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