Pquest users' meeting summary

[Mary Tang]

Dear pquest users --


Many thanks to those who attended and for the contributions by those who 
couldn't.  The meeting was well attended (even two faculty!) and 
well-represented by many different groups.  Here's a summary:


1.  Chlorine versus fluorine, 2011.  Because there are many more 
chlorine than fluorine users, it was decided to increase the 
chlorine-only time.  Starting in 2011, the schedule will be 1.5 weeks of 
chlorine-only after chamber clean followed by 0.5 weeks of 
fluorine-allowed.  Chamber cleans will be done on alternate Fridays.  
This will keep the current chamber clean frequency, which is good, and 
allow fluorine users access twice/month.


2.  Chlorine versus fluorine, 2010.  The system will remain 
chlorine-only until next Friday, Dec. 10, when it becomes 
fluorine-allowed.  A chamber clean will be done over the shutdown.


3.  Process problems.  Several people have observed variable etch rates 
in ZEP, PMMA, and GaAs.  One group's problems seem to be recently 
resolved.  Some reminders on pquest operation which will help with 
process control:  monitor DC bias voltage (and adjust RF accordingly); 
run O2 clean until DC bias stabilized; check (and rezero if needed) the 
VAT pressure controller; run recipes with chlorine flows within 
controllable range (3 sccm is recommended); use ellipsometry to measure 
resist thicknesses below 1000 A.


4.  Shutdown.  Elmer plans to repair the noisy clamp, clean the chamber, 
check for chips in the darkspace, and adjust the clamp pressure to try 
to get the helium blow by down a little.  Stray chips in the darkspace 
have been historically known to cause variable etch rate or plasma 
flickering.  The clamp pressure is a balancing act between good backside 
cooling and wafer breakage so needs to be done carefully.


5. Other stuff discussed:  instituting logsheet data entry on Coral 
disable - this will allow us to collect and monitor data (like DC bias); 
defining a basic process qual, to check machine functionality; 
temperature dots are available to check for substrate heating; optical 
spectroscopy testing for fluorines or chamber cleanliness.


Again, thanks all.  We would also like to encourage everyone to share 
observations about pquest process performance, especially any problems 
you encounter.


Team Pquest Etch (Jim and Jimmer, Elmer, Mary)

-- 
Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
(650)723-9980
mtang at stanford.edu
http://snf.stanford.edu