VIRTUAL IMPEDANCE AUTO MATCHING BOX

The present invention relates to a method for automatically matching virtual impedance. The method comprises the steps of: (a) determining an input parameter of an RF generator and a load condition parameter of a plasma chamber for each process type, process recipe, and process step of each process recipe; (b) applying an RF ON signal to an impedance matcher based on the input parameter of the RFgenerator for each process step; (c) determining whether an initial set position of a vacuum variable capacitor for load and a vacuum variable capacitor for tuning constituting the impedance matcher is within a matching range; (d) applying an RF OFF signal to the impedance matcher and generating a warning signal indicating the out of the matching range if the step (c) is not satisfied; (e) initiating matching by operating the impedance matcher if the step (c) is satisfied; (f) analyzing an amplitude error and phase error for 50+j0 according to impedance change in each process step, which succeeds the matching, to dete