Ni-Al-Ti ALLOY BASED THIN FILMS AS PASSIVATION LAYER FOR COPPER INTERCONNECTS

Date

2025-7

Author

Livan Şimşek, Pelin

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A systematic investigation was conducted on the Ni–Al–Ti ternary alloy system to evaluate its potential as a passivation layer for Cu-based thin film interconnects. For this purpose, 500 nm Ni–Al–Ti films were fabricated across a wide compositional range using a combinatorial magnetron co-sputtering approach and deposited on Cu/Ti/SiO2/Si substrates. The resulting film library was characterized by grazing incidence X-ray diffraction (GI-XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), and the structural phases were mapped in the ternary diagram. The multilayered Ni–Al–Ti/Cu/Ti/SiO2/Si films were then oxidized at 300 °C in dry air, and selected samples were examined via X- ray photoelectron spectroscopy (XPS) depth profiling. The oxidation behavior varied with composition. Films near the Ni and Al corners delaminated and fragmented, while Ti-rich compositions remained intact but showed interdiffusion of Ni, Al, Ti, Cu, and oxygen, leading to the loss of distinct layers. In contrast, films located away from the edges maintained structural integrity: oxygen was confined to the passivation layer, and copper remained metallic, although partial Cu diffusion into the top layer was observed. Compositions near the ternary center (Ni: 39–59 at. %, Al: 19–44 at. %, Ti: 9–27 at. %) exhibited optimal performance. Oxygen was primarily bonded to Ni at the surface and to Ti and Al below, with Al continuing to bind oxygen near the Cu interface, while Ni and Ti remained metallic. Copper showed no oxidation. These results demonstrate that Ni–Al–Ti films with balanced elemental fractions can serve as effective passivation layers for protecting copper interconnects.

Subject Keywords

Copper Interconnects, Passivation of Copper Interconnects, Ni-Al-Ti Ternary Thin Films, Combinatorial Approach, XPS Depth Profiling

URI

https://hdl.handle.net/11511/116011

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Graduate School of Natural and Applied Sciences, Thesis