Optical-softlithographic technology for patterning on curved surfaces

We have established a novel concept of hybrid lithographic technology for non-planar surface patterning. Softlithography and photolithography are properly combined to transfer micro-patterns onto a curved area in an easy, low-cost way. As a first step, a film type of a photomask with micro-metal features is fabricated by the direct pattern transfer technique that has been presented in our preliminary work. Then, a flexible polymer photomask is wrapped on a curved surface to make conformal contact, and a variety of micro-features are formed on the surface via the photolithographic process. We have confirmed the validity of the technique for application in the industrial process by comparing the results transferred via the conventional photolithography with a rigid flat photomask. Subsequently, 3D polymer structures with a high aspect ratio (A/R) are fabricated on curved surfaces using this technique, followed by a discussion on several drawbacks due to the shape of the substrate. Overall, this paper has demonstrated a new method of micro-patterning, which would promise an emerging field of micro-fabrication on non-planar substrates.