1  US 7,511,179 B2  2  FLUORINE-CONTAINING POLYMER,  RESIST COMPOSITION PREPARED FROM  SAME AND NOVEL  FLUORINE-CONTAINING MONOMER  CROSS-REFERENCE TO RELATED  APPLICATIONS  BACKGROUND OF THE INVENTION  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- 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.  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  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.  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.  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.  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.  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.  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.  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.  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.  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.  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 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.  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.  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.  ketal (KrF resist), methacrylic acid resins in which an acid› labile ester group is introduced to carboxyl (ArF resist) and  the like. 