Hi,
After I have patterned some gold conductors on SiO2 wafers and
lifting-off the resist, I tried plasma treatment with the conditions
250W, O2 plasma at 10sscm (171 mT) for 20-30mins.  It turned out that
there were some resist being burned away and become blackened.  The
blackened resist stringers remained on the gold conductors and these are
very difficult to remove.  I have tried combinations of Piranha
(H2SO4:H2O2 = 3:1) at 80-90'C for up to 1 hr, SC1 (NH4OH:H2O2:H2O =
1:1:5) for 15mins as well as AZ300T resist stripper but all these are
unable to remove the blackened resist stringers.

After all these chemical cleans, the SiO2 surface is very clean but the
gold conductors are still stained with the blackened resist stringers.

Can anyone suggest how I could more effectively remove these resist
stringers?  Thanks!

Jeffrey