The Effect of Process Time Delay for Polyimide in Photolithography Process

摘要

A negative-type photosensitive type polyamic acid ester (PAE) precursor is used in the photolithography process to pattern the wafer and thermally cure the wafer to yield polyimide. The photosensitive polyimide is of great interest in semiconductor industries because it has simplified the complicated photolithography process due its direct patternability. There are some time delays from coat to expose and from expose to develop during the process. The purpose of this paper is to study whether the process time delay gives impact to the polyimide after cure. Two types of PAE precursors which give different thicknesses, were examined on the effect of process time delay. One of the PAE precursors is used to obtain thicker polyimide which is Hum and the other is 3um. The thickness is measured by a profilometer. The chemical bonding and the degree of imidization are determined by using Fourier Transform Infrared (FTIR) spectroscopy. The results showed that for post coat delay, the delay of 30 hours give better degree of imidization and thickness for 3 μm sample and 11 μm sample. For post expose delay, the delay of 10 hours yield a higher degree of imidization and thickness for 3 urn and 11 fim sample.