V.P. Korolkov, A.S. Konchenko, and R.K. Nasyrov (Russia)
Profilometry, calibration grating, step height standard
Novel method for spectrophotometric certification of calibration gratings is presented. It is exploits zero order grating diffraction efficiency dependence on wavelength. Measurement accuracy for this method is mainly defined by following main parameters – shifts of the spectra maximums that are occurred due to grooves sidewalls angle differs from 90°, uncertainty of grating angular positions, and spectrophotometer wavelength error. It is shown theoretically that gratings fabrication technology and measurement setup bring uncertainty in certification procedure in range of 0.25-1%. The method was preliminary tested on calibration gratings TGZ-11 and TGZ-03 with 1550 and 484 nm depth correspondingly. Definition of grating depth by offered method showed values lying in error range specified by the producer of gratings. Spectrophotometric certification can be made if grating depth is not less than 400nm. And maximal depth can be as large as 10μm for gratings with depth to period ratio in range of 1:5 - 1:10. Spectrophotometric certification of such deep gratings can be made in spectral range of 1-3μm.
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