Effect of Secondary Fluorescence in Thin‐Film Thickness on Compositional Determination Using Electron Probe Microanalysis

Unlike bulk analysis, thin film compositional analysis necessitates considering substrate effects, such as secondary fluorescence induced by x‐rays generated in the substrate and backscattered electrons. Several methods have been proposed to address these challenges. This study examines the influence of secondary fluorescence induced by characteristic x‐rays from the substrate on the film composition as determined by the method employed in JEOL's EPMA system. A CuAlO 2 film deposited on a Si substrate was selected as the representative specimen, given that the effect of secondary fluorescence induced by characteristic x‐rays of the Si substrate is substantial, due to the absorption edge energy of Al being slightly lower than that of the Si K α line. The findings reveal that the Si K α line generated from the Si substrate affected the generation of secondary Al K α fluorescence in the CuAlO 2 film when the film thickness was 200 nm or less. This interference can be mitigated through either depositing a 500 nm‐thick Au layer on the Si substrate or by depositing a CuAlO 2 film with a thickness exceeding 500 nm.