Modeling of lateral C-V dependence of coaxial MOSFET with built-in charge in oxide layer

Full text: The charge built - in a oxide layer influences the MOSFET characteristics , in particular on both C-V dependence a gate-substrate and source substrate junctions. The built - in charge can be used as a bit of the information, which reading can be based on influence of a charge on the specified characteristics. In this work the influence of a charge built - in oxide layer of coaxial MOSFET on C-V dependence of a source - substrate (S-S) transition is simulated. The S-S transition represents p+ - n transition which capacity depends on his width. The charge built - in a oxide layer causes a curvature of border, reduction of width of the transition and by that increase of his capacity, which can be used as a signal or bit of the information. The change of transition width is estimated on distribution of concentration of the not basic carriers along both z and r axes of cylindrical substrate. Taking into account, that the positive charge built - in in oxide layer about Si-SiO2 interface causes enrichment of a substrate surface we can receive expression for concentration of the not basic carriers which depend on both potential distribution of built - in charge q(z,r) and potential of a field on S-S transition f(z). q(z,r) is determined from Poisson equation by numerical methods. q(z,r) depends on density and distribution of a built-in charge in oxide. The topography of S-S transition border is received and capacity in approach of the flat condenser is evaluated at various voltage on transition. The results show appreciable increase of capacity in all range of voltage that can be used as a source of a signal of bit of the information. (authors)