US 2019/0219920 Al  35  Jul.  18,  2019  [0293]  As the structural unit (a3) contained in the com› ponent (Al), 1 kind of structural unit may be used, or 2 or  more kinds of structural units may be used.  [0294]  When the component (Al) contains the structural  unit (a3), the amount of the structural unit (a3) based on the  combined total (100 mo! %) of all structural units consti› tuting the component (Al) is preferably 1 to 50 mo! %, more  preferably 1 to 40 mo! %, still more preferably 3 to 30 mo!  %, and most preferably 10 to 20 mo! %.  [0295]  When the amount of the structural unit (a3) is at  least as large as the lower limit of the above-mentioned  preferable range, the resolution is improved in the formation  of a resist pattern. On the other hand, when the amount of the  structural unit (a3) is no more than the upper limit of the  above-mentioned preferable range, a good balance can be  reliably achieved with the other structural units.  [0296]  Structural Unit (a4):  [0297]  The component (Al) may be further include, in  addition to the structural unit (a0), a structural unit (a4)  containing an acid non-dissociable, aliphatic cyclic group.  [0298]  When the component (Al) includes the structural  unit (a4),  dry  etching resistance of the resist pattern to be  formed is improved. Further, the hydrophobicity of the  component (A) is further improved. Increase in the hydro› phobicity contributes to improvement in terms of resolution,  shape of the resist pattern and the like, particularly in a  solvent developing process.  [0299]  An "acid non-dissociable, aliphatic cyclic group"  in the structural unit ( a4) refers to a cyclic group which is not  dissociated by the action of the acid ( e.g., acid generated  from a structural unit which generates acid upon exposure or  acid generated from the component (B)) upon exposure, and  remains in the structural unit.  [0300]  As the structural unit (a4), a structural unit which  contains a non-acid-dissociable aliphatic cyclic group, and is  also derived from an acrylate ester is preferable. As the  cyclic group, any of the multitude of conventional polycy› clic groups used within the resin component of resist com› positions for ArF excimer lasers or KrF excimer lasers (and  particularly for ArF excimer lasers) can be used.  [0301]  In consideration of industrial availability and the  like, at least one polycyclic group selected from amongst a  tricyclodecyl group, adamantyl group, tetracyclododecyl  group, isobornyl group, and norbomyl group is particularly  desirable. These polycyclic groups may be substituted with  a linear or branched alkyl group of 1 to 5 carbon atoms.  [0302]  Specific examples of the structural unit (a4) include  structural units represented by general formulae (a4-l) to  (a4-7) shown below.  [Chemical Formula 37]  (a4-1)  (a4-6)  0  (a4-5)  (a4-4)  (a4-3)  (a4-2)  -continued 