Electrostatic Discharge Stress Effects on the Performance and Reliability of High Performance NPN SiGe HBTs

We investigate the electrostatic discharge (ESD) stress effects on the performance and reliability of high performance NPN SiGe HBTs which are not designed to be part of an ESD protection scheme, but they may be subjected to residual ESD currents when connected to the IC input pin. Transmission line pulsing (TLP) measurements are conducted in NPNs of various emitter lengths and robust ESD tolerance is demonstrated. TLP testing results in a gradual increase of the forward bias base current which is found to correlate with the TLP stress current density and the device emitter length. Measurements and TCAD simulations provide insights into the physical mechanisms that drive the base current (Ib) increase during the ESD event. Two mechanisms responsible for the base current increase are observed; The first one increases the non- ideal recombination component of Ib and the second mechanism increases the ideal recombination component of Ib. Post-Tlpmeasurements indicate that the second component of Ib increase is largely recoverable. RF characterization results point to either no degradation or minimal degradation of the peak unity current gain frequency
$(\mathrm{f}_{\mathrm{T}})$
. Finally, we report for the first time, results from hot-carrier injection (HCI) stress experiments conducted on NPN SiGe HBTs that are first subjected to non-destructive TLP testing; The hot-carrier reliability of these ESD stressed devices is only marginally affected compared to the reliability of the pristine devices.