Atomic layer deposition of oxides for microelectronics

Description

Atomic layer deposition of high-κ oxides has gained interest due to the wide applications in microelectronics. For gate dielectric application, amorphous oxides are preferred for the structural uniformity at nanometer scale. La x M 2- x O 3 (M = Sc, Lu or Y) films were deposited by ALD with metal amidinate precursors and H 2 O. Both LaScO 3 and LaLuO 3 films are amorphous and free of interfacial layers. Besides the structural benefits, both oxides have high dielectric constants (∼23 for LaScO 3 and 28 ± 1 for LaLuO 3 ), low leakage current density, and very few bulk traps, and are scalable to EOT < 1 nm. La 1.23 Y 0.77 O 3 films have polycrystalline structures with moderately high κ ∼ 17 and low leakage current. The Poole-Frenkel mechanism is verified in the ternary oxide films by studying temperature dependence of the leakage current. For La 1.1 Al 0.9 O 3 /Si, the thermal stability was evaluated by studying the interface structure evolution under different annealing conditions. It concludes that an interfacial layer forms at the temperature above 600°C and the oxygen source resides in the film. For DRAM application, ALD deposition of rutile phase TiO 2 is developed for its 70. The substrate, SnO 2 and RuO 2 /Ru, works as both bottom electrodes and templates for rutile TiO 2 nucleation. The growth rate is ∼ 0.3 Å/cycle and is regardless of phases and crystallinity. The crystallinity strongly depends on the substrates. High quality ruthenium thin films were deposited by ALD with bis( N,N '-di- tert -butylacetamidinato) ruthenium(II) dicarbonyl and O 2 . The film crystallinity, density, and resistivity strongly depend on the O 2 exposure. As E O [approximate] E max , the films have the lowest resistivity, highest density and best crystallinity ( ∼10 μΩ·cm, ∼12.3 g/cm 3 and grain size comparable to film thickness). When E O > E max , films peel off from the substrate due to the recombinative desorption of O 2 . The impurities are mainly O (0.27±0.03at.%) and C (0.30±0.05at.%). The C is mostly segregated along grain boundaries, which are less dense than the grain interiors.

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