Real- time Etch Control to Reduce First Wafer Effect in SF6/O-2/Ar Plasma

Real-time plasma controller for SF6/O-2/Ar etching process plasma was developed to reduce first wafer effect caused by cleaning of plasma facing components. After the cleaning of the reactor, the etch rate of silicon decreased 12 % from the etch rate of normal state and increased with repeating etching processes. To reduce the first wafer effect, real-time feedback controller for fluorine density was developed. The controller adjusted O-2 gas flow rate to keep monitored fluorine density constant. With the controller, the etch rate of silicon after the cleaning was kept within 1 % variation.N