JP4482760B2 - Resist protective film material and pattern forming method - Google Patents

Description

  The present invention relates to microfabrication in a manufacturing process of a semiconductor device or the like, particularly in immersion photolithography in which an ArF excimer laser having a wavelength of 193 nm is used as a light source and water is inserted between a projection lens and a wafer to protect the photoresist. The present invention relates to a resist protective film material used as a film material and a resist pattern forming method using the same.

In recent years, with the higher integration and higher speed of LSIs, there has been a demand for finer pattern rules. In the light exposure currently used as a general-purpose technology, the intrinsic resolution limit derived from the wavelength of the light source. Is approaching. As exposure light used for forming a resist pattern, light exposure using a g-ray (436 nm) or i-line (365 nm) of a mercury lamp as a light source has been widely used. As a means for further miniaturization, a method of shortening the exposure wavelength is effective, and for mass production processes after 64 Mbit (process size is 0.25 μm or less) DRAM (Dynamic Random Access Memory). As a light source for exposure, a short wavelength KrF excimer laser (248 nm) was used in place of i-line (365 nm). However, in order to manufacture DRAMs with a density of 256M and 1G or more that require finer processing technology (processing dimensions of 0.2 μm or less), a light source with a shorter wavelength is required, and an ArF excimer has been used for about 10 years. Photolithography using a laser (193 nm) has been studied in earnest. At first, ArF lithography was supposed to be applied from the device fabrication of the 180 nm node, but KrF excimer lithography was extended to 130 nm node device mass production, and full-scale application of ArF lithography is from the 90 nm node. Further, a 65 nm node device is being studied in combination with a lens whose NA is increased to 0.9. The following 45nm node devices which required an advancement to reduce the wavelength of exposure light, F ₂ lithography wavelength 157nm became a candidate. However, the cost of the scanner is increased by using a large amount of expensive CaF ₂ single crystal for the projection lens, and the durability of the soft pellicle is extremely low. Due to various problems, F ₂ lithography was postponed and early introduction of ArF immersion lithography was proposed (Non-patent Document 1: Proc. SPIE Vol. 4690 xxix).

  In ArF immersion lithography, it has been proposed to impregnate water between the projection lens and the wafer. The refractive index of water at 193 nm is 1.44, and it is possible to form a pattern using a lens having an NA of 1.0 or more. Theoretically, the NA can be increased to 1.44. The resolution is improved by the improvement of NA, and the possibility of a 45 nm node is shown by a combination of a lens of NA 1.2 or higher and strong super-resolution technology (Non-patent Document 2: Proc. SPIE Vol. 5040 p724).

  Here, various problems due to the presence of water on the resist film have been pointed out. This includes shape change caused by dissolution of the generated acid or amine compound added to the resist film as a quencher in water, pattern collapse due to swelling, and the like. Therefore, it has been proposed that it is effective to provide a protective film between the resist film and water (Non-patent Document 3: 2nd Immersion Work Shop, July 11, 2003, Resist and Cover Material Investigation Lithography). .

  The protective film on the resist upper layer has been studied as an antireflection film until now. Examples thereof include the ARCOR method disclosed in Patent Documents 1 to 3, Japanese Patent Application Laid-Open Nos. 62-62520, 62-62521, and 60-38821. The ARCOR method is a method including a step of forming a transparent antireflection film on a resist film and peeling off after exposure, and is a method of forming a fine pattern with high accuracy and high alignment accuracy by the simple method. When a perfluoroalkyl compound (perfluoroalkyl polyether, perfluoroalkylamine) of a low refractive index material is used as the antireflection film, the reflected light at the resist-antireflection film interface is greatly reduced, and the dimensional accuracy is improved. Examples of the fluorine-based material include perfluoro (2,2-dimethyl-1,3-dioxole) -tetrafluoroethylene copolymer disclosed in JP-A-5-74700 as well as the above-mentioned materials. Amorphous polymers such as cyclized polymers of fluoro (allyl vinyl ether) and perfluorobutenyl vinyl ether have been proposed.

  However, since the perfluoroalkyl compound has low compatibility with organic substances, chlorofluorocarbon is used as a diluent for controlling the coating film thickness. Therefore, its use has become a problem. Moreover, the said compound had a problem in uniform film formability, and it could not be said that it was enough as an antireflection film. In addition, before development of the photoresist film, the antireflection film had to be peeled off with chlorofluorocarbon. For this reason, there have been significant demerits in practical use, such as the need to add a system for removing the antireflection film to the conventional apparatus and the considerable cost of the fluorocarbon solvent.

  When the antireflection film is peeled off without adding to the conventional apparatus, it is most desirable to peel off using the developing unit. Since the solution used in the developing unit of the photoresist film is an alkaline aqueous solution as a developer and pure water as a rinse solution, it can be said that an antireflection film material that can be easily peeled off with these solutions is desirable. Therefore, many water-soluble antireflection film materials and pattern forming methods using these have been proposed. For example, Patent Documents 5 and 6: JP-A-6-273926, Patent 2803549, and the like.

  However, since the water-soluble protective film is dissolved in water during exposure, it cannot be used for immersion lithography. On the other hand, water-insoluble fluorine-based polymers have the problem that a special flon-based release agent is required and that a specially designed flon-based release cup is required. A resist protective film has been demanded.

  An ideal value for the antireflection film on the resist upper layer is the square root of a value obtained by multiplying the refractive index of the atmosphere by the refractive index of the resist film. Since the refractive index at 193 nm of the methacrylic and cycloolefin polymer-based ArF resist is about 1.72, if the exposure in the atmosphere, 1.31 of the square root of 1.72 is the optimal refractive index of the upper layer film. is there. In the case of immersion exposure, for example, when water is used as the immersion material, a square root of 1.57, which is obtained by multiplying the refractive index of water by 1.44 and the refractive index of the resist film by 1.72, is optimal.

  Here, the refractive index of the fluoropolymer reported in 2nd Immersion Work Shop, July 11, 2003, Resist and Cover Material Investigation for Immersion Lithography is as low as 1.38, which is greatly deviated from the optimum value.

Proc. SPIE Vol. 4690 xxix Proc. SPIE Vol. 5040 p724 2nd Immersion Work Shop, July 11, 2003, Resist and Cover Material Investing for Immersion Lithography 14th Photoreaction / Electronic Materials Workshop Lecture Proceedings Life Extension of Photolithography and Resist Materials p27 (2005) JP-A-62-62520 JP-A-62-62521 JP 60-38821 A JP-A-5-74700 JP-A-6-273926 Japanese Patent No. 2803549

  The present invention has been made in view of the above circumstances, and enables excellent immersion lithography, and can be removed at the same time as development of a photoresist layer, and has excellent process applicability. An object of the present invention is to provide a film material and a pattern forming method using such a material.

  As a result of intensive studies to achieve the above object, the present inventors have formed a film of a polymer compound having a partial structure represented by the following general formula (1) on a resist film as a resist protective film material In addition, this protective film (resist upper layer film) is water-insoluble and can be dissolved in an alkaline aqueous solution, and does not mix with the resist layer, and can be peeled off together with development during development with alkaline water. It has been found that process applicability is considerably widened, and the present invention has been made.

  More specifically, the hexafluoroalcohol group has been studied as a resist protective film for immersion exposure because it has alkali solubility and high water repellency. However, when only the hexafluoroalcohol group is used as the alkali-soluble group, there is a problem that the resist pattern after development becomes a taper shape or the film is reduced. On the other hand, it was shown that it is effective to copolymerize a repeating unit having a carboxyl group in order to suppress film loss after development (Japanese Patent Application No. 2004-229085). However, due to the high hydrophilicity of the carboxyl group, problems such as elution of the additive into water due to penetration of water, which is immersion water, and remaining water on the surface of the protective film after scanning have occurred. There is a need to develop alkali-soluble groups that are more hydrophobic than normal carboxyl groups. Here, the calculation example of cLogP of the following monomer is shown. The monomer forming the recurring unit (2) described later of the present invention has a very high cLogP, indicating excellent water repellency.

  The present inventors have reported that an acid generator and a basic substance added to a resist are detected from the analysis result of water when a resist protective film is applied and water is immersed on the resist protective film. (Non-patent Document 4: Proceedings of the 14th Photoreaction / Electronic Materials Study Group Lecture Prolongation of Photolithography and Resist Materials p27 (2005)). At this time, it was estimated that the detected amount of the basic substance was larger than that of the acid generator, and the protective film of the basic substance was penetrated. In addition, the resist shape after development when a resist protective film is applied is often reduced or tapered, and this also supports the reduction of basic substances from the resist film and the penetration of the protective film of basic substances. ing. In particular, when a polymer having hexafluoroalcohol is used, the film thickness of the resist pattern is reduced, the taper shape and the amount of basic substances by immersion water analysis are remarkably large, and conversely, when a polymer having a carboxyl group is used, The resist protective film having a carboxyl group and a sulfo group was proposed (Japanese Patent Application No. 2004-121506). Since the carboxyl group and the sulfo group have higher acidity than hexafluoroalcohol, it is considered that the carboxyl group and the sulfo group are strongly bonded to the basic substance and the basic substance is effectively blocked in the protective film.

  However, when a resist protective film using a polymer having a carboxyl group and a sulfo group is subjected to scan exposure, water droplets remain on the protective film, and PEB (post-exposure baking) and development are performed with water droplets remaining on the protective film. The acid generated inside moved to the water droplets, resulting in a defect that bridged the lines. This is presumably because water droplets remain on the protective film after the scan exposure because the hydrophilicity of the carboxyl group and the sulfo group is high. For this reason, development of a protective film having higher water repellency and capable of suppressing leakage from the resist film and not deteriorating the resist pattern shape after development is desired, but the part represented by the following general formula (1) The inventors have found that it is effective to use a film of a polymer compound having a structure as a resist upper layer film, and have reached the present invention.

（式中、Ｒ¹は水素原子、フッ素原子又はＣＦ₃である。）
請求項２：
下記一般式（２）で示される繰り返し単位ａ及び／又は下記一般式（３）で示される繰り返し単位ｂを有する高分子化合物を含むことを特徴とする請求項１記載のレジスト保護膜材料。

（式中、Ｒ¹は水素原子、フッ素原子又はＣＦ₃、Ｒ²は水素原子又はメチル基、Ｒ³は炭素数１〜１０の直鎖状、分岐状又は環状のアルキレン基、Ｒ⁴は単結合、又は−Ｃ（＝Ｏ）−、Ｒ⁵は炭素数１〜１０の直鎖状又は分岐状のアルキレン基であり、フッ素原子を有していてもよい。ｎは１〜６の整数である。）
請求項３：
高分子化合物が、更に下記式で示されるいずれかのカルボキシル基を有する繰り返し単位を含有する請求項２記載のレジスト保護膜材料。

請求項４：
高分子化合物が、更に下記式で示されるいずれかのフルオロアルコールを有する繰り返し単位を含有する請求項２又は３記載のレジスト保護膜材料。

請求項５：
高分子化合物が、更に下記式で示されるいずれかのパーフルオロアルキル基を有する繰り返し単位を含有する請求項２〜４のいずれか１項記載のレジスト保護膜材料。

請求項６：
更に、上記高分子化合物を溶解する溶媒を含有する請求項１〜５のいずれか１項記載のレジスト保護膜材料。
請求項７：
ウエハーに形成したフォトレジスト層上にレジスト上層膜材料による保護膜を形成し、水中で露光を行った後、現像を行う液浸リソグラフィーによるパターン形成方法において、上記レジスト上層膜材料として請求項１〜６のいずれか１項記載のレジスト保護膜材料を用いることを特徴とするパターン形成方法。
請求項８：
液浸リソグラフィーが、１８０〜２５０ｎｍの範囲の露光波長を用い、投影レンズとウエハーの間に水を挿入させたものである請求項７記載のパターン形成方法。
請求項９：
露光後に行う現像工程において、アルカリ現像液によりフォトレジスト層の現像とレジスト上層膜材料の保護膜の剥離とを同時に行う請求項７又は８記載のパターン形成方法。 Accordingly, the present invention provides the following resist protective film material and pattern forming method.
Claim 1:
A resist protective film as the resist upper film material in the pattern forming method by immersion lithography, in which a protective film made of a resist upper film material is formed on a photoresist layer formed on a wafer, exposed in water, and then developed. a material, seen containing a polymer compound having a partial structure represented by the following general formula (1), the resist protective film material for liquid immersion lithography, which is a soluble in an aqueous alkaline solution in a water-insoluble.

(In the formula, R ¹ is a hydrogen atom, a fluorine atom or CF _3. )
Claim 2:
2. The resist protective film material according to claim 1, comprising a polymer compound having a repeating unit a represented by the following general formula (2) and / or a repeating unit b represented by the following general formula (3).

(In the formula, R ¹ is a hydrogen atom, a fluorine atom or CF ₃ , R ² is a hydrogen atom or a methyl group, R ³ is a linear, branched or cyclic alkylene group having 1 to 10 carbon atoms, and R ⁴ is a single atom. The bond, or —C (═O) —, R ⁵ is a linear or branched alkylene group having 1 to 10 carbon atoms and may have a fluorine atom, and n is an integer of 1 to 6. is there.)
Claim 3:
The resist protective film material according to claim 2, wherein the polymer compound further contains a repeating unit having any one of the carboxyl groups represented by the following formula.

Claim 4:
The resist protective film material according to claim 2 or 3, wherein the polymer compound further contains a repeating unit having any one of the fluoroalcohols represented by the following formula.

Claim 5:
The resist protective film material according to any one of claims 2 to 4, wherein the polymer compound further contains a repeating unit having any perfluoroalkyl group represented by the following formula.

Claim 6 :
Furthermore, the resist protective film material of any one of Claims 1-5 containing the solvent which melt | dissolves the said high molecular compound.
According to claim 7:
A protective film of a resist upper layer film material is formed on a photoresist layer formed on the wafer, after exposure in water, in the pattern forming method according to the immersion lithography to perform development, claim 1 as the resist upper layer film material 7. A pattern forming method comprising using the resist protective film material according to claim 6 .
Claim 8 :
8. The pattern forming method according to claim 7 , wherein the immersion lithography uses an exposure wavelength in a range of 180 to 250 nm and water is inserted between the projection lens and the wafer.
Claim 9 :
In the developing step carried out after the exposure, a pattern forming method according to claim 7 or 8, wherein simultaneously the separation of the protective film of the developing and resist upper layer film material of the photoresist layer by an alkali developer.

  By forming a film of a polymer compound having a partial structure represented by the general formula (1) according to the present invention on a resist film as a resist protective film material, it is water-insoluble and can be dissolved in an alkaline aqueous solution. In addition, a protective film (resist upper layer film) that can be peeled off together with development is formed at the time of development with alkaline water without being mixed with the resist layer, and the process applicability is considerably widened.

  In particular, the resist protective film material of the present invention is a pattern forming method by immersion lithography in which a protective film made of a resist upper layer film material is formed on a photoresist layer formed on a wafer, exposed in water, and then developed. The polymer is used as a material for the resist upper layer film, and is characterized by adding a polymer compound having a partial structure represented by the following general formula (1).

（式中、Ｒ¹は水素原子、フッ素原子又はＣＦ₃であり、好ましくはフッ素原子又はＣＦ₃である。）

(In the formula, R ¹ is a hydrogen atom, a fluorine atom or CF ₃ , preferably a fluorine atom or CF _3. )

  Examples of the repeating unit of the polymer compound having the partial structure represented by the general formula (1) include units represented by the following general formulas (2) and (3).

（式中、Ｒ¹は水素原子、フッ素原子又はＣＦ₃、好ましくはフッ素原子又はＣＦ₃、Ｒ²は水素原子又はメチル基、Ｒ³は炭素数１〜１０の直鎖状、分岐状又は環状のアルキレン基、Ｒ⁴は単結合、又は−Ｃ（＝Ｏ）−、Ｒ⁵は炭素数１〜１０の直鎖状又は分岐状のアルキレン基であり、フッ素原子を有していてもよい。ｎは１〜６の整数である。）

(Wherein R ¹ is a hydrogen atom, a fluorine atom or CF ₃ , preferably a fluorine atom or CF ₃ , R ² is a hydrogen atom or a methyl group, and R ³ is a linear, branched or cyclic group having 1 to 10 carbon atoms. , R ⁴ is a single bond, or —C (═O) —, R ⁵ is a linear or branched alkylene group having 1 to 10 carbon atoms, and may have a fluorine atom. n is an integer of 1-6.)

  In this case, as the polymer compound having the partial structure of the formula (1), a polymer having a repeating unit of the formulas (2) and (3) is preferable, and the dissolution rate in water is 0.1 Å (angstrom) / s or less. A resist protective film having a dissolution rate of a developing solution of 2.38 mass% tetramethylammonium hydroxide aqueous solution of 300 Å / s or more can be formed.

  Specific examples of the repeating units a and b represented by the general formulas (2) and (3) are shown below.

  As the repeating unit of the polymer for resist protective film material of the present invention, the repeating unit a represented by the general formula (2) and / or the repeating unit b represented by the general formula (3) are essential, but other carboxyls The repeating unit c having a group can be copolymerized. The repeating unit c can be exemplified below.

  Moreover, the repeating unit d which has a fluoro alcohol can be copolymerized. Specific examples of the repeating unit d can be given below.

  Furthermore, in order to prevent mixing with the resist film, a repeating unit e having a perfluoroalkyl group can be copolymerized. The repeating unit e can be exemplified below.

  The ratio of the repeating units a, b, c, d, e is 0 ≦ a ≦ 1.0, 0 ≦ b ≦ 1.0, 0 <a + b ≦ 1.0, 0 ≦ c ≦ 0.9, 0 ≦ d. ≦ 0.9, 0 ≦ e ≦ 0.9, preferably 0 ≦ a ≦ 0.8, 0 ≦ b ≦ 0.8, 0.1 ≦ a + b ≦ 0.8, 0 ≦ c ≦ 0.6, 0 ≦ d ≦ 0.8, 0 ≦ e ≦ 0.8, and a + b + c + d + e = 1.

  Here, a + b + c + d + e = 1 means that in a polymer compound containing repeating units a, b, c, d and e, the total amount of repeating units a, b, c, d and e is the total amount of all repeating units. It shows that it is 100 mol%.

  The polymer compound of the present invention has a polystyrene-reduced weight average molecular weight of 1,000 to 500,000, preferably 2,000 to 30,000, as determined by gel permeation chromatography (GPC). If the weight average molecular weight is too small, mixing with the resist material occurs, or it becomes easy to dissolve in water. If it is too large, there may be a problem in film formability after spin coating, or the alkali solubility may be lowered.

  In order to synthesize these polymer compounds, as one method, a monomer having an unsaturated bond for obtaining repeating units a to e is added to a radical initiator in an organic solvent, and heat polymerization is performed to obtain a polymer. A compound can be obtained. Examples of the organic solvent used at the time of polymerization include toluene, benzene, tetrahydrofuran, diethyl ether, dioxane, methanol, ethanol, isopropanol and the like. As polymerization initiators, 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2-azobis (2-methylpropionate) ), Benzoyl peroxide, lauroyl peroxide and the like, and preferably polymerized by heating to 50 to 80 ° C. The reaction time is 2 to 100 hours, preferably 5 to 20 hours.

  The resist protective film material of the present invention is preferably used by dissolving the polymer compound in a solvent. In this case, it is preferable to use a solvent so that the concentration of the polymer compound is 0.1 to 20% by mass, particularly 0.5 to 10% by mass, from the viewpoint of film formability by spin coating.

  The solvent used is not particularly limited, but a solvent that dissolves the resist layer is not preferable. For example, ketones such as cyclohexanone and methyl-2-n-amyl ketone used as a resist solvent, 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol Alcohols such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate , Ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, 3-ethoxy Ethyl propionate, acetate tert- butyl, tert- butyl propionate, and esters such as propylene glycol monobutyl -tert- butyl ether acetate is not preferable.

  Examples of the solvent that does not dissolve the resist layer include non-polar solvents such as higher alcohols having 4 or more carbon atoms, toluene, xylene, anisole, hexane, and cyclohexane. In particular, higher alcohols having 4 or more carbon atoms are preferably used. Specifically, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, tert-amyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-diethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl 2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentane 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol Is mentioned.

On the other hand, a fluorine-based solvent can be preferably used because it does not dissolve the resist layer.
Examples of such fluorine-substituted solvents include 2-fluoroanisole, 3-fluoroanisole, 4-fluoroanisole, 2,3-difluoroanisole, 2,4-difluoroanisole, 2,5-difluoroanisole, 5, 8-difluoro-1,4-benzodioxane, 2,3-difluorobenzyl alcohol, 1,3-difluoro-2-propanol, 2 ′, 4′-difluoropropiophenone, 2,4-difluorotoluene, trifluoroacetaldehyde Ethyl hemiacetal, trifluoroacetamide, trifluoroethanol, 2,2,2-trifluoroethyl butyrate, ethyl heptafluorobutyrate, ethyl heptafluorobutyl acetate, ethyl hexafluoroglutaryl methyl, ethyl-3-hydroxy 4,4,4-trifluorobutyrate, ethyl-2-methyl-4,4,4-trifluoroacetoacetate, ethyl pentafluorobenzoate, ethyl pentafluoropropionate, ethyl pentafluoropropynyl acetate, ethyl perfluoroocta Noate, ethyl-4,4,4-trifluoroacetoacetate, ethyl-4,4,4-trifluorobutyrate, ethyl-4,4,4-trifluorocrotonate, ethyltrifluorosulfonate, ethyl-3 -(Trifluoromethyl) butyrate, ethyl trifluoropyruvate, S-ethyl trifluoroacetate, fluorocyclohexane, 2,2,3,3,4,4,4-heptafluoro-1-butanol, 1,1,1 , 2,2,3,3-heptafluoro-7,7-dimethyl Til-4,6-octanedione, 1,1,1,3,5,5,5-heptafluoropentane-2,4-dione, 3,3,4,4,5,5,5-heptafluoro- 2-pentanol, 3,3,4,4,5,5,5-heptafluoro-2-pentanone, isopropyl 4,4,4-trifluoroacetoacetate, methyl perfluorodenanoate, methyl perfluoro (2 -Methyl-3-oxahexanoate), methyl perfluorononanoate, methyl perfluorooctanoate, methyl-2,3,3,3-tetrafluoropropionate, methyl trifluoroacetoacetate, 1,1, 1,2,2,6,6,6-octafluoro-2,4-hexanedione, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol, 1H, H, 2H, 2H-perfluoro-1-decanol, perfluoro (2,5-dimethyl-3,6-dioxane anionic) acid methyl ester, 2H-perfluoro-5-methyl-3,6-dioxanonane, 1H , 1H, 2H, 3H, 3H-perfluorononane-1,2-diol, 1H, 1H, 9H-perfluoro-1-nonanol, 1H, 1H-perfluorooctanol, 1H, 1H, 2H, 2H-perfluoro Octanol, 2H-perfluoro-5,8,11,14-tetramethyl-3,6,9,12,15-pentaoxaoctadecane, perfluorotributylamine, perfluorotrihexylamine, perfluoro-2,5 8-trimethyl-3,6,9-trioxadodecanoic acid methyl ester, perfluorotripentyl Min, perfluorotripropylamine, 1H, 1H, 2H, 3H, 3H-perfluoroundecane-1,2-diol, trifluorobutanol 1,1,1-trifluoro-5-methyl-2,4-hexanedione 1,1,1-trifluoro-2-propanol, 3,3,3-trifluoro-1-propanol, 1,1,1-trifluoro-2-propyl acetate, perfluorobutyltetrahydrofuran, perfluoro (butyl Tetrahydrofuran), perfluorodecalin, perfluoro (1,2-dimethylcyclohexane), perfluoro (1,3-dimethylcyclohexane), propylene glycol trifluoromethyl ether acetate, propylene glycol methyl ether trifluoromethyl acetate, trifluorome Butyl butyl acetate, methyl 3-trifluoromethoxypropionate, perfluorocyclohexanone, propylene glycol trifluoromethyl ether, butyl trifluoroacetate, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione 1,1,1,3,3,3-hexafluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 2,2,3,4 , 4,4-hexafluoro-1-butanol, 2-trifluoromethyl-2-propanol, 2,2,3,3-tetrafluoro-1-propanol, 3,3,3-trifluoro-1-propanol, 4,4,4-trifluoro-1-butanol and the like can be used, and one of these can be used alone or in admixture of two or more. But it is not limited thereto.

The pattern forming method using the water-insoluble and alkali-soluble resist protective film (upper layer film) material of the present invention will be described.
First, a water-insoluble and alkali-soluble resist protective film (upper film) material is formed on the photoresist layer by spin coating or the like. The film thickness is preferably in the range of 10 to 500 nm. After the spin coating, the solvent is volatilized by baking at 40 to 130 ° C. for 10 to 300 seconds. Then, it exposes in water by KrF or ArF immersion lithography. After exposure, water is spin-dried, post-exposure baking (PEB) is performed, and development is performed with an alkali developer for 10 to 300 seconds. As the alkaline developer, a 2.38 mass% tetramethylammonium hydroxide aqueous solution is generally widely used, and the resist protective film (upper layer film) of the present invention is peeled off and the resist film is developed simultaneously.

  The type of resist material is not particularly limited. It may be a positive type or a negative type, and may be an ordinary hydrocarbon-based single layer resist material or a bilayer resist material containing silicon atoms. As a resist material in KrF exposure, a polymer in which a hydrogen atom of a hydroxy group or a carboxyl group of a polyhydroxystyrene or polyhydroxystyrene- (meth) acrylate copolymer is substituted with an acid labile is preferably used as a base resin.

  The resist material in ArF exposure must have a structure that does not contain aromatics as a base resin. Specifically, polyacrylic acid and its derivatives, norbornene derivative-maleic anhydride alternating polymer, and polyacrylic acid or its derivatives. Tri- or quaternary copolymer, tetracyclododecene derivative-maleic anhydride alternating polymer and polyacrylic acid or a derivative thereof, ternary or quaternary copolymer, norbornene derivative-maleimide alternating polymer and polyacrylic acid or the like Tri- or quaternary copolymers with derivatives, tetracyclododecene derivative-maleimide alternating polymers and ternary or quaternary copolymers with polyacrylic acid or its derivatives, and two or more of these, or polynorbornene and One or more polymer polymers selected from metathesis ring-opening polymers are Used Mashiku.

EXAMPLES Hereinafter, although a synthesis example, an Example, and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In the examples, GPC is gel permeation chromatography, and the weight average molecular weight (Mw) and number average molecular weight (Mn) in terms of polystyrene were determined.
Moreover, the structural formula of the monomers 1-8 used by the synthesis example is shown below.

[Synthesis Example 1]
Monomer 1 (18 g), monomer 8 (12 g), and methanol (40 g) as a solvent were added to a 200 mL flask. The reaction vessel was cooled to −70 ° C. in a nitrogen atmosphere, and vacuum degassing and nitrogen flow were repeated three times. After raising the temperature to room temperature, 3 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as a polymerization initiator, and the temperature was raised to 65 ° C., followed by reaction for 25 hours. The reaction solution was crystallized from hexane to isolate the resin. The composition of the obtained resin was ¹ H-NMR, the molecular weight was confirmed by GPC, and Example polymer 1 was obtained.

[Synthesis Example 2]
32 g of monomer 2, 6 g of monomer 8 and 40 g of methanol as a solvent were added to a 200 mL flask. The reaction vessel was cooled to −70 ° C. in a nitrogen atmosphere, and vacuum degassing and nitrogen flow were repeated three times. After raising the temperature to room temperature, 3 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as a polymerization initiator, and the temperature was raised to 65 ° C., followed by reaction for 25 hours. The reaction solution was crystallized from hexane to isolate the resin. The composition of the obtained resin was confirmed by ¹ H-NMR, and the molecular weight was confirmed by GPC.

[Synthesis Example 3]
7.5 g of monomer 1, 7.3 g of monomer 7, 15 g of monomer 8 and 40 g of methanol as a solvent were added to a 200 mL flask. The reaction vessel was cooled to −70 ° C. in a nitrogen atmosphere, and vacuum degassing and nitrogen flow were repeated three times. After raising the temperature to room temperature, 3 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as a polymerization initiator, and the temperature was raised to 65 ° C., followed by reaction for 25 hours. The reaction solution was crystallized from hexane to isolate the resin. The composition of the obtained resin was confirmed by ¹ H-NMR, and the molecular weight was confirmed by GPC.

[Synthesis Example 4]
7.5 g of monomer 1, 12.5 g of monomer 6, 15 g of monomer 8 and 40 g of methanol as a solvent were added to a 200 mL flask. The reaction vessel was cooled to −70 ° C. in a nitrogen atmosphere, and vacuum degassing and nitrogen flow were repeated three times. After raising the temperature to room temperature, 3 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as a polymerization initiator, and the temperature was raised to 65 ° C., followed by reaction for 25 hours. The reaction solution was crystallized from hexane to isolate the resin. The composition of the obtained resin ¹ H-NMR, the molecular weight was confirmed by GPC, and was designated Inventive Polymer 4.

[Synthesis Example 5]
5.6 g of monomer 3, 12.5 g of monomer 6, 15 g of monomer 8 and 40 g of methanol as a solvent were added to a 200 mL flask. The reaction vessel was cooled to −70 ° C. in a nitrogen atmosphere, and vacuum degassing and nitrogen flow were repeated three times. After raising the temperature to room temperature, 3 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as a polymerization initiator, and the temperature was raised to 65 ° C., followed by reaction for 25 hours. The reaction solution was crystallized from hexane to isolate the resin. The composition of the obtained resin was confirmed by ¹ H-NMR, and the molecular weight was confirmed by GPC.

[Synthesis Example 6]
Into a 200 mL flask, 8.5 g of monomer 4, 7.2 g of monomer 7, 15 g of monomer 8 and 40 g of methanol as a solvent were added. The reaction vessel was cooled to −70 ° C. in a nitrogen atmosphere, and vacuum degassing and nitrogen flow were repeated three times. After raising the temperature to room temperature, 3 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as a polymerization initiator, and the temperature was raised to 85 ° C. and reacted for 25 hours. The reaction solution was crystallized from hexane to isolate the resin. The composition of the obtained resin was confirmed by ¹ H-NMR, and the molecular weight was confirmed by GPC.

[Synthesis Example 7]
To a 200 mL flask, 12.5 g of monomer 5, 7.2 g of monomer 7, 15 g of monomer 8 and 40 g of methanol as a solvent were added. The reaction vessel was cooled to −70 ° C. in a nitrogen atmosphere, and vacuum degassing and nitrogen flow were repeated three times. After raising the temperature to room temperature, 3 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as a polymerization initiator, and the temperature was raised to 85 ° C. and reacted for 25 hours. The reaction solution was crystallized from hexane to isolate the resin. The composition of the obtained resin was ¹ H-NMR, the molecular weight was confirmed by GPC, and Example polymer 7 was obtained.

[Comparative Synthesis Example 1]
To a 200 mL flask, 35 g of monomer 6, 9 g of monomer 8 and 40 g of methanol as a solvent were added. The reaction vessel was cooled to −70 ° C. in a nitrogen atmosphere, and vacuum degassing and nitrogen flow were repeated three times. After raising the temperature to room temperature, 3 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as a polymerization initiator, and the temperature was raised to 65 ° C., followed by reaction for 25 hours. The reaction solution was crystallized from hexane to isolate the resin. The composition of the obtained resin was confirmed by ¹ H-NMR, the molecular weight was confirmed by GPC, and Comparative polymer 1 was obtained.

[Examples and Comparative Examples]
Examples Polymers 1 to 7 and Comparative Example Polymer 1 used the polymers shown in the above synthesis examples. 0.5 g of each of Examples Polymer 1 to 7 and Comparative Example Polymer 1 was dissolved in 25 g of isobutyl alcohol and filtered through a 0.2 micron size polypropylene filter to prepare a resist protective film solution.

  After spin-coating a resist protective film on a silicon substrate and baking at 100 ° C. for 60 seconds, a protective film having a thickness of 50 nm was prepared. A. The refractive index of the protective film at a wavelength of 193 nm was determined using spectroscopic ellipsometry manufactured by Woollam. The results are shown in Table 1.

  Next, the wafer on which the resist protective film was formed by the above method was rinsed with pure water for 5 minutes, and the change in film thickness was observed. The results are shown in Table 2.

  Further, the wafer on which the resist protective film was formed by the above method was developed with an aqueous 2.38 mass% tetramethylammonium hydroxide (TMAH) solution, and the change in film thickness was observed. The results are shown in Table 3.

Furthermore, 5 g of resist polymer shown below, 0.25 g of PAG, and 0.6 g of tri-n-butylamine as a quencher were dissolved in 55 g of a propylene glycol monoethyl ether acetate (PGMEA) solution to obtain a 0.2 micron size polypropylene filter. And a resist solution was prepared. A resist solution was applied on an 87 nm film thickness of an anti-reflective film ARC-29A manufactured by Nissan Chemical Co., Ltd. produced on a Si substrate, and baked at 120 ° C. for 60 seconds to produce a 150 nm thick resist film. A resist protective film was applied thereon and baked at 100 ° C. for 60 seconds. In order to reproduce the simulated immersion exposure, the exposed film was rinsed with pure water for 5 minutes. Expose with Nikon ArF scanner S307E (NA0.85 σ0.93 4/5 ring illumination, 6% halftone phase shift mask), rinse for 5 minutes while applying pure water, post-exposure at 110 ° C for 60 seconds Arbake (PEB) was performed, and development was performed for 60 seconds with a 2.38 mass% TMAH developer.
A normal process without exposure, pure water rinsing, PEB, development, and post-exposure pure water rinsing was also performed without a protective film.
The wafer was cleaved, and the pattern shape and sensitivity of the 75 nm line and space were compared. The results are shown in Table 4.

When pure water rinsing was performed after exposure without a protective film, a T-top shape was obtained. This is probably because the generated acid was dissolved in water. On the other hand, when the protective film of the present invention was used, the shape did not change. In the case of a protective film containing only hexafluoroalcohol as a soluble group, the resist shape after development was reduced and became a tapered shape.

Claims (9)

A resist protective film as the resist upper film material in the pattern forming method by immersion lithography, in which a protective film made of a resist upper film material is formed on a photoresist layer formed on a wafer, exposed in water, and then developed. a material, seen containing a polymer compound having a partial structure represented by the following general formula (1), the resist protective film material for liquid immersion lithography, which is a soluble in an aqueous alkaline solution in a water-insoluble.

(In the formula, R ¹ is a hydrogen atom, a fluorine atom or CF _3. ) 2. The resist protective film material according to claim 1, comprising a polymer compound having a repeating unit a represented by the following general formula (2) and / or a repeating unit b represented by the following general formula (3).

(In the formula, R ¹ is a hydrogen atom, a fluorine atom or CF ₃ , R ² is a hydrogen atom or a methyl group, R ³ is a linear, branched or cyclic alkylene group having 1 to 10 carbon atoms, and R ⁴ is a single atom. The bond, or —C (═O) —, R ⁵ is a linear or branched alkylene group having 1 to 10 carbon atoms and may have a fluorine atom, and n is an integer of 1 to 6. is there.) The resist protective film material according to claim 2, wherein the polymer compound further contains a repeating unit having any one of the carboxyl groups represented by the following formula.

The resist protective film material according to claim 2 or 3, wherein the polymer compound further contains a repeating unit having any one of the fluoroalcohols represented by the following formula.

The resist protective film material according to any one of claims 2 to 4, wherein the polymer compound further contains a repeating unit having any perfluoroalkyl group represented by the following formula.

Furthermore, the resist protective film material of any one of Claims 1-5 containing the solvent which melt | dissolves the said high molecular compound. A protective film of a resist upper layer film material is formed on a photoresist layer formed on the wafer, after exposure in water, in the pattern forming method according to the immersion lithography to perform development, claim 1 as the resist upper layer film material 7. A pattern forming method comprising using the resist protective film material according to claim 6 . 8. The pattern forming method according to claim 7 , wherein the immersion lithography uses an exposure wavelength in a range of 180 to 250 nm and water is inserted between the projection lens and the wafer. In the developing step carried out after the exposure, a pattern forming method according to claim 7 or 8, wherein simultaneously the separation of the protective film of the developing and resist upper layer film material of the photoresist layer by an alkali developer.