Influence of solubility switching mechanism on resist performance in molecular glass resists

Five different molecular glass chemically amplified photoresists which utilized different solubility switching mechanisms and chemistries, based on a tris(4-hydroxyphenyl)ethane (THPE) core, were synthesized and their performance compared. Three different positive tone systems were designed based on acid catalyzed deprotection of a phenolic hydroxyl group protected with one of the following groups: tert-butoxycarbonyl (tBoc), tetrahydropyranyl, or ethoxyethyl. Two negative tone systems were designed; one using cationic epoxide polymerization of pendant epoxides and one using condensation of the unprotected THPE with a multifunctional cross-linking additive. The tBoc system and negative tone systems showed good performance under deep UV and large field e-beam patterning, but the epoxide system showed far superior performance for high resolution electron beam patterning. It was able to produce 50nm 1:1 line/space patterns and 30nm lines on 1:3 line/space patterns with high sensitivity, good contrast, and a very low line edge roughness (3σ) of 2.3nm using 100keV electron beam patterning.