Microstructural analysis of integrated pin-shaped two-dimensional and three-dimensional ferroelectric capacitors from micro-focused synchrotron X-ray techniques

Future development of ferroelectric random access memory requires the integration of three-dimensional ferroelectric capacitors (FeCAP) in a microelectronic architecture. In this paper, pin-shaped two-dimensional and three-dimensional Sr_0.8Bi_2.2Ta₂O₉-based FeCAP arrays were characterized using an original approach combining micro-focused synchrotron X-ray fluorescence and diffraction. From a modelling approach, dimensional, chemical and microstructural details were extracted over a series of capacitor arrays. Hence, these techniques proved insightful for a non-destructive benchmarking approach. In addition, for all investigated capacitor geometries, the micro-fluorescence experiments evidenced a well controlled chemical composition within the FeCAP arrays, attesting the stability of the elaboration and integration steps. Nevertheless, micro-diffraction experiments have indicated a lower control of the ferroelectric film crystallographic orientation from one capacitor to the next, despite a well defined chemical composition. This feature was attributed to the presence of patterned bottom electrodes, bringing to light the role of the slanted capacitor sidewalls in the three-dimensional geometry and partially explaining the non-optimized electrical polarization usually measured in three-dimensional capacitors with respect to planar geometry.