Bridge over troubled waters: Critical area based pattern generation

Stringent quality requirements in the automotive sector result in the necessity of targeting additional fault models beyond traditional stuck-at and transition. This paper is concerned with bridging faults, which are well known to require additional tests to detect those which are not detected by traditional tests. To keep ATPG tractable, bridging faults must be extracted from layout to obtain nodes which are physically close together. There are well established methods for such extraction but typically involve complex flows with several tools. This paper describes a much simpler approach using the same layout database that is used for layout-aware diagnosis. The extraction process automatically ranks bridges on critical area so it is simple to truncate the fault list, if necessary. Since each bridge has a critical area it is also possible to provide a weighted critical area based coverage, which is physically more realistic than a simple fault count. The paper describes experimental results, including coverage gains, critical area calculation, and explores physical versus traditional coverage metrics.