Uniform BCB bonding process toward low propagation loss in GaInAsP photonic wire waveguide on Si wafer

To realize optical integrated circuits on LSI with membrane structure of III-V material, we have investigated GaInAsP wire waveguide instead of global electrical wire which will be the bottleneck of LSI performance limitation. This time, fabrication process and characteristics of GaInAsP wire waveguides on Si substrate by adhesive bonding using benzocyclobutene (BCB) were investigated. A good bonding interface between SiO₂ and BCB with no air-void was achieved by extending pre-cure time of BCB. By using improved BCB bonding conditions, propagation loss of 460 × 150 nm² GaInAsP wire waveguide on Si substrate at λ=1.55 μm was reduced to 17 dB/cm which is a record low propagation loss in III-V material wire waveguides propagating at mm-order.