Laser interferometric measurement of polymer thin film thickness changes during processing

A simple interferometric technique is described for monitoring thickness changes in solution-cast polymer films as they are dried and cured. This paper follows a freshly spun solution of polyamic acid in NMP as it is converted into a cured polyimide film of 6 μm in thickness. The technique is shown to be nearly quantitative despite the effects of thermal expansion and cure-related refractive index changes.