> Just curious if anyone has had experience in the removal of
> a tungsten oxide residue after a plasma process.  Currently running a CF4
> tungsten recipe that coats the process chamber, problem being the oxide
> coats the process chamber and in time causes a contamination issue.

Rather than tungsten oxide, you may have a fluorocarbon polymer coating.
My experience is that running pure CF4 creates a
fluorcarbon polymer coating all over the chamber.
Running a small amount of O2 with the CF4 greatly reduces the polymer
coating and improves run-to-run repeatability, but does etch photoresist
faster.

Try cleaning the chamber with an O2 plasma. You can also add Ar.

    --Kirt Williams, Ph.D.  consultant