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 Alsingle bondSi bonds, passivating a Si sp3 orbital. Interstitial hydrogen atoms can also break interfacial Alsingle bondO bonds, or be adsorbed at the interface on aluminum, forming stable Alsingle bondHsingle bondAl bridges. We showed that hydrogenated Osingle bondH, Sisingle bondH and Alsingle bondH bonds at the Al/SiO2 interfaces are polarized. The resulting bond dipole weakens the Osingle bondH and Sisingle bondH bonds, but strengthens the Alsingle bondH bond under the application of a positive bias at the metal gate. Our calculations indicate that Alsingle bondH bonds and Osingle bondH bonds are more important than Sisingle bondH bonds for the hydrogen release process