Dear Craig,

There are many factors that will determine what the accuracy will be for
stopping in bulk silicon such as etch rate, exposed area, feature size and
the EPD used. If you have an STS system that you are working on for this,
please contact our process group at [email protected] who will be
able to help.

Andrew

------------------------------

Message: 11
Date: Wed, 10 Nov 2004 09:24:24 +0000
From: Keith Baldwin 
Subject: Re: [mems-talk] DRIE Etch Stop
To: General MEMS discussion 
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Craig,

I once tried to do something similar, but with a 10um membrane.  I never
actaully tested the repeatablility of the etch rate, but instead tried
to measure the depth of the feature (using a microscope) as it was
etched (the measurement error using the microscope was about 5um!).  But
even if you can get a repeatable etch rate, the real problem will be
uniformity across the surface of the wafer.  While a feature at the
centre of the wafer may have a 3um membrane, the features at the edge
are likely to be etched through.  In the end, I used SOI wafers with the
oxide layer as an etch stop.

Good luck,
Keith

Craig Lowrie wrote:

>Hello all,
>
>I am hoping that people out there with experience with the DRIE process
>could please tell me with what accuracy is it possible to get the DRIE
>to stop in a silicon wafer? I am wanting to be able to etch up to 300 um
>deep and be able to define a membrane thickness of 3 um with quite a
>high degree of accuracy.  Is this done by considering the etch rate?
>
>Regards,
>Cragi
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