Improved thermal stability in SiGe HBTs by emitter layout

Abstract

A new emitter layout in SiGe HBT is presented to improve the thermal stability. For comparison, a SiGe HBT with conventional layout is also fabricated. The thermal resistance and I-V characteristics of two types of HBTs at different biases and ambient temperature are measured and compared. Experimental results show that the new emitter layout is very effective in enhancing thermal stability over a wide range of operation and ambient temperatures. When compared with the old layout, the power level for thermal instability is increased by 35.91% for the HBT with new layout. In addition, the thermal resistance is also improved by 13.34%. Because of the improvement of thermal stability and heat dissipation capability, power SiGe HBT with the new layout can operate at higher power level and hence has higher power handling capability over a wide range of operation.