....interest some of you.
It's from Europhotonics, LASER 99 Issue, June/July 1999.
OPTICAL LITHOGRAPHY GETS SIMPLER
As the semiconductor industry struggles to expand optical lithography's
capabilities and decide on the next-generation tool, one research group
has come up with an alternative. A team at the IBM Zurich Research
Laboratory has developed a relatively simple optical technique that
prints features measuring less than half the wavelength of the light
source. And it does so without using complex and expensive focusing
The technique uses a "light stamp" that is placed directly on the
wafer. Unlike traditional contact lithography, which uses
chrome-on-glass masks, the new method uses a rubbery mask that makes
uniform contact with the wafer.
Protrusions on the stamp form the pattern to be printed. When the light
hits the stamp, it shifts to a shorter wavelength and is guided into the
substrate by the protrusions and blocked or reflected in the recessed
areas. The light is focused in the protrusions, and the close contact
between the stamp and the resist - whose refractive indices match -
The group has printed linewidths as narrow as 100nm with a 248nm light
source, and expects to be able to take that further. It has not
experimented with 193 or 157nm lasers, partly because the stamp material
it is using absorbs too much at those wavelengths, according to Bruno
Michel, one of the researchers on the project. But it may not even be
necessary to use shorter-wavelength light sources, he pointed out.
IBM does not yet have plans to use the light stamp method in
high-volume chip production, but might first use the technique for nihe
applications, Michel said.
Allan E W Rennie Research Engineer Centre for Rapid Design and Manufacture Buckinghamshire Chilterns University College Queen Alexandra Road High Wycombe, Bucks HP11 2JZ, UK
Tel: +44 (0)1494 605085 Fax: +44 (0)1494 538593 Email: Allan.Rennie@buckscol.ac.uk http://www.buckscol.ac.uk/tech/crdm/crdm.html
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