Operational testing of L.S.I. arrays by stroboscopic scanning electron microscopy

Abstract

The applications of stroboscopic scanning electron microscopy to the observation and testing of L.S.I. and hybrid arrays of operating digital micro-circuits are discussed. In the stroboscopic S.E.M., the spatial distribution of voltages on the surface conductors of a micro-circuit with repetitive pulse excitation up to gigahertz repetition rates can be studied at leisure and in great detail by a combination of two methods. The first is to form an image of the surface voltage distribution at any chosen phase of the operating cycle, which reveals a detailed logical map of the circuit's operation. The second is to display the voltage waveform at any chosen point of the circuit's surface (as in the sampling oscilloscope) which can be used to study, in detail, the electrical performance of the circuit. These techniques are demonstrated by imaging, and analyzing, the performance of a 24-bit dynamic shift register. Their relevance to, and suitability for, computer monitored testing of digital arrays is briefly discussed.