Determination of the Composition and Thickness of Thin Potassium Polyphosphide Films

An energy dispersive X-ray microprobe (EDX) analysis was developed to determine simultaneously the lateral uniformity of the thickness and the composition of thin potassium polyphosphide(KP x ) films. The EDX analysis was based on theoretical calibration curves generated by the Monte Carlo simulation approach developed by Kyser and Murata and extended by Miller and Koffman. Simultaneous determination of both composition and thickness was possible for this binary-element thin film due to the concentration independence of the theoretical intensity ratio of The EDX results were compared to macro techniques applied routinely in the characterization of thin films, i.e., piezoelectric thickness measurement and compositional analysis via X-ray fluorescence spectroscopy (XRF). A special XRF technique was developed to determine the weight ratios from fluorescent intensity measurements “directly” using “bulk” standards instead of thin film standards. The accuracy of this technique was demonstrated for an indium phosphide standard film since no certified KP x standard films are available. The comparison was carried out on films of widely different thicknesses (0.26–2.0 um) and compositions (KP 5 –KP 83 ). A Student's t test demonstrated that the compared techniques were identical at the 95% confidence level for the determinations of both thickness and composition. Thus, EDX analysis can be used to complement the macro techniques when the lateral uniformity of the thin films is to be determined at the micron scale.