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 fT and fMAX respectively.