Volume production of 45nm node devices utilizing Nikon's S610C immersion lithography tool has started. Important to the success in achieving high-yields in volume production with immersion lithography has been defectivity reduction. In this study we evaluate several methods of defectivity reduction. The tools used in our defectivity analysis included a dedicated immersion cluster tools consisting of a Nikon S610C, a volume production immersion exposure tool with NA of 1.3, and a resist coater-developer LITHIUS i+ from TEL. In our initial procedure we evaluated defectivity behavior by comparing on a topcoat-less resist process to a conventional topcoat process. Because of its simplicity the topcoatless resist shows lower defect levels than the topcoat process. In a second study we evaluated the defect reduction by introducing the TEL bevel rinse and pre-immersion bevel cleaning techniques. This technique was shown to successfully reduce the defect levels by reducing the particles at the wafer bevel region. For the third defect reduction method, two types of tool cleaning processes are shown. Finally, we discuss the overall defectivity behavior at the 45nm node. To facilitate an understanding of the root cause of the defects, defect source analysis (DSA) was applied to separate the defects into three classes according to the source of defects. DSA analysis revealed that more than 99% of defects relate to material and process, and less than 1% of the defects relate to the exposure tool. Material and process optimization by collaborative work between exposure tool vendors, track vendors and material vendors is a key for success of 45nm node device manufacturing.

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.

Immersion lithography is becoming a realistic method of high resolution pattern generation for semiconductor manufacturing. Nikon has a roadmap of full-field immersion exposure tools starting with an Engineering Evaluation Tool (EET, NA=0.85), succeeded with production models of S609B (NA=1.07) and S6xx (NA=1.30). EET was constructed in 2004, and is being used for evaluation of immersion technology and process development. With EET, focus, stepping, overlay and across-wafer CD uniformity data are demonstrated to be better or equivalent to dry tools, while the depth of focus (DOF) is significantly improved as expected. A remarkable point is the defectivity result with EET. We have detected no bubbles and a negligible level of "immersion specific" defects even with hydrophobic top coat. A production model S609B will have the NA=1.07 optics, which will be the highest NA of "all refractive optics", and will be shipped at 2005/4Q. S6xx, with planned shipment timing is 2006/2H, will have NA=1.30 catadioptric optics, whose NA will be the highest NA of "water-immersion". Both S609B and S6xx will be equipped with loss-less polarized illuminators, which will enable 50nm L/S with S609B and 42nm L/S with S6xx. Resist and top coat are studied from the viewpoints of chemical contamination and scanning properties. Tentative specifications are proposed for leaching of PAG and amines against chemical contamination. As for scanning properties, static contact angle was found to be not a good parameter; instead, sliding angle is proposed.

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