Deposition of durable wideband silver mirror coatings using long-throw low-pressure DC-pulsed magnetron sputtering

Jesse D. Wolfe; David M. Sanders; Steve Bryan; Norman L. Thomas

doi:10.1117/12.458075

30 January 2003 Deposition of durable wide-band silver mirror coatings using long-throw, low-pressure, DC-pulsed magnetron sputtering

Jesse D. Wolfe, David M. Sanders, Steve Bryan, Norman L. Thomas

Author Affiliations +

Proceedings Volume 4842, Specialized Optical Developments in Astronomy; (2003) https://doi.org/10.1117/12.458075
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

Sputter deposition at long-throw distances (15-30 in.) and low pressures (<1 mTorr) were developed mainly for the semiconductor industry to deposit metals and dielectrics into trenches or vias on silicon and gallium arsenide wafers. Scientists found that sputter depositions performed at pressures below 1 mTorr (0.13 Pa) results in a virtually collision-free trajectory of the sputtered atoms from the target to the substrate. If the throw distance (source to substrate) is increased at these low pressures, the activated (ionized) gas and target atoms maintain their energy. We used this methodology along with dc-pulsed sputtering to deliver additional energy at the substrate. This allowed us to coat large optics (>21-in. diameter) in a standard box coater using smaller-diameter sputter cathodes. This paper will discuss the process used to successfully coat a 22-in.-diameter optic for the Keck Telescope in Hawaii with a new Wide-Band Durable Silver Mirror. The process uses smaller-diameter sputter cathodes in a 4-ft.-x-4-ft.-x-5-ft. box coater. We will also discuss how the process can be scaled to 36-in. or larger optics for use on terrestrial or space-based platforms.

Citation Download Citation

Jesse D. Wolfe, David M. Sanders, Steve Bryan, and Norman L. Thomas "Deposition of durable wide-band silver mirror coatings using long-throw, low-pressure, DC-pulsed magnetron sputtering", Proc. SPIE 4842, Specialized Optical Developments in Astronomy, (30 January 2003); https://doi.org/10.1117/12.458075

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