Influence of temperature and hydrogen rate on silicon incorporation in silica films by reactive magnetron co-sputtering

Silicon-rich silicon oxide layers were deposited by reactive magnetron sputtering of a pure silica target. The main purpose was to understand how the different deposition parameters affect the silicon incorporation, in order to control the fabrication of efficient light emitting Si/SiO2 multilayers. The silicon excess incorporated in the films was monitored by two main parameters: (i) the hydrogen partial pressure (PH) introduced in the plasma, owing to the ability of hydrogen to reduce the oxygen released by the sputtered silica target, and (ii) the substrate temperature (TS). The silicon excess estimated from the refractive index contrast with respect to silica, as determined by spectroscopic ellipsometry and optical transmission, was found to increase from 2.1 to 3.1 when TS and PH are increased. The evolution of the infrared absorption spectroscopy spectra reflects the incorporation of silicon excess, while microstructural studies allowed the determination of the nature (crystalline or amorphous) of Si aggregates. Studies using atomic force microscopy on tapping mode revealed that the surface roughness deteriorate for high PH, leading to the adoption of low values of hydrogen partial pressure for the fabrication of efficiently luminescent multilayers.