SrTa 2 O 6 thin films for high-K dielectric applications grown by chemical vapor deposition on different substrates

Abstract

SrTa 2 O 6 thin films with thickness between 6 and 150 nm were deposited by metal-organic chemical vapor deposition in a multiwafer planetary reactor. The monomolecular precursor, strontium-tantalum-͑methoxyethoxy͒-ethoxide, was dissolved in toluene and injected by a liquid delivery system. A rather narrow process window for the deposition of stoichiometric SrTa 2 O 6 was found for this precursor at low pressures and a susceptor temperature around 500°C. Films were grown on Pt/TiO 2 /SiO 2 /Si, TiN x /Si, and SiO 2 /Si substrates. The as-deposited films were x-ray amorphous and could be crystallized by postannealing at a temperature ജ700°C. The distorted tetragonal tungsten bronze phase of SrTa 2 O 6 was dominating within a broad range of compositions ͑Sr/Ta: 0.4-0.7͒ and a perovskite-type phase was additionally observed for Sr/TaϾ 0.7 and predominated for Sr/TaϾ 1. The electrical properties have been investigated with metal-insulator-metal and metal-insulator-semiconductor capacitors after sputter deposition of Pt top electrodes. The amorphous films had a dielectric constant K in the range of 35-45 and low leakage currents. For stoichiometric SrTa 2 O 6 the dielectric permittivity reached values of K = 100-110, but the leakage currents were increased. Remarkably, the permittivity is not very sensitive to deviations from the exact stoichiometry of the SrTa 2 O 6 phase ͑Sr/Ta: 0.4-0.7͒, but a decrease to values of K = 30-40 is observed along with the transition to the perovskite phase at high Sr contents.

Liquid-Injection MOCVD of ZrO2 Thin Films using Zirconium Bis(diethlyamido)-bis(di-tert-butylmalonato) as a Novel Precursor

“…The thermal properties of the precursor was evaluated using a Seiko TG7DTA 6300S11 instrument in an argon atmosphere (300 mL min -1 , ambient pressure, RT-500°C, heating rate of 5°C min -1 ). Thin-Film Deposition and Characterization: ZrO 2 films were deposited in an AIXTRON 2600G3 Planetary Reactor, which can handle five 6 in wafers simultaneously [22]. The newly developed precursor, [Zr(NEt 2 ) 2 (dbml) 2 ], was dissolved in n-butyl acetate in a 0.05 molar solution.…”

Crystal structure analysis of tungsten bronzes β-SrTa2O6 and β′-SrTa2O6 by synchrotron X-ray and neutron powder diffraction

“…We speculate that above results arose from the disorder of Sr (or Ba) over multiple energy-equivalent sites within the penta- which is not the case for b-, and a-forms. While SrTa 2 O 6 has been considered as a promising candidate for gate oxide applications owing to its high relative permittivity (k¼110) [4][5][6], the dependence of its dielectric behavior on polymorphism has not yet been addressed in either thin film or ceramic forms. We plan to conduct dielectric characterization of SrTa 2 O 6 in a further study.…”

“…As is common for complex oxides containing d 0 tantalum, niobium, or titanium, the above Sr m Ta 2n O m þ 5n compounds have been popular choices for exploring photocatalysts or dielectrics [2][3][4][5][6][7]. One particular member, SrTa 2 O 6 , is known to form in three polymorphs designated as a-, b-, and b 0 -phases [8,9], whereas the formation of a metastable defect perovskite Sr 1/2 TaO 3 [10] has been also reported.…”

Subthreshold behavior optimization of nanoscale Graded Channel Gate Stack Double Gate (GCGSDG) MOSFET using multi-objective genetic algorithms

“…Final optimized (GCGSDG) MOSFET parameters are summarized in Table 2, in which random device parameters are introduced to show the impact of the proposed approach on the improvement of the subthreshold behavior of (GCGSDG) MOSFET. As it is shown in Table 2, the obtained high-k dielectric material, for the optimized design, is the SrTa x O z alloy [11]. It is to note that the gate material used in our study is the n + -Polysilicon with the work function φ M = 4.2 eV, and all simulations were carried out in the subthreshold regime with V gs = 0.1 V and V ds = 0.1 V. Figure 5 shows the impact of our MOGAs-based approach on the subthreshold drain current behavior.…”