Abstract

Scanning capacitance microscopy (SCM), a powerful technique to identify front-end defects, is also helpful in understanding failure mechanisms. This article discusses three front-end doping failure examples that were clearly identified by SCM analysis. The first example was NMOS leakage between drain and source. SCM images showed that N+ junction distortion resulted in effective channel length shortage. The second one was by-field SRAM failure with power leakage. From SCM images, it is clarified that P-well was directly short to P+ in bad die and slight P-well boundary shift to P+ was observed in good die. The third example was regarding low threshold voltage failure analysis. It illustrates that combination of plane-view and cross-sectional SCM analysis could help to diagnose the failure mechanism. The resolution and precision in SCM is better than that in chemical etching combined with SEM technique.

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