Scalable Fabrication of Diamond-on-Silica Heterostructures via High-Selectivity Deep ICP-RIE and Room-Temperature Bonding
Single-crystal diamond is a leading material platform for high-power electronics and solid-state quantum technologies, yet many device architectures require micrometer-scale membranes with deeply etched features, patterned from commercially available substrates. In this work, we demonstrate a complete through-etch of a 16 {\mu}m -thick NV-doped single-crystal diamond membrane using a single-layer SiO2 hard mask combined with a multi-step oxygen-based ICPRIE process. With a diamond-to-SiO2 selectivity of 15:1, this non-metallic mask strategy can achieve etch depths of few tens of {\mu}m with well-defined sidewalls, conserved surface roughness and negligible micromasking. Furthermore, we use the oxide layer that remains after etching to serve as the bonding surface in a subsequent integration step. The etched microstructures are transferred onto SiO2 substrates and bonded at room temperature using O2 plasma surface activation and a sodium silicate interlayer. The resulting siloxane film is optically transparent across the visible spectrum and introduces no detectable parasitic photoluminescence, preserving the optical readout of the embedded NV centers. Together, this deep-etch and room-temperature bonding process provides a scalable and contaminationfree route from bulk diamond membranes to diamond-on-silica heterostructures for integrated quantum photonics and sensing applications.