Impact of inter metal dielectric on the reliability of SiGe NPN HBTs after high temperature electrical operation

The current gain (h/sub FE/) shift of SiGe NPN transistors after High Temperature Electrical Operation (HTEO) stress is delineated in the current investigation. The current gain of transistors (type A), using a high density plasma SiO/sub 2/ for planarization of the inter metal dielectric, decreases with stress time. The decrease of the current gain is caused by an enhanced recombination in the emitter base space charge region. The enhanced recombination results in an increase of the base current Ib. In contrast, the current gain of devices (type B), employing a spin on glass SiO/sub 2/ for planarization, increases due to hydrogen passivation of recombination centers on the polycrystalline Si/crystalline SiGe interface. The passivation of recombination centers causes a decrease of the base current. Also a time-to-failure extrapolation methodology for the creation of recombination centers in the emitter base space charge region is presented.