Atomic Layer Deposition of SrTiO₃ Films with Cyclopentadienyl-Based Precursors for Metal–Insulator–Metal Capacitors

Abstract

The characteristics of the atomic layer deposition (ALD) of SrTiO3 (STO) films were examined for metal–insulator–metal capacitors, with Cp-based precursors Sr(iPr3Cp)2 and Cp*Ti(OMe)3 [Cp* = C5(CH3)5] employed as the Sr and Ti precursors, respectively. While the Sr precursor has a higher reactivity toward oxygen on the Ru substrate compared with another Ti precursor, with a 2,2,6,6-tetramethyl-3,5-heptanedionato ligand, which results in the highly Sr excessive STO film, the enhanced reactivity of the present Ti precursor suppressed the unwanted excessive incorporation of Sr into the film. A possible mechanism for the Sr overgrowth and retardation is suggested in detail. By controlling the subcycle ratio of SrO and TiO2 layers, stoichiometric STO could be obtained, even without employing a deleterious reaction barrier layer. This improved the attainable minimum equivalent oxide thickness of the Pt/STO/RuO2 capacitor to 0.43 nm, with acceptable leakage current density (∼8 × 10–8 A/cm2). This indicates an improvement of ∼25% in the capacitance density compared with previous work.

Atomic layer deposition of crystalline SrHfO3 directly on Ge (001) for high-k dielectric applications

“…Both the Sr and Hf metalorganic precursors are commercially available, reactive with water, and have been previously used for ALD. [38][39][40][41][42][43][44][45][46][47][48] Alternating subcycles of Sr and Hf are used to deposit stoichiometric to slightly Sr-rich (56%) films. During each subcycle the metalorganic is dosed for 2 s to ensure complete saturation of the surface, and subsequently purged for 15 s with ultrahigh purity Ar.…”

Asymmetry in electrical properties of Al‐doped TiO2 film with respect to bias voltage

“…1(f)). The decrease in the C value in small signal C-V measurement under the high DC bias is a common aspect of many higher k value materials, such as SrTiO 3 [8][9][10]. Therefore, the amount of shift in V max from zero point (ΔV max ) corresponded to the internal bias voltage which could be induced by different Schottky barrier height (SBH) at the TE and BE interfaces.…”

Impact of composition and crystallization behavior of atomic layer deposited strontium titanate films on the resistive switching of Pt/STO/TiN devices

“…The leakage current data of the 12 nm polycrystalline STO films at higher voltages are in reasonable agreement with results reported for high-k STO thin films. 15,31 Apparently, the leakage current for the stoichiometric STO films of 12 nm thickness was considerably reduced as compared with the 15 nm thick films (see Fig. 5(a)).…”

“…For the conformal growth on three dimensional (3D) structured devices with high integration density, chemical vapor deposition techniques 29,30 and, in particular, ALD techniques, 15,31,32 were utilized. Although the requirements on the aspect ratio of 3D structures for ReRAM applications are still moderate, the future of high-density ReRAM will also be defined by more challenging 3D topologies.…”

“…The surprisingly low resistance of the device from stoichiometric STO contradicts the findings reported by other groups. 15,31 This might be attributed to the formation of micro-cracks in the 15 nm thick annealed films which allow an enhanced current flow. The insulating behavior of the Sr-rich devices is in line with the regular dense morphology of the fine-grained films and with the slightly increased band gap found for the Sr-rich STO.…”