Application of an eddy-current method to measure electrical conductivity of thin films

Abstract

The research objective was the development of subminiature eddy-current transducer(ECT) designed for studying thin films. The possibility of studying the electrical conductivity of thin films of metals as per the amplitude of the eddy-current transducer signal. A subminiature surface eddy-current transducer of the transformer type was developed, and the optimum shape and size of the core and number of inductance coils and turns in them were defined, this provides efficient localization of electromagnetic field. On the basis of eddy-current transducer, a software and hardware complex was developed to control the eddy-current transducer (to generate alternating current of various frequencies, to provide its supply to the eddy-current transducer, to receive a useful signal from transducers to ensure its convenient visualization). The signal working frequency on the energizing winding of the eddy-current transducer was 3 MHz, the signal working amplitude on the energizing winding was 1.1 V. The hardware and software signal processing made it possible to significantly improve the accuracy of measurements. In the developed system, the parameter with information about the monitoring object is the averaged amplitude of the voltage applied by the eddy currents into the measuring winding of the ECT. The algorithm to determine the averaged signal amplitude is given. The dependence between the averaged amplitude of the eddy-current transducer signal and the electrical conductivity of thin films was analyzed and studied. The results of testing of Al, Cu and Zn films were presented, and the electrical conductivity values of the samples were obtained.