Understanding the mechanisms impacting the interface states of ozone-treated high-k/SiGe interfaces

Abstract

High-k/SiGe interface control for low interface state density (D-it) is one of the most critical issues for realizing SiGe-based MOSFETs. Among various SiGe MOS interlayers (ILs), oxide IL passivation performed by low-temperature ozone oxidation is one of the most promising methods. In this study, we have examined the interfacial chemical structures and the electrical properties of the Al2O3/IL/SiGe gate stacks fabricated under various ozone oxidation conditions. It is experimentally found that D-it values vary with two factors, one is the SiOx thickness and the other is the ratio of Si4+ component in SiOx. The increase in the SiOx thickness causes more Ge atoms to accumulate at the IL/SiGe interface, which means more Ge dangling bonds at the interface and higher D-it in the band gap. Conversely, the increase in the ratio of Si4+ component in SiOx leads to a decrease in D-it. Based on the perturbation theory of quantum mechanisms, this phenomenon may be explained by the remote coulomb potential perturbation arising from high-oxidation-state Si atoms.