Ultra-high aspect ratio dielectric etch

An apparatus for etching UHAR features in an etch layer below a carbon based mask, 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;
• an RF bias source providing a signal with a RF frequency between 1 kHz and 10 MHZ;
• a first RF excitation source providing a signal with a RF frequency between 1 MHz and 5 MHz;
• a second RF excitation source providing a signal with a RF frequency between 10 MHz and 40 MHz;
• 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 etch gas source;
• a fluorocarbon polymer gas source;
• and
• a trim gas source;
• and
• a controller controllably connected to the gas source, the RF bias source, the first RF excitation source, and the second RF excitation source and the at least one electrode, comprising:
• at least one processor;
• and
• computer readable media, comprising:
• computer readable code for providing a first selective etch of the dielectric layer with respect to the carbon based mask, where the first selective etch provides a net deposition of a fluorocarbon based polymer, comprising:
• computer readable code for providing a flow of an etch gas from the etch gas source and a fluorocarbon polymer forming gas from the fluorocarbon polymer forming gas source to the processing chamber enclosure;
• computer readable code for energizing the RF bias source, the first RF excitation source, and the second RF excitation source to provide energy, to form a plasma from the etch gas and polymer forming gas and create a bias;
• and
• computer readable code for stopping the flow of the etchant gas and the fluorocarbon polymer forming gas;
• computer readable code for selectively removing the fluorocarbon polymer with respect to the carbon based mask, comprising:
• computer readable code for providing a flow of a trimming gas, from the trim gas source;
• computer readable code for energizing the RF bias source, the first RF excitation source, and the second RF excitation source to provide energy, to form a plasma from the trimming gas and create a bias;
• and
• computer readable code for stopping the flow of the trimming gas;
• and
• computer readable code for providing a second selective etch of the dielectric layer with respect to the carbon based mask, where the second selective etch provides a net deposition of a fluorocarbon based polymer, comprising:
• computer readable code for providing a flow of an etch gas from the etch gas source and a fluorocarbon polymer forming gas from the fluorocarbon polymer forming gas source to the processing chamber enclosure;
• computer readable code for energizing the RF bias source, the first RF excitation source, and the second RF excitation source to provide energy, to form a plasma from the etch gas and polymer forming gas and create a bias;
• and
• computer readable code for stopping the flow of the etchant gas and the fluorocarbon polymer forming gas.