This is based on a typical MEMS Surface Micromachining Process.   It is
like a parallel capacitor with a fixed polysilicon electrode at the
bottom of the device and a movable doped polysilicon membrane on the top
that is grounded.  There is a thermal oxide or nitride deposited on the
fixed polysilicon to prevent electrical shorting between the two
electrodes.   Hope this give you enough details to answer my original
questions.

Thanks,

Nancy

-----Original Message-----
From: Tom Rust [mailto:[email protected]]
Subject: Re: Charge effects in electrostatic actuators

You've left out a lot of detail needed to help answer your question.

I'm assuming you are doing thermal oxide in silicon over a doped region
as the conductor. In this case, the surrounding silicon to the doped
region will have a substantial effect, depending on how highly doped it
is in the first place. There will be charge leakage through that
silicon, unless you form a p-n diode and reverse bias it - in which case
bipolar operation is out.

You don't indicate where the membrane is in relation to all this and how
it is driven.