US 9,496,122 B1
Electronically variable capacitor and RF matching network incorporating sameGeneral
US 9,496,122 B1
Electronically variable capacitor and RF matching network incorporating same
Tech Center:
2800 Semiconductors/Memory, Circuits/Measuring and Testing, Optics/Photocopying, Printing/Measuring and Testing
Examiner:
Minh D A
Art Unit:
2844 Electrical Circuits and Systems
Agent:
The Belles Group, P.C.
Inventors:
Imran Ahmed Bhutta
Assignee:
Priority:
01/10/14
Filed:
01/12/15
Granted:
11/15/16
Expiration:
01/10/34
Abstract
An RF impedance matching network includes an RF input coupled to an RF source having a fixed impedance and an RF output coupled to a plasma chamber having a variable impedance. A series electronically variable capacitor (EVC) is coupled in series between the RF input and the RF output. A shunt EVC is coupled in parallel between a ground and one of the RF input and the RF output. A control circuit is operatively coupled to the series and shunt EVCs to control first and second variable capacitances, wherein the control circuit is configured to: determine the variable impedance; determine first and second capacitance values for the first and second variable capacitances; and alter at least one of the first and second variable capacitances, wherein an elapsed time between determining the variable impedance and when RF power reflected back to the RF source decreases is less than about 150 μsec.