JP4687893B2 - Resist protective film material and pattern forming method - Google Patents

Description

  The present invention provides a resist for protecting a photoresist layer in immersion photolithography in which microfabrication in a manufacturing process of a semiconductor element or the like, in particular, 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. The present invention relates to a resist protective film material used as an upper layer film material and a pattern forming method using the same.

In recent years, with the higher integration and higher speed of LSIs, there is a demand for finer pattern rules. In 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. Photography using a laser (193 nm) has been studied in earnest. Initially, 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. For the next 45 nm node device, the exposure wavelength has been shortened, and F ₂ lithography with a wavelength of 157 nm was nominated. However, the cost of the scanner is increased by using a large amount of expensive CaF ₂ single crystal for the projection lens, the optical system is changed due to the introduction of the hard pellicle because the durability of the soft pellicle is extremely low, and the etching resistance of the resist film is reduced. 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), which is a low refractive index material, is used as the antireflection film, the reflected light at the resist film-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. Further, before developing 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 photoresist developing unit 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 problems that a special fluorocarbon-based release agent is required and that a special cup for fluorocarbon solvents is required. There was a need for a protective film.

Here, a developer-soluble top coat based on methacrylate pendant of hexafluoroalcohol has been proposed (Non-patent Document 4: J. Photopolymer Sci. And Technol. Vol. 18 No. 5 p615 (2005)). ). This has a high Tg of 150 ° C., high alkali solubility, and good compatibility with a resist film.
In order to increase the scanning speed of the exposure machine, it is necessary to increase the water slidability of the photoresist protective film in contact with water. In order to increase the water slidability, it is reported that it is effective not only to increase the water repellency but also to combine different types of water repellency groups to form a microdomain structure. For example, a fluororesin grafted with siloxane exhibits extremely excellent water slidability (Non-patent Document 5: XXIV FATIPEC Congress Book, Vol. B, p15-38 (1997)). This is superior in lubricity than fluororesin alone and silicone resin alone, and TEM observation shows that a domain structure of 10 to 20 nm is formed (Non-patent Document 6: Progress in Organic). Coatings, 31, p97-104 (1997)).

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 J. et al. Photopolymer Sci. and Technol. Vol. No. 18 5 p615 (2005) XXIV FATIPEC Congress Book. Vol. B, p15-38 (1997) Progress in Organic Coatings, 31, p97-104 (1997) 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 makes it possible to perform good immersion lithography, and can be removed at the same time as development of a photoresist layer, and has excellent process applicability and resist protection for immersion lithography. 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 inventors of the present invention are promising as a photoresist protective film material having very high lubricity due to a repeating unit having both a fluoroalkyl group and an alkyl group as hydrophobic groups. I found out.

  That is, according to Non-Patent Document 6, the fluorine atom of the fluoroalkyl group is weakly bonded to the hydrogen atom of the water molecule. On the other hand, the alkyl group is bonded to oxygen in the water molecule. In the calculation by the molecular orbital method, the fluorine-hydrogen bond distance between the fluoroalkyl group and water is 0.187 nm, which is shorter than the hydrogen-oxygen bond distance between alkyl group-water and 0.252 nm, and the fluoroalkyl group is the alkyl group. It is shown to be at a shorter bond distance with water molecules than. If the bond distance with water molecules is short, the sliding property is lowered, which is not preferable. Here, the orientation angle to the water molecule aggregate is shown between the fluoroalkyl group and the alkyl group, and each orientation angle is different.

  On the other hand, the present inventors tried to use both a fluoroalkyl group and an alkyl group as a water-repellent group in order to increase the bond distance to water (Japanese Patent Application No. 2005-301197). Here, a blend of a polymer having a fluoroalkyl group and a polymer having an alkyl group, or copolymerization of a repeating unit having a fluoroalkyl group and a repeating unit having an alkyl group, provides unprecedented high water slidability. Was able to. When a fluoroalkyl group and an alkyl group coexist, the optimum orientation position of water with respect to each other is different, so that a repulsive force acts between the water repellent group and water, and a long water-bonding distance increases the water-sliding property. It is thought that I was able to get.

  Further, in the present invention, the presence of both a fluoroalkyl group and an alkyl group in one molecule achieves the effect of further increasing the repulsive force with water, thereby having an unprecedented excellent water slidability. A protective film for immersion lithography could be obtained and the present invention was completed.

（式中、Ｒ ¹ 、Ｒ ² のいずれか一方は炭素数１〜２０のアルキル基であり、他方は炭素数１〜２０のフッ素化されたアルキル基である。Ｒ ³ 、Ｒ ⁴ のいずれか一方は炭素数１〜２０のアルキル基であり、他方は炭素数１〜２０のフッ素化されたアルキル基であり、エステル基及び／又はエーテル基を含んでいてもよい。Ｘは−Ｃ（＝Ｏ）−、−Ｏ−、−Ｏ−Ｃ（＝Ｏ）−であり、ｎは０〜３の整数、ｍは０又は１である。）
請求項２：
高分子化合物が、更にアルカリ溶解性の繰り返し単位を含む請求項１記載のレジスト保護膜材料。
請求項３：
アルカリ溶解性の繰り返し単位が、カルボキシル基又はα−フルオロアルコールを有する繰り返し単位である請求項２記載のレジスト保護膜材料。
請求項４：
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、２又は３記載のレジスト保護膜材料。
請求項５：
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、露光を行った後、現像を行う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乃至４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６：
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乃至４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７：
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６記載のパターン形成方法。
請求項８：
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５、６又は７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 material for immersion lithography , comprising using a polymer compound containing a repeating unit having both a fluoroalkyl group and an alkyl group represented by the following repeating unit a1 or a2 .

(In the formula, ^one of R ¹ and R ² is an alkyl group having 1 to 20 carbon atoms, and the other is a fluorinated alkyl group having 1 to 20 carbon atoms. Any of R ³ and R ⁴ One is an alkyl group having 1 to 20 carbon atoms, and the other is a fluorinated alkyl group having 1 to 20 carbon atoms, and may contain an ester group and / or an ether group, X is —C (= O)-, -O-, -OC (= O)-, n is an integer of 0 to 3, and m is 0 or 1.
Claim 2 :
Resist protective film material of claim 1, wherein the polymer compound further contains a repeating unit of alkali solubility.
Claim 3 :
The resist protective film material according to claim 2, wherein the alkali-soluble repeating unit is a repeating unit having a carboxyl group or α-fluoroalcohol.
Claim 4:
Furthermore, the resist protective film material of Claim 1, 2, or 3 containing the solvent which melt | dissolves the said high molecular compound.
Claim 5:
5. A lithography pattern forming method in which a protective film made of a resist upper layer film material is formed on a photoresist layer formed on a wafer, exposed and then developed, and the resist upper layer film material is used as the resist upper layer film material. A pattern forming method comprising using the resist protective film material according to claim 1.
Claim 6:
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, wherein the resist upper layer film material is used as the resist upper layer film material. 5. A pattern forming method using the resist protective film material according to any one of 4 above.
Claim 7:
The pattern forming method according to claim 6, wherein the immersion lithography uses an exposure wavelength in the range of 180 to 250 nm and water is inserted between the projection lens and the wafer.
Claim 8:
8. The pattern forming method according to claim 5, wherein development of the photoresist layer and peeling of the protective film of the resist upper layer film material are simultaneously performed with an alkali developer in the development step performed after exposure.

  In the pattern forming method by the immersion lithography of the present invention, the resist protective film formed on the resist film is water-insoluble and can be dissolved in an alkaline aqueous solution (alkaline developer), and has excellent sliding properties. Since mixing is not performed, satisfactory immersion lithography can be performed, and development of the resist film and removal of the protective film can be simultaneously performed at the same time during alkali development.

  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. These are used as the resist upper layer film material, and are formed by adding a polymer compound having both a fluoroalkyl group and an alkyl group in one repeating unit as a hydrophobic group.

Here, the repeating unit having a fluoroalkyl group and an alkyl group can be represented by the repeating unit a1 or a2 of the following formula (1).

Here, in the formula, any one of R ¹ and R ² is a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, particularly 2 to 16 carbon atoms, and the other is 1 to 20 carbon atoms, in particular. 2 to 16 linear, branched or cyclic fluorinated alkyl groups. One of R ³ and R ^{4 is} a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, particularly 2 to 16 carbon atoms, and the other is a linear chain having 1 to 20 carbon atoms, particularly 2 to 16 carbon atoms. , A branched or cyclic fluorinated alkyl group containing an ester group and / or an ether group in the form of —C (═O) —, —O—, —O—C (═O) —. May be. X is —C (═O) —, —O—, or —O—C (═O) —, n is an integer of 0 to 3, and m is 0 or 1.

Specific examples of the repeating unit a1 are shown below.
Here, an example in which R ¹ is a fluoroalkyl group and R ² is an alkyl group is shown, but this is not necessarily the case, and R ¹ may be an alkyl group and R ² may be a fluoroalkyl group.

The repeating unit a2 can be specifically exemplified below.
Here, an example in which R ³ is a fluoroalkyl group and R ⁴ is an alkyl group is shown, but this is not necessarily the case, and R ³ may be an alkyl group and R ⁴ may be a fluoroalkyl group.

  The resist protective film material of the present invention must contain a repeating unit containing both a fluoroalkyl group and an alkyl group in one molecule. This resist protective film is peeled off after exposure and post-exposure baking (PEB). In this case, it may be peeled off with an organic solvent, but may be peeled off during development due to alkali solubility. For alkali solubility, it is necessary to copolymerize and contain the alkali-soluble repeating unit b in the repeating unit a1 and / or a2.

  Here, it shows about the solubility group for obtaining the alkali solubility copolymerized with a1 and / or a2. Examples of the alkali-soluble group include a phenol group, a sulfo group, a carboxyl group, and an α-fluoroalcohol. Among these, a carboxyl group and an α-fluoroalcohol can be preferably used. Specific examples of the repeating unit having a carboxyl group or an α-fluoroalcohol are shown below.

  In this case, the dissolution rate in water of the polymer compound obtained by copolymerizing the water-repellent repeating units a1 and a2 of formula (1) and the alkali-soluble repeating unit b is 0.1 Å (angstrom) / s or less, 2 A resist protective film having a dissolution rate of a developer composed of an aqueous solution of 38 mass% tetramethylammonium hydroxide and having a dissolution rate of 300 kg / s or more can be formed.

  In the case of an alkali-soluble top coat, the copolymerization ratio of a1, a2 and b varies depending on the adjustment of the alkali dissolution rate. Preferred copolymerization ratios in this case are 0 ≦ a1 ≦ 0.8, 0 ≦ a2 ≦ 0.8, 0.03 ≦ a1 + a2 ≦ 0.8, 0 ≦ b ≦ 0.9, and more preferably 0 ≦ a1 ≦. The ranges are 0.7, 0 ≦ a2 ≦ 0.7, 0.05 ≦ a1 + a2 ≦ 0.6, and 0 ≦ b ≦ 0.8. In this case, when a1 + a2 + b ≦ 1, and when a1 + a2 + b <1, the remaining units are repeating units having only an alkyl group or a fluoroalkyl group in the units a1 and a2 of the formula (1).

  Here, a1 + a2 + b = 1 means that in the polymer compound containing the repeating units a1, a2, and b, the total amount of the repeating units a1, a2, and b is 100 mol% with respect to the total amount of all the repeating units. It shows that.

  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.

The synthesis of these polymer compounds is based on radical polymerization, anionic polymerization, cationic polymerization, and the like, but when performing block polymerization, living polymerization such as living anion polymerization is effective. As a polymerization method, a polymer compound can be obtained by adding an initiator to a monomer having an unsaturated bond for obtaining the repeating units a1, a2, and b in an organic solvent and performing heat polymerization. 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 the polymerization initiator, in radical polymerization, 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2-azobis (2- Methyl propionate), benzoyl peroxide, lauroyl peroxide, and the like. Alkyl lithium is used as anionic polymerization, and among them, sec-butyl lithium and n-butyl lithium are particularly preferably used as an initiator for living anion polymerization. It is done. Examples of cationic polymerization include sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, hypochlorous acid, trichloroacetic acid, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, camphorsulfonic acid, tosylic acid, BF ₃ , AlCl ₃ , TiCl _4, SnCl ₄ other Friedel-Crafts catalyst such _{as, I 2, (C 6 H} 5) 3 substance which easily generates a cation as CCl are used. As polymerization temperature, it can superpose | polymerize, preferably heating at 50-80 degreeC. 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 nonpolar solvents such as higher alcohols having 4 or more carbon atoms, toluene, xylene, anisole, hexane, cyclohexane, heptane, octane, decane, and ether. 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 , Diisopropyl ether, diisobutyl ether, di-n-butyl ether, methylcyclopentyl ether, and methylcyclohexyl ether.

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 layer 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. The exposure method may be dry exposure in which the space between the resist protective film and the projection lens is a gas such as air or nitrogen, but may be immersion exposure in which the space between the resist protective film and the projection lens is filled with liquid. Water is preferably used in the immersion exposure. In immersion exposure, the presence or absence of cleaning of the wafer edge and back surface and the cleaning method are important in order to prevent water from flowing around the wafer back surface and elution from the substrate. For example, the solvent is volatilized by baking the resist protective film in the range of 40 to 130 ° C. for 10 to 300 seconds after spin coating. In the case of resist coating and dry exposure, edge cleaning is performed at the time of spin coating, but in the case of immersion exposure, when a highly hydrophilic substrate surface comes into contact with water, water may remain on the substrate surface of the edge portion, It is not preferable. Therefore, there is a method in which edge cleaning is not performed during spin coating of the resist protective film.

  After forming the resist protective film, exposure is performed in water by KrF or ArF immersion lithography. After exposure, 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 of the present invention is peeled off and the resist film is developed simultaneously. Before PEB, water may remain on the resist protective film. If PEB is performed with water remaining, water passes through the protective film, causing azeotropic dehydration with the acid in the resist, and pattern formation becomes impossible. In order to completely remove water on the protective film before PEB, spin dry before PEB, purge with dry air or nitrogen on the surface of the protective film, or optimization of the water recovery nozzle shape and water recovery process on the stage after exposure For example, it is necessary to dry or recover the water on the protective film. Furthermore, the resist protective film having high water repellency and excellent water slidability shown in the present invention is characterized by excellent water recoverability.

  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 group is preferably used as a base resin. .

  The resist material in ArF exposure must have a structure that does not contain an aromatic 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, or ternary 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 polymerizations selected from metathesis ring-opening polymers It is preferably used.

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.
The structural formulas of monomers 1 to 16 used in the synthesis examples are shown below.

[Synthesis Example 1]
41.5 g of monomer 1, 13.9 g of monomer 3 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 ¹ H-NMR, the molecular weight was confirmed by GPC, and Example polymer 1 was obtained.

[Synthesis Example 2]
41.5 g of monomer 1, 13.1 g of monomer 4 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]
To a 200 mL flask, 41.5 g of monomer 1, 14.0 g of monomer 5 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, and the molecular weight was confirmed by GPC.

[Synthesis Example 4]
To a 200 mL flask, 41.5 g of monomer 1 and 13.1 g of monomer 6 were added, and 40 g of methanol was added as a solvent. 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 5]
In a 200 mL flask, 41.5 g of monomer 1, 9.8 g of monomer 7, 2.7 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, and the molecular weight was confirmed by GPC.

[Synthesis Example 6]
To a 200 mL flask, 32.5 g of monomer 2, 13.1 g of monomer 4, 2.7 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, and the molecular weight was confirmed by GPC.

[Synthesis Example 7]
To a 200 mL flask, 32.5 g of monomer 2, 9.8 g of monomer 7, 5.4 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 ¹ H-NMR, the molecular weight was confirmed by GPC, and Example polymer 7 was obtained.

[Synthesis Example 8]
To a 200 mL flask, 32.5 g of monomer 2, 14.0 g of monomer 3, 2.7 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 ¹ H-NMR, the molecular weight was confirmed by GPC, and Example polymer 8 was obtained.

[Synthesis Example 9]
To a 200 mL flask, 30.0 g of monomer 9, 14 g of monomer 10 and 60 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 Example polymer 9 was obtained.

[Synthesis Example 10]
To a 200 mL flask, 30.0 g of monomer 9, 13.6 g of monomer 11 and 60 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, and the molecular weight was confirmed by GPC.

[Synthesis Example 11]
To a 200 mL flask, 30.0 g of monomer 9, 14.5 g of monomer 12 and 60 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, and the molecular weight was confirmed by GPC.

[Comparative Synthesis Example 1]
In a 200 mL flask, 41.5 g of monomer 1, 10.5 g of monomer 13 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.

[Comparative Synthesis Example 2]
To a 200 mL flask, 41.5 g of monomer 1 and 5.8 g of monomer 14 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 ¹ H-NMR, the molecular weight was confirmed by GPC, and the polymer was Comparative Example 2.

[Comparative Synthesis Example 3]
To a 200 mL flask, 30.0 g of monomer 9, 9.0 g of monomer 15, 5.0 g of monomer 13 and 60 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 3 was obtained.

[Comparative Synthesis Example 4]
To a 200 mL flask, 30.0 g of monomer 9, 4.3 g of monomer 16 and 60 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 a comparative polymer 4 was obtained.

Example polymer 1-11 and comparative example polymer 1-4 use the polymer shown in the above synthesis example, each 0.5 g dissolved in 25 g isobutyl alcohol, each filtered through a 0.2 micron size polypropylene filter, A resist protective film solution was prepared.
A resist protective film solution was applied on a hexamethyldisilazane (HMDS) -treated silicon wafer, and baked at 100 ° C. for 60 seconds to prepare a resist protective film having a thickness of 50 nm.
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 1.

  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 2.

  Using a tilting contact angle meter Drrip Master 500 made by Kyowa Interface Science, 50 μL of pure water was dropped on the wafer that was formed horizontally by the resist protective film (TC1-11, comparative TC1-4) by the above method and kept horizontal. Formed polka dots. Next, the wafer was gradually tilted, and the wafer angle (falling angle) and receding contact angle at which the polka dots began to fall were determined. The results are shown in Table 3.

  A small falling angle indicates that water easily flows, and a receding contact angle indicates that it is difficult for a droplet to remain even in high-speed scanning exposure. In the case of the polymer of a repeating unit having a fluoroalkyl group and an alkyl group in one molecule of the present invention, the falling angle is smaller than a polymer having a repeating unit having a fluoroalkyl group and a repeating unit having an alkyl group alone. There is a feature that the receding contact angle becomes large.

Further, 5 g of the resist polymer shown below, 0.25 g of PAG, and 0.5 g of quencher are dissolved in 55 g of propylene glycol monoethyl ether acetate (PGMEA) solution, filtered through a 0.2 micron size polypropylene filter, and resist solution Was made. A resist solution was applied on an 87 nm film thickness of an anti-reflective film ARC-29A manufactured by Nissan Chemical Industries on a Si substrate, and baked at 120 ° C. for 60 seconds to prepare a resist film having a film thickness of 150 nm. A resist protective film was applied thereon and baked at 120 ° 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 annular 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 no post-exposure pure water rinsing was also performed.
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 a pure water rinse 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.

Claims (8)

A resist protective film material for immersion lithography , comprising using a polymer compound containing a repeating unit having both a fluoroalkyl group and an alkyl group represented by the following repeating unit a1 or a2 .

(In the formula, ^one of R ¹ and R ² is an alkyl group having 1 to 20 carbon atoms, and the other is a fluorinated alkyl group having 1 to 20 carbon atoms. Any of R ³ and R ⁴ One is an alkyl group having 1 to 20 carbon atoms, and the other is a fluorinated alkyl group having 1 to 20 carbon atoms, and may contain an ester group and / or an ether group, X is —C (= O)-, -O-, -OC (= O)-, n is an integer of 0 to 3, and m is 0 or 1. Resist protective film material of claim 1, wherein the polymer compound further contains a repeating unit of alkali solubility. The resist protective film material according to claim 2, wherein the alkali-soluble repeating unit is a repeating unit having a carboxyl group or α-fluoroalcohol.   Furthermore, the resist protective film material of Claim 1, 2, or 3 containing the solvent which melt | dissolves the said high molecular compound.   5. A lithography pattern forming method in which a protective film made of a resist upper layer film material is formed on a photoresist layer formed on a wafer, exposed and then developed, and the resist upper layer film material is used as the resist upper layer film material. A pattern forming method comprising using the resist protective film material according to claim 1.   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, wherein the resist upper layer film material is used as the resist upper layer film material. 5. A pattern forming method using the resist protective film material according to any one of 4 above.   The pattern forming method according to claim 6, wherein the immersion lithography uses an exposure wavelength in the range of 180 to 250 nm and water is inserted between the projection lens and the wafer.   8. The pattern forming method according to claim 5, wherein development of the photoresist layer and peeling of the protective film of the resist upper layer film material are simultaneously performed with an alkali developer in the development step performed after the exposure.