Detection and diagnosis of scan cell internal defects

摘要

A diagnosis technique to improve scan cell internal defect diagnostic resolution using scan cell internal fault models.

主权项

1. A method of scan cell internal defect diagnosis, comprising:
identifying a failing scan chain; determining an upper bound and a lower bound of candidate scan cells in the failing scan chain; and identifying one or more scan cell internal fault candidates in the candidate scan cells based on a failure log and failing scan test patterns associated with the failure log, wherein the one or more scan cell internal fault candidates are for one or more static scan cell internal defects that exhibit static defect behavior but that do not behave as stuck-at faults and also do not behave as transition faults, wherein the static scan cell internal defect is a resistive short or open, and wherein the static defect behavior is characterized by a faulty output value being consistently output from a scan cell output for a respective combination of input values at scan cell inputs, the faulty output value being 0 for at least one combination of input values and being 1 for at least another combination of input values.