<s>
Direct	B-Algorithm
bonding	I-Algorithm
,	O
or	O
fusion	O
bonding	O
,	O
describes	O
a	O
wafer	B-Algorithm
bonding	I-Algorithm
process	O
without	O
any	O
additional	O
intermediate	O
layers	O
.	O
</s>
<s>
Even	O
though	O
direct	B-Algorithm
bonding	I-Algorithm
as	O
a	O
wafer	B-Algorithm
bonding	I-Algorithm
technique	O
is	O
able	O
to	O
process	O
nearly	O
all	O
materials	O
,	O
silicon	O
is	O
the	O
most	O
established	O
material	O
up	O
to	O
now	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
bonding	O
process	O
is	O
also	O
referred	O
to	O
as	O
silicon	O
direct	B-Algorithm
bonding	I-Algorithm
or	O
silicon	O
fusion	O
bonding	O
.	O
</s>
<s>
The	O
fields	O
of	O
application	O
for	O
silicon	O
direct	B-Algorithm
bonding	I-Algorithm
are	O
,	O
e.g.	O
</s>
<s>
The	O
silicon	O
direct	B-Algorithm
bonding	I-Algorithm
is	O
based	O
on	O
intermolecular	O
interactions	O
including	O
van	O
der	O
Waals	O
forces	O
,	O
hydrogen	O
bonds	O
and	O
strong	O
covalent	O
bonds	O
.	O
</s>
<s>
The	O
initial	O
procedure	O
of	O
direct	B-Algorithm
bonding	I-Algorithm
was	O
characterized	O
by	O
a	O
high	O
process	O
temperature	O
.	O
</s>
<s>
First	O
reports	O
of	O
successful	O
silicon	O
direct	B-Algorithm
bonding	I-Algorithm
were	O
published	O
1986	O
among	O
others	O
by	O
J	O
.	O
</s>
<s>
Direct	B-Algorithm
bonding	I-Algorithm
is	O
mostly	O
referred	O
to	O
as	O
bonding	O
with	O
silicon	O
.	O
</s>
<s>
Even	O
though	O
direct	B-Algorithm
bonding	I-Algorithm
is	O
highly	O
flexible	O
in	O
processing	O
numerous	O
materials	O
,	O
the	O
mismatch	O
of	O
CTE	O
(	O
coefficient	O
of	O
thermal	O
expansion	O
)	O
using	O
different	O
materials	O
is	O
a	O
substantial	O
restriction	O
for	O
wafer	O
level	O
bonding	O
,	O
especially	O
the	O
high	O
annealing	O
temperatures	O
of	O
direct	B-Algorithm
bonding	I-Algorithm
.	O
</s>
