Dr. Rayan M. Alassaad Profile

Dr. Rayan M. Alassaad

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Publications (4)

SPIE Journal Paper | 1 January 2008

Physical characterization of nanoimprinted polymer nanostructures using visible light angular scatterometry

Rayan Alassaad, Li Tao, Wenchuang Hu

JM3, Vol. 7, Issue 01, 013008, (January 2008) https://doi.org/10.1117/12.10.1117/1.2894772

KEYWORDS: Polymers, Polymethylmethacrylate, Scatterometry, Nanostructures, Reflectivity, Electron beam lithography, Scanning electron microscopy, Nanoimprint lithography, Visible radiation, Cadmium sulfide

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Proceedings Article | 5 April 2007 Paper

Visible light angular scatterometry for nanolithography

Rayan Al-Assaad, Li Tao, Wenchuang Hu

Proceedings Volume 6518, 651839 (2007) https://doi.org/10.1117/12.712486

KEYWORDS: Scatterometry, Polymethylmethacrylate, Reflectivity, Electron beam lithography, Nanoimprint lithography, Polymers, Scanning electron microscopy, Metrology, Silicon, Error analysis

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Proceedings Article | 16 July 2002 Paper

Mathematical analyses of inverse scatterometry

Emmanuel Drege, Rayan Al-Assaad, Dale Byrne

Proceedings Volume 4689, (2002) https://doi.org/10.1117/12.473453

KEYWORDS: Scatterometry, Error analysis, Diffraction, Reflectivity, Diffraction gratings, Structural design, Metrology, Optical design, Lithography, Semiconductors

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Optical scatterometry has been proven to be a useful tool for the inspection and assessment of lithographic processes. The characteristic signature of the scattergram provides information about the surface relief profile and can be rapidly and non-invasively acquired. Currently, attention is being focused on the inversion of scatterometric data to determine the surface profile of the relief structure. To overcome the highly non-linear relationship between the properties of the diffracting structure and the diffraction measurements, we present a linearized solution based on a least-squared refinement method. This approach relies on the reliability of lithographic processes, which allows us to determine the departures of structural key parameters from a set of expected design values. This linearized inversion, as shown by the mathematical formalism, is independent of the scatterometric measurement configuration. Hence it can be applied whether, for example, the incident angle or wavelength of the light is varied to acquire either irradiance of phase information. This is validated in this paper by various examples handling the retrieval of three geometrical parameters (groove depth, line width, and sidewall angle) from reflectance data simulated using the rigorous coupled-wave theory (RCWT) for both angular and wavelength scans. An additional benefit of the proposed linearized solution is the ability to examine mathematically the significance of measurement errors. An analytical propagation of error is presented, connecting measurement noise to the soughed parameter precisions and uncertainties. We applied this formalism to the cases mentioned above, where we simulated the retrieval of three parameters from measurements containing various levels of noise. This studies allows us to draw preliminary conclusions on the sensitivity of scatterometry with respect to the number and types of structural parameters to be retrieved, but also to the technique employed to gather the measurements.

Proceedings Article | 12 July 2002 Paper

Profile parameter accuracy determined from scatterometric measurements

Rayan Al-Assaad, Emmanuel Drege, Dale Byrne

Proceedings Volume 4692, (2002) https://doi.org/10.1117/12.475665

KEYWORDS: Reflectivity, Structural design, Scatter measurement, Error analysis, Scatterometry, Optical design, Critical dimension metrology, Wafer-level optics, Diffraction, Control systems

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