Fine pitch grids for an x-ray solar imaging spectrometer fabricated by optical lithography and XeF2 etching

Reid A. Brennen; Michael H. Hecht; Dean V. Wiberg; Steven Manion; William D. Bonivert; Jill M. Hruby; Kristofer S. J. Pister; Ezekiel J. Kruglick

doi:10.1117/12.222651

26 September 1995 Fine pitch grids for an x-ray solar imaging spectrometer fabricated by optical lithography and XeF₂ etching

Reid A. Brennen, Michael H. Hecht, Dean V. Wiberg, Steven Manion, William D. Bonivert, Jill M. Hruby, Kristofer S. J. Pister, Ezekiel J. Kruglick

Author Affiliations +

Proceedings Volume 2640, Microlithography and Metrology in Micromachining; (1995) https://doi.org/10.1117/12.222651
Event: Micromachining and Microfabrication, 1995, Austin, TX, United States

Abstract

We have developed fine pitch, sub-collimating X-ray grids for an instrument in the High Energy Solar Spectroscopic Imager (HESSI), a proposed NASA mission. In addition to high- energy X-rays, the instrument requires collimation of photons with energies of less than 4 keV such that free-standing grids are required that have no material between the grid slats. We have fabricated 25 micrometer thick gold grids that can collimate photons from visible light up to 30 keV X-rays. They are 55 millimeters in diameter and have 200 micrometer thick silicon support structures. The fabrication process starts with 200 micrometer thick 3 inch wafers onto which a 50 angstrom chrome, 300 angstrom gold electroplating strike is e-beam evaporated. A 25 micrometer thick optical resist is deposited on the wafers using a low spin rate. The resist is exposed and developed and an oxygen plasma clean is performed to fully strip resist residue from the strike. 25 micrometers of gold is then plated in the resist mold, resulting in a gold grid with photoresist between each gold slat. The wafer is turned over and a 50 micrometer dry resist is patterned such that it has a array of 1 by 4 millimeter openings to the silicon. The silicon is etched through to the chrome/gold strike using a xenon difluoride etching process. Both types of photoresist are removed with acetone followed by a piranha clean and the chrome/gold strike is removed with a hydrochloric acid and hydrogen peroxide chrome etch which also slowly etches gold.

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Reid A. Brennen, Michael H. Hecht, Dean V. Wiberg, Steven Manion, William D. Bonivert, Jill M. Hruby, Kristofer S. J. Pister, and Ezekiel J. Kruglick "Fine pitch grids for an x-ray solar imaging spectrometer fabricated by optical lithography and XeF₂ etching", Proc. SPIE 2640, Microlithography and Metrology in Micromachining, (26 September 1995); https://doi.org/10.1117/12.222651

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