| Since its inception,ICP(Inductive Coupled Plasma Source)has played an important role in the field of chemical analysis and is widely used in semiconductor processing and manufacturing industries,thin film processing,plasma etching and other processes.In recent years,with the increasing popularity of wireless technology,more and more devices and systems have adopted RF circuits.However,the plasma terminal load impedance and the RF power output impedance do not match,if the RF source is directly connected to the plasma,there will be a large amount of reflected power in the transmission line and RF source equipment,reduce the efficiency of the RF source equipment,and even burn the RF source equipment.In this paper,the working principle and load impedance characteristics of ICP are studied,an adaptive matching network based on L-shaped structure is designed,and each component module of the prototype is tested to complete the low-power pre-tuning and high-power tuning of ICP and load coil.In the design of this project,the maximum power transfer conditions of the load are first derived,the load coil structure is designed,the load impedance characteristics before and after plasma ignition are analyzed,and the plasma self-inductance mutual inductance model is established to obtain the load impedance value before and after ignition.Based on the difference in the composition structure and adjustment path of L-type network when different load impedances are distributed on the Smith circle chart,the equivalent model of L-type matching network of load impedance is established,and the conditions for the use of the L-type matching network composed of two variable capacitors are derived,and the network parameters are obtained.The specific component values of the matching network before and after ignition are obtained through ADS(Advanced Design System)simulation.Secondly,the automatic matching function in the adaptive matching network is studied,and the design and implementation of the automatic matching function are systematically elaborated.By analyzing the principle of detecting the reflected power of Rogowski coil,the design of Rogowski coil structure and self-integration module was carried out.The resonance method is introduced to analyze the adjustment strategy of variable capacitance when impedance mismatch,and the mutual inductance detection circuit is designed based on the bridge method.When there is reflected power in the transmission line,the mutual inductance detection circuit outputs an induced electromotive force signal proportional to the amplitude and phase of the reflected power,which is used for the control of stepper motor and variable capacitor after conditioning,so that the reflected power continues to become smaller to achieve resonance conditions,and finally complete impedance matching.In addition,the refinement of each module of the matching network is carried out,and the corresponding circuit and PCB(Printed Circuit Board)layout are designed to realize the functions of conditioning control module,execution regulation module and power conversion module,and the functions of each component module of the prototype are tested and adjusted;The prototype was used to perform multiple low-power pre-tuning and highpower tuning and collect data,and the change of plasma load impedance with the increase of input power was analyzed,which verified the correctness of the simplified model and the designed circuit,and showed that the adaptive matching network has important practical significance in ICP work.Finally,the main work of designing adaptive matching network in this paper is summarized,and the next research direction is proposed for some existing problems. |
