Key differences for process-induced uniaxial vs. substrate-induced biaxial stressed Si and Ge channel MOSFETs

摘要

For both n and pMOSFETs, this paper confirms via controlled wafer bending experiments and physical modeling the superiority of uniaxial over biaxial stressed Si and Ge MOSFETs. For uniaxial stressed p-MOSFETs, valence band warping creates favorable in and out-of-plane conductivity effective masses resulting in significantly larger hole mobility enhancement at low strain and high vertical field. For process-induced uniaxial stressed n-MOSFETs, a significant performance advantage results from a smaller threshold voltage shift due to less bandgap narrowing and the gate also being strained.