Characterization of Ozone-Ethylene Radical Pretreatment for Hybrid Bonding without Water Rinsing Processes

An Ozone-Ethylene Radical (OER) generation technology can produce a highly active oxidizing agent of OH radicals by mixing an unsaturated hydrocarbon gas with a highly concentrated ozone gas. The OH radicals given by the OER treatment are expected to be used as a prospective surface hydrophilization technique without water rinsing. In this study, we investigate the effectiveness of the surface treatment technology OER on hybrid bonding with thermally grown SiO2, CVD-SiCN, and PVD-Cu thin films by water contact angle (WCA), AFM, and XPS. N2 plasma activation is also used before the OER treatment for comparison. OER drastically reduces the WCA of the SiCN thin films compared to the SiO2 thin film. The AFM analyses found that the surface roughness of the dielectric films is kept after the OER treatment, whereas OER slightly increases the surface roughness of Cu. XPS results suggest that the OER treatment acts on the SiO2 nitrided by N2 plasma to form Si-OH, and in addition, Cu(oh)2becomes dominant after OER processing. On the other hand, hydrophilic Cu2O mainly occupies the Cu surface before the OER treatment. Furthermore, the OER treatment on SiCN enhances oxygen composition, suggesting that OER yields more Si-OH groups by OH radicals. These results indicate that OER is a useful pretreatment method for hybrid bonding.