High-temperature and self-heating effects in fully depleted SOI MOSFETs

In this paper, the high-temperature and self-heating effects in the fully depleted enhancement lightly doped SOI n-MOSFETs are investigated over a wide range of temperatures from 300 to 600 °K by using the SILVACO¹ TCAD tools. In particular, we have studied their current-voltage characteristics (I_D-V_GS and I_D-V_DS), threshold voltages and propagation delays. Simulation results show that there exists a biasing point where the drain current and the transconductance are temperature independent. Such a point is known as the zero temperature coefficient (ZTC) bias point. The drain current ZTC bias points are identified in both the linear and saturation regions whereas the transconductance ZTC bias point exists only in the saturation region. We have observed that decreasing the film thickness could reduce the threshold voltage sensitivity of the SOI MOSFET with temperature and that the drain current decreases with increasing temperature. We have also noted that due to the self-heating effects, the drain current decreases with increasing drain bias exhibiting a negative conductance and that the self-heating effects reduced at a higher operating temperature. Self-heating effects are more pronounced for higher gate biases and thinner silicon films whereas the bulk device shows negligible self-heating effects.