Hole mobility enhancement in uniaxially strained SiGe FINFETs: Analysis and prospects

Abstract

Experimental and theoretical hole mobility study in uniaxially strained (110)<110> Si0.75Ge0.25 pFINFETs shows that alloy scattering contributes only a small fraction of the overall mobility at 300K but plays a bigger role limiting 77K hole mobility. Increasing the Ge content to 50% increases the strain level. However, the extent of strain relaxation depends on the length of the fin. Fig. 10 shows the measured and projected hole mobility for SiGe FINFETs with 25% and 50% Ge mole fraction. Higher strain induced reduction of effective mass compensates for the increased interface charge density, Dit, in SSGOI0.5 pFINFET and alloy disorder and results in 157% increase in the hole mobility observed at Ns=1×1013 cm−2 and T=300K. Fig. 11 benchmarks the hole mobility in SSGOI0.25 and SSGOI0.5 pFINFETs as a function of electrical oxide thickness (TOXE) and shows its advantage over relaxed Ge channel MOSFETs. However strain relaxation for shorter length fins need to be addressed using careful layout techniques. High mobility combined with excellent short channel behavior make these devices a promising candidate for future technology node.