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 Si0.5Ge0.5 chemical mechanical polishing (CMP) under alkaline condition were investigated. The results show that, DTPA-5K is a corrosion and rate enhancer for Si0.5Ge0.5. GeO2 and the silicon sub-oxide are believed to be generated on Si0.5Ge0.5 surface in DTPA-5K solution. The Si0.5Ge0.5 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 Si0.5Ge0.5 can be improved by triethanolamine (TEA). An optimized slurry formulation in the presence of DTPA-5K and TEA yielded a high Si0.5Ge0.5 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.
Published Version
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