A half-wave method of measurement of wafer birefringence that is based on interference fringes recorded from a uniaxial wafer by use of a standard phase-modulated spectroscopic ellipsometer is investigated. The birefringence of uniaxial wafers is calculated from the extremal points in the recorded oscillating intensities. A formalism is developed to incorporate the change in birefringence with wavelength as a correction factor. The correction explains the overestimation of the birefringence from previous similar research on thick uniaxial sapphire substrates. The enhanced derivative of the birefringence that is due to polarization-dependent intraconduction band transitions is detected. Furthermore, for well-characterized wafers it is shown that this method can be used in wafer-thickness mapping of 4H-SiC and similar uniaxial high-bandgap semiconductors.
© 2000 Optical Society of America
[Optical Society of America ]
(160.1190) Materials : Anisotropic optical materials
(260.1180) Physical optics : Crystal optics
(260.2130) Physical optics : Ellipsometry and polarimetry
(260.5430) Physical optics : Polarization
M. Kildemo, M. Mooney, C. Sudre, and P. V. Kelly, "Investigation of a Half-Wave Method for Birefringence or Thickness Measurements of a Thick, Semitransparent, Uniaxial, Anisotropic Substrate by Use of Spectroscopic Ellipsometry," Appl. Opt. 39, 4649-4657 (2000)