Etching mask for TMAH

Kim, Han-jun hjkim at
Fri Apr 4 11:38:31 PST 2003

Hi, Mr. Kim

I don't know if there's any wax, or polymer, withstanding 
the base. In my experience, most of them didn't. Both oxide 
and nitride work great, as you may know, except that a 
long-time etch leaves some unwanted hillocks behind. 
Some metals - like Au - are known to work also. But I don't 
have much experience in this domain. 

If making a mask hinders you from working on Si-materials, 
you may use so called "soft lithography" with transparency 
films, a laser printer and an old-fashioned contact printer 
which doesn't care too much about the size and dimension of 
the substrate. 


Han-Jun Kim           Hewlett-Packard Lab.
(650) 857-8525        1501 Page Mill Rd.
(650) 857-8948 FAX    MS 1198
hjkim at      Palo Alto, CA 94304

-----Original Message-----
From: Hyoungsub Kim [mailto:hsubkim at]
Sent: Friday, April 04, 2003 12:51 AM
To: labmembers at
Subject: Etching mask for TMAH 

Dear lab members.

These days, I'm trying to etch a small piece of Si (dia. 3mm) from the
backside using TMAH at my lab w/o patterning.
I want to make a small hole in the center to make TEM sample, however, it is
hard to find a suitable mask (like wax type) to cover unwanted area.
I tried several waxes but all are easily soluble in TMAH. It should be
easily removed after Si etching.
I would appreciate if anybody can let me know possible material.
Thanks a lot.

Hyoungsub Kim

Ph.D Student
Materials Science and Engineering, Stanford
E-mail : hsubkim at
Phone : (O) 650-725-2616
             (H) 650-497-3516
             (FAX) 650-725-4034
Address : (O) Rm 203 McCullough Bldg, Stanford, CA94305

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