In-situ photoresist strip during plasma etching of active hard mask

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.