| A novel photonic nano-coupler based on a nano-trench has been proposed, where the trench width depends on the refractivity of inside the trench; a highly refractive material needs to backfill the trench for a width that permits reliable trench fabrication. While ALD was considered the ideal method for backfilling, the materials that are compatible both with ALD and the rest of the process were reduced to Al2O3 and HfO2, with a large refractive index gap in between. In this study, we have created two types of structures with alternating layers of Al2O3 and HfO2 for customizing refractive index. Multiple sets with different composition ratios were built and tested by ellipsometry to reveal the correlation between the ratio and the effective refractive index. The second topic of the study is complete filling of high aspect ratio trenches by ALD; SEM/EDX and TEM analyses were used to establish seam formation mechanics. |
