Unified Compact Model for Generic Double-Gate MOSFETs
X. Zhou, G.H. See, G.J. Zhu, K. Chandrasekaran, Z.M. Zhu, S.C. Rustagi, S.H. Lin, C.Q. Wei and G.H. Lim
Nanyang Technological University, SG
compact modeling, double gate, MOSFETs, unified regional modeling, URM, Xsim
A generic double-gate (DG) MOSFET follows a generalized (input) voltage equation from the first integral of Poisson equation and Gauss' law at the two gates, which is implicit and, in general, non-integrable when the channel is doped. Only DG with undoped channel can be solved with implicit/coupled surface-potential equations, or approximate surface-potential solutions for doped symmetric-DG (s-DG) structures. The most challenging task in DG compact modeling is the surface-potential solutions for the generic asymmetric-DG (a-DG) doped-channel device: scalable over oxide thickness (from DG to SOI), channel thickness and doping (from UTB/fully-depleted to bulk/partially-depleted), and bias (a-DG to s-DG). Once it is conquered, the model will be able to cover different structures and operations with seamless transitions. In this paper, we present solution methods towards such a unified MOS compact model based on the unified regional modeling (URM) approach. Regional/explicit solutions are available for the generic doped a-DG in accumulation, depletion, weak/volume-inversion regions, and approximate solutions in inversion region for the two gate's surface potentials. The unified solutions are obtained with smoothing functions, which contain the essential physics captured in the regional solutions that are otherwise impossible to obtain, and can be applied to terminal current/charge models with physical layer thickness and doping scalability. The results demonstrate a first step towards unification of MOS compact models for the existing (bulk) and emerging (multi-gate) MOSFETs with seamless transitions and selectable accuracy.
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Nanotech 2007 Conference Program Abstract