Characterization of AZ PN114 resist for high resolution using electron-beam and soft-x-ray projection lithographies

Abstract

We report on resolution experiments with the negative chemically amplified resist AZ PN114. Using soft-x-ray projection lithography at λ=14 nm, we imaged 0.1-μm lines and spaces in film thicknesses ranging from 50 to 200 nm with both a 20× reduction Schwarzschild camera and a 1× Offner ring-field optical system at doses of ∼10 mJ/cm2. High-resolution electron-beam lithography was used to study the effect of postexposure bake temperature on resist resolution and to characterize a trilayer structure. We found that at temperatures higher than 105 °C 0.1-μm features could not be resolved and patterns were distorted. Using e-beam, we resolved 0.075-μm lines and spaces in AZ PN114 and transferred the pattern to the underlying levels of the trilayer. We measured feature edge-noise for 0.1- and 0.2-μm critical dimensions (CDs) over a wide range of doses. We compared the edge noise and linewidth variation with those measured on samples written in poly(methyl methacrylate) (PMMA). We found 3σ values of 24 nm for AZ PN114 and 9 nm for PMMA. These results suggest that AZ PN114, or a resist of similar sensitivity, may be useful for CDs as small as 0.25 μm. To maintain sufficient linewidth control at smaller CDs in manufacturing, less sensitive resists will probably be required.