Polysilicon emitter bipolarnpntransistors, silicided with platinum, exhibited emitter‐base leakage after the final passivation thermal cycle. Transmission electron microscopy studies revealed platinum silicide (PtSi) spiking through the polysilicon into the emitter‐base region, indicating an apparent release of Pt during high temperature (>400 °C) processing. A technique was developed to study the phenomenon using unpatterned monitor wafers. Observations from a series of tests indicate arsenic dose, Pt thickness, Pt sinter temperature, PtSi capping material, postsilicide formation temperatures, and exposure to oxygen during high temperature treatments (after silicide formation) as the major factors influencing PtSi spiking.