Impact of emitter fabrication on the yield of SiGe HBTs

Epitaxially-grown, in-situ doped emitters used for SiGe HBT fabrication deliver a couple of advantages regarding device performance. Positive effects on emitter resistance, low-frequency noise, emitter-collector breakdown and manufacturability are observed. Here we report, that the removing of the interfacial oxide between the capping Si layer of the base and the emitter layer may have significant impact not only on the As indiffusion but also on the yield of small transistors. Depending on the device geometry, the high-temperature treatment of the heavily As doped emitter layers has proven as critical process step regarding the defect formation.