The key to the system is a trademark technology nLine calls direct-to-digital holography (DDH). Developed at Oak Ridge National Laboratory in Tennessee by company founders Paul Jones and Tommy Thomas, the technique delves deep into submicron structures to detect defects with aspect ratios ≥12:1. The tool's ability to explore the submicron nether regions is unique in the patterned wafer inspection market, insists Bob Owen, nLine's president and CEO. He asserts that Fathom's DDH technology represents a revolution in the market segment, and nLine believes it has carved out a comfortable niche in the wafer inspection field against far bigger rivals. The start-up also announced at Semicon Japan that it had signed up a Japanese partner, Canon Sales, to give the company some needed sales oomph.

"DDH is the only known optical technology capable of detecting defects at the bottom of HAR structures, and the only technology capable of achieving the wafer throughput required for volume chip manufacturing," says Bob Bryant, product manager, in an e-mail interview with MICRO.

The introduction comes at a time of other potential good news for yield managers in a down economy. Two equipment powerhouses recently announced major moves in the wafer inspection field. Within a two-week period beginning in late November, Applied Materials made two acquisitions that bolster its presence in the wafer inspection segment. The global equipment leader purchased the assets of Schlumberger's e-beam wafer inspection unit for an undisclosed cash amount, and it also bought Global Knowledge Services. Headquartered in Austin, TX, Global Knowledge specializes in advanced data-mining services for semiconductor manufacturers.

By acquiring Schlumberger, Applied inherits an installed base of the company's Odyssey 300 system. The system uses e-beam voltage contrast to detect both surface and subsurface electrical, particle, and pattern defects, Applied says. Supporting the customer base will fall to the company's process diagnostics and control division.

A month before the Applied acquisitions, KLA-Tencor launched µLoop, the semiconductor industry's first noncontact, in-line tool for monitoring electrical defects. The so-called MicroLoop can lessen the electrical-yield learning cycle time from eight weeks to a few days, KLA-Tencor asserts. The tool uses an e-beam scanning inspection and review, coupled with testing structures and analytical software, to profile a complete wafer and locate electrical defects in minutes, according to the company. KLA is selling MicroLoop's ability to boost chipmakers' profits by reducing time to market, particularly as new technologies such as copper become more prevalent.

The product manager for nLine notes that his company will be competing with both KLA and Applied for device makers' defect-detection dollars. But, says Bob Bryant, "the competition is not so direct. Neither company has an offering capable of meeting the HARI requirements for volume chip manufacturing."

The DDH imaging technique records the intensity and phase of light. Combining two beams of coherent light, the method creates a hologram showing a complex pattern of interference. DDH captures the three-dimensional image digitally with a charge-coupled device camera before separating the hologram into two images. One is a crisp intensity image; the other, a phase image.

The latter enables them to see defects at a resolution that is five times greater than the resolution of technologies based on analyzing the intensity of light reflected or scattered off the surface of a wafer. At height-to-width ratios >3:1, light "intensity-based" tools cannot find killer defects at the bottom of the device structures, the start-up asserts.

The three established inspection technologies—dark-field, bright-field, and e-beam—have maximum usable aspect ratio capabilities of 1:1, 3:1, and 7:1, respectively, according to nLine. Furthermore, E-beam still offers a throughput of no better than 0.2 wafers per hour, nLine claims.

Mike McIntyre, a program manager for AMD's wafer fab group in Austin, points out that the concept dates to 1989. Thomas and Jones, the Oak Ridge researchers who are now nLine's chief marketing officer and CTO, respectively, refined it with the help of funds from the U.S. Department of Commerce's Advanced Technology Program in October 2000.

"It's not that the physics are new," McIntyre notes, "but the physics have been enabled by advances in imaging and the ability to digitize."

McIntyre says that much more processing now "is going toward damascene-style applications, as opposed to subtractive etch applications." On the contamination side, "you see that the slightest aberration at the bottom of that full feature ultimately results in an open or a dielectric gap that kills the part." At the level of just a few angstroms, the semiconductor industry has had to work around the problem by creating redundancies, he adds. "Ten years ago a logic circuit had no redundancies. Now, quite often, you will see pairs of contacts or quads of contacts."

McIntyre says the Fathom system "gives us a new set of eyeballs. Ultimately, it's tying those eyes back to causes and effects" that'll make the difference. "We've been able to apply new technology to an old system, and now it works."

In the factory of the future, what McIntyre calls "the traditional monolithic defect-detection tools" will still be represented, "but their role as the be-all and end-all as to how systems are put together, I don't think it's going to happen."

Bryant, the start-up's product manager, says the ATP award helped "to accelerate the development of our second-generation technology by nearly two years. The technology developed under the ATP program will allow us to broaden the application of DDH technology beyond HARI."