Joachim,
It sounds like a trapped layer of moisture in the top surfaces of the
PECVD SiN. If you have access to a Vacuum vapor primer, you can dehydrate and
seal the surface with a monolayer of HMDS immediately after the PECVD step. Or
treat the surface immediately before the evaporation with an inert gas Argon or
Nitrogen plasma to remove the top moisture containing layer of material. Bill
Moffat
-----Original Message-----
From: Oberhammer Joachim [mailto:joachim.oberhammer@s3.kth.se]
Sent: Friday, November 22, 2002 7:18 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] adhesion-layers for Au evaportation onto SiN
Hi researchers,
I have adhesion problems of evaporated Au (150 nm) to PECVD SiN (300
degC, 1 um). I'm using a Cr (50 nm) layer as adhesion. Both
evaporation processes (Cr+Au) are done in the same machine together.
I don't use any surface treatment of the SiN before the evaporation.
After exposure of the structures to O2 plasma (1000 W, 100 mTorr, 700
sccm O2) for 15 min, the Cr/Au layer is pealing off. The temperature
during the O2 plasma etch is between 150 and 200 degC.
Questions:
(1) is the off-pealing caused by the temperature during O2 treatment,
due to stress?
(2) how can I improve the adhesion? What kind of surface preparation
of the SiN do you recommend before the evaporation of Cr/Au (like O2
plasma ...)?
Thanks very very very much for any comment,
Joachim Oberhammer/KTH Stockholm.
--
------------------------------------------------------------------------------
Joachim Oberhammer, Dipl.-Ing.
Royal Institute of Technology (KTH) Phone: +46/(0)8 790 6250
Dept. of Signals, Sensors and Systems Fax: +46/(0)8 10 0858
Microsystem Technology (MST) Mobile: +46/(0)70 692 1858
e-mail: joachim.oberhammer@s3.kth.se
Osquldas väg 10 homepage: http://www.s3.kth.se/mst/
SE-100 44 Stockholm, Sweden
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