Energy distribution of negative ions of atomic oxygen during the sputter deposition of TiO_2 and SiO_2 thin films

摘要

By energy-resolved mass spectrometry, the nature and energy distribution of negative ions O~- impinging on the surface of a growing thin film has been investigated as a function of the total gas pressure and different pressure ratios of Ar and O_2. A different behaviour of the atomic negative ions O~- has been determined depending on the target (Ti or Si) used to deposit TiO_2 and SiO_2 by reactive sputtering. Low-energy tailed peaks have been detected for both Ti and Si targets. With the Si target a high-energy peak also appeared. An oxygen dissociative attachment mechanism can explain the main phenomena, being also demonstrated that the duty cycle plays a significant role in the variation of the plasma parameters (n_e, T_e).