Fault simulation of parametric bridging faults in CMOS IC´s

The authors point out that the simulation of resistive bridging faults inside complex CMOS macrogates requires proper evaluation of resistances, in order to correctly determine realistic fault coverages. Here, an approach applicable to a large category of faults (bridgings, transistor stuck-ons, and node stuck-ats) that give rise to resistive paths between power supply and ground, and hence are all covered by the general term `bridging faults,´ is presented. This method, which avoids the single-fault-injection procedure, fault analysis is performed inside the macrogates aimed to determine the threshold resistance, thus discriminating whether or not a given fault is detectable as a logic error. This analysis is performed inside CMOS macro-gates whose output is observable. To fully characterize the quality of a test sequence with regard to resistive bridging faults, a new definition of fault coverage is presented, because the common concept of fault detection is not applicable to parametric faults