US 2020/0401045 Al  13  Dec. 24, 2020  [0219]  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), and these groups preferably have 8 or less carbon  atoms.  [0208]  In Formula (Y3), R$_{36 }$ to R$_{38 }$ each independently  represent a hydrogen atom or a monovalent organic group.  [0212]  In General Formula (All),  [0200]  In Formulae (Yl) and (Y2), Rx$_{1 }$ to Rx$_{3 }$ each  independently represent an (linear or branched) alkyl group  or a (monocyclic or polycyclic) cycloalkyl group.  It  should  be noted that in a case where all ofRx$_{1 }$ to Rx$_{3 }$ are (linear or  branched) alkyl groups, it is preferable that at least two of  Rxi, ... , or Rx$_{3 }$ are methyl groups.  [0211]  As the repeating unit having a structure in which  the phenolic hydroxyl group is protected by a leaving group  that leaves through decomposition by the action of an acid,  a repeating unit represented by General Formula (All) is  preferable.  [0210]  The repeating unit having a structure (acid-decom› posable group) in which a phenolic hydroxyl group is  protected by a leaving group that leaves through decompo› sition by the action of an acid preferably has a structure in  which a hydrogen atom in the phenolic hydroxyl group is  protected by a group represented by any of Formulae (Yl)  to (Y4).  [0209]  In Formula (Y4), Ar represents an aromatic hydro› carbon group. Rn represents an alkyl group, a cycloalkyl  group, or an aryl group.  Rn and Ar may be bonded to each  other to form a non-aromatic ring. Ar is more preferably an  aryl group.  R$_{37 }$ and R$_{38 }$ may be bonded to each other to form a ring.  Examples of the monovalent organic group include an alkyl  group, a cycloalkyl group, an aryl group, an aralkyl group,  and an alkenyl group. R$_{36 }$ is preferably a hydrogen atom.  (All)  [0197]  •  Repeating Unit Having Structure (Acid-Decom› posable Group) in which Phenolic Hydroxyl Group is Pro› tected by Leaving Group that Leaves Through Decomposi› tion by Action of Acid  [0198]  In the present specification, the phenolic hydroxyl  group is a group obtained by substituting a hydrogen atom  of an aromatic hydrocarbon group with a hydroxyl group.  The aromatic ring of the aromatic hydrocarbon group is a  monocyclic or polycyclic aromatic ring, and examples  thereof include a benzene ring and a naphthalene ring.  [0199]  Examples of the leaving group that leaves through  decomposition by the action of an acid include groups  represented by Formulae (Yl) to (Y4).  Formula (Yl):  Formula (Y2):  Formula (Y3):  Formula (Y4):  -C(=O)OC(Rx$_{1}$)(Rx$_{2}$)(Rx$_{3}$ )  -C(Rn)(H)(Ar)  [0218]  n represents an integer of  1  to 4.  [0217]  Y/s each independently represent a hydrogen  atom or a group that leaves by the action of an acid in  a case of n2:2.  It  should be noted that at least one ofY/s  represents a group that leaves by the action of an acid.  The group that leaves by the action of an acid as Y2 is  preferably any of Formulae (Yl) to (Y4).  [0216]  Ar$_{6 }$ represents an (n+l)-valent aromatic hydro› carbon group, and in a case of being bonded to R $^{62 }$to  form a ring, Ar represents an (n+2)-valent aromatic  hydrocarbon group.  [0215]  L$_{6 }$represents a single bond or an alkylene group.  [0214]  X$_{6 }$ represents a single bond, -COO-, or  ----CONR$_{64}$-. R$_{64 }$represents a hydrogen atom or an  alkyl group.  [0213]  R$_{61}$, R 62 , and R $_{63 }$each independently represent  a hydrogen atom, an alkyl group, a cycloalkyl group, a  halogen atom, a cyano group, or an alkoxycarbonyl  group.  It  should be noted that R$_{62 }$may be bonded to Ar$_{6 }$ to form a ring, and in this case, R$_{62 }$represents a single  bond or an alkylene group.  [0207]  For the group represented by each of Formulae  (Yl) and (Y2), for example, an aspect 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 above-mentioned  cycloalkyl group is preferable.  [0206]  In the cycloalkyl group formed by the bonding  of two ofRx$_{1 }$to Rx$_{3}$ ,  for example, one of the methylene  groups constituting the ring may be substituted with a  heteroatom such as an oxygen atom, or a group having  a heteroatom, such as a carbonyl group.  [0205]  As the cycloalkyl group formed by the bonding  of two of Rx$_{1 }$ to Rx$_{3}$ ,  a monocyclic cycloalkyl group  such as a cyclopentyl group and a cyclohexyl group, or  a polycyclic cycloalkyl group such as a norbomyl  group, a tetracyclodecanyl group, a tetracyclododeca› nyl group, and an adamantyl group is preferable.  Among those, a monocyclic cycloalkyl group having 5  or 6 carbon atoms is more preferable.  [0204]  As the cycloalkyl group of each of Rx$_{1 }$ to Rx$_{3}$ ,  a monocyclic cycloalkyl group such as a cyclopentyl  group and a cyclohexyl group, or a polycyclic cycloal› kyl group such as a norbomyl group, a tetracyclode› canyl group, a tetracyclododecanyl group, and an ada› mantyl group is preferable.  [0203]  As the alkyl group of each 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 a t-butyl group, is preferable.  [0202]  Two ofRx$_{1 }$ to Rx$_{3 }$ may be bonded to each other  to form a monocycle or a polycycle.  [0201]  Among those, Rx$_{1 }$ to Rx$_{3 }$ are more preferably  each independently a repeating unit which represents a  linear or branched alkyl group, and Rx$_{1 }$ to Rx$_{3 }$ are still  more preferably each independently a repeating unit  which represents a linear alkyl group. 