A novel Ccb and Rb reduction technique for high-speed SiGe HBTs

In this paper, we discuss a novel technique to reduce base resistance (R
_b
) and collector-base capacitance (C
_cb
) for higher F
_max
in high-speed SiGe HBTs. In order to reduce C
_cb
, we first located the origins of the different components of C
_cb
through AC extraction. Then we utilized scanning capacitance measurements (SCM) to examine the shape of the collector-base depletion. We then propose a method to reduce the extrinsic C
_cb
, namely by using reticle enhancement techniques to print a blocking oxide layer to inhibit boron outdiffusion. An additional benefit was the reduction of R
_b
by reducing the base link resistance.