Chemical etch using selective ion implantation

A method of chemically etching an underlying material, the method comprising:

• performing a selective modification step comprising
• exciting a plasma comprising hydrogen ions, and
• exposing both a patterned resist layer and the underlying material of a substrate in a plasma etching chamber to the hydrogen ions to form a modified region in the underlying material, the underlying material being exposed through openings in the patterned resist layer;
• and
• performing a chemical etching step comprising
• flowing a halogen-containing etchant gas into the plasma etching chamber, and
• exciting a plasma from the halogen-containing etchant gas to etch the modified region of the underlying material.

A plasma etching system comprising:

• a plasma etching chamber;
• a substrate holder disposed in the plasma etching chamber and configured to support a substrate comprising a patterned resist layer having openings exposing an underlying material;
• a hydrogen ion source fluidically coupled to the plasma etching chamber and configured to provide hydrogen ions in the plasma etching chamber;
• an etchant gas source fluidically coupled to the plasma etching chamber and configured to supply a halogen-containing etchant gas into the plasma etching chamber;
• a source power supply configured to couple source power to gases in the plasma etching chamber;
• and
• a controller operationally coupled the hydrogen ion source, the etchant gas source, and the source power supply, the controller comprising a processor and a non-transitory computer-readable medium storing a program including instructions that, when executed by the processor, perform a method of chemically etching the underlying material by performing
• a selective modification step comprising exciting a plasma comprising the hydrogen ions, and exposing both the patterned resist layer and the underlying material to the hydrogen ions to form a modified region in the underlying material, and
• a chemical etching step comprising flowing the halogen-containing etchant gas into the plasma etching chamber, and exciting a plasma from the halogen-containing etchant gas to etch the modified region of the underlying material.