Nano-oxidation of silicon nitride films with an atomic force microscope: Chemical mapping, kinetics, and applications

We demonstrate that local oxidation of silicon nitride films deposited on conductive substrates with a conductive-probe atomic force microscope (AFM) is a very promising approach for nanofabrication. Scanning Auger microscopy and spectroscopy are employed to verify the chemical changes after AFM-induced oxidation. Furthermore, the growth kinetics are found to have a logarithmic relationship of oxide height versus pulse duration $\mathrm{[h\propto }\ln {\mathrm{(t/t}}_0\mathrm{)].}$ In contrast to rather slow thermal oxidation process, AFM-induced oxidation on silicon nitride has an anomalously high initial oxidation rate (∼30 000 nm/s at 10 V) and a small onset time $t_0$ (∼10 μs). As for the applications in ultrahigh-density recording, an oxide dot array (∼100 ${\mathrm{Gbit/in.}}^2)$ produced by this process is demonstrated. The nitride film patterned by AFM can be utilized as an etching mask to fabricate “subtractive” silicon nanostructures, due to the large etching selectivity of ${\mathrm{Si}}_3{\mathrm{N}}_4:{\mathrm{SiO}}_2:\mathrm{Si}$ in various etchants. With this method, which is entirely compatible with the existing microelectronic processes, synthesis of ultrahigh packing density and ordered nanostructures could become readily achievable.