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11 June 1999 Printing various feature types at low k factors with advanced i-line negative resists
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Lithographic conditions are typically optimized for a specific feature type; while some levels expose lines and spaces, others target contacts and islands. In today's challenging lithographic environment, printing multiple feature types on the same reticle is being discussed. The overlapping process window must then be considered. It is well-established in the industry that, for DNQ systems, two dimensional structures print at different doses than one dimensional structures of the same nominal chrome or clear size on the reticle. In this paper, the overlapping or common process window for all of these features is examined using a state-of-the-art i-line negative photoresist. When evaluating depth of focus (DOF) and exposure latitude, a +/- 0.10 micrometers deviation from target was used. Contact holes consistently limited the common process window. Three illumination conditions were examined: 0.57 NA with 0.38 sigma, 0.57 NA with 0.67 sigma, and 0.60 NA with 0.38 sigma. For total common process window, the 0.57 NA and 0.38 sigma condition was found to be optimal. PROLITH/2 aerial image simulations were found to agree with experimental result regarding an increased common exposure latitude with high NA and low sigma. The nominal feature dimensions were: 0.44 micrometers isolated lines, 0.44 micrometers isolated spaces, 0.4 X 1.5 micrometers contact,s and 0.4 X 1.5 micrometers islands. The nominal dimensions for contacts and islands were chosen to maintain a 3:1 area rule should the minimum dimension be used for one side of the features. The importance of a minimum area rule is discussed. Some early work on a second i-line negative resist targeted to simultaneously print 0.30-0.40 micrometers lines and spaces with 0.35-0.50 micrometers 2 contacts and islands is mentioned.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. Alexander Chediak, Derek Y. Chen, David T. Long, Premlatha Jagannathan, Charles Richwine, and Laura Benner "Printing various feature types at low k factors with advanced i-line negative resists", Proc. SPIE 3678, Advances in Resist Technology and Processing XVI, (11 June 1999);

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