Improved optical loss characteristics of PECVD silicon oxynitride films using low frequency plasma


With the continued growth of photonics, silicon oxynitride (SiOxNy) is becoming a popular material for optoelectronic applications owing to its large tunable refractive index. However, with the increase in refractive index, these films tend to show poor optical transmission characteristics. In this research we have investigated the influence of growth conditions on the loss characteristics of PECVD SiOxNy films. The films are grown at 350 °C substrate temperature and 1 Torr pressure with silane (SiH4) and nitrous oxide (N2O) precursor gases. The precursor flow rate and power input to the system are varied as the two primary parameters. It is observed that films grown at 100 kHz plasma frequency proved to be more transmissive than films grown at 13.56 MHz plasma frequency. Elastic recoil detection analysis results showed the hydrogen content is less in the low frequency films than the high frequency films, which is believed to be the reason for the low loss behavior. The details of these analysis results are discussed below.

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The authors would like to thank Prof. John F. Muth and Ailing Cai at the Department of Electrical and Computer Engineering, North Carolina State University for helping in carrying out the material loss measurement of the silicon oxynitride samples. This research is sponsored by Laboratory of Photonic Nanocomposites, sponsored by DARPA/MTO under contract number # N66001-03-1-8900. The tuition and educational support for Sudipto Naskar is provided by Gould Research Fellowship at Case Western Reserve University, OH where he is a doctoral candidate. The research is conducted at the METD division of RTI-International, Research Triangle Park, NC and formerly MCNC-RDI, Research Triangle Park, NC.

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Naskar, S., Bower, C., Wolter, S. et al. Improved optical loss characteristics of PECVD silicon oxynitride films using low frequency plasma. MRS Online Proceedings Library 862, 203 (2004).

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