Silicon Oxynitride can be deposited by PECVD, using silane, nitrous oxide
and ammonia
source gases.  Deposition temperature is normally around 350 degrees C,
pressure between
750mTorr and 1 Torr.  It is possible to deposit anything between silicon
dioxide and
silicon nitride by adjusting the proportion of gases.  Naturally, the
refractive index will
reflect the composition.  It is possible to control the refractive index
very accurately, which
is good news for anyone making waveguides using this material.
Drop me an email (martin.walker@oxinst.co.uk) if you need any details on
equipment for this
process.

Martin Walker

Mr. Martin Walker, Senior Applications Engineer
Oxford Instruments Plasma Technology
North End, Yatton, Bristol, BS49 4AP, UK
Tel. +44 1934 837031  Fax. +44 1934 837001

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