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

Chris Kenney kenney at SLAC.Stanford.EDU
Wed Feb 18 10:20:29 PST 2004


Hi Mary,

Thanks for your reply.

I discussed all the details with Jim and Uli in December.

My impression is that Jim has a permit form the county to
dispose of a modest amount of ethanol down the HF drain.

I was lacking official permission from specmat to proceed.

I will talk to Uli and Jim again to make sure I understand
the details of how I should do this before performing the etch.

Thanks for your help.

Chris

On Wed, 18 Feb 2004, Mary Tang wrote:

> Wups!  Sorry, I meant to follow up.  I believe Jim McVittie went through
> this exercise and it was decided that this chemical mixture and the
> first rinses of labware and wafers, should all go into the HF drain.
> The only concern is that ethanol is a flammable solvent and that other
> people using wbgeneral may put HNA (which contains nitric, an oxidizer
> and a no-no with regard to flammables) into the sink as well.  It is
> thought that the dilution from other HF tanks and such would make it a
> non-issue, particularly if the volume and proportion of ethanol were
> relatively small.  Alternatively, to be on the extra-safe side, it may
> be better to simply collect the waste in a labelled hazardous waste
> container and deal with it according to standard procedure.  I'll double
> check with Jim and get back to you on this.
>
> As for the set up -- Uli and Jim Haydon have gone through this before
> with another user in the last year or so.  Please work with them on the
> logistics of scheduling, setup, etc. at wbgaas.
>
> Again, my apologies for the delay -- I'd forgotten about the SpecMat
> files.
>
> Mary
>
>
> Chris Kenney wrote:
>
> > 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
>
> --
> Mary X. Tang, Ph.D.
> Stanford Nanofabrication Facility
> CIS Room 136, Mail Code 4070
> Stanford, CA  94305
> (650)723-9980
> mtang at stanford.edu
> http://snf.stanford.edu
>
>
>



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