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the metal stacks highlighted. Between each metal layer is a dielectric
or low-K type of material that is stacked for device performance
improvements. This device design has >5 microns of metal thickness
in total. The stack up of the layers, along with each mask step in the
wafer fabrication facility, leads to 38 stacked layers of interfaces at
the end of processing.
The red areas in Figure 5 indicate examples of possible inclusions
from dicing or potential damage that is sub-surface during dicing of
the wafer. These sub-surface interaction points can create failures as
they can propagate to create damage across the scribe seal into the
active device circuitry. Blade dicing these 38 layers happens in one or
two passes of the mechanical dicing blade. Complexities arise when
trying to find a blade composition that is adequate to handle all the
individual material layers and still enable a singulated part that will
not generate a defect during operation in the final product.
Figure 6 shows the introduction of increased complexity of the
current 38 layers with a copper BEOL process. Copper is added
t o i m p r o v e d e v i c e
performance capabilities.
The copper is thicker
and much more difficult
for mechanical dicing
operations. Copper tends
to load dicing blades via a
new failure mode.
The blades used for
dicing are constructed of
electroplated nickel alloy
with synthetic diamonds
embedded into the plating
process. With aluminum
back end of line, use of
the blades is designed to
remove aluminum and
during dicing the blades
are self sharpening. In Figure 6: Copper back end heavy metal cutting.
conjunction with heat
generated during dicing, the copper removed tends to bond to the
nickel allowed at elevated temperatures, and then it is solidified in
place during rotational cooling. This reduces blade life, increases
chipping and dicing associated problems.
New dicing machines are incorporated with an inline-type dressing
block that can periodically be used to free blades from loading with
metals. The alloy of copper nickel created during dicing is much more
difficult to address with auto dressing techniques, and leads to risks
and more failures for mechanical dicing.
New blades are dedicated to improve dicing for copper, but
limitations still exist that were not associated with aluminum BEOL
stack up in the past. An evolution is underway to improve blade
technologies for copper cutting, but new limitations and increasing
costs are associated with copper solutions. With wafer interactions,
there are many variables that affect chipping. Figure 7 shows the
major impacts to chipping during mechanical dicing. Best-case wafer
process design requires use of many of these interactions to drive the
appropriate wafer fabrication design standards for long term success
of any wafer design.
From a mechanical dicing standpoint, there are also multitudes
of dicing inputs impacted by the silicon and package design. Dicing
interactions with inclusion of the silicon design aspects called
out in Figure 8 combine to create vast complexity that should be

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