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Process improvements in the production of silicon immersion gratings

Published

Author(s)

Cynthia Brooks, Benjamin Kidder, Michelle Grigas, Daniel Jaffe, Ulf Griesmann, Daniel Wilson, Richard Muller

Abstract

We have explored a number of lithographic techniques and improvements to produce the resist lines that then define the grating groove edges of silicon immersion gratings. In addition to our lithographic process using contact printing with photomasks, which is our primary technique for the production of immersion gratings, we explored two alternative fabrication methods. We have investigated anti-reflection (AR) coatings during our contact printing lithography method to reduce the effect of Fizeau fringes produced by the contact of the photomask on the photoresist surface. This AR coating reduces the amplitude of the repetitive errors by a factor of 1.5. Electron beam (e-beam) patterning allows us to manufacture gratings that can be used in first order, with groove spacing down to 0.5 micron or smaller (2,000 grooves/mm), but could require significant e-beam write times of up to one week to pattern a full-sized grating. The University of Texas at Austin silicon diffractive optics group is working with Jet Propulsion Laboratory to develop an alternate e-beam method that employs chromium liftoff to reduce the write time by a factor of 10. We are working with the National Institute of Standards and Technology using laser writing to explore the possibility of creating very high quality gratings without the errors introduced during the contact-printing step. Both e-beam and laser patterning bypass the contact photolithography step and directly write the lines in photoresist on our silicon substrates, but require increased cost, time, and process complexity.
Proceedings Title
Astronomical Telescopes and Instrumentation
Conference Dates
June 25-July 1, 2016
Conference Location
Edinburgh, UK

Keywords

Immersion gratings, diffraction, gratings, infrared, spectroscopy, lithography

Citation

Brooks, C. , Kidder, B. , Grigas, M. , Jaffe, D. , Griesmann, U. , Wilson, D. and Muller, R. (2016), Process improvements in the production of silicon immersion gratings, Astronomical Telescopes and Instrumentation, Edinburgh, UK (Accessed April 15, 2024)
Created June 25, 2016, Updated October 12, 2021