US 9,097,971 B2  146  145  -continued  -continued  As the structural unit (a2L), it is preferable to use at least  one structural unit selected from the group consisting of  structural units represented by the aforementioned general  formulas ( a2-1) to ( a2-5), more preferably at least one struc› tural unit selected from the group consisting of structural  units represented by the aforementioned general formulas  (a2-1) to (a2-3), and most preferably at least one structural  unit selected from the group consisting of structural units  represented by the aforementioned general formulas (a2-1)  and (a2-3).  Specifically, it is preferable to use at least one structural  unit selected from the group consisting of formulas (a2-l-1)  (a2-l-2) (a2-2-1 ), (a2-2-7), (a2-2-12), (a2-2-14), (a2-3-l) and  (a2-3-5).  Further, as the structural unit (a2L), a structural unit repre› sented by formula (a2-6) or (a2-7) shown below is also pref- erable.  [Chemical Formula 69]  These aliphatic cyclic groups (monocyclic groups and  polycyclic groups) can be selected appropriately from the  multitude of groups that have been proposed for the resins of  Examples of the aliphatic hydrocarbon group as the hydro› carbon group include linear or branched hydrocarbon groups  (preferably alkylene groups) of 1 to 10 carbon atoms, and  aliphatic cyclic groups (monocyclic groups and polycyclic  groups).  The structural unit (a3) is preferably a structural unit con- taining a hydrocarbon group in which part of the hydrogen  atoms has been substituted with a polar group. The hydrocar› bon group may be either an aliphatic hydrocarbon group or an  aromatic hydrocarbon group. Among these, as the hydrocar- bon group, an aliphatic hydrocarbon group is preferable.  Examples of the polar group include -OH, -COOH,  ----CN, -SO$_{2}$NH$_{2}$ ,  ----CONH$_{2 }$ and a hydroxyalkyl group in  which part of the hydrogen atoms of an alkyl group have been  substituted with fluorine atoms. Of these, -OH is preferable.  The structural unit (a3) is preferably a structural unit (a3- 12-21) derived from an acrylate ester which may have the  hydrogen atom bonded to the carbon atom on the a-position  substituted with a substituent and contains a polar group› containing aliphatic hydrocarbon group.  The structural unit (a3) is a structural unit containing a  polar group. When the polymeric compound includes the  structural unit (a3), the hydrophilicity of the polymeric com› pound is enhanced, thereby contributing to improvement in  resolution.  When the amount of the structural unit (a2) is at least as  large as the lower limit of the above-mentioned range, the  effect of using the structural unit (a2) can be satisfactorily  achieved. On the other hand, when the amount of the struc› tural unit (a2) is no more than the upper limit of the above› mentioned range, a good balance can be achieved with the  other structural units, and various lithography properties such  as DOF and CDU and pattern shape can be improved.  In the polymeric compound (Al) or (Al’), the amount of  the structural unit (a2) based on the combined total of all  structural units constituting the polymeric compound (Al) or  (Al’) is preferably 1 to 80 mo! %, more preferably 10 to 70  mo! %, still more preferably 10 to 65 mo! %, and most  preferably 10 to 60 mo! %.  Further, as the structural unit (a2s) or the structural unit  (a2L), either a single type of structural unit may be used, or  two or more types may be used in combination.  In the polymeric compounds (Al) and (Al’), as the struc› tural unit (a2), one type of structural unit may be used, or two  or more types may be used in combination. For example, as  the structural unit (a2), a structural unit (a2s) may be used  alone, or a structural unit (a2L), or a combination of these  structural units may be used.  In the formulae, Rand R$^{29 }$are the same as defined above.  (a2-5-6)  (a2-7)  (a2-6)  (Structural Unit (a3)) 