Strain characterisation of shallow trench isolation structures on a nanometer scale by convergent beam electron diffraction

The convergent beam electron diffraction (CBED) technique of transmission electron microscopy (TEM) has been applied to [110] cross-sections of shallow trench isolation structures in silicon, in order to evaluate the strain field distribution in 0.22 mum wide active areas. Different spot sizes (1 and 10 nm) and sample temperatures (room temperature with energy filtering, liquid nitrogen cooling without filtering) have been employed. It has been found that the regions of the active area closer than about 100 nm to the padoxide/substrate interface can be analysed only by using a 1 nm spot size. Moreover, the use of an energy filter to reduce the inelastic scattering improves the contrast of the diffraction lines in the CBED pattern, thus allowing the analysis to be performed at room temperature.