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Journal of Nanophotonics

Optimization of electron beam patterned hydrogen silsesquioxane mask edge roughness for low-loss silicon waveguides
Author(s): Michael G. Wood; Li Chen; Justin R. Burr; Ronald M. Reano
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Paper Abstract

We carried out a multiparameter fabrication study designed to reduce the line edge roughness (LER) of electron beam (e-beam) patterned hydrogen silsesquioxane resist for the purpose of producing low-loss silicon strip waveguides. Reduced mask roughness was achieved for 50°C pre-exposure baking, 5000  μC/cm 2 dose with a beam spot size more than twice as large as the electron beam step size, development in 25% tetramethylammonium hydroxide and postdevelopment baking with rapid thermal annealing in an O 2 ambient at 1000°C. The LER caused by pattern fracturing and stage stitches was reduced with multipass writing and per-pass linear and rotational offsets. Si strip waveguides patterned with the optimized mask have root-mean-square sidewall roughness of 2.1 nm with a correlation length of 94 nm, as measured by three-dimensional atomic force microscopy. Measured optical propagation losses of these waveguides across the telecommunications C-band were 2.5 and 2.8  dB/cm for the transverse magnetic and transverse electric modes, respectively. These reduced loss waveguides enable the fabrication of advanced planar lightwave circuit topologies.

Paper Details

Date Published: 3 January 2014
PDF: 15 pages
J. Nanophoton. 8(1) 083098 doi: 10.1117/1.JNP.8.083098
Published in: Journal of Nanophotonics Volume 8, Issue 1
Show Author Affiliations
Michael G. Wood, The Ohio State Univ. (United States)
Li Chen, The Ohio State Univ. (United States)
Justin R. Burr, The Ohio State Univ. (United States)
Ronald M. Reano, The Ohio State Univ. (United States)

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