The reliable measurement of small structures, less than one micrometre in size, is necessary to enable the ongoing miniaturisation of components in optical and semiconductor products. Scatterometry is a tool that measures surface structures at the nano level by scattering light across a surface and detecting the reflections. It is relatively fast compared with traditional techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM), and could be more widely used during the manufacture of nanoelectronic and other miniature devices once its performance can be robustly validated via traceability to accurate standards.
This project established traceable and absolute scatterometric measurements and transfer standards for the characterisation and calibration of scatterometers. As part of the project:
- Three relevant methods for dimensional and critical dimension (CD) metrology in the semiconductor industry were improved: CD-SEM, CD-AFM and scatterometry. The project improved the comparability of these methods and developed data analysis schemes that enabled an additional reduction of measurement uncertainty.
- Fast and reliable optical metrology methods were developed and tested with scatterometry and Mueller polarimetry – these are available for the characterisation of diffractive and hybrid optical devices in the optics industry.
- Scatterometry reference standards have been designed, developed, characterised and calibrated to face the challenging requirements of the semiconductor industry as specified in the International Technology Roadmap for Semiconductors. For the first time, standards are available which are suitable for the test and calibration of scatterometers, AFMs and SEMs. This will facilitate the comparability of measurement results obtained using these different types of tools.
The project worked closely with European and international instrumentation suppliers and semiconductor manufacturers throughout, sharing results and developments. A number of companies are interested in the reference standards, measurement services and software developed. Sector organisations such as the international SEMI Microlithography Committee were also closely involved. The project team is continuing to work with one of these organisations to evaluate EUV (extreme ultraviolet) photomasks that will support the next generation of semiconductor manufacturing.
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