RESURF Model and Electrical Characteristics of Finger-Type STI Drain Extended MOS Transistors

Finger-type shallow trench isolation (finger STI) drain extended MOS transistors are fabricated and its electrical characteristics is studied. Polyplate on a finger STI served as a reduced surface field is adopted to enhance breakdown voltage (BV) by reducing the effective doping concentration of the drain extension (DE) finger. The conformal mapping method, which relates the reduction of the doping concentration to the width (
$z_{o}$
) of the DE finger, the gap (
$z_{d}$
) between the polyplate and the DE finger, and the STI depth
$y_{s}$
, is used to estimate the reduction of the doping concentration theoretically. Based on this reduced doping concentration, a BV model is derived. The predictions of this model agree very well with the experimental data.