Comparative effects of plasma treatments on SiO2 surface and bonding performance for wafer and hybrid bonding

초록

We investigate the effects of plasma on SiO2 surfaces in various plasma environments, including Ar, O2, and N2, under identical plasma conditions for low-temperature annealing in SiO2/SiO2 wafer bonding. After plasma treatments, no damage is observed on the SiO2 surface, which is comparable to post-CMP SiO2. With the Ar and O2 plasma treatments and XPS analysis, the SiO2 surface shows a Si-OH-rich surface and changes to more hydrophilic properties. Although N2 plasma treatment results in a few isolated voids being observed compared to O2 plasma treatment, N2 plasma treatment will be a suitable choice for Cu/SiO2 hybrid bonding thanks to its highest bonding strength compared to other plasma treatments and the ability to avoid Cu oxidation. On the other hand, O2 plasma treatment on SiO2 surface is the most effective way for SiO2/SiO2 wafer bonding providing excellent hydrophilicity, strong bonding strength, and minimal bonding voids.

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