Nano Group, University of Southampton

Nano Group

New age of exploration touches the limit of the nano world

The extraordinary technology in the new Southampton Nanofabrication Centre is demonstrated in this image of tungsten atoms - the group of three atoms in the centre of the image is close to being 100,000 times smaller than a human hair.

The image was obtained this week during the commissioning in the new Mountbatten Building cleanroom of the ORION™helium-ion microscope. The ORION™ is the only one of its kind in the UK. Developed and provided by Carl Zeiss SMT, ORION™is pushing scanning beam technologies beyond current limits – in November 2008 it achieved a record 0.24nm resolution, close to the diameter of a single atom.

Professor Harvey Rutt, Head of the School of Electronics and Computer Science at the University of Southampton, was instrumental in bringing this new technology to the Mountbatten Building. He says: 'What can be seen here is an an array of tungsten atoms. Each "fuzzy dot" is a single atom – in the centre of the image is the tip of a needle so sharp it has just three atoms on its tip, surrounded by a slightly irregular hexagon of six, with three arrays of six more further out on the sides of the needle.

'This illustrates graphically how tiny our world can be,' he says. 'The conditions needed to make these images need to be stable, vibration-free and clean. A speck of dust is tens of thousands of times bigger than what can be seen here. Vibration utterly imperceptible to a person would destroy the image, like a blurred image from a shaking camera, but millions of times more sensitive. This is, in one sense, the ultimate limit of the nano world – you can’t go smaller than an atom.'

According to Carl Zeiss SMT, this new microscope is capable of providing images of unrivalled high resolution, surface information and material contrast, unachievable with any other microscopy instrument available today and paving the way for a new era in sub-nanometer, ultra-high resolution scanning microscopy.

The ORION™ scanning ion microscope uses a beam of Helium ions — rather than electrons typically used in scanning electron microscopes (SEM) — to image and measure. Since Helium ions can be focused into a substantially smaller probe size and provide a much smaller sample interaction compared to electrons, the ORION™ system can generate higher resolution images with greatly improved material contrast at a substantially extended depth of focus.

The ongoing shrinkage of feature sizes of semiconductor devices makes extreme high resolution microscopy mandatory. 'Some layers of integrated circuits already have reached a thickness of only a few atoms,' Dr Rainer Knippelmeyer, Senior Vice President Operations of Carl Zeiss SMT explained last November. 'Semiconductor manufacturers are in dire need of reliable high-resolution, surface sensitive metrology and process control tools. With the ORION™ helium-ion microscope we offer exactly the tool the industry and nanotechnology research needs and we continue to keep pace with the industry’s rapidly changing requirements.’

The secret behind the extreme high resolution of the helium-ion microscope lies in the proprietary source technology and in the interaction between the scanning ion beam and the surface of the specimen. The source of the microscope is very small and the helium ions emanate from a region as small as a single atom. Unlike electrons, the helium ions have a very small wavelength and hence do not suffer appreciably from adverse diffraction effects – a law of physics which fundamentally limits the imaging resolution of electrons. Also, the helium ion beam triggers signals directly from the surface of the sample and stays very collimated upon entering the sample. This results in very sharp and surface sensitive images at the quoted resolution which can be easily interpreted. In contrast, for a typical SEM, the majority of the secondary electrons that are used for imaging come from deeper and much less confined regions within the sample, creating blurrier images with less resolution than the ORION helium-ion microscope.

For further information contact Joyce Lewis, tel.023 8059 5453

Posted by Joyce K Lewis on 03 Apr 2009.