RESOLUTION AND ETCH RESISTANCE OF A FAMILY OF 193nm POSITIVE RESISTS

Abstract

Our approach to the design of positive, single layer resists for 193nm lithography will be discussed. Phenolic resins, the archetype in positive photoresist materials, cannot be used at this wavelength due to optical opacity. Acrylic polymers combine the required optical transparency at 193nm with easily tailored properties. With a design based on methacrylate terpolymers, we developed a high resolution positive resist for 193nm lithography with excellent imaging at both 193 and 248nm. Our recent work has centered on gaining further insight into methacrylate polymer structure/property relationships, improving the imaging performance and finally increasing the etch resistance. Towards that end, we have employed a class of dissolution inhibitors for 193 nm resists that are combined with methacrylate polymers to provide 3-component resists.[1] A family of 5B-steroid dissolution inhibitors that also increase etch resistance will be described. Imaging and etch performance of four versions of our resist will be disclosed. These methac ylate resists show resolution capability below 0.25 micron, etch rates 20% higher than novolak resins, good environmental stability in contrast to traditional DUV resists and dual wavelength (193/248nm) imaging.