Synthesis and characterization of a photosensitive polyimide precursor and its photocuring behavior for lithography applications

Photosensitive polyimide (PSPI) is of great interest, especially in microelectronic industry and potentially in the photonics and MEMS applications. Here we report on our studies for optimization of synthesis conditions for a PSPI which can be used in lithography. The direct polymerization method using phenyl phosphonic dichloride (PPD) as an activator was used to synthesize poly(amic ester) (PAE) from pyromellitic dianhydride (PMDA), 4,4′-oxydianiline (ODA) and 2-hydroxyethylmethacrylate (HEMA). Main parameters of the synthesis procedure were investigated by differential scanning calorimetry (DSC) analyses. From that, synthesis conditions were determined. Characteristics of the synthesized PAE and the imidized film were studied by the means of DSC, thermalgravimetric analyses (TGA) and Fourier transform infrared spectroscopy (FTIR). The glass transition temperature and the thermal stability of the imidized film were determined. Additionally, formulations of photo-PAE and the Irgacure 369 as photoinitiator were prepared and photocuring was tested by lithography. The results show that the images can be transferred to the PAE film by selective exposure.