wbgen2 TMAH Bath

Mary Tang mtang at stanford.edu
Mon Jul 20 16:05:56 PDT 2009

Hi Raja, Gaurav --

Sorry for the delay.  Your request to use the Lufran TMAH etch bath at 
wbgen2 for PRS-1000 resist clean of Ge substrates is hereby OK'ed. 

- The bath has previously been used, but for only for TMAH (no KOH) on 
non-gold-containing substrates, so gold and potassium should not be a 
concern.  However, please decontaminate using 5:1:1 Water: 30% hydrogen 
peroxide: Conc. HCl before your use.  The tank has a drain to AWN, so 
you should be OK. The bath heater is mounted below a perforated teflon 
plate.  There's a lot of surface area, so you should rinse a bit better 
than you would normally on a regular quartz bath.

- You should rinse the bath with a little PRS-1000 a few times before 
using.  Any residual water in the bath will not be good for the PRS-1000.

- As mentioned, the bath heater is below perforated teflon plate.  The 
thermocouple tip is just about an inch or two above the plate.  We want 
to make sure there's adequate thermal mixing, which will be more impeded 
(with the teflon plate) than in a regular quartz bath.  This can be done 
with the N2 sparger (flow a little N2 which bubbles up through the 
plate) but I'm not sure what this may do to Ge.  You can also make sure 
to mix by dunking the cassette at regular intervals to ensure mixing.  
Jim 's suggestion (which is a very good one) is to turn the sparger on 
while the system is heating (to ensure mixing) and turn it off when you 
dunk your cassette, making sure to lift the cassette in and our every 
couple of minutes to ensure good mixing.  Turn the heater off when 
you're done.

I've got Jim's manuals at my desk, if you are interested in looking at 
the controller operating procedures -- but it seems pretty 
straightforward.  If there is trouble with the temperature stabilizing, 
there are PID settings which you should use. 

Let me know how things go --



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

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