Molecular glass resists for next generation lithography

The idea of using small molecules instead of polymers for next generation lithography may enable improved resolution and line edge roughness (LER). Rather than using polymeric materials we are focusing on a new class of materials known as molecular glasses (MGs). These are low molecular weight organic materials that demonstrate high glass transition temperatures despite their modest size. Unlike polymeric resists, these molecules have the added advantages of distinct size and uniformity. We have synthesized a series of molecular resists containing rigid aromatic backbones and phenolic moieties suited for electron beam and Extreme Ultraviolet (EUV) lithography as both positive tone and negative tone photoresists. An increase in glass transition temperature is observed with increasing size and rigidity. Glass transition temperatures (Tgs) between 80-130°C have been observed for tBOC protected positive tone resists with molecular weights within the range of 800-1200g/mol. MGs with branched, dense structures are explored to design high Tg resist systems with improved sensitivity and contrast. The effects of protection ratio, high and low activation protecting groups, post exposure bake conditions, etch resistance and outgassing have been tested using selected phenolic MG resists. These new resist architectures are synthesized and evaluated to attain sub 30nm feature sizes required of candidates for next generation lithography.