15 March 2006 Immersion effects on lithography system performance
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The immersion effects on lithography-system performance have been investigated using a ASML TWINSCAN XT:1250Di immersion-ArF scanner (NA=0.85) and Tokyo Electron CLEAN TRACK ACT12 at IMEC. Effects of immersion-induced-temperature change and effects of material-top surface are discussed in this paper. The wafer-stage temperature is measured during the leveling-verification tests and compared with the observed residual-focus-error change. The results indicate that stage-temperature change under an immersion environment can induce a focus change. In this paper, it was proved that the improved-temperature-control stage is effective to mitigate the immersion-specific focus change. The immersion effect on overlay is also investigated as a function of material top surface. It was demonstrated that the effect of material-receding-contact angles on the grid-residual errors (non-correctable errors) is small in the latest-immersion-hardware configuration of the scanner. However, there was a tendency that material with a smaller-receding-contact angle has a larger-wafer scaling although it is a correctable parameter. This can be caused by the first-layer wafer shrinkage due to more water evaporation on the more-hydrophilic surface. The immersion effect on scanner-dynamic performance is then investigated by changing the material-top surface and the scan speed of the scanner. It was turned out that the scan synchronization is not much affected by differences of material receding-contact-angles for the new configuration of the scanner. Moving-standard deviation of the synchronization error in scanning direction (y-direction) is slightly more affected by increased scanning speed, although it stays within specification even at a maximum scan speed of 500 mm/sec. Finally the immersion effects on resist-profile uniformity are examined. It was found that lower-leaching-film stacks (with a top coat or a lower leaching resist) seem to mitigate the variation of resist-profile uniformity.
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Seiji Nagahara, Seiji Nagahara, Ivan Pollentier, Ivan Pollentier, Takahiro Machida, Takahiro Machida, Sean O'Brien, Sean O'Brien, Eric Jacobs, Eric Jacobs, Charles Schaap, Charles Schaap, Philippe Leray, Philippe Leray, Greet Storms, Greet Storms, Kathleen Nafus, Kathleen Nafus, David Laidler, David Laidler, Shaunee Cheng, Shaunee Cheng, "Immersion effects on lithography system performance", Proc. SPIE 6154, Optical Microlithography XIX, 61540U (15 March 2006); doi: 10.1117/12.659620; https://doi.org/10.1117/12.659620

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