A circuit breaker for redundant IC systems

On-chip circuit breakers have the potential to significantly increase the yield of VLSICs which incorporate redundant elements by preventing power-ground shorts from destroying the functionality of the entire die. Bipolar transistors are proposed as the switching element to achieve a low voltage drop at high currents without requiring large die area. Two types of IC circuit breakers which are compatible with standard CMOS processing have been studied, and test circuits have been fabricated. The first type of IC circuit breaker uses a lateral bipolar transistor. Measurements of current injected into the substrate indicate that the small fraction of substrate current which escapes from the guard rings around the region of the bipolar transistors is far below that which could result in latchup