Light sensitive marginal voltage technique for the location of defects in digital microcircuits

Abstract

The marginal supply line voltages, below which a digital integrated circuit misoperates during a functional test, provide the basis of a simple method of locating defects in circuits which satisfy all the conventional manufacturers' acceptance measurements but are identified as abnormal by their anomalous marginal voltage characteristics. The method employs a lightspot which is scanned across the exposed silicon die of the circuit under test causing a change in the anomalous values of marginal voltage when incident upon the defect site. The technique is described and examples are given to illustrate its practical application.