Optical loss in silicon microphotonic waveguides induced by metallic contamination

Propagation losses are paramount to the performance of microphotonic devices. In silicon photonics, the expected contribution of known propagation-loss mechanisms is often insufficient to account for all the observed loss. Here, we identify a loss mechanism that we believe has not yet been reported in the literature. We observe loss reaching 70 dBcm in silicon wire waveguides patterned in proximity of metals with low temperatures of silicide formation. The loss is attributed to formation of a dilute silicide at the waveguide sidewalls during reactive-ion etching. Sputtered metal atoms originate from exposed metal on the wafer surface or from the reactive-ion etcher chamber and react with the bare silicon of the waveguide sidewall being formed. © 2008 American Institute of Physics.