We report the development of new fabrication techniques for creating high aspect ratio optical lightpipes in SiO2 layers of 10μm thickness and above. A dielectric photo mask was used for deep reactive ion etching. Our experiments show that CF4-based reaction gases were best for deep etching with high selectivity and etch rate. Trenches with diameters or width of 1.5μm were demonstrated, with an aspect ratio of 7.2:1 and a sidewall angle of 87.4 degrees. We also present the lift-off process of the etch masks and the via-filling procedures for the lightpipes. These structures are useful for image sensors, vertical interconnect and waveguiding applications.

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Keywords Deep-etching fabrication, Dielectric photo mask, High-aspect-ratio etching, Image sensors, Lightpipes, Vertical interconnects, Vertical waveguides
Persistent URL dx.doi.org/10.1117/12.840725
Conference Advanced Fabrication Technologies for Micro/Nano Optics and Photonics III
Ye, W.N, Duane, P. (Peter), Wober, M. (Munib), & Crozier, K.B. (Kenneth B.). (2010). Fabrication techniques of high aspect ratio vertical lightpipes using a dielectric photomask. In Proceedings of SPIE - The International Society for Optical Engineering. doi:10.1117/12.840725