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5 November 2005 Compensating mask topography effects in CPL through-pitch solutions toward the 45nm node
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Different types of phase shifting masks in combination with the proper illumination condition are widely used to allow 193nm lithography to print ever-decreasing pitches with sufficient process window. A viable option for the 65nm and 45nm node is chromeless phase lithography (CPL), which combines a chromeless phase shift mask and 193nm off-axis illumination. Previously, we demonstrated that imaging-wise the π-shift is not entirely reached in narrow mask features, although etched to the nominal etch depth. This is caused by the mask 3D effect, and manifests itself in through focus Bossung tilt/shift issues. In particular, 3D mask simulations suggested that an effective π phase shift could be recovered for the narrow chromeless mask features by applying a larger than nominal etch depth. In this work, the applicability of this solution is considered in more detail. Experimental through-pitch solutions for regular line/space patterns using CPL, obtained on three latest generations of ASML ArF scanners: 0.75NA (PAS5500 /1100), 0.85NA (XT:1250Di), and 0.93NA (XT:1400i) are demonstrated. Importantly, it is illustrated that mask etch depth adjustment is a widely applicable practical solution to the CPL Bossung tilt/shift issue. The effect of source shape, increasing NA, as well as the effect of immersion versus 'dry' lithography is evaluated. Additionally, the ultimate resolution limits at 0.93NA (XT:1400) are explored. Data obtained on a Zeiss AIMS fab193i shows to be in line with both the exposure data and the 3D simulated data, confirming the clear reduction of focus tilt/shift when using the larger than nominal etch depth.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Joost Bekaert, Vicky Philipsen, Geert Vandenberghe, Doug van den Broeke, Wolfgang Degel, and Axel Zibold "Compensating mask topography effects in CPL through-pitch solutions toward the 45nm node", Proc. SPIE 5992, 25th Annual BACUS Symposium on Photomask Technology, 59921O (5 November 2005);

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