Hi Everybody,

We have a problem in our silicon nitride PECVD process.

There is a short (about 1 cm), white, hot discharge appearing at only one
showerhead hole at a time. When it occurs, it usually happens a few minutes
into an apparently normal deposition. Besides the visible appearance of this
phenomenon, its presence is also evident from a dramatic change in bias
voltage. If left glowing for more than a few seconds, the discharge
generates enough heat to begin melting the area around the hole. The effect
seems to occur at a hole situated on one of the inner gas distribution rings
of the showerhead, near, but not necessarily immediately adjacent to, the
gas inlet.
There is also evidence of reaction (deposits) on the back side of the
showerhead and even damage to the stainless steel screen in the gas inlet
tube.
More than that, sometimes the Plasma bulk stick to the top electrode on some
area of the top electrode (there is no dark sheath between the plasma bulk
and Cathode).

I apologize for long e-mail and appreciate any help in advance.


With best Regards


Kourosh Khosraviani
Master of Applied Science Candidate
Simon Fraser University
School of Engineering Science
Burnaby, BC, Canada