Impedance-matching network using bjt switches in variable-reactance circuits

Abstract

This disclosure describes systems, methods, and apparatuses for impedance-matching radio frequency power transmitted from a radio frequency generator to a plasma load in a semiconductor processing chamber. Impedance-matching can be performed via a match network having a variable-reactance circuit. The variable-reactance circuit can comprise one or more reactive elements all connected to a first terminal and selectively shorted to a second terminal via a switch. The switch can comprise a bipolar junction transistor (BJT) or insulated gate bipolar transistor (IGBT) controlled via bias circuitry. In an on-state, the BJT base-emitter junction is forward biased, and AC is conducted between a collector terminal and a base terminal. Thus, AC passes through the BJT primarily from collector to base rather than from collector to emitter. Furthermore, the classic match network topology used with vacuum variable capacitors can be modified such that voltages do not overload the BJT's in the modified topology.