We describe a means for improving the performance of CMOS image sensors using vertical waveguides, known
as light pipes. We describe experimental results on the etching of silicon nitride pillars, and the fabrication of
We report the development of new fabrication techniques for creating high aspect ratio optical lightpipes in SiO<sub>2</sub> layers
of 10μm thickness and above. A dielectric photo mask was used for deep reactive ion etching. Our experiments show
that CF<sub>4</sub>-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.