Mechanistic study of metalorganic chemical vapor deposition of (Ba,Sr)TiO3 thin films

Abstract

The metalorganic precursor chemistry was studied on Pt(111) surfaces in a O162 and O182 backgrounds. Using temperature programmed desorption (TPD) and static secondary ion mass spectrometry (SIMS). The precursor chemistry of Sr(thd)2 was found to be different on oxide covered Pt(111) surface as compared to the clean Pt(111) surface. In an oxygen ambient, TPD showed at least four different reaction processes which involved the removal of carbon from the precursor ligands on oxide covered Pt(111). In two of these, gas phase oxygen was incorporated into the oxidative products. In contrast, one carbon removing reaction was observed on the clean Pt(111) surface. Isotopic labeling experiments have also been carried out to understand the film-formation reactions in the metalorganic chemical vapor deposition of (Ba,Sr)TiO3 (BST) films. Time-of-flight SIMS and nuclear reaction analysis reveal that the oxygen in the BST films originates from both the gas phase oxidants (18O) and the precursor ligands (16O). The ligand substitution by gas phase O2 plays a more prominent role in the film formation at lower temperatures. On the other hand, the reactive oxygen radicals produced by microwave plasma involved more in breaking the O–C bonds than substituting the precursor ligands for the film formation. Use of the 50% O182–50% N2 16O2 mixture results in a reduction of O18 incorporation in the BST films, indicative of the direct involvement of N2O in the film-formation reactions. The mechanistic studies are essential for understanding the new BST precursors used in this study, and provide useful information to correlate the film microstructure, step coverage, and dielectric properties with the precursor properties.

Surface Chemical and Leakage Current Density Characteristics of Nanocrystalline Ag–Ba0.5Sr0.5TiO3 Thin Films

“…T he high‐permittivity (Ba,Sr)TiO 3 (BST) thin films have been intensively studied in recent years as a potential dielectric material for the development of capacitors in microwave devices and future ultra high‐density dynamic random access memories (DRAM) because of their low dielectric loss, high breakdown field strength, tunable dielectric constant, low leakage current density, and high reliability 1 . The present research interests in this class of high‐permittivity perovskite oxides are directed toward achieving improved performance of miniaturized BST capacitors by tuning the processing parameters, 2 reducing the leakage current density by suitable dopants, 3 fabricating composite or multilayer capacitors and superlattices with enhanced properties, 4 and adopting innovative procedures for the integration of high‐permittivity films directly on silicon (Si) 5 . Among the various factors that lead to high leakage current density in BST thin films, oxygen vacancy formation at the film/electrode interface has been identified as a major cause for current conduction and performance degradation of BST capacitors 6,7 .…”

Effect of (Ba+Sr/Ti) ratio on the dielectric properties for highly (111) oriented (Ba,Sr)TiO3 thin films

“…Although single-crystal substrates such as LaAlO 3 , MgO and SrTiO 3 have been adopted due to the good lattice match and low substrate dielectric loss, Si wafers have intrigued great interest in order to make multifaceted devices in the integrated microelectronics field [7][8][9]. Gao et al fabricated (0 0 1) BST film on platinized Si by metalorganic chemical vapor deposition and investigated a mechanistic study of MOCVD growth [10]. Padmini et al reported (0 0 1) texture BST film on platnized Si using RF magnetron sputtering and investigated the dielectric constant properties [11].…”

FABRICATION AND CHARACTERISTICS OF Pb DOPED BST FERROELECTRIC THIN FILMS FOR UNCOOLED INFRARED FOCAL PLANE ARRAYS

“…Figure 4(a) displays that the remnant polarization and coercive field of the films is 3.8 µCcm −2 , and 45 kVcm −1 respectively at 25 • C, and the films has high saturation of P − E hysteresis loop, and the nonlinear characteristics as good as that of the bulk BST films. We also found this P − E hysteresis loop slowly turns into a single straight line when the measurement temperature was raised from 25 • C to, which also indicates that the Tc of the films is diffuse below 35 • C. Similar phenomena have been observed in BST and BT films derived from MOCVD and RF magnetron sputtering [24]. Tahan et al attribute these phenomena to the effect of nanoscale grain size, as seen in the surface morphology [25].…”