Oxidation of hydrogen-passivated silicon surfaces by scanning near-field optical lithography using uncoated and aluminum-coated fiber probes

Abstract

Optically induced oxidation of hydrogen-passivated silicon surfaces using a scanning near-field optical microscope was achieved with both uncoated and aluminum-coated fiber probes. Line scans on amorphous silicon using uncoated fiber probes display a three-peak profile after etching in potassium hydroxide. Numerical simulations of the electromagnetic field around the probe–sample interaction region are used to explain the experimental observations. With an aluminum-coated fiber probe, lines of 35 nm in width were transferred into the amorphous silicon layer.

Recent developments in nanofabrication using scanning near-field optical microscope lithography

“…The probe-to-sample separation is approximately 5-10 nm and controlled at a constant-distance mode during scanning. The observed three-peak profile is consistent with a numerical finding by simulating the electromagnetic field around the probe-sample interaction region [14]. As compared, the results obtained from the uncoated probe to the pattern shown in Fig.…”

“…A proper explanation of the size enlargement due to light illumination can be that the induced electric field near the probe-sample region is enhanced by the illumination and resulted in stronger hydrogen (H) depassivation (desorption) and, in turn, to have larger patterned areas or oxidized sizes. The electric field enhancement by the SNOM light illumination should be consistent with the numerical simulation of the electromagnetic field similar to that reported by Madsen et al [14] mentioned earlier. Moreover, Herndon et al [15] also found that the probe oscillation amplitude greatly affects the dimensions of patterns generated and reported a patterned a-Si:H surface without light exposure shown in Fig.…”

“…Fig. 4 shows the AFM image and cross-profile of a single nanoline obtained by Madsen et al [14]. The 54-nm-wide single line is made after the subsequent potassium hydroxide (KOH) etching using an oxidation mask patterned by SNOM with an exposure density of 130 kW/cm 2 .…”

“…The resulting thin oxide layer becomes a mask for subsequent selective etching of the unexposed area. Madsen et al [14] and Herndon et al [15] used Al-coated fiber probes with a 100 nm aperture and an Ar + laser (l ¼ 457.9 nm) light source with an output power of 120 mW to oxidize various patterns on a-Si:H surfaces. Fig.…”

“…Single line patterning by SNOM oxidation using Al-coated fiber probe with 100 nm aperture: (a) AFM image after KOH etch and (b) cross-profile with apparent width of 54 nm (after[14]). …”