Development of new polymers for 157nm photolithography

As the semiconductor industry moves to ever-smaller feature sizes to maintain competitive stances and reduce cost there is an inevitable need to develop new polymeric materials to meet increasingly harsh processing conditions. These polymers are involved in photoresists, pellicles and optical coatings. In photolithography, the move from 248 and 193 nm to 157nm requires a revolutionary development in these materials. The reason for this is the high energy of 7.9eV at 157nm, which in itself is capable of breaking all of the chemical bonds present within the current materials. Of course some degradation pathways will be favored in these materials. Unfortunately, much of the work on polymer degradation has been focused at =200nm or at much shorter wavelengths leaving a gap of knowledge between. This study seeks to examine the impact of 157nm radiation on polymers and develop an understanding of degradation mechanisms so that new materials can be developed for photolithography. Currently of all of the polymers for 157nm photolithography, the polymers for the pellicle raise the most concern. A pellicle is a thin (∼1 micron) polymer film that protects the reticle from deposition of particle contamination. These pellicles will be required to have exposure lifetimes of 1kJ/cm2 at 157nm; however, existing materials have lifetimes of only a few J/cm2. Additionally the pellicles will have to meet additional requirements for transmission and variance over the lifetime of the pellicle