Low-Temperature Photosensitive Polyimide Processing for Use in 3D Integration Technologies

Abstract

Imidization in solid state and the impact of photo-crosslinking of a photosensitive low-temperature cure ester-type polyimide was studied by in-situ FT-IR spectroscopy. Imidization kinetics depends on the crosslinking degree of the PI precursor. It is confirmed that the full imidization can be achieved at T < 250°C with low exposure doses. The reaction rate within the chemically-controlled region is lowered with increased exposure energy from 0.279 min^-1 to 0.097 min^-1 and to 0.038 min^-1 at 215°C. The diffusion controlled rate constant at 215°C is lowered from 0.00329min^-1 to 0.00298min^-1 and to 0.00170min^-1 with increased exposure energy 0, 200, 600mJ/cm² respectively. This shows that crosslinking has a major influence on the chemically-controlled reaction rate. Thermo gravimetric analysis (TGA) and TGA/FT-IR spectroscopy confirms the in-situ FT-IR results. At temperatures > 300°C further weight losses of volatile components were detected.