The impact of the combination of xanthan gum and polyvinyl pyrrolidone (PVP) on the chemical mechanical polishing of through silicon via (TSV) barrier layer

Abstract

The material of the through silicon via (TSV) barrier layer is thicker than the barrier layer for copper wiring. In the chemical mechanical polishing (CMP) process, it is required to maintain a high removal rate of the tantalum (Ta) barrier layer and a low surface roughness and non-uniformity. To meet this technological challenge, the effect of a novel surfactant, xanthan gum, and polyvinylpyrrolidone (PVP) complex on the polishing performance and stability of the TSV barrier layer slurry under the conditions of pH 9, SiO2 concentration of 10 wt%, H2O2 concentration of 0.3 wt%, guanidine phosphate concentration of 1.5 wt%, and benzotriazole (BTA) concentration of 0.3 wt% was studied. The synergistic mechanism of xanthan gum and PVP was analyzed by electrochemical, X-ray photoelectron spectroscopy (XPS), and contact angle tests. The surface quality of Ta and copper (Cu) after polishing under different conditions was compared using atomic force microscopy (AFM). The experiment showed that when 0.025 wt% xanthan gum and 0.025 wt% PVP were added to the slurry, the removal rates of Ta and Cu were 109 nm/min and 51 nm/min respectively, and the surface non-uniformity was 2% and 1.9% respectively. At this time, the surface roughness Sq and Ra of Ta were 0.191 nm and 0.0215 nm respectively, and the surface roughness Sq and Ra of Cu were 0.344 nm and 0.0349 nm respectively, indicating that the slurry compounded with xanthan gum and PVP can maintain a high Ta removal rate while obtaining a high surface quality.