US 9,152,050 B2  8  7  polymer comprises recurring units derived from HFA sty› rene, that is, has fluorine-containing recurring units, it will  segregate on the surface of the resist film after spin coating.  Because of its robustness and high density, HFA styrene is  effective for shutting off outgassing from the photoresist film.  Since the polymer comprises recurring units ofHFA styrene  dissolves in an alkaline developer, it is also effective for  reducing bridge defects between resist pattern features after  development.  Polymeric Additive  One embodiment of the invention is a resist composition  comprising a polymer capable of increasing alkali solubility  under the action ofacid, serving as a base resin, and a polymer  comprising recurring units derived from HFA styrene, serv- ing as a polymeric additive. Typically, the polymer serving as  polymeric additive comprises recurring units having the gen› eral formula (1).  Herein R $^{1 }$is hydrogen, hydroxyl, a C$_{1 }$-C$_{10 }$straight, branched  or cyclic alkyl group, alkoxy group, acyloxy group, cyano  group, nitro group, amino group or halogen atom, mis 1 or 2,  and 0<psl.0.  Preferably, the polymer serving as a polymeric additive is  a polymer comprising recurring units derived from a styrene  having 1,1,1,3,3,3-hexafluoro-2-propanol and optionally,  recurring units (ql) and/or (q2) derived from a monomer  selected from a styrene and vinylnaphthalene, represented by  the general formula (2).  Herein R $^{1 }$is hydrogen, hydroxyl, a C$_{1 }$-C$_{10 }$straight, branched  or cyclic alkyl group, alkoxy group, acyloxy group, cyano  group, nitro group, amino group or halogen atom, and mis 1  or 2. R$^{2 }$andR$^{3 }$each are hydrogen, a C$_{1}$-C$_{6}$ ,  straight, branched  or cyclic alkyl group, alkoxy group, acyl group, acyloxy 60  group, alkoxycarbonyl group, nitro group, cyano group, halo- gen atom, trifluoromethyl group, hydroxyl group or carboxyl  group, v is an integer of 1 to 5, and w is an integer of 1 to 7.  Subscripts p, ql and q2 are numbers in the range: 0<psl.0,  0sq 1 <1.0, and 0sq2<1.0.  65  The resist composition having the polymer comprising  recurring units of formula (1 ), especially formula (2) added  Examples of the monomers from which recurring units  (p)  ofHFA styrene are derived are shown below, but not limited  thereto.  thereto is coated to form a photoresist film. The photoresist  film is characterized in that a polymeric surfactant compris› ing recurring units of HFA styrene and optionally, recurring  units of styrene or vinylnaphthalene is present on the film  surface. The polymeric surfactant segregates on the photore› sist film surface at the end of photoresist coating and func- tions to suppress the release of outgassing components from  the resist film and to minimize defects in the resist pattern  after development.  R’6  (1) R’t  0  ~  ~X:,,1  R2v  R3w  F3C  CF3  HO  OH  F3C  CF3  CF3  CF3  OH  if  OH  CF3  : I  CF3  OH  OH  F3C  F3C  CF3  OH  CF3  OH  CF3  OH  OH  CF3  OH  )nee  OH  CF3  3  HO  HO  OH  CF3  0/  CF3  F3C  CF3  OH  /0  CF3  OH  CF3  OH  CF3  0  I  OH  /0  CF3 