by M. David Levenson, Editor-In-Chief, Microlithography World
A quick roundup of news and views ahead of SEMICON West finds ASML tipping a KrF version of its Twinscan and announcing a first customer for its “ultimate” XT:1900i immersion tool; Cymer’s “socialized medicine” for laser light sources; and Synopsys weaving its tools together to drive next-generation yields.
ASML updates KrF Twinscan line
ASML has announced its long-awaited Twinscan XT:1000 KrF scanner, a high productivity exposure tool for less-than-totally critical layers in circuit manufacturing. Employing a NA=0.93 lens, the nominal resolution of the XT:1000 is 80nm, well below the limit of previous KrF exposure systems. By employing a less costly laser and more robust 248nm wavelength resists, the XT:1000 can lower costs by 1/3 compared to an ArF tool especially for implant and other layers requiring aggressive processing, reported Peter Jenkins, VP of marketing at ASML, in an interview with WaferNEWS.
The XT:1000 sports 300mm wafer throughput of 165 wafers/hr, 10% better than ASML’s previous top KrF tool. With a machine-to-itself overlay of 6nm and 10nm matched tool overlay, the XT:1000 is capable of replacing an ArF scanner for patterning at least six layers of 32nm generation chips. The cost of the new tool would be returned in12 months of production due to lower operating expenses, predicted Jenkins.
Even though the industry has moved on to ArF and ArF immersion, KrF exposure tools continue to take up one-third of the lithography market and print a third of all chip layers. At 80nm CD, the high-NA KrF tool would have a shorter depth-of-focus than an ArF tool running at 193nm. However, improvements in 248nm lens design have reduced the focal plane deviation to below 45nm, mitigating this effect, according to Jenkins. The Twinscan’s state-of-the-art mapping and overlay system allows the new tool to achieve high yield and cost efficiency at a dimension that is 1/3 the exposure wavelength, he noted.
With an NA of 1.35, the XT:1900 approaches the limit of water as the immersion fluid is suitable for 40nm NAND flash memory production. Single-machine overlay of <4.6nm had been demonstrated on this tool over a three day period, he reported, proving that previous overlay difficulties had been overcome.
ASML announced the first shipment of its XT:1900i water
immersion exposure tool on July 18, on schedule to a commercial customer,
reported Peter Jenkins, VP of marketing at ASML. With over 45 immersion systems shipped, and more than half of them the second generation XT:1700s being used in production, ASML considers itself the leader in immersion lithography and plans a fast ramp of XT:1900 production, he noted.
Cymer’s OnPulse: Socialized medicine for lasers
The excimer lasers used for leading-edge lithography incorporate parts that wear out at a rate dependent upon how heavily the laser is being used. Avoiding unscheduled downtime has always required scheduled maintenance and the replacement of consumable parts, some of which are quite expensive. Organizing the purchase and scheduling the delivery and installation of such items adds administrative expense. Thus the costs of operating an individual litho cell can spike at inconvenient and unpredictable times — just like medical costs in the US.
The solution for both problems is some form of insurance, and Cymer has stepped up with its OnPulse approach to insure the health and well-being of its laser products. Because Cymer has 3100 DUV systems in the field, the spikes of expense would average out if a substantial number of customers subscribed to OnPulse; the company would then assume the risk, as would an insurance company. Moreover, since Cymer monitors the operation of its lasers remotely and performs the field service, it can anticipate needs, pre-position personnel and supplies, and undertake preventative maintenance procedures, some remotely. OnPulse combines all laser operating costs in a transparent system that is aligned with chipmakers’ business cycles and goals, according to Nigel Farrar, VP of technical marketing at Cymer, in an interview with WaferNEWS before SEMICON West. The fixed OnPulse rate makes the light source operating costs predictable from the business, smoothing out peaks and reducing transaction costs and administrative overhead, he explained.
The upshot is that Cymer is offering what amounts to a single-payer HMO system for laser light sources. It expects to drive down the costs of maintenance year over year, while making operating expenses more predictable. OnPulse represents a paradigm change for the laser industry, and perhaps other segments of semiconductor manufacturing. Let’s hope it works, and that the idea spreads.
Meanwhile, the company also has announced its latest ArF excimer laser — the XLR-600i, based on the proven XLA two-chamber platform, a 90W variant of the XLR-500 regenerative amplifier laser announced last year. That design allows lower power at the master oscillator, extending its life while improving pulse energy stability by operating the amplifier nearer saturation, according to Nigel Farrar, VP of technical marketing at Cymer, in an interview with WaferNEWS before SEMICON West. “The XLR-600i is also a 6kHz system ,so all that has changed is the energy per pulse, which is now 15mJ,” he noted. The XLR series can achieve 1 billion pulse/fill thanks to Cymer’s GLX gas lifetime extension, and an ABD advanced bandwidth stabilization system keeps the E95 bandwidth below 0.35pm. Farrar said Cymer thinks the high-power XLR-600i can assist the industry’s push toward double-patterning technology, “which otherwise might suffer from reduced throughput at 32nm,” he said.
Synopsys drives next-generation yield
In a pre-SEMICON West interview, Dr. Tracy Weed, director of the manufacturing enabling products group at EDA tool maker Synopsys, explained how the company’s many tools worked together to “drive next-generation yield.” The overriding issue, Weed claimed, is understanding variation at CDs of 45nm and below.
Understanding variation at CDs of 45nm and below is critical to driving next-generation yield, and is the key behind getting Synopsys’ EDA tools to work together, according to Tracy Weed, director of the company’s manufacturing enabling products group, in a pre-SEMICON West interview with WaferNEWS.
With TCAD products like PrimeYield/Seismos increasingly integrated with updated CATs mask data prep tools, the Odyssey/TetraMax modules linking fab and test data along with the company’s Yield Ramp services, Synopsys aims to have a wide impact on future production. PrimeYield, for example, is intended to identify and correct litho and CMP hotspots during design, saving 4-6 weeks, according to Weed. Seismos models proximity effects due to the stress needed to speed gate switching, ensuring that geometrically similar gates have the same mobility and switching times independent of neighboring features.
Mask data prep can now be done concurrently with OPC application, allowing “zero” mask prep turnaround time, according to Weed. Improved fracturing eliminates “slivers” on gate levels and reduces the figure count. “There will be a new, more intuitive GUI in 2008,” he predicted. He also observed that Synopsys is the only EDA vendor with extensive experience in manufacturing and design, and expects to continue to improve communication along the value chain. — M.D.L.