Analysis And Modeling Of Self Heating In Silicon Germanium Heterojunction Bipolar Transistors

Silicon Germanium (SiGe) hetero junction bipolar transistors (HBTs) have established itself as strong technology contender for a host of circuit applications including analog, mixed signal and Radio Frequency (RF). Due to the effect of technology scaling, self heating plays a significant role in the performance of SiGe HBTs. This thesis paper does an extensive analysis on the effect of self heating and uses different methods to extract the self heating parameters. An expression for thermal resistance considering thermal conductivity as a function of temperature is derived. Also a method to convert a multi pole thermal model to a single pole thermal model is introduced.The VBIC (Vertical Bipolar Inter Company) model is used for all the simulations. Simulations are performed using Cadence and ICCAP (Integrated circuit characterization and Analysis Program) tools. Measurements are done using Agilent 4142 DC source and Agilent 6000 series oscilloscope. National Semiconductor's SiGe HBTs from their CBC8 process are used for getting real data.