Sensitivity and image quality of resists with electron-beam, ion-beam, and optical exposure

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Abstract
Chemically-amplified resists show promise as patterning materials in many advanced lithography systems including optical, electron-beam and ion-beam systems. In this study, four such resists including IBM APEX-E, IBM ENR, Shipley UVIIHS, and Shipley SAL-601 (ion-beam and electron-beam exposure only) were characterized for the three methods of exposure to determine relative sensitivities, fundamental resolution limits, and diffusivity for each of the above mentioned exposure methods. It was discovered that volumetric exposure doses for ion-beam and electron-beam were roughly equivalent but all resists were more sensitive to optical exposure. This is most likely due to a difference in transfer of energy to the photoacid generator during the exposure. Resolution tests were conducted in ion-beam exposure with simple line/space array patterns. All resists demonstrated patterning capability with resolution limits of 150 nm, 70 nm, 70 nm, and 50 nm for APEX-E, SAL-601, UVIIHS, and ENR respectively. Evidence of a competing cross-linking mechanism in the positive tone resists was discovered from the resolution tests. From a simple electron-beam `post/hole' experiment with varying post-exposure bake times, it was determined that SAL-601 and APEX-E demonstrated the highest level of diffusivity while UVIIHS and ENR exhibited negligible levels of diffusion. The characterization tests demonstrated the suitability of all four resists as good ion-beam patterning materials in addition to their suitability for electron-beam and optical exposure.

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