Experimental study on deformation potential (D_ac) in MOSFETs: Demonstration of increased D_ac at MOS interfaces and its impact on electron mobility

Deformation potential (D_ac), which is one of the most important parameters determining the rate of electronacoustic phonon scattering, in Si around MOS interfaces is thoroughly studied with regard to the dependences on surface carrier densities, back-gate biases, and device structures. It is demonstrated that D_ac increases sharply at the MOS interface. To investigate the impact of the increased D_ac on μe, thick body-channel SOI MOSFETs, where drain current flows in the entire SOI layers, was fabricated. The carrier transport experiments reveal that μe of greater than 1100 cm²V^-1s^-1 is obtained in body-channel SOI MOSFETs with the SOI thickness of greater than 70 nm. By taking into account the D_ac profile around the MOS interface, experimental μe of SOI MOSFETs is numerically reproduced over a wide range of SOI thicknesses. μe of the body-channel SOI MOSFETs is also well reproduced using the same D_ac profile. Thus, it is concluded that D_ac increases sharply at the Si/SiO₂ interface. The accurate modeling of the increased D_ac around the Si/SiO₂ interface is indispensable for designing high-performance and/or low-power 3-D MOSFETs including FinFETs, extremely thin SOI MOSFETs, and nanowire MOSFETs, because these types of MOSFETs have greater interface-to-volume ratios.