The possibility of the SPM local oxidation nanolithography for Si surfaces is demonstrated in several SPM modes. It is well kown that the feature size of the fabricated Si oxide is controlled by some of the relevant factors such as applied bias voltage between the cantilever and Si surfaces, scanning speed of the cantilever and chemical composition of the atmosphere. In addition, a key feature of SPM local oxidation is the formation of a water meniscus bridging cantilever and Si surface. In tapping mode SPM local oxidation, the cantilever is driven at its resonance frequency and has oscillation amplitude, spring constant and quality factor (Q) of the cantilever's mechanical resonance. We have reported that the size of Si oxide wires is well controlled by the modulation of the oscillation amplitude of the cantilever [1].
Here, we study the tapping mode SPM local oxidation with sub-10 nm resolution by optimizing the applied bias voltage (V), scanning speed (S) and the amplitude of the cantilever (A). The experiments were performed in ambient air. The relative humidity was kept at ~30 %. Doped n+-type silicon cantilever was used. We obtained fabricated Si oxide wire of 8.5 nm in width (V = 17.5 V, S = 250 nm/s, A = 292 nm). In tapping mode SPM local oxidation, it is possible to decrease the size of the water meniscus by enhancing the oscillation amplitude of cantilever. It is considered that in this case, the water meniscus of around sub-10 nm in width can be formed by optimizing the oxidation conditions. Additionally, the amplitude enhancement causes to decrease the average intensity of electric field between the tip and the sample. This also contributes to the improvement of the size controllability with smaller resolution of the fabricated oxide. Therefore, sub-10 nm resolution of tapping mode SPM local oxidation nanolithography is achieved with the modulation of the cantilever dynamics.
References
[1] S. Nishimura, Y. Takemura and J. Shirakashi, J. Phys. Conf. Ser., in print (2007)
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