ANALYSIS AND EXPERIMENTAL CHARACTERIZATION OF SAFE OPERATING AREA OF SIGE HETEROJUNCTION BIPOLAR TRANSISTOR

In Chapter 1, a brief introduction to state-of-the-art SiGe heterostructure bipolar transistors and its evolution is described. The main junction breakdown phenomena are presented. Finally, an overview on trade-offs in the design of this kind of devices is provided. In Chapter 2, a new 2D theoretical model for the bipolar transistor operation under reversal base current conditions is presented. In this operating condition the focusing of the current in the central area of the intrinsic base region limits the Safe Operating Area. A detailed study on the behavior of the bipolar transistor above the open-base breakdown voltage has defined a partial differential equation numerically solved by a finite element software package. The analysis has been extended to include the emitter resistance contribution and high injection effects. By means of this model, the cause of instabilities occurring in the common base output characteristics has been clarified. In Chapter 3, the description of a complete characterization of state-of-the-art SiGe HBT devices is reported. The measurements have been totally realized in department laboratories. In Chapter 4, a new technique for the base resistance extraction of bipolar transistor is presented. This method is the first in literature to capture the bias dependence of the base resistance of modern devices. The new extraction strategy has been applied to STM and Infineon SiGe HBT. The good accuracy of the extraction is demonstrated. In Chapter 5, the design, realization and characterization of an in-house pulse generator required for isothermal characterization is described. Main features and specifications of the proposed system are highlighted. The pulser has been successfully adopted for the characterization of packaged power BJTs and MOS transistors, as well as of on-wafer SiGe:C HBTs.