Dec. 3, 2020  5  US 2020/0379345 Al  mantyl, and adamantylmethyl, and aryl groups such as  phenyl, naphthyl and anthracenyl. Examples of the monova› lent fluorinated hydrocarbon group include the foregoing  monovalent hydrocarbon groups in which some or all hydro› gen atoms are substituted by fluorine atoms.  [0053]  In the monovalent hydrocarbon group or monova› lent fluorinated hydrocarbon group, some hydrogen may be  substituted by a moiety containing a heteroatom such as  oxygen, sulfur, nitrogen, chlorine, bromine or iodine, or  some carbon may be replaced by a moiety containing a  heteroatom such as oxygen, sulfur or nitrogen, so that the  group may contain a hydroxyl, cyano, carbonyl, ether bond,  ester bond, sulfonate bond, carbonate bond, carbamate bond,  amide bond, imide bond, lactone ring, sultone ring, thiolac› tone ring, lactam ring, sultam ring, carboxylic anhydride  (-C(=O)-O----C(=O)-), or haloalkyl moiety. It is noted  that any carbon atom in R bonded to a carbon atom on the  phenyl group in formula (A) may be replaced by the  heteroatom-containing moiety.  [0054]  When a is 2 or more (i.e., a;;,;2), R $^{1 }$may be identical  or different and two R  1  may bond together to form a ring  with the atoms to which they are attached. Examples of the  ring thus formed include cyclopropane, cyclobutane, cyclo› pentane, cyclohexane, norbornane and adamantane rings.  [0055]  The monovalent hydrocarbon group which may  contain a heteroatom other than fluorine or the monovalent  fluorinated hydrocarbon group which may contain a het› eroatom other than fluorine, represented by R  1, may be an  acid labile group of acetal form. The preferred acid labile  group of acetal form has the following formula (A’).  [0058]  In formula (A’),  Ra  is hydrogen or a C$_{1 }$-C$_{20 }$mon› ovalent hydrocarbon group which may contain a heteroa› tom. The monovalent hydrocarbon group may be straight,  branched or cyclic. Examples include alkyl groups such as  methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert› butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-de› cyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, cyclopentylm› ethyl,  cyclopentylethyl,  cyclopentylbutyl,  cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, nor› bomyl, tricyclo[5.2.l.0 2 • $^{6}$]decanyl, adamantyl, and adaman› tylmethyl, and aryl groups such as phenyl, naphthyl and  anthracenyl. In the monovalent hydrocarbon group, some  hydrogen may be substituted by a moiety containing a  heteroatom such as oxygen, sulfur, nitrogen or halogen, or a  [0051]  Of these,  XL-1  to  XL-22  and  XL_47  to  XL_49  are  more preferred, with  XL-1  to  XL-17  being most preferred.  [0052]  In formula (A), R$^{1 }$is a C$_{3}$ -C$_{40 }$monovalent hydro› carbon group which may contain a heteroatom other than  fluorine or a C$_{1 }$-C$_{40 }$ monovalent fluorinated hydrocarbon  group which may contain a heteroatom other than fluorine.  The monovalent hydrocarbon group may be straight,  branched or cyclic. Examples include alkyl groups such as  n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-pen› tyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl,  cyclohexyl, 2-ethylhexyl, cyclopentylmethyl, cyclopentyl› ethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl,  cyclohexylbutyl, norbomyl, tricyclo[5.2.l.0 2 • $^{6}$]decanyl, ada- (A’)  (\7  •-- s --•  l_____V  -continued  [0056]  In formula (A’), L 3  and L  4  are each independently  a single bond, ether bond, ester bond, sulfonate bond,  carbonate bond or carbamate bond. L $^{3 }$is preferably a single  bond, ether bond, or ester bond, more preferably a single  bond. L  $^{4 }$is preferably a single bond, ether bond, or ester  bond, more preferably a single bond.  [0057]  In formula (A’),  XL2  is a single bond or a C$_{1 }$-C$_{40 }$ divalent hydrocarbon group which may contain a heteroa› tom. Examples of the optionally heteroatom-containing  C$_{1 }$-C$_{40 }$divalent hydrocarbon group  XL2  include the forego› ing  XL-1  to  XL-49. XL2  is preferably a single bond. 