Lithographic Properties of Positive Photosensitive Polyimide Insulator by Block Copolymerization.

Abstract

Photosensitive polyimide has enormous potential as a future dielectric interlayer material for potential use in large scale integrated (LSI) circuits. The block copolyimide known as 21-169 was synthesised via a single step polycondensation reaction. This procedure involved reacting dianhydrides with diamines in the presence of γ- valerolactone/pyridine catalyst in a NMP/toluene solvent system at 180°C. This experimentation involves two types of diazonaphtoquinone (DNQ) compound referred to as PC-5 and NT-200. The exposed films were subjected to a developing process using several alkaline aqueous solutions and tetramethylammonium hydroxide (TMAH). A solution of silane coupling reagent was found to be necessary for good adhesion between the polyimide layer and the silicon wafer. In this paper, the resulting products solubility characteristic and pattern shape of the exposed and unexposed areas at 365nm wavelength of light and 700mJ/cm2 were investigated. The contrast γ value between the fully exposed and unexposed area was found to be above 1.1. The PC-5 photosensitive material was found to be an effective dissolution inhibitor for polyimide 21-169 in alkaline developer solution (A0).