Abstract
The trend towards continued miniaturization in integrated circuits has placed enormous demands on both equipment and materials used in the fab lines. As a result, the higher technology fab lines have shifted away from the currently available cyclized polyisoprene negative resists to the novolac-based positive types. At the same time, the desirability of having a high performance negative photoresist has been mentioned in the literature.' We are presenting a new family of organic solvent developed negative photoresists, the key feature of which is the ability to maintain resist images with virtually no swelling. This is demonstrated by the presence of standing waves in the side walls. Being based on a proprietary new chemistry, the new resists provide the advantage of having independent degrees of freedom in such critical properties such as the double bond content, glass transition temperature and aromatic content of the resin. These properties allow for high ultimate crosslink density, limited plastic flow up to 230°C, and high plasma/RIE resis-tance. The photoresist is sensitized for either 365 nm to be used in mirror projection, contact or proximity printing, for 254 rim (deep UV) , or for 405-436 nm to be used in stepper prin-ting. In contact mode the resolution obtained was 1 micron (submicron for under exposure), in scanning projection 1.25 microns. The one micron features were transfered into silicon oxide by RIE with a better than 5:1 selectivity. All these innovations allow for a significant advancement in the state-of-the-art in negative resist microlithography.
