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Occasional electronically erasable programmable read only memory retention failures occurred after thousands of read write cycles. The physical sites of the failed cells were known, but not their location within the individual memory bits. Memory storage transistors have normal gate oxides and thinner tunneling oxide regions for programming. Focused ion beam (FIB) images are brighter when samples are grounded due to a passive voltage contrast mechanism. Thus, using precision etching and polishing to expose memory cells, transistors with leaky (grounded) gate-to-channel characteristics stand out. FIB examination successfully identified the failed transistors and additionally highlighted previously undetected leaky but still functional cells. FIB etching was next used to physically isolate the normal gate and tunneling oxide regions of failed transistors. This proved that the leakage only occurred within the tunnel oxide regions. Further analysis using precision focused ion beam/transmission electron microscopy cross sectioning and atomic force microscopy, identified local thickness reductions in the tunnel oxide which occurred during manufacture. Gate dielectric breakdown failures increase very rapidly with reduced thickness. Calculations showed that unacceptable gate oxide leakage would develop in a time comparable with the observed memory loss failures.

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Quantitative analyses of light elements using energy‐dispersive x‐ray microanalysis (EDX) is increasingly possible since the development of sealed light element ultra‐thin window detectors. However, the computer programs available for quantitative analyses fail for light elements because the correction and background modelling parameters are not accurately known. Therefore, we have developed a simple method of light element quantitative analysis using the peak ratios of two elements as the basis for calibration curves using stable standards. The use of peak ratios avoids the need for accurate ZAF corrections and minimizes many experimental variables. This article describes the criteria for the selection of standards, and the development of the calibration curve in the case of compounds containing oxygen and carbon. The success of the method depends on careful sample preparation and predetermined experimental parameters. The method has been successfully applied to the surface analysis of fresh and oxidized Western and Eastern Canadian coals.

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