Exposure mechanism of fullerene derivative electron beam resists

We report systematic studies of the response of C60 derivatives to electron beam irradiation. Films of nine different methanofullerene C60 monoadducts, produced by spin coating on Si surfaces, were irradiated with a 20 keV electron beam. All exhibited negative tone resist behaviour with a sensitivity much higher than that of C60. In the case of derivatives with two polyether chains, the sensitivity was found to be linearly dependent upon the derivative mass, consistent with an increasing electron cross-section for larger derivatives. Features with widths of 20 nm were produced using these compounds, and the etch ratios of the compounds were found to be more than twice those of a standard novolac-based resist.