Abstract
We propose and investigate a conductivity microscope made possible by improving the eddy current method. The scanning eddy current method using a small probe with a small gap between the probe and sample surface was tried; it could make a map distinguishing fine regions with different electrical conductivity related to electron-defect scattering. A copper–aluminum cold-pressure-welded junction specimen was selected, because it is considered to be a good conductor of electrons and is a commonly used interconnection for large-scale integrated circuits. At the bimetallic joint interface, two stages of 300-nm-thick and 600-nm-thick poor-conductivity layers were detected. These poor-conductivity layers of aluminum are considered to include numerous defects and dislocations that were produced by large plastic flow during the welding process. This conductivity microscope can image a terrace layer of about 3.5 \\micron in width at the welded interface after the layer is annealed for one hour at 470 K, which is comparable to that in the case of scanning electron microscope. The electrical resistivity of this layer was indicated to be lower than that of the aluminum bulk by the estimation of the electrical resistivity. The layer is considered to be an α-copper solid solution one. This instrument is available to detect defects and solid solution.
