Thin Film Resistivity Based On Near-field Scanning Microwave Microscopy

With the widespread use of thin film technology in many fields,the precise characterization of its electrical properties has become a key focus and a challenge in the field of testing.In various engineering fields,the properties of thin films influence the performance of various electronic components.Traditional testing methods have limitations in terms of measurement methods and the accuracy of results.Near-field scanning microwave microscopy is a technique that integrates a microwave signal into the scanning probe and keeps the tip of the probe within the near-field range,enabling high-resolution scanning of the sample and characterization of microscopic areas of the sample.Scanning a sample with a near-field scanning microwave microscope enables nanoscale imaging and characterization of the electromagnetic properties of the sample.In this thesis,based on the near-field theory and perturbation theory,a quasi-static model of the pin-tip sample is equated and then obtained,and a theoretical derivation of the quasi-static model is made to lay the foundation for subsequent finite element simulations.At the same time,the near-field scanning microwave microscope test system is equated to a resonant circuit using the set-total parameter model.Several commonly used near-field scanning microwave microscope test structures and the control of the tip sample distance are analyzed.The electric field distribution of the lumped material as well as the thin film material is analysed by means of finite element analysis to model the needle tip sample.The influence of the electrical conductivity of the bulk material,the distance between the needle tip samples and the electrical conductivity of the thin film material,the film thickness and the thin film substrate on the energy variation of the system is also investigated.The effect of conductor and dielectric materials on the resonant frequency and quality factor of the system is also simulated using resonant circuits.The test procedure of the near-field scanning microwave microscope is improved to enable three-dimensional scanning of the sample.A method is proposed to obtain the resistivity of an unknown sample based on the ratio of the quality factors between the samples,based on the variation of the quality factors of the samples with distance.The method is also supplemented by substituting the quality factor ratio of the sample to be measured and the standard sample into the fitted curve based on the resonance frequency variation relationship,and the error between the calculated and theoretical values of the sample to be measured is obtained as 1.7%.Finally,imaging scans were performed on samples with different resistivities and the test system was able to achieve resolutions at the hundred micron level.The imaging quality of the resonant frequency and quality factor data was also analysed and the effect of different scan steps on the imaging quality was investigated.With the use of a probe size of 1 μm,scan steps of 0.05 mm and 0.1 mm had no significant effect on the imaging quality.