Reduction of proximity effect in fabricating nanometer-spaced nanopillars by two-step exposure

Abstract

A two-step exposure method to effectively reduce the proximity effect in fabricating nanometer-spaced nanopillars is presented. In this method, nanopillar patterns on poly-methylmethacrylate (PMMA) were partly cross-linked in the first-step exposure. After development, PMMA between nanopillar patterns was removed, and hence the proximity effect would not take place there in the subsequent exposure. In the second-step exposure, PMMA masks were completely cross-linked to achieve good resistance in inductively coupled plasma etching. Accurate pattern transfer of rows of nanopillars with spacing down to 40 nm was realized on a silicon-on-insulator substrate.

Review—Nanopillar Structure in the Direction of Optical Biosensor On-Chip Integration

“…Fortunately, this issue can be solved using two steps resist development or second-step exposure with PMMA as a dual-tone resist. 54 PMMA itself is an organic resist that works differently depending on the irradiating dose level. [55][56][57][58] At a low dose, PMMA act as a positive-tone resist, where the EBL break down molecular PMMA into smaller molecule (chain scission).…”