Method for plasma etching vertical features in a silicon-based semiconductor layer of a substrate

A method for plasma etching, the method comprising:

• flowing a gas over a substrate in a plasma processing chamber, the substrate comprising:
• an etch stop layer;
• a patterned silicon-based semiconductor layer disposed over the etch stop layer, the pattern comprising lines and openings between the lines, each of the lines having a foot along its base and each of the openings exposing a surface of an etch stop layer, and
• a patterned masking layer disposed over the patterned silicon-based semiconductor layer, the patterned masking layer being a topmost layer of the substrate;
• generating a plasma by ionizing the gas in the plasma processing chamber, the gas comprising:
• a first gas comprising an etchant;
• and
• a second gas comprising a scavenging and deposition agent;
• and
• exposing the substrate to the plasma to remove the foot, the exposing comprising scavenging the etchant while depositing a protective layer over the patterned masking layer.

A method for plasma etching in a plasma processing chamber, the method comprising:

• providing a substrate having a silicon-based semiconductor layer disposed over an etch stop layer and a patterned masking layer disposed over the silicon-based semiconductor layer, the patterned masking layer exposing a surface of the silicon-based semiconductor layer;
• using the patterned masking layer as an etch mask, vertically etching the silicon-based semiconductor layer using a first plasma etch process to form a pattern of lines and expose portions of the underlying etch stop layer, one or more lines of the pattern of lines having a foot along its base, the first plasma etch process comprising:
• generating a first plasma from a first gas comprising chlorine, and
• exposing the substrate to the first plasma;
• and
• vertically etching in situ the pattern of lines using a second plasma etch process, the second plasma etch process comprising:
• generating a second plasma from the first gas and a second gas comprising a compound of hydrogen with Si, Br, I, P, or S, and
• exposing the pattern of lines to the second plasma to remove the foot from the pattern of lines.