Fourier transform infrared spectroscopy (FT-IR) was used to study the cure reaction process of an ester-type photosensitive polyimide, PMDA/ODA films coated on silicon wafer substrates. In the in situ high-temperature FT-IR study carried out in vacuum, all the characteristic peaks of imide and the crosslinkable group were observed to decrease gradually with an increase in temperature. The completion of the imidization reaction is at ~ 270 C. Our result shows that the ester-type photosensitive polyimide can be cured at a much lower temperature than previously reported. The imide peak delta as (C, C > NC) at 588 cm-1 was used to follow the imidization process, and the result agrees well with that obtained by using another imide peak upsilon (C-N-C) at 1378 cm-1. The film shrinks by one third during the cure process, and the temperature dependence of the film thickness shows excellent agreement with the "imidization degree".
W. S. Li, Z. X. Shen, J. Z. Zheng, and S. H. Tang, "FT-IR Study of the Imidization Process of Photosensitive Polyimide PMDA/ODA," Appl. Spectrosc. 52, 985-989 (1998)