(Ba,Sr)TiO 3 thin films with conducting perovskite electrodes for dynamic random access memory applications

Abstract

Interfaces and hence electrodes determine the performance of (Ba,Sr)TiO3 (BST) capacitors for ultralarge scale integration dynamic random access memories. Electrode materials forming a rectifying contact on BST drastically reduce the dielectric constant and hence the capacitance and charge storage density of the capacitor, when the dielectric thickness is reduced. This can limit the role of Pt as an electrode material for gigabit dynamic random access memories (DRAM). The conducting oxide, La0.5Sr0.5CoO3 (LSCO) with its perovskite structure, has structural and chemical compatibility with BST. Our results in LSCO/BST/LSCO capacitor show that the mechanism of conduction is not interface limited but predominantly bulk limited. A 75 nm BST film with LSCO electrodes shows a leakage current density of 1×10−7 A/cm2 at 1 V, 85 °C. The dielectric constant at 1 V, 105 Hz is 350, making LSCO a potential contact electrode for DRAM memories.

Microstructure of La0.7Sr0.3MnO3/Ba0.7Sr0.3TiO3/La0.7Sr0.3MnO3 epitaxial films grown on (001) SrTiO3 substrate

“…So far, several different conducting oxides, e.g. YBa 2 Cu 3 O 7-d , SrRuO 3 , (La x ,Sr 1Àx )CoO 3 and (La x ,Sr 1Àx )MnO 3 , etc., are proved to be suitable electrodes in epitaxial heterostructures with BST layers and have been used extensively [6][7][8][9]. High-quality films grown on each other are easily obtained for those perovskitetype conducting oxides and ferroelectric layers because of their similar structures and small mismatches in lattice parameters.…”

High tunability of pulsed laser deposited Ba0.7Sr0.3TiO3 thin films on perovskite oxide electrode

“…The leakage current density of BST thin film capacitor with LSCO electrode is found to be 200 nA/cm 2 at a bias voltage of 2 V for 800 nm thick BST film. The low leakage current density of the capacitor with LSCO electrode makes it a potential candidate for gigabit density memories [41].…”

Modified space-charge-limited current behavior in pulsed laser deposited (Ba,Sr)TiO3 thin films

“…Such materials include a large group of electro-ceramic materials comprising dielectrics, ferroelectrics, and piezoelectrics [1][2][3]. An example is (Ba,Sr)TiO 3 which possesses great potential for applications, in especially as high-permittivity dielectrics in micro-electronics or nonvolatile memory devices [4,5]. Researches on the structures and properties of these materials have shown that the shallow traps introduced by oxygen vacancies sensitively control material properties and device performance [6].…”