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Applied takes wraps off its first wafer defect detection tools

Applied Materials has introduced its first defect detection systems since the vendor entered the metrology and wafer inspection market in early 1997. The global leader in fab process gear unveiled the WF-736 DUO and WF-731 systems, tools that the manufacturer says will give fabs detection and analysis capability "from process development through mature manufacturing."

DEBUT: The WF-736 DUO is one of two wafer defect detection tools recently introduced by Applied. Designed for engineering analysis, the system combines darkfield and brightfield technology.

The tools share the same architecture and can work in tandem, says Applied. The WF-736 DUO tool enables engineering analysis applications, and the WF-731 focuses on fab-floor production monitoring. The systems will be installed in product development labs for customers to perform defect characterization on Applied's front-end equipment, supporting the company's Total Solutions marketing approach.

The DUO's benefits include a combination of four-channel Perspective Darkfield Imaging (PDI) and a brightfield capability called Integrated Normal Perspective (INP) for detecting light scattered from particles and pattern defects. To enhance sensitivity to surface and subsurface defects, the brightfield image is analyzed in parallel with the four darkfield images, Applied says. Positioned above the wafer, the brightfield channel captures defect "signatures" that result from "the vertical illumination of the wafer surface" and compares this signal with the other channels.

Incorporating the same brightfield technology, the 731 system is capable of analyzing 34 wafers per hour as a production monitoring tool. In addition to sharing the PDI technology, both systems are based on Applied's WF-73X platform, share hardware and software, and feature the same process recipes to enable the comparison and transfer of inspection data. This design gives users the ability to develop one standard inspection system in the fab, Applied asserts.

The introduction comes approximately one year after the equipment manufacturer purchased Orbot Instruments, a manufacturer of automated optical inspection systems, and Opal, a supplier of CD-SEM systems. Both are based in Israel. Applied has received approximately $20 million in advance orders for the systems from semiconductor manufacturers in the United States, Europe, and Taiwan.

David Jensen, the manager of the defect reduction technical program at Sematech, has run demonstration tests on the machines. "The great advantage is the user-friendliness of it all. I am not a physicist or a long-time operator of every tool in the industry and in less than a few hours was able to understand what the recipe was about . . . to make the [necessary] adjustments. It's very simple to learn; the recipe setup is made much easier because of the diverse detection algorithms."

Understandably, KLA-Tencor has a different viewpoint. The company is the market leader, with more than 80% of the world's defect detection segment sewn up. "This is an attempt by Orbot to recycle existing technology and does not represent anything new," asserts David Icke, vice president of marketing for KLA-Tencor's wafer inspection group. "When customers require a single-platform solution for engineering analysis and line monitoring, they have that capability with the KLA-Tencor 2100 series brightfield inspection technology and its modular configurations. The difference is that the 2100 series offers high-resolution brightfield capability. . . with far greater sensitivity and defect capture than is possible with the Orbot technology using monochromatic illumination." Icke adds, "A monochromatic point sensor is just going to be a noise detector."

KLA-Tencor's 2100 series is designed for use in etch and photolithography analysis. Its Surfscan AIT system is a film and pattern tool. The vendor has introduced a laser imaging pattern wafer inspection system called the ILM-2230, which the company says is the first to combine oblique angle darkfield illumination with KLA-Tencor's small-pixel, high-data-range image processing for defect detection on 0.25-µm and lower devices. The tool is a result of "leveraging" digital image processing and laser illumination technologies that were combined after the merger of KLA and Tencor in spring 1997. The vendor says the tool is targeting inspection applications in advanced interconnect processes such as CMP.

Applied's tools can also be used for yield analysis and production monitoring in CMP applications. The systems can be used to classify up to nine defect categories. Bob Johnson, the product marketing manager for the equipment manufacturer's process diagnostics and control group, notes that the tools' automatic defect classification ability means the systems do not have to rescan a wafer in order to group the defects. The detectors used in conjunction with the laser scattering have different signals depending on the detector, and, "by looking at this unique signature. . . we can usually give you a first order of classification of the defects as we find them."

Johnson adds that user-defined rules enable operators to set their own processes based on the images picked up by the five detectors running in parallel. "Is [the defect] scattering light like a particle, like a microscratch, like a big boulder would scatter light, like a pattern defect would scatter light? The advantage we have is that there's no impact on throughput. You don't have to go back to take a picture of the defect and analyze a picture," says Johnson. "The data is available as part of the whole detection algorithm."

The 731 is optimized for higher-speed line-monitoring applications and as such has a lower level of detection sensibility than the 736 system. The 731 does not have the fifth, or brightfield, channel, "meaning that the kind of detailed work [needed] for engineering analysis is not there." But, Johnson explains, the operator can say, "Gee, I've got data off my line-monitoring tool that I really want to go to my high-sensitivity engineering analysis tool. It's a simple thing to do."

The concept, concludes Johnson, "is we have this common technology that goes all the way from high-throughput line monitoring up to high engineering analysis uses." Priced at approximately $1.5 million, the 731 can be upgraded to the 736, says Johnson. "You can develop recipes running on the 736 that will run on the 731." The 736 costs "in the $2-million range."

Price as a buying factor is not really on the radar screen, Johnson points out, stressing that most customers are "making initial evaluations based on performance." Says Sematech's Jensen on the issue of tool costs: "If you're price sensitive this is a very good thing, although I haven't priced it in about six months. Their tool is less expensive than comparable technology. However, if you're not in a price-sensitive environment, it doesn't matter. You buy the tools that detect the defects."

Icke says KLA-Tencor's defect detection tools "are head and shoulders above the rest in terms of implementation." He adds that the 2100 series system "is the highest performing brightfield tool, and it has the capability if you want to take advantage of it." As for the AIT system, Icke says it is "faster and more sensitive than the two Orbot tools." The marketing executive believes the Applied name will open some doors. "If you sell a $100-million to $150-million order you can say [to customers], 'Have a look at this piece of equipment.' However, they aren't going to find the technical need that's unsatisfied at KLA-Tencor."

Insists Icke: "One size is not going to fit all."

One vendor pleased with the Applied introduction is Knights Technology, a supplier of yield-management software. Arkush Oberai, vice president of worldwide sales for Knights, says he expects to see an increase in sales of his company's software. "It surely gives us another avenue for selling our products," says Oberai, adding, "In general I think the market now can have multiple sources of defect detection machines." The executive notes that KLA-Tencor offers proprietary software for use on its tools.

"It seems from the customers I've talked to, they expect Applied's defect detection systems are going to hopefully meet or exceed what they have in the market today. So there is a little bit of excitement." Oberai believes customers will buy systems from both vendors.

A diplomatic Jensen concurs. "More than anything, we're finding that different types of defects are preferentially detected by different detection techniques," he says. "Anything the tool suppliers can offer that . . . is different from another tool . . . such as the incident angle of the light, the spot size, the number of detectors, and the angle of those detectors—both longitudinally and latitudinally to the pattern—there is probably a niche for it, because there'll be a defect or a set of films or layers that the tool is more capable of detecting defects on."

Sue Billat, an equipment industry analyst with Robertson Stephens, applauds Applied's strategy. "In my view it was both a wise and strategic decision by Applied to go into the inspection and metrology businesses, and I would say the fact that they are continuing to develop and upgrade these products indicates their corporate strategy of working to dominate the markets they serve. I think we can expect to see a broader use of inspection in the near term as stand-alone tools and ultimately as tools that are integrated into their large-platform systems."

Billat adds that Applied told the investment community it "would be investing heavily in this area. I think they're looking beyond just simply addressing a new market, which would be a tactical move, to a strategic side, which is, how do you bring the inspection tools closer to the process tools? That to me is the real significance of Applied entering this market."

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