Silicon etching in a pulsed HBr/O2 plasma. II. Pattern transfer

Abstract

The strong impact of synchronized plasma pulsing on an HBr/O2 silicon pattern etch process is studied with respect to the continuous process. This article focuses on blanket etch rates and a detailed analysis of the etched profiles, where several significant features of plasma pulsing are identified. First, the time compensated (TC) silicon etch rate is increased while the SiO2 TC etch rate is decreased at a low duty cycle, whereby the selectivity between silicon and SiO2 etching is strongly increased. Furthermore, the thickness of the sidewall passivation layer is reduced, thereby guiding the etched profile. Finally, the overall homogeneity is increased compared to the continuous wave etching process.