Sanjay,

Have you diced the wafer? Very often people use "city water" for the
cooling during dicing. The chlorine from this water will cause
corrosion, if you are not careful to rinse them well in DI water. We
have Carbon Filters on our water.

Just a thought.

Charles Ellis...
Director, Auburn Microelectronics Laboratory

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf
Of Kirt & Erika Zipf-Williams
Sent: Thursday, November 13, 2003 2:36 PM
To: General MEMS discussion
Subject: Re: [mems-talk] Protecting Aluminium Bond Pads from Corrosion


> Guys,
>       Any advise on this subject.  The Aluminium Pad size is
> approximately 500um X 500um and the leads are protected by the
> Passivation Layer.  I experience Corrosion problem only on the Bond
> Pads.  Bond Pads are opened using RIE etch process. Thanks,
>
> Sanjay Thekdi
> 375 Los Coches Street,
> Milpitas, CA 95035

This might be your problem:
If aluminum is plasma etched, a chlorine-based (Cl2, BCl3, etc.)
chemistry is used. Some Cl is left on the surface after etching. When
exposed to water or water vapor in the air, hydrochloric acid is formed
that corrodes the aluminum. The solution to this problem, found on
commercial aluminum etchers, is to add an addtional process chamber that
runs a flourine-based plasma. The F displaces the Cl on the surface and
does not create a problem later.
   --Kirt Williams, Ph.D.  consultant


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