Investigation Of Virtual Instrumentation-based Automatic Thin Film Resistivity Measurement System

Attention is mainly paid to the measurement of resistivity--an important property of thin film. Owing to apply traditional four-probe method on film sample resistivity measurement, complex corrections are required in order to acquire an accurate result and sample will easily be scratched during the measuring process when using manual four-probe equipment. Therefore, the measurement theory, software and hardware integration method by virtual instrumentation for thin film resistivity automatic system are of important value.Through comparing various resistivity measurement methods, Dual-Configuration method is selected as the fundamental theory of the measurement system. The principles of Dual-Configuration method were carefully analyzed, and the resistivity calculation process was modified to fit the requirement of automatic measurement. It not only simplified the correction for measurement results but also enhanced the reliability and accurate of the system. An automatic measurement system, which is based on visual instrument technology, was built up on PXI system. By using DAQ to control the relay unit, circuit automatic switching which is served as the foundation of Dual-Configuration method was realized. Through practicing servo motor, the position of the probe could be controlled by software and it effectively prevented the scratch of film sample during measurement process. A program which was designed in LabVIEW achieved accurate control of the measurement process and the influence on measurement results stemming from the circuit switch is eliminated. Flaw analyzing module could effectively eliminate the influence resulting from circuit switching.Testing result of nano-magnetic films indicated that, in the range of 1μΩ?cm ~1Ω?cm the measurement results were stable and meaningful. The impact from edge condition and current level followd the theory. The advantage of Dual-Configuration method was obvious in non-ideal conditions. This system met the requirement of measuring the resistivity of thin films.