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Electron holography on silicon microstructures and its comparison to other microscopic techniques

Two-dimensional dopant profiling is being strongly demanded by the semiconductor industry, and several techniques have been developed in recent years. We compare the performance of electron holography in a transmission electron microscope with other microscopic techniques. The advantages of electron holography are the high spatial resolution of a few nanometres and the direct interpretability of the measured two-dimensional electrostatic potential requiring no simulation. We demonstrate the detection of a 0.5 monolayer of boron in silicon and silicon germanium. We image a 35 nm wide potential dip of 25 mV in a boron-doped specimen, corresponding to detection of a 2 × 1017 B cm−3 dip between peaks of 2 × 1018 B cm−3. Moreover, we illustrate directly by electron holography the existence of a potential barrier at NiSi2 precipitates in silicon, which was predicted earlier by the electron-beam-induced current technique.