Immersion lithography is fast approaching its launch on the manufacturing floor and will probably come on board with a number of large semiconductor manufacturing companies this year. That's the word from Dr. Michael Lercel, director of lithography at SEMATECH. As he sees it, manufacturers who are spearheading both tighter densities and higher performance will be making the switch from dry-film techniques because immersion lithography in high-volume manufacturing holds the promise of better imaging resolution, which is essential for tighter geometries. These views were also echoed by others who attended the SPIE Advanced Lithography Symposium in San Jose, Calif. two weeks ago.

Immersion lithography interposes a liquid between an exposure tool's projection lens and the wafer. The liquid enhances the resolution, enabling the system to produce smaller features. It will gradually become the successor to 'dry lithography,' so-called because there is an air gap between the lens and the wafer. Filling that gap with a liquid, such as water, brings about a higher index of refraction and no total reflection at high incident angles. The switch to a liquid means higher resolving power and enables using a bigger lens, which means more imaging power, and in turn, narrower line widths.

However, to get to 32 nm geometries, a fluid other than water is undergoing trials. These are typically organic-based and have indices of refraction, which makes simultaneously meeting low absorption difficult to achieve. Also, new materials for making lenses that also increase refractive index and so enable greater magnificiation, are being sought. One such material, lutetium aluminum garnet (LuAG), shows considerable promise. 

Summing up the advances in immersion technology, Lercel sees it this way: "What these efforts offer to the overall chip industry is a potential for scaling, using technologies that are not dramatically different from what is in use today. If these advancing immersion lithography techniques prove successful they will provide a maufacturable solution that semiconductor companies will be able to adopt quite easily. Using these changes they will be able to ramp up to the next technology, which is to say implementing higher density higher performance in a fairly short period of time."

The consortium, called SEMATECH (SEmiconductor MAnufacturing TECHnology), was formed in 1987, when 14 U.S.-based semiconductor manufacturers and the U.S. government came together to solve common manufacturing problems by leveraging resources and sharing risks.

SEMATECH officially began operations in 1988, focused on improving the industry infrastructure, particularly by working with domestic equipment suppliers to improve their capabilities. Since its inception, SEMATECH has set global direction, enabled flexible collaboration and bridged strategic R&D to manufacturing. It continues to accelerate the next-technology revolution with nanoelectronics and emerging technology partnerships.

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