Positive-Type Photopolyimide Based on Vinyl Ether Crosslinking and De-Crosslinking

Abstract

A series of different acid value polyimides with carboxyl groups in the ends of main chain was synthesized and used for the three-component photopolymers, consisting of the polyimide, a vinyl ether monomer, and a photo-acid generator (PAG). This polyimide acts as a positive-type resist with the process of prebaking (PB), exposure to light, and post-exposure baking (PEB). The effect of the acid value correspond to molecular weight on the characteristics of the photopolyimide, such as sensitivity and contrast, was investigated. An increase in the acid value and a decrease in the molecular weight enhance the increment of sensitivity based on solubilization rate by cleavage reaction. This positive-type photopolyimide showed a sensitivity of 137mJ/cm² and a gamma value of 2.9.