Modeling and fabrication of traveling-wave electrode (TWE) of Si optical modulator via Cu-BEOL

CMOS-compatible silicon photonics technology is becoming a promising candidate to realize very large-scale complex photonics-CMOS integration system. For the purpose of CMOS-compatible complete-Cu integration, a traveling-wave electrode (TWE) of a silicon optical modulator via Cu-based back-end-of-line (BEOL) process is demonstrated in this work. A latticed Cu surface pattern is designed for the requirement of Cu-BEOL process. The Cu-TWE is modeled on aspects of the group velocity match and the characteristic impedance match. The dual-damascene based Cu-BEOL fabrication process for the TWE and the contact plugs of the modulator is presented. Finally, the experiment and characterization results are presented, and above 30 GHz-bandwidth can be achieved.