Computationally efficient determination of threshold voltages in narrow-channel MOSFETs including fringing and inversion effects

A method for computing threshold voltages for narrow-channel MOSFETs based on infinite-network theory is presented. The technique enables a domain contraction down to a narrow strip containing the gate contact. Its principal advantage is that it takes into account the fringing of the electric field in the infinite domain above and below the strip without any domain truncations outside the strip. Thus, it does not assume any artificial boundary conditions except at the extremities of the strip, and, consequently, provides more accurate results. Furthermore, the charges of the mobile carriers in the channel-inversion layer are not ignored. The method is general enough to take into account various other determinants. Moreover, the required nodal analysis need be made only for the nodes within the strip and, therefore, the number of equations to be solved is decreased by an order of magnitude, as compared to the standard finite-difference analysis. The computed depletion profile and the total charge of the surface mobile carriers change as the gate-contact width decreases, and this in turn increases the threshold velocity in conformity with the expected narrow-channel effect.<
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