Hi I don't know whether LPCVD will do the trick,also depending how thick a film.
You may want to consider PVD sputtering.

It worked well for us.

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----- Original Message -----
From: "Roger Shile" 
To: "General MEMS discussion" 
Sent: Monday, August 17, 2009 9:32 AM
Subject: [mems-talk] Source for Low Stress Silicon Nitride

> Can someone suggest a commercial for low stress silicon nitride with low
> stress gradient?
>
> Low stress gradient is important as the films will be used to fabricate
> free standing beams which must remain straight when released.
>
> Roger Shile
>