Layout Design of Multi-finger Power SiGe HBTs for Thermal Stability Improvement

This paper proposes the layout design of multi-finger power SiGe HBTs with non-uniform finger spacing to improve the thermal stability. Two types of 20-finger SiGe HBTs with uniform and non-uniform finger spacing are fabricated. Experimental results shown that, for the HBT with non-uniform finger spacing, the power level for thermal regression is 22.8% higher than that of the uniform one, which contributes to the improvement of the maximum temperature and the non-uniformity of the temperature profile in the device. Therefore, the temperature profiles of HBTs are simulated to directly show thermal stability and verified by the experiment result. Basing on the verified simulation, a further optimum layout design of HBT with non-uniform spacing is proposed. It is shown that the maximum temperature difference is improved by 79.28% for the further optimum HBT, when compared with that of HBT with uniform finger spacing. These results indicate that optimizing the layout of HBTs with non-uniform finger spacing is very useful for improving the thermal properties of power HBTs.