Development And Experimental Research Of The Auto Impedance Matcher In The Rf Power

After radio frequency technology enters into coating technology, the problem of RF matching needs to solve. The power of RF power source should be used in the coating technology as possible as it can. Input power of system has an direct influence on concentration and pressure of plasma and the quality of coating,which has a relation with process level. In some condition, system load changes with time went by,which makes it necessary to have an auto impedance matching. But it is dominated by manual matching in China.The development of automatic matcher is always in the position of bottleneck. Therefore,the research on the technology of auto matching is has very important significance.This thesis investigates RF power supply impedance matcher RS-500 which matches with RF plasma enhanced CVD coating machine in lab.It has a research on principle and design of manual matching. Transfer the signals that were transferred into electric meters into PC to carry out automatic control in order to realize auto matching. This thesis regards the detailed design of power detection module and control simulation for mathematical model built by system as key research content.Combined with the analysis and research on other modules of relative perfect function and relative mature technology,such as driven module,signal transformer module etc,this thesis puts forward relative perfect design methods about RF power supply automatic impedance matcher.There is a relative whole recognition in general structural design and principle.The design of electric circuit in this thesis is based on matching principle.It means that with the change of plasma resistance in coating,impedance matcher realizes conjugated impedance matching of the whole transmission circuit,which makes sure that incident power is always maximal while reflected power is minimal.All is for the quality of coating.The change of plasma can be treated as an impedance in the circuit.Matcher realizes conjugate match in the whole transmission circuit by regulating two variable capacitor in self-module.The method of determining conjugate match is detecting incident power and reflected power,making sure incident power is maximal while reflected power is minimal. Power can be characterized by voltage,current and phase between them.That is,P=U*I*cosï¿ .In power detecting module,the selection of current transformer of measuring current is Rogowski coil that is better than traditional coil. The selection of voltage transformer is capacitive voltage transformer.The phases of them is fixed in the coating.So the phase between them is unchanged.There is no need to measure.Directional coupled device is made up of current transformer and voltage transformer.It is the key to power detecting module.The thesis analysises the circuit of power detecting module and puts forward reasonable designing scheme.Then the thesis analysises other modules and puts forward feasible designing scheme.At last,the thesis builds up the mathematic model of transmission circuit.Using PID to control and simulate by MATLAB,the thesis obtains effective controlling method.