Process characterization of inductively coupled plasma etched silicon nanopillars by micro-Raman

Abstract

The authors report on the top-down fabrication of silicon nanopillar arrays using electron beam lithography and enhanced plasma etch protocols for producing smoothed sidewalls. They have used cold development (2–4°C) to minimize line edge roughness in the patterned features. Standard reactive ion etch and inductively coupled plasma etch techniques have been used to fabricate nanopillar arrays, 60–100nm in diameter, with aspect ratios up to 20:1. They describe the use of a cyclic plasma oxidation and etch procedure to reduce sidewall roughness of silicon etched by the Bosch® process. The optimization of the smoothing process is demonstrated to produce near roughness free sidewalls. Raman spectroscopy has been used to characterize both the attributes of the nanopillars (including black silicon) and the effects of plasma processing. Preliminary results indicate that the Raman technique can distinguish the quality of the nanopillars (from processing perspective) based on intensity, spectral shifts, and changes in the linewidth. These changes are attributed to an increase in local heating of smoothed nanopillars caused by a modulation in optical absorption.