Bruce,
Could you elaborate on the measurements done to observe the eutectic
formation.
Burns and Bright report that there is a decrease in reflectivity of Gold
as early as 250 C (Transducers '97). But your observations seem to show that
nothing happens till 325 C.
In my chips, I observed that Gold is terribly deformed after a few thermal
runs with temperatures ranging from 200-300 C. Gold has not peeled off of
poly2 but there are little deformations all over gold on the order of a
few tenths to few microns.
Any more observations/explanations will be appreciated.
Regards,
Vamsee Pamula
On Fri, 2 Jul 1999, Bruce H Weiller wrote:
> Regarding the temperature limit of gold in MUMPs devices; unfortunately gold
> forms a eutectic with silicon at 363 C. Our measurements with MUMPs die
> confirm this limit. We have recorded temperatures as high as 325 C with no
> apparent loss of gold. It would be helpful if MUMPs (Chronos) would
> incorporate a good barrier layer to prevent eutectic formation. Or better
> yet, offer an alternative metallization like platinum. Are you listening?
>
> If anyone has any good suggestions for a fix, I would appreciate them. Is
> plating a second metal on the gold a reasonable possibility? What metals are
> easy to plate on gold?
>
> Thanks in advance,
>
> Bruce H. Weiller
> The Aerospace Corporation
> PO Box 92957 / M2-248
> Los Angeles, CA 90009
> bruce.h.weiller@aero.org
>
>
>
>
>
>
> vkp@ee.duke.edu on 07/01/99 07:17:00 PM
> To: MEMS@ISI.EDU@Internet
> cc: (bcc: Bruce H Weiller/West/Aerospace/US)
> Subject: Specularity of Gold
>
>
> Hello All,
>
> Does anybody know the temperature at which a thin film (0.5 um) of Gold
> looses its specular property.
>
> In particular, I would like to know the temperature beyond which Gold
> looses its good reflectance and becomes rough, for a MUMPS fabricated Gold
> on Polysilicon2 layer with a thin Chromium adhesion layer in between.
>
>
> Thanks,
> Vamsee Krishna
> Dept of Elec Engg'
> Duke University
> vkp@ee.duke.edu
>
>
>
>
>
>
>
