Sidewall chemical analysis of plasma-etched nano-patterns using tilted X-ray photoelectron spectroscopy combined with in-situ ion sputtering

Abstract

A novel experimental technique for sidewall analysis of plasma-etched nano-patterns using tilted X-ray photoelectron spectroscopy (XPS) combined with in-situ ion sputtering was investigated. Complete removal of the residue layer (on the mask surface) and the mask layer using in-situ ion sputtering in the XPS chamber was conducted to reveal the sidewall information of the plasma-etched hole in SiO2 in addition to the trench in Si, after anisotropic plasma etching. The influence of the measured profile depth changes after adjusting the take-off angle in the sidewall chemistry of the plasma-etched hole in SiO2 and the trench in Si was examined. To demonstrate the analysis results, the sidewall compositions of the plasma-etched hole in SiO2 with various oxygen contents in the plasma were comparatively analyzed using XPS and Auger electron spectroscopy. It was observed that fluorinated carbon polymer (C-Fx, x ≤ 3) and SixOy (x ≤ 2, y ≤ 3) residue layers were formed on the hole in SiO2 and trench in Si sidewalls after C4F8/CH2F2/O2/Ar and HBr/Cl2 plasma etching, respectively. Thus, changes in the chemical characteristics of these sidewall etching residues were realized, revealing their dependency on the pattern size and type, plasma gas chemistry, and mask material. In addition, effectiveness of the dry cleaning process was evaluated using the tilted XPS combined with in-situ Ar ion sputtering.