Wet Cleaning and Surface Preparation for Ge

Abstract

In the process flow with Ge material, several wet cleaning steps are considered as post Ge channel deposition, post gate etch and post spacer etch. For these cleanings, not only high PRE (Particle Removal Efficiency) but also the control of Ge loss is required. We confirmed the characteristic of PRE on the Ge surface and Ge loss with conventional chemistries. Particles can be removed by the lift-off phenomena using ozonated water but a large amount (> 3nm) of Ge loss were required to obtain sufficient PRE. Applying diluted APM for high pH oxidation chemistry can minimize Ge loss while keeping effective particle removal. However since evaluated APM (1:1:20,000) still etches Ge layer first, it might have an issue of the concentration controllability and reproducibility. In this paper, we demonstrated a novel chemistry alternative to highly diluted APM that has proven significant competitive advantages.