Low-voltage transient bipolar effect induced by dynamic floating-body charging in PD/SOI MOSFETs

Abstract

Partially-depleted (PD) SOI MOSFETs offer improved threshold control and sensitivity over fully depleted devices, but the effects of dynamic floating-body charging on the threshold voltage VT(t) can possibly lead to instabilities in PD/SOI circuits. We show in this paper that the dynamic charging of the body can also induce a parasitic bipolar-transistor (BJT) transient current which can be significant even at low voltages well below the drain-source breakdown defined by the BJT. Our results indicate that if device/circuit design allows substantial variation of the body charge, then the transient BJT current could be large enough to upset the logic or memory (SRAM or DRAM) function of a chip. They further show that such an upset becomes more probable as the device is scaled, and they give insight regarding device and circuit design to reduce the probability.