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 dB/cm 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. (C) 2008 American Institute of Physics.