New-Tech Europe | March 2016 | Digital edition

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

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

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

Fig 1: Nanoparticles in solution

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