Optical and structural properties of silicon oxynitride deposited by plasma enhanced chemical vapor deposition

• Published in: Thin solid films 2010-12, Vol.519 (4), p.1325-1333
• Main Authors: Dupuis, J., Fourmond, E., Ballutaud, D., Bererd, N., Lemiti, M.
• Format: Article
• Language: English
• Subjects: Annealing; Applied sciences; Chemical Sciences; Chemical vapor deposition; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Deposition; Energy; ERDA; Exact sciences and technology; FTIR; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Natural energy; Optical instruments, equipment and techniques; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Photovoltaic cells; Photovoltaic conversion; Physics; Plasma enhanced chemical vapor deposition; Polarimeters and ellipsometers; Precursors; Radiochemistry; Silicon oxynitride; SiON; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Surface passivation; XPS
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2010.09.036

We present an overview of the properties of silicon oxynitride material (SiON) deposited by plasma enhanced chemical vapor deposition (PECVD) for photovoltaic applications. SiON films were deposited using silane (SiH 4), ammonia (NH 3) and nitrogen protoxide (N 2O) as precursor gases in a low frequency PECVD. Varying the gas flow mixture leads to a whole range of SiON layers starting from the silicon oxide to the silicon nitride with unique stoichiometries and properties. Thanks to spectroscopic ellipsometry measurements we have confirmed the suitability of SiON for antireflection coating layers due to the range of the refractive indexes attainable. SiON structure was analyzed by X-ray photo-electron spectroscopy. We have thus highlighted the critical role of oxygen behavior on the SiON network and the progressive replacement of nitrogen by oxygen atoms when the oxygen precursor increases. The type of chemical bonds present in SiON layers was also investigated by infrared spectroscopy. The SiON layers also contain a non-negligible amount of hydrogen which might be useful for passivation applications. The behavior of hydrogen content was thus analyzed by elastic recoil decay analysis and desorption characterization. A typical rapid thermal annealing was performed on the SiON samples in order to simulate the solar cells contact annealing and to investigate its impact on the dielectric film properties. It was found that hydrogen becomes weakly bonded to the films and strongly decreases in quantity with the annealing. The surface passivation effect is presented in the last part of this paper. The trend before and after a rapid thermal annealing showed opposite results which could be explained by the high porosity of the layers and the formation of Si–O bonds.