Proceedings Article | 26 March 2007
Katsushi Nakano, Hiroshi Kato, Tomoharu Fujiwara, K. Shiraishi, Yasuhiro Iriuchijima, Soichi Owa, Irfan Malik, Steve Woodman, Prasad Terala, Christine Pelissier, Haiping Zhang
KEYWORDS: Semiconducting wafers, Particles, Immersion lithography, Inspection, Wafer inspection, Bridges, Photoresist processing, Optical lithography, Calibration, Defect inspection
ArF immersion lithography has become accepted as the critical layer patterning solution for lithography going forward.
Volume production of 55 nm devices using immersion lithography has begun. One of the key issues for the success of
volume production immersion lithography is the control of immersion defectivity. Because the defectivity is influenced
by the exposure tool, track, materials, and the wafer environment, a broad range of analysis and optimization is needed
to minimize defect levels. Defect tests were performed using a dedicated immersion cluster consisting of a volume
production immersion exposure tool, Nikon NSR-S609B, having NA of 1.07, and a resist coater-developer, TEL
LITHIUS i+.
Miniaturization of feature size by immersion lithography requires higher sensitivity defect inspection. In this
paper, first we demonstrate the high sensitivity defect measurement using a next generation wafer inspection system,
KLA-Tencor 2800 and Surfscan SP2, on both patterned and non-patterned wafers. Long-term defect stability is very
important from the viewpoint of device mass production. Secondly, we present long-term defectivity data using a
topcoat-less process. For tool and process qualification, a simple monitor method is required. Simple, non-pattern
immersion scanned wafer measurement has been proposed elsewhere, but the correlation between such a non-pattern
defect and pattern defect must be confirmed. In this paper, using a topcoat process, the correlation between topcoat
defects and pattern defects is analyzed using the defect source analysis (DSA) method. In case of accidental tool
contamination, a cleaning process should be established. Liquid cleaning is suitable because it can be easily introduced
through the immersion nozzle. An in-situ tool cleaning method is introduced. A broad range of optimization of tools,
materials, and processes provide convincing evidence that immersion lithography is ready for volume production chip
manufacturing.
