Hi, All,
Thank you very much for those who replied my email and gave me precious
suggestions. Here I summarize the answers and attach my recent experiments
as well.

ORIGINAL:

I have metal layer (Cr 300A, Au 1200A), the patterns are 1um features with
1um spaces. I use ion mill to etch the metal with PR (897-12i) as the mask.
After the etching, it is hard to clean the PR ( I use hot 1165 remover).
There are residue attached on the pattern.
Any suggestion is highly appreciated. Thanks in advance.

Yahong

ANSWERS:

1)  From:         "Shuwen Guo" 
Try dry etch by using Asher (oxygen plasma).
Shuwen Guo

2) From:
        Winston Chan 
I always use an oxygen plasma etcher (time and conditions to remove
about 100 nm of photoresist, conditions vary with etcher) before
stripping the photoresist in acetone. If you do not do the plasma
etching before stripping, I have found no way (without damaging the
substrate) of removing the residue.

Winston

3) From:
        BobHendu@aol.com
I am working on a technique for removal. You would have to etch the
underlayer of approximately 4,000 angstroms prior to gold etch. Would that
be
a problem? You can contact me at 602-524-2576 if you want to discuss
further.
Bob Henderson bobhendu@aol.com

4) From:
        Ranganathan Nagaranjan 

        You need to do Deep UV bake before etching so that the resist does
not get hardened.
        Ion milling causes lot of resist hardening. There is a standard
system available to do UV treatment before etch or ion implantation.

        Good luck.
        Ranga


5) From:
        Charlie Emrich 
Sounds like you're friying your resist.  Ion mills are
designed to run the wafers cool.  Make sure the
cooling water to the substrate table is flowing to
spec.  Also, make sure that your wafer is adequately
attatched (thermally) to the table.  I used to use a
silver loaded silicone past from Transene (Danvers,
MA).  Also, using diffusion pump oil with Al powder
works well.  If you still run into problems, back off
on your neutralizer current (it's a great black body
source) - this will mean that you'll have to lower
your accelerator voltage accordingly.

Good luck!

Charlie

Mathies Research Group
UC Berkeley

6) I am sorry that I lose another colleague's message. He suggest me to use
Branson for about 30min.


RECENT EXPERIMENTS:
I think the measure you take depends on the specific situation. In my case,
Au is on the top and it sputters in Plasma Ashing. My lesson and experience
were: In the ion milling, alternating etching and cooling processes (15sec
etching and 45sec cooling). The accumulated etching time was 2.5min. I used
500V and 100mA for 4" wafer substrate. After that, the wafer surface is
pretty much clear under microscope and the metals (Cr 300A and Au 1200A) are
etched through. What I did afterwards was put them in Branson for 5min
(1000W). This ruined the whole thing. The Au on wafer edge almost gone and
the metal surface became dark. This dark stuff was the residue I believe and
it was hard to remove.
Another thing I found was after accumulated 4 min (or less) etching, the PR
became residue.
In my situation, after the ion milling, I need etch away the 1.5um SiO2
underneath the metal, in order to protect the Au surface, I put 1000A or
less Al on top of Au. So for ion milling, the multilayer was Cr/Au/Al, it
need longer time to etch through. After 2.5min milling, clean the surface PR
and add more milling time utill through. The Al was thinned but it was still
enough for SiO2 RIE mask. That works quite well.

Good Luck.

Yh
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