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A comparative electrical characterization study of aluminum oxide (Al2O3) deposited by thermal and plasma-assisted atomic layer depositions (ALDs) in a single reactor is presented. Capacitance and leakage current measurements show that the Al2O3 deposited by the plasma-assisted ALD shows excellent dielectric properties, such as better interfaces with silicon, lower oxide trap charges, higher tunnel barrier with aluminum electrode, and better dielectric permittivity (k = 8.8), than the thermal ALD Al2O3. Remarkably, the plasma-assisted ALD Al2O3 films exhibit niore negative fixed oxide charge density than the thermal ALD Al2O3 layers. In addition, it is shown that plasma-assisted ALD Al2O1 exhibits negligible trap-assisted (Poole-Frenkel) conduction unlike the thermal ALD Al2O3 films, resulting in higher breakdown electric-fields than the thermal ALD prepared films. [ABSTRACT FROM AUTHOR]

The deposition of Al2O3 by remote plasma atomic layer deposition (ALD) in the Oxford Instruments FlexAL reactor was studied and compared with results from thermal ALD in the same reactor. Trimethylaluminum [Al(CH3)3] was used as the metal precursor and O2 plasma and H2O were used as oxidizing agents for the plasma and thermal processes, respectively. For remote plasma ALD with a total cycle time of 4 s, the growth per cycle decreased monotonically with substrate temperature, from 1.7 Å/cycle at 25°C to 1.0 Å/cycle at 300°C. This growth per cycle was consistently higher than that obtained for thermal ALD. For the latter a maximum growth per cycle of ∼ 1.0 Å/cycle was found at 200°C. The film properties investigated were nearly independent of oxidant source for temperatures between 100 and 300°C, with a slightly higher mass density for the remote plasma ALD AI2O3 films. Films deposited at 200 and 300°C were stoichiometric with a mass density of 3.0 g/cm3 and low C (<1 atom %) and H (<3 atom %) contents. At lower substrate temperatures, oxygen-rich films were obtained with a lower mass density and higher H-content. Remote plasma ALD produced uniform AI2O3 films with nonuniformities of less than ±2% over 200 mm diam substrates. Excellent conformality was obtained for films deposited in macropores with an aspect ratio of ∼8 (2.0-2.5 μm diam). Preliminary results on electrical properties of remote plasma deposited films showed high dielectric constants of 7.8 and 8.9 for as-deposited and forming gas annealed AI2O3, respectively. [ABSTRACT FROM AUTHOR]

The Maxwell–Wagner effect, the enhanced charge migration to the interface of a stack of two dielectrics with different conductances, is shown to cause asymmetric leakage current and electrical breakdown behavior for different electrode polarities. For this purpose, metal-insulator-silicon capacitors were fabricated consisting of bilayered silicon dioxide–lanthanum zirconate dielectric stacks. Maxwell–Wagner instability and Debye polarization can be distinguished upon comparing electron injection from both sides of the stack. The Maxwell–Wagner charges have relaxation times that are nearly five orders of magnitude larger than the Debye polarization, suggesting the long-lasting influence of these trapped charges in nanolaminated dielectric systems. [ABSTRACT FROM AUTHOR]