RESIST UNDERLAYER FILM-FORMING COMPOSITION

Abstract

A composition for forming a resist underlayer film exhibits strong etching resistance, has a good dry etching rate ratio and a good optical constant, and is capable of forming a film that provides good coverage over a so-called multilevel substrate and that is flat with reduced difference in thickness after embedding. A resist underlayer film uses said composition for forming a resist underlayer film; and a method for producing a semiconductor device. The composition for forming a resist underlayer film contains: a polymer having the partial structure represented by formula (1); and a solvent. (In the formula, Ar represents an optionally substituted C6-20 aromatic group.)

Claims

1. A resist underlayer film-forming composition comprising a solvent and a polymer having a partial structure represented by the following formula (1): ##STR00020## wherein Ar denotes an optionally substituted C6-C20 aromatic group.

2. The resist underlayer film-forming composition according to claim 1, wherein Ar in formula (1) is a phenyl group, a naphthyl group, an anthracenyl group, a pyrenyl group or a combination of any of them.

3. The resist underlayer film-forming composition according to claim 1, wherein Ar in formula (1) is a naphthyl group, an anthracenyl group or a combination thereof.

4. The resist underlayer film-forming composition according to claim 1, further comprising a crosslinking agent.

5. The resist underlayer film-forming composition according to claim 1, further comprising an acid and/or an acid generator.

6. The resist underlayer film-forming composition according to claim 1, wherein the solvent has a boiling point of 160° C. or above.

7. A resist underlayer film, which is a baked product of a coating film comprising the resist underlayer film-forming composition according to claim 1.

8. A method for manufacturing a semiconductor device, comprising the steps of: forming on a semiconductor substrate a resist underlayer film using the resist underlayer film-forming composition according to claim 1; forming a resist film on the formed resist underlayer film; irradiating the formed resist film with light or electron beam followed by development, to form a resist pattern; etching the resist underlayer film through the formed resist pattern, to form a patterned resist underlayer film; and processing the semiconductor substrate through the patterned resist underlayer film.

Description

EXAMPLES

[0122] Specific examples of the resist underlayer film-forming compositions of the present invention will be described hereinbelow with reference to the following Examples. However, it should be construed that the scope of the present invention is not limited thereto.

[0123] The equipment such as apparatus used for the measurement of the weight average molecular weight of reaction products obtained in Synthesis Examples are described below.

[0124] Apparatus: HLC-8320 GPC manufactured by Tosoh Corporation

[0125] GPC columns: TSKgel Super-Multipore HZ-N (two columns)

[0126] Column temperature: 40° C.

[0127] Flow rate: 0.35 ml/min

[0128] Eluent: THF

[0129] Standard samples: Polystyrenes

[0130] The following are the chemical structures (illustrative) and the abbreviations of representative raw materials used.

##STR00014##

Synthesis Example 1

[0131] 6.00 g of NC-7300L (product name, manufactured by Nippon Kayaku Co., Ltd.), 4.91 g of 1-naphthalenecarboxylic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.26 g of ethyltriphenylphosphonium bromide as a catalyst were added to 26.07 g of propylene glycol monomethyl ether (hereinafter, abbreviated as PGME in this specification). The resultant mixture was allowed to react at 140° C. for 24 hours to give a solution containing the reaction product. Thereto were added 12.00 g of an anion exchange resin (product name: DOWEX [registered trademark] MONOSPHERE [registered trademark] 550A, Muromachi Technos Co., Ltd.) and 12.00 g of a cation exchange resin (product name: AMBERLYST [registered trademark] 15JWET, ORGANO CORPORATION). The resultant mixture was stirred at 25° C. to 30° C. for 4 hours and was then filtered.

[0132] GPC analysis showed that the thus obtained reaction product had a weight average molecular weight of 770 relative to standard polystyrenes. The reaction product obtained is estimated to be a copolymer having a structural unit represented by the following formula (1):

##STR00015##

Synthesis Example 2

[0133] 6.00 g of NC-7300L (product name, manufactured by Nippon Kayaku Co., Ltd.), 6.33 g of 9-anthracenecarboxylic acid (manufactured by Midori Kagaku Co., Ltd.) and 0.26 g of ethyltriphenylphosphonium bromide as a catalyst were added to 26.07 g of PGME. The resultant mixture was allowed to react at 140° C. for 24 hours to give a solution containing the reaction product. Thereto were added 13.00 g of an anion exchange resin (product name: DOWEX [registered trademark] MONOSPHERE [registered trademark] 550A, Muromachi Technos Co., Ltd.) and 13.00 g of a cation exchange resin (product name: AMBERLYST [registered trademark] 15JWET, ORGANO CORPORATION). The resultant mixture was stirred at 25° C. to 30° C. for 4 hours and was then filtered.

[0134] GPC analysis showed that the thus obtained reaction product had a weight average molecular weight of 830 relative to standard polystyrenes. The reaction product obtained is estimated to be a copolymer having a structural unit represented by the following formula (2):

##STR00016##

Synthesis Example 3

[0135] 6.00 g of NC-7300L (product name, manufactured by Nippon Kayaku Co., Ltd.), 3.48 g of benzoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.26 g of ethyltriphenylphosphonium bromide as a catalyst were added to 22.74 g of PGME. The resultant mixture was allowed to react at 140° C. for 24 hours to give a solution containing the reaction product. Thereto were added 10.00 g of an anion exchange resin (product name: DOWEX [registered trademark] MONOSPHERE [registered trademark] 550A, Muromachi Technos Co., Ltd.) and 10.00 g of a cation exchange resin (product name: AMBERLYST [registered trademark] 15JWET, ORGANO CORPORATION). The resultant mixture was stirred at 25° C. to 30° C. for 4 hours and was then filtered.

[0136] GPC analysis showed that the thus obtained reaction product had a weight average molecular weight of 750 relative to standard polystyrenes. The reaction product obtained is estimated to be a copolymer having a structural unit represented by the following formula (4):

##STR00017##

Synthesis Example 4

[0137] 5.00 g of NC-7300L (product name, manufactured by Nippon Kayaku Co., Ltd.), 5.85 g of 1-pyrenecarboxylic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.22 g of ethyltriphenylphosphonium bromide as a catalyst were added to 25.83 g of PGME. The resultant mixture was allowed to react at 140° C. for 24 hours to give a solution containing the reaction product. Thereto were added 11.00 g of an anion exchange resin (product name: DOWEX [registered trademark] MONOSPHERE [registered trademark] 550A, Muromachi Technos Co., Ltd.) and 11.00 g of a cation exchange resin (product name: AMBERLYST [registered trademark] 15JWET, ORGANO CORPORATION). The resultant mixture was stirred at 25° C. to 30° C. for 4 hours and was then filtered.

[0138] GPC analysis showed that the thus obtained reaction product had a weight average molecular weight of 720 relative to standard polystyrenes. The reaction product obtained is estimated to be a copolymer having a structural unit represented by the following formula (5):

##STR00018##

Comparative Synthesis Example 1

[0139] 17.67 g of propylene glycol monomethyl ether acetate (hereinafter, abbreviated as PGMEA in this specification), 5.00 g of EHPE-3150 (product name, manufactured by Daicel Corporation), 3.11 g of 9-anthracenecarboxylic acid, 2.09 g of benzoic acid and 0.62 g of ethyltriphenylphosphonium bromide were added to 7.57 g of PGME. The mixture was heated under reflux in a nitrogen atmosphere for 13 hours. To the resultant solution were added 16 g of a cation exchange resin (product name: AMBERLYST [registered trademark] 15JWET, ORGANO CORPORATION) and 16 g of an anion exchange resin (product name: DOWEX [registered trademark] MONOSPHERE [registered trademark] 550A, Muromachi Technos Co., Ltd.). The resultant mixture was stirred at 25° C. to 30° C. for 4 hours and was then filtered.

[0140] GPC analysis showed that the thus obtained reaction product had a weight average molecular weight of 4,700 relative to standard polystyrenes. The reaction product obtained is estimated to be a copolymer having a structural unit represented by the following formula (3):

##STR00019##

[0141] [Preparation of Resist Underlayer Film-Forming Composition]

Example 1

[0142] 4.90 g of a solution containing 1.26 g of the copolymer obtained in Synthesis Example 1 (the solvent was PGME, and the solid content was 25.74% by mass) was mixed together with 0.25 g of TMOM-BP (product name, manufactured by Honshu Chemical Industry Co., Ltd.), 2.52 g of a 1% by mass PGME solution of K-PURE [registered trademark] TAG2689 (product name, manufactured by King Industries), 6.66 g of PGME, 5.54 g of PGMEA and 0.13 g of a 1% by mass PGME solution of a surfactant (product name: R-30N, manufactured by DIC CORPORATION), thus forming a 7.7% by mass solution. The solution was filtered through a polytetrafluoroethylene microfilter having a pore size of 0.2 μm. A resist underlayer film-forming composition was thus prepared.

Example 2

[0143] 4.63 g of a solution containing 1.26 g of the copolymer obtained in Synthesis Example 2 (the solvent was PGME, and the solid content was 27.23% by mass) was mixed together with 0.25 g of TMOM-BP (product name, manufactured by Honshu Chemical Industry Co., Ltd.), 2.52 g of a 1% by mass PGME solution of K-PURE [registered trademark] TAG2689 (product name, manufactured by King Industries), 6.93 g of PGME, 5.54 g of PGMEA and 0.13 g of a 1% by mass PGME solution of a surfactant (product name: R-30N, manufactured by DIC CORPORATION), thus forming a 7.7% by mass solution. The solution was filtered through a polytetrafluoroethylene microfilter having a pore size of 0.2 μm. A resist underlayer film-forming composition was thus prepared.

Example 3

[0144] 5.06 g of a solution containing 1.26 g of the copolymer obtained in Synthesis Example 3 (the solvent was PGME, and the solid content was 24.95% by mass) was mixed together with 0.25 g of TMOM-BP (product name, manufactured by Honshu Chemical Industry Co., Ltd.), 2.52 g of a 1% by mass PGME solution of K-PURE [registered trademark] TAG2689 (product name, manufactured by King Industries), 6.51 g of PGME, 5.54 g of PGMEA and 0.13 g of a 1% by mass PGME solution of a surfactant (product name: R-30N, manufactured by DIC CORPORATION), thus forming a 7.7% by mass solution. The solution was filtered through a polytetrafluoroethylene microfilter having a pore size of 0.2 μm. A resist underlayer film-forming composition was thus prepared.

Example 4

[0145] 4.19 g of a solution containing 1.26 g of the copolymer obtained in Synthesis Example 4 (the solvent was PGME, and the solid content was 30.12% by mass) was mixed together with 0.25 g of TMOM-BP (product name, manufactured by Honshu Chemical Industry Co., Ltd.), 2.52 g of a 1% by mass PGME solution of K-PURE [registered trademark] TAG2689 (product name, manufactured by King Industries), 7.37 g of PGME, 5.54 g of PGMEA and 0.13 g of a 1% by mass PGME solution of a surfactant (product name: R-30N, manufactured by DIC CORPORATION), thus forming a 7.7% by mass solution. The solution was filtered through a polytetrafluoroethylene microfilter having a pore size of 0.2 μm. A resist underlayer film-forming composition was thus prepared.

Comparative Example 1

[0146] 19.52 g of a solution containing 4.51 g of the copolymer obtained in Comparative Synthesis Example 1 (the solvent was PGME/PGMEA mixed solvent, the same as that used at the time of synthesis, and the solid content was 23.26% by mass) was mixed together with 1.14 g of tetramethoxymethylglycoluril (product name: POWDERLINK [registered trademark] 1174, manufactured by Cytec Industries Incorporated, Japan), 3.41 g of a 1% by mass PGME solution of pyridinium p-toluenesulfonate, 50.68 g of PGME, 14.80 g of PGMEA and 0.45 g of a 1% by mass PGME solution of a surfactant (product name: R-30, manufactured by DIC CORPORATION), thus forming a 6.35% by mass solution. The solution was filtered through a polytetrafluoroethylene microfilter having a pore size of 0.2 μm. A resist underlayer film-forming composition was thus prepared.

[0147] [Test of Dissolution into Photoresist Solvents]

[0148] Each of the resist underlayer film-forming compositions prepared in Examples 1 to 4 and Comparative Example 1 was applied onto a silicon wafer using a spinner. The coating was baked on a hot plate at a temperature according to Table 1 below for 1 minute to form a resist underlayer film (film thickness: 0.2 μm). The resist underlayer film was soaked in a PGME/PGMEA mixed solvent (mixing ratio by mass: 70/30), which was used for photoresist solutions. The resist underlayer films were insoluble in the solvent. The results are indicated as “AA” in Table 1 below.

[0149] [Test of Optical Parameters]

[0150] Each of the resist underlayer film-forming compositions prepared in Examples 1 to 4 and Comparative Example 1 was applied onto a silicon wafer using a spinner. The coating was baked on a hot plate at a temperature according to Table 1 below for 1 minute to form a resist underlayer film (film thickness: 0.2 μm). The resist underlayer film was analyzed with an optical ellipsometer (VUV-VASE VU-302 manufactured by J. A. Woollam) to measure the refractive index (n value) and the attenuation coefficient (k value) at a wavelength of 193 nm. The results are shown in Table 1 below. To ensure for the resist underlayer film to exhibit a sufficient antireflection function, the k value at a wavelength of 193 nm is desirably 0.1 or more and 0.4 or less.

[0151] [Measurement of Dry Etching Rate]

[0152] Each of the resist underlayer film-forming compositions prepared in Examples 1 to 4 and Comparative Example 1 was applied onto a silicon wafer in the same manner as described above to form a resist underlayer film. The dry etching rate of the resist underlayer film was measured with an RIE system manufactured by Samco Inc., using CF.sub.4 as a dry etching gas. The dry etching rate of the resist underlayer film was converted to a relative value when the dry etching rate of Comparative Example 1 was taken as 1.00. The results are shown as the “relative dry etching rate” in Table 1 below. The resist underlayer film from each of the resist underlayer film-forming compositions prepared in Examples 1 to 2 had a sufficiently slower dry etching rate as compared to the dry etching rate of Comparative Example 1. These results indicate that use of the resist underlayer film-forming composition according to the invention as a mask would facilitate the processing of the substrate.

TABLE-US-00001 TABLE 1 Solvent Baking resistance Optical parameters temperature PGME/PGMEA 193 nm Etching Gap-filling (deg. C.) 70/30 n value k value resistance properties Flatness Example 1 250 ∘ 1.38 0.40 0.82 ∘ ∘ Example 2 250 ∘ 1.46 0.36 0.82 ∘ ∘ Example 3 250 ∘ 1.46 0.60 0.86 ∘ ∘ Example 4 250 ∘ 1.49 0.58 0.75 ∘ ∘ Comparative 215 ∘ 1.64 0.26 1.00 x x Example 1

[0153] [Evaluation of Gap-Filling Property]

[0154] Gap-filling property was evaluated using a 200 nm thick SiO.sub.2 substrate having a dense pattern area consisting of 50 nm wide trenches at 100 nm pitches. Each of the resist underlayer film-forming compositions prepared in Examples 1 to 2 and Comparative Examples 1 to 3 was applied onto the substrate, and the coating was baked under predetermined conditions to form a resist underlayer film having a thickness of about 200 nm. The flatness of the substrate was observed using a scanning electron microscope (S-4800) manufactured by Hitachi High-Tech Corporation to confirm whether the resist underlayer film-forming composition had filled the inside of the pattern. Good gap-filling propertiy was obtained in Examples 1 to 2 and Comparative Examples 2 to 3, but voids were found in Comparative Example 1.

[0155] [Test of Coatability on Stepped Substrate]

[0156] To evaluate the coatability on a stepped substrate, the thickness of a coating film formed on a 200 nm thick SiO.sub.2 substrate was compared between on a dense pattern area (DENSE) consisting of 50 nm wide trenches at 100 nm pitches and on an open area (OPEN) free from such patterns. Each of the resist underlayer film-forming compositions from Examples 1 to 2 and Comparative Examples 1 to 3 was applied onto the substrate to form a 150 nm thick film, which was then baked at a predetermined temperature. The coatability of the film onto the stepped substrate was observed with a scanning electron microscope (S-4800) manufactured by Hitachi High-Tech Corporation to measure the difference in film thickness between on the dense area (the patterned area) and on the open area (the pattern-free area) of the stepped substrate (the difference in level present on the film between the dense area and the open area, called the bias), to evaluate the flattening property. The film thicknesses in each of the areas, and the difference in level present on the film are shown in Table 2. In the evaluation of flatness, the smaller the value of bias, the higher the flattening property.

TABLE-US-00002 TABLE 2 DENSE OPEN DENSE/OPEN Film thickness Film thickness Difference in level (nm) (nm) (nm) Example 1 101 135 34 Example 2 95 143 48 Example 3 105 133 28 Example 4 95 149 54 Comparative 70 145 75 Example 1

INDUSTRIAL APPLICABILITY

[0157] The resist underlayer film-forming composition provided according to the present invention has high etching resistance and good optical constants, offers a useful dry etching rate ratio, and exhibits high coatability even on the so-called stepped substrate and can bury the difference in level by forming a flat film having a small variation in film thickness. The present invention also provides a resist underlayer film formed using the resist underlayer film-forming composition, and a method for manufacturing a semiconductor device using the resist underlayer film-forming composition.