Current ratios: a self-scaling technique for production I/sub DDQ/ testing

The use of a single pass/fail threshold for I/sub DDQ/ testing is unworkable as chip background currents increase to the point where they exceed many defect currents. This paper describes a method of using "current signatures" which uses only simple comparisons on the tester, and which automatically scales with process variations which give a wide range of background currents. Dynamic thresholds are used, based on the ratio of maximum to minimum current. Using a single I/sub DDQ/ measurement for each die, upper and lower comparator values are set, against which I/sub DDQ/ for each vector in the suite is compared. Production data is presented to verify the validity of the method.