Hydrogen release at metal-oxide interfaces: A first principle study of hydrogenated Al/SiO2 interfaces

The Anode Hydrogen Release (AHR) mechanism at interfaces is responsible for the generation of defects, that traps charge carriers and can induce dielectric breakdown in Metal-Oxide-Semiconductor Field Effect Transistors. The AHR has been extensively studied at Si/SiO2 interfaces but its characteristics at metal-silica interfaces remain unclear. In this study, we performed Density Functional Theory (DFT) calculations to study the hydrogen release mechanism at the typical Al/SiO2 metal-oxide interface. We found that interstitial hydrogen atoms can break interfacial AlSi bonds, passivating a Si sp3 orbital. Interstitial hydrogen atoms can also break interfacial AlO bonds, or be adsorbed at the interface on aluminum, forming stable AlHAl bridges. We showed that hydrogenated OH, SiH and AlH bonds at the Al/SiO2 interfaces are polarized. The resulting bond dipole weakens the OH and SiH bonds, but strengthens the AlH bond under the application of a positive bias at the metal gate. Our calculations indicate that AlH bonds and OH bonds are more important than SiH bonds for the hydrogen release process.