I need some help concerning wet etch. My sample is
Cr(3000A)/SiO2(4 micron,I know it's quite thick)/Si.
After UV lithography, and hard bake I want to etch Cr,
and Oxide down to silicon surface. I am having two
different problems. One is in Cr etch. Because I have
an array of windows I want to etch, there's some
uniformity issue. Some windows are etched, but some
aren't. I use 1040 type A Cr etch from transene
company for Cr etch. What are common conditions in
using this kind of etchant? Should I heat it up? or
stir the etchant during etching?

My second, and more challenging problem is in oxide
etch. I use 49% HF to etch SiO2. Usually it takes
about 3-4 min. As is well known HF etches oxide
leaving isotropic etch profile. So I have a severe
undercut. And that always causes the overhanging Cr
layer around edge break down. I'd like to keep this
undercut profile, but have to find out some solution
to prevent breakage of Cr layer. Should I deposit
thicker Cr? (Cr was deposited thermally)

Lastly my etch mask is Shipley 1813 positive PR.
Thank you for any advice or comments.

-Soojin
North Carolina
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