| AVS 57th International Symposium & Exhibition | |
| Spectroscopic Ellipsometry Focus Topic | Thursday Sessions |
| Session EL+AS+EM+MS+TF-ThA |
| Session: | Spectroscopic Ellipsometry |
| Presenter: | T. Novikova, LPICM, CNRS, Ecole Polytechnique, France |
| Authors: | T. Novikova, LPICM, CNRS, Ecole Polytechnique, France P. Bulkin, LPICM, CNRS, Ecole Polytechnique, France V. Popov, Moscow State University, Russia A. De Martino, LPICM, CNRS, Ecole Polytechnique, France |
| Correspondent: | Click to Email |
Mueller polarimetry in conical diffraction has proved to be a powerful optical technique for the metrological characterization of diffraction gratings. It was already shown that the shape of grating profile can be successfully reconstructed via appropriate optical modeling using full Mueller matrix measurements [1]. We also demonstrated that this approach can be of particular interest in microelectronics technology for the detection of overlay errors, which frequently result from the alignment deficiencies in lithography [2]. In some cases the asymmetrical distortion of grating profile can be induced by the etch process, or even be intentional, like in blazed gratings fabrication. For these applications a technique that allows for fast non-contact evaluation of the profile asymmetry may be of great value.
We studied the Mueller matrix spectra of symmetrical [3] and asymmetrical photoresist diffraction gratings on chromium using MM16 spectroscopic polarimeter, commercially produced by Horiba Jobin-Yvon, in the most general geometry of conical diffraction. At this configuration the 0th order cross-polarization complex reflection coefficients are antisymmetrical (r0sp = −r0ps) , provided that the grating is composed of only reciprocal materials and is invariant under the rotation by 180° about the normal incidence [4]. It leads to the following relations between the elements of 2x2 off-diagonal blocks of Mueller matrix: Mij = ±Mji.
The lack of rotational symmetry violates the electromagnetic reciprocity theorem for the 0th-order diffraction on the asymmetrical gratings and, consequently, breaks the symmetry of the off-diagonal blocks of Mueller matrix (|Mij | is not equal to |Mji|). This property of Mueller matrix of asymmetrical gratings was experimentally observed and numerically modeled at any illumination condition with exception of planar and pure conical mounting. We showed that the non-reciprocity in diffraction gratings can be used for the unambiguous detection of the grating profile asymmetry. The optimal choice of measurement configuration, i.e. azimuthal and polar angles considerably increases the sensitivity of the above mentioned technique.
References:
[1] T. Novikova, A. De Martino, S. Ben Hatit, and B. Drévillon, Appl. Opt. 45, 3688 (2006).
[2] T. Novikova, A. De Martino, R. Ossikovski and B. Drévillon, Europ. Phys. J. Appl. Phys. 31, 63 (2005).
[3] T. Novikova, A. De Martino, P. Bulkin, Q. Nguyen, B. Drévillon, V. Popov, and A. Chumakov, Opt. Express 15, 2033 (2007).