Nanofabrication

Citation

Rudall, B.H. (1999), "Nanofabrication", Kybernetes, Vol. 28 No. 2. https://doi.org/10.1108/k.1999.06728baa.003

Nanofabrication

Keywords Automation, Cybernetics, Research and development

Abstract Presents reports and surveys of selected current research and development in systems and cybernetics. They include: Cybernetics studies in Romania; Management cybernetics; Nanofabrication; Global information access; Web publishing revolution?; Innovations in systems and cybernetics.

Nanofabrication

The research file of the UK's Engineering and Physical Sciences Research Council's (EPSRC) Impact (No. 21, 1998) gives details of an innovative method of making ultra-high resolution nanoscale devices using silicon-germanium (SiGe). The method has been discovered by researchers working on an EPSRC project on advanced silicon structures. The project involved the UK's Universities of Cambridge, Liverpool, and Warwick and Imperial College.

The project report says that:

The new device fabrication route takes advantage of damage caused during the electron beam irradiation process that etches patterned circuits into a layer of "photo-resist" material on a semiconductor base.

It was discovered unexpectedly as part of the project's investigation into the ultimate limits of nanofabrication, which seeks to create circuits at extremely small scales. Conventional high-resolution electron beam lithography has usually involved a polymer-based resist like PMMA which hardens when exposed to the beam. One of the aims of the project was to study how silicon dioxide on a SiGe base could be used to provide higher resolution circuits than is possible with PMMA.

The EPSRC's projects' principal investigator, Dr Mark Welland, a researcher at the Department of Engineering at Cambridge University UK says that:

We successfully developed a masking layer of low-temperature plasma oxidised silicon on a SiGe heterostructure. However, we found it was impractical to apply to the fabrication of useful devices.

He added that the degree of damage caused to the SiGe by the high dose levels required for irradiating the silicon dioxide was the main barrier to creating practical devices. It was realised later that the team could exploit the damage effect to eliminate some process steps when patterning nanoscale structures within SiGe. The project also demonstrated how this direct damage technique could be used effectively to pattern nanoscale structures with conventional resists.

The report says that:

It quantified the ultimate resolution limits of PMMA to a new precision through the most comprehensive study of its kind to date. No clear evidence was found on how to improve the ultimate resolution, but many valuable data were gathered on potential approaches, like ultrasonic agitation.

The project showed how it could benefit from close collaboration at Cambridge between the Engineering Department and Professor Mike Pepper and Dr Douglas Paul at the Cavendish Laboratory.

Important contributions were also made by Warwick University's Physics Department, which has pioneered work on SiGe, and the Engineering Department at Liverpool University, a world leading centre on plasma oxidisation growth. Imperial College assisted by providing additional supplies of SiGe material.

The three-year project ended recently. Dr Welland led its latter stages, after its original manager, Professor Alec Broers, became Vice-Chancellor of Cambridge University. The results of the project are being built on at Cambridge in the Esprit SIQUIC and NANOWIRES projects and EPSRC-funded research into applying irradiation damage technology to manufacture superconducting devices and to fabricate SiGe-based quantum devices.

Readers may wish to know the Web link for the Nanoscale Science Group at Cambridge, UK is: www2.eng.cam.ac.uk/~nano-www/