Optimizing SiGe HBTs technology using small-signal and high frequency noise device's modeling

The rapid expansion of SiGe technologies during the last decade essentially due to civil telecommunication's applications have led Si/SiGe based heterojunction bipolar transistors (HBTs) to excellent performance levels, allowing high frequency low noise circuit designs such as linear low noise amplifiers( RF noise) or also low-phase noise oscillators (LF noise). Among these technologies, the SiGe BiCMOS one integrates digital and RF functions on the same chip. Fast improvements of the technological process have been performed thanks to large efforts allowed to characterization and modeling of the devices. We have investigated on the influence of technological parameters such as Germanium profile, doping level and thickness of the base layer (5 different wafers) on the dynamic and high frequency noise performances to converge towards the optimum technological process (now available with the BiCMOS6G processed by ST microelectronics). We made use of scattering parameters [S] measurements on the devices to extract the electrical parameters of our small signal model. The high frequency noise parameters based on the electrical model (with noise sources added to the junction, resistances) are simulated and compared with the measured noise parameters of the devices. The four noise parameters (Fmin, Rn, and complex Topt) measurements have been performed from 1 GHz to 12 GHz, and the dynamic S parameters measurements have been realized in the 40 MHz-40 GHz range. These models have been used to enable the identification of the limiting parameters on the dynamic performances and on the high frequency noise parameters.