Adhesion of Si and LiNbO₃ via Perhydropolysilazane for Photonic Substrate Fabrication

In this study, we propose a new bonding technique for fabricating LiNbO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> on insulator (LNOI) wafers using perhydropolysilazane (PHPS) as an adhesive layer. PHPS transforms into optically transparent silica (SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>) with water at room temperature. The bonding process is enhanced by N2 plasma irradiation, which makes the wafer surfaces hydrophilic, facilitates the silica conversion of PHPS, and improves the bonding strength. This method is attractive because it relaxes the requirements for surface roughness and can be performed at room temperature.