Characterization of TSV etch from a sustainability standpoint

Abstract

The recent passing of the CHIPS act has highlighted the semiconductor industry as a driver of innovation. Simultaneously, environmental legislation regarding per- and polyfluoroalkylated substances (PFAS) usage has become a major focus in both the US and EU, which has potential implications for many hydro- and perfluorocarbon (HFC/PFC) gases currently used in semiconductor manufacturing. High-aspect ratio (HAR) etch processes are a critical component of two high-growth manufacturing areas (packaging and solid-state memory), however, they are significant consumers of HFC/PFC chemistries due to the vertical scale of the features involved. This paper analyzes reduced gas flow effects in a HAR through-silicon via (TSV) etch process, with the aim of improving the sustainability of future processes through an improved mechanistic understanding. We demonstrate a cyclic C4F8 /SF6 TSV process with ~90% ER and comparable sidewall roughness using 50% of the SF6 flow rate and 60% of the passivation time. We also show through TOF-SIMS analysis a depth dependence of the sulfur and fluorocarbon concentrations on the TSV sidewall which varies with gas flow rate, providing further insight into the mechanisms associated with HAR etching.