The dielectric properties of SrTiO 3 thin films deposited on SrRuO 3 seed layer were investigated. The SrTiO 3 thin films were deposited by plasma-enhanced atomic layer deposition using Sr͑C 11 H 19 O 2 ͒ 2 and Ti͑O i -C 3 H 7 ͒ 4 as precursors and O 2 plasma as an oxidant. The SrRuO 3 seed layer was formed through deposition of an SrO layer on a RuO 2 substrate and postannealing in O 2 ambient. As a result of introducing SrRuO 3 seed layers, the dielectric constant of 10 nm thick SrTiO 3 thin films increased to 83 compared with that of 16 and 50 for film deposited on Ru directly and seed formed on Ru substrate, respectively.Of the various high-k materials that are candidate capacitor dielectrics in next-generation dynamic random access memory ͑DRAM͒ devices, strontium titanate ͑SrTiO 3 ͒ has attracted interest due to its high dielectric constant ͑k bulk Ϸ 300͒ 1-4 with a paraelectric phase in the normal range of operating temperatures, high breakdown strength, 5 and good chemical stability. 6 For the application of SrTiO 3 films to the capacitor dielectric in DRAM devices, it is necessary to fabricate stoichiometric SrTiO 3 thin films with a thickness of around 10 nm with a suitable thickness and good compositional conformality. However, in an applicable thickness range for a DRAM capacitor, the dielectric constant of the SrTiO 3 thin film decreases abruptly when the thickness decreases due to inadequate crystallinity. 7-10 For enhancement of the dielectric properties of SrTiO 3 films, a strontium ruthenate ͑SRO͒ layer, which is formed by the deposition of an ultrathin SrO layer on Ru and postannealing in N 2 ambient, was introduced as a seed layer in our previous report. 11 As a conductive oxide material, SrRuO 3 has a pseudocubic perovskite structure with a lattice constant of 3.93 Å. Furthermore, the lattice mismatch between SrTiO 3 and SrRuO 3 is roughly 0.5% ͑whereas the lattice constant of perovskite SrTiO 3 is 3.91 Å͒. 12 The thin SRO layer can consequently act as a crystallization seed layer. However, it was hard to confirm the formation of the SrRuO 3 phase by X-ray diffraction ͑XRD͒ analysis, even if the dielectric properties of SrTiO 3 thin films were improved by the introduction of a SRO layer on a Ru substrate. Moreover, it was observed that the Sr-Ru-O layer that formed after annealing tends toward nonuniformity. If the RuO 2 layer is used as the substrate instead of Ru, a sufficient oxygen supply might be possible for the transformation of the deposited SrO to the SrRuO 3 layer ͑SrO + RuO 2 → SrRuO 3 ͒ and the O 2 ambient annealing could also be used instead of N 2 ambient annealing for the crystallization of SrTiO 3 thin films. Thus, in this paper, the SrRuO 3 is introduced as a crystallization seed layer formed by the deposition of a SrO layer on a RuO 2 substrate followed by O 2 annealing, instead of on a Ru substrate followed by N 2 annealing. The dielectric properties of SrTiO 3 thin films deposited on a seed layer are investigated in comparison with those deposited on Ru and on a seed layer ...
The dielectric properties of SrTiO3 thin films deposited on SrRuO3 seed layer was investigated. The SrTiO3 thin films were deposited by plasma enhanced atomic layer deposition using titanium tetra-isopropoxide and bis(dipivaloylmethanato) strontium as precursors and oxygen as an oxidant. The SrRuO3 seed layer was formed through deposition of ultra-thin SrO on RuO2 substrate and a post-annealing in O2 ambient. As the results of introducing SrRuO3 seed layer, the dielectric constants of SrTiO3 thin films were increased and the thickness dependency of dielectric properties was reduced compared with the SrTiO3 thin films deposited on Ru directly or seed formed on Ru substrate.
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