Single-component silicon-based patterning materials for EUV lithography

A single-component silsesquioxane (SQ)-based material was developed and investigated for patterning in extreme ultraviolet (EUV) lithography. This negative-tone SQ-material is soluble in the industry standard aqueous alkali developer 2.38wt% tetramethylammonium hydroxide (TMAH). Early experiments using electron beam (EB) lithography showed pattern capability in resolving 18nm line patterns (exposure dose: 2000 μC/cm²). After numerous screening evaluations using EB lithography, one variant was selected for patterning evaluation with EUV lithography. Patterning resolution was confirmed at 19nm line patterns (exposure dose: 200 mJ/cm²), with evidence of pattern modulation down to 15nm. As revealed in these preliminary patterning investigations, low sensitivity is the obvious issue. To understand the reaction mechanisms of this SQ-based material, various analyses were also carried out. Results reveal the occurrence of direct photo-crosslinking (no main scission) of Si-O-Si bonds from the decomposition of Si-OH components on exposure, resulting in insolubility in the developer solution (negative tone). Lastly, to address the sensitivity issue, the application of what we refer to as "Sensitivity Enhancer Unit" was utilized. EB lithography results show an improvement in sensitivity indicating a possible solution to the low sensitivity issue. These results show the potential applicability of the single-component SQ-based patterning material for both EUV and EB lithography.