Three-dimensional profile extraction from CD-SEM image and top/bottom CD measurement by line-edge roughness analysis

Atsuko Yamaguchi; Takeyoshi Ohashi; Takahiro Kawasaki; Osamu Inoue; Hiroki Kawada

doi:10.1117/12.2013422

18 April 2013 Three-dimensional profile extraction from CD-SEM image and top/bottom CD measurement by line-edge roughness analysis

Atsuko Yamaguchi, Takeyoshi Ohashi, Takahiro Kawasaki, Osamu Inoue, Hiroki Kawada

Author Affiliations +

Proceedings Volume 8681, Metrology, Inspection, and Process Control for Microlithography XXVII; 86812Z (2013) https://doi.org/10.1117/12.2013422
Event: SPIE Advanced Lithography, 2013, San Jose, California, United States

Abstract

A new method for calculating critical dimension (CDs) at the top and bottom of three-dimensional (3D) pattern profiles from a critical-dimension scanning electron microscope (CD-SEM) image, called as “T-sigma method”, is proposed and evaluated. Without preparing a library of database in advance, T-sigma can estimate a feature of a pattern sidewall. Furthermore, it supplies the optimum edge-definition (i.e., threshold level for determining edge position from a CDSEM signal) to detect the top and bottom of the pattern. This method consists of three steps. First, two components of line-edge roughness (LER); noise-induced bias (i.e., LER bias) and unbiased component (i.e., bias-free LER) are calculated with set threshold level. Second, these components are calculated with various threshold values, and the threshold-dependence of these two components, “T-sigma graph”, is obtained. Finally, the optimum threshold value for the top and the bottom edge detection are given by the analysis of T-sigma graph. T-sigma was applied to CD-SEM images of three kinds of resist-pattern samples. In addition, reference metrology was performed with atomic force microscope (AFM) and scanning transmission electron microscope (STEM). Sensitivity of CD measured by T-sigma to the reference CD was higher than or equal to that measured by the conventional edge definition. Regarding the absolute measurement accuracy, T-sigma showed better results than the conventional definition. Furthermore, T-sigma graphs were calculated from CD-SEM images of two kinds of resist samples and compared with corresponding STEM observation results. Both bias-free LER and LER bias increased as the detected edge point moved from the bottom to the top of the pattern in the case that the pattern had a straight sidewall and a round top. On the other hand, they were almost constant in the case that the pattern had a re-entrant profile. T-sigma will be able to reveal a re-entrant feature. From these results, it is found that T-sigma method can provide rough cross-sectional pattern features and achieve quick, easy and accurate measurements of top and bottom CD.

Citation Download Citation

Atsuko Yamaguchi, Takeyoshi Ohashi, Takahiro Kawasaki, Osamu Inoue, and Hiroki Kawada "Three-dimensional profile extraction from CD-SEM image and top/bottom CD measurement by line-edge roughness analysis", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 86812Z (18 April 2013); https://doi.org/10.1117/12.2013422

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