Stoichiometric limitations of RF plasma deposited amorphous silicon–nitrogen alloys

• Published in: Thin solid films 1997-12, Vol.311 (1), p.133-137
• Main Authors: Almeida, S.A, Silva, S.R.P
• Format: Article
• Language: English
• Subjects: Amorphous materials; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Rutherford backscattering spectroscopy; Silicon nitride; Stress
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/S0040-6090(97)00460-4

The variation of the composition and structural properties of plasma enhanced chemical vapour deposited hydrogenated amorphous silicon–nitrogen alloys (a-SiN x :H y ) are studied as a function of the feed gas flow ratio. A capacitively coupled parallel plate chemical vapour deposition reactor (with R=NH 3/SiH 4, ratios of 0.2 to 200) was used to deposit the a-SiN x :H y thin films. Rutherford backscattering spectrometry and elastic recoil detection were used to analyse the composition of the films. The Si content in the films decreased in a logarithmic manner for 0< R4. A turning point for the experimentally measured properties was observed at R≈4 for the specified deposition conditions. This corresponds to a N/Si ratio of about 1.45±0.15 with a hydrogen content of 22 at.% for the deposited a-SiN x :H y films. Below this pivotal ratio, the films have high growth rates, a refractive index between 1.9 and 2.7, a N/Si ratio between 0.5 and 1.5 and moderate values of compressive stress (∼0.7 GPa). While, above this pivotal ratio of R≈4, growth rates become significantly lower, the refractive index minimises to 1.8, N and Si concentrations in the films saturate and the compressive stress rapidly increases.