COMPARISON OF EXPOSURE, BAKE, AND DISSOLUTION CHARACTERISTICS OF ELECTRON-BEAM AND OPTICALLY EXPOSED CHEMICALLY AMPLIFIED RESISTS

Fourier-transform infrared (FTIR) spectrometry and dissolution rate measurements are used to compare chemical-physical mechanisms in electron beam and deep-ultraviolet (UV) optical exposure of a chemically amplified negative crosslinking resist, Shipley XP-8843 (SNR-248). In contrast to optical exposure, up to 20% of the maximum extent of reaction by the melamine crosslinking agent, as measured by the change in peak-to-peak absorbance of the infrared (IR) spectrum at 990-1070 cm-1, was observed after electron beam exposure at nominal exposure doses of 0.5-3-mu-C/cm2. For both electron-beam and optical exposure, the kinetics of the acidcatalyzed crosslinking reactions during the postexposure bake (PEB) were similar and the saturation value of the crosslinking reaction measured by the FTIR was identical. A plot of the dissolution rate versus the degree of crosslinking for normal lithographic doses was single-valued and tended to follow comparable data for optical exposure. When doses > 5-mu-C/cm2 are used without a PEB, the slowing of the dissolution rate is less than expected from IR spectral change. Contrary to typical electron beam exposed negative resists, slightly underexposing small features produced a reentrant profile apparently owing to the high contrast of this resist.