A physically based analytical model for the threshold voltage of strained-Si n-MOSFETs

• Published in: IEEE transactions on electron devices 2004-12, Vol.51 (12), p.2069-2072
• Main Authors: Nayfeh, H.M., Hoyt, J.L., Antoniadis, D.A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Compound structure devices; Electronics; Exact sciences and technology; Heterostructure; MIS devices; mobility enhancement; MOS devices; MOSFET; MOSFETs; Semiconductor device doping; Semiconductor device modeling; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; SiGe; silicon; Silicon materials/devices; strained-Si n-MOSFETs; Transistors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2004.838320

A physically based analytic model for the threshold voltage V/sub t/ of long-channel strained-Si--Si/sub 1-x/Ge/sub x/ n-MOSFETs is presented and confirmed using numerical simulations for a wide range of channel doping concentration, gate-oxide thicknesses, and strained-Si layer thicknesses. The threshold voltage is sensitive to both the electron affinity and bandgap of the strained-Si cap material and the relaxed-Si/sub 1-x/Ge/sub x/ substrate. It is shown that the threshold voltage difference between strained- and unstrained-Si devices increases with channel doping, but that the increase is mitigated by gate oxide thickness reduction. Strained Si devices with constant, high channel doping have a threshold voltage difference that is sensitive to Si cap thickness, for thicknesses below the equilibrium critical thickness for strain relaxation.