hi Behraad
your problem can be sorted out by cleaning in oxygen plasma. tratment with
oxygen plasma gives contact angles near to zero and it would enhance the bonding
process if bonded immidiately after plasma treatment. but you have to be sure
that your process is clean enough so as not to leave any particles on surfaces
after plasma treatment.

Sunil K Taya
MEMS & Microsensors Group
CEERI, Pilani(Raj)
India-333031

Behraad Bahreyni  wrote:
Hello Everybody,

I want to bond two Silicon wafers which are coated with a 2um layer of
CVD oxide. The oxide layer on one of the wafers is recessed and 1um of
metal (gold) is deposited (and patterned) inside the recessed region
(please check the illustration below). Since I have the metal layer on
the bottom wafer, I can not do an RCA clean on that wafer. This may
cause some photoresist to remain on the oxide layer, which as far as I
now, will cause bonding problems. Moreover, because of the metal layer,
I can not use high temperatures for bonding. An oxygen plasma cleaning
is possible, but I am not sure of its effect on bonding process and
quality.

Does anybody have any experience with cases similar to this scenario?
I will highly appreciate any help and/or references for bonding this
kind of structures.

Thank you in advance,
Behraad


_________________________________________________
| Oxide |
_________________________________________________
| |
Top | Silicon |
Wafer | |
_________________________________________________
| Oxide |
_________________________________________________

______________ ___________
| \ / |
| Oxide \ / Oxide |
________________=======Metal========_____________
Bottom | |
Wafer | Silicon |
| |
_________________________________________________
| Oxide |
_________________________________________________



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