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Exploring the Limits of Bottom-Up Gold Filling to Fabricate Diffraction Gratings



Daniel Josell, Stephen J. Ambrozik, Maureen E. Williams, A E. Hollowell, Christian Arrington, Shinichiro Muramoto, Thomas P. Moffat


Gold deposition on rotating disk electrodes, Bi3+ adsorption on planar Au films and superconformal Au filling of trenches up to 45 m deep are examined in Bi+3-containing Na3Au(SO3)2 electrolytes with pH between 9.5 and 11.5. Higher pH is found to increase the potential-dependent rate of Bi adsorption on planar Au surfaces, shortening the incubation period that precedes active Au deposition on planar surfaces and bottom-up filling in patterned features. Decreased contact angles between the Au seeded sidewalls and bottom-up growth front also suggest improved wetting. The bottom-up filling dynamic in trenches is, however, lost at pH 11.5. The impact of Au concentration, 80 mmol/L versus 160 mmol/L Na3Au(SO3)2, on bottom-up filling is examined in trenches up ≈ 210 m deep with aspect ratio of depth/width ≈ 30. The microstructure of void-free, bottom-up filled structures characterized by scanning electron microscopy (SEM) and Electron BackScatter Diffraction (EBSD), revealing marked spatial variation of the grain size and orientation within the filled features.
Journal of the Electrochemical Society


gold, grating, trenches, superfill
Created November 27, 2019, Updated February 26, 2020