Cyclic etch-ash process for semiconductor processing

A method of manufacturing an integrated circuit (IC), the method comprising:

• forming a photoresist layer on a dielectric layer over a semiconductor substrate;
• forming an opening in the photoresist layer, thereby exposing the dielectric layer;
• removing a portion of the exposed dielectric layer using a plasma etch process, the removing stopping on an etch stop layer;
• removing the photoresist layer, the removing including performing a etch-ash process cycle, the etch-ash process cycle including:
• exposing the photoresist layer to a fluorine-based plasma, and then exposing the photoresist layer to an oxygen-based plasma;
• repeating the etch-ash process cycle at least once;
• and
• after removing the photoresist layer, then removing the etch stop layer.

A method of manufacturing an integrated circuit, the method comprising:

• forming a dielectric layer over a semiconductor substrate;
• forming a photoresist layer over the dielectric layer;
• patterning the photoresist layer thereby exposing the dielectric layer through an opening in the photoresist layer;
• etching the exposed dielectric layer thereby forming a trench having an etch stop layer at a trench bottom;
• removing the photoresist layer and leaving a remaining portion of the etch stop layer extending between sidewalls of the trench by performing at least two etch-ash cycles, each etch-ash cycle including:
• exposing the photoresist layer to a first plasma including a fluorine source species;
• and
• then exposing the photoresist layer to a second plasma including oxygen and lacking a fluorine source species;
• removing the etch stop layer;
• filling the trench with a copper-containing metal and forming a metal overburden over the dielectric layer;
• removing the metal overburden by a chemical-mechanical polishing;
• and
• removing a portion of the dielectric layer by the chemical-mechanical polishing.