Wideband Microwave Reflectometry for Rapid Detection of Dissimilar and Aged ICs

Abstract

A wideband microwave method is described as a means for rapid detection of slight dissimilarities and aging effects in integrated circuits (ICs). The method is based on measuring the complex reflection coefficient of an IC when illuminated with an open-ended rectangular waveguide probe, at K-band (18–26.5 GHz) and Ka-band (26.5–40 GHz) microwave frequencies. The spatially integrated reflected electromagnetic signature of a given IC is a function of its internal material properties, geometry and metallic deposition of circuit element, and wire bonds. Consequently, dissimilar (including counterfeit) and aged ICs exhibit markedly different reflection properties than their reference and new (nonaged) counterparts. In addition to measuring spatially integrated complex reflection coefficient (over the waveguide aperture), it is also integrated over the operating frequency band (spectrally integrated) , resulting in significant increase in the robustness of the approach. Root-mean-squared-error, defined as the average Euclidean distance between two reflection coefficient vectors, is used to associate a quantitative metric to the complex reflection coefficient difference between two dissimilar ICs. Measurement results on several sets of ICs having the same package (DIP-14) and different functionalities, similar functionalities with slight differences in specifications, and aged ICs are presented. The results clearly indicate the capability of this method to differentiate among ICs having slight differences in packaging material properties and/or electronic circuitry.