Mechanically induced strain enhancement of metal–oxide–semiconductor field effect transistors

Device characteristics and analysis are reported for strained silicon $n$ - and $p$ - channel partially depleted metal oxide semiconductor field effect transistors (MOSFETs) at 300 K. The devices were fabricated commercially on standard silicon-based silicon-on-insulator substrates and strain was applied mechanically after fabrication. Uniaxial tensile strain was applied within the elastic region using a back-end process and the relaxed structures were characterized under steady state conditions. Characterization was performed before and after straining. At ultralow strain levels (0.031%), $p\mathrm{MOSFETs}$ showed an increase in effective mobility ${\mu }_{\mathrm{eff}}$ of 14.35% and an enhanced saturation current, $I_{\mathrm{sat}}$ of 14.56%. An improvement in ${\mu }_{\mathrm{eff}}$ of 15.19% and in $I_{\mathrm{sat}}$ of 15.34% was observed for $n\mathrm{MOSFETs}$ strained by 0.039%. The latter die was debonded, released, and restressed at an elevated level of 0.052%. We observed an increased effective mobility ${\mu }_{\mathrm{eff}}$ of 18.49% and $I_{\mathrm{sat}}$ of 18.05%. Elastic uniaxial strain was fixed and characterization was performed at each strain level. The greatest mobility enhancement was observed for holes with strain applied at right angles to the channel length and applied field.