Research On Testing Mechanism And Application Of Microwave Near Field Scanning Semiconductor Materials

Near-field microwave scanning microscopy is an emerging technology to study the electrodynamic response of materials on length scales much smaller than the free-space radiation wavelength l.It breaks through the limit of spatial resolution in optical far-field measurement and can further improve the spatial resolution.Therefore,this technology has broad application prospects in the field of wafer measurement of semiconductor chips.It can not only realize the measurement of material properties,but also present the change of material properties in microcosmic,which can direct the design and manufacture of semiconductor chips with higher integration.This problem comes from the project of National Natural Science Foundation of China-microwave high power semiconductor chip thermal state parameter comprehensive analyzer.The mechanism of using microwave nearfield scanning microscope to measure the semiconductor chip is that the microwave signal generated by the near-field probe is electromagnetically coupled with the semiconductor material.The characteristics of the material react on the propagation of the microwave signal in the sample,and the probe feeds back this effect to the measuring instrument.There are two cores in the study of the measuring mechanism,one is the electromagnetic coupling between the probe and the semiconductor material,the other is the embodiment of the coupling in the measuring circuit,which is the coupling is equivalent to the change of the parameters of the components in the circuit,and the theoretical relationship between the material characteristics and the measuring parameters is constructed by the circuit analysis method.This thesis mainly studies three aspects.Firstly,the electromagnetic coupling between the probe and the semiconductor is researched.Based on the concept of near-field and the definition of quasi-static field,the probe tip is treated as a spherical conductor.Using the image charge method in electrostatic field,the field distribution mathematical model of electromagnetic interaction between probe samples under the electric quasi-static field is derived,which solves the mathematical description problem of near-field field field distribution at the probe tip.Then the correctness of the mathematical model is explained from the point of simulation.The first step is to use MATLAB to calculate and image the mathematical model.The second step is to build the physical model of the probe sample in COMSOL and get the potential distribution image through the finite element calculation.By comparing the data point information in the image distribution trend and the orthogonal direction,the correctness of the mathematical model is verified,and explain the characteristics of the rapid decay of the electric potential in the near field.Secondly,the equivalent impedance formed by the coaxial probe and the sample is studied.The electromagnetic coupling of the probe sample reflects the change of the medium efficiency components in the circuit.Generally,the low-order RLC can be approximately equivalent.However,if the measurement result curve is complicated,the higher-order circuit is ordinarily needed.In this thesis,the capacitance model is used to simulate the interaction between the coaxial probe and the sample,and an experimental system based on the coaxial probe is constructed.The causes of different experimental phenomena are analyzed,which provides guidance for further optimization of the experimental system.Finally,the influence factors of probe spatial resolution are studied.The range of the near-field formed by the probe tip in the sample indicates the probe's detection ability,which directly determines its spatial resolution.By studying the relationship between the transverse resolution and the depth resolution of the probe sample in contact with the electric field distribution in the sample,a theoretical method for calculating the spatial resolution of the probe is obtained and verified by COMSOL software.The same method is used to study the spatial resolution of the probe sample in the non-contact case.From the theoretical perspective illustrate the influence of the characteristic length of the probe tip on the spatial resolution is decisive,while the influence of the probe sample spacing on the spatial resolution is small.Therefore,this method can be used to construct the design of probe tip details and the control of tip distance.Through the research of this thesis,a mathematical description method of the electric field distribution in the near field of the probe is proposed,which is verified by the simulation calculation and lays the foundation for the research of the near field test mechanism.At the same time,the equivalent impedance of the coaxial probe and the sample is analyzed,and the coupling effect of the two is simulated by the capacitance model.The experimental system based on the coaxial probe is constructed,and the causes of different experimental phenomena are analyzed.Using the mathematical description method proposed in this thesis,the spatial resolution of the probe is analyzed,and the theoretical method that can estimate the spatial resolution in the design stage of the probe is creatively proposed.The above research work on the near-field microwave scanning microscope technology is only one aspect,and the follow-up research is still a long way to go.