<title>One-step lithography for mass production of multilevel diffractive optical elements using high-energy beam sensitive (HEBS) gray-level mask</title>

Abstract

AB STRACTMicro-optics such as diffractive optics and computer generated holograms are essential components for modern optical design. To reduce their unit fabrication cost we describe a method of reproducing micro-optics in quantities. A true gray-level mask was fabricated in High Energy Beam Sensitive (HEBS)-Glass [1] by means of a single e-beam direct write step. This gray-level mask was used in a optical contact aligner to print a multilevel Diffiactive Optical Element (DOE) in a single optical exposure. A chemically assisted ion beam etching process has been used to transfer the DOE structure from the resist into the substrate [2].Micro-optics such as diffractive optical elements (DOEs) and computer generated holograms (CGHs) are essential optical components in modern optical systems. Fabricating large arrays or elements covering large areas is often very costly. But, cost will be an important factor whenever a new product based on a new technology is introduced into the market place.In this paper we present a new method for reproducing DOEs and CGHs (arrays) in quantities. The new method is compatible with the microfabrication techniques in semiconductor industry and involves first generating a gray level mask. The HEBS-Glass gray level mask can be generated with a laser writer or an electron beam writer, depending on the resolution of the features in the DOE I CGH required and the design software available. This allowed to use all the current software [3,4] previously written in house to support mask making and direct write approaches for the fabrication of DOEs. Due to the inherit sensitivity of the HEBS-Glass to the e-beam, after exposure no resist processing is necessary for mask generation. Then, the gray level mask can be employed in a projection aligner to expose analog photoresist on any environmentally durable substrate, e.g. glass, quartz, semiconductors or metal, one optical exposure for each DOE I CGH (array). After many copies of the mask on the photoresists are developed, many substrates with the developed photoresists will be placed in a chemically assisted reactive ion beam etcher (CAIBE) to simultaneously transfer the microstructures on the analog resists onto the surfaces of the substrates. The number of substrates that can be etched simultaneously will depend on the relative size of the reactive ion gun in the CAIBE and the size of the substrate. The larger is O-8194-2063-8/96/$6.OO SPIE Vol. 2689 / 153 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/22/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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