Investigation of Hole and Electron Back Injected Tunneling Currents in a Poly-Silicon Emitter Complementary Bipolar Technology

The effects of interfacial oxide on back injected tunneling base current in NPN and PNP transistors are investigated on the same wafer in a silicon complementary technology for the first time. Following the classic treatment of De Graaff and De Groot, electrical measurements were performed on devices with a thin oxide between the poly-crystalline and mono-crystalline regions of the emitter. TEM results show that a 22A interfacial oxide is present in the PNP device and 14A oxide in the NPN devices. Temperature measurements were performed to extract the tunneling probability of back injected holes, Ph, for the NPN and back injected electrons, Pe, for the PNP. It was found that the Pe ~ 5 Ph and was independent of temperature.