We present a method for reproducing diffractive optical elements in quantity. The method is compatible with VLSI microfabrication techniques and involves generating a gray-scale mask. The gray-scale mask is employed in an optical aligner to expose an analog photoresist on any environmentally durable substrate, e.g., glass, quartz, semiconductor, or metal, one exposure for each diffractive optical element. After copies of the mask on the photoresist are developed, many substrates can be processed in parallel in a chemically assisted ion-beam etcher to transfer the microstructures on the analog resists simultaneously onto the surfaces of the substrates.

Articles you may be interested in X-ray mask fabrication technology for 0.1 μm very large scale integrated circuits General aspheric refractive micro-optics fabricated by optical lithography using a high energy beam sensitive glass gray-level mask A method for mass fabrication of environmentally rugged monolithic diffractive optical elements ͑DOEs͒ is demonstrated. A one-step optical exposure, with a gray level mask, was used to produce analog resist profiles that were transferred into their substrates using chemically assisted ion beam etching in a single etching step. The described procedure allows mass fabrication of DOEs without the tedious multiple exposure and etching steps commonly used in multilevel DOE fabrication. To generate a multilevel DOE in an optical substrate, only a single exposure using a gray level mask and a single etching step are necessary. The fabrication method presented will reduce processing time and increase manufacturability, which will result in a general cost reduction per element.

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

Polymeric films deposited from the vapor of C&16 by the surface-photopolymerization technique are electrically and mechanically continuous on various substrates when very thin. The thickness of the films depends upon irradiation time with wavelengths in the region 2000-3000A. Re-irradiation in oxygen (air) of the polymeric films with light of these low wavelengths leads to patterned removal of the films. Since films 500A thick and less can resist etchants for various substrates, a new and extremely thin positive photoresist system is possible. Resolution of etched substrates to lines a few microns wide has been demonstrated. If the polymeric films from C4C16 are deposited from the monomeric vapor at lower substrate temperatures they are soluble in various solvents. Reirradiation with UV light with the films in vacuum produces a patterned fixing of the polymer with respect to acetone. A negative photoresist system is therefore possible. Again, films of thickness 500A and less can resist various etchants such that substrates can be etched to high resolution.

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