Jamie:

Often the adhesion layer is not attacked, but because of pin holes and
micro-cracks in the metal films, the HF based etchant can leak through the
film(s) and attack the glass under the metal film causing metal lift-off  W
won't work any better, in fact it gets etched in HF based etchant.  Your
best bet is still Au/Cr double layer, but take extra care in cleaning your
glass substrate prior to metal deposition to minimize pin-holes.  You may
also want to minimize film stress (make it slightly compressive if
possible), and use relatively thick metal (100nm Cr, 250nm Au for example).
If you have access to poly silicon and SiC films, they can also be used as
good mask for deep glass etch.

Yuebin Ning, Ph.D.
Norcada Inc.
#3, 9808 - 47 Avenue
Edmonton, AB, T6E 5P3
Canada
Phone 780-431-9637, Fax 780-431-9638
Email: Yuebin@norcada.com


> Message: 1
> Date: Tue, 11 Mar 2003 11:59:22 -0800
> From: "Zhimin J Yao" 
> Subject: [mems-talk] mask material for wet etch glass
> To: mems-talk@memsnet.org
> Message-ID: 
> Content-Type: text/plain; charset=us-ascii
>
> Hi,
>
> We are trying to etch about 0.5 - 1mm deep into glass or quartz using a
> metal mask.  Au did not work well because the adhesion layer got etched.
> Does anybody know what metal works the best?  Anybody tried W?
>
> Thanks,
> Z. Jamie Yao