Research On Near-field Microwave Measurement Of Thin Film Electrical Properties

With the increasing demand for miniaturization of electronic components,various functional thin-film materials have been widely used in people's daily lives.The research on the electrical characteristics of thin-film materials is an important research field of current science and technology.The accurate measurement of the electrical characteristics of thin-film materials is the basis for developing electronic components.The traditional methods of characterizing the electrical characteristics of thin films have strict requirements on the shape and volume of the sample,and the test results are a common contribution within a certain sample area,and it is difficult to obtain the electrical characteristics of the micro-area.Near-field microwave microscopy uses the near-field scanning of the measured sample,breaking through the limit of diffraction,with a high spatial resolution,can realize nano-scale micro-region imaging and non-destructive detection of thin film materials,so that people can quickly find the defects of the thin film,And then optimize the film production process.Therefore,this paper uses a near-field microwave microscope to study the electrical properties of the film.In this paper,through the derivation of the near field theory and perturbation theory,the conclusion that the interaction between the needle tip and the sample produces perturbation of the energy of the resonant cavity,which in turn affects the resonance frequency change of the resonant cavity,provides theoretical basis for simulation analysis of finite element model,through the image charge method and perturbation theory,the quantitative calculation formula of the dielectric constant based on the quasi-static model is derived,and the calculation results are optimized by subtracting the background noise.Then,the bulk dielectric materials,thin film dielectric materials,and metal thin film materials were simulated and analyzed respectively,The effects of the tip-sample distance,the bulk dielectric material dielectric constant,system structure,the thin film dielectric material dielectric constant,and film thickness on the resonance frequency were studied;the effect of surface resistance on quality factor;the effect of needle tip sample distance,dielectric constant of dielectric sample,and needle tip radius on system spatial resolution,The results show that:The dielectric constant should be measured in the soft contact mode.The quality factor should be used to characterize the surface resistance of the sample.Decreasing tip-sample distance and the tip radius can increase the spatial resolution of the system.it points out the direction for the research of testing methods for exploring the electrical properties of thin film materials based on near-field microwave microscopy.Finally,in order to deduct the influence of distance,this paper proposes a soft contact implementation method,using this method to measure different bulk dielectric materials,the measurement results are consistent with the simulation results,which proves the effectiveness of the method.In order to deduct the influence of noise,the soft contact measurement results of multiple samples were fitted using the quantitative calculation formula of dielectric constant after deducting background noise,and then we measured the measurement error of the soft-contact resonance frequency as±0.228MHz.and the system constant factor A is equal to 0.00294 and the background noise F is equal to 3.78044×10^-4.the system had been calibrated to the dielectric constant test,This paper also measured the metal thin film,the measurement results were consistent with the simulation results,the imaging study of the dielectric thin film and the metal thin film,proved that the near-field microwave microscopy can achieve micro imaging and non-destructive testing.