Effect of multi-functional amines on SiGe surface finish during chemical mechanical polishing

Abstract SiGe is one of the most promising strain relaxed buffer at advanced technology nodes. In this paper, the effects of pentapotassium; 2-[bis[2-[bis(carboxylatomethyl)amino]ethyl] amino]acetate (DTPA-5K) and triethanolamine (TEA) on Si 0.5 Ge 0.5 chemical mechanical polishing (CMP) under alkaline condition were investigated. The results show that, DTPA-5K is a corrosion and rate enhancer for Si 0.5 Ge 0.5 . GeO 2 and the silicon sub-oxide are believed to be generated on Si 0.5 Ge 0.5 surface in DTPA-5K solution. The Si 0.5 Ge 0.5 removal rate and its selectivity to TEOS are both proportional to DTPA-5K concentration. However, DTPA-5K has an impact on the slurry stability. With proper DTPA-5K concentration to ensure colloidal stability, the surface roughness of Si 0.5 Ge 0.5 can be improved by triethanolamine (TEA). An optimized slurry formulation in the presence of DTPA-5K and TEA yielded a high Si 0.5 Ge 0.5 removal rate, an acceptable within-wafer non-uniformity (WIWNU), very low surface roughness and desirable selectivity to TEOS. A CMP mechanism for this system is also proposed.