.

  The blending amount of the oxidant component is preferably 0.003 mol to 0.7 mol, more preferably 0.03 mol to 0.5 mol, and more preferably 0.2 mol to 0.00 mol with respect to 100 g of the polishing slurry for CMP. 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.

  As the protective film forming agent, nitrogen-containing compounds (for example, ammonia, alkylamines, amino acids, imines, azoles and salts thereof), mercaptans, glucose, and cellulose are preferable.

  Specific examples of the protective film forming agent include: ammonia; alkylamines such as dimethylamine, trimethylamine, triethylamine, propylenediamine, ethylenediaminetetraacetic acid (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-pro Phosphorus, L-cysteine, L-methionine, L-ethionine, L-lanthionine, L-cystathionine, L-cysteine, 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- Amino acids such as L-histidine, 3-methyl-L-histidine, ergothioneine, L-tryptophan, actinomycin C1, apamin, angiotensin I, angiotensin II and antipine; dithizone, cuproin (2,2′-biquinoline), neocuproine ( 2,9-dimethyl-1 Imines such as 10-phenanthroline), bathocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and cuperazone (biscyclohexanone oxalylhydrazone); benzimidazole-2-thiol, triazinedithiol , Triazine trithiol, 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-carboxyl-1H-benzotriazole methyl ester, 4-carboxyl-1H-benzotriazole butyl ester, 4-carboxyl-1H-benzotriazole octyl ester, 5-hexylbenzotriazole, [1, 2,3-benzotriazolyl-1-methyl] [1,2,4-triazolyl-1-methyl] [2-ethylhexyl] amine, tolyltriazole, naphthotriazole, bis [(1-benzotriazolyl) methyl Azoles such as phosphonic acid; mercaptans such as nonyl mercaptan and dodecyl mercaptan; and saccharides such as glucose and cellulose. These may use a single compound or may use two or more compounds in combination.

  Among these, chitosan, ethylenediaminetetraacetic acid, L-tryptophan, cuperazone, triazinedithiol, benzotriazole, 4-hydroxybenzotriazole, 4-carboxyl-1H-benzotriazole butyl ester, tolyltriazole, and naphthotriazole are high CMP. This is preferable for achieving both a high speed and a low etching speed.

  The blending amount of the protective film forming agent is preferably 0.0001 mol to 0.05 mol, more preferably 0.0003 mol to 0.005 mol, and more preferably 0.0005 mol to 0.0035 mol with respect to 100 g of the polishing slurry for CMP. It is particularly preferable that 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.

  As the metal oxide solubilizer, at least one of an organic acid, an organic acid ester, an ammonium salt of an organic acid, and sulfuric acid is preferable.

  The metal oxide solubilizer is preferably water-soluble and may be blended in the form of an aqueous solution. Specific examples 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, maleic acid, phthalate Organic acids such as acids, malic acid, tartaric acid and citric acid, esters of these organic acids, salts of these organic acids (ammonium salts, etc.), sulfuric acid, nitric acid, ammonia, ammonium salts (eg ammonium persulfate, ammonium nitrate, ammonium chloride) Etc.) and chromic acid. These may use a single compound or may use two or more compounds in combination.

  Of these, formic acid, malonic acid, malic acid, tartaric acid, and citric acid are preferred because they are easily balanced with the protective film forming agent. 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.

  In the present invention, the compounding amount of the metal oxide solubilizer is preferably 0 to 0.005 mol, more preferably 0.00005 mol to 0.0025 mol, more preferably 0.0005 mol to 0, with respect to 100 g of the polishing slurry for CMP. Particularly preferred is .0015 mol. If this amount exceeds 0.005 mol, it tends to be difficult to suppress etching.

  The CMP polishing slurry of the present invention may further contain other water-soluble polymer in the PVA graft polymer. Examples of the water-soluble polymer include polyacrylic acid or a salt thereof, polymethacrylic acid or a salt thereof, polyamic acid and a salt thereof, polyacrylamide, polyvinyl alcohol, and polyvinylpyrrolidone, and two or more of these may be used.

  The polishing method using the CMP polishing agent is not particularly limited. For example, the polishing platen is pressed in a state where the substrate having the film to be polished is pressed against the polishing cloth while supplying the CMP polishing agent onto the polishing cloth of the polishing platen. The film to be polished can be polished by relatively moving the substrate.

The polishing conditions are not limited, but the rotation speed of the 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 cloth of the semiconductor substrate having the film to be polished is preferably 100 to 1000 gf / cm ^{2. In} order to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern, the pressure is 100 to 500 gf. / Cm ² is more preferable. As an abrasive cloth, a general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. can be used.

  Hereinafter, the present invention will be specifically described by way of examples, but the scope of the present invention is not limited thereto.

  Graft polymers 1 to 4 according to Examples 1 to 4 of the present invention were prepared by the following method. Polishing for CMP of Examples 1 to 4 and Comparative Examples 1 to 3 (Comparative Example 3 does not contain a polymer) using the obtained Polymers 1 to 4 and Polymers 5 and 6 according to Comparative Examples 1 and 2 Agents were prepared and evaluated for CMP rate and edging rate. The results are shown in Table 1.

[Preparation of polymer]
Polymer 1: Dissolve 190 g of PVA (polymerization degree 200, saponification degree 98-99 mol%) in 800 g of pure water, then add and mix NVP 10 g (vs. PVA 5.26 wt%), and deoxygenate by nitrogen purge It was. Subsequently, the temperature of the reaction system was adjusted to 70 ° C. To this, 10 mg of 1 wt% copper sulfate, 1.0 g of 28 wt% aqueous ammonia and 1.5 g of 30 wt% aqueous hydrogen peroxide were added to initiate polymerization. During polymerization, the temperature is maintained at 70 to 80 ° C. and pH 5.5 to 6.5 with ammonia, and 1.5 g of 30% by weight hydrogen peroxide solution is added 6 times every 15 minutes so that the polymerization rate is 90% or more. It became. Subsequently, 4 g of 30 wt% aqueous hydrogen peroxide was added as a residual NVP treatment step and reacted for a total of 210 minutes while maintaining the pH at 5 or higher with aqueous ammonia to obtain a 20% aqueous solution of a polymer having a K value of 23.

  Polymer 2: Polymer having a K value of 31 in the same manner as the preparation of Polymer 1 except that NVP (42.9 wt% of PVA) was used for PVA (polymerization degree 2400, saponification degree 98-99 mol%). A 20% aqueous solution of 2 was obtained.

Polymer 3: A P value (polymerization degree 500, saponification degree 72.5-74.5 mol%) was used in the same manner as the preparation method for polymer 1 except that NVP (vs. PVA 150 wt%) was used. A 20% aqueous solution of polymer 3 was obtained.

  Polymer 4: A polymer 4 having a K value of 94 was prepared in the same manner as in the preparation of Polymer 1 except that NVP (based on PVA 900 wt%) was used for PVA (polymerization degree 3500, saponification degree 87-89 mol%). A 20% aqueous solution was obtained.

  Polymer 5: PVA (polymerization degree 3500, saponification degree 87-89 mol%) powder.

  Polymer 6: Polyvinylpyrrolidone (K-30, K value 30) powder.

[Preparation of abrasive for CMP]
To 98 parts by weight of water, 0.4 parts by weight of malic acid, 1 part by weight of abrasive grains, 0.05 parts by weight (solid content) of the above polymers 1 to 6, and 0.2 parts by weight of benzotriazole. In addition, a solution obtained by adding 0.5 parts by weight of aqueous hydrogen peroxide (special grade reagent, 30% aqueous solution) as an oxidizing agent for the conductor was used as an abrasive for CMP. As the abrasive grains, colloidal silica having an average particle diameter of 20 nm prepared by hydrolysis of tetraethoxysilane in an ammonia solution was added.

[Polishing method]
Using the obtained abrasive, CMP was performed under the following conditions.
Substrate to be polished: silicon substrate on which a 1 μm thick copper film is formed Polishing pad: foamed polyurethane resin with closed cells Polishing pressure: 250 gf / cm ²
Relative speed between substrate and polishing surface plate: 18m / min

[Abrasive Product Evaluation Method]
CMP rate: The difference in film thickness of the copper film before and after CMP was calculated from the electrical resistance value.
Etching rate: The difference in thickness of the copper layer before and after immersion in the stirred abrasive was calculated from the electrical resistance value.

  According to the polishing slurry for CMP of the present invention, it is possible to efficiently form a highly reliable embedded pattern of a metal film by obtaining a high CMP rate while maintaining a low etching rate.

Claims (6)

  An abrasive for chemical mechanical polishing, comprising a polymer obtained by graft-polymerizing vinyl pyrrolidone to polyvinyl alcohol.   2. The polymer according to claim 1, comprising a polymer having a K value of 12 to 150 obtained by grafting vinylpyrrolidone to polyvinyl alcohol having a polymerization degree of 100 to 4000 and a saponification degree of 70 to 100 mol%. Abrasives for chemical mechanical polishing.   The polymer obtained by grafting vinyl pyrrolidone to the polyvinyl alcohol is obtained by blending vinyl pyrrolidone in a polyvinyl alcohol solution and polymerizing using hydrogen peroxide, an organic peroxide or an azo compound as an initiator. The abrasive for chemical mechanical polishing according to claim 1 or 2.   The abrasive for chemical mechanical polishing according to claim 1, further comprising abrasive grains.   The abrasive for chemical mechanical polishing according to claim 4, wherein the abrasive is at least one selected from silica, alumina, titania, zirconia, and germania.   The abrasive for chemical mechanical polishing according to claim 4, wherein the abrasive grains are colloidal silica or colloidal alumina.