Patent ID: 8691057

Claim:
A method for adjusting stress of a sputtered film on a substrate, the method comprising: applying an ac power to at least two sputter targets, including an inner target and an outer target, from an ac power supply having a first terminal connected to the inner target and a second terminal connected to the outer target; and adjusting a stress adjustment circuit to adjust a plasma impedance and allows to control stress in the sputtered film, the stress adjustment circuit having a first polarity connected to an internal shield and a second polarity connected to the first terminal, the stress adjustment circuit adjusting a current flow between the outer target and the inner target, wherein the inner target, the outer target and the internal shield have a coaxial relationship with the inner target located inside the outer target and the internal shield located outside and proximate the outer target such that the outer target is interposed between the inner target and the internal shield, wherein the stress adjustment circuit comprises selecting a resistance value from a plurality of resistance values of a variable resistor of the stress adjustment circuit.