Thin layer etching of low-k SiCO spacer using hydrogen ion implantation followed by hydrofluoric acid

Abstract

Spacer etching realization is considered today as one of the most critical processes for the fully depleted silicon on insulator devices realization. The challenge arises from the fact that low-k spacer needs to be introduced to improve device performances. In this paper, a new approach to etch the low-k SiCO film was investigated. This approach is based on the SiCO film modification by H2 plasma followed by a removal step of this modified layer using hydrofluoric acid- (HF) based wet cleaning. It has been demonstrated that SiCO layer modification depth is controlled by plasma parameters like bias voltage. The SiCO film modification induced by H2 plasma has been well understood by x-ray photoelectron spectroscopy, infrared spectroscopy analyses in transmission or in multi-internal reflection. It has been demonstrated that the H2 plasma exposure converts the SiCO film in volume into an SiOxHy film, explaining the higher damaged film removal rate when dipped in liquid phase HF. Finally, the compatibility of the new etch approach with the SiCO low-k film has been demonstrated on pattern structures.