Performance and Reliability Improvement in Ge nMOSFETs with Different Surface Orientations through Channel Flattening Process

The impact of channel flattening process, dozen digital etching (DDE), on device performance and reliability of Ge nMOSFETs with different surfaces of (100), (110) and (111) has been systematically investigated. It was found, for the first time, that DDE improves not only electron mobility but also gate oxide reliability, especially on Ge (100). Decrease of surface roughness, as well as interfacial/bulk trap densities in gate oxide could explain these phenomena. Thanks to DDE, the electron mobility of Ge (100) devices can compete with those of Ge (111) devices while possessing higher reliability.