Fabrication of composite x-ray masks by micromilling

Philip J. Coane; Craig R. Friedrich

doi:10.1117/12.250944

13 September 1996 Fabrication of composite x-ray masks by micromilling

Philip J. Coane, Craig R. Friedrich

Proceedings Volume 2880, Microlithography and Metrology in Micromachining II; (1996) https://doi.org/10.1117/12.250944
Event: Micromachining and Microfabrication '96, 1996, Austin, TX, United States

Abstract

An important aspect for the development of micromanufactured components and systems is to reduce the time and cost required to reach the prototype stage. At present, this development typically spans several years. Any fabrication approach which would reduce the cost and time-to-prototype would allow for the more rapid development of design concepts and the more rapid evolution of the design cycle. Direct fabrication of masks for X-ray lithography, by mechanical micromilling, is one potential avenue for rapid, lower cost development. The key process requirements for the fabrication of a typical X-ray mask involves the selection of both substrate and absorber materials. The substrate must provide a mechanically stable support for the patterned absorber without introducing excessive attenuation of the X- ray flux that ultimately reaches the resist surface. Frame supported, thin membranes (such as SiC, C, Si₃N₄, Si) are most often used as well as low atomic number bulk materials (Be). The choice of elemental composition and thickness for the absorber will be largely determined by the resist sensitivity and the X-ray wavelength used. Many process steps are required in order to define the final absorber pattern geometry and will generally involve either additive or subtractive processes. Mechanical micromilling techniques may be used with either a single bulk material which serves the dual role of both substrate and absorber or with a composite structure consisting of a thin gold layer deposited on a thick, low atomic number bulk substrate. Single material masks of aluminum and graphite have been investigated. A composite mask of graphite with a thin layer of sputtered gold has also been investigated. The paper will report on the developmental work for both types of masks and will give results for synchrotron X-ray exposure using these masks. Problems associated with using micromilling as an X- ray mask fabrication method will also be presented.

Citation Download Citation

Philip J. Coane and Craig R. Friedrich "Fabrication of composite x-ray masks by micromilling", Proc. SPIE 2880, Microlithography and Metrology in Micromachining II, (13 September 1996); https://doi.org/10.1117/12.250944

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