Hello,

I have some troubles in protecting Chrome film in TMAH. The Cr was
sputtered on PECVD SiO2 and was fine in TMAH if the PECVD SiO2 was
more than 0.5 um thick. But the Cr lines were peeled off after 1-hour
etching if the oxide film was thinner than 0.3 um. I suspect that the
thin oxide film was porous and TMAH creep under the Cr and etch the
Chrome oxide or SiO2 at the interface. In my process, it is desirable to
use ~ 0.2-um thin oxide film, on which Cr is sputterred. Could anyone
give me some suggestions on how to protect the Cr in TMAH?

One way that I have in mind is to use tungsten to protect Cr. I was told
that tungsten is resistent to KOH and suspect that it may also be fine in
TMAH. So I would like to try sputtering W to cover Cr and SiO2 before TMAH
etching. After TMAH etching, I could use H2O2 to strip W. Will this idea
work?

Li Shi

Mechanical Engineering Department
University of California
Berkeley, CA 94720
E-mail: lishi@newton.berkeley.edu
Phone:  (510)643-3007
Fax:    (510)642-6163