Investigation of strain distribution in LOCOS structures by dynamical simulation of LACBED patterns

Large-angle convergent beam electron diffraction (LACBED) dynamical simulations have been applied to the investigation of the strain distribution in the silicon region underlying a local oxidation of silicon (LOCOS) structure. This distribution is revealed through the modification of the profile of the (0 0 8) Bragg contour in the [1 2 0] projection of a [1 1 0] TEM cross-sectioned structure. If one assumes a strain field independent on the direction normal to the cross section, a contrast in the LACBED pattern is obtained only if a rotation of the lattice planes in the silicon region under stress is taken into account. The experimental patterns, taken on a submicron recessed-LOCOS, are in fair agreement with those calculated assuming, for the strain field, an analytical model based on the planar stress approximation [J. Vanhellemont, Ph.D. Thesis, University of Antwerp, 1990; I. De Wolf, J. Vanhellemont, A. Romano-Rodrı̀guez, H. Norström, H.E. Maes, J. Appl. Phys. 71 (1992) 898].