content_image/931244.jpg
<img src='content_image/931244.jpg'>

R represents a hydrogen atom, a methyl group or a trifluo› romethyl group, RA represents a hydrogen atom or a methyl group, andR $^{6 }$represents a single bond or an alkylene group of 1 to 3 carbon atoms. 

As the structural unit ( a0-1 ), one type of structural unit may be used alone, or two or more types of structural units may be used in combination. 

In the component (Al’), the amount of the structural unit (a0-1) based on the combined total of all structural units constituting the component (Al’) is preferably 1 to 40 mmol %, more preferably 5 to 35 mo! %, and still more preferably 5 to 30 mmol %. By ensuring the above-mentioned range, the lithography properties are improved. Further, solubility in an organic solvent can be increased. 

(Structural Unit (a0-2)) 

The structural unit (a0-2) is a structural unit that generates acid upon exposure and contains a group represented by general formula (a0-2’). The main chain of the structural unit (a0-2) is not particularly limited. By including the structural unit (a0-2), outgas can be suppressed. Further, the acid gen› erator can be uniformly distributed within the resist film, which results in the improvement of the lithography proper› ties. In addition, lowering of Tg can be suppressed. As the main chain of the monomer for deriving the structural unit ( a0-2), any one which can be polymerized with the monomers for deriving the structural units ( a5-l) and ( a0-1) can be used, e.g., a main chain having a (meth)acryloyl group or a vinyl group. 

Firstly, the cation moiety excluding the anion moiety in general formula (a0-2’), i.e., the portion excluding x- will be described. 

<<Cation Moiety>> 

In general formula (a0-2’), R$^{7 }$is the same as defined for R 7 in general formula ( a0-1 ), and is preferably a hydrogen atom or a methyl group. 

Further, R $^{7 }$may be the same or different from R $^{7 }$in general formula (a0-1). 

In general formula (a0-2’), Y represents a divalent linking group. 

Preferable examples ofY include a divalent hydrocarbon group which may have a substituent, and a divalent linking group containing a hetero atom. 

A hydrocarbon "has a substituent" means that part or all of the hydrogen atoms within the hydrocarbon group is substi› tuted with groups or atoms other than hydrogen. 

The hydrocarbon group may be either an aliphatic hydro› carbon group or an aromatic hydrocarbon group. An "ali- phatic hydrocarbon group" refers to a hydrocarbon group that has no aromaticity. 

-continued 

The aliphatic hydrocarbon group may be saturated or unsaturated. In general, the aliphatic hydrocarbon group is preferably saturated. 

As specific examples of the aliphatic hydrocarbon group, a linear or branched aliphatic hydrocarbon group, and an ali› phatic hydrocarbon group confining a ring in the structure thereof can be given. 

The linear, or branched aliphatic hydrocarbon group pref› erably has 1 to 10 carbon atoms, more preferably 1 to 8, still 10 more preferably 1 to 5, and most preferably 1 or 2. 

As the linear aliphatic hydrocarbon group, a linear alkylene group is preferable. Specific examples thereof include a methylene group [----CH 2 -], an ethylene group [-(CH 2 ) 2 -], a trimethylene group [-(CH 2 )$_{3}$ -], a tetram› ethylene group [-(CH 2 )$_{4}$ -] and a pentamethylene group [-(CH2)s-l- 

As the branched aliphatic hydrocarbon group, branched alkylene groups are preferable, and specific examples include various alkylalkylene groups, including alkylmethylene groups such as ----CH(CH$_{3}$)-, ----CH(CH 2 CH$_{3}$)-, ----C(CH$_{3}$ ) 2 -, -C(CH$_{3}$)(CH 2 CH$_{3}$)-, -C(CH$_{3}$ ) (CH 2 CH 2 CH$_{3}$)-, and ----C(CH 2 CH$_{3}$ ) 2 -; alkylethylene groups such as ----CH(CH$_{3}$)CH 2 -, ----CH(CH$_{3}$)CH(CH$_{3}$)-, ----C(CH$_{3}$ ) 2 CH 2 -, -CH(CH 2 CH$_{3}$)CH 2 -, and ----C(CH 2 CH$_{3}$ ) 2 ----CH 2 -; alkyltrimethylene groups such as ----CH(CH$_{3}$)CH 2 CH 2 -, and ----CH 2 CH(CH$_{3}$)CH 2 -; and alkyltetramethylene groups such as -CH(CH$_{3}$ ) CH 2 CH 2 CH 2 -, and ----CH 2 CH(CH$_{3}$)CH 2 CH 2 -. As the alkyl group within the alkylalkylene group, a linear alkyl group of 1 to 5 carbon atoms is preferable. 

The linear or branched aliphatic hydrocarbon group (chain-like aliphatic hydrocarbon group) may or may not have a substituent. Examples of substituents include a fluo- rine atom, a fluorinated alkyl group of 1 to 5 carbon atoms, and an oxygen atom (=0). 

As examples of the hydrocarbon group containing a ring in the structure thereof, a cyclic aliphatic hydrocarbon group (a group in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring), and a group in which the cyclic aliphatic hydrocarbon group is bonded to the terminal of the aforementioned chain-like aliphatic hydrocarbon group or interposed within the aforementioned chain-like aliphatic hydrocarbon group, can be given. 

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably 3 to 12 carbon atoms. 

The cyclic aliphatic hydrocarbon group may be either a polycyclic group or a monocyclic group. As the monocyclic group, a group in which two hydrogen atoms have been removed from a monocycloalkane of 3 to 6 carbon atoms is preferable. Examples of the monocycloalkane include cyclo› pentane and cyclohexane. As the polycyclic group, a group in which two hydrogen atoms have been removed from a poly› cycloalkane of7 to 12 carbon atoms is preferable. Examples of the polycycloalkane include adamantane, norbomane, isobomane, tricyclodecane and tetracyclododecane. 

The cyclic aliphatic hydrocarbon group may or may not have a substituent. Examples of the substituent include an alkyl group of 1 to 5 carbon atoms, a fluorine atom, a fluori- nated alkyl group ofl to 5 carbon atoms, and an oxygen atom (=0). 

Examples of aromatic hydrocarbon groups include a diva› lent aromatic hydrocarbon group in which one hydrogen atom has been removed from a benzene ring of a monovalent aromatic hydrocarbon group such as a phenyl group, a bi phe› nyl group, a fluorenyl group, a naphthyl group, an anthryl group or a phenanthryl group; 

