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An experimental evaluation of the state of stress and mechanical performance of a polyacrylate photoresist coating
Abstract
This dissertation explores the effect of processing and environmental conditions on the mechanical performance of photoresist coatings. Characterization of the mechanical performance included a comparison of the state of stress with the strength of the coating. Various techniques were compiled and developed to explore the effect of processing and environmental parameters on the state of stress and mechanical properties. Techniques used to determine the stress as a function of temperature changes, swelling, or curing (UV or thermal) were: vibrational holographic interferometry, thermal mechanical analysis (constant strain) as a function of temperature and ultraviolet dosage, and a newly developed technique, membrane deflection. The mechanical properties were examined using standard tensile tests. It was found that a thermal or ultraviolet cure resulted in a significant residual stress (3 to 10 MPa). This stress was compared to the strength of the coating (20-40 MPa). The stress was found to be a result of cooling the sample following cure. A reduction in the temperature experienced during cure resulted in a decrease in the final stress. This reduction in cure temperature, if carried out above the glass transition, did not result in a decrease in the mechanical properties. It was also established that the stress increased linearly as a function of decreasing the temperature. The stress increase as a function of temperature was determined to be $-$0.32 MPa/$\sp\circ$C, with the stress reaching over 45 MPa at $-$65$\sp\circ$C. It was established that the coatings followed a maximum normal stress failure criterion; that is, failure occurred when the 2-dimensional coating stress equaled the ultimate strength. It was also illustrated that the stress due to thermal shock was 10-30% higher than stresses measured during a slow equilibrium cool. A model using linear elasticity was used to describe this phenomenon. It was also shown that swelling the photoresist coatings with water and isopropanol resulted in a complete reduction in the stress. Upon drying, this stress was recovered.
Subject Area
Polymer chemistry|Mechanics|Materials science
Recommended Citation
Taylor, Jeffrey Facer, "An experimental evaluation of the state of stress and mechanical performance of a polyacrylate photoresist coating" (1993). Doctoral Dissertations Available from Proquest. AAI9316721.
https://scholarworks.umass.edu/dissertations/AAI9316721