Physical properties of plasma deposited SiOx thin films

Abstract The composition ( x =[O]/[Si]), hydrogen content, bonding configuration and paramagnetic defects of SiO x films were studied. Films were deposited by the electron cyclotron resonance plasma method at room temperature using SiH 4 and O 2 as precursor gases, and depending on gases flux ratio, films from x ≈2 to 0.9 were obtained. Infrared spectroscopy analysis showed the presence of different vibration modes: Si–O stretching, used to estimate film composition, bending and rocking with positions nearly independent on film composition, and various Si–H peaks: stretching and wagging-bending. Films with non-stoichiometric composition show a wider peak than the ones deposited at higher gas ratios. Ellipsometry measurements showed a refractive index at λ =632.8 nm comprised between 1.45 and 2.04. Electron spin resonance measurements shows that the stoichiometric films ( x ≈2) present the well known E ′ centre ( Si≡O 3 ) with concentrations in the 10 16  cm −3 range, while for Si-rich films ( x ⪡2) the Si dangling bond centre ( D centre, Si≡Si 3 ) is dominant, with concentrations in the 10 18 –10 19  cm −3 range. For near-stoichiometric ( x ≈1.9) films also both E ′ and D centres are present, but in this case the E ′ centre is dominant.