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Fabrication of high aspect ratio submicron gratings on ∼100nm titanium membranes using electron beam lithography
Abstract
We have developed a new technique for fabrication of 1:1 submicron gratings by means of single step electron beamlithography coupled with thin film deposition. The edge profile and the width ratio (line-to-groove) are easily controlled. Metal like gold or copper transmission gratings can be produced by an additional lift-off process. A 30kV electron beam was used to generate 500nm lines on standalone ∼2.3μm thick PMMA/Titanium. The dimensions of fabricated features together with their surface morphology and profiles were investigated by optical microscope and SEM. Low current slow writing coupled with special development is optimized to write structures smaller than the thickness of the resist membrane.
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In this paper, we report a novel process for the fabrication of Fresnel zone plate (FZP) in poly methyl methacrylate (PMMA) using ultra-thin titanium film on carbon as sacrificial layer by electron-beam lithography at 30 keV with proximity correction. The process involves fabrication of free standing structure with high mechanical stability. A study was undertaken to understand the interaction of an electron beam in the resist stack, leading to the optimization of the process for high aspect ratio structures in a single step of exposure and development. The negative tone of PMMA was also utilized to provide mechanical strength to the structure. FZPs of 800 μm diameter were designed and fabricated for a capillary discharge based argon x-ray laser operating at 46.9 nm, to have a focal length of 25 mm. Each FZP had 165 zones with an outer most zone width of 1.34 μm, and a numerical aperture of 17 mrad.
This paper is a description of the stopping power routine utilized in the CASINO program that is based on the experimental measurement of the energy loss function (ELF). In addition, we present an ANSI C standard program that can be used to generate the data needed for the stopping power routine. Both optical and energy loss spectrum (ELS) measurements of the ELF can be used as input to compute the stopping power. For ELS, only the single scattering spectrum is needed. Hence, measurement of the stopping power for a given element or compound of interest can easily be performed and used in the CASINO program. The resulting effect of using these stopping powers in Monte Carlo simulations is generally to increase the backscattering coefficient. Except for carbon, the change of stopping power for pure elements so far compiled is relatively small. In some compounds (i.e., Al2O3 and ZnSe), the discrepancy with the Joy and Luo (1989) expression is significant.
Handbook of microlithography, micromachining and microfabrication: microlithography (SPIE and The Institution of Electrical Engineers
- P Rai-Choudhury
microlithography (SPIE and The Institution of Electrical Engineers
- P Rai-Choudhury