LAUSR

As an emerging platform for high-precision sensing, integrated silicon-waveguide-based cavity optomechanical devices face a critical fabrication challenge in the co-fabrication of silicon-on-insulator (SOI) micromechanical structures and optical waveguides: the silicon oxide (SiO2) layer beneath the waveguides is susceptible to etching during hydrofluoric acid (HF) release of the microstructures, leading to waveguide collapse and significantly reducing production yields. This study proposes a novel selective protection process based on a magnesium fluoride (MgF2) thin film to address the critical challenge of long-range waveguide collapse during hydrofluoric acid (HF) etching. By depositing a MgF2 protective layer over the waveguide regions via optical coating technology, localized protection of specific SiO2 areas during HF etching is achieved. The experimental results demonstrate the successful release of silicon waveguides with lengths of up to 5000 μm and a significant improvement in production yield. This work provides a compatible and efficient strategy for the fabrication of robust photonic–microelectromechanical integrated devices.