5th INTERNATIONAL WORKSHOP ON ELECTRODEPOSITED NANOSTRUCTURES 7-9 June 2007, Iasi, Romania	ABSTRACTS

Microscale pattern transfer without photolithography on metallic substrates S. Roy and S. Nouraei School of Chemical Engineering and Advanced Materials and Institute of Nanoscale Science and Technology Newcastle University, Merz Court Newcastle upon Tyne, NE1 7RU, U.K E-mail: s.roy@newcastle.ac.uk In a typical micro-fabrication process, micro scale pattern transfer is achieved by using photolithography. In this process, each substrate is covered by a light sensitive resist. The resist covered substrate is then exposed to light through a patterned mask – this either develops or destroys the resist in the areas exposed to light. Thereafter, materials can be plated on or etched off from the exposed areas. This platform technology, therefore, allows micro sized patterns of materials to be transferred on to a substrate. In this work we have developed a process to transfer micro scale patterns on a fully exposed (un-patterned) substrate. The method uses electrochemical means and a specialised electrochemical reactor for pattern transfer. This process uses a metallic material with a resist pattern, which serves as an electrochemical tool. The substrate, which is fully exposed, is placed facing the tool, within close proximity. The tool and the substrate are electrically connected so that the tool is the cathode and the substrate is the anode. Electrolyte is pumped through the system to deliver fresh solution to the anode and cathode as well as remove reaction by products. Our initial experiments, involving copper as the tool as well as substrate material, showed that micro scale patterns could be transferred with good reproducibility. In our reactor, they were placed within a distance of 500 um. We have successfully transferred micro patterns which are significantly smaller than the electrode gap, namely, 50, 100 and 200 um. A specimen 3-D optical profile of a 100 um x 100 um square pattern obtained by this process is shown in the following figure. The steep walls and cubic shape demonstrate the feasibility of the process. Since a single tool can be used to transfer a pattern numerous times, this opens the the possibility of greatly reducing the use of photolithography for pattern transfer on to metallic substrates. We have developed a model which describes the underlying physical phenomemenon of the micropattern transfer process. The model is a reaction distribution model (which, in electrochemical engineering is called a potential or current distribution) model. We used a commercially available modelling software, ElSyCA-2D to understand the critical processes enable micropattern transfer. The model is tested against the experimental data obtained in the experiments. The usefulness of this technique in a variety of microfabrication applications will be discussed.

 
 
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