Hi Behraad,

have you had a look into localized waver bonding with laser? I use this
process with glass to silicon, but it might work for silicon to silicon too.
What's about the lateral dimensions, is there some "space for a bonding zone
that can heat up without destroying your metal layer?
The oxides should not harm the process at all as long as the surfaces are
flat and clean.

Hope this is helpful!

Regards,

Reiner


<[ -----Original Message-----
<[ From: Behraad Bahreyni [mailto:[email protected]]
<[ Sent: Monday, January 26, 2004 6:53 PM
<[ To: [email protected]
<[ Subject: [mems-talk] Wafer Bonding Problem
<[
<[
<[ 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                          |
<[            _________________________________________________
<[
<[
<[
<[
<[