This paper reports a new and more efficient Si waveguide sidewall smoothing process using wet chemical oxidation. Sidewall roughness is a major source of loss and an impediment to realizing high-transmission Si waveguides. The postetch multistepped approach allows for efficient smoothing (in terms of roughness amplitude reduction to material consumption) by continuous oxidation in the fast reaction-limited regime. This method reduces waveguide transmission loss without sacrificing dimensional integrity or thermal budget. In this proof-of-concept work, Si waveguide sidewall loss has been reduced from 9.2 to 1.9 dB/cm.
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