A large-signal RF reliability study of complementary SiGe HBTs on SOI intended for use in wireless applications

For the first time, a large-signal RF stress study of complementary (npn + pnp) SiGe HBTs on thick-film SOI is performed, and analyses based on device physics are presented, shedding light on the observed failure mechanisms of these C-SiGe HBTs at very high RF input power. Two types of npn SiGe HBTs, low-breakdown voltage (LVNPN) and high-breakdown voltage (HVNPN) devices, as well as a high-breakdown voltage pnp SiGe HBT (HVPNP) in a 250 nm C-SiGe on SOI process are investigated. It is shown that the HVPNP can withstand aggressive RF stress for longer periods of time, compared with the LVNPN and the HVNPN, which succumb to several interesting modes of catastrophic device failure. A case is made for the use of pnp SiGe HBTs in sensitive RF front-ends that may be exposed to non-limited high RF power due to leakages in the transmit/receive (T/R) path or RF reflections.