Soluble polyimides containing benzimidazole rings for interlevel dielectrics

Abstract

New soluble polyimides with improved adhesion to copper were synthesized from 6,4 ' diamino-2-phenylbenzimidazole (BIA) and 2,2 ' -bis(trifluoromethyl)-4,4 ' -diaminobiphenyI (TFDB) with 3,3 ' ,4,4 ' -benzophenone tetracarboxylic dianhydride (BTDA) via one-pot synthetic method using N-methylpyrrolidone (NMP) as a solvent. Precipitation or gelation did not occur during imidization, and the synthesized polyimides having inherent viscosity values of 0.86-1.74 dL/g were dissolved well in polar aprotic solvents and phenolic solvents. Flexible and fingernail-creasable films were formed on casting. T-g values of the polyimides were in the range of 320-351 degreesC and 5% weight loss in nitrogen occurred above 540 degreesC in all cases. The polyimides containing an equimolar amount of BIA and TFDB showed good adhesion to copper without any adhesion promoters. Water absorption and dielectric constant of the polyimides were in the ranges of 0.57-1.18% and 2.74-2.94, respectively. The polyimides containing a higher content of benzimidazole rings exhibited higher adhesion to copper.