Functionalization dependence of the electron beam sensitivity for a conformationally immobile calix[6]arene resist

Calixarenes form a group of compounds that have been studied as high resolution negative electron beam resists. In this work, resists based on a conformationally immobile calix[6]arene molecule were synthesized and their sensitivities measured while the number of attached functional groups was systematically varied. This provided a direct test of the effect of the degree of functionalization on the electron beam resist sensitivity. The synthesis produced two basic molecular conformations: a cone conformer and a 1,2,3-alternate conformer. The number of attached allyl groups was deliberately varied from 0 to 8 allyls in steps of 2 allyls per synthesis. The resulting nine different resists were exposed and contrast curves were measured by atomic force microscopy. The least sensitive were the unfunctionalized calix[6]arenes with threshold doses of about 2 mC / cm 2 . The fully functionalized conformers had threshold doses around 0.1 mC / cm 2 . The sensitivities of both conformers were found to scale directly with the number of attached allyls for the sequence running from 0 to 8 attached functional groups. The molecular weight effect on sensitivity, seen by other groups, appeared only for the heaviest of the nine resists. This conformer, containing six attached functional groups had the highest sensitivity of all those tested. The presence of these two methods for improving sensitivity, partial functionalization of the conformers and higher conformer molecular weight, allows for the possibility of creating a single calixarene resist that is optimized simultaneously for more than one property, such as sensitivity for imaging and etch resistance for pattern transfer.