COMBINED MILLIMETER-WAVE NEAR-FIELD MICROSCOPE AND CAPACITANCE DISTANCE CONTROL FOR THE QUANTITATIVE MAPPING OF SHEET RESISTANCE OF CONDUCTING LAYERS

We present a dual-frequency electromagnetic scanning probe and apply i t for quantitative mapping of the sheet resistance of conducting films . The high-frequency (82 GHz) mode is used for image acquisition, whil e the low-frequency (5 MHz) mode is used for distance control. We meas ure magnitude and phase of the near-field microwave reflectivity from conducting films of varying thickness and develop a model which accoun ts fairly well for our results. This brings us to a quantitative under standing of the contrast in the microwave near-field imaging using an aperture probe, and allows us to achieve quantitative contactless char acterization of conducting layers with sheet resistance even below 2 O hm. (C) 1998 American Institute of Physics. [S0003-6951(98)01345-X].