| TECHNOLOGY |
However, in September 1997 IBM surprised the computer industry by announcing that it had decided on the metal, choosing copper as its circuit material of the future. "Suddenly, everybody's program shifted to copper research from dielectric research," McClear says. "Dielectric research was put on hold." Jim Ryan, manager of interconnect technology for IBM Microelectronics in East Fishkill, N.Y., says his company chose the metal before the dielectric precisely because it was the easier decision. "Our strategy is to make one change, then incorporate it commercially," Ryan says. In 1998, IBM launched production of semiconductors with 0.22-m copper wiring using a conventional dielectric. However, once IBM and other semiconductor manufacturers were able to make copper wiring work, the research focus shifted back to the dielectric. Gradually, the original 150 candidates were whittled down to just a handful. Like it did with copper, IBM came out first with its material of choice for the new dielectric, announcing in April that it had picked Dow's SiLK aromatic hydrocarbon polymer, which has a dielectric constant--what the industry calls k value--of 2.65. Suddenly, Dow, a company with little experience in the semiconductor materials business, was linked up with one of the world's top chip makers. Ryan acknowledges that choosing a new dielectric was difficult. "Silicon dioxide is a marvelous material," he says. "It has all the characteristics you like--no low-k material can do what it can do." But with a dielectric constant of about 4.2, SiO2 wasn't a good enough insulator to prevent cross talk between the closely spaced wires in the smaller generation of electronic devices. The criteria that IBM subjected its dielectric candidates to included thermal stability to 450 C, a dielectric constant of less than 3.0, good adhesion, chemical compatibility with other chip components, etchability, and commercial availability. "We looked through a whole host of dielectrics," Ryan says, "and the one we felt had the best properties was SiLK." IBM will start producing 0.13-m semiconductors that employ copper and SiLK in the first half of 2001 at an existing plant in Burlington, Vt. A new $2.5 billion plant based on copper and SiLK--part of IBM's largest ever capital investment--will then start up in 2003 in East Fishkill. These applications will mark the commercialization of SiLK, but McClear makes it clear that IBM won't be Dow's only customer. "There are about 15 semiconductor companies worldwide with active low-k programs, and we are working with all of them," he says |
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