The Highly Selective Wet Etching Process of SiO2 to TiSix

Abstract

The relatively higher etch rate of titanium silicide to silicon oxide in HF-based solution was ascribed to the strong interaction of the positively charged hydrogen with titanium, which has very low electron affinity relative to other metals. Based on the electron-transfer mechanism of dissolution, we developed the highly selective etching material (T-Block) mainly composed of fluoride salt and low dielectric constant solvent. To overcome the self-limiting nature of the T-Block material in the etch process, we devised the iterative treatment process, which is more suitable for single-wafer processing equipment. In contrast to the normal etching solution such as buffered oxide etchant or HF, T-Block did not show any kind of failure regarding dissolution even when the underlying bit-line contact was disclosed to T-Block in the wet etch process. Therefore, if T-Block is applied in a fabrication process with the 6F2 cell design, a significant enhancement of productivity through process simplification as well as production yield is expected.