Ab initio calculations on the depassivation reaction of H⁺ at a-SiO₂/Si(100) interfaces

Hydrogen is widely used to passivate the dangling bonds generated in the thermo xidation process, which significantly improves the electronic quality of the Si/SiO₂ interface. It may, however, make the devices vulnerable in certain environments. For example, ionization radiation may convert the excess hydrogen induced in the fabrication process to protons, and then the later may migrate to the interface and depassivate the dangling bonds saturated by hydrogen. In this study, the depassivation of P_b1 and P_b0 defects generated in amorphous SiO₂/Si(100) interfaces is investigated quantitatively. For P_b1 defects, the proton detaches from the oxygen atom and then activates the defect. The forward reaction barrier is ~0.4 eV. After the reaction, the energy of the system decreases by 0.85 eV. The depassivation of P_b0 defects is more unpredictable, because the proton may be trapped by other atoms or bonds during the long reaction path due to the location of the defect. In our simulation, the proton can be captured by Si-O-Si or Si-Si bond, and form threefold-coordinated O atom defect or Si-H⁺-Si bridge bond, respectively. The energy of the intermediate products is lower than the desired ones.