INDUSTRY NEWS

SPIE Microlithography 2001

Overlay, SEM, and CD control topics find favor at symposium's metrology and inspection conference

An array of technical presentations on pattern overlay and SEM technology will share the spotlight in the metrology conference portion of SPIE's microlithography symposium this month. Additional metrology highlights include a session devoted to new technologies and one exploring the microeconomics of 300-mm manufacturing. A panel discussion on the topic will follow, which is a first. Hosted by SPIE, the 26th Annual International Symposium on Microlithography will be held February 25–March 2 in Santa Clara, CA.

"One trend this year seems to be the good number of overlay papers. Year to year, it's a toss-up between CD-SEM and overlay...as the leading candidates," says Neal Sullivan, chairman of the metrology conference. Fewer defect papers were submitted for this year's metrology conference than last, he notes, adding that the quality of the submissions is "outstanding."

A five-paper session on CD control for photomasks is a first for the metrology conference, says Sullivan, technology group manager at Schlumberger Semiconductor Solutions in Concord, MA. "That's the first time we've ever had more than a single paper or two on mask CD control. Now, you can see the interaction of the mask and the wafer. That area is being looked at more carefully as pushing optical technology reaches its limits."

More technical papers are focused on this area because "the CD space is starting to head more toward process control, and the emphasis on SEM as a single technology is supplemented by the appearance of scatterometry and other methods of CD control," the conference chair says. The inclusion of these papers reflects fresh concerns by chipmakers using different types of photoresists and antireflective coatings coupled with phase-shift masks and optical proximity correction (OPC) techniques.

The shape of feature sizes has taken on increased importance, process experts note. New projects at International Sematech are exploring ways to discern the shape of the line from other data that are normally available. The critical dimension "is a distance between two points...but that distance can be an infinite number of shapes," Sullivan notes. "It's becoming critical to understand more about the features you're manufacturing in order to predict and control the process. In the photolithography area, they're squeezing everything they can out of the reticle by going to phase shift and OPC. In metrology, they're squeezing everything by using more of the information provided in the images."

Sullivan believes tracking each year's submissions reveals the evolution of metrology and process control technology. "As technology evolves, you wind up with some implementation issues where people are taking a technology and not saying, 'Look what this can do.' They're saying, 'Look what it does in my process and how it's impacting my ability to control my process and understand variations in the stepper or scanner field.'" The appearance of scatterometry sessions both this year and last, in addition to CD control papers, shows wider acceptance of a technique that has moved "from a laboratory curiosity into more-mainstream utilization. This is speculation on my part, but it's most likely that within the developmental areas of these fabs, if you follow the evolution, next year you'll have people talking about production parameters."

The symposium features three conferences in addition to the one on metrology, inspection, and process control: emerging lithographic technologies, resist technologies and processing, and optical lithographies. Poster sessions are scheduled all day February 26 and February 28, with the authors present between 5:30 and 8 p.m. both days to answer questions. Poster topics include KrF and ArF processing, ARC, simulation, phase-shift masks, and lens technology.

A panel discussion hosted by BACUS on photomask technologies will address the topic, "Reticle Defects: Will They Break Moore's Law?" A joint session for participants in the lithographic technologies, resist technologies, and optical microlithography conferences features seven papers on different aspects of molecular contamination. The photolithography technical group will host a panel discussion February 27 to address the requirements for the introduction of 157-nm lithography.

Two plenary presentations will take place February 26. Karen Brown, deputy director of NIST, will deliver the keynote address on future technologies. Dennis Buss, vp of silicon technology development for Texas Instruments, will discuss DSPs and other devices that are driving growth in the Internet era. The trade show will be open February 27–28 between 10 a.m. and 4 p.m.

Sullivan notes that the metrology conference covers areas, particularly CD-SEM, that are mentioned as requirements in the recent technology roadmap. "I think a lot of the drive for new metrology technologies such as scatterometry directly correlates to pushing the pace of technology. As your linewidth sizes are reduced, process control by a single metric, for example the critical dimension, becomes more difficult because there are more feature attributes that are factored into the performance of the device." In other words, "I can still have devices that will give me a good in-line CD, but I'll actually have yield problems that are related to another attribute of my process, [such as] sidewalls."

For more information on SPIE Microlithography and the companies exhibiting there, go to http://www.spie.org/info/ml

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