Request to use lampoly or p5000 to etch semi-clean wafers

Ed Myers edmyers at stanford.edu
Fri Oct 9 11:29:35 PDT 2009


It's OK with me, but we should let Nancy chime in.

At 10:07 AM 10/9/2009, Jim McVittie wrote:
>Mary,
>
>Back at the beginning of time, we wanted to keep all metals of the Lam and
>push requests like this to the P5000. The idea was to reserve the Lam for
>frontend processes where being metal free is most important. However, yrs
>back when we did TXRF measurements on the Lam, we found that it was no
>better then the P5000 Si chamber and the key was the post etch cleaning.
>So I do not think it make much difference from a metal contamination
>viewpoint whether this work is done in the Lam or P5000. Since this is not
>a high resolution etch, I would recommand he use the P-5000. By the way,
>the Lam intrically has Al comtamination because of its clamp.
>
>         Jim
>
>On Fri, 9 Oct 2009, Mary Tang wrote:
>
> > Hi all --
> >
> >
> > We really need to get back to this question of how we are going to
> > accommodate requests for metal-containing materials in clean dry etch
> > tools.  This request strikes me as being an incremental step in that
> > direction....
> >
> >
> > As for as lampoly is concerned (and I suspect would also apply to
> > P5000etch), this seems reasonable.  The EBR margin should be sufficient
> > (a wafer without EBR risks sticking to the lampoly clamp ring.)  And the
> > clamp is made from alumina, so I don't think there's an appreciable
> > contamination risk from whatever trace Al may remain on exposed wafer
> > surfaces.
> >
> >
> > I vote that we OK this request -- with the proviso that we update the
> > documentation to describe in detail the rationale and conditions under
> > which semi-clean wafers can be processed in lampoly (and p5000etch.)
> >
> >
> > So...  do we have a quorum?
> >
> >
> >
> > Mary
> >
> > Nahid Harjee wrote:
> > > SpecMat,
> > >
> > > I am designing a process to fabricate single crystal silicon
> > > cantilevers that are 3 um thick. The narrowest cantilevers are 14 um
> > > wide and have 4 "legs" at the clamped end that are 2 um wide. I am
> > > trying to select a tool to etch the 3 um of silicon to define the
> > > cantilever that will produce straight sidewalls. In the past, I have
> > > used stsetch to define wider cantilevers. However, I am concerned that
> > > the scalloping resulting from this tool will make it difficult to etch
> > > the 2 um legs of the new design. Thus, I am writing to propose that I
> > > perform this etch with HBr/Cl2 chemistry in lampoly or p5000. What
> > > makes this process non-standard is that my wafers will be semi-clean
> > > at this point. The step prior to defining the cantilevers is
> > > deposition of 1500 A of Al in gryphon which is then patterned with a
> > > wet etch in Al-11. During the Si etch, the Al will never be exposed to
> > > the plasma (it will be covered by 3 um of resist). However, there is a
> > > chance that there will be trace Al on the exposed Si from the Al-11
> > > bath. At the most recent process clinic, Keith Best raised the point
> > > that there may be exposed Al in the EBR region of my wafers. In order
> > > to minimize this possibility, I can use 5 mm EBR for the Al litho and
> > > 2 mm EBR for the cantilever litho, ensuring there's a buffer of 3 mm
> > > of resist with no Al below it.
> > >
> > > I look foward to hearing your decision on the proposed process or if
> > > there is a tool that is better suited for this process, I welcome any
> > > suggestions.
> > >
> > > Thanks,
> > >
> > > nh
> > >
> > > --
> > > Nahid Harjee
> > > Ph.D. Candidate
> > > Electrical Engineering
> > > Stanford University
> > > 408-761-8651
> >
> >
> >
>
>--
>--------------------------------------------------------------
>James (Jim) P. McVittie, Ph.D.          Sr. Research Scientist
>Paul G. Allen Building                  Electrical Engineering
>Stanford Nanofabrication Facility       jmcvittie at stanford.edu
>Stanford University                     Office: (650) 725-3640
>Rm. 336X, 330 Serra Mall                Lab: (650) 721-6834
>Stanford, CA 94305-4075                 Fax: (650) 723-4659





More information about the specmat mailing list