In this paper, we present a numerical modelling of a NPN SiGe heterojunction
bipolar transistor (HBT) realized in an industrial 0.35 µm BiCMOS
process, using our own software simulator “SIBIDIF”, taking into account
some electrically active defects in the HBT device. The electric
performances of this device can be penalized by the presence of defects
inherent to the complex structure shrinking. For our devices, most of these
relevant defects are located at the vertical interface between the spacers
and the polysilicon emitter, due to the Reactive Ion Etching (RIE) process
step. Nevertheless, their localization, as well as theirs effective density
or their capture section, have an influence on the electric characteristics
of the HBT's. As a check, we find some good agreement between our simulated
results and some experimental ones. Our work is focused on the
identification of defects responsible for the current fluctuations at the
origin of low frequency noise or Random Telegraphic Signals in industrial
submicronic BiCMOS technologies. Gummel characteristics are simulated in
order to identify generation-recombination or trap assisted tunnelling
process in the base current. We have shown that devices having an excess
base current present random discrete fluctuations on the base current.