Evanescent polarization-induced technique enables nanometer-scale imaging

March 1, 2007
Using a solid-immersion lens (SIL), which does not affect or contaminate the sample like liquid-immersion systems and also enables imaging at numerical-aperture (NA) values greater than 2, researchers in the College of Optical Sciences at theUniversity of Arizona (Tucson, AZ) have demonstrated an induced-polarization evanescent-imaging technique that achieves nanometer-scale vertical resolution and high lateral resolution over a relatively large field of view.

Using a solid-immersion lens (SIL), which does not affect or contaminate the sample like liquid-immersion systems and also enables imaging at numerical-aperture (NA) values greater than 2, researchers in the College of Optical Sciences at theUniversity of Arizona (Tucson, AZ) have demonstrated an induced-polarization evanescent-imaging technique that achieves nanometer-scale vertical resolution and high lateral resolution over a relatively large field of view.

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The flat side of the hemispherical SIL is placed just above the sample to be measured. The small gap height (less than the wavelength of the imaging light) enables contrast-enhanced evanescent coupling of the light between the SIL and the sample, inducing a polarization state at the pupil of the objective lens. This information is then imaged onto a CCD and analyzed using a vector plane-wave decomposition model to determine the physical dimensions of the sample under test. Experiments using a patterned silicon wafer and a known reference target with NA of 1.5 confirm a lateral resolution of approximately 175 nm (better than a conventional far-field microscope without scanning or immersion oil) and a height accuracy of ±2 nm in a 25 µm field of view. Contact Tom Milster at [email protected].

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