Zia--
Peeling is partially the result of poor adhesion, which is often due to the
surface being dirty.
Because you have Cr on both sides of the wafer, I'm guessing that you coated
the top side first, then flipped the wafer over and coated the back.
The back may have gotten dirty during this process.
One solution would be to use Kapton (polyimide) tape or a metal clip to hold
your device wafer to a clean dummy wafer.
If you can sputter-clean the surface of your wafer, do that as well.
Another thing that helps a film peel is high stress, either tensile or
compressive. The worse the adhesion and the thicker the film, the less
stress it takes for the film to peel.
Due to the relatively low pressure you are using, you might double the
sputtering pressure to shift the stress toward tensile.
If you have a wafer-curvature-measurement tool, you should use it to
determine stress and adjust the pressure accordingly.
I would not recommend annealing the Cr, as it will form chromium silicide
above some temperature, which may be harder to remove.
--Kirt Williams
----- Original Message -----
From: "Ziaur Rahman"
To:
Sent: Monday, May 01, 2006 2:18 PM
Subject: [mems-talk] Need a recipe for Cr Sputtering
> Hello
>
> I need to use KOH as anitropic etchant to etch silicon.
> I sputtered Cr as mask. The recipe I used is:
>
> 200 W DC, 4 mtorr pressure at room temperature.
> It gave me 600 nm Cr film on silicon wafer.
>
> When I immeresed the wafer in KOH solution (44% by weight
> at 85 Deg. C) for 5 minutes the Cr on back side of the wafer
> was peeled off and in the front side of the wafer the Cr became dull
> (though it did not peel off). Do I have to anneal the Cr after
> sputtering or do I need to use higher temperature during sputtering?
>
> Can anyone give me a good recipe for Cr Sputtering?