Role of point defects in dielectric breakdown of sio₂formed by plasma-enhanced chemical vapor deposition of tetraethoxysilane

The intrinsic breakdown strength of thin SiO₂films formed by plasma-enhanced chemical vapor deposition of tetraethoxysilane was measured using a self-healing technique by applying short-duration voltage pulses. Point defects in the films and other film qualities were examined by instrumental analyses and by optical absorption and luminescence using synchrotron radiation. The intrinsic breakdown strength decreases when the deposition temperature becomes higher than 400 °C, in spite of the fact that the optical gap and the density increase and the impurity content decreases. Based on the fact that the film deposited at high temperatures shows absorption at 7.6-eV and luminescence at 4.4-eV, the existence of oxygen vacancies(Si-Si) is suggested. The intrinsic breakdown strength is increased by decreasing oxygen vacancies through oxygen treatment. From these results, it is considered that oxygen vacancies play a crucial role in lowering the breakdown strength. Three possible mechanisms are discussed.