A new methodology for realistic open defect detection probability evaluation under process variations

CMOS IC scaling has provided significant improvements in electronic circuit performance. Advances in test methodologies to deal with new failure mechanisms and nanometer issues are required. Interconnect opens are an important defect mechanism that requires detailed knowledge of its physical properties. In nanometer process, variability is predominant and considering only nominal value of parameters is not realistic. In this work, a model for computing a realistic coverage of via open defect that takes into account the process variability is proposed. Correlation between parameters of the affected gates is considered. Furthermore, spatial correlation of the parameters for those gates tied to the defective floating node can also influence the detectability of the defect. The proposed methodology is implemented in a software tool to determine the probability of detection of via opens for some ISCAS benchmark circuits. The proposed detection probability evaluation together with a test methodology to generate favorable logic conditions at the coupling lines can allow a better test quality leading to higher product reliability.