Mechanistic Study of the Nanoscale Negative-Tone Pattern Transfer from DNA Nanostructures to SiO2

We report a mechanistic study of a DNA-mediated vapor phase HF etching of SiO2. The kinetics of SiO2 etching was studied as a function of the reaction temperature, time, and partial pressures of H2O, HF, and 2-propanol. Our results show that DNA locally increases the etching rate of SiO2 by promoting the adsorption of water and that the enhancement effect mostly originates from the organic components of DNA. On the basis of the mechanistic studies, we identified conditions for high-contrast (>10 nm deep), high-resolution (similar to 10 nm) pattern transfers to SiO2 from DNA nanostructures as well as individual double-stranded DNA. These SiO2 patterns were used as a hard mask for plasma etching of Si to produce even higher-contrast patterns that are comparable to those obtained by electron-beam lithography.