The measurement method of solvent evaporation rate of photoresist liquid film based on monochromatic light interference

Abstract The solvent evaporation rate of the photoresist is a crucial parameter in the spin coating process, influencing process conditions and product quality. When the thickness of the film changes rapidly, the difference between the evaporation obtained through static testing and the actual evaporation during the process becomes significant. Therefore, there is a pressing need for an in-situ method to measure evaporation in situ. This study proposed a method for measuring the solvent evaporation rate of photoresist liquid film based on monochromatic light interference. The hardware of the measurement system consists of an image receiver, a lens assembly, and a light source. The software code for calculating the evaporation rate is based on the principle of relative light intensity. Experimental measurements of the evaporation rate during the drying stage of the spin coating process were conducted using this system. The evaporation rate gradually decreases during the drying process of the liquid film, which is consistent with the characteristics of interfacial evaporation. The experiment demonstrates that this method is convenient and feasible for evaporation rate measurement in the spin coating process.