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IBM promotes making chips in the bath

An experimental version of immersion lithography could help cut the cost of making chips in the future.

IBM Research has come up with a way to draw lines in silicon 29.9 nanometers apart with existing chipmaking machines, far closer than on today's chips, a development that could help cut the cost of making chips in the future.

The breakthrough revolves around an enhanced, experimental version of immersion lithography. In immersion lithography, silicon wafers are immersed in purified water. Laser light shining through an intricate mask throws a microscopic shadow pattern onto the wafer, which then becomes permanent through chemical processes similar to the process in which a negative becomes a photographic print. The more intricate the pattern, the smaller the circuits.

The wafers are immersed in water because water bends light rays better than air, which in turn can lead to sharper resolution and smaller patterns. Immersion lithography will start getting used commercially in the relatively near future.

In IBM's system, light from the laser is split into two beams. Then, a tool called Nemo weaves the two beams to create a light and dark interference pattern that allows for a pattern with more closely etched lines that can be achieved in standard immersion lithography.

The system also swaps out water with a special fluid from JSR Micro, a specialized prism, and a special photoresist system.

"We can routinely do sub-30 nanometer spacing," said Robert Allen, manager of lithography materials at the Almaden Research Center, IBM Research.

If the Nemo system ultimately goes commercial, the process could let the industry wring more life out of 193-nanometer lithography systems installed today. Machines based on these standards--which can cost $15 million each and get delivered in customized tractor trailers--have been around for years. The name derives from the fact that the wavelength of the laser light measures 193 nanometers (a nanometer is a billionth of a meter.)

Replacing them with machines based on new technologies has not been easy. Years ago, IBM was one of the principal backers of X-ray lithography. It worked, but was not economical. In the past decade, Intel--along with Advanced Micro Devices and to a lesser extent IBM--has promoted Extreme Ultra Violet lithography, or EUV.

EUV systems have been delayed for years. Back in 1997, proponents expected EUV equipment to be on the manufacturing line for 65-nanometer chips, which just started coming out.

But the technology is still in the labs. Although Intel may use it to produce 32-nanometer chips, coming out around 2009 or 2010, researchers there say it won't likely hit until the chip generation after that, when processors will have an average feature size of 22 nanometers.

Nemo gives IBM confidence that immersion lithography with 193-nanometer systems could be used for the 32-nanometer chips. Pushing it to 22 nanometers, however, will require better fluids, different photoresist materials, and lenses made up of as-yet-unidentified substances, Allen said.

IBM will show off the results at the Microlithography 2006 conference being held in San Jose, Calif., this week.