High Temperature Annealing induced recovery of Hot-Carrier degradation in High Performance NPN SiGe HBTs

We investigate the possibility of any spontaneous recovery of the hot-carrier injection (HCI) induced degradation in NPN SiGe HBTs as well as the recovery mechanism of the hot carrier damage when the SiGe HBTs are subjected to a high temperature annealing (bake) environment. In our study, devices were HCI stressed under the forward-active/mixed mode as well as the reverse emitter-base (EB) mode and were subsequently stored unbiased under room temperature for ten years. Characterization of these devices at the end of the ten-year storing period showed no recovery of the HCI damage. On the other hand, we observed significant levels of recovery when we thermally cured these same devices even at a low anneal temperature of $180^{\circ} \mathrm{C}$. The recovery was characterized as a function of the anneal temperature, the annealing time duration and the pre-anneal level of HCI damage. The measured recovery kinetics for the devices that were stressed under the forward-active/mixed mode and those that were stressed under the reverse EB mode are, within the experimental uncertainty, the same, suggesting that the same type of defects are activated during stress in both cases. The recovery rate exhibits Arrhenius behavior, and the extracted activation energy values for the forward-active/mixed mode and reverse EB mode stressed and attributed to the re-passivation of Si dangling bonds by hydrogen atoms.