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approach to nanotechnology, where
bulk materials are further processed
to create nanoscale entities. In this
approach, all the nanoscale objects
are contained within packages,
and nanomaterials are only used
or released during certain steps
of the processing. There is no
concern for consumer exposure.
But the fab worker can be exposed
to nanomaterials during e.g. the
maintenance of his equipment, or
nanomaterials can be released into
the environment."
Identifying
the hotspots of
risk
The project builds on the earlier
activities of a working group that
was part of the ESIA community,
the
European
Semiconductor
Industry Association. This working
group consisted of representatives
from imec, STMicroelectronics,
CEA, Fraunhofer and Intel. Its
focus was on establishing best
practices for CMP processing. CMP or
chemical mechanical polishing uses
nanoparticle abrasives for polishing,
leading to waste slurries that can
enter the environment. The use of
properties of most of the engineered
nanomaterials are largely unknown to
the sector, most of the semiconductor
fabs adopt the precautionary
principle. Dimiter Prodanov: "As long
as we don't completely understand
what is going on, we apply the
precautionary
principle
when
handling these materials: we assume
that an unknown material has certain
hazardous properties, and we take
all the necessary precautions for
handling this material safely. Later on,
when there will be more experience
and more scientific information on
the material's properties, we can
lower the precautions or make them
more focused."
The properties of nanomaterials
cannot simply be derived from their
bulk counterparts. Dimiter Prodanov:
"Materials at the nanoscale behave
different from bulk materials due
to quantum physics phenomena.
Nanoparticles have a very large
surface area compared to bulk
material with an identical mass.
And this increases significantly their
catalytic activities. Also, the charge
and surface energy distributions can
be different. And this may change
their chemical reactivity and lead to
toxicological properties. For example,
some materials can catalyze the
formation of reactive oxygen species,
which are pro-inflammatory in the
body."
Risk-banding tools
The precautionary principle is
implemented by the use of so-called
risk-banding tools, an approach that
is also being followed at imec. Dimiter
Prodanov: "At imec, the approach
Fig 1: Nanoparticles in solution
nanomaterials in CMP slurries is
now well documented, but there are
other scenarios where nanomaterials
may be used or generated. Dimiter
Prodanov: "For example, different
types of carbon-containing materials,
such as graphene and carbon-
nanotubes, start to enter the fab.
There is growing evidence that
unbounded carbon nanotubes -in the
form of nanoparticles ¬are health
hazards. Experimental studies have
pointed out that carbon nanotubes,
when inhaled, can lead to sustained
inflammation. In a semiconductor fab
where nanoparticles are handled in
containment, exposure to unbounded
carbon nanotubes is not very likely.
But there are situations where some
exposure in not
unthinkable, such as the opening
of a deposition reactor during
maintenance. Part of the project's
mission will therefore be to map the
trajectoryof thevariousnanomaterials
within a typical European facility and
identify the hotspots of risk, where
worker exposure is possible."
Precautionary principle
As the eco-and human toxicological
28 l New-Tech Magazine Europe