High-spatial-resolution scanning capacitance microscope using all-metal probe with quartz tuning fork

The scanning capacitance microscope (SCM) reported here uses a frequency modulation (FM) technique to control the distance between the sample and an all-metal probe. The probe was attached to a quartz tuning fork in a configuration minimizing the perturbation due to the probe. The FM-SCM yields two images of ∂C∕∂V and ∂C∕∂Z signals, where C is capacitance sensed by the probe, Z the probe–sample distance, and V a bias voltage, respectively. On a cross section of a field effect transistor, the two-dimensional p–n junction locus was observed with a spatial resolution better than 5nm in the ∂C∕∂V image. The ∂C∕∂Z images of polysilicon gate electrodes and highly doped source/drain regions have higher contrast than the ∂C∕∂V images.