US 2016/0223905 Al  3  Aug. 4, 2016  [0052]  Preferred examples of the alkali-soluble group  include a carboxyl group, a fluorinated alcohol group (pref› erably a hexafluoroisopropanol group), and a sulfonic acid  group.  [0053]  The group which is preferable as the acid-decom› posable group is a group in which a hydrogen atom of the  alkali-soluble group is substituted with a group capable of  leaving by an acid.  [0054]  Examples of the group capable ofleaving by an acid  include -C(R 36 )(R 37 )(R 38 ),  ----C(R 36 )(R 37 )(OR 39 ),  and  -CCR01)CR02)(OR39)- [0066]  Tis preferably a single bond or a-COO-Rt- group.  Rtis preferably analkylene group having 1 to 5 carbon atoms,  and more preferably a ----CH 2 - group, a -(CH 2 ) 2 - group,  or a -(CH 2 ) 3 - group.  [0067]  As the alkyl group of Rx 1  to Rx 3 , an alkyl group  having 1 to 4 carbon atoms, such as a methyl group, an ethyl  group, an n-propyl group, an isopropyl group, an n-butyl  group, an isobutyl group, and at-butyl group is preferable.  [0068]  As the cycloalkyl group ofRx 1  to Rx 3 , a monocyclic  cycloalkyl group such as a cyclopentyl group and a cyclo› hexyl group, and a polycyclic cycloalkyl group such as a  norbornyl group, a tetracyclodecanyl group, a tetracy› clododecanyl group, and an adamantyl group are preferable.  [0055]  In the formulae, R 36  to R 39  each independently rep› resent an alkyl group, a cycloalkyl group, an aryl group, an  aralkyl group, or an alkenyl group. R 36  and R 37  may be  bonded to each other to form a ring.  [0056]  R 01  to R 02  each independently represent a hydrogen  atom, an alkyl group, a cycloalkyl group, an aryl group, an  aralkyl group, or an alkenyl group.  [0057]  The acid-decomposable group is preferably a cumyl  ester group, an enol ester group, an acetal ester group, a  tertiary alkyl ester group, or the like, and more preferably a  tertiary alkyl ester group.  [0069]  As the cycloalkyl group formed by the mutual bond› ing of two members ofRx 1  to Rx 3 , a monocyclic cycloalkyl  group such as a cyclopentyl group and a cyclohexyl group,  and a polycyclic cycloalkyl group such as a norbornyl group,  a tetracyclodecanyl group, a tetracyclododecanyl group, and  an adamantyl group are preferable, and a monocyclic  cycloalkyl group having 5 or  6  carbon atoms is particularly  preferable.  [0070]  In the cycloalkyl group formed by the mutual bond› ing of two members ofRx 1  to Rx 3 , for example, one of the  methylene groups constituting the ring may be substituted  with a hetero atom such as an oxygen atom, or with a group  having a hetero atom, such as a carbonyl group.  [0058]  Furthermore, a repeating unit represented by the  following General Formula (AI) is preferable as the repeating  unit having an acid-decomposable group, which can be con› tained in the resin (A).  (Al)  [0071]  An aspect of the repeating unit represented by Gen› eral Formula (AI), for example, in which Rx 1  is a methyl  group or an ethyl group, and Rx 2  and Rx 3  are bonded to each  other to form the afore-mentioned cycloalkyl group, is pref› erable.  [0072]  Each of the groups may have a substituent, and  examples of the substituent include an alkyl group (having 1  to 4 carbon atoms), a halogen atom, a hydroxyl group, an  alkoxy group (having 1 to 4 carbon atoms), a carboxyl group,  and an alkoxycarbonyl group (having  2 to 6 carbon atoms),  with those having  8  or less carbon atoms being preferable.  [0059]  In General Formula (AI),  [0060]  Xa 1  represents a hydrogen atom, or an alkyl group  which may have a substituent,  [0061]  T represents a single bond or a divalent linking  group,  [0062]  Rx 1  to Rx 3  each independently represent an (linear  or branched) alkyl group or a (monocyclic or polycyclic)  cycloalkyl group, and  [0073]  The total content of the repeating unit having an  acid-decomposable group is preferably 20% by mole to 90%  by mole, more preferably 25% by mole to 85% by mole, and  still more preferably 30% by mole to 80% by mole, with  respect to all the repeating units in the resin (A).  [0074]  Specific preferred examples of the repeating unit  having an acid-decomposable group are set forth below, but  the present invention is not limited thereto.  [0075]  In the specific examples, Rx and Xa 1  each represent  a hydrogen atom, CH 3 , CF 3 , or CH 2 OH. Rxa and Rxb each  represent a an alkyl group having 1 to 4 carbon atoms. Z  represents a substituent containing a polar group, and in the  case where Z’s are present in plural numbers, they are each  independent. p represents  O  or a positive integer. Examples of  the substituent containing a polar group, represented by Z,  include a linear or branched alkyl group, and a cycloalkyl  group, each having a hydroxyl group, a cyano group, an  amino group, an alkylamide group, or a sulfonamide group,  and preferably an alkyl group having a hydroxyl group.As the  branched alkyl group, an isopropyl group is particularly pref› erable.  [0063]  two members out of Rx 1  to Rx 3  may be bonded to  each other to form a (monocyclic or polycyclic) cycloalkyl  group.  [0064]  Examples of the alkyl group which may have a  substituent, represented by Xa 1 , include a methyl group or a  group represented by ----CH 2 -R$_{11}$. R$_{11 }$represents a halogen  atom (a fluorine atom or the like), a hydroxyl group, or a  monovalent organic group, and examples thereof include an  alkyl group having 5 or less carbon atoms, and an acyl group  having 5 or less carbon atoms, preferably an alkyl group  having  3  or less carbon atoms, and more preferably a methyl  group. In one aspect, Xa 1  is preferably a hydrogen atom, a  methyl group, a trifluoromethyl group, a hydroxymethyl  group, or the like.  [0065]  Examples of the divalent linking group ofT include  an alky lene group, a -COO-Rt- group, and an ---0 Rt- group.  In the formulae, Rt represents an alkylene group or a  cycloalkylene group. 