Status? - DI/Ethanol/HF Request (fwd)

Chris Kenney kenney at SLAC.Stanford.EDU
Tue Feb 17 12:07:35 PST 2004


Dear Specmat,

Could you let me know the status of my request to perform
photo-assisted, electrochemical etching using a DI/ethanol/HF
solution?

Do you need more information from me?

Are there issues we should discuss?

Thank you for your help.

Chris

---------- Forwarded message ----------
Date: Tue, 27 Jan 2004 01:07:38 -0800 (PST)
From: Chris Kenney <kenney at slac.stanford.edu>
To: specmat at snf.stanford.edu
Cc: sher at slac.stanford.edu
Subject: DI/Ethanol/HF Request

Dear SpecMat,

Our group would like to develop a photo-assisted, electro-
chemical etch process for making high-aspect ratio holes
in silicon substrates.

The basic setup involves a container which holds the silicon
wafer against a window on one side. This is sealed using
an O-ring. One side of the wafer will be exposed to the
etching solution and the other side to the ambient air and
a light source.

The entire apparatus will be set inside a secondary containment
basin. This basin in turn would be inside the sink at the wet bench.

So there would be 3 levels of nested containers for the solution.

Electrical contact is also made to the air-side of the wafer.

There are two platinum electrodes immersed in the solution iside
the container: a reference electrode and a field electrode.

In use, a potential of about 1 Volt will be applied between
the field electrode and the silicon wafer. We expect total
electrical currents used in the system to be less than
100 milliAmperes.  The power source will have current
and Voltage limits set near these values for safety.

The power source is a Keitheley 2400 source meter. It would
be located away from the interior of the wet bench and close to
the floor to avoid a fall hazard.

The solution will consist of approximately 75% water and
25% ethanol with a small amount of HF. The typical HF concentration
would be between 4% and 6% by weight.

It seems that the unusual aspect of this request is the
use of a mixture containing both an acid and a solvent.

I'm unsure of the best method for disposing of this solution
after use.

We feel the most appropriate location for this set up is the
GaAs wet bench. We would use less than half of the bench and
would remove our set up when it wasn't in use to avoid
getting in the way of other users.

We welcome all suggestions and comments on the best way to proceed.

Feel free to ask any questions.

We would like permission to use the GaAs wet bench for this work.

Thanks for your help.

Chris




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