Water method shrinks chips

Researchers are refining a method to produce smaller chips. The key ingredient is water.

Researchers are refining a method to produce smaller chips. The key ingredient is water.

By running a small stream of water across a silicon wafer as the circuit lines are etched into the chip, lithography tools can produce circuits down to the 45 nanometer level because of the refractive properties of water, said Bruce Smith, professor of microelectronics engineering and associate dean for graduate studies at New York's Rochester Institute of Technology.

Water turned out to be an ideal liquid because it does not produce a reaction with many commonly used semiconductor manufacturing materials and liquids, and because its refractive properties peak at the same wavelengths used by etching tools in the manufacturing process, Smith said.

Most semiconductor researchers had thought that tools with smaller wavelengths were necessary to produce chips for the 65-nanometer process generation and below. Each time the industry moves to a new lithography tool, it must go through an expensive and time-consuming process to ensure that the new tools will work with existing materials and to iron out any problems that arise.

Chip makers will need to invest in new tools that can deliver the water in a steady stream and purification systems to ensure the water does not contaminate the silicon wafer, said Peter Silverman, an Intel fellow and director of lithography capital equipment. However, they will still be able to use the same generation of lasers and optical equipment.

Several challenges remain, such as the necessity to eliminate defects in the manufacturing process, said Michael Lercel, manager of the advanced imaging department at IBM. At this point, there is too little data about immersion lithography to know exactly what needs to be done to take this technique out of the lab and into manufacturing plants, he added.

Intel and IBM are waiting for immersion lithography research tools due out by the end of this year from suppliers such as Nikon Precision, Canon and ASML Lithography Holding.

The companies will experiment with immersion lithography during the first part of 2005, and decide if and how it will fit into their future manufacturing plans.

Tom Krazit writes for IDG News Service

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