Process control and monitoring in device fabrication for optical interconnection using silicon photonics technology

Precise dimension control technology for the fabrication of silicon photonics devices was established. The dimension control technology is based on the devices fabrication using 40-nm-node CMOS technology and in-line process monitoring by optical wafer-level probing system. As the results of process optimization in waveguide formation, superior dimension control in 440-nm-wide / 220-nm-thick waveguides was achieved, in which waveguide width deviation of 1.0 nm and height deviation of0.3 nm were respectively obtained for a single 300-mmφ wafer. In the characterization of 5th-order coupled resonator optical waveguides (CROWs), remarkably small deviation of resonant frequency 0.7 nm in a single wafer was confirmed, which values agreed with the theoretical estimation from the fabrication error. As for the optical wafer-level probing system, quite small deviation less than 0.2 dB in I/O coupling loss between optical devices under test and fiber probe was confirmed. It was successfully shown that the combination of the precise process control and the in-line optical process control monitor is sufficient to the reproducible device fabrication for wide-bandwidth optical interconnection.