A physical compact model for direct tunneling from NMOS inversion layers

This paper presents a physically based, analytical, circuit simulation mode l for direct tunneling from NMOS inversion layers in a MOS structure. The m odel takes account of the effect of quantization on surface potential in th e silicon, the supply of carriers for tunneling and the oxide transmission probability. The inclusion of quantum effects is based on a variational app roach to the solution of the Poisson and Schrodinger equations in the silic on inversion layer [Rev Modern Phys 54 (1982) 437]. Usually the variational approach requires iterative solution of equations which is computationally prohibitive in a circuit simulation environment. In this paper, it is show n that by considering the dominant effects in weak and strong inversion, it is possible to formulate a set of equations which give all required quanti ties for the calculation of quantization in the inversion layer, without th e requirement for iterative solution. The tunneling model is based on the c oncept of transparency. Improved formulae for the transparency and the esca pe frequency are used. Comparisons with coupled Poisson and Schrodinger sim ulations and with measurements are demonstrated. (C) 2001 Elsevier Science Ltd, All rights reserved.