content_image/899657.jpg content_image/899656.jpg
<img src='content_image/899657.jpg'>

The attachment of an acid generator to the polymer main chain is effective in restraining acid diffusion, thereby pre- venting a reduction of resolution due to blur by acid diffu› sion. Also edge roughness is Improved since the acid gen› erator is uniformly distributed. 

The base polymer comprising recurring units (f) also functions as the acid generator. Since this base polymer is integrated with the acid generator, an acid generator of addition type may or may not be added to the chemically amplified resist composition. 

The base polymer for formulating the positive resist composition comprises recurring units (al) or (a2) having an acid labile group as essential component and additional recurring units (b), (c), (d), (e), and (f) as optional compo› nents. A fraction of units (al), (a2), (b), (c), (d), (e), and (f) is: preferably 0sal<l.0, 0sa2<1.0, 0<al+a2<1.0, 0sbs0.9, 0scs0.9, 0sds0.8, 0ses0.8, and 0sfs0.5; more preferably 0sals0.9, 0sa2s0.9, 0.lsal+a2s0.9, 0sbs0.8, 0scs0.8, 0sds0.7, 0scs0.7, and 0sfs0.4; and even more preferably 0sals0.8, 0sa2s0.8, 0.lsal+a2s0.8, 0sbs0.75, 0scs0.75, 0sds0.6, 0ses0.6, and 0sfs0.3. In the embodiment wherein the base polymer also functions as an acid generator, the fraction of recurring units (f) is preferably 0<fs0.5, more preferably 0.Olsfs0.4, and even more preferably 0.02sfs0.3. Notably, f=fl+f2+f3, meaning that unit (f) is at least one of units (fl) to (f3), and al+a2+b+c+d+e+f=l.0. 

For the base polymer for formulating the negative resist composition, an acid labile group is not necessarily essen› tial. The base polymer comprises recurring units (b ), and optionally recurring units (c), (d), (e), and/or (f). A fraction of these units is: preferably 0<bsl.0, 0scs0.9, 0sds0.8, 0ses0.8, and 0sfs0.5; more preferably 0.2sbsl .0, 0scs0.8, 0sds0.7, 0ses0.7, and 0sfs0.4; and even more preferably 0.3sbsl.0, 0scs0.75, 0sds0.6, 0ses0.6, and 0sfs0.3. In the embodiment wherein the base polymer also functions as an acid generator, the fraction of recurring units (f) is preferably 0<fs0.5, more preferably 0.0lsfs0.4, and even more pref› erably 0.02sfs0.3. Notably, f=fl+f2+f3, meaning that unit (f) is at least one of units (fl) to (f3), and b+c+d+e+f=l.0. 

The base polymer may be synthesized by any desired methods, for example, by dissolving one or more monomers selected from the monomers corresponding to the foregoing recurring units in an organic solvent, adding a radical polymerization initiator thereto, and effecting heat polym- 

<img src='content_image/899656.jpg'>

