Numerical extraction of capacitance in a-Si thin-fim transistors

摘要

We present a new comptuational approach for extracting the quasistatic parasitic coupling capacitance associiated with geometric overlappling in amporphous silicon (a-Si) thin-film transistors (TFTs). The method is based on efficient evaluation of the three-dimensional potential and the electric field using expenential expansion of the Green's function 1/r to facilitate accurate large-scale parasitic capacitance ex-traction in complex device structures and arrays. using this technique, we study the effect of the fringing field for the case of small overlap length and that of substrate perimittivity on the overlap capacitance in TFTs. The fringing field results in non-trivial capacitance even with non-overlapping structures and the capacitance is found to increase w ith perimittivity of the sustrate.