Chemically amplified and conventional resists age in the bottle. Photoactive components drift, viscosity walks, particles and ions can accumulate from packaging, and a manufacturer’s expiration date is the claim that specifications hold under stated storage—not a promise that dose-to-size stays fixed to the last hour. Narrow CD windows often need dose or develop retunes before the printed date, especially after warm storage or late equilibration that lets moisture condense into a cold bottle.
PEB uniformity owns bake plates. Post-exposure queue owns PED. BARC thickness owns the underlayer. This page is resist age and storage discipline as lithography inputs—bottle lot, fridge history, and time-on-track.
Store to the supplier range. Many critical resists want refrigeration (commonly on the order of about 4–10 °C when the label says so); others must stay near room temperature—follow the bottle, not a single plant rule. Bring chilled bottles to bay temperature before opening so condensation does not water the resist. Day bottles or day tanks that sit warm while the bulk stays cold are a deliberate MoC, not tribal practice. Trend CD and coat thickness against resist lot age and storage excursion flags; a dose ladder that “fixes” an aged lot without updating genealogy invents tribal centering.
Post-coat delay and storage of coated wafers are neighboring clocks. An aged resist plus a long PCD stack can move uniformity and proximity behavior in ways that look like scanner drift. Hold lots against bottle open date and coat-to-expose minutes when the signature matches chemistry age rather than tool chamber.
Uncritical layers may run past nominal expiry with metrology proof. Critical layers should not. If the traveler only says “OK to use,” the lithography POR is missing a field the chemistry already filled in.