US 10,007,180 B2  20  19  with a bulky structure having at least 7 carbon atoms, such  as a norbomyl group, a tricyclodecanyl group, a tetracyclo› decanyl group, a tetracyclododecanyl group and an adaman› tyl group, are preferred from the viewpoint of inhibition of  any in-film diffusion in the PEB (post-exposure bake) opera- tion and enhancement of MEEF (Mask Error Enhancement  Factor).  other substituent containing a fluorine atom can be, for  example, an alkyl group substituted with at least one fluorine  atom.  Further, these alkyl group, cycloalkyl group and aryl  The aryl group may be monocyclic or polycyclic. As the  aryl group, there can be mentioned, for example, a phenyl  group, a naphthyl group, a phenanthryl group or an anthryl  group. Of these, a naphthyl group exhibiting a relatively low  light absorbance at 193 nm is preferred.  The heterocyclic group may be monocyclic or polycyclic.  The polycyclic structure is superior in the inhibition of any  acid diffusion.  It  is optional for the heterocyclic group to  have aromaticity. As the heterocycle having aromaticity,  there can be mentioned, for example, a furan ring, a thio› phene ring, a benzofuran ring, a benzothiophene ring, a  dibenzofuran ring, a dibenzothiophene ring or a pyridine  ring. As the heterocycle having no aromaticity, there can be  mentioned, for example, a tetrahydropyran ring, a lactone  ring or a decahydroisoquinoline ring.  It  is especially pre› ferred for the heterocycle in the heterocyclic group to be a  furan ring, a thiophene ring, a pyridine ring or a decahy- droisoquinoline ring. As examples of the lactone rings, there  can be mentioned those set forth above by way of example  in connection with  RA  and  RB  in general formula (N-1).  A substituent may be introduced in the above cyclic  organic group. As the substituent, there can be mentioned,  for example, an alkyl group, a cycloalkyl group, an aryl  group, a hydroxyl group, an alkoxy group, an ester group, an  amido group, a urethane group, a ureido group, a thioether  group, a sulfonamido group or a sulfonic ester group. The  alkyl group may be in the form of a linear or branched chain.  It  is preferred for the alkyl group to have 1 to 12 carbon  atoms. The cycloalkyl group may be monocyclic or poly› cyclic.  It  is preferred for the cycloalkyl group to have 3 to  12 carbon atoms. The aryl group preferably has 6 to 14  carbon atoms.  In the formula, x is preferably 1 to 8, more preferably 1  to 4 and most preferably 1; y is preferably  O  to 4, more  preferably  O; and z is preferably O to 8, more preferably O to  4.  Also, the nonnucleophilic anion is preferably expressed  by, for example, general formula (LD2) below.  (LD2)  group may further be substituted with a substituent contain› ing no fluorine atom. As this substituent, there can be  mentioned, for example, any of those mentioned above with  respect to Cy wherein no fluorine atom is contained.  As the alkyl group containing at least one fluorine atom  represented by Rf, there can be mentioned, for example, any  of those mentioned hereinbefore as the alkyl group substi› tuted with at least one fluorine atom, represented by Xf. As  the cycloalkyl group containing at least one fluorine atom  represented by Rf, there can be mentioned, for example, a  perfluorocyclopentyl group or a perfluorocyclohexyl group.  As the aryl group containing at least one fluorine atom  represented by Rf, there can be mentioned, for example, a  perfluorophenyl group.  As a preferred form of the anion moiety of compound (A),  there can be mentioned any of structures to be set forth  hereinafter as examples of preferred anion structures of  photoacid generator (B), other than the above structures of  general formulae (LDl) and (LD2).  In compound (A), the fluorine content expressed by (sum  of the masses of all fluorine atoms contained in the com› pound)/(sum of the masses of all atoms contained in the  compound) is preferably 0.30 or less, more preferably 0.25  or less, further more preferably 0.20 or less, still further  preferably 0.15 or less and most preferably 0.10 or less.  Nonlimiting specific examples of compounds (A) are  shown below.  In general formula (LD2), Xf, Ri, R$_{2}$ ,  L, Cy, x, y and z are 55  as defined above in connection with general formula (LDl).  Rf is a group containing a fluorine atom.  As the group containing a fluorine atom represented by  Rf, there can be mentioned, for example, an alkyl group  containing at least one fluorine atom, a cycloalkyl group  containing at least one fluorine atom or an aryl group  containing at least one fluorine atom.  These alkyl group, cycloalkyl group and aryl group may  be substituted with a fluorine atom, or may be substituted  with another substituent containing a fluorine atom. When  Rf is a cycloalkyl group containing at least one fluorine atom  or an aryl group containing at least one fluorine atom, the  )~--O  0 "frF  OiG  0-S  II  F  0  0  0~ 0 -0--"--0  0  0  Xf  R1  II  0  II  I  I  0  Rf-S-N-S---f-C7xf-C-J:j;-i-Ltz-Cy  II  II  I  I  0  OXf  R2 