Hello Hasan,

At first for a successful performing of a Silicon Fusion bond you need very
good substrate requirements like (for direct bonding):
surface roughness < 1nm, waferbow < 25µm, TTV < 5µm and a particular
free
surface preferably.

Furthermore it is a advantage to hydrophilize the wafer surfaces with a wet
chemical cleaning procedure. In our company we commonly use a Standard
Clean, so-called SC1 and SC2.
Piranha clean, H2SO4:H2O2 4:1, 10 minutes then
SC1: HCl:H2O2:H20 1:1:6, 75C, 10 minutes, then DI rinse, then
SC2: NH4OH:H2O2:H2O 1:1:5, 80C, 10 minutes, then DI rinse and spin-dry

After the chemical clean it is important to keep the pairs clean for
successful direct bond. With our CL200 Bonder it is no problem to keep the
pairs clean and bond them at room temperature without any voids. The bond
front is initiated at one point, this is an important point for you. After
performing the bond the interface of the stack can be inspected with
IR-light. If you see any voids you can separate the wafers, clean and bond
them again. The bond energy is weak at this moment. Keep in mind that the
bonding energy after room temperature bonding is based on van der Waal
forces. For completion the bond a high temperature annealing at 1100C (1
hour) is necessary.

Our company Suss MicroTec offers in addition to the Cl200 a Plasma
activation module. The plasma treatment allows to reduce the annealing
temperature significantly down to 200C (8hour) for full bond energy. We have
extensive knowledge of plasma activation. For more information please do not
hesitate to contact me.

Best Regards,
Volkan Cetin