Special Section on Metrology

Mueller matrix measurement of asymmetric gratings

[+] Author Affiliations
Jie Li

Nanometrics Inc., 1550 Buckeye Drive, Milpitas, California 95035,

Justin J. Hwu

Seagate Technology, 47010 Kato Road, Fremont, California 94538

Yongdong Liu, Silvio Rabello, Zhuan Liu, Jiangtao Hu

Nanometrics Inc., 1550 Buckeye Drive, Milpitas, California 95035

J. Micro/Nanolith. MEMS MOEMS. 9(4), 041305 (December 17, 2010). doi:10.1117/1.3514708
History: Received March 31, 2010; Revised August 19, 2010; Accepted September 28, 2010; Published December 17, 2010; Online December 17, 2010
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Scatterometry has been used extensively for the characterization of critical dimensions (CDs) and detailed sidewall profiles of periodic structures in microelectronics fabrication processes. In most cases devices are designed to be symmetric, although errors could occur during the fabrication process and result in undesired asymmetry. Conventional optical scatterometry techniques have difficulties distinguishing between left and right asymmetries. We investigate the possibility of measuring grating asymmetry with Mueller matrix spectroscopic ellipsometry (MM-SE) for a patterned hard disk sample prepared by a nanoimprint technique. The relief image on the disk sometimes has an asymmetrical sidewall profile, presumably due to the uneven separation of the template from the disk. Cross section SEM reveals that asymmetrical resist lines are typically tilted toward the outer diameter direction. 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 methods. 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 for which symmetric structures are desired.

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© 2010 Society of Photo-Optical Instrumentation Engineers

Citation

Jie Li ; Justin J. Hwu ; Yongdong Liu ; Silvio Rabello ; Zhuan Liu, et al.
"Mueller matrix measurement of asymmetric gratings", J. Micro/Nanolith. MEMS MOEMS. 9(4), 041305 (December 17, 2010). ; http://dx.doi.org/10.1117/1.3514708


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