Acid Labile Crosslinked Units: A new Concept for Deep-UV Photoresists.

New Polymers with Acid Labile Crosslinked Units and their Performance in Deep-UV Photoresists

“…Recently we reported [20], that the reaction of poly-[4-hydroxystyrene/4-vinylcyclohexanol] (PHSVC) with vinylether in the presence of an acidic catalyst leads to polymers with a strong increase of the weight average molecular weight (MW) and polydispersivity (MW/M"). This increase can be explained by a transacetalization reaction [20][21][22], which forms acetal links of type A and B (Figure 1) between the polymer chains.…”

“…This increase can be explained by a transacetalization reaction [20][21][22], which forms acetal links of type A and B (Figure 1) between the polymer chains. MW and polydispersivity are controlled by the amount of the cyclohexanol units because a possible link between two aromatic units (C in Figure 1) was not observed under the applied reaction conditions.…”

“…For the comparison of the different crosslinked and linear acetal protected polymers, we define the crosslinking degree X [20]: X = [M(cross)/M(lin)] wW-1 MW(cross) is the weight average molecular weight of the crosslinked polymer, whereas MW(lin) is the weight average molecular weight of the corresponding linear polymer with the same acetal blocking level under the provision that MW before the acetalization reactions is the same for both. Figure 3 shows the correlation between the feed of the bifunctional alcohol and the crosslinking level.…”

“…In our earlier paper [20] we described that the crosslinked polymer systems show an improved resolution with increase of the molecular weight. This is in opposition to the general experience with backbones with high molecular weight used in resist systems [23].…”

“…These resins however suffer from reduced plasma etch stability. A better possibility to increase the thermal properties of the polymeric binder is to increase the molecular weight via acid labile crosslinked units [20].…”