US 11,956,885 B2
Method and apparatus for impedance matching in a power delivery system for remote plasma generation
Ilya Pokidov, Winchester, MA (US); Mohammad Kamarehi, Lexington, MA (US); Kenneth B. Trenholm, Salem, NH (US); and Fedir Viktorovych Teplyuk, Lowell, MA (US)
Assigned to MKS Instruments, Inc., Andover, MA (US)
Filed by MKS Instruments, Inc., Andover, MA (US)
Filed on Aug. 19, 2021, as Appl. No. 17/406,378.
Prior Publication US 2023/0057795 A1, Feb. 23, 2023
Int. Cl. H05H 1/46 (2006.01); H05H 1/24 (2006.01); H05H 1/26 (2006.01); H05H 1/28 (2006.01); H05H 1/30 (2006.01)
CPC H05H 1/463 (2021.05) [H05H 1/24 (2013.01); H05H 1/26 (2013.01); H05H 1/28 (2013.01); H05H 1/30 (2013.01)] 23 Claims
OG exemplary drawing
 
1. A plasma-generating system comprising:
a variable-frequency microwave generator configured to generate microwave power;
a plasma applicator configured to use the microwave power from the microwave generator to (i) ignite a process gas therein for initiating a plasma in a plasma ignition process and (ii) maintain the plasma in a steady state process; and
a coarse tuner connected between the microwave generator and the plasma applicator, the coarse tuner located immediately adjacent to the plasma applicator without a coaxial cable connection therebetween, wherein the coarse tuner includes an integrated coupling element for coupling the microwave power from the microwave generator to a microwave cavity of the plasma applicator, and wherein at least one physical parameter of the coarse tuner is adapted to be set to achieve coarse impedance matching between the microwave generator and the plasma generated during both the plasma ignition process and the steady state process, wherein a load impedance of the plasma generated during the plasma ignition process and the steady state process is adapted to vary over an impedance range;
wherein the microwave generator is configured to tune an operating frequency at the set physical parameter of the coarse tuner to achieve at least one of (i) ignition of the process gas during the plasma ignition process or (ii) maximization of the microwave power delivered to the plasma in the steady state process.
 
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.