Dec. 3, 2020  75  US 2020/0379345 Al  equal to 1, B is an integer of 2 to 25, and C is an integer of  0 to 10. Preferably, Bis an integer of 4 to 20, and C is  O  or  1. Note that the above structural formula does not prescribe  the arrangement of respective constituent units while they  may be arranged either blockwise or randomly. For the  preparation of surfactants in the form of partially fluorinated  oxetane ring-opened polymers, reference should be made to  U.S. Pat. No. 5,650,483, for example.  [0102]  The surfactant which is insoluble or substantially  insoluble in water and soluble in alkaline developer is useful  when ArF immersion lithography is applied to the resist  composition in the absence of a resist protective film. In this  embodiment, the surfactant has a propensity to segregate on  the resist film surface for achieving a function of minimizing  water penetration or leaching. The surfactant is also effective  for  preventing water-soluble components from being  leached out of the resist film for minimizing any damage to  the exposure tool. The surfactant becomes solubilized dur› ing alkaline development following exposure and PEB, and  thus forms few or no foreign particles which become  defects. The preferred surfactant is a polymeric surfactant  which is insoluble or substantially insoluble in water, but  soluble in alkaline developer, also referred to as "hydropho› bic resin" in this sense, and especially which is water  repellent and enhances water slippage.  [0103]  Suitable polymeric surfactants include those con› taining recurring units of at least one type selected from the  formulae (IA) to (IE).  [0104]  Herein,  RA  is hydrogen, fluorine, methyl or trifluo› romethyl. W 1  is ----CH$_{2}$-, ----CH$_{2}$CH$_{2}$ - or ---0-, or two  separate -H.  Rs 1  is each independently hydrogen or a  C$_{1 }$-C$_{10 }$monovalent hydrocarbon group. Rs 2  is a single bond  or a C$_{1 }$-C$_{5 }$ straight or branched divalent hydrocarbon group.  Rs 3  is each independently hydrogen, a C$_{1 }$-C$_{15 }$ monovalent  hydrocarbon or fluorinated hydrocarbon group, or an acid  labile group. When  Rs 3  is a monovalent hydrocarbon or  fluorinated hydrocarbon group, an ether bond  (-0-)  or  carbonyl moiety (----C(=O)-) may intervene in a carbon› carbon bond. R5 4  is a C$_{1}$-C$_{20 }$ (u+l)-valent hydrocarbon or  fluorinated hydrocarbon group, and u is an integer of 1 to 3.  R5 5  is each independently hydrogen or a group having the  formula.  -----C(=0)---0-R’a  wherein  Rsa  is a C$_{1 }$-C$_{20 }$fluorinated hydrocarbon group. Rs 6  is a C-Cis monovalent hydrocarbon or fluorinated hydrocar› bon group in which an ether bond (---0-) or carbonyl  moiety (----C(=O)-) may intervene in a ca-carbon bond.  [0105]  The monovalent hydrocarbon group represented by  Rs $^{1 }$may be straight, branched or cyclic and examples thereof  include methyl, ethyl, n-propyl, isopropyl, cyclopropyl,  n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl,  cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl,  n-decyl, adamantyl, and norbornyl. Inter alia, C$_{1 }$-C$_{6 }$ hydro› carbon groups are preferred.  [0106]  The divalent hydrocarbon group represented by R5 2  may be straight, branched or cyclic and examples thereof  include methylene, ethylene, propylene, butylene, and pen› tylene.  [0107]  The monovalent hydrocarbon group represented by  Rs 3  or Rs$^{6 }$may be straight, branched or cyclic and examples  thereof include alkyl, alkenyl, and alkynyl groups, with the  alkyl groups being preferred. Suitable alkyl groups include  those exemplified for the monovalent hydrocarbon group  represented by  Rs $^{1 }$as well as n-undecyl, n-dodecyl, tridecyl,  tetradecyl, and pentadecyl. Examples of the monovalent  fluorinated hydrocarbon group represented by  Rs 3  or Rs 6  include the foregoing monovalent hydrocarbon groups in  which some or all carbon-bonded hydrogen atoms are sub› stituted by fluorine atoms. In these groups, an ether bond  -continued  (lD)  (lE)  (lA)  (lB)  (lC) 