Analysis and Modeling of NQS Effects in MOSFET’s

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Three issues regarding NQS effect in MOSFET’s are investigated: When NQS effect becomes significant, NQS effect on channel charge partition, and its implementation in advanced MOSFET models (PSP, Hisim2 and Bsim4).
Channel segmentation method [1] with N=10 is used in the investigation. Device is biased at strong inversion region with Vds=0. Small signal input is added to drain node and gate current is used as monitor. The starting point of NQS (5% degradation of the segmentation simulation compared with single device simulation) is found to be around 30% to 40% of device unit-gain frequency (ft), and the percentage is smaller for shorter devices. Simple model is developed to model the frenquency and channel length dependent of NQS starting point.
Drain charge is found to be around 35% of the total channel charge using segmentation simulation, while it is 44% for single device simulation without NQS effect, and around 42% for single device simulation with NQS effect using hisim2 model. This shows the difference from the 40/60 Ward-Dutton charge partition in QS mode.
Three NQS implementations are compared: internal node approach (Bsim), hidden state approach (Hisim) and Spline corelation approach (PSP). First two are theoretically equivalent. Non-ideal behavior are observed in the latter two and analized in this work.

[1] A.J. Scholten, L.F. Tiemeijer, P.W.H. de Vreede and D.B.M. Klaassen, Tech. Dig. International Electron Device Meeting, 1999, p163

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Journal: TechConnect Briefs
Volume: 3, Technical Proceedings of the 2006 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: May 7, 2006
Pages: 780 - 783
Industry sector: Sensors, MEMS, Electronics
Topic: Compact Modeling
ISBN: 0-9767985-8-1