Exposure Tool for Photolithography on non-flat Samples Wilhelmus J. Geerts, Texas State University – San Marcos, DMR In this project we develop a new instrument that will enable us to make small structures on non-flat samples. The micro structures are created in a photosensitive layer, photoresist, with which the sample is covered. Exposure of the photoresist by light will make it soluble in the developer creating process windows. Although similar photo-techniques are widely applied in the printing and high-tech industry, photolithography is not trivial on non-flat samples. The image of the mask projected on the sample is not everywhere in focus, and the photosensitive layer does not have a homogeneous thickness across the sample. The project focuses on three tasks: 1.The development of a fast method to estimate the thickness of the photoresist across the sample [1]. 2.The development of a suitable method to measure the topography of the sample [2,3]. 3.The development of a technique to wrap a two dimensional blue-print (mask) around a 3-dimensional surface structure. [1] Geoffrey Miller, “A Fast Algortihm to determine Photoresist film thickness from the reflection spectrum”, spring [2] Javad R. Gatabi, “Three Dimensional Topography Using LCD Pattern Transfer Method”, spring [3] Bryant Aaron, “Sample topography measurements by a novel image processing algorithm”, spring Holographic projection of two Texas Lone Stars on a perpendicular (a, b) and an inclined surface (c) using a liquid crystal display. a b c

Exposure Tool for Photolithography on non-flat Samples Wilhelmus J. Geerts, Texas State University – San Marcos, DMR Broader impacts: a.Optical Imaging without lenses, lab demonstration for Woman in Science and Engineering Conference (Nova Clara, Arpil 2012): Graduate student Javad Gatabi and PI, Wim Geerts, demonstrate how an LCD display can be used to focus an image on a distant wall without having to move lenses. to a group of female students from San Marcos high school. The demonstration led to an interesting discussion on what limits the speed of traditional zoom lenses, and how performance and form factor can be improved by replacing bulky lenses with large mass and thus large inertia, with light, cheap, thin film liquid crystal devices. b.Solar Cell Interconnect, 2 day Solar Cell Technology Workshop (June 2012): Undergraduate students James Breuleux and Hanu Arava, and graduate student Nelson Simpson, explain process details in the clean room to a group of Taylor high school students. Over the course of two days the students made, and characterized their own photovoltaic devices. The students designed their own interconnect mask for their solar cell. c.Course Development: Four new lab assignments for our Applied Optics course were developed: diffractive optics, optical microscopy, optical instrumentation, and a digital camera assignment (Fourier Optics). The lab assignments make use of Mathcad and optical physlets developed by the University of Barcelona [1]. [1]