Electrochemical study of SiGe in different alkaline chemical formulations

Abstract:
As continuous shrinking and scaling down, silicon CMOS devices approach their physical limitations. This results in an increased interest in introducing high mobility channel materials beyond 14nm technology node. Due to the high mobility, SiGe has already attracted wide attentions. In this work, the electrochemical properties of Si0.5Ge0.5 in different alkaline chemical formulations were studied. Some alkalis and oxidants were selected as additives, and the effects of their respective concentrations and pH values on the electrochemical characteristics were also systematically investigated. It was found that organic alkalis such as EDA and DTPA-5K had strong corrosivity to Si0.5Ge0.5, since they could significantly decrease the corrosion potential (Fig.1). Similarly, ammonia also exhibited a certain level of corrosivity. With regard to oxidants such like H2O2 and NaClO, Si0.5Ge0.5 was corroded at very low concentrations, while obvious passivation phenomenon was observed at the high concentrations; the corrosion effect highly depended on the pH value in alkaline conditions (Fig.2). Based on the results, the two formulations with EDA and DPTA-5K are the best candidates for the SiGe CMP study in the future. Keywords: SiGe, Channel material, Electrochemistry, Corrosivity, CMP