Modelling of impurity dopant density measurement in semiconductors by scanning force microscopy

Abstract Lateral dopant profiling has recently been demonstrated using a scanning force microscope (SFM) in electrostatic mode. We have modeled the electrostatic force between a tip and semiconducting sample as a function of bias voltage. We find that the dopant density can be extracted from the force-versus-voltage relationship. This method is analogous to the standard semiconductor characterization technique where the capacitance-versus-voltage relationship is used to determine the dopant density. It is shown that the measurement of AC rather than DC electrostatic forces improves the SFM's ability to provide quantitative dopant profiling in semiconductors. Reducing the gap between tip and sample improves both the SFM dopant sensitivity and the contrast seen between regions of differing dopant density.