In situ investigation by energy dispersive X-ray diffraction (EDXRD) of the growth of magnetron sputtered ITO films

Using the new analytical technique of in situ energy dispersive X-ray diffraction (EDXRD) during magnetron sputtering, the phase and structure formation in tin-doped indium oxide films (ITO) has been investigated. Due to the parallel data collection and the high X-ray flux of a synchrotron radiation source, the measurement time of an EDXRD spectrum was only approximately 30 s, allowing the collection of 10–20 spectra during a deposition run. From the fluorescence lines of indium and tin the film composition as well as the film thickness can be determined. Pattern, position and width of the diffraction lines are used to derive the phases, the mechanical stress and grain size of the growing films. By varying the oxygen flow at a fixed discharge power, the phase formation during the deposition of In1.8Sn0.2Ox with 0≤x≤3.5 films was investigated. At low oxygen flows the metallic indium phase dominates. With increasing oxygen flow the indium crystallites become much smaller accompanied by a steep increase of the In2O3 phase. At a certain oxygen flow the crystallite size of the In2O3 phase exhibits a maximum connected with the lowest compressive film strain. This favorable crystalline structure of the films leads to the lowest film resistivities. At very high oxygen flows the crystallites become smaller and show an increase in compressive strain.