SCALING CONSTRAINTS IMPOSED BY SELF-HEATING IN SUBMICRON SOI MOSFETS

The presence of a buried oxide layer in silicon causes enhanced self-heating in Silicon-On-insulator (SOI) n-channel MOSFET's, The self-heating becomes more pronounced as device dimensions are reduced into the submicron regime because of increased electric field density and reduced silicon volume available for heat removal, Two-dimensional numerical simulations are used to show that self-heating manifests itself in the form of degraded drive current due to mobility reduction and premature breakdown, The heat how equation was consistently solved with the classical semiconductor equations to study the effect of power dissipation on carrier transport. The simulated temperature increases in the channel region are shown to be in close agreement with recently measured data. Numerical simulation results also demonstrated accelerated turn-on of the parasitic bipolar transistor due to self-heating, Simulation results were used to identify scaling constraints caused hy the parasitic bipolar transistor turn-an effect in SOI CMOS ULSI. For a quarter-micron rt-channel SOI MOSFET, results suggest a maximum power supply of 1.8 V. In the deep submicron regime, SOI devices exhibited a negative differential resistance due to increased self-heating with drain bias voltage. Detailed comparison with bulk devices suggested significant reduction in the drain-source avalanche breakdown voltage due to increased carrier injection at the source-body junction, These results place important limits on the maximum supply voltage that can be applied.