An Improved Soft-Error Rate Measurement Technique

Soft errors caused by ionizing radiation have emerged as a major concern for current generation of CMOS technologies, and the trend is expected to get worse. The measurement unit for failures due to soft errors is failure in time (FIT) that represents the number of failures encountered per billion hours of device operation. FIT rate measurement is time consuming and calls for accelerated testing. To improve effectiveness of soft-error rate (SER) testing, the patterns must be targeted toward detecting node failures that are most likely. In this paper, we present a technique for identifying soft-error-susceptible sites based on efficient electrical analysis that treats soft errors as Boolean errors but uses analog strengths to decide whether such errors can propagate to the next stage. Next, we present pattern generation techniques for manifestable soft errors such that each pattern targets a maximal set of soft errors. These patterns maximize the likelihood of detecting a soft error when it occurs. The pattern generators target scan architecture. It is well known that scan test time is dominated by scan shifts, when no useful testing is being done. To improve efficiency of scan-based testing, we extend the functionality of the existing built-in logic block observation (BILBO) architecture to support test-per-clock operation. Such targeted pattern generation and test application improve SER characterization time by an order of magnitude.