content_image/948452.jpg content_image/948448.jpg content_image/948451.jpg content_image/948450.jpg content_image/948449.jpg
and/or the formula (b-5): 

<img src='content_image/948452.jpg'>

wherein Z 5 and Z$^{6 }$are as defined above, can be obtained. 

In the above-mentioned formulae (b-4) and (b-5), it is preferable from the viewpoint of copolymerizability that Z 5 and Z 6 are the same or different and each is at least one selected from COOH or a derivative of carboxylic acid group. 

Example of preferred derivative of carboxylic acid group is one selected from carboxylic acid esters, functional groups protected by a protective group which can convert the func- tional group to COOH group due to reaction with an acid, acid halides and acid amides. 

In the fluorine-containing polymer of the present inven› tion, the structural unit Ml derived from a fluoroolefin is at least one structural unit selected from structural units derived from fluorine-containing ethylenic monomers having 2 or 3 carbon atoms. Examples thereof are, for instance, tetrafluo› roethylene, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, trifluoroethylene, hexafluoropropylene and the like. 

Among them, preferred are structural units derived from tetrafluoroethylene and chlorotrifluoroethylene because transparency and dry etching resistance can be improved in resist application. 

In the polymers of the formulae (Ma) and (Mb) of the present invention, the structural unit Ml, the structural unit M2a or M2b and the structural unit N are contained in amounts of from 1 to 99% by mole, from 1 to 99% by mole and from Oto 98% by mole, respectively. Provided that (Ml)+ (M2a) or (Ml)+(M2b) is 100% by mole, a percent by mole ratio of (Ml)/(M2a) or (Ml)/(M2b) is preferably 80/20 to 20/80, more preferably 70/30 to 30/70, further preferably 60/40 to 40/60. 

The present inventors have found that a specific ethylenic monomer having functional group can be copolymerized in addition to the fluoroolefin and the above-mentioned mono› mer being capable of introducing a monocyclic structure, thereby making it possible to introduce the functional group to the fluorine-containing polymer having a monocyclic structure in its trunk chain. 

Accordingly photosensitivity necessary in resist applica› tion and various useful functions necessary in other applica› tions can be imparted to the polymer. 

The structural unit derived from an ethylenic monomer having functional group which is copolymerized with the fluoroolefin and the monomer introducing the monocyclic structure is a structural unit derived from an ethylenic mono› mer and represented by the formula (N-1): 

<img src='content_image/948448.jpg'>

wherein X $^{1 }$and X 2 are the same or different and each is H or F; X 3 is H, F, CH 3 orCF 3 ; X$^{4 }$andX$^{5 }$are the same or different 

(b- 5 ) 

(N-1) 60 

and each is H, F or CF 3 ; Rf is a fluorine-containing alkylene group having 1 to 40 carbon atoms or a fluorine-containing alky lene group having 2 to 100 carbon atoms and ether bond; a is 0 or an integer of from 1 to 3; b and c are the same or different and each is 0 or 1; Z 2 is at least one functional group selected from the group consisting of OH group, COOH group, a derivative of carboxylic acid group and a functional group protected by a protective group which can convert the functional group to OH group due to reaction with an acid. 

Examples thereof are, for instance, as follows. 

(i) Structural unit derived from acrylic monomer and repre› sented by: 

<img src='content_image/948451.jpg'>

wherein X $^{1 }$and X 2 are the same or different and each is H or F; X 3 is H, F, CH 3 or CF 3 ; R is selected from hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a fluorine› containing alkyl group having 1 to 20 carbon atoms, a fluo› rine-containing alky 1 group having 2 to 100 carbon atoms and ether bond or a fluorine-containing aryl group having 3 to 20 carbon atoms. 

In the above-mentioned formula, examples of preferred -Rare: 

hydrogen atom, 

----C(CH3)3, -CH2CH2OH, -(CH2)m(CF 2)n -F, -(CH2)m (CF$_{2}$ )n-H, 

-(CH 2 )m(CF $_{2}$ )n -Cl, (mis an integer of from 1 to 5, n is an integer of from 1 to 10) 

----CH(CF 3)2, -CH2CFHCF 3, -(CH2)m(CF 2)n ----CF(CF 3)2, (mis an integer of from 1 to 5, n is an integer of from 1 to 10) 

<img src='content_image/948450.jpg'>

(mis an integer of from 1 to 10) 

<img src='content_image/948449.jpg'>

and the like. 

Examples thereof are, for instance, acrylic acid, meth› acrylic acid, a-fluoroacrylic acid, a-trifluoromethylacrylic acid, acrylic acid esters, a-fluoroacrylic acid esters, meth› acrylic acid esters, a-trifluoromethylacrylic acid esters, hydroxyethyl acrylate, hydroxyethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, acrylamides, methacryla› mides and the like. 

The introduction of the structural unit derived therefrom is preferred because it is possible to enhance solubility in a solvent, photosensitivity with a photoacid generator, adhe› sion to a substrate and compatibility with a photoacid gen- erator and other additives. 1 2 3 

It is preferable that at least any one ofX , X and X has fluorine atom and/or X 3 is a trifluoromethyl group, from the 

