Nanoscale lithography of silicon dioxide using electron beam patterned carboxylic acids as localized etch initiators

We report on the use of self-assembled monolayers of long chain carboxylic acids as initiators in the high temperature (120°C) HF vapor etching of silicon dioxide thin films and on their use in a unique nanolithographic process we have named chemically enhanced vapor etching. Spectroscopic ellipsometry, Rutherford backscatter spectroscopy, Raman spectroscopy, and multiple internal reflectance infrared characterizations of monolayers of n-octadecyltrichlorosilane and/or myristic and 10-undecenoic carboxylic acids on silicon dioxide are reported. IR data support acid adsorption on the surface via hydroxyl coordination. Raman data provide evidence for the cross-linking of the hydrocarbon backbone upon exposure to the electron beam. Comparative etch behavior of various samples with differing monolayers on the oxide surface provide strong support for the carboxylic acid moiety as the primary reaction initiator for silicon dioxide etching at the temperature employed in these systems. Monolayers of 10-undecenoic acid on silicon dioxide have been patterned using electron beams and subsequent etch processing of the samples has yielded oxide test patterns with linewidths as narrow as 0.1 μm. These systems thus hold promise as novel patterning tools for nanolithography.