Cyclic plasma etching of carbon-containing materials

A method for processing a substrate, the method comprising:

• performing a cyclic passivation process in a plasma processing chamber having a plasma source, the cyclic passivation process comprising a plurality of cycles, wherein a cycle of the cyclic passivation process comprises:
• forming a passivation layer by
• exposing the substrate to a first gas comprising boron, silicon, or aluminum without powering the plasma source, the substrate comprising a carbon-containing layer, the first gas interacting with the carbon-containing layer to form the passivation layer,
• purging the plasma processing chamber with a second gas comprising hydrogen, and
• exposing the substrate to a plasma generated from the second gas by powering the plasma source.

A method for processing a substrate, the method comprising:

• performing a plurality of cycles of a cyclic etch process to form a recess in a carbon-containing layer of a substrate loaded in a process chamber, each cycle comprising:
• forming a passivation layer from the carbon-containing layer by
• exposing the substrate to a plasma formed from a first gas comprising a hydrogen-containing gas,
• after turning OFF power to the plasma, purging the process chamber with a second gas comprising boron and a halogen, and
• purging the process chamber with the first gas and turning ON power to the plasma.