Conformationally Immobile Calix[6]arenes as Negative Resists in Electron Beam Lithography
The challenge of creating smaller integrated circuits drives a necessity for novel semiconductor fabrication materials which will facilitate the processing of nanometer-scale features. Literature reports that calixarenes have the potential to meet this challenge, due to their ultrahigh resolution and their process robustness. For this study, the “1,2,3-alternate” and “cone” conformers of Diallyloxy-Bis-/77-Xylenyloxycalix[6]arene were synthesized via a pre-elaborated pathway, purified, and then formulated into negative electron beam resists. The index of refraction (at 632.8 nm) was determined for both compounds. Spin speed curves of various concentrations (w/w) of these compounds were also created. Both compounds were found to form thin, robust films up to 5.0 wt%. These calixarene resists were then exposed using a scanning electron microscope (SEM). All formulations gave qualitative results, as patterns were observed under an optical microscope after development. The sensitivity of the 1,2,3-alternate conformed was found to be relatively good with respect to known literature calix[6]arenes, as well as PMMA. A high contrast of 4.0 was determined for this conformer by constructing a contrast curve. The gel and insolubilization dosages were also determined. Pictures and scans of the features created using these calix[6]arenes were taken using an atomic force microscope (AFM) and the SEM. The width of the highest resolution line was 0.474 i^m, as measured by AFM. Formulations involving the use of a radical initiator (benzoyl peroxide) were exposed for both conformers, and no significant change in pattern quality or sensitivity from nonintiator formulations was observed. The exposure characteristics of the conformationally immobile calix[6]arenes in the electron beam resists described herein were comparable to literature calixarene resist characteristics. Both conformers also show the promise of ultrahigh resolution.
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