Apparatus and methods for removing contaminant particles in a plasma process

Abstract

A method and apparatus for operating a plasma processing chamber includes performing a plasma process at a process pressure and a pressure power to generate a plasma. A first ramping-down stage starts in which the process power and the process pressure are ramped down substantially simultaneously to an intermediate power level and an intermediate pressure level, respectively. The intermediate power level and intermediate pressure level are preselected so as to raise a plasma sheath boundary above a threshold height from a surface of a substrate. A purge gas is flowed from a showerhead assembly at a sufficiently high rate to sweep away contaminant particles trapped in the plasma such that one or more contaminant particles move outwardly of an edge of the substrate. A second ramping-down stage starts where the intermediate power level and the intermediate pressure level decline to a zero level and a base pressure, respectively.