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of different solutions that enable high-vacuum performance,
long-term stability and device reliability. The getter films are a
common and technically-accepted way to maintain and control
vacuum in hermetically-sealed MEMS used in a large number
of applications, such as defense and security, automotive,
industrial and consumer. The getter features and applications
are as follows:

Getter features: 1) High vacuum; 2) Long-term stability; 3)
High sorption capacity for all active gases; 4) Activation
temperature compatible with all main packaging procedures;
5) Different patterning methods; and 6) Particle free.

Getter applications: 1) Uncooled IR sensors; 2) Gyros; 3)
Resonators; 4) Time frequency devices; and 5) High-end
pressure sensors.

To prevent premature activation, the getter should not be heated
above 250°C and the device fabrication exploited the large gap
between the two platens in the bonder process chamber to enable
thorough outgassing before the in situ alignment step (required to
align the patterns on the two wafers to be bonded) and subsequent
contacting and hermetic sealing of the two wafers. The getter was
then activated during the 260ºC wafer bonding step.

Discussion
Neither of the above examples of wafer-level encapsulation could
have been achieved without the use of an aligner wafer bonder
capable of in situ alignment. The in situ aligner bonder is best
described with reference to Figure 3, which shows a schematic of
the process chamber.

Figure 3: Schematic of the process chamber of the aligner wafer bonder.
A key feature of the in situ aligner wafer bonding system is the
large gap between the platens. This difference between the aligner
wafer bonder and conventional wafer bonding tools is key for
wafer-level encapsulation applications.
Figures 4-7 demonstrate the essential differences between
conventional wafer bonding equipment and the design of the AML
aligner wafer bonder with regard to the following: 1) Capability
for in situ chemistry; 2) Capability for differential platen
temperature; 3) Simultaneous heating, alignment and fast vacuum
pumping; and 4) Outgassing of the process wafers and accurate
measurement of chamber pressure.

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