Structural-Dielectric Property Relation From Compositional Tuning of ALD Deposited Yttrium-Stabilized Hafnium Oxide Films

Abstract:

Sequential Atomic Layer Deposition has been used to deposit yttrium-doped hafnium (YDH) oxide films with variable yttrium content using a new yttrium precursor, tris(ethylcyclopentadienyl) yttrium, and tetrakis(diethylamino) hafnium, with water vapor as the oxidizer. The resulting films were analyzed in terms of structural and electrical properties after different post-deposition annealing conditions in order to assess composition-structure-dielectric property relationships. The as-deposited and annealed film structures were investigated using grazing incidence x-ray diffraction and cross-sectional transmission electron microscopy to obtain structural information in terms of both lattice crystalline structure and estimated polycrystalline grain size. The electrical properties were observed by performing capacitance-voltage and current-voltage measurements. The presence of yttrium in HfO2 affects post-annealed structural and electrical properties in a manner consistent with density functional theory; however, YDH compositional dependence is different for structural and electrical properties. Whereas variable yttrium content from 2.5 – 20% after post annealing above at least 600 ºC for 5 minutes, yielded the same basic polycrystalline cubic HfO2 structure with similar average grain size, there was a continuously variable compositional effect with yttria content on the dielectric constant which maximized at ~ 14% yttrium content in HfO2. All the films have a low leakage current density of below 10-5 A/cm2 at bias voltage of 1 V.