Positive-Working Photosensitive Alkaline-Developable Polyimide Precursor Based on Semi-Alicyclic Poly(amide acid), Vinyl Ether Crosslinker, and a Photoacid Generator

A positive-working photosensitive polyimide based on semi-alicyclic poly(amide acid) (PAA), 1,1,1-tris(4-[2-(vinyloxy)ethoxy]phenyl)ethane (TVPE) as a crosslinking dissolution inhibitor and a photoacid generator has been developed. PAA was prepared from pyromellitic dianhydride and alicyclic diamine in N,N-dimethylacetamide (DMAc), which has excellent transparency above 365 nm and good solubility for 1 % sodium carbonate aqueous solution (aq.). The resist from the polymerization solution was formulated with photosensitive additives without isolation of PAA. A 23 μm thick film of the PSPI precursor system containing 25 wt% TVPE, 5 wt% PAG exhibited a sensitivity of 160 mJ/cm2 and contrast of 1.3 when it was exposed to broadband UV light followed by development in a 1 % sodium carbonate aq. at room temperature. A positive image featuring 40 μm line and space patterns was observed by the contact mode.