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 θ - 2θscan of a Bragg peak from the textured planes is collected and also a θ 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 defocusing during the scan - the scattering angle varies along the irradiated length of the specimen as it is tilted out of the symmetric position. To obtain an accurate texture profile from the θ scan, corrections for defocusing and absorption must be applied, and the θ - 2θ scan of the Bragg peak, which gives the variation of scattered intensity with angle, is used for the defocusing correction. First principles calculations, with the film thickness and x-ray absorption coefficient as parameters, are used to correct for ab-sorp-tion. The technique has been applied to several classes of technologically important materials used in thin film form, including electronic materials such as films of electroplated copper for advanced metallization, and also BST films down to 26 nm thick, which are candidates for DRAM applications.