A new analysis strategy for CD metrology using rapid photo goniometry method

In the present paper, we use a new photo goniometric method capable to measure the entire diffracted pattern of a sub micron grating at fixed wavelength very rapidly. The complete reflectance pattern is obtained versus incidence angle (0-80°) and azimuth angle (0-360°). Regression software based on RCWA simulations has been developed. It is used to adjust automatically the grating profile with an unprecedented rapidity. Regressions have been applied to our polarimetric measurements versus incidence angle θ and versus azimuth angle φ. Results are compared to those provided by spectroscopic ellipsometry (SE) and scanning electron microscopy (SEM). We show that fixed incidence angle specular reflection coefficients versus azimuth angle R(φ) curves are very sensitive to the profiles especially when the CD is reduced mainly because of the occurrence of diffracted orders matching the CD at given azimuths even if the wavelength is much larger than the CD. Mid space illumination measurements in a large angular aperture (0<θ<80° and 0<φ<180°) can be also used to deduce profile information. We show that specular reflection coefficients can be fitted in the entire angular aperture to provide precise structural shapes. Out of specular contribution which is measured simultaneously can also be used in the analysis. We show that it is more sensitive to the grating imperfections than the specular contribution.