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

IDDQ data analysis using neighbor current ratios

“…Maxwell et al observed that in spite of an order of magnitude difference in I DDQ values, dice had similar signatures, as shown in Fig. 1 [7]. It was proposed that ratios of maximum I DDQ to minimum I DDQ for fault-free chips would have small variation and can be used as a pass/fail criterion.…”

“…This indicates that the SEMA-TECH I DDQ test limit of 5 lA resulted in considerable yield loss. [7].…”

“…Several solutions reduce faultfree I DDQ variation by statistical means [6,7] or graphical display of data [8] while others use correlation between I DDQ and other parameters [9][10][11] to make faulty I DDQ values distinguishable. The current ratios (CR) approach has shown some promising results [7]. However, it is not capable of screening certain defects.…”

CROWNE: current ratio outliers with neighbor estimator

“…The current Ratio of a chip is the ratio of the maximum I DDQ to the minimum I DDQ [6]. It is based on the observation that the intra-die (within-die) variation in I DDQ for fault-free chips is deterministic and relatively constant.…”

“…Several solutions have been proposed in the literature to extend I DDQ test to deep sub-micron (DSM) technologies by reducing variance in the data using graphical means [5] or statistical post-processing of data [6] [7]. Most of these methods rely on the observation that variations in fault-free I DDQ are regular and deterministic and those caused by a defect are random in nature.…”