Patent ID: 8912633

Claim:
An apparatus for etching features in a silicon layer, wherein the silicon layer is under a hard mask layer, which in turn is under a photoresist layer, comprising: a plasma processing chamber, comprising: a chamber wall forming a plasma processing chamber enclosure; a substrate support for supporting a substrate within the plasma processing chamber enclosure; a pressure regulator for regulating the pressure in the plasma processing chamber enclosure; at least one electrode for providing power to the plasma processing chamber enclosure for sustaining a plasma; a high frequency power source electrically connected to the at least one electrode; a low frequency power source electrically connected to the at least one electrode; a gas inlet for providing gas into the plasma processing chamber enclosure; and a gas outlet for exhausting gas from the plasma processing chamber enclosure; a gas source in fluid connection with the gas inlet, comprising: an opening gas source; and a photoresist stripping gas source; and a controller controllably connected to the gas source and the at least one RF power source, comprising: at least one processor; and a non-transitory computer readable media, comprising: computer readable code for opening the hard mask layer; and computer readable code for stripping the photoresist layer, comprising computer readable code for providing a stripping gas; computer readable code for forming a plasma with the stripping gas by providing a high frequency RF power and a low frequency RF power, wherein the low frequency RF power has a power less than 50 watts; and computer readable code for stopping the stripping gas when the photoresist layer is stripped, wherein the use of low frequency RF power during the stripping of the photoresist layer after opening the hard mask prevents the hard mask from corner rounding or faceting.