Patent ID: 11956885
Assignee: MKS INSTRUMENTS, INC.
Field: Chemical engineering (Chemistry)
Classification: CPC H | IPC H

Claim 9:
10. A method for generating plasma in a system that includes a variable-frequency microwave generator connected to a plasma applicator, the method comprising:
disposing a coarse tuner between the microwave generator and the plasma applicator such that the coarse tuner is positioned adjacent to the plasma applicator;
configuring one or more physical parameters of the coarse tuner to achieve coarse impedance matching between the microwave generator and plasma generated by the plasma applicator during both plasma ignition and steady state plasma generation, wherein a load impedance of the plasma generated during plasma ignition and steady state plasma generation is adapted to vary over an impedance range;
flowing a process gas into a plasma tube of the plasma applicator;
setting a frequency of the microwave generator to an initial frequency value to initiate microwave power;
coupling the microwave power to the plasma applicator to ionize the process gas therein;
iteratively fine tuning the frequency of the microwave generator relative to the initial frequency without altering the one or more physical parameters of the coarse tuner, each iteration comprising:
determining if the process gas in the plasma tube is ignited for initiating a plasma at the microwave power corresponding to the tuned frequency; and
discontinuing fine tuning the frequency of the microwave generator if ignition is detected.