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Proceedings Paper

Scatterometry measurement of asymmetric gratings
Author(s): Jie Li; Justin J. Hwu; Yongdong Liu; Silvio Rabello; Zhuan Liu; Jiangtao Hu
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Paper Abstract

Scatterometry has been used extensively for the characterization of critical dimensions (CD) and detailed sidewall profiles of periodic structures in microelectronics fabrication processes. So far the majority of applications are for symmetric gratings. In most cases devices are designed to be symmetric although errors could occur during fabrication process and result in undesired asymmetry. The problem with conventional optical scatterometry techniques lies in the lack of capability to distinguish between left and right asymmetries. In this work we investigate the possibility of measuring grating asymmetry using Mueller matrix spectroscopic ellipsometry (MM-SE). A patterned hard disk prepared by nano-imprint technique is used for the study. The relief image on the disk sometimes has asymmetrical sidewall profile, presumably due to the uneven separation of the template from the disk. The undesired tilting resist profile causes difficulties to the downstream processes or even makes them fail. Cross-section SEM reveals that the asymmetrical resist lines are typically tilted towards the outer diameter direction. The simulation and experimental data show that certain Mueller matrix elements are proportional to the direction and amplitude of profile asymmetry, providing a direct indication to the sidewall tilting. The tilting parameter can be extracted using rigorous optical critical dimension (OCD) modeling or calibration method. We demonstrate that this technique has good sensitivity for measuring and distinguishing left and right asymmetry caused by sidewall tilting, and can therefore be used for monitoring processes, such as lithography and etch processing, for which symmetric structures are desired.

Paper Details

Date Published: 11 December 2009
PDF: 10 pages
Proc. SPIE 7520, Lithography Asia 2009, 75201B (11 December 2009); doi: 10.1117/12.839821
Show Author Affiliations
Jie Li, Nanometrics Inc. (United States)
Justin J. Hwu, Seagate Technology (United States)
Yongdong Liu, Nanometrics Inc. (United States)
Silvio Rabello, Nanometrics Inc. (United States)
Zhuan Liu, Nanometrics Inc. (United States)
Jiangtao Hu, Nanometrics Inc. (United States)

Published in SPIE Proceedings Vol. 7520:
Lithography Asia 2009
Alek C. Chen; Woo-Sung Han; Burn J. Lin; Anthony Yen, Editor(s)

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