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1 April 2008 AltPSM contact hole application at DRAM 4xnm nodes with dry 193nm lithography
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To avoid expensive immersion lithography and to further use existing dry tools for critical contact layer lithography at 4Xnm DRAM nodes the application of altPSM is investigated and compared to attPSM. Simulations and experiments with several test masks showed that by use of altPSM with suitable 0°/180° coloring and assist placement 30nm smaller contacts can be resolved through pitch with sufficient process windows (PW). This holds for arrays of contacts with variable lengths through short and long side pitches. A further benefit is the lower mask error enhancement factor (MEEF). Nevertheless 3D mask errors (ME) consume benefits in the PW and the assist placement and coloring of the main features (MF) put some constraints on the chip design. An altPSM compatible 4Xnm full-chip layout was realized without loss of chip area. Mask making showed very convincing results with respect to CDU, etch depth uniformity and defectiveness. The printed intra-field CD uniformity was comparable to attPSM despite the smaller target CDs. Room for improvement is identified in OPC accuracy and in automatic assist placement and sizing.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Christoph Noelscher, Thomas Henkel, Franck Jauzion-Graverolle, Mario Hennig, Nicolo Morgana, Ralph Schlief, Molela Moukara, Roderick Koehle, and Ralf Neubauer "AltPSM contact hole application at DRAM 4xnm nodes with dry 193nm lithography", Proc. SPIE 6924, Optical Microlithography XXI, 692446 (1 April 2008);


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