The utilization of phase-mask technology for the fabrication of an analog micro-optics profile with a thick photoresist was investigated. A two-dimensional phase-grating mask with pi phase depth can produce a desired analog variation of exposure intensity, which allows one to vary the thickness of an analog photoresist after its exposure by a photolithographic stepper and development of the photoresist. A two-dimensional phase-grating mask of square pixels was simulated, designed, and fabricated. The fabrication of analog micro-optics in a thick SPR-220 photoresist by use of this phase mask was also demonstrated.

Fabrication of a thick analog profile with photoresist is a difficult task in photolithography. We demonstrate that a binary phase-grating photomask with an appropriate period and duty cycles is capable of manipulating the exposure illumination in an analog fashion and can be used for fabrication of the desired analog micro-optics profiles on the surface of a thick photoresist. By choosing the proper period and variation of duty cycle of the phase-grating mask, one can create the desired analog intensity of exposure illumination for an optical stepper. This allows the formation of a wide range of analog micro-optics profiles with an SPR 220-7 photoresist. The numerical convolution of the diffraction efficiency curve and resist exposure characteristics is used to predict the final resist profile and also to design the appropriate duty-cycle distribution for the binary phase grating. As a demonstration of this technology, we fabricated a variety of micro-optical elements, such as a positive lens, ring lens, prism, and vortex of approximately 100-200 microm diameter, by using a phase-grating mask fabricated in a poly(methyl methacrylate) electron-beam resist.

An innovative fabrication technique is introduced that is based on multiple-exposure techniques for micro-optics fabrication. This method utilizes various exposure times and combinations of binary and analog photo masks to sculpture complex photoresist profiles. It also demonstrates the fabrication of analog structures from the multilevel structures thus formed by using resist reflow.

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An innovative fabrication technique is introduced that is based on multiple exposure techniques for micro-optics fabrication. This approach is compatible with conventional lithography systems used in Integrated Circuit manufacturing and can be applied to thick and thin photoresists. The additive concept is centered on the idea ofusing multiple exposures to remove the desired amount of resist without resorting to multiple etching steps. This presentation will explain how the additive technique', used with thin and thick resists, will revolutionize our capability to efficiently form refractive lenses and micro-optics for optical beam shaping and transforming. The quality and reproducibility of these elements will also be discussed.