Impact of BEOL stress on BiCMOS9MW HBTs

Stress investigations have been carried out on SiGe HBTs from STMicroelectronics BiCMOS9MW technology. The strain created by the stack of metal connections impacts the base bandgap of the transistors: from the reference to the denser dummies structure, a 9.1 meV bandgap energy variation is pointed out. Dummies structures were embedded for both DC and HF characterizations which showed a 25% increase for the collector current, and a 21% and 12% increase for the transit frequencies f
_T
and f
_MAX
respectively.