Chemical and morphological properties of amorphous silicon oxynitride films deposited by plasma enhanced chemical vapor deposition

The deposition of amorphous hydrogenated silicon oxynitride thin films, var ying the nitrogen and oxygen content in ge the solid phase, is reported. Th e films were deposited by plasma enhanced chemical vapor deposition at diff erent nitrous oxide/silane flow ratios, keeping constant the silane flow an d the deposition temperature at 320 degreesC. The composition of the thin f ilms was determined by Rutherford backscattering spectroscopy (RBS) and the morphological properties were investigated by small angle X-ray scattering (SAXS) and transmission electron rnicroscopy (TEM). The composition data s howed that the oxygen content increases and the nitrogen content decreases, inside the films, as the ratio between the nitrous oxide flow and silane f low goes toward larger values. The oxygen (x) plus nitrogen (y) content in the chemical formula (a-SiOxNy) is always close to two, suggesting that the se atoms share the same atomic positions around the silicon atoms in a loca l structure similar to SiO2. The SAXS results revealed the presence of scat terers with an average radius (R) that varies from small values, like 10 An gstrom, up to 100 Angstrom. The TEM results showed the formation of particl es with a circular cross-section, composed of Si, N and O spread in a matri x with the same elemental composition. These particles have a radius larger than 50 Angstrom. (C) 2001 Elsevier Science B.V. All rights reserved.