Base doping and dopant profile control of SiGe npn and pnp HBTs

Incorporation of high doping concentrations and the creation and maintaining of steep doping profiles during processing are key enabler for high level RF performance of heterojunction bipolar transistors (HBTs). In this paper, we discuss results of base doping and dopant profile control for npn and pnp SiGe HBTs fabricated within 0.25 μm BiCMOS technologies. High level of electrically active B and P doping concentrations (up to 1020 cm−3) have been incorporated into SiGe. By adding C to SiGe steep doping profiles have been maintained due to the prevention of dopant diffusion during device processing. It is shown that broadening of P doping profiles caused by segregation could be reduced by lowering the deposition temperature for the SiGe cap. B and P atomic layer doping is shown to be suitable for the creation of steep and narrow doping profiles. This result is demonstrating the capability of the atomic layer processing approach for future devices with critical requirements of dopant dose and location control.