Detection of lens anti-reflective coating decay by undesired residue detection

A semiconductor fabrication equipment assembly comprising:

• one or more lenses having a field of view;
• an anti-reflective coating on a sidewall of the one or more lenses and having decay;
• a mask positioned relative to the one or more lenses such that a scribe line of the mask is in the field of view;
• a stage;
• and,
• a semiconductor wafer placed on the stage, positioned under the one or more lenses, and having a negative photoresist,
• such that photoresist residue contributed by the negative photoresist and detectable on the scribe line of the mask through the one or more lenses correlates to the decay of the anti-reflective coating.

A method comprising:

• positioning a mask over one or more lenses of semiconductor fabrication equipment, the mask having a scribe line within a field of view of the one or more lenses;
• positioning a semiconductor wafer under the one or more lenses of the semiconductor fabrication equipment, the semiconductor wafer having a negative photoresist that contributes photoresist residue viewable on the scribe line of the mask;
• detecting photoresist residue on the semiconductor wafer as viewable on the scribe line of the mask, the photoresist residue detected resulting from stray light reflected by an anti-reflective coating of the one or more lenses as a result of decay of the anti-reflective coating;
• and,
• correlating decay of the anti-reflective coating of the one or more lenses of the semiconductor fabrication equipment to the photoresist residue detected on the semiconductor wafer as viewable on the scribe line of the mask.