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atomic layer deposition rare earth oxides structure morphology electrical properties oxide thin-films chemical-vapor-deposition rare-earth-oxides precursors ceramics
Abstract:
Gd2O3 and Dy2O3 thin films were grown by atomic layer deposition (ALD) on Si(100) substrates using the homoleptic rare earth guanidinate based precursors, namely, tris(N,N'-diisopropy1-2-dimethylamido-guanidinato) gadolinium (III) [Gd(DPDMG)(3)] (1) and tris (N,N'-diisopropyl-2-dimethylamido-guanidinato)dysprosium (III) [Dy(DPDMG)(3)] (2), respectively. Both complexes are volatile and exhibit high reactivity and good thermal stability, which are ideal characteristics of a good ALD precursor. Thin Gd2O3 and Dy2O3 layers were grown by ALD, where the precursors were used in combination with water as a reactant at reduced pressure at the substrate temperature ranging from 150 degrees C to 350 degrees C. A constant growth per cycle (GPC) of 1.1 angstrom was obtained at deposition temperatures between 175 and 275 degrees C for Gd2O3, and in the case of Dy2O3, a GPC of 1.0 angstrom was obtained at 200-275 degrees C. The self-limiting ALD growth characteristics and the saturation behavior of the precursors were confirmed at substrate temperatures of 225 and 250 degrees C within the ALD window for both Gd2O3 and Dy2O3. Thin films were structurally characterized by grazing incidence X-ray diffraction (GI-XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) analyses for crystallinity and morphology. The chemical composition of the layer was examined by Rutherford backscattering (RBS) analysis and Auger electron spectroscopy (AES) depth profile measurements. The electrical properties of the ALD grown layers were analyzed by capacitance voltage (C-V) and current-voltage (I-V) measurements. Upon subjection to a forming gas treatment, the ALD grown layers show promising dielectric behavior, with no hysteresis and reduced interface trap densities, thus revealing the potential of these layers as high-k oxide for application in complementary metal oxide semiconductor based devices.
