Physical properties of plasma deposited SiO<inf>x</inf> thin films

The composition (x = [O]/[Si]), hydrogen content, bonding configuration and paramagnetic defects of SiOx films were studied. Films were deposited by the electron cyclotron resonance plasma method at room temperature using SiH4 and O2 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 ¿ = 632.8nm 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¿O3) with concentrations in the 1016cm-3 range, while for Si-rich films (x ¿ 2) the Si dangling bond centre (D centre, ·Si¿Si3) is dominant, with concentrations in the 1018-1019cm-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. © 2002 Elsevier Science Ltd. All rights reserved.