Chemistry at Polyimide-Metal Interfaces: In Situ FTIR Studies of Polymer Curing Processes and Thermal Stability

We report in-situ Fourier transform infrared (FTIR) reflection-absorption studies of curing chemistry of polyimide thin films on Crand Cu surfaces, and of the thermal stability of the resulting thin film interfaces when exposed to air at elevated temperatures. The polyimide investigated is based on 4,4'-(hexafluoroisopropylidene)bis(phthalicanhydride)-4,4'-bis(4-aminophenoxy)-biphenyl. The imidization process takes place at temperatures higher than 90°C anda small amount of anhydride is generated during curing. This by-product is converted to imide at temperatures above 250°C. Complete imidization is achieved after curing at 300°C on Cr substrates, while evidence for incomplete curing on Cu is observed under the same conditions. Thermal stability studies with Cr and Cu substrates show that thermal decomposition of thin (∼1000A) polyimide filmsoccurs on Cu when the film is exposed to air at 200°C, while the polyimide is stable on Cr.