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Proceedings Paper

Evaluation of a new model of mask topography effects
Author(s): Christophe Pierrat
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Paper Abstract

A new method for simulating mask topography effects is described. A model comprising a set of functions is generated based on the results of test patterns simulated using rigorous mask simulation. The functions are combined with the thin mask diffraction pattern in order to create a modeled thick mask diffraction pattern. The mask diffraction pattern is subsequently used in the lithosimTM simulation tool to generate the wafer image. Results are described for 1D and 2D test structures. The 1D test structures is a line and space test pattern where the line is set at 40nm width and the space is varied from 40nm to 1000nm. The illumination setting chosen was a TE polarized dipole illumination with a pole distance of 0.9 and a pole radius of 0.01. First the accuracy of the simulator itself was verified using thin mask calculation and comparing the data to another simulator. The intensity profiles are virtually identical. The RMS of the difference between the two plots is 8E-05. Next the model is compared to the rigorous calculation. The RMS of the difference between the two plots is 3E-03. The standard deviation of the CD difference between the model and the rigorous calculation, calculated for 5 thresholds (0.1, 0.11, 0.12, 0.13, and 0.14) and for all the structures, is 0.38nm. We also demonstrate that the mask model can be used with different optical settings by showing an example of two additional defocus values with an identical RMS of 3E-03. For the 2D test pattern made of a dense contact array, the mask fields are computed using rigorous calculation and compared to the model. The difference between the fields is within the error of the rigorous calculation. The resulting wafer images are almost identical. No re-scaling of the data was applied to either the mask fields or the wafer images.

Paper Details

Date Published: 25 September 2010
PDF: 11 pages
Proc. SPIE 7823, Photomask Technology 2010, 78230W (25 September 2010); doi: 10.1117/12.864264
Show Author Affiliations
Christophe Pierrat, IC Images Technologies (United States)


Published in SPIE Proceedings Vol. 7823:
Photomask Technology 2010
M. Warren Montgomery; Wilhelm Maurer, Editor(s)

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