Thermal time constants in SOI-MOSFETs

The authors present detailed theoretical considerations and a first-order analytical model for the dynamical behavior of self heating in SOIMOS (silicon-on-insulator metal oxide semiconductor). They show the results of the simulated spreading of heat when switching a SOIMOS in the on-state. At least four different time constants can be detected: spreading vertically through the channel region within about 100 ps; passing gate oxide and heating the polygate within 10 ns; heating up S/D-regions and buried oxide within 1 μs; and at about 1 μs heat energy reaches the substrate. The effects showing temperature rise vs. time in the channel and at backside interface are summarized. It is concluded that, in pulsed measurements of SOIMOS output characteristics, a pulse length of 10 ns will already produce an elevated temperature on the order of 10% of the steady-state value