Extraction of eleven model parameters for consistent reproduction of lateral bipolar snapback high-current I-V characteristics in NMOS devices

Abstract

A series of literature models originally devoted to the second breakdown trigger current I/sub t2/ in a grounded-gate NMOS transistor can further find promising potential in handling high-current I-V due to lateral bipolar snapback. This is achieved primarily by building significant linkage between bipolar current-gain /spl beta/-related parameters: 1) the collector-to-base junction voltage dependencies A/sub 1/ and A/sub 2/ of the medium-level injection /spl beta/ roll-off factor; 2) the high-level /spl beta/ roll-off factor A/sub 3/; and 3) the collector-to-base junction voltage dependencies A/sub 4/ and A/sub 5/ of the collector corner current at the onset of high-level /spl beta/ roll-off. The new parameters A/sub 1/ to A/sub 5/ enable a consistent I-V solution along with other existing six model parameters such as the substrate resistance R/sub sub/ and its conductivity modulation factor A/sub /spl tau//, the impact ionization coefficients K/sub 1/ and K/sub 2/, and the emitter series resistance R/sub e/ and collector series resistance R/sub c/. Parameter extraction except R/sub c/ is thoroughly performed using only the parametric analyzer, and opposed to the traditional procedure, impact ionization coefficients and current gains are all assessed without entering the snapback regime. Remarkably, not only excellent agreements are obtained, but also bipolar snapback I-V measured under the current pulsing condition can be separated into two distinct parts: medium- and high-level injection region. This is quite effective under R/sub e/=R/sub c/. Series resistance, although having very low value, is not to be absent under the high-level injection conditions.