INDUSTRY NEWS

Lam takes CMP plunge with dry-in/out tool

Lam Research has plunged into the growing global CMP market with a wafer polisher that the vendor claims is three times more efficient at planarization than conventional systems. Called Teres, the dry-in/dry-out system owes its greater efficiency to a proprietary method called Linear Planarization Technology (LPT) that addresses current pattern density effects as well as dishing and erosion problems, Lam says. Solving these problems will help chipmakers in CMP applications such as shallow trench isolation and copper damascene.

The vendor claims two key yield-related benefits. The Teres tool minimizes defect density by preventing slurry residues from drying on wafer surfaces. It also eliminates the potential for contamination caused by transferring wet wafers to a separate postprocess cleaning system.

The tool's design solves the "logistics problem" common to the wet CMP process, says Rahul Jairath, Lam's director of CMP technology. "It becomes a logistics problem after you complete a certain step such as polishing when the wafers have to be moved rapidly in a wet environment from the output station of the polisher to the [next] input station, a scrubber, for example. . . . There's been a major drive here to integrate the two functions."

Lam has spent "the past three to four years" in technology development and approximately 11Ž2 years developing the cluster tool "to make sure the wafers move from the polishing station into the scrubber as soon as possible." Teres incorporates two polishing stations and an integrated cleaner that uses scrubbers from OnTrak Systems, which was recently acquired by Lam. The overall system integrates etch, CVD, and CMP steps for submicron trench and copper damascene structures. According to Jairath, these capabilities require no trade-offs such as low uniformity and high production costs that could result from compensating for pattern and topography sensitivity by using metal fill, for example.

"The biggest hurdle is, of course, copper. There are corrosion and not just cleaning issues involved," Jairath points out. "That's why we think our precleaning step can actually double as a corrosion [prevention] step as well." For short oxide polishing and short tungsten polishing steps, the system can process up to 70 wafers per hour. "The copper integration steps are not defined yet."

Jairath says Lam has been working "very closely with a number of Asian and European customers. What we're finding as the industry is transitioning from 0.25- to 0.18-µm processes is there are a lot of issues showing up in high-volume manufacturing . . . that don't show up in early process development activities such as a pilot line. So as the need to increase yield becomes higher, people are finding that rotary polishers are not up to speed in terms of their ability to handle throughput."

Tony Schraub, director of marketing for CMP tool supplier Strasbaugh, says he is not familiar with the capabilities of the Teres system. "I think they have a well-established post-CMP tool," he said of Lam's OnTrak subsidiary. "That's an advantage for them, but their CMP tool is an unknown."

Strasbaugh has "at least 15%" of the global CMP market, and business continues to be "very good," says Schraub. In mid-March the executive said the vendor was close to signing a contract to purchase scrubbers from OnTrak. "It's a bit strange to be making deals with new competitors. So far, they're behaving quite honorably in that."

Regarding Lam's announcement, he concludes, "I don't want to bad-mouth them and have no basis to. They separated their scrubber work from their cleanroom work. They're a good company, and they're to be respected and watched out for."

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