Tuesday, February 24th, 2009

At the Nikon Lithovisions 2009 Symposium on February 22 this year in San Jose, California, Masato Hamatani described the features and beta test results for the NSR-S620 scanning immersion exposure tool, optimized for double patterning lithography. While the tool boasts only one wafer stage, its “Streamlign Platform” concept shoots 200 wafers per hour with 2nm overlay precision after a promised 2 week tool installation time. “The key number is 222,” Hamatani said.

Achieving such a high throughput without using tandem wafer stages meant speeding up the alignment and metrology steps as well as scan speed. The S620’s (see figure) 5-eye FIA system registers aligment marks in 5 different scribe lines on the wafer with 5 different microscopes simultaneously. The “Stream alignment” system measures wafer height at many places across the wafer with a moving laser beam. Together, these innovations mean that the wafer needs only to be scanned in one dimension through the metrology system (rather than serpentined) before exposures begin.

A dual-stage servo system with four glass scale encoders, many read heads, and a full interferometer in parallel enable a speed of 700m/s with 1ms settling time. The reticle stage acceleration is 12.5 Gs, but the sync accuracy is <1nm (moving average) with <3nm moving standard deviation.

A more complete description of the system will be presented at the SPIE Lithography Symposium this Friday, February 27. The tool is scheduled for first shipment in the fouth quarter of 2009. –M.D.L.

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