RCA Clean: Changes to the prefurnace clean

Dear Labmembers:

We would like you to be aware of upcoming changes in the standard pre-furnace clean procedures.  Instead of the 4:1 sulfuric-peroxide/HCl-SC2/HF dip sequence that has been standard at SNF for many years, the plan is to change to a standard RCA SC1/SC2/HF dip clean at 50C.  Experiments are underway to validate procedures.  The scheduled date for implementation is Aug.2. 

The reasons for this change are: 

1. Safety – SC1 runs at a lower temperature and much lower concentration than piranha.
2. Better quality clean –Over 40 years of research and practice have gone into silicon wafer cleans; but best known practices remain based on the RCA mix.  In fact, the RCA clean is being routinely used by some labmembers now. 
3. Requirements of new research – Sulfur from the standard clean has long been known to be contaminant in our lab appearing even in furnaces.   With more researchers in nanowires, organic transistors, and biodevices, sulfur contamination is becoming a serious concern. 
4. Lower chemical costs – We can expect to save over $20K/year at the usage rates of 2009-2010.  And this allows us to reduce our chemical inventories in preparation for the lab renovation.

The plan:

1.       One hot pot at wbsilicide will be converted over to the new RCA SC-1 clean, effective Friday, July 22.  Users for the last 6 months have been notified. 

2.      The station at wbdiff will be converted to the new RCA clean on August 2.  Training materials will be updated and and a “white paper” describing the rationale and implementation will be posted for labmembers.

Several EE faculty and senior staff fully endorse this change; key AdCom faculty have been notified.  No change is completely without risk, but this is believed to be minute.

Please do let us know if you have any concerns.

Thanks for your attention,

Your SNF Staff