Europhys. Lett, 46 (4), pp. 479-485 (1999)
Strain investigation of low strained buried gratings by
grazing incidence X-ray diffraction and elasticity theory
D. Lübbert 1, T. Baumbach 1, S. Ponti 1,
U. Pietsch 2, L. Leprince 3
J. Schneck 3 and A. Talneau 3
1 Fraunhofer-Institut für Zerstörungsfreie Prüfverfahren -
D-01326 Dresden, Germany
2 Institut für Festkörperphysik, Universität Potsdam - D-14469 Potsdam, Germany
3 France Télécom, CNET/DTD - BP 107, F-92225 Bagneux Cedex, France
(received 27 April 1998; accepted in final form 9 March 1999)
PACS. 61.10-i - X-ray diffraction and scattering.
PACS. 68.65+g - Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties.
PACS. 62.20Dc - Elasticity, elastic constants.
We investigate the strain evolution in low strained gratings before and after embedding in the substrate material by high-resolution grazing incidence X-ray diffraction and elasticity theory. For the experiments, we use a non-coplanar multiple crystal arrangement. A suitable selection of reflections allows us to characterise the grating shape independently of the strain state. Depth selective measurements give evidence for a non-uniform strain relaxation in the surface grating and a complete planarization of the sample surface by the burying process. In the buried grating a counteraction of the embedding material is found. The counteraction only leads to a partial restraining of the grating. There remains a laterally periodic strain modulation in the grating, which extends into the non-patterned material below and above the grating and reaches the free surface of the embedding material. The experimental findings are confirmed by calculations of the strain field based on elasticity theory. The subsequent simulations of the diffraction patterns show a good quantitative agreement with experiment.