Atomic Layer Deposition and Electrical Properties of SrTiO[sub 3] Thin Films Grown Using Sr(C[sub 11]H[sub 19]O[sub 2])[sub 2], Ti(Oi-C[sub 3]H[sub 7])[sub 4], and H[sub 2]O

Abstract

Atomic layer deposited SrTinormalO3 (STO) thin films were grown using Sr(normalC11normalH19normalO2)2 and Ti(Oi-normalC3normalH7)4 with a remote plasma activated or thermal normalH2O vapor as oxidant at growth temperatures ranging from 190to270°C . The as-grown films were amorphous and showed a low effective dielectric constant of ∼20 with a low leakage current density ( <10−7A∕cm2 at 1V ). The chemical binding status of the Sr ions varied with the degree of crystallization of the STO film. A reasonable film growth rate and stoichiometric cation composition were obtained when the vaporization temperature of Sr-precursor was <200°C with the thermal normalH2O vapor. The low density of the as-grown film induced a large shrinkage in the film thickness which caused microcracking of the crystallized films during postannealing, even with the increased normalH2O supply. Adoption of thin (∼5nm) crystallized seed layer before the main layer STO growth improved the microstructure after the crystallization and the leakage current performance. As a result of the process optimization, the best electrical properties of an STO film grown on a Ru electrode were 0.45nm for the equivalent oxide thickness and 1×10−3A∕cm2 for the leakage current density at 1V .

Plasma-Assisted Atomic Layer Deposition of SrTiO3: Stoichiometry and Crystallinity Studied by Spectroscopic Ellipsometry

“…[15][16][17][18][19] The stoichiometry of the STO films strongly affects the crystallization temperature, crystalline microstructure after annealing and the dielectric constant. 20 Recent developments on ALD of STO showed that Sr-rich films have a smaller grain size after annealing resulting in lower leakage current values.…”

Process–property relationship in high-k ALD SrTiO3 and BaTiO3: a review

“…Hwang and coworkers used a 5 nm thick STO seed layer annealed at 650 1C for 1 min with RTA, which resulted in an improvement in the capacitance (2.7 mF cm À2 without a seed layer vs. 4.5 mF cm À2 with a seed layer) and a decrease in the J G (10 À1 A cm À2 without a seed layer vs. 10 À5 A cm À2 with a seed layer at 1 V) of the main STO layer. 86 They also reported a 3 nm thick STO seed layer annealed at 600-750 1C for 1 min with RTA. The capacitance of a 17 nm thick main STO layer significantly increased by a factor of 5.…”

“…In this section, we review characterization strategies that researchers have pursued to understand the morphology of thin-film perovskites and how they linked their findings to the obtained properties (Table 5). 15,46,[64][65][66]70,72,[76][77][78][79][80][81]83,[85][86][87]90,94,97,98,102,[104][105][106] To obtain compositional information, XPS is the most common technique. The information that can be obtained ranges from film contamination to the elemental composition within the topmost 1-10 nm of the film and its uniformity, chemical and electronic states, binding information, and depth information.…”

“…However, the correctness of the optical model for multicomponent films usually requires validation by means of cross-sectional transmission electron microscopy (TEM) and TEM-Energy dispersive spectroscopy (EDS). 83,86,87 For non-planar substrates, TEM-EDS and TEM elemental energy loss spectroscopy (TEM-EELS) are emerging approaches to measure the thickness and compositional step coverage. The Hwang group of Seoul National University used TEM-EDS to investigate cross-sectional images of a SiO 2 high-aspect-ratio structure with a B100 nm diameter opening and a depth of B1 mm coated with B8-9.5 nm thick ALD STO.…”

Stoichiometry variation for the atomic layer deposition of SrxTiyOz from Sr(iPr3Cp)2, Ti[N(CH3)2]4 and H2O

“…There are several reports on the growth of STO films by ALD from different volatile metal organic precursors at home built ALD systems [10,[12][13][14]. Whereas a broad variety of Ti precursors is available, for the ALD of the TiO 2 half cycle of strontium titanate, mainly precursors based on alkoxides and mixed alkoxides-diketonates like Ti( i OMe) 4 [15,16], Ti( i OPr) 4 [13,14] or Ti( i OPr) 2 (thd) 2 [17] are mentioned in the literature. Just recently, also cyclopentadienyl (Cp) based precursors like Cp*Ti(OMe) 3 [18] and (CpMe 5 )Ti(OMe) 3 [19] are described for the ALD of SrTiO 3 .…”