[Fwd: Couple of requests from MEMS Exchange]

Jim McVittie mcvittie at snf.stanford.edu
Tue Aug 31 10:48:23 PDT 2004


Regarding item #1, I have never intentionally etched silicon nitride with a
chlorine based process. While Mo etches best in an F based etch, it should etch at
a slower rate in a Cl based etch.  I say this because the boiling points of MoF5
and MoCl5 are 35 C and 268C, respectively. Note that the boiling point of TiF4 is
284C and we often etch Ti is SF6 plasmas.  If  the requestor has a ref for nitride
etching in Cl2, we can look into doing it in the Pquest.

Regarding item #2, we have etched pieces in the Al chamber on the P5000. However,
we have not tried to mount 2” wafers onto 4”. The mounting process uses
doublesided carbon tape to attach the pieces and resist to seal the edges. It is a
pain to get off all the tape residue after the etch. I am willing to try other
mounting methods but one does need good thermal contact between the carrier wafer
and pieces to get good etch results.


Mary Tang wrote:

> I think these are questions for Jim...  and I've a couple more to add
> regarding logistics...
> 1.  I don't believe that Nancy (and please correct me if I'm wrong, Nancy) is
> going to feel comfortable doing this etch on the pquest.  Is there any chance
> that you or someone you feel is knowledgeable about the pquest could do this?
> If not, then I suggest that MEMS exchange try to find another site to do
> this.   Nancy -- if this could be done here, could we get more info from the
> customer as to what the process requirements are?  (I presume that Moly/C are
> pretty robust against Cl, but no idea how much, and it seems they are
> concerned if they want to avoid Fl...  Is Moly/C a shiny reflective
> substrate?  I mean, can we use the nanospec to measure nitride?)
> 2.  Can smaller pieces be mounted on 4" wafers for processing in the P5000?  I
> know this has been done, but gather that it's on a case-by-case basis?  Are
> carbon dots acceptable?  I think you had mentioned that your technical
> contacts at Applied used a certain adhesive...  is this something that's been
> investigated here?
>  Jim -- what do you think?
> Mary
> Nancy Latta wrote:
> > Folks,
> >
> > I sent these requests to Spec Mat a week ago.  Any progress?
> >
> >   ------------------------------------------------------------------------
> >
> > Subject: Couple of requests from MEMS Exchange
> > Date: Wed, 18 Aug 2004 09:36:01 -0700
> > From: Nancy Latta <latta at snf.stanford.edu>
> > To: specmat at snf.stanford.edu
> >
> > Folks,
> >
> > The MEMS Exchange people has asked me to ask about two etch proccesses;
> > 1) They have a customer that has nitride over Moly/carbon on a Si
> > substrate.  They want to use a Cl process to etch the nitride and expose
> > the Moly/carbon.  Any chance pquest can be used?  They do not want to
> > use a flourine process.
> >
> > 2) Another customer wants to etch Al/3%Ti off a SiC substrate.  I need
> > to check about the cleanliness of the sputtered metals, but the first
> > problem is that the samples are 2 inch.  They are suggesting that we
> > mount them to a 4 in wafer and use p5000.
> >
> > Thanks for your reply,
> >
> > -Nancy
> --
> 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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