Influence of Exhaust Pressure on Photosensitivity in Photo-definable Polyimide

We found unusual exhaust pressure dependency on photo-sensitivity of positive photo-definable polyimide (posi-PDPI) when soft baking PDPI. Higher exhaust pressure of soft baking makes higher photo-sensitivity. This tendency is reverse thing what we expected, because higher exhaust pressure seems to give lower solvent in the soft baking film. We measured the dissolution change of base polymer, and posi-PDPI by using dissolution rate monitoring method.