A positive‐working photosensitive polyimide based on thermal cross‐linking and acidolytic cleavage

Abstract

A novel positive-working photosensitive polyimide (PSPI) based on a poly(hydroxyimide) (PHI), a crosslinking agent having vinyl ether groups, and a photoacid generator (PAG) was prepared. The PHI as a base resin of the three-component PSPI was synthesized from 4,4 0 -oxydiphthalic anhydride and 2,2 0 -bis(3-amino-4-hydroxyphenyl)hexafluoropropane through ring-opening polymerization and subsequent thermal cyclization. 2,2 0 -bis(4-(2-(vinyloxy)ethoxy)phenyl)propane (BPA-DEVE) was used as a vinylether compound and diphenyliodonium 5-hydroxynaphthalene-1-sulfonate was used as a PAG. The phenolic hydroxyl groups of the PHI and the vinyl ether groups of BPA-DEVE are thermally crosslinked with acetal structures during prebake step, and the crosslinked PHI becomes completely insoluble in an aqueous basic solution. Upon exposure to UV light (365 nm) and subsequent postexposure bake (PEB), a strong acid generated from the PAG cleaves the crosslinked structures, and the exposed area is effectively solubilized in the alkaline developer. The dissolution behavior of the PSPI containing each 11.5 wt % of BPA-DEVE and of the PAG was studied after UV exposure (365 nm) and PEB. It was found that the difference in dissolution rates between exposed and unexposed areas was enough to get high resolution. A fine positive pattern with a resolution of 5 lm in a 3.7-lm-thick film was obtained from the three-component PSPI.

Low‐temperature curable, alkaline‐developable, and negative‐type photosensitive polyimide with high resolution and mechanical properties based on chain extendable poly(amic acid) and photo‐base generator

“…PIs are conventionally patterned with an additional photoresist coated on the PI and lead to a sophisticated manufacturing procedure. In contrast, photosensitive PIs ( PSPIs ) streamline the manufacturing procedure through introducing photosensitivity into PIs or the precursor of PI, poly(amic acid ester) (PAE) and poly(amic acid) ( PAA ) 6‐10 …”

Alkaline‐developable, chemically amplified, negative‐type photosensitive polyimide based on polyhydroxyimide, a crosslinker, and a photoacid generator

“…The introduction of soluble PIs can eliminate the high‐temperature curing step in the patterning process. Moreover, alkaline‐developable soluble polyhydroxyimides (PHIs) can be obtained by the introduction of phenolic hydroxyl groups, as reported in previous articles 8, 12–14…”

“…Moreover, alkaline-developable soluble polyhydroxyimides (PHIs) can be obtained by the introduction of phenolic hydroxyl groups, as reported in previous articles. 8,[12][13][14] We recently reported various photosensitive thermally stable polymers having phenolic hydroxyl groups combined with a crosslinker, 4,4 0 -methylenebis[2,6-bis(hydroxymethyl)phenol] (MBHP), and they showed very high sensitivity. [15][16][17] These findings prompted us to develop a novel photosensitive PHI [chemically amplified photosensitive polyhydroxyimide (PSPHI)] containing MBHP as the crosslinker that would provide higher sensitivity in comparison with previous PSPHIs.…”

Alkaline‐developable positive‐type photosensitive polyimide with high mechanical strength and high resolution based on chain extendable poly(amic acid), thermally degradable cross‐linker and photoacid generator

“…On top of that, direct patterning of PSPIs and PSPBOs without the use of photoresist make the process simpler and thus lowering the manufacturing cost. Poly(amic acid) ( PAA ) derivatives are the most commercially available PSPI for microelectronic fabrication . TSPSPs should meet both of the following two requirements: precise photosensitive pattern formation properties and moderate mechanical endurances (i.e., tensile strength, Young's modulus and elongation) suitable for the application of final products.…”

“…Poly(amic acid) (PAA) derivatives are the most commercially available PSPI for microelectronic fabrication. [6][7][8][9][10] TSPSPs should meet both of the following two requirements: precise photosensitive pattern formation properties and moderate mechanical endurances (i.e., tensile strength, Young's modulus and elongation) suitable for the application of final products. Positive-tone TSPSPs are much more favorable than negative tones for wire-bonding process because of the V-type pattern shape instead of swelling pattern.…”