The Results Of Simulation And Experiments Of Microwave Probe In Plasma

In the process of industrial production, especially in the preparation of materials, plasma technology often played an important role in the production of semiconductor.To solve the problems during the diagnosis of plasma parameters by Langmuir probe, plenty of other diagnostic methods were developed, such as spectral diagnosis, microwave diagnosis and etc., among which microwave probe is a non-intrusive diagnostic method with simple structure and high resolution. The microwave probe has two theory bases, one is by measuring the effective dielectric constant of plasma to calculate the plasma density, and the other is by measuring the surface wave formed by microwave on the interface of antenna and plasma, the dispersion relationship of the surface wave could reflect the plasma density.My research contains four parts as followings. Designed a microwave heterodyne circuit system. Utilize the microwave system to replace the Vector Network Analyzer. Study a new phenomenon while applying microwave probe into magnetized plasma in both simulation and experiment. Optimized the high-pass filter plate in front of the antenna array in ECEI system.Basing on the characteristic of the microwave probe, a microwave heterodyne circuit system is projected to improve the measurement accuracy of microwave probe. The usage of 4MHz chop frequency nicely avoid the possibility of immediate frequency signal and the zero-frequency peak overlapping.The resonant frequency of microwave probe could be calculated by analyzing the amplitude and phase of the immediate frequency signal, and then the plasma density is measured. Meanwhile, by IFFT, the pulse signal in time domain could be obtained, thus the spatial position of the reflection point could be derive. Hence, the microwave circuit could replace the Vector Network Analyzer, and fulfil the task of measuring the resonant frequency.In both simulation and experiment methods, the new phenomenon while applying microwave probe into magnetized plasma was studied. In calculation, it is discovered that the resonant frequency of the microwave probe is related to electron cyclotron frequency in magnetized plasma. With the help of CST high frequency electromagnetism module, the plasma frequency, collision frequency and electron cyclotron frequency were defined. In calculation, by making comparison of 8 examples, it is discovered that the resonant frequency of microwave probe in magnetized plasma is only related to pre-formed electron cyclotron frequency. Related experiments were projected and executed. The ICP discharge produced plasma, by placing magnets near the resource, the plasma is locally magnetized. The results of the experiments showed that the resonant frequency is only related to local magnetic field intensity, which strengthened the simulation results.My research about Frequency Selective Surface was presented at the final part of this thesis. In simulation, it is detected that the high pass filter plate is wavelength-sensitive and by filling the waveguide with dielectric, the slope of passband and stopband would be improved.