Polymer Structural Variation Towards Enhancing KrF Resist Lithographic Properties.

Abstract

Lithographic properties of a variety of acetal-derivatized hydroxy styrene based polymers are reported. The structural modifications in the polymers involve varying the size of the pendent acetal moiety. utilizing a novel transacetalization synthetic procedure. The lithographic performance of the resists containing "bulky" acetal-derivatized polymers was found to be superior to those containing non-bulky acetal functionalized polymers. In the cases where the acidolysis products of the bulky acetal-based polymers are non-volatile alcohols, the post-exposure volatilization, film shrinkage and plasma etch resistance were found to be significantly improved.

Modified Acetal Approach to 157nm Resist Design.

“…As seen with other bulky acetals, this resist only loses a maximum of 1 % of the original film thickness over the dose range studied. The film shrinkage of this "bulky" acetal is insignificant compared to around 11 % film loss for the tertiary-butyl-acetal based resist, as reported earlier [16].…”

“…The acetal-derived polymers were formed by reacting the HSbased polymers with tertiary-butyl vinyl ether (t-BVE) and an alcohol as described previously [16]. The procedure is depicted in Scheme 1:…”

“…One problem with acetal groups, however, is their tendency to outgas during exposure, especially simple acetals based on low molecular weight alcohols. Our previous work on bulky acetal derivatized polyhydroxystyrene (PHS) showed that the level of out-gassing could be significantly reduced by appropriate choice of the blocking group [16,17].…”

Fundamental Studies of the Effects of Photo-additive Structure on Resist Outgassing.

“…However, formulation with sulfonium salts better suppresses the formation of t-butylbenzene and the unknown Figure 6A). Also tested was a sample of a similar polyhydroxystyrene derived material protected with "bulky acetal" ( Figure 6B) which has shown lower volume loss during exposure [9].…”

Lithographic properties of novel acetal-derivatized hydroxy styrene polymers

“…These PAGs require UV exposure as well as heating for complete photoacid generation, hence the subsequent acidolysis reaction takes place only during the post-exposure heating step. Another approach to reducing volume loss during exposure is to modify the acetal functionality, such that the deblockmg reaction would generate less volatile byproducts [9].…”