Back side release of slot waveguides for integration of functional materials in a silicon photonic technology with full BEOL

In this work, we developed a process to release the optical waveguides locally from the back side of a silicon-on-insulator wafer to enable a connection and an interaction between organic materials and photonic devices. The release procedure is realized by a local back-side etch followed by a chemical wet etch. Furthermore, certain process steps for a controlled removal of the buried oxide below the silicon device layer are introduced to protect the back end of line (BEOL) and to guarantee a compatibility with a photonic integrated circuit (PIC) technology. The presented approach gives perspective to a hybrid integration of organic materials into a PIC technology with a full BEOL for high-speed silicon-organic hybrid modulators and label-free biosensors.