Lithography developer

Mary Tang mtang at
Wed Jun 11 15:50:02 PDT 2008

Hi Cathy --

Are you collaborating by any chance with Chandra Ja in the Kenney Lab?  
I understand he is considering etching 1-3 microns of AlN deposited at 
Berkeley as well.  Could you please coordinate between the two of you to 
get more information from your collaborators at Berkeley?

I've contacted Sia Parsa, who's my counterpart at Berkeley.  He did not 
have a lot of specific information about processing of AlN and so 
suggested contacting the researchers who use this film at Berkeley.  So, 
I think there are a couple of processing issues that you should check 
with your Berkeley counterparts:

1.  The AlN etches somewhat in basic solutions, such as developer.  
However, Sia did not know if wet etch patterning of AlN could be done. 
If AlN can be appropriately patterned with wet etching, then this would 
be the easiest method.  However, you'd have to bias your mask if you 
want to define 10 micron lines in 3 micron films.

2.  Alternatively, AlN could be plasma etched in the p5000etch metal 
chamber, if it can be demonstrated that the AlN is CMOS clean.  The 
machine at Berkeley is considered by Sia to be CMOS clean, but they do 
not have data and processing is allowed on Pt-film coated wafers (which 
is not really CMOS clean.)  So, Sia could not say if the materials from 
this system could be considered clean for SNF.  If your counterparts 
have any data on trace metal contamination on AlN films deposited in the 
Berkeley Microlab AMS, it would be greatly appreciated.  If not, then we 
would require that a study be made.  This could be done either at the 
SNL (Rich Chin or Ann Marshal would be the contacts there) or at Evans 
Analytical Group, a commercial provider of analytical services.  
Typically, TXRF is used for contamination studies on surfaces, but a 
bulk film technique might be more appropriate in this case.  Usually, 
these techniques will detect a spectrum of metal contaminants -- the 
contaminants of interest would likely be Pt (since it is introduced to 
the system) and any likely contaminants from the chamber or deposition 
tool itself.  Please check out the Evans Analytical website, which has a 
lot of good information about different analytical methods.

Please work with Chandra to find out this information from your 
collaborators.  It would also be helpful to know if you plan to pattern 
your wafers here at SNF or at Berkeley.  If you want to use the CD-30 
developer here, you should check the compatibility with the resist you 
plan used here.

I suggest that you might consider coming to the next Process Clinic -- 
staff and SpecMat members will be on hand to help with processing and 
materials questions.  This will be 2-4 pm next Monday afternoon, in the 
open cubicle area next to Maureen's office.


Cathy Chiang wrote:
> Hi Mary,
> Sorry but one more bother, do you know with what machine we can do AlN 
> etch in SNF?
> Thank you very much,
> Cathy
> Quoting Cathy Chiang <cfchiang at>:
>> Hi Mary,
>> Thank you for the fast response. Yes, we collaborate with Berkeley and
>> will deposit AlN from their microlab. They use Shipley CD-30 to
>> pattern the feature. In our application, the thickness of AlN is
>> around 1-3 microns. And the feature size will be >200 microns with a
>> minimum line width >10 microns. Attached is the MSDS of Shipley CD-30.
>> Sorry that I have not got an updated version of the MSDS from the
>> company sales representative.
>> Thank you sincerely,
>> Cathy

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at

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