Imaging capabilities of resist in deep ultraviolet liquid immersion interferometric lithography

Abstract

Liquid immersion lithography (LIL) extends the resolution of optical lithography to meet industry demands into the next decade. Through the use of exposure media such as purified water (n of 1.44 at 193nm), it is possible to reduce minimum pitches compared with traditional air/vacuum exposures media by a factor of as much as 44%—a full technology node. Beyond this simple observation, there is a good deal of work necessary to fully understand the impact of LIL immersion lithography on a lithography processes. This article addresses the impact of water immersion on the imaging capabilities of different resist formulations. All resists were evaluated by imaging dense line-space structures at a 65-nm half-pitch both in air and with water immersion. Studies of dense 65-nm lines made by immersion imaging in HPLC grade water with controlled variations in resist components were performed. Significant differences were observed and will be discussed.