EISEVIER Applied Surface Science 96-98 (1996) 425-429 app(ied zyxwvutsrqponmlkj surface science Excimer laser machining for the fabrication of analogous microstructures K. Zimmer *, D. Hirsch, F. Big1 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR Abteilung Ionenstrahltechnik, Institutfk Obe~~chenmodifizierung, Permoserstrasse 15, D-04303 Leipzig, Germany Received 22 May 1995 Abstract Excimer laser ablation is normally used for micromachining of binary structures, for instance holes or cuts. We investigated new machining techniques for the fabrication of three-dimensional (3D) structures with analogous topology by excimer laser ablation: (i) line scan with a contour mask which correlates with the desired topology and (ii) gray scale mask projection. The structuring methods make use of the dependence of the machined depth (i) on the locally applied pulse quantity or (ii) on the energy density. The details of the methods, the process parameters and the resultant structure properties are discussed. Examples for the structuring of cylindrical and spherical microlenses and microarrays with dimensions in the micron range are given. 1. Introduction There is a growing interest in the field of mi- crosystem technology in three-dimensional (3D) mi- crostructures on surfaces like saw-tooth, spherical or cylindrical topologies with lateral dimensions in the micron range. Many applications in microoptics (e.g. microlenses (arrays), diffractive elements) and mi- cromechanics are possible. Contrary to binary struc- tures where a lot of well-established techniques for production exist (mainly lithographic techniques - photo, e-beam, ion-beam) only a few methods like thermal modification of binary resist structures or dose-dependent beam writing are available for the * Corresponding author. Fax: +4Y 341 235 2595; e-mail: zim- mer@rz.uni.leipzig.de. fabrication of three-dimensional (3D) microstruc- tures 111. Suitable excimer laser irradiation of polymers re- sults in etching (ablation) of the material surface. The ablation process is often used for the fabrication of binary microstructures like holes, cuts or edges. A new challenge is the machining of analogous 3D microstructures. The simplest way to do this is ma- chining in sequential steps by a small spot beam. This technique is based on computer-controlled scan- ning of the focused laser beam across the workpiece surface and applying locally different numbers of laser pulses according to the desired topology depth [4,5]. Due to the small spot normally used in this processing scheme the efficiency of this method is usually low. Although nearly all materials can be structured by excimer laser processing, from the technological 0169-4332/96/$15.00 0 1996 Elsevier Science B.V. All rights resewed SSDI 0169-4332(95)00498-X