Strain enhanced p-type metal oxide semiconductor field effect transistors

Abstract

Results are reported for Si p-channel metal oxide semiconductor field effect transistors (pMOSFETs) subjected to a combination of tensile and compressive strains in different directions. This combination strain is reported and discussed. Results are reported for both partially depleted and bulk architectures. The maximum increase in effective mobility μeff attained in bulk pMOSFETs was 120.19% and the corresponding increase in saturation current Isat was 120.08% for 1.6% strain. Partially depleted devices were strained up to 2.2%, giving an increase in effective mobility μeff of 138.40% and increase in saturation current Isat of 147.74%. Tensile stress was applied orthogonal to the carrier transport direction (transverse) and compressive stress was induced along the channel, resulting in unprecedented increases in both output and effective mobility. Our straining technique involves thinning die and wafer sections of commercially fabricated devices until they are ultrathin (<10μm); stress is then applied mechanically. Measurements were performed on devices “as fabricated” and also after thinning and layer transfer. Stress was applied at predefined values and characterization was carried out. The “strain and characterization” sequence was repeated until the applied stress exceeded the elastic region.