In-situ SEM Electron Failure Analysis (EFA) of low-resistance samples is challenging because the signal in such experiments is usually masked by the low-frequency noise. Lock-in amplification can significantly improve imaging quality and open access to the signals masked by noise or high offsets.
To apply lock-in amplification in SEM the beam—and thus the signal—is modulated according to a reference frequency, which is usually achieved by an electrostatic beam blanker, installing which incurs long down-time and for some microscopes, is impossible.
In this application note, we introduce an alternative approach: scan-assisted beam modulation for lock-in EFA. It is compatible with any SEM and is integrated into our combined nanoprobing and EFA system with digital lock-in amplification. We show several examples of lock-in RCI on devices with difference resistance, compare this method with in-situ pre-amplification, and discuss its limitations.
Scan-assisted lock-in amplification boosts the RCI workflow by fully removing low-frequency noise typical for two-probe measurements. Moreover, it extends RCI capabilities to low-resistance samples which can’t be analysed otherwise, without significant hardware investments.
Spotting shorts: how to use RCI to find low resistance defects in metal-insulator-metal capacitors
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