Filling the Microscopic-scale Spaces with Polyamic Acid and Polyimide of the PMDA-ODA and PMDA-TFDB Pairs Using Supercritical Carbon Dioxide at Low Deposition Temperature

Abstract

Microscopic-scale trenches that were formed on silicon wafers were filled with polyamic acid (PAA) and polyimide (PI) that consisted of the pyromellitic dianhydride (PMDA)-2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFDB) pair with the aid of supercritical carbon dioxide (scCO₂) and 20 mol% N,N-dimethylformamide (DMF) at 50 and 75°C and at monomer concentrations of 2.0×10⁻² mol/dm³ each. Most of the trenches were well filled with the polymer, which consisted mostly of PAA. Moreover, PAA and PI that consisted of the PMDA-4,4′-diaminodiphenyl ether (ODA) pair was also investigated at deposition temperatures ranging from 50 to 150°C and at monomer concentrations of 2.0×10⁻² mol/dm³ each. The trenches were completely filled with PAA and PI at 50°C. Slight shrinkage of the deposited polymers inside the trenches was observed after thermal imidization.