8  US 8,283,102 B2  7  wherein R$_{1 }$ is a hydrogen atom, a trifluoromethyl group, a  C$_{1 }$ -Cs  alkyl group, or C$_{1 }$ -Cs  alkoxy group, R$_{2 }$ and R$_{3 }$ are  respectively a linear or branched C$_{1 }$-C$_{20 }$alkyl group, an aryl  group, a linear or branched C$_{1 }$-C$_{20 }$ perfluoroalkyl group, a  benzyl group, or a  CcC$_{20 }$ aryl group, R$_{4}$ ,  Rs and R$_{6 }$ are  respectively a hydrogen atom, or a C$_{1 }$-C$_{30 }$alkyl group includ› ing or not including an ether group, an ester group, a carbonyl  group, an acetal group, an epoxy group, a nitrile group, or an  aldehyde group, R$_{7}$ ,  R$_{8 }$ and R$_{9 }$ are respectively a hydrogen  atom, a methyl group, or a trifluoromethyl group, X$_{2 }$is olefin,  vinyl, styrene, or a derivative thereof, a, b, c, d, and e respec- tively satisfy 0.0l~a/(a+b+c+d+e)<0.4; 0.01 <b/(a+b+c+d+  e)<0.3;  0.01 <c/(a+b+c+d+e)<0.3;  0.01 ~d/(a+b+c+d+e)  <0.3; 0.0l~e/(a+b+c+d+e)<0.15, and A- is a compound  represented as  solution polymerization, suspension polymerization, bulk› suspension polymerization, emulsion polymerization, and  the like. As a polymerization solvent, at least one polymer- ization solvent selected from benzene, toluene, xylene, halo› genated benzene, diethyl ether, tetrahydrofuran, 1,2-dichlo› roethane, esters, ethers, lactones, ketones, and amides may be  used. Non-reaction monomer and by-products remaining in a  reaction mixture may be preferably removed by a precipita› tion method performed by means of a solvent, after the poly- merization is completed.  An amount of the PAG upon the polymerization of the  copolymer may rely on an amount of a total solid of the  chemically amplified resist composition including the  copolymer. Specifically, the copolymer may perform the  polymerization using the PAG of about 0.5 to 15 parts by  weight with respect to about 100 parts by weight of the total  solid of the chemically amplified resist composition. When  the amount of the PAG is about 0.5 parts by weight or less  with respect to about 100 parts by weight of the total solid of  the composition, acid generation may be reduced to thereby  reduce a resolution, and a resist pattern including a bottom  layer may be not properly generated, that is, formed to be  inclined, and when the amount of the PAG is about 15 parts by  weight or more with respect to about 100 parts by weight of  the same, the acid generation may overly occur to thereby  increase in a thickness loss of an upper portion of the resist  layer, and a light absorption of the PAG may increase to  thereby reduce a transparence of a resin.  A weight-average molecular weight in terms of polysty› rene measured by gel permeation chromatography (GPC) of  the copolymer may be about 500 to 100,000. More specifi- cally, the weight-average molecular weight may be about  3,000 to 30,000 considering coating property of the chemi› cally amplified resist composition, developing property and  heat resistance of the resist layer. When the weight-average  molecular weight is about 500 or less, the resist pattern may  be easily destroyed or deformed, and when the weight-aver› age molecular weight exceeds about 100,000, the resolution  of the resist pattern may be reduced. The molecular weight  distribution of the copolymer may be about 0.9 to 5, and more  particularly, about 1 to 3. The molecular weight distribution  of the copolymer may be appropriately adjusted by changing  a used amount and reaction time of a radical polymerization  initiator.  As examples of the copolymer according to an exemplary  embodiment of the invention, copolymers represented as  Chemical formulas 9 to 21 may be given, and the present  exemplary embodiments are not limited thereto.  The copolymer may be a block copolymer, a random  copolymer, or a graft copolymer. The copolymer may be  synthesized by a polymerization of monomers including the  PAG, and a method of the polymerization is not particularly  limited, however, for example, a radical polymerization may  be used. As a polymerization initiator of the radical polymer› ization, azobisisobutyronitrile (AIBN), benzoyl peroxide  (BPO), lauryl peroxide, azobisisocapronitrile, azobisisovale› ronitrile, tert-butyl hydroperoxide, and the like may be used  alone or in a combination of two or more thereof. A polymer› ization reaction may be performed by an arbitrary polymer› ization reaction selected from among bulk polymerization,  wherein X$_{1 }$ is a monocyclic or polycyclic C$_{3}$ -C$_{20 }$hydro› carbon group, a benzyl group, a C$_{6}$-C$_{20 }$aryl group, a C$_{1 }$-C$_{10 }$ alkyl group, a C$_{1 }$-C$_{10 }$alkoxy group, a C$_{1 }$-C$_{10 }$hydroxy alkyl  group, or a cyano group, at least one hydrogen atom of the  monocyclic or polycyclic C$_{3}$ -C$_{20 }$hydrocarbon group is or is  not substituted with an ether group, an ester group, a carbonyl  group, an acetal group, a nitrile group, a cyano group, a  hydroxy group, a carboxyl group, or an aldehyde group, R is  a C$_{1 }$-C$_{10 }$alkyl group, aC$_{1 }$-C$_{10 }$alkoxy group, a nitrogen atom,  a sulfur atom, or an oxygen atom, and mis a positive integer  ofO to 2.  0  0  II  F2  H2  II  _o-s-c -c -O___JL__(R)m-X1,  II  0  [Chemical formula 2]  [Chemical formula 9] 