14 October 2011 PPF-Explorer: pointwise proximity function calibration using a new radial symmetric calibration structure
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Proceedings Volume 8166, Photomask Technology 2011; 81660P (2011); doi: 10.1117/12.896759
Event: SPIE Photomask Technology, 2011, Monterey, California, United States
Abstract
Lithographic patterning encounters growing challenges to meet the requirements of current and future semiconductor technology nodes. Even e-beam lithography is challenged due to the physical characteristic of the whole transfer process including the e-beam blur, electron scattering, and resist effects. These effects cause an unavoidable blurring of the exposed shapes and are often described as process proximity effect. Besides the correction of this process proximity effect pattern contrast and process window for the lithography step have to be regarded. There are promising approaches for contrast enhancing proximity effect correction concepts. To enable a stable patterning great efforts have to be put into decreasing the errors of all involved technologies. The blurring resulting from the transfer process is usually described by a so-called process proximity function (PPF) and mostly approximated by a superposition of two or more Gaussian functions. All algorithms for proximity effect correction use that PPF to perform their correction. Thus, an accurate determination of that PPF contributes to reducing the error budget of the proximity effect correction scheme. Several methods for PPF calibration were introduced in the past. Some are based on modelling the transfer process and performing Monte Carlo simulations. Another common approach is to design and expose calibration patterns, measure the resulting CDs, and obtain the process proximity function as the result of a simulation based parameter fitting to a model function such as a sum of Gaussian functions. In order to respect the increased accuracy requirements an even more accurate description of the PPF is expected. This paper describes the newly developed PPF-explorer method for the calibration of a pointwise proximity function as a complementary technique, which is based on the exposure and evaluation of new calibration layouts. Following the common assumption that a process proximity function is radial-symmetric, we developed radial-symmetric calibration layouts.
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R. Galler, M. Krueger, D. Melzer, L. E. Ramos, M. Suelzle, U. Weidenmueller, "PPF-Explorer: pointwise proximity function calibration using a new radial symmetric calibration structure", Proc. SPIE 8166, Photomask Technology 2011, 81660P (14 October 2011); doi: 10.1117/12.896759; https://doi.org/10.1117/12.896759
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KEYWORDS
Calibration

Monte Carlo methods

Electron beam lithography

Cadmium sulfide

Lithography

Photoresist processing

Critical dimension metrology

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