Crystalline surfaces, self assembled structures, and nano-origami as length standards in (nano)metrology

The global market for advanced electronics currently valued at around €235 bn, with semiconductors being key manufacturing materials. The EU has a goal of supplying 20 % of all silicon wafer production by 2025. The ability to make accurate nanoscale measurements during the manufacturing process is an important factor for reliable production. Instrumentation, such as Atomic Force Microscopy is used to assess production quality, but currently few nanometre dimensional standards exist to confirm performance. The natural shapes of crystals, polymer chains or DNA folded into pre-determined shapes all have great potential to self-organise into repeatable and reproducible structures for use as nanoscale rulers. Before these can be routinely used, further investigations are required to confirm their suitability for characterising advanced measurement techniques.

This project developed novel dimensional reference standards, based on self-organising crystalline and molecular structures, for the calibration of the instruments that are used to measure the dimensions of advanced nanoscale electronic components.

The project:

• Developed prototype nano-dimensional standards based on silicon crystals, which form regular lateral and step height features, for use in the calibration of scanning microscopes
• Developed prototype nanoscale standards based on the self-assembly of polymer structures to produce repeatable lateral grids - patent application
• Developed so-called “find-me” structures to aid users in identifying the locations of features on reference standards
• Demonstrated the feasibility of using “nano-origami” to manipulate DNA to produce repeatable structures that are suitable for future use as dimensional standards.

This project investigated self-organised, repeatable structures formed from silicon crystal lattices, polymer chains or DNA sequences for use as nano-dimensional standards, with patent applications already registered to protect IP. Although 20 times smaller than previously available reference materials, these prototypes have 10 times better accuracy. The Comité International des Poids et Mésures (CIPM) is considering the adoption of these new reference materials to calibrate instrumentation for measurements at the nanoscale. Further comparison studies between National Measurement Institutes are needed to demonstrate to the BIPM the reliability of procedures for their production and characterisation. Then the introduction of international standards and best practice guidance to increase measurement uniformity and accuracy at the nanoscale are required before these reference length standards based on the fundamental properties of nature, can be introduced to help maintain European competitiveness in advanced electronics manufacturing.