WO2008035640A1 - Composition for formation of resist protection film, and method for formation of resist pattern using the same - Google Patents

Abstract

Disclosed are: a composition for the formation of a resist protection film, which shows less damage to a resist film, can form a good, rectangular resist pattern, and can be used regardless of the structure of a resin used in a resist composition; and a method for forming a resist pattern by using the composition. Specifically, disclosed are: a composition for the formation of a resist protection film, which comprises (a) an alkali-soluble polymer and (b) an organic solvent comprising a mixture of an ether-based solvent and an alcohol-based solvent; and a method for forming a resist pattern by using the composition.

Description

 Specification

 Resist protective film forming composition and resist pattern forming method using the same

 Technical field

 The present invention relates to a resist protective film-forming composition for forming a resist protective film provided on a resist film. More specifically, the present invention relates to an ω alkali-soluble polymer, and (b) an ether solvent and an alcohol system. The present invention relates to a resist protective film forming composition containing an organic solvent composed of a mixed solvent with a solvent, and a resist pattern forming method using the resist protective film forming composition.

 Background art

 [0002] In recent years, a liquid immersion lithography process has been reported as a new lithography technique (see Non-Patent Documents 1 to 3). In this method, during exposure, the resist film is exposed with an immersion medium having a predetermined thickness interposed on at least the resist film in an exposure optical path between an exposure apparatus (lens) and the resist film on the substrate. However, this is a method of forming a resist pattern.

 In the conventional exposure optical path space, an inert gas such as air or nitrogen has been interposed. In this immersion exposure process, the gas in the exposure optical path space is larger than the refractive index of these gases, and a resist film. It is replaced with an immersion medium having a refractive index (n) smaller than the refractive index (for example, pure water or a fluorine-based inert liquid). As a result, the immersion exposure process achieves high resolution even when a light source with the same exposure wavelength is used, as is the case with exposure light with a shorter wavelength or with a high NA lens. At the same time, it has the advantage that the depth of focus does not decrease.

 [0003] By using a resist composition for such an immersion exposure process and a lens mounted on an existing exposure apparatus, the cost is lower, the resolution is better, and the depth of focus is better. A resist pattern can be formed (see Patent Document 1).

In addition, a resist protective film using a fluorine-containing resin that can be dissolved only in a specific solvent is formed on the resist film, and an immersion medium is interposed on the resist protective film, so that the liquid immersion There has been proposed a technique aimed at simultaneously preventing a change in the refractive index due to the alteration of the resist film due to the medium and the alteration of the immersion medium due to the elution component of the resist film force (see Patent Document 2).

 [0004] More recently, from the viewpoints of simplifying the resist pattern formation process and improving manufacturing efficiency, the resist protective film is removed at the time of alkali development after immersion exposure by using an alkali-soluble resist protective film. And a technique for simultaneously forming a resist pattern has been proposed (see Patent Document 3).

 Non-Patent Document 1: “Journal of Vacuum Science & Technology B” (USA), 1999, Vol. 117, No. 6, pages 3306-3309

 Non-Patent Document 2: "Journal of Vacuum Science & Technology B" (USA), 2001, Vol. 119, No. 6, pages 2353-2356

 Non-Patent Document 3: "Proceedings of SPI E", (USA), 2002, 4691, 459-465

 Patent Document 1: International Publication No. 2004/068242 Pamphlet

 Patent Document 2: Pamphlet of International Publication No. 2004/074937

 Patent Document 3: Japanese Patent Laid-Open No. 2005-264131

 Disclosure of the invention

 Problems to be solved by the invention

[0005] Incidentally, the solvent used in the resist protective film forming material disclosed in Patent Document 3 is mainly alcohol. However, when alcohol is used as a solvent, the resist pattern that can damage the resist film becomes T-top shape, or if the surface of the resist pattern is rough, it may swell. Sometimes. In addition, the use of alcohol may be restricted depending on the structure of the polymer (resin) used in the resist composition.

In view of the above problems, the present invention is capable of forming a favorable rectangular resist pattern with little damage to the resist film, and a polymer in the resist composition. The purpose of the present invention is to provide a resist protective film forming composition whose use is not restricted by any structure, and a resist pattern forming method using the resist protective film forming composition. To do.

 Means for solving the problem

 [0007] The present inventors have found that the above-mentioned problems can be solved by using an organic solvent composed of a mixed solvent of an ether solvent and an alcohol solvent as a solvent of the composition for forming a resist protective film. The present invention has been completed. Specifically, it is as follows.

[0008] The present invention relates to a resist protective film-forming composition for forming a resist protective film provided on a resist film, comprising: (a) an alkali-soluble polymer; and (b) an ether solvent and an alcohol solvent. And a composition for forming a resist protective film, which comprises an organic solvent comprising a mixed solvent.

 [0009] The present invention also includes a resist film forming step of forming a resist film on a substrate, and a protective film forming step of forming a resist protective film on the resist film using the resist protective film forming composition described above. Forming a resist pattern comprising: an exposure step of exposing the resist film through the resist protective film; and an image step of developing the resist film after the exposure by removing the resist protective film with a developer. Provide a method.

 The invention's effect

 [0010] According to the present invention, it is possible to reduce damage to the resist film by using an organic solvent composed of a mixed solvent of an ether solvent and an alcohol solvent. In addition, it is possible to provide a composition for forming a resist protective film whose use is not restricted regardless of the structure of the polymer in the resist composition. This makes it possible to form a good rectangular resist pattern.

 Furthermore, according to the present invention, the solubility of the polymer can be improved by using an organic solvent comprising a mixed solvent of an ether solvent and an alcohol solvent. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, embodiments of the present invention will be described in detail.

[Composition for forming resist protective film]

The composition for forming a resist protective film according to the present invention includes an immersion exposure process and a dry exposure process. It can be used for both exposure processes.

 [0013] The composition for forming a resist protective film of the present invention comprises an ω alkali-soluble polymer (hereinafter also referred to as ω component), and (b) an organic solvent (hereinafter referred to as a mixed solvent of an ether solvent and an alcohol solvent). (Also referred to as component (b)). The following explains each component o

 [0014] <(a) Alkali-soluble polymer>

 Specific examples of the alkali-soluble polymer (a) include the following embodiments. First, as a first embodiment of (a) the alkali-soluble polymer, a polymer having at least a monomer unit represented by the following general formula (A-1) as a constituent unit can be used.

 [0015] [Chemical 1]

 (Α-1)

 In the above general formula (A-1), R is an alkylene group having 1 to 6 carbon atoms or a fluoroalkylene group, and each R is independently a hydrogen atom or a straight chain having 1 to 6 carbon atoms. Shape, branch

 2

 Or a cyclic alkyl group or a fluoroalkyl group, Ζ is an alkylene group having 1 to 2 carbon atoms or an oxygen atom, and η is an integer of 0 to 3.

 [0017] In particular, as R, specifically, methylene group, ethylene group, η-propylene group, η butylene group, η-pentylene group or other linear alkylene group, 1 methylethylene group, 1-methylpropylene Groups, branched alkylene groups such as 2-methylpropylene group, and the like. Some or all of the hydrogen atoms of these alkylene groups may be substituted with fluorine atoms. Among these, R is more preferably a methylene group.

[0018] Specific examples of R include, in addition to a hydrogen atom, a methyl group, an ethyl group, and η-propinole. Group, a linear alkyl group such as n-butyl group and n-pentyl group, and a branched alkyl group such as isopropyl group, 1-methylpropyl group and 2-methylpropyl group. Some or all of the hydrogen atoms of these alkyl groups may be substituted with fluorine atoms. Among these, from the viewpoint of improving water repellency, a perfluoroalkyl group in which all of the hydrogen atoms of these alkyl groups are replaced with fluorine atoms is preferable, and a trifluoromethyl group is particularly preferable.

 Further, in the general formula (A-1), Z is preferably a methylene group, and n is preferably 0.

 [0019] Further, the alkali-soluble polymer of the first aspect includes a structural unit represented by the above general formula (A-1), the following general formulas (A-2), (A-3), and (A — A copolymer having at least one selected from among the monomer units represented by 4) as a constituent unit may also be used.

 [0020] [Chemical 2]

 (A-2) (A-3) (A-4)

[0021] In the general formulas (A-2), (A-3), and (A-4), R represents an alkyle having 1 to 6 carbon atoms.

 Three

 R and R are each an alkyl group having 0 to 6 carbon atoms.

 5 7

 Is a xylene group or a fluoroalkylene group, and each of R, R, and R

 4 6 8

 15 linear, branched, or cyclic alkyl groups or fluoroalkyl groups (provided that part of the alkyl group may be via an ether bond, or a hydrogen atom or fluorine atom of the alkyl group or fluoroalkyl group). Is partially substituted with a hydroxyl group! /, And R, Z, and n have the same meanings as in the general formula (A-1).

 2

[0022] The monomer units represented by the general formulas (A-2), (A-3), and (A-4) are represented by the following general formulas (A-5), (A-6), and ( The monomer unit represented by A—7) is preferred.

[0024] In the general formulas (A-5), (A-6), and (A-7), R represents a single bond or a methylene group.

 9

 R is independently a methyl group or a trifluoromethyl group, and R is carbon.

10 11 A linear or branched alkyl group or a fluoroalkyl group having a number of 2 to 10 (however, part of the hydrogen atom or fluorine atom of the alkyl group or fluoroalkyl group may be replaced by a hydroxyl group). R is a linear or branched alkyl having 5 to 10 carbon atoms.

 12

 Or a fluoroalkyl group (provided that a part of the hydrogen atom or fluorine atom of the alkyl group or fluoroalkyl group may be substituted by a hydroxyl group), R Z, and

 2 and n are synonymous with the above general formula (A-1).

[0025] Among them, R is -CH C F or one C (CH) CH C (CF) OH.

 11 2 2 5 3 2 3 2

 R is C F -CF CF (CF) CF CF CF CF (CF) or one CF CF (CF)

12 7 15 2 3 2 2 2 3 2 2 3

CF C (CF) is preferred.

 2 3 3

 [0026] By incorporating a monomer unit having a sulfonamide group represented by the above general formula (A-1) in the side group into an alkali-soluble polymer, the basic requirements required particularly when applied to an immersion exposure process. A protective film having characteristics can be formed.

Here, the basic characteristics required for the protective film are the ability of the immersion medium to have high resistance to the immersion medium and low compatibility with the resist film provided in the lower layer. In addition, the resist film strength can also prevent elution of components into the immersion medium, and can suppress gas permeation of the protective film. Furthermore, the above general formula (A-2), (A By incorporating at least one structural unit selected from the monomer units represented by 3) and (A-4), a protective film with further improved water repellency can be formed.

 [0027] When an alkali-soluble polymer is used as a copolymer, the monomer unit represented by the general formula (A-1), the general formulas (A-2), (A-3), and (A-4) It is preferable that the monomer unit force represented by () is at least one selected from the constituent ratio (molar ratio) of 60: 40-99: 1.

 A large amount of the monomer unit represented by the general formula (A-2) as the monomer unit is preferable because the solubility of the copolymer in the ether solvent is improved.

 Therefore, in particular, a monomer unit represented by the general formula (A-1) and a copolymer essentially including the monomer unit represented by the general formula (A-2) are preferable. A copolymer comprising a monomer unit represented by formula (1) and / or a monomer unit represented by formula (A-4) is more preferred.

 In this case, the composition ratio (molar ratio) of each monomer unit is (A-1) / (A-2) / (A-3) and / or (8-4) = 10 to 90/10 to 80 / I like to be 5-80.

[0028] Next, as the second aspect of the alkali-soluble polymer (a), an alkali-soluble structure composed of an aliphatic cyclic compound having both a fluorine atom or a fluoroalkyl group and an alcoholic hydroxyl group or an oxyalkyl group is used. Polymers having units can be used.

 That is, a fluorine atom or a fluoroalkyl group and an alcoholic hydroxyl group or an alkyloxy group of the structural unit are bonded to an aliphatic cyclic compound, respectively, and the aliphatic ring constitutes the main chain. It is.

[0030] Specific examples of the fluorine atom or the fluoroalkyl group include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, and the like. In particular, a fluorine atom or a trifunoleolomethyl group is preferable. In addition, as the alcoholic hydroxyl group or alkyloxy group, specifically, an alcoholic hydroxyl group, a linear, branched, or cyclic alkyloxyalkylene group or alkyloxy group having 1 to 15 carbon atoms is used. Can be mentioned. [0031] Specific examples of the alkyloxy group having 1 to 15 carbon atoms include a methyloxy group, an ethyloxy group, a propyloxy group, a butoxy group, and the like, and examples of the alkyloxy group having 1 to 15 carbon atoms include Examples thereof include a methyloxymethyl group, an ethyloxymethyl group, a propoxymethyl group, and a butoxymethyl group.

 [0032] Such a configuration unit

 Formed by cyclopolymerization of the product. The gen compound is preferably butadiene, which is excellent in transparency and dry etching resistance, and can easily form a polymer having a 5-membered ring or a 6-membered ring. In particular, 1,1,2,2,3,3-pentafluoro-4-trifluoromethyl-1,4-hydroxy-1,6-hexadiene (CF = CFCF C (CF) (OH) CH CH = CH) Cyclization

 2 2 3 2 2 A polymer formed by polymerization is most preferred in the industry.

 [0033] The structure of the polymer is specifically shown below.

[0034] [Chemical 4

(A- ⁸ )

[0035] In general formula (A-8), each R is independently a hydrogen atom, or a straight, branched, or

 13

 Or a cyclic alkyloxy group having 1 to 15 carbon atoms or an alkyloxyalkyl group. 1 and m represent the molar ratio of the structure in parentheses, and each 10 mol% force is 90 mol%.

 [0036] Next, as a third embodiment of the (a) alkali-soluble polymer, the general formulas (A-9) and (A

-A polymer having a structural unit represented by 10) can be used.

[0037] [Chemical 5]

 (A-9) (A-10)

 [0038] In the above general formulas (A-9) and (A-10), each R is independently linear, branched,

 14

 Or a cyclic alkyl group having 1 to 5 carbon atoms or a fluoroalkyl group.

 15 each independently represents a hydrogen atom, a fluorine atom, a linear, branched, or cyclic alkyl group having 1 to 5 carbon atoms or a fluoroalkyl group, and at least one of R 1 and R 2

 14 15

 The displacement force is a group having a fluorine atom. R is a hydrogen atom or a methyl group, and p is

 16

 It is a repeat unit.

 [0039] More specifically, the structural units represented by the general formulas (A-9) and (A-10) are represented by the following structural formulas (A-11) and (A-12), respectively. The structural unit is preferably used.

 [0040] [Chemical 6]

[0041] The polymer having the structural units represented by (A-9) and (A-10) is: It may be a copolymer and / or a mixed polymer with the structural unit represented by the general formula (A-13). By using such a copolymer and / or mixed polymer, alkali solubility can be further improved.

[0042] [Chemical 7]

 (A-13)

 [0043] In the above general formula (A-13), each R is independently a hydrogen atom or linear or branched.

 17

 Or a cyclic alkyl group having 1 to 5 carbon atoms or a fluoroalkyl group, and p is a repeating unit as in the general formulas (A-9) and (A-10).

 [0044] Next, as the fourth embodiment of (a) the alkali-soluble polymer, a polymer having a structural unit represented by the general formula (Α-14) can be used.

[0045] [Chemical 8]

 In the above general formula (式 -14), C is a methylene group or a fluoromethylene group, and R is

 A 18 Linear, branched or cyclic fluoroalkyl group having 1 to 5 carbon atoms, q is an integer of 0 to 3, and p is the same as in general formulas (A-9) and (A-10) It is a repeating unit.

 In the above general formula (A-14), part or all of the hydrogen atoms bonded to the carbon atoms constituting the ring skeleton may be substituted with fluorine atoms! /.

 As the structural unit represented by the general formula (A-14), specifically, the following structural formula (A

 The structural unit represented by 15) is particularly preferably used.

[0048] [Chemical 9]

 [0049] Next, as the fifth aspect of the (a) alkali-soluble polymer, a polymer having a structural unit represented by the general formula (A-16) can be used.

 [0050] [Chemical 10]

 (A-16)

 [0051] In the above general formula (A-16), R is a hydrogen atom or a methyl group, and R is a carbon atom of 1

 19 20

 5 is an alkylene group, and R 1 is a group in which some or all of the hydrogen atoms are substituted with fluorine atoms.

 twenty one

 P is a general formula (A-9) and (A-

Similar to 0), it is a repeating unit.

As the structural unit represented by the general formula (A-16), specifically, the following structural formula (A

-It is preferable to use those having the structure shown by 17) and (A-18)!

[0053] [Chemical 11]

(Α-17) ίΑ-18) [0054] Next, as the sixth aspect of the (a) alkali-soluble polymer, a polymer having a structural unit represented by the general formula (A-19) can be used.

 [0055] [Chemical 12]

 [0056] In the general formula (A-19), C is a methylene group or a fluoromethylene group, and R is

 A 22 A linear, branched, or cyclic fluoroalkyl group having 1 to 5 carbon atoms in which some or all of the hydrogen atoms are substituted with fluorine atoms, and R is a hydrogen atom or a hydrogen atom.

 twenty three

 A linear, branched, or cyclic carbon number partially or entirely substituted with fluorine atoms;! ~ 5 fluoroalkyl group, q is an integer of 0-3, p is a general formula (A —9) and repeating unit as in (A-10).

 In the above general formula (A-19), part or all of the hydrogen atoms bonded to the carbon atoms constituting the ring skeleton may be substituted with fluorine atoms! /, Or may be! /.

As the structural unit represented by the general formula (A-19), specifically, a structural unit represented by the following formula (A-20) is preferably used.

[0058] [Chemical 13]

 [0059] In the present invention, the above-mentioned (a) alkali-soluble polymer does not impair the effects of the present invention! / If within the range, the copolymerized polymer obtained by copolymerization or mixing with any other monomer unit It may be a polymer or a mixed polymer.

[0060] Such (a) alkali-soluble polymer can be synthesized by a known method. In addition, the polystyrene equivalent weight average molecular weight (Mw) of this polymer by GPC is not limited to force 2000 force, etc. 80000, 3000 force, etc. More preferred.

 [0061] (a) The blending amount of the alkali-soluble polymer is preferably about 0.1% by mass to 20% by mass with respect to the total amount of the resist protective film forming composition. More preferably, the content is 10% by mass.

 [0062] <(b) Organic solvent>

 The organic solvent (b) is not particularly limited as long as it is an organic solvent composed of a mixed solvent of an ether solvent and an alcohol solvent.

 Since mixed solvents of ether solvents and alcohol solvents generally have a smaller SP value (solubility parameter) than alcohol solvents, polymers in resists with polar groups are more difficult than when alcohol solvents are used. As a result, damage to the resist film can be suppressed, and a resist pattern with a good shape can be formed.

 Furthermore, since the ether solvent and alcohol solvent have little influence on the environment, it is preferable that V and the difference do not contain a fluorine atom! /, Or an organic solvent.

[0063] The ether solvent preferably has 2 to 16 carbon atoms, more preferably 6 to 12 carbon atoms. By setting the carbon number within the above range, damage to the resist film can be further reduced, and the coating property and drying property of the resist protective film forming composition can be maintained in a good state.

 Specific examples of such ether solvents include linear chains such as dimethyl ether, jetyl ethereol, methinoleethinoreethenole, dipropinoleenotenole, diisopropinoleethenore, dibutyl ether, diisoamyl ether, and the like. Examples include branched alkyl ethers. Among these, it is preferable to use at least one selected from diisopropyl ether, dibutyl ether, and diisoamyl ether. These can be used alone or in combination of two or more.

 Furthermore, since these ether solvents are non-fluorine solvents, it is possible to provide a composition for forming a resist protective film that has little environmental impact.

The boiling point of the ether solvent is preferably 200 ° C. or less from the viewpoint of coating properties and drying properties of the resist protective film forming composition! [0064] Further, the alcohol solvent preferably has 2 to 10 carbon atoms. By making the number of carbons within the above range, it becomes possible to improve the solubility of (a) the alkali-soluble polymer.

 Examples of such alkyl alcohols include linear, branched, and cyclic alkyl alcohols such as ethanol, propanol, n-butanol, isobutanol, n-pentanol, 4-methyl-2-pentanol, and 2-octanol. Among them, it is preferable to use at least one selected from 4-methyl 2-pentanol and iso-butanol.

 The boiling point of the alcohol solvent is preferably 200 ° C. or less from the viewpoints of coating properties and drying properties of the resist protective film forming composition.

[0065] (b) The content ratio of the ether solvent and the alcohol solvent in the organic solvent is preferably 50:50 force, et al. 99: 1 by mass ratio, 60:40 force, et al. 99: 1 is more preferable, and 80:20 to 95: 5 is most preferable. By setting the content ratio within the above range, (a) it is possible to provide a composition for forming a resist protective film that can dissolve the alkali-soluble polymer satisfactorily and reduce damage to the resist film. Become

Yes

 [0066] <(c) Crosslinking agent>

 The composition for forming a resist protective film according to the present invention may further contain (c) a crosslinking agent, if necessary, in addition to the components (a) and (b). The crosslinking agent includes a nitrogen-containing compound having an amino group substituted with at least one substituent selected from a hydroxyalkyl group and an alkoxyalkyl group, and a hydrogen atom having a hydroxyalkyl group and an alkoxyalkyl group. Use force S to use at least one nitrogen-containing compound selected from among nitrogen-containing compounds having an imino group substituted with at least one substituent selected from the group.

These nitrogen-containing compounds include, for example, melamine derivatives, urea derivatives, guanamine derivatives, acetoguanamine derivatives, benzoguanamine derivatives, which are substituted with a hydrogen atom of a hydroxyl group, a hydroxyl group or an alkoxymethyl group, or both. Succinamide derivatives, glycoluril derivatives in which the hydrogen atom of the imino group is substituted, Examples include a tylene urea-based derivative.

 [0067] These nitrogen-containing compounds are obtained by, for example, reacting the above-mentioned nitrogen-containing compounds with formalin in boiling water to form methylol, or in addition to this, lower alcohols, specifically methanol, ethanol, n- It can be obtained by reacting with propanol, isopropanol, n-butanol, isobutanol and the like to effect alkoxylation. Among them, a preferable cross-linking agent is tetrabutoxymethylated glycoluril.

 [0068] Further, as a cross-linking agent, a condensation reaction product of a hydrocarbon compound substituted with at least one substituent selected from a hydroxyl group and an alkyloxy group and a monohydroxymonocarboxylic acid compound may be preferably used. it can. As the monohydroxymonocarboxylic acid, those in which the hydroxyl group and the carboxyl group are bonded to the same carbon atom or two adjacent carbon atoms are preferred.

 [0069] When such a crosslinking agent is blended, the blending amount is preferably about 0.5 to 10% by mass with respect to the amount of (a) the alkali-soluble polymer.

 [0070] <(d) Acidic compound>

 The resist protective film-forming material according to the present invention may further contain (d) an acidic compound as necessary. By adding this acidic compound, an effect of improving the shape of the resist pattern can be obtained. Furthermore, after immersion exposure, the resist film is exposed to an atmosphere containing a trace amount of amine before development. Even if it is present (reservation after exposure), the presence of the protective film can effectively suppress the adverse effects of the amine. As a result, it is possible to prevent a large deviation in the size of the resist pattern obtained by subsequent development.

 [0071] Examples of such acidic compounds include at least one selected from the following general formulas (D-l), (D-2), (D-3), and (D-4). .

[0072] [Chemical 14] (C _s F _{s + 1} S0 ₂ ) ₂ NH (D-1) C _t F _{t + 1} S0 ₂ COOH (D-2)

 [0073] In the above general formulas (D— ;!) to (D—4), s is an integer from 1 to 5, t is an integer from 10 forces, 15 and u is an integer from 2 to 3. V is an integer from 2 to 3 respectively, and R and R are

 23 24 is an alkyl group having 1 to 15 carbon atoms or a fluoroalkyl group (a part of hydrogen atoms or fluorine atoms may be substituted with a hydroxyl group, an alkoxy group, a carboxyl group, or an amino group).

 [0074] None of these acidic compounds are subject to the Important New Use Regulation (SNUR), and are considered to have no adverse effects on the human body! /.

 [0075] Specific examples of the acidic compound represented by the general formula (D-1) include (C F SO) N

 4 9 2 2

Acidification represented by the above general formula (D-2) preferred by compounds such as H and (C F SO) NH

3 7 2 2

 Specifically, the compound is preferably a compound such as C 2 F 3 COOH.

 10 21

 [0076] Further, the acidic compounds represented by the general formulas (D-3) and (D-4) are specifically represented by the following formulas (D-5) and (D-6), respectively. I like the compound!

 [0077] [Chemical 15]

[0078] When the acidic compound is blended, the blending amount is set to 0.

 It is preferably about 1 to 10% by mass.

 [0079] <(e) Acid generating aid that generates acid in the presence of acid>

If necessary, the resist protective film-forming composition according to the present invention may further contain (e) an acid generation assistant. This (e) acid generation auxiliary agent means an acid generation agent that does not have a function of generating an acid alone, but generates an acid by the presence of an acid. As a result, the acid generation in the resist film Even when acid power S generated from the raw material is diffused into the resist protective film, the acid generated from the acid generation auxiliary agent in the resist protective film compensates for the shortage of acid in the resist film. By doing so, it is possible to suppress the degradation of the resolution of the resist composition and the reduction of the depth of focus, and a finer resist pattern can be formed.

 [0080] Such an acid generation auxiliary agent is preferably an alicyclic hydrocarbon compound having both a carbonyl group and a sulfonyl group in the molecule.

 [0081] Specifically, such an acid generation auxiliary agent is preferably at least one selected from the compounds represented by the following general formulas (E-1) and (E-2).

 [0082] [Chemical 16]

 (E-1) (E-2)

 [0083] In the above general formulas (E-1) and (E-2), R to R are each independently a hydrogen atom,

 25 28

 Or a linear or branched alkyl group having 1 to 10 carbon atoms, and X is an electrophilic group having a sulfonyl group.

 [0084] Here, the "linear or branched alkyl group having 1 to 10 carbon atoms" means a methyl group, an ethynole group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a second group Butyl, tertiary butyl, amyl, isoamyl, tertiary amyl, hexyl, heptyl, octyl, isooctyl, 2-ethylhexyl, tertiary octyl, nonyl, isononyl And straight-chain or branched saturated hydrocarbon groups such as a group, a decyl group, and an isodecyl group.

 [0085] X is "an electrophilic group having a sulfonyl group". Here, the “electrophilic group having a sulfonyl group” is preferably —O—SO—Y. Where Y is 1 carbon number

 2

 5 alkyl groups or halogenated alkyl groups having 1 to 10 carbon atoms. Of these, Y is preferably a fluoroalkyl group.

[0086] Specific examples of the compounds represented by the general formulas (E-1) and (E-2) include the following: Examples thereof include compounds represented by formulas (E-3) to (E-10).

[0087] [Chemical 17]

 (E-7) (E-8) (E-9) (E-10)

[0088] (e) The blending amount of the acid generation auxiliary agent is preferably 0.1 to 50 parts by mass with respect to 100 parts by mass of the (a) alkali-soluble polymer. Is more preferable. By setting it within such a range, it is possible to improve the pattern shape by effectively generating an acid with respect to the resist film force that does not cause uneven coating and the acid eluted.

 [0089] <(f) Others>

 The protective film-forming composition according to the present invention may further contain an optional (f) surfactant, if desired. Examples of this surfactant include “XR-104” (trade name: manufactured by Dainippon Ink & Chemicals, Inc.), but are not limited thereto. By blending such a surfactant, it is possible to further improve the coating properties and the ability to suppress the eluate.

 [0090] When such a surfactant is blended, the blending amount is (a) an alkali-soluble polymer.

 The amount is preferably 0.001 to 10 parts by mass with respect to 100 parts by mass.

[0091] The resist composition is not particularly limited, and any resist composition that can be developed with an aqueous alkali solution, including negative and positive resist compositions, can be used. Such resist compositions include (i) a pod-type resist composition containing a naphthoquinone diazide compound and a nopolac resin, (ii) a compound that generates an acid upon exposure, an alkaline water decomposed by the acid. A positive resist composition containing a compound that increases solubility in a solution and an alkali-soluble resin, (iii) a compound that generates an acid upon exposure, an alkali having a group that decomposes with an acid and increases the solubility in an alkaline aqueous solution Power that includes a positive resist composition containing a soluble resin, and (iv) a negative resist composition containing a compound that generates an acid by light, a cross-linking agent, and an alkali-soluble resin, etc. Absent.

 <Method for forming resist pattern>

 Next, a method for forming a resist protective film using the composition for forming a resist protective film according to the present invention and exposing the resist film through the resist protective film to form a pattern will be described.

 The method for forming a resist pattern according to the present invention includes a resist film forming step for forming a resist film on a substrate, and a protective film for forming a resist protective film on the resist film using a resist protective film forming composition. A film forming step, an exposure step of exposing the resist film through the resist protective film, and a developing step of developing the resist film after exposure by removing the resist protective film with a developer. . This resist pattern can be formed using either a dry exposure process or an immersion exposure process.

 [0094] [Dry exposure process]

 The “resist film forming step” refers to a step of forming a resist film on a substrate. Specifically, a known resist composition is applied to a substrate such as a silicon wafer by using a known method such as a spinner and then pre-beta (PAB treatment) is performed to form a resist film. Note that the resist film may be formed after providing one layer of an organic or inorganic antireflection film (lower antireflection film) on the substrate.

 [0095] The resist composition is not particularly limited, and any resist composition that can be developed with an alkaline aqueous solution can be used, including negative and positive resists. As such a resist composition, the resist composition as described above can be used.

“Protective film forming step” refers to a step of forming a resist protective film. Specifically, the resist protective film forming composition according to the present invention is uniformly applied to the surface of the resist film formed by the above resist film forming process by the same method as in the resist film forming process, beta And a step of forming a resist protective film by curing.

The “exposure step” refers to a step of performing exposure at a predetermined wavelength via a mask pattern from above the resist protective film formed in the protective film forming step. At this time, the exposure light passes through the resist protective film and reaches the resist film.

The wavelength used for exposure in this case is appropriately selected depending on the characteristics of the resist film, which is not particularly limited. For example, ArF excimer laser, KrF excimer laser,

F excimer laser, extreme ultraviolet (EUV), vacuum ultraviolet (VUV), electron beam, X-ray, soft X

2

 It can be performed using radiation such as lines. In the present embodiment, the exposure wavelength is particularly preferably 193 nm.

[0099] The refractive index of the resist protective film with respect to the exposure wavelength is preferably higher than the refractive index of water at the exposure wavelength!

[0100] Further, it is preferable that the exposed resist film and resist protective film are subjected to a heat treatment (PEB).

 [0101] "Developing step" refers to a step of developing a resist film after exposure using an alkaline developer composed of an alkaline aqueous solution. Since this developing solution is alkaline, when the resist protective film is formed on the surface of the resist film, the resist protective film is first dissolved, and then the soluble portion of the resist film is dissolved. In addition, post-beta may be performed after development.

 [0102] [In case of immersion exposure process]

 In the case of the immersion exposure process, the same procedure as in the dry exposure process is performed up to the “protective film formation step”. Then, in the “exposure process”, an immersion medium is disposed on the substrate on which the resist protective film is formed, and in this state, the resist film and the resist protective film on the substrate are selectively exposed through the mask pattern. I do. Accordingly, at this time, the exposure light passes through the immersion medium and the resist protective film and reaches the resist film.

[0103] At this time, since the resist film is shielded from the immersion medium by the resist protective film, the resist film is subjected to alteration such as swelling due to the invasion of the immersion medium. Elution prevents optical properties such as the refractive index of the immersion medium itself from being altered. [0104] The exposure light is not particularly limited as in the dry exposure process, and can be performed using radiation such as ArF excimer laser, KrF excimer laser, VUV (vacuum ultraviolet).

 Here, the immersion medium is not particularly limited as long as it is a liquid having a refractive index larger than that of air and smaller than that of the resist film to be used. Examples of such immersion media include water (pure water, deionized water), fluorine-based inert liquids, etc., but immersion media having high refractive index characteristics that are expected to be developed in the near future can also be used. is there. Specific examples of fluorinated inert liquids include c HC1 F, C F OCH, C F OC H, C

 3 2 5 4 9 3 4 9 2 5 5

Examples thereof include liquids mainly composed of fluorine-based compounds such as HF. Of these, cost,

3 7

 From the viewpoints of integrity, environmental problems, and versatility, it is preferable to use water (pure water, deionized water), but when using exposure light (eg, F excimer laser) with a wavelength of 157 nm.

 2

 From the viewpoint of little exposure light absorption, it is preferable to use a fluorinated solvent.

 [0106] When the exposure process in the immersion state is completed, the substrate is taken out of the immersion medium, and the liquid is removed from the substrate. It is preferable to perform PEB on the resist film with the protective film laminated on the exposed resist film!

 Next, the exposed resist film and resist protective film are heated in the same manner as in the dry exposure process, and developed using an alkali developer. A known developing solution can be appropriately selected and used as the alkaline developer. By this alkali development treatment, the resist protective film is dissolved and removed simultaneously with the soluble portion of the resist film. In addition, post-beta may be performed following the development processing.

 [0108] Subsequently, rinsing is performed using pure water or the like. In this water rinse, for example, while rotating the substrate, water is dropped or sprayed on the surface of the substrate to wash away the developer on the substrate and the resist protective film component and the resist composition dissolved by the developer. Then, drying is performed to obtain a resist pattern in which the resist film is patterned into a shape corresponding to the mask pattern.

Thus, in the present invention, the removal of the resist protective film and the development of the resist film are realized simultaneously by the development process. The resist protective film formed from the resist protective film-forming composition of the present invention has improved water repellency, so that the amount of the immersion medium that can be easily separated after completion of the exposure is as follows. So-called immersion medium leakage with less is less. [0109] By forming a resist pattern in this manner, it is possible to manufacture a resist pattern with a fine line width, particularly a line 'and' space pattern with a small pitch with a good resolution. Note that the pitch in the line-and-space pattern refers to the total distance of the resist pattern width and the space width in the line width direction of the pattern.

 [0110] The resist pattern formed by such a method has a better rectangular shape as compared with the case where a resist pattern is formed using a conventional resist protective film-forming composition using only an alcohol solvent. .

 Example

 [0111] [Examples;! To 3 and Comparative Example 1]

 First, an alkali-soluble polymer represented by the following structural formula (X-1) (mass average molecular weight: 5000) is mixed with a mixed solvent of dibutyl ether and 4-methyl-2-pentanol (mixed mass ratio = 70:30). Dissolved to prepare a resist protective film-forming composition 1 having a solid content concentration of 1.5% by mass. In addition, the same alkali-soluble polymer as in composition 1 for resist protection film formation is dissolved in a mixed solvent of diisopropyl ether and isobutanol (mixing mass ratio = 80:20) to protect the resist with a solid content concentration of 1.5% by mass. A film-forming composition 2 was prepared. Furthermore, the same alkali-soluble polymer as in the resist protective film forming composition 1 is dissolved in a mixed solvent of diisopropyl ether and 4-methyl-2-pentanol (mixing mass ratio = 90: 10) to obtain a solid content concentration of 1.5. A composition 3 for forming a resist protective film of 3% by mass was prepared.

 Further, as a comparative example, the same alkali-soluble polymer as the resist protective film forming composition 1 was dissolved in a dibutyl ether single solvent to prepare a resist protective film forming composition 4 having a solid content concentration of 1.5% by mass.

 [0112] [Chemical 18]

(X-1) [0113] Next, TArF-7a 128 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a resist material containing an acrylic resin, is applied onto a substrate on which ARC29 (manufactured by Brewer) having a thickness of 77 nm is formed. A resist film with a film thickness of 170 nm is formed by heating at 60 ° C for 60 seconds, and the resist protective film forming compositions 1 to 4 are applied to the upper layer, and heated at 90 ° C for 60 seconds. A resist protective film having a thickness of 35 nm was formed.

[0114] These substrates were exposed using an exposure machine NSR-S302A (manufactured by Nikon Corporation), and after the exposure, pure water was dropped for 1 minute in a simulated immersion environment. Next, by heating for 60 seconds after exposure at 100 ° C, followed by 2. 30 seconds development processing using 38 mass _^0/0 of tetramethylammonium Niu arm hydroxide (TMAH) aqueous solution, to perform a rinsing process Thus, each resist pattern was formed.

 As a result of observing the resist pattern with an SEM (scanning electron microscope), the resist pattern was formed in a good rectangular shape when using the resist protective film forming compositions 1 to 3 of Examples; In contrast, when the resist protective film forming composition 4 of Comparative Example 1 was used, the pattern top portion had a T-top shape.

 [0115] [Example 4]

 First, an alkali-soluble polymer represented by the following structural formula (X-2) (mass average molecular weight: 4500) is dissolved in a mixed solvent of diisoamyl ether and 4-methyl-2-pentanol (mixing mass ratio = 80:20). Thus, a resist protective film-forming composition 5 having a solid content concentration of 2.5 mass% was prepared.

[0116] [Chemical 19]

 (X-2)

[0117] Next, on the substrate on which ARC29 (manufactured by Brewer) having a film thickness of 77 nm was formed, acrylic Resin-containing resist material TArF-7a 128 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied and heated at 110 ° C for 60 seconds to form a resist film with a thickness of 170 nm. The resist protective film-forming composition 5 was applied and heated at 90 ° C. for 60 seconds to form a resist protective film having a thickness of 35 nm.

 [0118] This substrate was subjected to immersion exposure using an exposure machine NSR-S609B (Nikon Corp.), followed by post-exposure heating at 100 ° C for 60 seconds, followed by 2.38% by mass. A resist pattern was formed by developing for 30 seconds using an aqueous solution of tetramethylammonium hydroxide (TMAH) and rinsing.

 As a result of observing the resist pattern with a scanning electron microscope (SEM), the shape of the resist pattern was a good rectangular shape.

 [Example 5]

 First, an alkali-soluble polymer represented by the following structural formula (X-3) (mass average molecular weight: 4500) is mixed with a mixed solvent of diisoamyl ether and 4-methyl-2-pentanol (mixing mass ratio = 80:20). After dissolution, a resist protective film-forming composition 6 having a solid content concentration of 2.5 mass% was prepared.

[0120] [Chemical 20]

 (X-3)

Next, TARF-7a 128 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a resist material containing acrylic yarn resin, is applied onto a substrate on which ARC29 (manufactured by Brewer) having a film thickness of 77 nm is formed. Then, a resist film with a thickness of 170 nm is formed, and a resist protective film-forming composition 6 is applied on the upper layer and heated at 90 ° C. for 60 seconds to form a resist film with a thickness of 35 nm. A strike protective film was formed.

 This substrate was subjected to immersion exposure using an exposure machine NSR-S609B (Nikon Corp.), followed by post-exposure heating at 100 ° C for 60 seconds, followed by 2.38 mass% tetramethyl. The resist pattern was formed by developing for 30 seconds using an aqueous solution of ammonium hydroxide (TMAH) and rinsing.

 As a result of observing the resist pattern with a scanning electron microscope (SEM), the shape of the resist pattern was a good rectangular shape.

Claims

The scope of the claims  [1] A resist protective film forming composition for forming a resist protective film provided on a resist film,  A resist protective film-forming composition comprising (a) an alkali-soluble polymer, and (b) an organic solvent comprising a mixed solvent of an ether solvent and an alcohol solvent. [2] The resist protective film-forming film according to claim 1, wherein the content ratio of the ether solvent and the alcohol solvent in the organic solvent (b) is 50:50 to 99: 1 by mass ratio. Composition.  [3] The composition for forming a resist protective film according to [1] or [2], wherein each of the ether solvent and the alcohol solvent is an organic solvent containing no fluorine atom. [4] The resist protective film forming composition according to any one of claims 1 to 3, wherein the ether solvent is an ether solvent having 2 to 16 carbon atoms. [5] The composition for forming a resist protective film according to any one of claims 1 to 4, wherein the ether solvent is at least one selected from the group consisting of diisopropyl ether, dibutyl ether, and diisoamyl ether. object. [6] The composition for forming a resist protective film according to any one of [1] to [5], wherein the alcohol solvent is an alcohol solvent having 2 to 10 carbon atoms. [7] The composition for forming a resist protective film according to any one of [1] to [6], wherein the alcohol-based solvent power is at least one selected from 4 methyl (2 pentanol) and isobutanol. .  [8] The resist protective film-forming composition for forming a resist protective film provided on the resist film in the immersion exposure process! A resist protective film forming composition. [9] a resist film forming step of forming a resist film on the substrate;  A protective film forming step of forming a resist protective film on the resist film using the composition for forming a resist protective film according to any one of claims 1 to 8,  An exposure step of exposing the resist film through the resist protective film; The resist protective film is removed with a developer to develop the exposed resist film And a developing step.  10. The method for forming a resist pattern according to claim 9, wherein the exposure step is a step of disposing an immersion medium on the resist protective film and selectively exposing the resist film through the immersion medium. .