Improved second breakdown of integrated bipolar power transistors

This paper presents two new power bipolar transistor structures With greatly increased forward Second breakdown values without saturation voltage degradation. These structures, labeled
S
1 and
S
2, were obtained with slight modification of the output stages of an IC power amplifier and without complicating the standard IC process. The design concepts developed in this paper were applied to power transistors fabricated using two different processes already in production: process
A(V_{CEO(sus)} \gt 50
V) and process
B(V_{CEO(sus)} \gt 80
V). Measurements have Shown that an improvement of three times for dc conditions and four times or more for single pulses duration of less than 1 ms can be obtained for structure
S
1 while structure
S
2 is able to achieve the proportionality between power silicon area and power levels. Experimental temperature distributions over emitter area and some theoretical calculations for the steady-state condition are given.