Dear  Hongtao,

i have faced similar problem in past but it got rid from this.
you may increase the Au thickness (if Possible for your requirement) upto
500nm. Rotation of the wafer during deposition may serve good for almost
pinhole free film.

you may also try annealing in nitrogen ambient at 250 degree Celsius for 60
min.

Hope that you may get rid of it.
Good Luck,

Manish Hooda

----- Original Message -----
From: "Tao" 
To: "General MEMS discussion" 
Sent: Monday, October 23, 2006 4:40 AM
Subject: [mems-talk] pinhole free metallization


> Dear all
>     I am looking for pinhole free metallization. I am using KOH etching
> to release my device. But the eletric contact under the metal pads will
> be etched. I guess the reason is the pinholes in the metallization. I
> tried Cr 30nm/ Au 300nm, Cr 40nm/ Pt 200nm/ Au 200nm and other kinds of
> multilayer metallizations with both ebeam and thermal evaporatoration.
> But none of them give me desired results. Since Au is used, even 200nm
> Pt layer can not prevent it diffusing into Si with annealing at 400C for
> 5min (by RTA). Do you have some advices on pinhole free metallization
> without gold? Thanks in advance.