Etching methods and apparatus and substrate assemblies produced therewith

A method of etching a substrate assembly comprising:

• defining a pattern in a resist layer on a surface of the substrate assembly by exposing a portion of the surface;
• selecting a gas or gas mixture;
• exposing the substrate assembly to a plasma generated in the gas or gas mixture;
• selecting a flow rate of the gas or gas mixture so that exposed portions of the substrate assembly is etched without thinning the resist.

A method for plasma etching an oxide layer formed on a silicon wafer, the oxide layer partially covered with a patterned layer of a resist, the method comprising:

• exposing the oxide layer and the patterned layer of resist to a first gas consisting essentially of CH2F2;
• generating a plasma within the first gas;
• directing ions from the plasma onto exposed portions of the oxide layer;
• adjusting the flow of the first gas so that the exposed portions of the oxide layer are etched such that the oxide layer is etched at a rate at least five times faster than the resist;
• and
• etching the portion of the substrate assembly that is not covered by the resist with a plasma generated in a flow of a second halogenated hydrocarbon containing a second gas that etches the surface of the substrate and the resist layer.