Multi-layer stacking scheme of sol-gel based SiO₂ towards thicker (>0.8 µm) cladding layers for optical waveguides

A multi-layer stacking scheme using a sol-gel SiO₂ fabrication technique was developed towards stacking thick layers of >0.8 µm for cladding and passivation layers of optical waveguides. The multi-layer stacking scheme, which improves the intrinsic stress problem especially in case of thick layer stacking, enables a >0.8 µm sol-gel SiO₂ thickness without cracking and peeling issues. As a result, thick layer of 3.5 µm with high surface resistivity of >6.6 × 10¹³ Ω/m was obtained. Furthermore, a-Si/SiO₂ waveguide (cladding thickness: 1.9 µm) was realized to confirm the fundamental potential as a cladding layer.