Nanoscale patterning of an organosilane monolayer on the basis of tip-induced electrochemistry in atomic force microscopy

Abstract
An organosilane trimethylsilyl (TMS) monolayer prepared on silicon (Si) substrate by chemical vapor deposition was successfully applied as a self-developing resist for atomic force microscope (AFM) lithography. The thickness of the monolayer was less than 1 nm. This resist was locally degraded due to electrochemical reactions induced in the junction between a conductive AFM probe and a Si–TMS sample. The generated pattern on the sample was then transferred to the Si substrate by chemical etching using the degraded region as an etching window. Degradation of the monolayer proceeded with both positive and negative sample biases. However, the absolute values of the voltage at which the probe-scanned region began to show etching were +3.0 for Vs>0 and −5.0 V for Vs<0, in a 60% relative humidity air atmosphere. Faster patterning was achieved through increased current flow by applying a higher bias voltage. A 500 μm/s line drawing at Vs=+20.0 V with 2–3 nA was obtained. The number of injected electrons was estimated to be hundreds of times larger than the number of TMS groups in the scanned area. We therefore concluded that only a small part of the current flowing through the probe-sample junction is actually responsible for the degradation.

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