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KLA-Tencor Combats Lithography Focus-Related Yield Loss at 130 nm and Below with Industry's First Inline Focus-Exposure Monitoring Solution
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SAN JOSE, Calif., June 24, 2003-KLA-Tencor (NASDAQ: KLAC) today introduced MPX-a new option on its Archer overlay metrology tool series that enables lithographers to control stepper defocus and exposure variations in sub-130-nm IC production. MPX is a cost-effective, non-destructive focus-exposure product wafer monitor that leverages unique dual-tone-design targets and analysis software to enable lithographers to decouple focus from exposure with a high degree of precision. Armed with this information, lithographers can quickly isolate the sources of stepper variations and determine the necessary corrective actions to minimize their impact on device performance and yields. As the industry's first inline focus-exposure monitoring solution, MPX can help chipmakers save millions of dollars per year by reducing focus-related yield loss.

Staying within focus: the dilemma with shrinking focus and exposure windows
Focus-exposure control in lithography is a key challenge for critical dimension (CD) control at the 130-nm technology node and below. Unseen lithography focus-exposure excursions can result in CD process variations that lead to lower yields, cause unnecessary and costly rework, as well as reduce scanner productivity. At 130 nm and below, focus errors alone account for as much as 50 percent of the CD variation on product wafers due to shrinking focus windows (the amount of allowable focus latitude). This has given rise to a critical new requirement: monitoring focus and exposure variations inline in order to maintain tight CD control at these advanced design rules. Until now, lithographers have not had the ability to separate focus and exposure parameters. Instead, they have been forced to rely on exposure data alone to control both exposure- and focus-related excursions. However, stepper corrections that are based only on exposure parameters can significantly reduce process latitude-ultimately resulting in processes that are out of spec, as well as subsequent yield loss. To meet the production requirements for sub-130-nm design rules, lithographers must be able to cost-effectively monitor and segment the contributing components of focus and exposure to determine the appropriate corrective action.

"For low-runner flash memory in early production, focus errors can lower yields by several percent," stated Sean Hannon, metrology engineer at AMD's Fab 25 based in Austin, Texas. "The most serious deficiency in focus-exposure control is the lack of a monitor that can work directly on product wafers. MPX provides a method for rapidly characterizing stepper defocus and exposure variations across field and across wafer, enabling us to optimize our lithography processes for a new product or technology using the very first wafer ever exposed."

Until MPX, there has been no cost-effective and reliable way to monitor focus on product wafers. With its ability to decouple focus and exposure information on product wafers with high precision, MPX provides fast and accurate feedback on the key parameters needed to maintain tight CD control. Current methodologies do not have the ability to decouple focus from exposure, and focus information is achieved through periodic off-line monitoring of the exposure tool. This is done by printing a focus-exposure matrix on a test wafer, which is then measured with a CD SEM tool. However, given the tight focus error budget and increased focus monitoring requirements for sub-130-nm production, this method reduces the scanner's availability to pattern product wafers on the production floor, resulting in lost productivity. Using MPX, lithographers can achieve improved stepper productivity and implement lot-to-lot focus monitoring to maintain shrinking focus budget requirements.

"In today's deep sub-micron production era, every nanometer's worth of process variance can count toward the success or failure of the lithography process," stated Ofer Greenberger, vice president and general manager of KLA-Tencor's Optical Metrology Division. "MPX provides significant cost-of-ownership benefits to our Archer customers by enabling them to monitor all stepper controls-overlay, focus and exposure-with a single metrology tool solution that is extendible to the 65-nm node and beyond."

According to Greenberger, leading-edge semiconductor manufacturers are spending more time on focus-exposure control to obtain satisfactory yields below 130 nm. "In some cases, this additional time amounts to a one- to three-percent loss of scanner utilization, resulting in millions of dollars in lost revenue per scanner per year. In a large 300-mm fab, this could add up to more than $100 million in lost revenue per year. One of our leading-edge customers, who was both capacity- and yield-limited at its latest technology node, calculated that the incremental ROI for shifting focus-exposure control measurements to product wafers more than justified the cost of Archer MPX. In fact, incremental ROI models show payback of ten-fold or greater, depending on the level of overall equipment effectiveness and yield improvement."

Industry's first inline focus-exposure monitor
MPX is a technology that leverages analysis software in conjunction with unique dual-tone, line-end-shortening (LES) targets. Licensed from IBM, these targets are designed to simultaneously provide separate exposure and focus measurements. The extremely small dimensions of these targets (22 micron x 13 micron) enable them to be easily placed at multiple locations within the constraints of the scribe lines on product wafers. Due to their grating-style design, the LES targets are not limited by device design rules, and are inherently more sensitive to focus and exposure changes than actual device linewidths.

Delivering the sensitivity to determine exposure dose to within one percent, and scanner focus offset to within 50 nm, MPX provides lithographers with a stable, robust focus-exposure product wafer monitor that helps reduce the contribution of focus error to negligible levels. MPX can also be used to selectively sample wafer-edge die to quickly identify and correct potential yield-killing focus excursions on the wafer edges. In addition, MPX can conduct across-field and across-wafer focus tilt monitoring.

Comprehensive CD process window monitoring
MPX also complements KLA-Tencor's existing SpectraCD-PWM™ (Process Window Monitor) automated tool monitoring solution by acting as an alarm that can trigger additional CD process window monitoring in the event of excursions. This enables lithographers to respond rapidly when a problem occurs, and address it before it can result in catastrophic yield losses.

KLA-Tencor's Archer platform consists of the Archer 10, Archer 10XT and Archer AIM, and has a global installed base of more than 150 tools. KLA-Tencor is currently accepting orders for the MPX upgrade.


About KLA-Tencor: KLA-Tencor is the world leader in yield management and process control solutions for semiconductor manufacturing and related industries. Headquartered in San Jose, Calif., with operations around the world, KLA-Tencor ranked #6 on S&P's 2002 index of the top 500 companies in the U.S. KLA-Tencor is traded on the Nasdaq National Market under the symbol KLAC. Additional information about the company is available on the Internet at http://www.kla-tencor.com.

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SpectraCD-PWM is a trademark of KLA-Tencor.

Contact:
Meggan Powers
Director Corporate Communications

 

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