Scatterometry measurement of asymmetric gratings

Jie Li; Justin J. Hwu; Yongdong Liu; Silvio Rabello; Zhuan Liu; Jiangtao Hu

doi:10.1117/12.839821

11 December 2009 Scatterometry measurement of asymmetric gratings

Jie Li, Justin J. Hwu, Yongdong Liu, Silvio Rabello, Zhuan Liu, Jiangtao Hu

Proceedings Volume 7520, Lithography Asia 2009; 75201B (2009) https://doi.org/10.1117/12.839821
Event: SPIE Lithography Asia, 2009, Taipei, Taiwan

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.

Citation Download Citation

Jie Li, Justin J. Hwu, Yongdong Liu, Silvio Rabello, Zhuan Liu, and Jiangtao Hu "Scatterometry measurement of asymmetric gratings", Proc. SPIE 7520, Lithography Asia 2009, 75201B (11 December 2009); https://doi.org/10.1117/12.839821

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KEYWORDS

Picosecond phenomena

Scatterometry

Atomic force microscopy

Lithography

Calibration

Critical dimension metrology

Photoresist processing

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