Accurate Texture Measurements On Thin Films Using A Powder X-Ray Diffractometer

Mark D. Vaudin

A fast and accurate method that uses a conventional powder x-ray diffractometer has been developed for measuring crystalline texture. A theta-two theta scan of a Bragg peak from the textured planes is collected and also a omega scan, or rocking curve, using the same Bragg peak. The method has important advantages over other techniques: a large x-ray footprint can be used, thus obtaining significantly higher intensity which is particularly significant for thin films; no randomly textured specimen is required. The large footprint leads to considerable tilt-induced defocussing during the theta scan Ð the scattering angle varies along the iradiated length of the specimen as it is tilted out of the symmetric position. To obtain an accurate texture profile from the theta scan, corrections for defocussing and absorption must be applied, and the theta-two theta scan of the Bragg peak, which gives the variation of scattered intensity with angle, is used for the defocussing correction. First principles calculations are used to correct for absorption, with the film thickness and x-ray absorption coefficient as parameters. The technique has been applied to several classes of technologically important materials used in thin film form, such as films of electroplated copper for advanced metallization, and also BST films down to 26 nm thick, which are candidates for DRAM applications.