Lattice parameter measurement of sub-micron device structures in compound semiconductors via convergent-beam electron diffraction

Abstract

Convergent-beam electron diffraction (CBED), which is one of the techniques available on a modern transmission electron microscope (TEM), is sensitive to small localized lattice parameter changes and its application is therefore important in the characterization of sub-micron device structures. Unfortunately, dynamical diffraction effects prevent direct extraction of changes in the lattice parameter from CBED patterns which are obtained from high atomic number materials such as compound semiconductors. Therefore, in order to measure the relative lattice mismatch of a quaternary (InGaAsP) device structure grown on InP, we have opted to calibrate the relative position of CBED features with X-ray lattice parameter measurements which were obtained from planar quaternary layers grown on InP substrates. Three parameters from bright-field CBED patterns were measured as a function of the X-ray determined lattice mismatch in order to establish three separate calibration curves. CBED measurements taken from a device structure were found to produce similar values of lattice mismatch when interpreted using the calibration curves. The close correspondence of these three values of the lattice mismatch ((4.541 ± 2.119) × 10 −4, (5.158 ± 2.881) × 10 −1 and (4.819 ± 4.021) × 10 −4), enhances the credibility of this approach for the characterization of sub-micron device structures.