Passivation and dissociation of P_b-type defects at a-SiO₂/Si interface

It is well known that in the process of thermal oxidation of silicon, there are P_b-type defects at amorphous silicon dioxide/silicon (a-SiO₂/Si) interface due to strain. These defects have a very important impact on the performance and reliability of semiconductor devices. In the process of passivation, hydrogen is usually used to inactivate P_b-type defects by the reaction P_b+H₂→P_bH+H. At the same time, P_bH centers dissociate according to the chemical reaction P_bH→P_b+H. Therefore, it is of great significance to study the balance of the passivation and dissociation. In this work, the reaction mechanisms of passivation and dissociation of the P_b-type defects are investigated by first-principles calculations. The reaction rates of the passivation and dissociation are calculated by the climbing image-nudged elastic band (CI-NEB) method and harmonic transition state theory (HTST). By coupling the rate equations of the passivation and dissociation reactions, the equilibrium density ratio of the saturated interfacial dangling bonds and interfacial defects (P_b, P_b0, and P_b1) at different temperatures is calculated.