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Applied Optics

Applied Optics


  • Vol. 42, Iss. 16 — Jun. 1, 2003
  • pp: 3234–3240

Optical measurement of depth and duty cycle for binary diffraction gratings with subwavelength features

John R. Marciante, Nestor O. Farmiga, Jeffrey I. Hirsh, Michelle S. Evans, and Hieu T. Ta  »View Author Affiliations

Applied Optics, Vol. 42, Issue 16, pp. 3234-3240 (2003)

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We describe a new and unique method for simultaneous determination of the groove depth and duty cycle of binary diffraction gratings. For a near-normal angle of incidence, the +1 and -1 diffracted orders will behave nearly the same as the duty cycle is varied for a fixed grating depth. The difference in their behavior, quantified as the ratio of their respective diffraction efficiencies, is compared to a look-up table generated by rigorous coupled-wave theory, and the duty cycle of the grating is thus obtained as a function of grating depth. Performing the same analysis for the orthogonal probe-light polarization results in a different functional dependence of the duty cycle on the grating depth. By use of both TE and TM polarizations, the depth and duty cycle for the grating are obtained by the intersection of the functions generated by the individual polarizations. These measurements can also be used to assess qualitatively both the uniformity of the grating and the symmetry of the grating profile. Comparison with scanning electron microscope images shows excellent agreement. This method is advantageous since it can be carried out rapidly, is accurate and repeatable, does not damage the sample, and uses low-cost, commonly available equipment. Since this method consists of only four fixed simple measurements, it is highly suitable for quality control in a manufacturing environment.

© 2003 Optical Society of America

OCIS Codes
(050.1950) Diffraction and gratings : Diffraction gratings
(050.2770) Diffraction and gratings : Gratings
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(120.3940) Instrumentation, measurement, and metrology : Metrology
(220.4000) Optical design and fabrication : Microstructure fabrication

Original Manuscript: October 14, 2002
Revised Manuscript: February 20, 2003
Published: June 1, 2003

John R. Marciante, Nestor O. Farmiga, Jeffrey I. Hirsh, Michelle S. Evans, and Hieu T. Ta, "Optical measurement of depth and duty cycle for binary diffraction gratings with subwavelength features," Appl. Opt. 42, 3234-3240 (2003)

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