Strain measurements by convergent-beam electron diffraction: The importance of stress relaxation in lamella preparations

Abstract

Local convergent-beam electron diffraction (CBED) patterns have been acquired on focus ion beam prepared samples in order to determine the strain field generated by a NiSi layer in a n-MOS transistor. A broadening of the high order Laue zone lines in the transmitted disk of CBED patterns is observed when approaching the NiSi∕Si interface. We show that this broadening is mainly due to the atomic plane bending that occurs as a result of the stress relaxation during the preparation of the thin lamella. From the analysis of this relaxation, we are able to determine the initial stress state of the bulk structure. The presented CBED procedure appears to be a promising tool to measure the strain and stress in any layer or structure deposited on a crystalline substrate.