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

Abstract

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%), pMOSFETs showed an increase in effective mobility μeff of 14.35% and an enhanced saturation current, Isat of 14.56%. An improvement in μeff of 15.19% and in Isat of 15.34% was observed for nMOSFETs 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 μeff of 18.49% and Isat 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.