Impact of passivation layers on enhanced low-dose-rate sensitivity and pre-irradiation elevated-temperature stress effects in bipolar linear ICs

Final chip passivation layers are shown to have a major impact on the total dose hardness of bipolar linear technologies. It is found that devices fabricated without passivation layers do not exhibit enhanced low-dose-rate sensitivity (ELDRS) or pre-irradiation elevated-temperature stress (PETS) sensitivity, whereas devices from the same production lot fabricated with either oxide/nitride or doped-glass passivation layers are ELDRS and PETS sensitive. In addition, removing the passivation layers after fabrication can mitigate ELDRS and PETS effects. ELDRS and PETS effects do not appear to be inherently related to circuit design or layout, but are related to mechanical stress effects, hydrogen in the device, or a combination of the two. These results suggest that proper engineering of the final chip passivation layer might eliminate ELDRS and PETS effects in bipolar integrated circuits.