Mike

  Michael

  Thanks for your response. I did the cleaning earlier also with O2 plasma,
which is a recommended plasma clean chemistry for polymer etching chamber. But
this time I spent whole day in trying different gas chemistry with SF6+CHF3+O2
and O2 alone in combination with high pressure (750mTorr) and low pressure
(250mTorr). I don't know which one worked. But it worked successfully and I am
not getting any flickering even at 30mTorr.

  Thanks for your suggestion

  With regards,

Pramod Gupta
21084 Red Fir Court
Cupertino, CA 95014
Phone: (408) 253-1646

Mike Stan  wrote:
  Pramod,

What you are seeing is likely local arching within the plasma. Local
arching can create feedback that causes the plasma to "flicker" as you
say. This is usually caused by organic contamination that is outgassing
or even sputtering during the etch cycle. Higher power levels will also
exacerbate the problem as will moisture in the chamber. Tuning the
current or plasma density is key to a robust process. I am curious if
you would see "sparkles in the plasma at lower power levels, say 125 -
175W. As you know the [F+] radical is very reactive and can be prone to
external reactions. What I have found to be of help in the past is a
thorough polymeric residue clean of, not just the chamber, but the
electrodes as well, followed by a bake out under HiVac to drive off
moisture.