Study of acid diffusion in a positive tone chemically amplified resist using an on-wafer imaging technique

In this article, the acid diffusion coefficient of Shipley positive tone re sist, UV-III, in an as-spin coated film is determined by using an on-wafer imaging technique. This technique involves incorporation of a pH-dependent fluorescence material, 5-aminofluorescence, into the resist. This fluoresce nce material images the acid distribution by generating fluorescence intens ity contrast under a confocal microscope. Using a laser beam of 488 nm wave length and an objective lens of 100X (with oil immersion), the nominal feat ure sizes of 0.20 mu m can be resolved with a high signal-to-noise ratio. T he acid diffusion coefficient is determined from 1 mu m lines and spaces (1 :9), which are generated by e-beam writing under different post exposure ba king (PEB) times. The value obtained during the PEB is smaller than 3.5X10( -13) cm(2)/s. The resist properties (e.g., sensitivity, resolution, and the rmal stability) are not changed significantly by the low loading of the flu orophore because the dose to size and the printed linewidth are very close to the conditions for resist processing without the fluorophore. (C) 1999 A merican Vacuum Society. [S0734-211X(99)14106-4].