Schottky-barrier-height engineering for strained-Si MOSFETs

The Schottky source/drain MOSFET (SSD-MOSFET) is an attractive design for ballistic MOSFETs because it has the potential to allow high-energy carrier injection from a metal source to an intrinsic channel (J.R. Tucker et al, Appl. Phys. Lett., vol. 65, p. 618, 1994; J. Kedzierski et al, IEDM Tech. Dig., p. 57, 2000). However, achieving high-drive current is difficult because of the relatively high potential barrier (Schottky barrier) at the source. To overcome this problem, we have proposed the Schottky-barrier-height (SBH) engineering through semiconductor bandgap modulation (K. Ikeda et al, 60th DRC late news paper; K. Ikeda et al, IEEE Electron Device Lett., vol. 23, p. 670, 2002). For effective SBH engineering with high controllability, stress control to control the bandgap is key issue. However, we know of no published reports on strain distributions in a strained-Si channel or at silicide/strained-Si interfaces. In this paper, we demonstrate strain-distribution analysis using STEM micrographs of a strained-Si channel SSD-MOSFET combined with fast-Fourier transform mapping (FFTM) (T. Ide et al, Jpn, J. Appl. Phys., vol. 37, p. L1546, 1998).