Room-temperature direct bonding of yttria-stabilized zirconia to silicon wafer via surface activation for advanced heterointegration

Achieving high-quality heterogeneous integration between single-crystal oxide materials and silicon-based platforms is a critical prerequisite for advancing the application of oxide devices. Yttria-stabilized zirconia (YSZ) is regarded as an ideal buffer layer material for complex oxides epitaxially grown on silicon substrates due to its excellent lattice matching and chemical inertness. However, a significant difference in thermal expansion coefficients between YSZ and silicon (Si) makes it difficult to achieve ideal quality standards for YSZ buffer layers prepared using conventional high-temperature processes. This study employed surface activation bonding technology to realize high-quality hetero-integration of YSZ/Si. The results obtained indicate an ideal YSZ/Si bonding area, with only trace localized voids observed at the edges. A 9.5 nm-thick transition layer formed at the interface, exhibiting atomic-level flatness and crack-free integrity. The interface formation mechanism is attributable to the dual effects of Ar atom bombardment and Fe atom sputtering-deposition, resulting in a bilayer structure composed of an amorphous Si layer and an α-Fe crystalline layer. YSZ maintained excellent single-crystal quality in the near-interface region. The investigation established a high-quality YSZ/Si platform, which was found to provide an outstanding substrate for the growth of various functional oxide materials and subsequent device fabrication.