Hello,

In continuation to my previous posting (XeF2 attack on
Tungsten), I have another question.

Does XeF2 etch on Si leaves any residue??

I am trying to etch Si wafer which is bonded to
another wafer. Both the wafers has Au patterned on
them and are Au-Au thermocompression bonded. The top
wafer (which is etched in XeF2) has the Tungsten
adhesion layer between the gold and silicon wafer.

After the complete removal of the top silicon wafer
(STS DRIE and XeF2 etches), I can clearly see that the
Tunsten is etched away completely which confirms the
answers from the previous posting.

Also, I can find some residue left on the bottom
wafer. I have performed the EDAX on the material that
was scattered on the entire Au and SiO2 layers on the
bottom wafer. The content of Si is more than any other
material.

I was wondering if the Si etched in the XACTIX got
redeposited as a thin layer on the bottom wafer?? Or
is it the thin native or virgin oxide of the bare
silicon top wafer that was etched??

Your suggestions are highly appreciated.

Thanks,
Kris