Asymmetric source/drain extension transistor structure for high performance sub-50 nm gate length CMOS devices

In this paper, we present for the first time an asymmetric source/drain extension (SDE) transistor structure which can achieve high I/sub DSAT/ at gate dimensions below 50 nm. We demonstrate that this structure alleviates the severe I/sub DSAT/ degradation reported in the literature for devices when gate to source/drain overlap dimensions are reduced to under 20 nm/side (Thomson et al, 1998). Sub-15 nm gate to source/drain overlap is mandatory for supporting gate dimensions below 50 nm (Ghani et al, 2000). Moreover, fabrication of this structure employs a standard process flow in which SDE regions are formed by ion implantation and a subsequent drive-in anneal. Fundamental principles of device operation of the asymmetric SDE transistor are presented followed by a description of the process flow and an in-depth analysis of electrical characteristics and associated trade-offs.