A method to remove the masksand millions of dollars in costsfrom some optical chipmaking processes is under development at a pair of European companies, and while it's not "smoke and mirrors," the idea is, in fact, to do it all with mirrors.
Photolithography uses a mask, or reticle, with the pattern for a computer chip etched into it. Laser light shining through the mask exposes a light-sensitive material on the surface of a silicon wafer, inscribing the lines that make up the transistors on the chip, much like a negative in photography. Each reticle contains the pattern for only part of the semiconductor wafer, and usually several reticles are used for different layers of circuits.
A practical problem arises as chipmakers try to make the inscribed lines smaller and the patterns more complex. A set of 25 to 30 reticles for today's chips, which are based on 130-nm-thick lines, can cost US $500 000. For the next generation of devices, the 90-nm node, a reticle set is expected to cost more than $1 million, and for the 65-nm node, scheduled to be introduced in 2007, some people are projecting a cost of $3 million per set.
Now Micronic Laser Systems AB of Täby, Sweden, and ASML of Veldhoven, the Netherlands, have teamed up to build a lithography system that replaces the reticles with arrays of millions of microscopic mirrors, which would direct the laser light to the wafer according to patterns fed to them by a computer.
Micronic makes laser pattern generators for producing photomasks, and ASML is one of the world's largest manufacturers of lithography equipment, such as steppers. Their system would use several arrays totaling approximately 13 million aluminum alloy mirrors, each perhaps 8 µm on a side. The exact design will depend on how the companies decide to balance various tradeoffslarger mirrors are easier to build but have a shorter field of view, for instance.