X-ray diffraction studies of thin films and multilayer structures

Characterization ofAIIIBVsuperlattices by means of synchrotron diffraction topography and high-resolution X-ray diffraction

New possibilities are presented for the characterization ofAIIIBVmixed superlattice compounds by the complementary use of synchrotron diffraction topography and rocking curves. In particular, using a synchrotron white beam and the section diffraction pattern of a 5 µm slit taken at a 10 cm film-to-crystal distance, it was possible to reproduce a set of stripes corresponding to interference fringes. These are analogous to the interference maxima revealed in high-resolution rocking curves, but are created by the changes in orientation of the planes inclined to the surface which are induced by unrelaxed strain. The section diffraction topographic method enabled examination of the sample homogeneity along the narrow intersecting beam. This was important in the case of the present sample containing a twin lamella in the InP substrate wafer. Both the section and projection Bragg case topographic methods enabled the crystallographic identification of the twin lamella. Another characteristic feature indicated in the section topography was the bending of the stripes corresponding to the superlattice peaks close to the boundaries of the twin lamella. The most probable interpretation of this phenomenon is an increase in the thickness of the deposited layers close to the lamella, together with possible changes in the chemical composition, leading to a decrease in the mean lattice parameter in the superlattice.

High-temperature residual stresses in thin films characterized by x-ray diffraction substrate curvature method

A new x-ray technique to determine temperature dependencies of macroscopic stresses in thin films by characterizing the substrate curvature is introduced. The technique is demonstrated on polycrystalline TiN and Al thin films deposited on Si(100) wafers. The structures are thermally cycled in the temperature range of 25-400 degrees C using a newly developed heating chamber attached to a commercial x-ray diffractometer. The curvature of the freestanding samples was determined by the rocking curve measurement of substrate Si 400 reflections at different lateral positions of the samples, and the stresses are calculated using Stoney's formula. The results show that the magnitude of the stress is in good agreement with the results obtained by other techniques. For the practical application of the technique, the sample mounting and the temperature control are of great importance.