Evaluation of Mobility Degradation Factors and Performance Improvement of Ultrathin-Body Germanium-on-Insulator MOSFETs by GOI Thinning Using Plasma Oxidation

摘要

Mobility degradation factors in ultrathin body (UTB) germanium on insulator (GOI), including the back interfacial quality and the crystal quality, have been experimentally examined and identified. By comparing UTB GOI MOSFETs with different back-MOS interfaces and crystal qualities, it is found that the interfacial quality is more critical to the GOI effective mobility than the crystallite quality in the thin body GOI MOSFETs ranging from 30 nm down to 10 nm. A novel way to realize UTB GOI MOSFETs by plasma oxidation (PO) at room temperature is proposed, in order to prevent potential degradation to the Ge/buried oxide back interface and realize precise GOI thickness control. UTB GOI MOSFETs down to 7.2 nm is successfully fabricated on the flipped GOI thinned by PO. The GOI thickness dependence of the effectivemobility is experimentally examinedby usingGOIMOSFETs fabricatedby this thinning method. It is found that the GOI MOSFETs thinned by PO exhibit higher mobility at a given GOI thickness than those thinned by thermal oxidation.