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Did You Know…

…why ZEISS Is Interested In How Fast Grass Grows?

In the summer, some people have to mow their lawns about every two weeks. This is because grass grows about two centimeters a week. That works out to two micrometers per minute or 30 nanometers per second. So why is ZEISS interested in how fast grass grows? The smallest structural size of a high-performance microchip transistor is currently about 30 nanometers, the rate that grass grows per second. To map such fine patterns onto the microchips, optical lithography – the key technology in chip fabrication – must become increasingly precise. ZEISS is the leading manufacturer of these lithography optics.

Much like a slide projector, lithography optics project the desired structures for the subsequent microchip onto a silicon disk, or wafer. The actual semiconductor structures are then developed in further process steps. To achieve the extremely high resolution needed to produce miniature structures, the lenses or mirrors in optics systems must be made with utmost precision. This manufacturing precision is so extreme that the highest irregularity on a mirror from the most recent lithography generation is barely one nanometer high. In order to create such a smooth surface, the lenses and mirrors undergo several very sophisticated processing steps – from grinding and various polishing processes to coating.

Humans can normally imagine sizes that are four to five magnitudes different than their body size. One hundred micrometers – the thickness of a sheet of paper – or 1,000 kilometers, the stretch of road that we can normally cover in one day with a car… these are things we can easily imagine. But how small is a nanometer? It is simply not something we can truly comprehend. Only comparisons help here: if a mirror from the latest lithography generation were to be enlarged to the size of Germany, the largest deviation – i.e. the peak of the country’s highest mountain – would be less than one millimeter high. Just imagine — if grass grew just by one nanometer per second instead of 30, then it would need to be mowed only once a year!



24 July 2012

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