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A dynamic receding contact angle (RCA) is a well-known guideline to estimate the degree of watermark (WM) defects, which shapes circle and bridges inside of the defect and reduces with enlarging the RCA of topcoat (TC). However, our recent investigation revealed the occurrence of the circular shape defects in spite of using the TC with a large RCA, bringing about a change of line and space pattern pitch. In this paper, we clarify the origin of these defects and propose a new key factor of the dynamic surface properties of immersion-specific defects. It was found that the pitch-change defect is caused by the lens effect of the air bubbles embedded between advancing water meniscus and the TC. To well understand generation of the bubble defects, we defined the "effective" hysteresis (EH) as the hysteresis of dynamic contact angle taken the effects of water-absorption into account. An analysis with the EH indicates that the bubble defect arises from not only to the large ACA but also small amount of water uptake and the amount of water-absorption could be substituted by the dissolution rate of TC. It was demonstrated that the EH proposed is a new key factor for estimating the number of bubble defects. The EH is very useful for analyzing the bubble defects in immersion lithography. The characteristics of the bubble defect are also discussed with a focus on the structure of the polymer attached to water.

We have developed a new ArF-RELACS (Resolution Enhancement Lithography Assisted by Chemical Shrink) material called AZ-LExp.R720. The principle and process procedure of LExp.R720 are almost identical to those previously developed with KrF lithography. The extent of crosslinking reactions and the mobility balance of chemical components at the boundary between resist and the RELACS film is adjusted to ArF resist chemistry. LExp.R720 can vary shrinkage from 10 to 40nm by controlling the process conditions, mainly the mixing bake temperature. The amount of shrinkage is independent of pattern pitch and focus. We confirmed that pattern profile, lithography margin, CD uniformity, etching resistance, and pattern defects were not deteriorated by the RELACS process with deionized water development. L.ExpR720 was able to get an amount of shrinkage with several of ArF resists, which has commercial applications. In conclusion, we believe that LExp.R720 is extremely useful for 65 nm node and next generation devices.

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