Temperature effects on overlay accuracy

A method for reducing overlay error in a photolithographic process, the method comprising the steps of:

• providing a substrate having a permanent layer with a first pattern disposed therein, where the substrate is an instrumented substrate having temperature sensors fabricated therein,
• coating the substrate with photoresist,
• exposing the photoresist to a second pattern, while measuring temperatures at a plurality of different first positions across the substrate, where the temperature is measured at a given position on the substrate simultaneously with the exposure of the given position on the substrate,
• developing the second pattern in the photoresist,
• measuring overlay errors between the first and second patterns at a plurality of different second positions across the substrate,
• correlating the overlay errors with temperatures by position on the substrate,
• determining any relationship indicated between the correlated overlay errors and temperatures, and
• adjusting at least one temperature controlling aspect of the photolithographic process in response to any relationship determined.