3 January 2014 Optimization of electron beam patterned hydrogen silsesquioxane mask edge roughness for low-loss silicon waveguides
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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.
© 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)
Michael G. Wood, Li Chen, Justin R. Burr, Ronald M. Reano, "Optimization of electron beam patterned hydrogen silsesquioxane mask edge roughness for low-loss silicon waveguides," Journal of Nanophotonics 8(1), 083098 (3 January 2014). https://doi.org/10.1117/1.JNP.8.083098 . Submission:
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