Preparation of photosensitive polyimides (PSPIs) and their feasible evaluation for lithographic insulation patterns (LIPs) of integrated circuits (ICs) without negative photoresists

Abstract

A photosensitive polyimide (PSPI) with high glass transition temperature (Tg; 259 ℃), good inherent viscosity (I.V.; 0.31 dL/g), and superb decomposition temperature (Td; 368 ℃) has been manufactured by the appropriate prescription of diamine monomer (i.e. 2,2-bis (3-amino-4- hydroxyphenyl)-hexafluoropropane; APAF), dianhydride monomer (i.e. 4,4′-(4,4′- isopropylidenediphenoxy)bis(phthalic anhydride); BPADA), cyclodehydating agent (i.e. p-xylene), base (i.e. N,N,N-triethylamine; TEA), and photosensitive monomer (i.e. acryloyl chloride; AOC). In order to explore the applying feasibility, we have prepared lithographic insulation pattern resin (LIPR) of integrated circuit (IC) with PSPI (i.e. APAF/BPADA/AOC polyimide), solvent (i.e. N-methyl-2-pyrrolidone; NMP), photoinitiator (i.e. I-305), crosslinking agent (i.e. CLA-1), co-photoinitiator (i.e. I-309) as well as coupling agent (i.e. vinyltrimethoxysilane; VTES) and utilized it without negative photoreist by silicon wafer, i-line (wavelength: 365 nm; optical density: 1200 mW/cm2), and photomask. Experimental results reveal that lab-made LIPR of IC based on PSPI is a promising IC package material with high tensile strength of 106 MPa, excellent adhesion on silicon wafer (i.e. eligible of cross-cut examination), great coefficient of thermal expansion (CTE) of 17.9 ppm/℃, low dielectric constant (Dk) of 3.5, high surface electric resistance of 8.3 × 1011 Ω/sq., low dielectric loss (Df) of 0.01, moderate hygroscopicity of 2.9% (23 ℃, 24 h), and low residual stress of 32.0 MPa.