# FLUORINE-CONTAINING POLYMER, RESIST COMPOSITION PREPARED FROM SAME AND NOVEL FLUORINE-CONTAINING MONOMER 

## CROSS-REFERENCE TO RELATED APPLICATIONS 

This application is a Divisional ofU.S. application Ser. No. 10/815,801 filed Apr. 2, 2004 now U.S. Pat. No. 7,115,690, which is a continuation-in-part of PCT international applica› tion No. PCT/JP02/10242 filed on Oct. 2, 2002; the above› noted applications incorporated herein by reference in their entirety. 

## BACKGROUND OF THE INVENTION 

The present invention relates to a novel fluorine-containing unsaturated cyclic compound, a novel fluorine-containing polymer having an aliphatic monocyclic structure in its trunk chain, and a chemically amplifying photoresist composition which is obtained from the fluorine-containing polymer, is excellent in transparency and possesses improved dry etching resistance. 

As a result of an increasing necessity for high integration of a large scale integrated circuit (LSI), microfabrication tech› nology is required for photolithography. In order to satisfy such requirements, there have been tried to use, as exposure light sources, a deep ultraviolet, a KrF excimer laser beam (wavelength: 248 nm) and a ArF excimer laser beam (wave› length: 193 nm) which have a wavelength shorter than con› ventional g-rays (wavelength: 436 nm) and i-rays (wave› length: 365 nm). Those light sources are put into practical use. 

Recently a process using a F $_{2 }$laser beam (wavelength: 157 nm) having a wavelength in a vacuum ultraviolet region has been studied in an ultra-microfabrication technology and is considered promising as an exposure technology aiming at a technology node of0.1 µm. 

On the other hand, in the pattern formation, a chemically amplifying resist which becomes advantageous in transpar› ency, resolution, sensitivity and dry etching resistance in cases of energy rays having various wavelengths has been studied. The chemically amplifying resist means, for example, in case of a positive resist, an energy-sensitive com- position comprising a resin being soluble in an alkali devel› oping solution and having an introduced substituent which has an effect of inhibiting dissolution of the resin but is deprotected due to action of an acid, and a compound which generates an acid by irradiation of energy rays such as light and electron beam (hereinafter referred to as a photoacid generator). When the composition is irradiated with light or electron beam, an acid is generated from the photoacid gen› erator, and by heating (post-exposure bake, which may be hereinafter referred to as "PEB") after the exposure to light, the substituent which has been giving a dissolution inhibiting effect on the resin is deprotected due to action of an acid. As a result, the exposed portion becomes soluble in alkali, and by treating the exposed portion with an alkali developing solu› tion, a positive resist pattern can be obtained. In that case, the acid acts as a catalyst and exhibits its effect in a very small amount. Also action of the acid becomes active by the PEB and a chemical reaction is accelerated like a chain reaction, and thus sensitivity is enhanced. 

Examples of conventional resins for chemically amplify- ing resist are phenol resins in which a part or the whole of hydroxyl is protected by a protective group such as acetal or 

ketal (KrF resist), methacrylic acid resins in which an acid› labile ester group is introduced to carboxyl (ArF resist) and the like. 

However those conventional resist polymers have strong absorption in a wavelength range of a vacuum ultraviolet region and have a significant problem that transparency against F $_{2 }$ laser beam having a wavelength of 157 nm which is studied in a process for ultra fine pattern is low ( an absorp› tion coefficient is high). Therefore for exposing with F $_{2 }$ laser, it is necessary to make a resist film thickness very thin and it is substantially difficult to use the polymers as a single layer F$_{2 }$resist. 

R. R. Kunz, T. M. Bloomstein, et al. suggest in Journal of PhotopolymerScienceand Technology (Vol. 12, No. 4 (1999) 561-569) that fluorocarbons have good transparency at 157 nm as compared with other various materials and have pos› sibility of use as a F $_{2 }$ resist. 

However in that literature, there is only description that existing fluorocarbon polymers are high in transparency at 157 nm, but there is no description as to preferable structure of fluorine-containing polymers. Also, for example, with respect to a fluorine-containing polymer having functional group necessary for a positive type or negative type chemi› cally amplifying resist, neither evaluation of transparency nor synthesis of the polymer was made. Moreover the literature does not suggest a fluorine-containing base polymer material being preferable as a chemically amplifying resist and a pref› erable resist composition obtained therefrom at all, and there is found no possibility of forming a F $_{2 }$resist pattern by using a fluorine-containing polymer. 

Thereafter A. E. Feiring, et al. ofE.I. du Pont de Nemours and Company disclosed in WO00/17712 pamphlet (pub› lished Mar. 30, 2000) that a specific fluorine-containing poly› mer is useful for F $_{2 }$ resist application. 

That pamphlet describes the use of a fluorine-containing polymer having a structural unit of fluoroolefin and a struc› tural unit having a polycyclic condensed structure which is mainly a structural unit derived from norbornene. 

Also an acid-labile (acid-decomposable) functional group necessary for a positive type resist is introduced to the fluo› rine-containing polymer by copolymerizing a conventional acrylic, methacrylic, norbornene or vinyl ester monomer with a monomer having an introduced acid-labile (acid-decom- posable) functional group. 

Further thereafter A. E. Feiring, et al. of E.I. du Pont de Nemours and Company disclosed in WO00/67072 pamphlet (published Nov. 9, 2000) that a fluorine-containing polymer having -C(Rf)(Rf’)OH or -C(Rf)(Rf’)O-Rb is useful for F $_{2 }$ resist application. 

In that pamphlet, a structural unit of norbornene in which ----C(Rf)(Rf’)OH or-C(Rf)(Rf’)O-Rb is bonded through a part of-CH$_{2}$OCH$_{2}$-is disclosed. Further there is disclosed norbornene derivatives having ----C(Rf)(Rf’)OH or -C(Rf) (Rf’)O-Rb as an example of a fluorine-containing polymer to be used for a resist. 

However in those patent publications, there is no descrip› tion as to the use of a fluorine-containing copolymer com› prising a structural unit of fluoroolefin and a structural unit having an aliphatic monocyclic structure in its trunk chain, and further there is no description as to an aliphatic monocy› clic structure to which a functional group necessary for a resist is introduced. 

Further Katsuyama, et al. of Matsushita Electric Industrial Co., Ltd. proposed a method of forming a pattern with expo› sure light having a wavelength of from 1 to 180 nm using a resist material containing halogen atom, etc. (JP2000- 321774A published Nov. 24, 2000). However there is dis- 

