Patent ID: 8251011

Claim:
An apparatus which performs a plasma process on a target substrate by use of plasma, the apparatus comprising: an airtight process chamber which accommodates the target substrate; a gas supply system which supplies a process gas into the process chamber; an exhaust system which exhausts an interior of the process chamber and sets the interior of the process chamber to a vacuum state; first and second electrodes arranged in the process chamber to oppose each other, an RF field, which turns the process gas into plasma by excitation, being formed between the first and second electrodes; a first RF power supply connected to the first electrode through a first interconnection and configured to supply first RF power; a first matching circuit arranged between the first electrode and the first RF power supply on the first interconnection and configured to automatically perform input impedance matching relative to the first RF power; a second RF power supply connected to the second electrode through a second interconnection and configured to supply second RF power; a second matching circuit arranged between the second electrode and the second RF power supply on the second interconnection and configured to automatically perform input impedance matching relative to the second RF power; an impedance setting section provided on a shunt line connecting a portion of the second interconnection between the second electrode and the second matching circuit to a grounded line, the impedance setting section being configured to set a backward-direction impedance of circuitry of a second electrode side against a fundamental frequency of the first RF power, which is to be input as an RF component into the circuitry of the second electrode side from the plasma, and the impedance setting section including an impedance change unit configured to change the backward-direction impedance; and a controller configured to supply a control signal for controlling the impedance setting section to cause the impedance change unit to change the backward-direction impedance and thereby to control a characteristic of a plasma process performed in the process chamber, wherein the impedance setting section has a value of an impedance against the second RF power, which is at least twice as large as a value of an RF load impedance formed by the process chamber and the plasma against the second RF power, as long as the impedance change unit is capable of changing the backward-direction impedance.