Rapid thermal annealing effects on plasma deposited SiO x:H films

Abstract

The bonding configuration, hydrogen evolution and defect content of rapid thermally annealed (RTA) SiO x :H films of different initial compositions were studied. Infrared absorption measurements showed that all the hydrogen present in the films was lost at temperatures lower than 700°C without any change in the oxygen to silicon ratio of films. RTA temperatures higher than 700°C promote a change in the Si–O–Si stretching position from the initial unannealed value to the 1070–1080 cm −1 range independent of the initial film composition. Electron Spin Resonance (ESR) measurements show that all the films contained two types of paramagnetic defects: E′ ( Si≡O 3) and D ( Si≡Si 3). Annealing up to 700°C promotes the disappearance of the E′ centre. For films where the D defect is present (all except the film with x≈2), the concentration of these defects initially decreases for annealing temperatures of 400°C, then continuously increases for temperatures up to 700°C, getting a saturation value in the 10 18–10 19 cm −3 range for higher temperatures. ESR characterisation suggests that annealing at higher temperatures promotes the formation of a high-quality SiO 2 matrix in which Si nanocrystals are formed, the D defects being located within these nanocrystals.