A thermal design methodology for power SiGe HBTs with non-uniform emitter finger spacing

As an effective and feasible method, the technology of non-uniform emitter finger spacing has been used to alleviate the thermal effects and improve the uneven temperature profile in multi-finger power SiGe HBTs. However, for the HBT with dozens of emitter fingers, designing multiple finger spacing values becomes trivial and time-consuming. In the paper, a new thermal design methodology namely Grouping and Adjusting (GA) method is proposed to shorten design time of non-uniform spacing values. Taking a 30-finger HBT for example, the detailed design procedure of non-uniform spacing values is presented, which shows that the peak temperature is lowed by 8.3K, and the maximum temperature difference is improved by 23.5% when compared with the uniform one. Furthermore, three types of the formulas for designing the spacing values are proposed to meet the different requirement of the temperature profile.