Behavior Analysis of Si Etching Process with HF/HNO3 Mixture in Single-Spin Wafer Process

Abstract

The HF/HNO3mixture Si etching process is widely used to remove stress and damaged layers after Si wafer back grinding. Although there have been many reports on the dip process, there have been few detailed reports on the single-spin process. In a single spin process, Si etch rate distributions largely differ with different HF/HNO3concentrations. On the other hand, thermal SiO2etch rate distributions are similar even with different HF/HNO3concentrations. In this work, we analyzed Si surfaces with XPS (X-ray Photoelectron Spectroscopy) after processing various HF/HNO3mixture concentrations. SiOxstays steady in any wafer position and HNO3concentration, whereas SiO2thickens depending on HNO3concentration at the center. We assumed that Si etch rate distributions were caused by HF or HNO3consumption and confirmed this assumption was correct in a wafer center SiN cover experiment.