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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Vol. 37, Iss. 22 — Aug. 1, 1998
  • pp: 5116–5125

Determining the optical constants of read-write sliders during flying-height testing

Peter de Groot, Ara Dergevorkian, Tod Erickson, and Russell Pavlat  »View Author Affiliations


Applied Optics, Vol. 37, Issue 22, pp. 5116-5125 (1998)
http://dx.doi.org/10.1364/AO.37.005116


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Abstract

Flying-height testers for rigid disk drives employ a transparent glass substrate in place of the magnetic disk and use optical interferometry to measure the flight properties of the read-write slider. Because of the material phase change on reflection, the effective optical constants n and k of the slider play an important role in the measurement. We describe an instrument that determines the optical constants simultaneously with flying height, using polarization interferometry. This in situ analysis of n and k obviates the need for independent ellipsometry, while avoiding the problematic retract calibration characteristic of traditional flying-height test equipment. The rms uncertainty for n and k are 0.04, resulting in height uncertainties that range from 3 nm for 250-nm flying heights down to 0.5 nm at contact. We verify these results by use of a variety of experimental techniques on both laboratory samples and actual read-write sliders.

© 1998 Optical Society of America

OCIS Codes
(120.2130) Instrumentation, measurement, and metrology : Ellipsometry and polarimetry
(120.2830) Instrumentation, measurement, and metrology : Height measurements
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.4530) Instrumentation, measurement, and metrology : Optical constants
(120.4640) Instrumentation, measurement, and metrology : Optical instruments
(120.5410) Instrumentation, measurement, and metrology : Polarimetry

History
Original Manuscript: November 5, 1997
Revised Manuscript: March 31, 1998
Published: August 1, 1998

Citation
Peter de Groot, Ara Dergevorkian, Tod Erickson, and Russell Pavlat, "Determining the optical constants of read-write sliders during flying-height testing," Appl. Opt. 37, 5116-5125 (1998)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-37-22-5116


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References

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  11. The calculations for Table 1 also appear in the paper “Interferometric measurement of disk/slider spacing: the effect of phase shift on reflection,” by C. Lacey, R. Shelor, A. Cormier, R. E. TalkeIEEE Trans. Magn. MAG-29, 3906–3910 (1993).
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  13. Following Born and Wolf, we prefer to use the n + ik definition of the complex index, rather than the more common n - ik.
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  19. Generally, it is not possible to calculate a film thickness as well as the optical constants from a single ellipsometric measurement; hence the need for three or more flying heights for proper n and k calibration. See, for example, R. M. A. Azzam, N. M. Bashara, Ellipsometry and Polarized Light (Elsevier, Amsterdam, 1987), p. 317.
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  34. P. de Groot, J. Biegen, L. Deck, R. Smythe, “Calibration standard for optical gap measuring tools,” U.S. patent5,724,134 (3March1998).
  35. A similar arrangement for establishing known gaps for calibration appears in U.S. patent5,220,408 to M. Mager, entitled “Method and apparatus for calibration of optical flying-height testers” (15June1993).
  36. Our technique does require an estimated value for the scattered light loss, in the form of the μ factor. However, the effect of an incorrect μ on the ZSE is small. It serves primarily to simplify comparison of our technique with traditional ellipsometry.

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