<title>Effect of ultraviolet curing temperature on the state of stress and mechanical properties of photoresists</title>

Ultraviolet curing, typical during processing of photoresist coatings, often results in residual stress. This stress is critical since it is the driving force for failure in a coating. Increasing the stress usually corresponds to a decrease in the mechanical performance. The source of residual stress was illustrated to be a result of thermal expansion mismatch between the substrate and the coating during the cooling stage following UV cure. The objective of this investigation was to reduce the residual stress by decreasing the ultraviolet curing temperature. A photoresist coating was UV cured at 3 different temperatures and the state of stress and mechanical properties were evaluated. A reduction in the state of stress of the photoresist coating was observed. Using incremental elasticity, this reduction in stress was determined to be primarily a result of decreasing the thermal stresses associated with cooling. When the cure temperature was close to the glass transition temperature, a decrease in the ultimate strength and modulus were observed, which was attributed to a decrease in the efficiency of the crosslinking reaction present during UV cure.