Physical properties of plasma deposited SiOx thin films

Abstract

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 O-2 as precursor gases, and depending on gases flux ratio, films from x approximate to 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 lambda = 632.8 nm comprised between 1.45 and 2.04. Electron spin resonance measurements shows that the stoichiometric films (x approximate to 2) present the well known E' centre (.SidropO(3)) with concentrations in the 10(16)cm(-3) range, while for Si-rich films (x much less than 2) the Si dangling bond centre (D centre, .SidropSi(3)) is dominant, with concentrations in the 10(18)-10(19) cm(-3) range. For near-stoichiometric (x approximate to 1.9) films also both E' and D centres are present, but in this case the E' centre is dominant.