Nov.  22, 2018  43  US 2018/0335696 Al  0  0  [0060]  When the polymer-bound acid generator also func› tions as a base polymer, the polymer may further comprise  recurring units (f) derived from indane, vinylpyridine or  vinylcarbazole.  [0061]  In a further embodiment, the polymer-bound acid  generator may further comprise recurring units (g) derived  from an onium salt having a polymerizable unsaturated bond  other than the recurring units (al) and (a2). Typical recurring  units (g) are described, for example, in U.S. Pat. No.  9,810,983 (JP-A 2017-008181, paragraph [0060]).  [0062]  The base polymer for formulating the positive  resist composition comprises recurring units (al) and/or (a2)  and recurring units (bl) and/or (b2) having an acid labile  group as essential components and additional recurring units  ( c ), ( d), ( e ), (f) and (g) as optional components. A fraction of  units (al), (a2), (bl), (b2), (c), (d), (e), (f), and (g) is:  preferably 0sal <1.0, 0sa2<1.0, 0<al +a2<1.0, 0sbl <1.0,  0sb2<1.0,  0<bl+b2<1.0,  0scs0.9,  0sds0.9, 0ses0.8,  0<f<0.8, and 0sgs0.4; more preferably 0sals0.7, 0sa2s0.7,  0.02sal+a2s0.7,  0sbls0.9, 0sb2s0.9, 0.lsbl+b2s0.9,  0scs0.8, 0sds0.8, 0ses0.7, 0sfs0.7, and 0sgs0.3; and even  more preferably 0sal s0.5, 0sa2s0.5, 0.03sal +a2s0.5,  [0058]  In the case of a monomer having a hydroxyl group,  the hydroxyl group may be replaced by an acetal group  susceptible to deprotection with acid, typically ethoxy› ethoxy, prior to polymerization, and the polymerization be  followed by deprotection with weak acid and water. Alter› natively, the hydroxyl group may be replaced by an acetyl,  formyl, pivaloyl or similar group prior to polymerization,  and the polymerization be followed by alkaline hydrolysis.  [0059]  When the polymer-bound acid generator also func› tions as a base polymer, the polymer may further comprise  recurring units ( e) derived from indene, benzofuran, benzo› thiophene, acenaphthylene, chromone, coumarin, and nor› bomadiene, or derivatives thereof. Suitable monomers are  exemplified below.  -continued 