We present a finite-element method to calculate 3-D surface profiles of refractive microlenses fabricated by melting-resist technology (reflow technique). The geometry of the microlenses can be arbitrary. Surface tension and gravity are taken into account. Gravity can have an advantageous influence on the profile form, so that smaller focal spots can be achieved. A simple scaling law is given to estimate the influence of gravity on the profile form for given microlens parameters. We compared various theoretical and measured surface profiles of microlenses fabricated by melting-resist technology and found good agreement. Finally, the usefulness of this method for the design of refractive microstructures for smart masks is shown. © 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)

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Abstract.We present miniaturized, focusing fan-out elements. The new micro-optical elements were fabricated using different technologies: double-sided injection moulding in polycarbonate, double-sided photolithography with subsequent transfer in quartz and direct laser writing in photoresist. The fan-out elements were characterized by measuring their efficiency and uniformity, the surface profiles of the microlenses were measured with a Twyman-Green interferometer. The overall performance of the combined, hybrid elements is demonstrated with intensity distributions recorded in the focal planes.

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We report on the fabrication of high-quality microlens arrays on 4' ' , 6' ' and 8' ' -fused silica wafers. Refractive, pianoconvex microlenses are fabricated by using photolithography; a reflow or melting resist technique and reactive ion etching.A diffraction-limited optical performance (p-v wave aberrations < X/8, Strehl ratio > 0.97) is achieved. Aspherical lens profiles are obtained by varying the etch parameters during the reactive ion etching transfer.The microlens arrays are used for Microlens Projection Lithography (MPL) and within UV-light illumination systems. Microlens Projection Lithography is an innovative technique using KARL SUSS Mask Aligners equipped with an ultra-flat microlens-based projection system. The projection system consists of 500.000 identical micro-objectives side-by-side. Each micro-objective consists of 3 to 4 microlenses. A fully symmetrical optical design eliminates coma, distortion and lateral color. The lens system is frontal-and backside telecentric to provide a unit magnification (+1) over the whole depth of focus. Each micro-objective images a small part of the photomask pattern onto the wafer. The partial images from different channels overlap consistently and form a complete aerial image of the photomask. Microlens Projection Lithography provides an increased depth of focus (> 50 microns) at a larger working distance (> 1 mm) than standard proximity printing. Microlens Projection Lithography allows photolithography on curved or non-planar substrates, in V-grooves, holes, etc. using a KARL SUSS Mask Aligner.