ASML Shipping 1900i; Developing High-NA KrF Scanner for Mid-2008 Release
David Lammers, News Editor -- Semiconductor International, 7/18/2007
ASML Holding NV (Veldhoven, Netherlands) made SEMICON West lithography news at both the ArF (193 nm) and KrF (248 nm) wavelengths, with high-numerical aperture (NA) optics and improved throughputs.
The Dutch lithography vendor announced that its hyper-NA 193 nm immersion scanner, the Twinscan XT:1900i, shipped to one customer in early July. The system is capable of 36.3 nm patterning, features a 1.35 NA lens, and throughput of more than 130 wph.
The announcement comes after Nikon Corp. said in late February that it had shipped its flagship immersion scanner, the NSR-S610C, to a memory customer. The Nikon system has a 1.3 NA lens, also aimed at the 45 nm generation memory and logic devices.
ASML announced plans for a dry KrF scanner with a newly designed 0.93 NA lens from optics supplier Carl Zeiss. By taking advantage of the lower-cost resists and light source of KrF systems compared with ArF, the XT:1000 scanner can achieve a 30% cost reduction compared with an ArF tool for patterns such as implant layers, said Frank Bornebroek, senior product manager.
The Twinscan XT:1000 begins shipping in the middle of 2008, capable of 80 nm resolution, a significant improvement over the 100 nm resolution of the company’s previous KrF scanners. Last week, Nikon said it has released for sale a KrF scanner with an NA of 0.82, designed for patterning layers down to 110 nm. The Nikon system achieves 176 wafers per hour throughput and 9 nm overlay accuracy.
The ASML KrF system was designed to complement the company’s immersion ArF scanners, with 6 nm overlays which equal today’s ArF systems. Throughput was increased from 150 300 mm wph to 165 wph.
Bornebroek said at the 45 nm generation and beyond, ArF immersion scanners will be used for the isolation and gate contact layers, among other critical layers. The higher-resolution optics of the XT:1000 will make it possible to use KrF systems for critical implants, with a matched machine overlay of 10 nm. It also may be used for metal layers in DRAM and flash.
The cost of the ArF resists can be 4× higher than KrF resists, and the scanners themselves are more expensive. He estimated the cost per wafer increases to $15.30 with an immersion ArF scanner, compared to an estimated $9.90 with the XT:1000.
“It is much more difficult to make a 0.93 NA KrF lens than a 0.93 ArF lens,” he said. Because of the refractive index of KrF lenses, early attempts at high-NA KrF lenses resulted in overly large optics. By adopting knowledge gained in designing the catadioptic ArF lenses, the Zeiss lens designers were able to hit the higher-NA target while keeping the lens size under control, he said.
Peter Jenkins, an ASML vice president, said the flagship ArF 1900i was able to achieve 4.6 nm overlay over three days of testing. ASML has been able to show &3 nm overlay for double patterning, using advanced process control technology.
Immersion is being adopted quickly, said Ryan Young, senior manager of marketing communications at ASML. “It took 21 months for our customers to expose the first million wafers, and only the last three months to expose the second million.”
In its second-quarter financial statement, released today, ASML said demand for immersion boosted the average selling price for new systems booked in the quarter to a record 16.9 million euros ($23.34M).
Eric Meurice, president and CEO, said 22 new systems were shipped in the quarter.
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