Evaluation of resists for lithography at 248 nanometers. I. Positive tone resists.

Two types of positive tone resists were lithographically evaluated using the 248.4nm emission of a krypton fluoride (KrF) excimer laser by contact printing. These were polymers such as poly (methylmethacrylate) and modified methacrylate copolymers which undergo chain scission upon absortion of light and the dissolution- inhibition resist systems, such as the commercially available naphthoquinone diazidesensitized novolok-resin-based resists. Our goal was to establish which resists met the sensitivity (100-200mJ/cm(2)) and resolution (0.5micron lines and spaces) requirements for use in a deep UV stepper operating at 248. 4nm. The sensitivities of the degrading polymers, poly(methyl methacrylate) (1.2 J/cm(2)), poly(methyl methacrylate-co-indenone) (450 mJ/cm(2)), poly(methyl methacrylate-co-oximinobutanedione methacrylate) (450 mJ/cm(2)) and poly(methyl methacrylate-co- oximinobutanedione methacrylate-co-methacrylonitrile) (350 mJ/cm(2)) were found to be too low for future stepper use. In addition, their sensitivity to KrF excimer laser emission was 5-7 times less than previously reported for irradiation with standard Hg-arc emission sources. Of all the materials evaluated, only AZ-2415 and its successor Microposit 2400-17 from Shipley Co., exhibited the best match. 4650angstroms thick films of these resists have a sensitivity of 90 mJ/cm (2) when exposed on hard-baked HPR-206 and developed with 3. 5 parts H(2)O and 1 part AZ400K developer concentrate. Increases in sensitivity were obtained by increasing developer strength and/or developer time 0.5micron resolution in readily obtained with AZ-2400 exposed at 248nm.