Radiation-sensitive resin composition and method for forming a resist pattern

Abstract

The present invention provides: a radiation-sensitive resin composition which is capable of exhibiting sensitivity, LWR performance and pattern rectangularity at excellent levels; and a method for forming a resist pattern. A radiation-sensitive resin composition which comprises: a resin that contains a structural unit (A) represented by formula (1) and a structural unit (B) having an acid dissociable group; a radiation-sensitive acid generator; and a solvent. (In formula (1), R1 represents a halogen atom-substituted or unsubstituted monovalent hydrocarbon group having from 1 to 20 carbon atoms;　X represents -O- or -S-;　La1 represents a halogen atom-substituted or unsubstituted divalent hydrocarbon group having from 1 to 10 carbon atoms; and　RP represents a monovalent organic group which has at least one structure selected from the group consisting of a lactone structure, a cyclic carbonate structure and a sultone structure.)

Description

Technical Field

[0001] The present invention relates to a radiation-sensitive resin composition and a method for forming a resist pattern.

Background Art

[0002] Photolithography technology using a resist composition is utilized for forming fine circuits in semiconductor elements. As a typical procedure, for example, acid is generated by exposure of a resist composition film through a mask pattern to radiation, and a difference in solubility of the resin in an alkaline or organic developer between the exposed portion and the unexposed portion is caused by a reaction using the acid as a catalyst, thereby forming a resist pattern on a substrate.

[0003] In the above photolithography technology, radiation with a short wavelength such as an ArF excimer laser is used, or a liquid immersion exposure method (liquid immersion lithography) in which the space between the lens of an exposure apparatus and the resist film is filled with a liquid medium and exposure is performed is used to promote pattern miniaturization. As a next-generation technology, lithography using radiation with an even shorter wavelength such as an electron beam, X-ray, and EUV (extreme ultraviolet ray) is also being studied.

[0004] With the progress of exposure technology, a technology for achieving pattern resolution from the micron unit to the submicron unit using a resist composition containing a resin having an alicyclic group is being developed (Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, as the miniaturization of resist patterns has advanced, in addition to line width roughness (LWR) performance indicating sensitivity and variations in the line width of resist patterns, the rectangularity of the resist pattern shape has been required, and further improvement in various resist performances has been demanded. Furthermore, in next-generation exposure technologies such as electron beam exposure, resist performances equivalent to or better than those of exposure technologies using ArF excimer lasers are required.

[0007] An object of the present invention is to provide a radiation-sensitive resin composition capable of exhibiting excellent sensitivity, LWR performance, and pattern rectangularity, and a method for forming a resist pattern.

Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, the inventors of the present application have found that the above object can be achieved by adopting the following configuration, and have completed the present invention.

[0009] In one embodiment, the present invention relates to a radiation-sensitive resin composition comprising a resin containing a structural unit (A) represented by the following formula (1) and a structural unit (B) having an acid dissociable group, a radiation-sensitive acid generator, and a solvent .

Chemical Formula

[0010] Since the radiation-sensitive resin composition contains a resin having the structural unit (A) represented by the above formula (1) as one structural unit, not only exposure with an ArF excimer laser or the like but also exposure with EUV (extreme ultraviolet light) or the like can exhibit sufficient levels of sensitivity, LWR performance, and resist pattern rectangularity in the resist film using the composition. Although not bound by any theory, the reason is presumed as follows. R in the above formula (1) P At least one structure selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure possessed by (hereinafter also referred to as "lactone structure, etc.") is ring-opened by the action of an alkali in the exposed portion to generate a polar structure, and the solubility in the developer is improved. On the other hand, in the unexposed portion, the lactone structure, etc. maintains hydrophobicity without ring-opening, and due to the hydrophobicity of the hydrocarbon group represented by R 1 , the entire structural unit (A) can exhibit hydrophobicity and suppress dissolution in the developer. Thus, it is presumed that the synergistic effect of the action of improving the solubility of the resin in the developer in the exposed portion and the action of suppressing the dissolution of the resin in the developer in the unexposed portion improves the dissolution contrast between the two, thereby resulting in good rectangularity of the pattern. An organic group means a group containing at least one carbon atom.

[0011] In another embodiment of the present invention, a step of forming a resist film with the above radiation-sensitive resin composition, a step of exposing the above resist film, and a step of developing the above exposed resist film relate to a method for forming a resist pattern including these steps.

[0012] According to the forming method, since the above radiation-sensitive resin composition excellent in various resist performances is used, a high-quality resist pattern can be efficiently formed.

Embodiments for Carrying Out the Invention

[0013] <Radiation-Sensitive Resin Composition> The radiation-sensitive resin composition according to this embodiment (hereinafter, also simply referred to as "composition") contains a resin, a radiation-sensitive acid generator, and a solvent. The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0014] [Resin] (Structural unit (A)) The resin is an aggregate of polymers containing a structural unit (A) represented by the following formula (1) and a structural unit (B) having an acid-dissociable group (hereinafter, this resin is also referred to as "base resin"). [Chemical formula]

[0015] In the above formula (1), R 1 is a monovalent hydrocarbon group having 1 to 20 carbon atoms, which may be substituted or unsubstituted by a halogen atom. X is -O- or -S-. L a1 is a divalent hydrocarbon group having 1 to 10 carbon atoms, which may be substituted or unsubstituted by a halogen atom. R P is a monovalent organic group having at least one structure selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure.)

[0016] Due to the resin containing the structural unit (A), the radiation-sensitive resin composition is excellent in sensitivity, LWR performance, and pattern rectangularity.

[0017] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above R 1 include, for example, a linear hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, or a combination thereof.

[0018] Examples of the linear hydrocarbon group having 1 to 20 carbon atoms represented by the above R 1 include a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, or a linear or branched unsaturated hydrocarbon group having 1 to 20 carbon atoms.

[0019] The above R 1 Examples of the alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by 1 include monocyclic or polycyclic saturated hydrocarbon groups, or monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred monocyclic saturated hydrocarbon groups include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Preferred polycyclic cycloalkyl groups include bridged alicyclic hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms among the carbon atoms constituting the alicyclic ring are bonded by a bonding chain containing one or more carbon atoms.

[0020] The above R 1 Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by 1 include, for example, aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group; aralkyl groups such as a benzyl group, a phenethyl group, and a naphthylmethyl group, and the like.

[0021] The above R 1 Some or all of the hydrogen atoms of these monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by 1 may be substituted with halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Of course, they may not be substituted with any halogen atoms at all.

[0022] The above R 1 The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by 1 preferably does not contain heteroatoms such as an oxygen atom and a sulfur atom (excluding the above halogen atoms). Thereby, by suppressing the generation of polarization and polarity in R 1 it is possible to maintain the hydrophobicity in the unexposed portion of the structural unit (A), and it is possible to exhibit excellent pattern rectangularity.

[0023] The above L a1 Examples of the divalent hydrocarbon group having 1 to 10 carbon atoms represented by a1 include the above R 1Among the monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by , a group in which one hydrogen atom is further removed from a group having 1 to 10 carbon atoms is preferably exemplified.

[0024] Among them, from the viewpoints of the balance between the hydrophobicity of the structural unit (A) in the exposed portion and the hydrophilicity due to the generation of a polar structure, and the copolymerizability of the monomer giving the structural unit (A) and other monomers, etc., L a1 is preferably a divalent chain hydrocarbon group, and particularly preferably a methylene group.

[0025] The above R P The organic group represented by is not particularly limited as long as it has at least one structure selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. The organic group may be any of a chain structure, a cyclic structure, or a combination thereof. Examples of the chain structure include a chain hydrocarbon group that may be saturated or unsaturated, linear or branched. Examples of the cyclic structure include an alicyclic, aromatic, or heterocyclic hydrocarbon group. Further, a group in which some or all of the hydrogen atoms of a group having a chain structure or a group having a cyclic structure are substituted with a substituent, a group in which CO, CS, O, S, SO2, or NR', or a combination of two or more of these is included between the carbon-carbon bonds of these groups, etc. are also exemplified.

[0026] Examples of the substituent that substitutes some or all of the hydrogen atoms of the above organic group include halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; hydroxy group; carboxy group; cyano group; nitro group; alkyl group, alkoxy group, alkoxycarbonyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, or a group in which the hydrogen atom of these groups is substituted with a halogen atom; oxo group (=O), etc.

[0027] R in the above formula (1) P is preferably represented by the following formula (A).

Chemical formula

[0028] In the above formula (A), L a2 is a single bond or a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms. Y is a single bond or a divalent linking group selected from -O-, -CO-, -NH-, -SO2- or a combination thereof. L a3 is a single bond or a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms. R P1 is a substituted or unsubstituted lactone structure, cyclic carbonate structure or sultone structure. * is a bond with -O- in the above formula (1).

[0029] The above L a2 and L a3 Examples of the divalent hydrocarbon group having 1 to 10 carbon atoms represented by are the same groups as the divalent hydrocarbon group having 1 to 10 carbon atoms represented by the above L a1 Examples of the substituent that can substitute part or all of the hydrogen atoms contained in this hydrocarbon group include the above substituents. Examples of groups containing CO, CS, O, S, SO2 or NR', or a combination of two or more of these between carbon-carbon of these groups are also included.

[0030] The above R P1 Examples of the lactone structure, cyclic carbonate structure and sultone structure represented by include the structures represented by the following formulas (A-1) to (A-15). [Chemical formula]

[0031] In the above formula, R L2 ~R L4 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group. When a plurality of R L2 ~R L4 are present respectively, a plurality of RL2 ~R L4 may be the same as or different from each other. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3. * is the bond with -L a3 - in the above formula (A).

[0032] Specific examples of the structural unit (A) include structural units represented by the following formulas (1-1) to (1-20) and the like.

Chemical formula

[0033]

Chemical formula

[0034] The base resin may contain one or a combination of two or more of the structural units (A).

[0035] As the lower limit of the content ratio of the structural unit (A) (the total content ratio when a plurality of types of the structural unit (A) are included), 5 mol% is preferable, 6 mol% is more preferable, 8 mol% is further preferable, and 10 mol% is particularly preferable with respect to all the structural units constituting the base resin. As the upper limit of the above content ratio, 80 mol% is preferable, 70 mol% is more preferable, 65 mol% is further preferable, and 60 mol% is particularly preferable. By setting the content ratio of the structural unit (A) within the above range, the sensitivity, LWR performance, and pattern rectangularity of the resist film obtained from the radiation-sensitive resin composition can be further improved.

[0036] (Synthesis method of the monomer that gives the structural unit (A)) The monomer that gives the structural unit (A) can be synthesized, for example, according to the following scheme. Taking the case where X is an oxygen atom in the above formula (1) as an example, the following description will be given.

Chemical formula

[0037] A halogenated raw material with a protected ester moiety and the R in the above formula (1) 1 is reacted with an alcohol having a structure corresponding to that of R in the above formula (1) to produce an ether derivative, followed by deprotection by alkali hydrolysis, and finally reacted with an alcohol having a structure corresponding to that of R in the above formula (1), whereby a monomer giving a structural unit (A) represented by formula (1') can be synthesized. For other structures, starting materials' linking groups, alcohols having the structure of R P and alcohols having the structure of R 1 can be synthesized by appropriately changing them, etc. P P

[0038] The base resin preferably has, in addition to the structural unit (A), a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (B)") and at least one structural unit (C) selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure described later (however, excluding the structural unit corresponding to the structural unit (A)). It may have other structural units other than the structural units (B) and (C). The "acid-dissociable group" is a group that replaces the hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, etc., and dissociates by the action of an acid. The radiation-sensitive resin composition is excellent in pattern formability because the resin has the structural unit (B). Hereinafter, each structural unit will be described.

[0039] (Structural unit (B)) The structural unit (B) is a structural unit having an acid-dissociable group. The structural unit (B) is not particularly limited as long as it contains an acid-dissociable group. For example, a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, a structural unit having an acetal bond, etc. can be mentioned. From the viewpoint of improving the pattern formability of the radiation-sensitive resin composition, the structural unit represented by the following formula (2) (hereinafter also referred to as "structural unit (B-1)") is preferable.

[0040]

Chem.

[0041] In the above formula (2), R 7 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R 8 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R 9 and R 10 each independently represent a monovalent linear hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are attached.

[0042] As the above R 7 from the viewpoint of the copolymerizability of the monomer giving the structural unit (I-1), a hydrogen atom and a methyl group are preferable, and a methyl group is more preferable.

[0043] As the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above R 8 for example, a linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, etc. can be mentioned.

[0044] As the linear hydrocarbon group having 1 to 10 carbon atoms represented by the above R 8 ~R 10 a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or a linear or branched unsaturated hydrocarbon group having 1 to 10 carbon atoms can be mentioned.

[0045] As the above R 8 ~R 10Examples of the alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by [the formula] include monocyclic or polycyclic saturated hydrocarbon groups, or monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred examples of the monocyclic saturated hydrocarbon group include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Preferred examples of the polycyclic cycloalkyl group include bridged alicyclic hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group. The bridged alicyclic hydrocarbon group means a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms among the carbon atoms constituting the alicyclic ring are bonded by a bonding chain containing one or more carbon atoms.

[0046] The above R 8 Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by [the formula] include, for example, aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group; aralkyl groups such as a benzyl group, a phenethyl group, and a naphthylmethyl group, and the like.

[0047] The above R 8 is preferably a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0048] The above R 9 and R 10 The divalent alicyclic group having 3 to 20 carbon atoms formed by combining the chain hydrocarbon group or alicyclic hydrocarbon group represented by [the formula] together with the carbon atom to which they are bonded is not particularly limited as long as it is a group obtained by removing two hydrogen atoms from the same carbon atom constituting the carbon ring of the monocyclic or polycyclic alicyclic hydrocarbon having the above number of carbon atoms. Either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group may be used. As the polycyclic hydrocarbon group, either a bridged alicyclic hydrocarbon group or a condensed alicyclic hydrocarbon group may be used, and either a saturated hydrocarbon group or an unsaturated hydrocarbon group may be used. The condensed alicyclic hydrocarbon group means a polycyclic alicyclic hydrocarbon group in which a plurality of alicyclic rings are formed in such a way that they share a side (a bond between two adjacent carbon atoms).

[0049] Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include a cyclopentanediy group, a cyclohexanediy group, a cycloheptanediy group, a cyclooctanediy group, etc., and preferred unsaturated hydrocarbon groups include a cyclopentenediy group, a cyclohexenediy group, a cycloheptenediy group, a cyclooctenediy group, a cyclodecenediy group, etc. As the polycyclic alicyclic hydrocarbon group, a bridged alicyclic saturated hydrocarbon group is preferred. For example, a bicyclo[2.2.1]heptane-2,2-diy group (norbornane-2,2-diy group), a bicyclo[2.2.2]octane-2,2-diy group, a tricyclo[3.3.1.1 3,7 decane-2,2-diy group (adamantane-2,2-diy group), etc. are preferred.

[0050] Among these, R 8 is an alkyl group having 1 to 4 carbon atoms, and it is preferable that R 9 and R 10 are combined with each other and the alicyclic structure formed together with the carbon atom to which they are attached is a polycyclic or monocyclic cycloalkane structure.

[0051] Examples of the structural unit (B-1) include structural units represented by the following formulas (3-1) to (3-6) (hereinafter, also referred to as "structural units (B-1-1) to (B-1-6)").

[0052]

Chemical formula

[0053] In the above formulas (3-1) to (3-6), R 7 to R 10 have the same meanings as in the above formula (2). i and j are each independently an integer of 1 to 4. k and l are 0 or 1.

[0054] As i and j, 1 is preferable. As R 8 , a methyl group, an ethyl group or an isopropyl group is preferable. As R 9 and R 10 , a methyl group or an ethyl group is preferable.

[0055] The base resin may contain one or more combinations of structural units (B).

[0056] As the lower limit of the content ratio of the structural unit (B) (when a plurality of types of structural units (B) are included, the total content ratio), 10 mol% is preferable, 20 mol% is more preferable, and 25 mol% is even more preferable with respect to all the structural units constituting the base resin. As the upper limit of the above content ratio, 90 mol% is preferable, 80 mol% is more preferable, 75 mol% is even more preferable, and 70 mol% is particularly preferable. By setting the content ratio of the structural unit (B) within the above range, the pattern formability of the radiation-sensitive resin composition can be further improved.

[0057] (Structural unit (C)) The structural unit (C) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure (however, the structural unit corresponding to the structural unit (A) is excluded). By further having the structural unit (C) in the base resin, the solubility in the developer can be adjusted. As a result, the radiation-sensitive resin composition can improve lithography performance such as resolution. In addition, the adhesion between the resist pattern formed from the base resin and the substrate can be improved.

[0058] Examples of the structural unit (C) include structural units represented by the following formulas (T-1) to (T-10).

[0059] [Chemical formula]

[0060] In the above formula, R L1 is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R L2 ~R L5is, independently of each other, a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group. R L4 and R L5 may, together with the carbon atom to which they are attached, form a divalent alicyclic group having 3 to 8 carbon atoms. L 2 is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3.

[0061] The above R L4 and R L5 Examples of the divalent alicyclic group having 3 to 8 carbon atoms formed by combining R 9 and R 10 together with the carbon atom to which they are attached include groups having 3 to 8 carbon atoms among the divalent alicyclic groups having 3 to 20 carbon atoms formed by combining the chain hydrocarbon group or alicyclic hydrocarbon group represented by R

[0062] and R 2 together with the carbon atom to which they are attached in the above formula (2). One or more hydrogen atoms on this alicyclic group may be substituted with a hydroxy group.

[0063] Among these, as the structural unit (C), a structural unit containing a lactone structure is preferable, a structural unit containing a norbornane lactone structure is more preferable, and a structural unit derived from norbornane lactone-yl (meth)acrylate is even more preferable.

[0064] As the lower limit of the content ratio of the structural unit (C), 2 mol% is preferable, 4 mol% is more preferable, and 5 mol% is even more preferable with respect to all the structural units constituting the base resin. As the upper limit of the above content ratio, 50 mol% is preferable, 45 mol% is more preferable, and 40 mol% is even more preferable. By setting the content ratio of the structural unit (C) within the above range, the radiation-sensitive resin composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0065] (Structural unit (D)) In addition to the above structural units (B) and (C), the base resin may have other structural units. Examples of the other structural units include a structural unit (D) containing a polar group (however, those corresponding to the structural unit (C) are excluded). By further having a structural unit containing a polar group, the base resin can adjust the solubility in the developer, and as a result, the lithography performance such as the resolution of the radiation-sensitive resin composition can be improved. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, a sulfonamide group, etc. Among these, a hydroxy group and a carboxy group are preferable, and a hydroxy group is more preferable.

[0066] Examples of the structural unit (D) having this polar group include a structural unit represented by the following formula.

[0067] [Chemical formula]

[0068] In the above formula, R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0069] When the base resin has a structural unit having the polar group, the lower limit of the content ratio of the structural unit (D) having the polar group is preferably 2 mol%, more preferably 5 mol%, and still more preferably 8 mol% with respect to all the structural units constituting the base resin. The upper limit of the content ratio is preferably 40 mol%, more preferably 30 mol%, and still more preferably 20 mol%. By setting the content ratio of the structural unit (D) having the polar group within the above range, the lithography performance such as the resolution of the radiation-sensitive resin composition can be further improved.

[0070] (Structural unit (E)) As other structural units, the base resin may have a structural unit containing a phenolic hydroxyl group (hereinafter also referred to as "structural unit (E)") in addition to the structural unit (D) having the polar group. The structural unit (E) contributes to the improvement of the etching resistance and the improvement of the difference in developer solubility (dissolution contrast) between the exposed portion and the unexposed portion. In particular, it can be suitably applied to pattern formation using exposure with radiation having a wavelength of 50 nm or less such as an electron beam or EUV. In this case, the resin preferably has the structural unit (B) together with the structural unit (E).

[0071] Examples of the structural unit (E) include a structural unit represented by the following formula (af).

[0072] [Chemical formula]

[0073] In the above formula (af), R AF1 is a hydrogen atom or a methyl group. L AF is a single bond, -COO-, -O- or -CONH-. R AF2 is a monovalent organic group having 1 to 20 carbon atoms or a halogen atom. n f1 is an integer of 0 to 3. n f1 When n is 2 or 3, the plurality of R AF2 may be the same or different. n f2 is an integer of 1 to 3. However, n f1+n f2 is 5 or less. n af is an integer from 0 to 2.

[0074] The above R AF1 is preferably a hydrogen atom from the viewpoint of the copolymerizability of the monomer that provides the structural unit (E).

[0075] L AF is preferably a single bond and -COO-.

[0076] The organic group in the base resin refers to a group containing at least one carbon atom.

[0077] The above R AF2 Examples of the monovalent organic group having 1 to 20 carbon atoms represented by the above R include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group containing a divalent heteroatom-containing group at the carbon-carbon bond or the terminal on the bond side of this hydrocarbon group, a group in which a part or all of the hydrogen atoms of the group and the above hydrocarbon group are substituted with a monovalent heteroatom-containing group, and the like.

[0078] The above R AF2 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above R include an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group; an alkenyl group such as an ethenyl group, a propenyl group, a butenyl group; a chain hydrocarbon group such as an ethynyl group, a propynyl group, a butynyl group; a cycloalkyl group such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a norbornyl group, an adamantyl group; an alicyclic hydrocarbon group such as a cyclopropenyl group, a cyclopentenyl group, a cyclohexenyl group, a norbornenyl group; an aryl group such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, an anthryl group; an aromatic hydrocarbon group such as a benzyl group, a phenethyl group, a naphthylmethyl group, etc.

[0079] The above R AF2 is preferably a chain hydrocarbon group or a cycloalkyl group, more preferably an alkyl group or a cycloalkyl group, and even more preferably a methyl group, an ethyl group, a propyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group or an adamantyl group.

[0080] Examples of the above divalent heteroatom-containing group include -O-, -CO-, -CO-O-, -S-, -CS-, -SO2-, -NR'- and groups formed by combining two or more of these. Preferred examples of the divalent heteroatom-containing group include a methoxy group, an ethoxy group, a propoxy group and the like. R' is a hydrogen atom or a monovalent hydrocarbon group.

[0081] Examples of the above monovalent heteroatom-containing group include halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, a hydroxy group, a carboxy group, a cyano group, an amino group, a sulfanyl group (-SH) and the like.

[0082] The above halogen atom is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

[0083] The above n f1 is preferably an integer of 0 to 2, more preferably 0 and 1, and even more preferably 0.

[0084] The above n f2 is preferably 1 and 2, more preferably 1.

[0085] The above n af is preferably 0 and 1, more preferably 0.

[0086] The above structural unit (E) is preferably a structural unit represented by the following formulas (a1-1) to (a1-9) and the like.

[0087]

Chemical formula

[0088] In the above formulas (a1-1) to (a1-9), R AF1 is the same as in the above formula (af).

[0089] Among these, the structural units represented by each of the above formulas (a1-1) to (a1-7) are preferable, and the structural unit represented by the above formula (a1-1) is more preferable.

[0090] When the base resin contains the structural unit (E), the lower limit of the content ratio of the structural unit (E) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol% with respect to all the structural units constituting the base resin. The upper limit of the above content ratio is preferably 50 mol%, more preferably 40 mol%, and even more preferably 30 mol%. By setting the content ratio of the structural unit (E) within the above range, the sensitivity, LWR performance, and pattern rectangularity of the resist film obtained from the radiation-sensitive resin composition can be further improved.

[0091] However, even if one attempts to polymerize hydroxystyrene, the polymerization will be inhibited by the influence of the phenolic hydroxyl group. Therefore, it is preferable to polymerize in a state where the phenolic hydroxyl group is protected by a protecting group such as an alkali-dissociable group, and then perform hydrolysis for deprotection to obtain the structural unit (E). The structural unit that gives the structural unit (E) by hydrolysis is preferably represented by the following formula (af-1).

[0092] [Chemical formula]

[0093] In the above formula (af-1), R AF1 , L AF , R AF2 , n f1 , n f2 and n af are synonymous with the above formula (af). R 12 is a monovalent hydrocarbon group or alkoxy group having 1 to 20 carbon atoms. R 12Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms for R in structural unit (B) 8 include a monovalent hydrocarbon group having 1 to 20 carbon atoms. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a tert-butoxy group.

[0094] For the above R 12 an alkyl group and an alkoxy group are preferable, and among them, a methyl group and a tert-butoxy group are more preferable.

[0095] The fluorine content in the base resin is preferably 10% by mass or less. The upper limit of the fluorine content is more preferably 9% by mass, further preferably 8% by mass, and particularly preferably 7% by mass. The lower limit of the fluorine content is preferably 0% by mass (that is, does not contain fluorine atoms). By setting the fluorine content in the base resin within the above range, the dissolution contrast between the exposed part and the unexposed part can be improved, and desired resist performances can be exhibited.

[0096] (Synthesis method of base resin) The base resin can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0097] Examples of the radical polymerization initiator include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; peroxide-based radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferable, and AIBN is more preferable. These radical initiators can be used alone or in combination of two or more.

[0098] Examples of the solvent used in the polymerization include Alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; Cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; Halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylenedibromide, and chlorobenzene; Saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; Ketones such as acetone, methyl ethyl ketone, 4-methyl-2-pentanone, and 2-heptanone; Ethers such as tetrahydrofuran, dimethoxyethanes, and diethoxyethanes; Alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol, etc. The solvents used for these polymerizations may be used alone or in combination of two or more.

[0099] The reaction temperature in the above polymerization is usually 40°C to 150°C, preferably 50°C to 120°C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0100] The molecular weight of the base resin is not particularly limited, but the polystyrene-equivalent weight average molecular weight (Mw) by gel permeation chromatography (GPC) is preferably 1,000 or more and 50,000 or less, more preferably 2,000 or more and 30,000 or less, even more preferably 3,000 or more and 15,000 or less, and particularly preferably 4,000 or more and 12,000 or less. If the Mw of the base resin is less than the above lower limit, the heat resistance of the resulting resist film may decrease. If the Mw of the base resin exceeds the above upper limit, the developability of the resist film may decrease.

[0101] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base resin by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0102] Mw and Mn of the resin in this specification are values measured using gel permeation chromatography (GPC) under the following conditions.

[0103] GPC column: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh Corporation) Column temperature: 40 °C Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection volume: 100 μL Detector: Differential refractometer Standard substance: Monodisperse polystyrene

[0104] As the content of the base resin, 70 mass% or more is preferable, 80 mass% or more is more preferable, and 85 mass% or more is even more preferable with respect to the total solid content of the radiation-sensitive resin composition.

[0105] [Other resin] The radiation-sensitive resin composition of this embodiment may contain, as another resin, a resin having a higher mass content ratio of fluorine atoms than the above base resin (hereinafter, also referred to as "high fluorine content resin"). When the radiation-sensitive resin composition contains a high fluorine content resin, it can be unevenly distributed on the surface layer of the resist film with respect to the above base resin, and as a result, the water repellency of the surface of the resist film during immersion exposure can be enhanced.

[0106] As the high fluorine content resin, for example, it preferably has at least one of the structural unit (B) and the structural unit (C) in the above base resin and has a structural unit represented by the following formula (5) (hereinafter, also referred to as "structural unit (F)").

[0107] [Chemical formula]

[0108] In the above formula (5), R 13 is a hydrogen atom, a methyl group or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, -COO-, -SO2ONH-, -CONH- or -OCONH-. R 14 is a monovalent fluorinated linear hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0109] Regarding the above R 13 from the viewpoint of the copolymerizability of the monomer that provides the structural unit (F), a hydrogen atom and a methyl group are preferable, and a methyl group is more preferable.

[0110] Regarding the above G L from the viewpoint of the copolymerizability of the monomer that provides the structural unit (F), a single bond and -COO- are preferable, and -COO- is more preferable.

[0111] Regarding the above R 14 Examples of the monovalent fluorinated linear hydrocarbon group having 1 to 20 carbon atoms represented by the above formula include those in which some or all of the hydrogen atoms of a linear or branched alkyl group having 1 to 20 carbon atoms are substituted with fluorine atoms.

[0112] Regarding the above R 14 Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula include those in which some or all of the hydrogen atoms of a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms are substituted with fluorine atoms.

[0113] Regarding the above R 14 is preferably a fluorinated linear hydrocarbon group, more preferably a fluorinated alkyl group, and even more preferably a 2,2,2-trifluoroethyl group, a 1,1,1,3,3,3-hexafluoropropyl group and a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0114] When the high-fluorine content resin has the structural unit (F), the lower limit of the content ratio of the structural unit (F) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 35 mol% with respect to all the structural units constituting the high-fluorine content resin. As the upper limit of the above content ratio, 95 mol% is preferable, 90 mol% is more preferable, and 85 mol% is even more preferable. By setting the content ratio of the structural unit (F) within the above range, the mass content ratio of fluorine atoms in the high-fluorine content resin can be adjusted more appropriately, and the uneven distribution on the surface layer of the resist film can be further promoted. As a result, the water repellency of the resist film during immersion exposure can be further improved.

[0115] In addition to the structural unit (F), the high-fluorine content resin may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter, also referred to as the structural unit (G)). By having the structural unit (G), the high-fluorine content resin can improve its solubility in an alkaline developer and suppress the occurrence of development defects.

[0116]

Chemical formula

[0117] The structural unit (G) is roughly classified into two cases: (x) having an alkali-soluble group and (y) having a group that dissociates by the action of an alkali to increase the solubility in an alkaline developer (hereinafter, also simply referred to as an "alkali-dissociable group"). Commonly to both (x) and (y), in the above formula (f-2), R C is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R D is a single bond, a (s + 1)-valent hydrocarbon group having 1 to 20 carbon atoms, an oxygen atom, a sulfur atom, -NR E -, a carbonyl group, -COO- or -CONH- bonded to the terminal on the R dd side of this hydrocarbon group, or a structure in which a part of the hydrogen atoms of this hydrocarbon group is substituted by an organic group having a hetero atom. R dd is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0118] When the structural unit (G) has (x) an alkali-soluble group, R F is a hydrogen atom, and A 1 is an oxygen atom, -COO-*, or -SO2O-*. * indicates the bonding site to R F . W 1 is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. When A 1 is an oxygen atom, W 1 is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group at the carbon atom to which A 1 is bonded. R E is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, a plurality of R E , W 1 , A 1 and R F may be the same or different from each other. By having (x) an alkali-soluble group in the structural unit (G), the affinity for the alkali developer can be increased, and development defects can be suppressed. As the structural unit (G) having (x) an alkali-soluble group, when A 1 is an oxygen atom and W 1 is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group, it is particularly preferable.

[0119] When the structural unit (G) has (y) an alkali-dissociable group, R F is a monovalent organic group having 1 to 30 carbon atoms, and A 1 is an oxygen atom, -NR aa -, -COO-*, or -SO2O-*. R aa is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * indicates the bonding site to R F . W 1 is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. R E is a single bond or a divalent organic group having 1 to 20 carbon atoms. When A 1 is -COO-* or -SO2O-*, W 1 or R F is A 1It has a fluorine atom on the carbon atom that binds to or on the carbon atom adjacent thereto. A 1 When A is an oxygen atom, W 1 and R E is a single bond, and R D is a structure in which a carbonyl group is bonded to the end on the R side of a hydrocarbon group having 1 to 20 carbon atoms, and R E is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R F , W E , A 1 , and R 1 and R F may be the same or different from each other. Since the structural unit (G) has a (y) alkali-dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development process. As a result, the affinity for the developer is significantly increased, and development defects can be suppressed more efficiently. As the structural unit (V) having a (y) alkali-dissociable group, A 1 is -COO-*, and R F or W 1 or both of them having a fluorine atom are particularly preferable.

[0120] R C is preferably a hydrogen atom and a methyl group, and more preferably a methyl group, from the viewpoints of copolymerizability of the monomer that gives the structural unit (G) and the like.

[0121] R E When it is a divalent organic group, a group having a lactone structure is preferable, a group having a polycyclic lactone structure is more preferable, and a group having a norbornane lactone structure is more preferable.

[0122] When the high-fluorine content resin has the structural unit (G), the lower limit of the content ratio of the structural unit (G) is preferably 40 mol%, more preferably 50 mol%, still more preferably 60 mol%, and particularly preferably 70 mol% with respect to all the structural units constituting the high-fluorine content resin. The upper limit of the above content ratio is preferably 98 mol%, more preferably 95 mol%, and still more preferably 92 mol%. By setting the content ratio of the structural unit (V) within the above range, the water repellency of the resist film during liquid immersion exposure can be further improved.

[0123] The lower limit of the Mw of the high-fluorine content resin is preferably 1,000, more preferably 2,000, still more preferably 3,000, and particularly preferably 5,000. The upper limit of the above Mw is preferably 50,000, more preferably 30,000, still more preferably 20,000, and particularly preferably 15,000.

[0124] The lower limit of the Mw / Mn of the high-fluorine content resin is usually 1, and more preferably 1.1. The upper limit of the above Mw / Mn is usually 5, preferably 3, more preferably 2, and still more preferably 1.9.

[0125] The lower limit of the content of the high-fluorine content resin is preferably 0.1 part by mass, more preferably 1 part by mass, still more preferably 1.5 parts by mass, and particularly preferably 2 parts by mass with respect to 100 parts by mass of the above base resin. The upper limit of the above content is preferably 15 parts by mass, more preferably 12 parts by mass, still more preferably 10 parts by mass, and particularly preferably 8 parts by mass.

[0126] By setting the content of the high-fluorine content resin within the above range, the high-fluorine content resin can be more effectively unevenly distributed on the surface layer of the resist film. As a result, the water repellency of the surface of the resist film during liquid immersion exposure can be further enhanced. The radiation-sensitive resin composition may contain one or more high-fluorine content resins.

[0127] (Synthesis method of high-fluorine content resin) The high-fluorine content resin can be synthesized by the same method as the above-described method for synthesizing the base resin.

[0128] [Radiation-sensitive acid generator] The radiation-sensitive acid generator is a component that generates an acid upon exposure. The acid generated upon exposure is considered to perform two functions in the radiation-sensitive resin composition depending on the strength of the acid. As the first function, when the resin contains a structural unit (B) having an acid-dissociable group and the acid generated upon exposure dissociates the acid-dissociable group of the structural unit (B), a function of generating a carboxy group or the like is mentioned. The radiation-sensitive acid generator having this first function is referred to as a radiation-sensitive acid generator (I). As the second function, under the pattern formation conditions using the above-described radiation-sensitive resin composition, the acid-dissociable group of the resin's structural unit (B) is not substantially dissociated, and a function of suppressing the diffusion of the acid generated from the above-described radiation-sensitive acid generator (I) in the unexposed portion is mentioned. The radiation-sensitive acid generator having this second function is referred to as a radiation-sensitive acid generator (II). It can be said that the acid generated from the radiation-sensitive acid generator (II) is a relatively weaker acid (an acid with a larger pKa) than the acid generated from the radiation-sensitive acid generator (I). Whether the radiation-sensitive acid generator functions as a radiation-sensitive acid generator (I) or a radiation-sensitive acid generator (II) is determined by the energy required for the acid-dissociable group of the resin's structural unit (B) to dissociate, the thermal energy conditions applied when forming a pattern using the radiation-sensitive resin composition, and the like. As the form of inclusion of the radiation-sensitive acid generator in the radiation-sensitive resin composition, it may be present alone as a compound (released from the polymer), incorporated as a part of the polymer, or both of these forms, but the form of being present alone as a compound is preferred.

[0129] When the radiation-sensitive resin composition contains the above-described radiation-sensitive acid generator (I), the polarity of the resin in the exposed portion increases, and the resin in the exposed portion becomes soluble in the developer in the case of development with an aqueous alkali solution, while becoming poorly soluble in the developer in the case of development with an organic solvent.

[0130] By containing the above radiation-sensitive acid generator (II), the radiation-sensitive resin composition can form a resist pattern that is excellent in pattern developability, LWR, and CDU performance.

[0131] Examples of the radiation-sensitive acid generator include onium salt compounds, sulfonimide compounds, halogen-containing compounds, diazoketone compounds, etc. Examples of the onium salt compounds include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, pyridinium salts, etc. Among these, sulfonium salts and iodonium salts are preferred.

[0132] Examples of the acid generated by exposure include those that generate sulfonic acid, carboxylic acid, and sulfonimide upon exposure. Such acids include (1) Compounds in which one or more fluorine atoms or fluorinated hydrocarbon groups are substituted on the carbon atom adjacent to the sulfonic group, (2) Compounds in which the carbon atom adjacent to the sulfonic group is not substituted with a fluorine atom or a fluorinated hydrocarbon group can be mentioned. Examples of the carboxylic acid generated by exposure include (3) Compounds in which one or more fluorine atoms or fluorinated hydrocarbon groups are substituted on the carbon atom adjacent to the carboxy group, (4) Compounds in which the carbon atom adjacent to the carboxy group is not substituted with a fluorine atom or a fluorinated hydrocarbon group can be mentioned. Among these, as the radiation-sensitive acid generator (I), those corresponding to the above (1) are preferred, and those having a cyclic structure are particularly preferred. As the radiation-sensitive acid generator (II), those corresponding to the above (2), (3), or (4) are preferred, and those corresponding to (2) or (4) are particularly preferred.

[0133] These radiation-sensitive acid generators may be used alone or in combination of two or more. From the viewpoint of ensuring the sensitivity and developability as a resist, the lower limit of the content of the radiation-sensitive acid generator (I) is preferably 2 parts by mass, more preferably 5 parts by mass, and even more preferably 8 parts by mass with respect to 100 parts by mass of the resin. From the viewpoint of ensuring transparency to radiation, the upper limit of the content of the radiation-sensitive acid generator (I) is preferably 30 parts by mass, more preferably 25 parts by mass, and even more preferably 20 parts by mass with respect to 100 parts by mass of the resin.

[0134] [Solvent] The radiation-sensitive resin composition contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least the resin, the radiation-sensitive acid generator, and, if desired, an acid diffusion control agent and the like.

[0135] Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents, and the like.

[0136] Examples of the alcohol solvent include monohydric alcohol solvents having 1 to 18 carbon atoms such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol solvents having 2 to 18 carbon atoms such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; polyhydric alcohol partial ether solvents in which a part of the hydroxy groups of the above polyhydric alcohol solvents are etherified, and the like.

[0137] Examples of the ether solvent include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; Cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; Aromatic ring-containing ether solvents such as diphenyl ether and anisole (methyl phenyl ether); Examples include polyhydric alcohol ether solvents obtained by etherifying the hydroxy groups of the above polyhydric alcohol solvents.

[0138] Examples of ketone solvents include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone: Cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone: 2,4-pentanedione, acetylacetone, acetophenone, etc. are included.

[0139] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; Chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, N-methylpropionamide, etc. are included.

[0140] Examples of ester solvents include, for example, Monocarboxylic acid ester solvents such as n-butyl acetate and ethyl lactate; Polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; Lactone solvents such as γ-butyrolactone and valerolactone; Carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; Examples include polycarboxylic acid diester solvents such as dipropylene glycol diacetate, methoxytriethylene glycol acetate, diethyl oxalate, ethyl acetoacetate, ethyl lactate, and diethyl phthalate.

[0141] Examples of the hydrocarbon solvent include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, di-iso-propylbenzene, and n-amylnaphthalene.

[0142] Among these, ester solvents and ketone solvents are preferred, polyhydric alcohol partial ether acetate solvents, cyclic ketone solvents, and lactone solvents are more preferred, and propylene glycol monomethyl ether acetate, cyclohexanone, and γ-butyrolactone are even more preferred. The radiation-sensitive resin composition may contain one or more solvents.

[0143] [Other optional components] The radiation-sensitive resin composition may contain other optional components in addition to the above components. Examples of the other optional components include, for example, acid diffusion control agents, uneven distribution promoters, surfactants, alicyclic skeleton-containing compounds, sensitizers, and the like. These other optional components may be used in combination of one or more of each.

[0144] (Acid diffusion control agent) The radiation-sensitive resin composition may contain an acid diffusion control agent as needed. As the acid diffusion control agent, the radiation-sensitive acid generator (II) among the above radiation-sensitive acid generators can be preferably employed. The acid diffusion control agent controls the diffusion phenomenon of the acid generated from the radiation-sensitive acid generator in the resist film by exposure, and exhibits the effect of suppressing undesirable chemical reactions in the unexposed region. In addition, the storage stability of the obtained radiation-sensitive resin composition is improved. Furthermore, the resolution of the resist pattern is further improved, and the change in the line width of the resist pattern due to the variation in the standing time from exposure to development processing can be suppressed, and a radiation-sensitive resin composition excellent in process stability can be obtained.

[0145] As the lower limit of the content of the acid diffusion control agent, 1 part by mass is preferable, 2 parts by mass is more preferable, and 4 parts by mass is even more preferable with respect to 100 parts by mass in total of the radiation-sensitive acid generator. As the upper limit of the above content, 20 parts by mass is preferable, 15 parts by mass is more preferable, and 10 parts by mass is even more preferable.

[0146] By setting the content of the acid diffusion control agent within the above range, the lithography performance of the radiation-sensitive resin composition can be further improved. The radiation-sensitive resin composition may contain one or more acid diffusion control agents.

[0147] (Phase separation promoter) The phase separation promoter has the effect of more efficiently causing the high-fluorine content resin to be phase-separated on the resist film surface. By incorporating this phase separation promoter into the radiation-sensitive resin composition, the addition amount of the high-fluorine content resin can be made less than before. Therefore, while maintaining the lithography performance of the radiation-sensitive resin composition, elution of components from the resist film into the immersion medium can be further suppressed, or immersion exposure can be performed at a higher speed by high-speed scanning, and as a result, the hydrophobicity of the resist film surface that suppresses immersion-derived defects such as watermark defects can be improved. Examples of those that can be used as such a phase separation promoter include low molecular weight compounds having a relative dielectric constant of 30 or more and 200 or less and a boiling point of 100°C or more at 1 atm. Specific examples of such compounds include lactone compounds, carbonate compounds, nitrile compounds, polyhydric alcohols, and the like.

[0148] Examples of the above lactone compounds include γ-butyrolactone, valerolactone, mevalonic lactone, norbornane lactone, and the like. Examples of the above carbonate compounds include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, and the like. Examples of the above nitrile compounds include succinonitrile and the like. Examples of the above polyhydric alcohols include glycerin and the like.

[0149] As the lower limit of the content of the uneven distribution promoter, 10 parts by mass is preferable, 15 parts by mass is more preferable, 20 parts by mass is further preferable, and 25 parts by mass is further preferable with respect to 100 parts by mass of the total amount of the resin in the radiation-sensitive resin composition. As the upper limit of the above content, 300 parts by mass is preferable, 200 parts by mass is more preferable, 100 parts by mass is further preferable, and 80 parts by mass is particularly preferable. The radiation-sensitive resin composition may contain one or more uneven distribution promoters.

[0150] (Surfactant) The surfactant has an effect of improving coatability, striation, developability, etc. Examples of the surfactant include nonionic surfactants such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene n-octylphenyl ether, polyoxyethylene n-nonylphenyl ether, polyethylene glycol dilaurate, and polyethylene glycol distearate; Commercially available products include KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), Polyflow No.75, No.95 (manufactured by Kyoeisha Chemical Co., Ltd.), F-Top EF301, EF303, EF352 (manufactured by Tochem Products Co., Ltd.), Megafac F171, F173 (manufactured by DIC Corporation), Fluorad FC430, FC431 (manufactured by Sumitomo 3M Limited), Asahi Guard AG710, Surflon S-382, SC-101, SC-102, SC-103, SC-104, SC-105, SC-106 (manufactured by Asahi Glass Co., Ltd.), etc. The content of the surfactant in the radiation-sensitive resin composition is usually 2 parts by mass or less with respect to 100 parts by mass of the resin.

[0151] (Compound containing an alicyclic skeleton) The compound containing an alicyclic skeleton has an effect of improving dry etching resistance, pattern shape, adhesion to a substrate, etc.

[0152] Examples of the compound containing an alicyclic skeleton include Adamantane derivatives such as 1-adamantanecarboxylic acid, 2-adamantanone, and t-butyl 1-adamantanecarboxylate; Deoxycholic acid esters such as t-butyl deoxycholate, t-butoxycarbonylmethyl deoxycholate, and 2-ethoxyethyl deoxycholate; Lithocholic acid esters such as t-butyl lithocholate, t-butoxycarbonylmethyl lithocholate, and 2-ethoxyethyl lithocholate; Examples include 3-[2-hydroxy-2,2-bis(trifluoromethyl)ethyl]tetracyclo[4.4.0.12,5.17,10]dodecane and 2-hydroxy-9-methoxycarbonyl-5-oxo-4-oxa-tricyclo[4.2.1.03,7]nonane. The content of the alicyclic skeleton-containing compound in the radiation-sensitive resin composition is usually 5 parts by mass or less with respect to 100 parts by mass of the resin.

[0153] (Sensitizer) A sensitizer exhibits the action of increasing the amount of acid generated from a radiation-sensitive acid generator or the like, and has the effect of improving the "apparent sensitivity" of the radiation-sensitive resin composition.

[0154] Examples of the sensitizer include carbazoles, acetophenones, benzophenones, naphthalenes, phenols, biacetyl, eosin, rose bengal, pyrenes, anthracenes, phenothiazines, and the like. These sensitizers may be used alone or in combination of two or more. The content of the sensitizer in the radiation-sensitive resin composition is usually 2 parts by mass or less with respect to 100 parts by mass of the resin.

[0155] <Method for preparing a radiation-sensitive resin composition> The radiation-sensitive resin composition can be prepared, for example, by mixing a resin, a radiation-sensitive acid generator, an acid diffusion controller as required, a high-fluorine content resin, etc., and a solvent at a predetermined ratio. After mixing, the radiation-sensitive resin composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.2 μm. The solid content concentration of the radiation-sensitive resin composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0156] <Resist Pattern Forming Method> The resist pattern forming method according to this embodiment is a step of forming a resist film with the radiation-sensitive resin composition (hereinafter, also referred to as "resist film forming step"), a step of exposing the resist film (hereinafter, also referred to as "exposure step"), and a step of developing the exposed resist film (hereinafter, also referred to as "development step").

[0157] Furthermore, the resist pattern forming method may include a step of providing an upper layer film on the resist film (hereinafter, also referred to as "upper layer film forming step") after the step of forming the resist film and before the step of exposing the resist film.

[0158] According to the resist pattern forming method, since the above-described radiation-sensitive resin composition is used, a resist pattern excellent in sensitivity, LWR performance, and pattern rectangularity can be formed. Hereinafter, each step will be described.

[0159] [Resist Film Forming Step] In this process, a resist film is formed using the radiation-sensitive resin composition. Examples of the substrate for forming this resist film include conventionally known ones such as silicon wafers, silicon dioxide, and wafers coated with aluminum. Further, for example, an organic or inorganic antireflection film disclosed in Japanese Patent Publication No. 6-12452, Japanese Unexamined Patent Application Publication No. 59-93448, etc. may be formed on the substrate. Examples of the coating method include spin coating, casting coating, roll coating, etc. After coating, pre-baking (PB) may be performed as necessary to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 140°C, preferably 80°C to 120°C. The PB time is usually 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The film thickness of the resist film to be formed is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0160] When performing immersion lithography, regardless of the presence or absence of a water-repellent polymer additive such as the high-fluorine content resin in the radiation-sensitive resin composition, for the purpose of avoiding direct contact between the immersion liquid and the resist film, an immersion protective film insoluble in the immersion liquid may be provided on the formed resist film. As the immersion protective film, a solvent-peeling type protective film that is peeled off by a solvent before the development process (see, for example, Japanese Unexamined Patent Application Publication No. 2006-227632), or a developer-peeling type protective film that is peeled off simultaneously with the development in the development process (see, for example, WO2005-069076, WO2006-035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peeling type immersion protective film.

[0161] Further, when the exposure process, which is the next process, is performed with radiation having a wavelength of 50 nm or less, it is preferable to use a resin having the structural units (B) and (E) as the base resin in the composition.

[0162] [Upper layer film forming process] In this process, an upper layer film is provided on the resist film using a composition for forming an upper layer film. As the composition for forming an upper layer film, for example, a conventionally known composition disclosed in Japanese Patent Application Laid-Open No. 2005-352384 or the like can be used. The composition for forming an upper layer film is applied on the resist film to form an upper layer film. As a method for applying the composition for forming an upper layer film, the same method as the method for applying the radiation-sensitive resin composition in the resist film forming step can be mentioned. In this process, it is preferable to perform pre-baking (PB) after applying the composition for forming an upper layer film. By forming the upper layer film on the resist film in this way, the immersion medium and the resist film do not come into direct contact, so that the lithography performance of the resist film is reduced due to the penetration of the liquid medium into the resist film, or the lens of the projection exposure apparatus is contaminated by the components eluted from the resist film into the liquid medium. This can be effectively suppressed.

[0163] The thickness of the upper layer film to be formed is preferably made as close as possible to an odd multiple of λ / 4m (where λ is the wavelength of the radiation and m is the refractive index of the upper layer film). By doing so, the reflection suppression effect at the upper interface of the resist film can be enhanced.

[0164] [Exposure Step] In this process, the resist film formed in the above-described resist film forming step is irradiated with radiation through a photomask (in some cases, through an immersion medium such as water) and exposed. As the radiation used for exposure, depending on the line width of the target pattern, for example, electromagnetic waves such as visible light, ultraviolet light, deep ultraviolet light, EUV (extreme ultraviolet light), X-rays, γ-rays; charged particle beams such as electron beams, α-rays, etc. can be mentioned. Among these, deep ultraviolet light, electron beams, and EUV are preferable, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferable, and ArF excimer laser light and EUV are even more preferable.

[0165] When performing exposure by liquid immersion exposure, examples of the liquid immersion liquid to be used include water, fluorine-based inert liquids, etc. The liquid immersion liquid is preferably a liquid that is transparent to the exposure light wavelength and has a temperature coefficient of refractive index as small as possible so as to minimize the distortion of the optical image projected onto the film. In particular, when the exposure light source is ArF excimer laser light (wavelength 193 nm), in addition to the above viewpoints, it is preferable to use water from the viewpoints of easy availability and ease of handling. When using water, an additive that reduces the surface tension of water and increases the interfacial activity may be added in a small proportion. This additive is preferably one that does not dissolve the resist film on the wafer and has a negligible effect on the optical coating on the lower surface of the lens. Distilled water is preferably used as the water to be used.

[0166] After the above exposure, post-exposure baking (PEB) is performed, and it is preferable to promote the dissociation of the acid-dissociable groups of the resin, etc. by the acid generated from the radiation-sensitive acid generator by exposure in the exposed portion of the resist film. By this PEB, a difference in solubility in the developer occurs between the exposed portion and the unexposed portion. The PEB temperature is usually 50°C to 180°C, and preferably 80°C to 130°C. The PEB time is usually 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds.

[0167] [Development process] In this process, the resist film exposed in the above exposure process is developed. Thereby, a predetermined resist pattern can be formed. After development, it is common to wash with a rinse liquid such as water or alcohol and then dry. The upper layer film can be easily removed by the developer during development or by the cleaning liquid during cleaning when cleaning is performed after development.

[0168] As the developer used for the above development, in the case of alkali development, for example, an alkaline aqueous solution in which at least one alkaline compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, 1,5-diazabicyclo-[4.3.0]-5-nonene is dissolved can be mentioned. Among these, an aqueous TMAH solution is preferable, and a 2.38 mass% aqueous TMAH solution is more preferable.

[0169] In addition, in the case of organic solvent development, organic solvents such as hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, or solvents containing an organic solvent can be mentioned. Examples of the above organic solvents include one or more of the solvents listed as the solvents of the above radiation-sensitive resin composition. Among these, ester solvents and ketone solvents are preferable. As the ester solvent, an acetic acid ester solvent is preferable, and n-butyl acetate and amyl acetate are more preferable. As the ketone solvent, a chain ketone is preferable, and 2-heptanone is more preferable. The content of the organic solvent in the developer is preferably 80 mass% or more, more preferably 90 mass% or more, further preferably 95 mass% or more, and particularly preferably 99 mass% or more. Examples of the components other than the organic solvent in the developer include water, silicone oil, etc.

[0170] Examples of the development method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of developing by raising the developer on the substrate surface by surface tension and allowing it to stand for a certain period of time (paddle method), a method of spraying the developer on the substrate surface (spray method), a method of continuously discharging the developer while scanning a developer discharge nozzle at a constant speed on a substrate rotating at a constant speed (dynamic dispense method), etc.

Examples

[0171] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. The measurement methods of various physical property values are shown below.

[0172] [Weight average molecular weight (Mw) and number average molecular weight (Mn)] The Mw and Mn of the resin were measured under the above conditions. Also, the dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0173] 13 C-NMR analysis] For the 13 C-NMR analysis of the resin, a nuclear magnetic resonance apparatus ("JNM-Delta400" manufactured by JEOL Ltd.) was used.

[0174] [Fluorine content] The fluorine content in the resin was calculated from the molar ratio of the monomer containing fluorine in the total resin after calculating the theoretical fluorine elemental analysis value of the monomer containing fluorine.

[0175] <Synthesis of monomer compound> [Synthesis Example 1] (Synthesis of compound (M-1)) To a reaction vessel, 20.0 mmol of ethyl 2-(bromomethyl)acrylate, 30.0 mmol of isopropyl alcohol, 40.0 mmol of diisopropylethylamine, and 50 g of dimethyl sulfoxide were added, and the mixture was stirred at 60°C for 12 hours. Then, the reaction solution was cooled to 30°C or lower, diluted by adding water, and then extracted by adding ethyl acetate, and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off. By purification by column chromatography, an ether derivative was obtained in a good yield.

[0176] ​A mixed solution of methanol:water (1:1 (mass ratio)) was added to the above ether derivative to make a 1 M solution, and then 20.0 mmol of sodium hydroxide was added, followed by reacting at room temperature for 1 hour. Then, the reaction solution was cooled to 30 °C or lower, and 1 M hydrochloric acid was added to make the system acidic. Dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off to obtain the carboxylic acid form in good yield.

[0177] To the above carboxylic acid form, 30.0 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 3.0 mmol of 4-dimethylaminopyridine, 30.0 mmol of α-hydroxy-γ-butyrolactone, and 50 g of dichloromethane were added, and the mixture was stirred at room temperature for 2 hours. Then, the reaction solution was cooled to 30 °C or lower, diluted by adding water, and then dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off. By purification using column chromatography, the compound represented by the following formula (M-1) (hereinafter, may be referred to as "compound (M-1)" or "monomer (M-1)") was obtained in good yield. The synthesis scheme of compound (M-1) is shown below.

[0178] [Chemical formula]

[0179] [Synthesis Examples 2 to 18] (Synthesis of Monomers (M-2) to (M-18)) Compounds represented by the following formulas (M-2) to (M-18) were synthesized in the same manner as in Synthesis Example 1 except that the raw materials and precursors were appropriately changed. Hereinafter, the compounds represented by formulas (M-2) to (M-18) may be referred to as "compound (M-2)" to "compound (M-18)" or "monomer (M-2)" to "monomer (M-18)", respectively.

[0180] [Chemical formula]

[0181] <Synthesis of [A] Resin and [E] High-Fluorine-Content Resin> Among the monomers used in the synthesis of each resin, monomers other than the above monomers (M-1) to (M-18) are shown below. In the following synthesis examples, unless otherwise specified, parts by mass mean the values when the total mass of the monomers used is 100 parts by mass, and mol% means the values when the total number of moles of the monomers used is 100 mol%.

[0182]

Chemical formula

[0183] [Synthesis Example 19] (Synthesis of Resin (A-1)) Monomer (M-1) and monomer (m-1) were dissolved in 2-butanone (200 parts by mass) so that the molar ratio was 50 / 50 (mol%), and AIBN (azobisisobutyronitrile) (5 mol% with respect to 100 mol% of the total monomers used) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in an empty reaction vessel, purged with nitrogen for 30 minutes, then the inside of the reaction vessel was set to 80 °C, and the above monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition was taken as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled with water to 30 °C or lower. The cooled polymerization solution was poured into methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, then filtered off and dried at 50 °C for 10 hours to obtain a white powder-like resin (A-1) (yield: 80%). The Mw of resin (A-1) was 6,100, and Mw / Mn was 1.61. Also, 13 As a result of C-NMR analysis, the content ratios of the respective structural units derived from monomer (M-1) and monomer (m-1) were 49.0 mol% and 51.0 mol%, respectively. The fluorine content was 0.0%.

[0184] [Synthesis Examples 20 to 50] (Synthesis of Resins (A-2) to (A-32)) Resins (A-2) to (A-32) were synthesized in the same manner as in Synthesis Example 19, except that the monomers having the types and blending ratios shown in Tables 1 and 2 below were used. The content ratios (mol%) of the respective structural units of the obtained resins and the physical property values (Mw, Mw / Mn, and fluorine content) are shown together in Tables 1 and 2 below. In Tables 1 and 2 below, "-" indicates that the corresponding monomer was not used.

[0185] [Table 1]

[0186] [Table 2]

[0187] [Synthesis Example 51] (Synthesis of Resin (A-33)) The monomer (M-3), monomer (m-1), and monomer (m-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) so that the molar ratio was 20 / 40 / 40 (mol%). AIBN (5 mol%) was added as an initiator to prepare a monomer solution. 1-Methoxy-2-propanol (100 parts by mass) was placed in a reaction vessel and purged with nitrogen for 30 minutes. Then, the inside of the reaction vessel was set to 80 °C, and the above monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled with water to 30 °C or lower. The cooled polymerization solution was poured into hexane (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane, then filtered and dissolved in 1-methoxy-2-propanol (300 parts by mass). Next, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and a hydrolysis reaction was carried out at 70 °C for 6 hours with stirring. After the reaction was completed, the residual solvent was distilled off. The obtained solid was dissolved in acetone (100 parts by mass) and dropped into water (500 parts by mass) to solidify the resin. The obtained solid was filtered and dried at 50 °C for 13 hours to obtain a white powder polymer (A-33) (yield: 73%). The Mw of resin (A-33) was 6,100, and Mw / Mn was 1.60. Also, 13 As a result of C-NMR analysis, the content ratios of the respective structural units derived from (M-3), (m-1), and (m-18) were 19.4 mol%, 40.7 mol%, and 39.9 mol%, respectively. The fluorine content was 0.0%.

[0188] [Synthesis Examples 52 to 57] (Synthesis of Polymer (A-34) to Polymer (A-39)) Resins (A-34) to (A-39) were synthesized in the same manner as in Synthesis Example 51, except that the monomers of the types and blending ratios shown in Tables 3 and 4 below were used. The content ratios (mol%) of the respective structural units and the physical property values (Mw, Mw / Mn, and fluorine content) of the obtained resins are shown together in Tables 3 and 4 below.

[0189]

Table 3

[0190] [Table 4]

[0191] [Synthesis Example 58] (Synthesis of High-Fluorine-Content Resin (E-1)) Monomer (m-1) and monomer (m-20) were dissolved in 2-butanone (200 parts by mass) so that the molar ratio was 10 / 90 (mol%), and AIBN (5 mol%) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel and purged with nitrogen for 30 minutes. Then, the inside of the reaction vessel was set to 80°C, and the above monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled with water to 30°C or lower. After replacing the solvent with acetonitrile (400 parts by mass), hexane (100 parts by mass) was added and stirred, and the operation of recovering the acetonitrile layer was repeated 3 times. By replacing the solvent with propylene glycol monomethyl ether acetate, a solution of high-fluorine-content resin (E-1) was obtained (yield: 81%). The Mw of the high-fluorine-content resin (E-1) was 6,300, and Mw / Mn was 1.67. Also, 13 As a result of C-NMR analysis, the content ratios of the respective structural units derived from (m-1) and (m-20) were 10.8 mol% and 89.2 mol%, respectively. The fluorine content was 14.5%.

[0192] [Synthesis Examples 59 to 61] (Synthesis of High-Fluorine-Content Resins (E-2) to (E-4)) High-fluorine-content resins (E-2) to (E-4) were synthesized in the same manner as in Synthesis Example 58 except that monomers of the types and blending ratios shown in Table 5 below were used. The content ratios (mol%) of the respective structural units and physical property values (Mw, Mw / Mn, and fluorine content) of the obtained high-fluorine-content resins are also shown in Table 5 below.

[0193] [Table 5]

[0194] <Preparation of Radiation-Sensitive Resin Composition> Components other than the [A] resin and [E] high-fluorine content resin used in the preparation of each radiation-sensitive resin composition are shown below.

[0195] [[B] Radiation-Sensitive Acid Generator] B-1 to B-6: Compounds represented by the following formulas (B-1) to (B-6)

[0196]

Chemical formula

[0197] [[C] Acid Diffusion Controller] C-1 to C-5: Compounds represented by the following formulas (C-1) to (C-5)

[0198]

Chemical formula

[0199] [[D] Solvent] D-1: Propylene glycol monomethyl ether acetate D-2: Cyclohexanone D-3: γ-Butyrolactone D-4: Ethyl lactate

[0200] [Preparation of Positive-Type Radiation-Sensitive Resin Composition for ArF Exposure] [Example 1] 100 parts by mass of (A-1) as the [A] resin, 14.0 parts by mass of (B-4) as the [B] radiation-sensitive acid generator, 8.0 parts by mass of (C-1)(C-2) as the [C] acid diffusion controller, 5.0 parts by mass (solid content) of (E-1) as the [E] high-fluorine content resin, and 3,230 parts by mass of a mixed solvent of (D-1) / (D-2) / (D-3) as the [D] solvent were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive resin composition (J-1).

[0201] [Examples 2 to 38 and Comparative Examples 1 to 12] Except for using the components of the types and contents shown in Table 6 below, radiation-sensitive resin compositions (J-2) to (J-38) and (CJ-1) to (CJ-12) were prepared in the same manner as in Example 1.

[0202] [Table 6]

[0203] [Formation of Resist Pattern Using Positive-Type Radiation-Sensitive Resin Composition for ArF Exposure] On a 12-inch silicon wafer, using a spin coater ("CLEAN TRACK ACT12" manufactured by Tokyo Electron Limited), a composition for forming an anti-reflection film for the lower layer ("ARC66" manufactured by Brewer Science, Inc.) was applied, and then heated at 205°C for 60 seconds to form an anti-reflection film for the lower layer with an average thickness of 105 nm. On this anti-reflection film for the lower layer, the positive-type radiation-sensitive resin composition for ArF exposure prepared above was applied using the spin coater, and PB (pre-bake) was performed at 90°C for 60 seconds. Then, by cooling at 23°C for 30 seconds, a resist film with an average thickness of 90 nm was formed. Next, for this resist film, using an ArF excimer laser immersion exposure apparatus ("TWINSCAN XT-1900i" manufactured by ASML), exposure was performed through a mask pattern with a 40 nm space and a 105 nm pitch under optical conditions of NA = 1.35 and Annular (σ = 0.8 / 0.6). After exposure, PEB (post-exposure bake) was performed at 90°C for 60 seconds. Then, the resist film was alkali-developed using a 2.38 mass% aqueous TMAH solution as an alkali developer, washed with water after development, and further dried to form a positive-type resist pattern (40 nm line and space pattern). Also, a positive-type resist pattern (40 nm hole, 105 nm pitch) was formed in the same manner as the above operation except that the mask pattern was changed.

[0204] [Evaluation] Regarding the resist pattern formed using the above-mentioned positive radiation-sensitive resin composition for ArF exposure, the sensitivity, LWR performance, and pattern rectangularity were evaluated according to the following methods. The results are shown in Table 7 below. For the length measurement of the resist pattern, a scanning electron microscope ("CG-5000" of Hitachi High-Technologies Corporation) was used.

[0205] [Sensitivity] In the formation of the resist pattern using the above-mentioned positive radiation-sensitive resin composition for ArF exposure, the exposure dose for forming a 40 nm line-and-space pattern was defined as the optimum exposure dose, and this optimum exposure dose was defined as the sensitivity (mJ / cm 2 ). The sensitivity was evaluated as "good" when it was 20 mJ / cm 2 or less, and as "bad" when it exceeded 20 mJ / cm 2 .

[0206] [LWR Performance] The mask size was adjusted to form a 40 nm line-and-space pattern by irradiating the optimum exposure dose obtained in the above sensitivity evaluation, and a resist pattern was formed. The formed resist pattern was observed from the top of the pattern using the above scanning electron microscope. The variation in line width was measured at 500 points in total, and the 3-sigma value was obtained from the distribution of the measured values, and this 3-sigma value was defined as LWR (nm). The smaller the value of LWR, the smaller the line roughness and the better the result. The LWR performance was evaluated as "good" when the value was 2.5 nm or less, and as "bad" when it exceeded 2.5 nm.

[0207] [Pattern Rectangularity] Regarding the 40 nm line-and-space pattern formed by irradiating the optimum exposure dose obtained in the above sensitivity evaluation, it was observed using the above scanning electron microscope, and the cross-sectional shape of the line-and-space pattern was evaluated. The rectangularity of the resist pattern was evaluated as "〇" if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape was 1 or more and 1.05 or less, as "△" if it was more than 1.05 and 1.10 or less, and as "×" if it exceeded 1.10.

[0208]

Table 7

[0209] As is clear from the results in Table 7, the radiation-sensitive resin composition of the example had good sensitivity, LWR performance, and pattern rectangularity when used for ArF exposure, whereas in the comparative examples, each characteristic was inferior to that of the example. Therefore, when the radiation-sensitive resin composition of the example is used for ArF exposure, a resist pattern with high sensitivity and good LWR performance and pattern rectangularity can be formed.

[0210] [Preparation of Positive-Type Radiation-Sensitive Resin Composition for Extreme Ultraviolet (EUV) Lithography] [Example 39] [A] 100 parts by mass of (A-33) as a resin, [B] 12.0 parts by mass of (B-4) as a radiation-sensitive acid generator, [C] 6.0 parts by mass of (C-1) as an acid diffusion controller, [E] 5.0 parts by mass of (E-4) as a high fluorine content resin, and 6,110 parts by mass of a mixed solvent of (D-1) / (D-4) as [D] a solvent were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive resin composition (J-39).

[0211] [Examples 40 to 50 and Comparative Examples 13 to 15] Radiation-sensitive resin compositions (J-40) to (J-50) and (CJ-13) to (CJ-15) were prepared in the same manner as in Example 39 except that the components of the types and contents shown in Table 8 below were used.

[0212]

Table 8

[0213] [Formation of Resist Pattern Using Positive-Type Radiation-Sensitive Resin Composition for EUV Lithography] On a 12-inch silicon wafer, using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), a composition for forming an underlying antireflection film ("ARC66" from Brewer Science, Inc.) was applied, and then heated at 205 °C for 60 seconds to form an underlying antireflection film with an average thickness of 105 nm. On this underlying antireflection film, the prepared positive radiation-sensitive resin composition for EUV lithography was applied using the above spin coater, and PB was performed at 130 °C for 60 seconds. Then, by cooling at 23 °C for 30 seconds, a resist film with an average thickness of 55 nm was formed. Next, this resist film was exposed using an EUV exposure apparatus ("NXE3300" from ASML) with NA = 0.33, illumination condition: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120 °C for 60 seconds. Then, the resist film was alkali-developed using a 2.38 mass% aqueous TMAH solution as the alkali developer, washed with water after development, and further dried to form a positive resist pattern (32 nm line and space pattern).

[0214] <Evaluation> Regarding the resist pattern formed using the above positive radiation-sensitive resin composition for EUV lithography, sensitivity, LWR performance, and pattern rectangularity were evaluated according to the following methods. The results are shown in Table 9 below. For the length measurement of the resist pattern, a scanning electron microscope ("CG-5000" from Hitachi High-Technologies Corporation) was used.

[0215] [Sensitivity] In the formation of the resist pattern using the above positive radiation-sensitive resin composition for EUV lithography, the exposure dose for forming a 32 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was defined as the sensitivity (mJ / cm 2 ). Sensitivity was evaluated as "good" when it was 25 mJ / cm 2 or less, and "bad" when it exceeded 25 mJ / cm 2 .

[0216] [LWR Performance] The mask size was adjusted to form a resist pattern by irradiating the optimum exposure dose obtained in the above sensitivity evaluation so as to form a 32 nm line and space pattern. The formed resist pattern was observed from above the pattern using the above scanning electron microscope. The variation in line width was measured at 500 points in total, the 3-sigma value was obtained from the distribution of the measured values, and this 3-sigma value was defined as LWR (nm). The smaller the value of LWR, the smaller the line wobbling and the better the performance. The LWR performance was evaluated as "good" when it was 3.0 nm or less and "bad" when it exceeded 3.0 nm.

[0217] [Pattern rectangularity] Regarding the 32 nm line and space pattern formed by irradiating the optimum exposure dose obtained in the above sensitivity evaluation, it was observed using the above scanning electron microscope, and the cross-sectional shape of the line and space pattern was evaluated. The rectangularity of the resist pattern was evaluated as "〇" if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape was 1 or more and 1.05 or less, "△" if it was more than 1.05 and 1.10 or less, and "×" if it was more than 1.10.

[0218]

Table 9

[0219] As is clear from the results in Table 9, the radiation-sensitive resin composition of the example had good sensitivity, LWR performance, and pattern rectangularity when used for EUV exposure, whereas in the comparative example, each characteristic was inferior to that of the example.

[0220] [Preparation of a negative-type radiation-sensitive resin composition for ArF exposure, formation and evaluation of a resist pattern using this composition] [Example 51] 100 parts by mass of (A-3) as a resin, 15.0 parts by mass of (B-3) as a radiation-sensitive acid generator, 8.0 parts by mass of (C-2) as an acid diffusion controller, 2.0 parts by mass (solid content) of (E-3) as a high fluorine content resin, and 3,230 parts by mass of a mixed solvent of (D-1) / (D-2) / (D-3) as a solvent were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive resin composition (J-51).

[0221] On a 12-inch silicon wafer, using a spin coater ("CLEAN TRACK ACT12" of Tokyo Electron Limited), a composition for forming an underlying antireflective film ("ARC66" of Brewer Science, Inc.) was applied, and then heated at 205°C for 60 seconds to form an underlying antireflective film with an average thickness of 105 nm. Using the above spin coater, the prepared negative-type radiation-sensitive resin composition (J-51) for ArF exposure was applied on this underlying antireflective film, and PB (pre-bake) was performed at 90°C for 60 seconds. Then, by cooling at 23°C for 30 seconds, a resist film with an average thickness of 90 nm was formed. Next, with respect to this resist film, using an ArF excimer laser immersion exposure apparatus ("TWINSCAN XT-1900i" of ASML), under optical conditions of NA = 1.35 and Annular (σ = 0.8 / 0.6), it was exposed through a mask pattern with a 40 nm space and a 105 nm pitch. After exposure, PEB (post-exposure bake) was performed at 90°C for 60 seconds. Then, the resist film was developed with an organic solvent developer of n-butyl acetate and dried to form a negative-type resist pattern (40 nm line and space pattern).

[0222] The resist pattern using the above negative-type radiation-sensitive resin composition for ArF exposure was evaluated in the same manner as the evaluation of the resist pattern using the above positive-type radiation-sensitive resin composition for ArF exposure. As a result, even when the radiation-sensitive resin composition of Example 51 formed a negative-type resist pattern by ArF exposure, the sensitivity, LWR performance, and pattern rectangularity were good.

[0223] [Preparation of Negative-Type Radiation-Sensitive Resin Composition for EUV Lithography, Formation and Evaluation of Resist Pattern Using this Composition] [Example 52] [A] 100 parts by mass of (A-33) as a resin, [B] 20.0 parts by mass of (B-4) as a radiation-sensitive acid generator, [C] 12.0 parts by mass of (C-1) as an acid diffusion controller, [E] 2.0 parts by mass of (E-4) as a high-fluorine content resin, and 6,110 parts by mass of a mixed solvent of (D-1) / (D-4) = 70 / 30 (mass ratio) as [D] a solvent were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive resin composition (J-52).

[0224] On a 12-inch silicon wafer, using a spin coater ("CLEAN TRACK ACT12" manufactured by Tokyo Electron Limited), a composition for forming an anti-reflection film for the lower layer ("ARC66" manufactured by Brewer Science, Inc.) was applied and then heated at 205°C for 60 seconds to form an anti-reflection film for the lower layer with an average thickness of 105 nm. The radiation-sensitive resin composition for EUV lithography prepared above was applied on this anti-reflection film for the lower layer using the above spin coater, and PB was performed at 130°C for 60 seconds. Then, by cooling at 23°C for 30 seconds, a resist film with an average thickness of 55 nm was formed. Next, this resist film was exposed using an EUV exposure apparatus ("NXE3300" manufactured by ASML) with NA = 0.33, illumination condition: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. Then, the resist film was developed with an organic solvent developer, n-butyl acetate, and dried to form a negative-type resist pattern (32 nm line and space pattern).

[0225] The resist pattern using the above negative-type radiation-sensitive resin composition for EUV exposure was evaluated in the same manner as the evaluation of the resist pattern using the above positive-type radiation-sensitive resin composition for EUV exposure. As a result, even when the radiation-sensitive resin composition of Example 52 formed a negative-type resist pattern by EUV exposure, the sensitivity, LWR performance, and pattern rectangularity were good.

Industrial Applicability

[0226] According to the radiation-sensitive resin composition and the method for forming a resist pattern of the present invention, a resist pattern having good sensitivity to exposure, excellent LWR performance, and pattern rectangularity can be formed. Therefore, these can be suitably used in the processing process of semiconductor devices and the like, which are expected to be further miniaturized in the future.

Claims

1. A resin containing a structural unit (A) represented by the following formula (1) and a structural unit (B) having an acid dissociable group, a radiation-sensitive acid generator, and a solvent comprising a radiation-sensitive resin composition. 【Chemical 1】 (In the above formula (1), R １ is a monovalent hydrocarbon group having 3 to 20 carbon atoms, which may or may not be substituted with a halogen atom. X is -O- or -S-. L ａ１ is a divalent hydrocarbon group having 1 to 10 carbon atoms, which may or may not be substituted with a halogen atom. R Ｐ is a monovalent organic group having at least one structure selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure.)

2. R in the above formula (1) １ The radiation-sensitive resin composition according to claim 1, wherein each of them is a monovalent chain hydrocarbon group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group.

3. L in the above formula (1) ａ１ The radiation-sensitive resin composition according to claim 1 or 2, wherein L is a divalent chain hydrocarbon group.

4. L in the above formula (1) ａ１ The radiation-sensitive resin composition according to claim 3, wherein ａ１ is a methylene group.

5. R in the above formula (1) Ｐ is a radiation-sensitive resin composition according to any one of claims 1 to 4 represented by the following formula (A). [Chemical 2] (In the above formula (A), L ａ２ is a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted or unsubstituted. Y is a single bond or a divalent linking group selected from -O-, -CO-, -NH-, -SO ２ - or a combination thereof. L ａ3 is a single bond or a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms. R Ｐ１ is a substituted or unsubstituted lactone structure, cyclic carbonate structure or sultone structure. * is a bond to -O- in the above formula (1).)

6. The radiation-sensitive resin composition according to any one of Claims 1 to 5, wherein the fluorine content in the resin is 10% by mass or less.

7. The radiation-sensitive resin composition according to any one of Claims 1 to 6, wherein the content of the structural unit (A) in the resin is 5 mol% or more and 80 mol% or less based on all the structural units constituting the resin.

8. The resin further contains a structural unit (C) (excluding the structural unit corresponding to the structural unit (A)) selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure The radiation-sensitive resin composition according to any one of Claims 1 to 7.

9. The radiation-sensitive resin composition according to any one of Claims 1 to 8, wherein the resin has two or more combinations of the structural unit (B).

10. The radiation-sensitive resin composition according to any one of Claims 1 to 9, wherein the structural unit (B) in the resin is a structural unit represented by the following formula (3-1). 【Chemical Formula 3】 (In the above formula (3-1), R ７ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ８ is a monovalent hydrocarbon group having 1 to 20 carbon atoms. i is an integer of 1 to 4.)

11. A method for forming a resist pattern, comprising the steps of forming a resist film with the radiation-sensitive resin composition according to any one of Claims 1 to 10, exposing the resist film, and developing the exposed resist film.

12. The method for forming a resist pattern according to Claim 11, further comprising a step of providing an upper layer film on the resist film after the step of forming the resist film and before the step of exposing the resist film.

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