ALD of Scandium Oxide from Scandium Tris(N,N[sup ʹ]-diisopropylacetamidinate) and Water

Abstract

Sc 2 O 3 films were deposited by atomic layer deposition ͑ALD͒ from a new precursor scandium tris͑N,NЈ-diisopropylacetamidinate͒ and water. The precursor is thermally stable ͑Ͼ350°C͒, volatile, with good reactivity to HF-last silicon. A growth rate of 0.3 Å/cycle was obtained at 290°C. The films were pure ͑C,N Ͻ 0.5 atom %͒ and had a refractive index of 1.8. Reactive ion etching tests on ALD scandia showed an etch rate 18 times slower than ALD hafnia. Electrical measurements showed a high permittivity of ϳ17, and a leakage current density of Ͻ3 ϫ 10 −3 A/cm 2 for an equivalent oxide thickness of 1.8 nm at 1.0 V.High-quality dielectric films are required in order to continue scaling down gate dimensions, capacitor footprints in dynamic random access memory ͑DRAM͒, and for optical applications. 1 Scandium oxide has been identified as a candidate material for these applications. Scandium oxide films also have properties that enable their use as damage-resistant antireflection multilayer coatings in high-power UV lasers, etch-stop layers in multilayer dielectric gratings and resist layers in electron beam lithography. 2,3 While etchstop and resist layers currently use hafnium oxide, reactive ion etching ͑RIE͒ on HfO 2 /SiO 2 multilayers causes fluorinated hafnium compounds to accumulate on SiO 2 walls, thereby reducing the laser damage threshold. On the contrary, Sc 2 O 3 /SiO 2 multilayers produce clean etches with no fluorinated Sc accumulation. Furthermore, etch rate selectivities for HfO 2 /Sc 2 O 3 were reported to be ϳ10:1, indicating that scandia films are potential candidates for replacing hafnia films in etch-stop and resist applications. 3 Along with these interesting physical characteristics, Sc 2 O 3 possesses electrical properties that are compatible with advanced microelectronic devices.To eliminate the high gate leakage experienced by ultrathin ͑Ͻ1.5 nm͒ films in metal oxide semiconductor field-effect transistor ͑MOSFET͒ devices it is necessary to incorporate higher dielectric constant materials. The current choices for replacing SiO 2 and SiO x N y in high performance transistors are HfO x 4 and HfO x N y . 5,6 Though the hafnium based insulators have promising characteristics, HfO x tends to crystallize at modest processing conditions. Crystallization of the dielectric layer can lead to increased leakage current densities due to impurity segregation to the grain boundaries. 4 Amorphous HfO x N y has been successfully deposited by atomic layer deposition ͑ALD͒, 7 but its crystallization after annealing has not been studied. One class of dielectrics that has been identified as having a high dielectric constant, high band offsets with respect to silicon, and high crystallization onset temperatures ͑Ͼ900°C͒ is the group of lanthanide ternary scandates, Ln x Sc y O 3 . 8 These compounds have been grown using physical vapor deposition techniques such as pulsed laser deposition ͑PLD͒ and molecular beam epitacy ͑MBE͒. 7,9 Developing an ALD process for the scandates is important for conformal coating over str...

TEM‐Based Metrology for HfO2 Layers and Nanotubes Formed in Anodic Aluminum Oxide Nanopore Structures

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Atomic layer deposition of aluminum oxide on hydrophobic and hydrophilic surfaces

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In Situ Infrared Characterization during Atomic Layer Deposition of Lanthanum Oxide

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