Page 47 - ChipScale_Jan-Feb_2020-digital

Figure 4: Comparison of aligner wafer bonders and conventional wafer bonders for Figure 5: Comparison of aligner wafer bonders and conventional wafer bonders for
performing in situ chemistry [4,5]. maintaining a temperature differential between the two platens.

Figure 6: Comparison of aligner wafer bonders and conventional wafer bonders for Figure 7: Comparison of aligner wafer bonders and conventional wafer bonders
heating, alignment and vacuum pumping. for outgassing.
AML bonders have been extensively used for many years for
vacuum encapsulation applications for which their in situ align and
bond design is ideally suited. However, the systems have previously
been limited to vacuum levels of 10 mbar, which has excluded their
-6
use in some application areas. To address this, the latest system
design allows integration of an optional cryopump and enables
ultra-high vacuum (UHV) levels to be achieved. One important,
high-growth area that requires UHV conditions is quantum
-8
computing for which vacuum levels in the low 10 mbar range are
required. Other applications that benefit from the UHV capability
are surface-activated bonding and thermal imaging, especially
when using vacuum encapsulation wafer-level packaging. Figure 8
shows the vacuum performance of the new UHV bonder.
The purge step was included in the pump-down procedure
because this spreads the heat from the internal bake-out heater
more effectively around the chamber to promote more outgassing,
resulting in a slightly faster pump-down time. For pressure control,
the UHV bonder also includes a turbomolecular pump, and this
makes the bonder compatible with the AML radical activation/
Figure 8: Pump down performance. surface etch tool for which pressures of 1mbar are required.

45
Chip Scale Review January • February • 2020 [ChipScaleReview.com] 45