A comparative study on atomic layer deposited oxide film morphology and their electrical breakdown

Abstract

Transition metal oxide films HfO2, ZrO2, Ta2O5, TiO2, Nb2O5, and Y2O3, together with Al2O3 and SiO2 for reference, were deposited by atomic layer deposition (ALD) and investigated. For all the films ALD process was performed within the same reactor at two temperature ranges 100–125∘C and 250–300∘C. Both water and ozone were used as oxygen sources if processes were available. Most films are amorphous as-deposited, but HfO2, ZrO2, and Y2O3 can be crystalline, depending on deposition temperature and oxygen source.After deposition and initial characterization, the films were annealed to different temperatures up to 1200∘C, depending on the material, to observe the crystallization process.When crystalline phases were observed, grain sizes have been derived from the X-ray diffractograms and compared with feature sizes in SEM images. RMS analysis revealed a general tendency - an increase of roughness with the appearance of crystallization.The temperature-dependent morphological investigations were supported by breakdown field measurements. Those are also strongly affected when a film becomes crystalline. Most values observed for break down fields agree with literature, some values exceed previously reported numbers.