This project, “Pitch Division Photolithography at 365 nm,” seeks to improve patterning resolution by using a traditional 248 nm photoresist polymer in conjunction with a photo-acid generator (PAG) and a photo-base generator (PBG). This formulation can achieve a two-fold improvement in photolithography resolution without the need for new equipment or significant changes in processing conditions. The photoresist matrix used in this work is poly[4-[(tert-butoxycarbonyl)oxy] styrene] (PTBOC), which is employed in combination with a PAG in 248 nm resists. When exposed to light, the PAG decomposes to form acid which, upon post-exposure baking, deprotects multiple pendant groups on the PTBOC, changing its solubility. This polymer exhibits another key feature: below a threshold dose, the polymer will not appreciably dissolve in aqueous base, but above this dose, the dissolution rate increases several orders of magnitude. This behavior becomes vital at feature sizes that approach theoretical resolution limits. Because the dissolution rate is controlled by the acid content within the polymer matrix, it is possible to cross the dissolution threshold twice with increasing dose if the acid is somehow quenched at higher doses. A PBG is an easy way to achieve this goal. If a PBG is chosen such that it is decomposes more slowly than the PAG and is incorporated with a stochiometric excess, then this dissolution threshold may be crossed twice with increasing dose. If the relative rates of the PAG and PBG decomposition are tuned such that the two dissolution thresholds properly match a sinusoid intensity profile, the resolution of patterns can be improved by a factor of two. In this work, we report several combinations of PAGs and PBGs that meet the above criteria and show promise for exhibiting pitch-division. These combinations were tested by exposing a film to a given dose and then developing in an aqueous base solution. It was found that the relative dissolution rates closely match the ideals described above. These combinations are ready for testing with an exposure tool to verify their function as a pitch division photoresist.

Pitch-division photolithography at 365 nm

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.