AAS 199th meeting, Washington, DC, January 2002
Session 102. Instrumentation for the Optical and Infrared
Display, Wednesday, January 9, 2002, 9:20am-6:30pm, Exhibit Hall

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[102.07] Improved Results in the Development of Large Silicon Grisms using New Techniques

D. McDavitt, J. Ge, J. Bernecker, S. Miller (Penn State University)

We present new results in the development of large silicon grisms (~ 25x25 mm2). Using photolithography, new etching techniques and post-processing steps we have obtained greatly improved results. Experiments were performed adding ammonium persulfate to the TMAH etching solution. This new method reduced the surface roughness up to ~30% (from rms 32 nm to 22 nm), eliminated all hillock formations and helped maintain constant etch rates. This combined with improved lithography processes has reduced the large-scale defects to less than a few per square inch. Other experiments in post-processing were also carried out. Thin layers of dry silicon dioxide were repeatedly added to and removed from the grating surface producing an additional improvement of ~20% to the surface roughness (from rms roughness of 22 nm to 16 nm) or a ~50% total improvement over previous results. Optical testing of a grating with rms roughness of 16 nm shows less than 1% integrated scattered light at 0.6328 um. We are applying the new techniques in etching an 80x40 mm2 grating on a ~ 30 mm thick substrate to make an anamorphic silicon immersion grating, which can provide a diffraction-limited spectral resolution (R = 200,000) at 2.2 micron.

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The author(s) of this abstract have provided an email address for comments about the abstract: jian@astro.psu.edu

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