Epitaxial growth of high-k BaxSr1−xTiO3 thin films on SrTiO3 (001) substrates by atomic layer deposition

Abstract

Atomic layer deposition (ALD) offers a viable route for the growth of thin and conformal films over 3D topographies and is becoming attractive as a method to grow films thin enough, and with sufficient dielectric constants (k), for the fabrication of next-generation dynamic random memories. The authors used ALD to grow thin (≤15 nm) BaxSr1 − xTiO3 (BST) films that are epitaxially integrated to SrTiO3 (001) (STO) and Nb-doped SrTiO3 (001) (Nb:STO). Films of three compositions, which are x ∼ 0.7, 0.5, and 0.3, and thicknesses of 7.8–14.9 nm were grown at 1.05 Torr and 225 °C using barium bis(triisopropylcyclopentadienyl), strontium bis(triisopropylcyclopentadienyl), titanium tetraisopropoxide, and H2O. Film compositions were controlled by changing cycle ratios (Ba:Sr, Ba:Ti, and Sr:Ti) and confirmed by in situ x-ray photoelectron spectroscopy. Films were amorphous as-deposited and required postdeposition vacuum annealing at 650–710 °C to crystallize. Epitaxy was confirmed with x-ray diffraction and transmission electron microscopy. Only BST (00l) out-of-plane diffraction signals were detected. Capacitance-voltage (C-V) measurements revealed that BST thin films grown by ALD have dielectric constant values ranging from 210 for Ba0.71Sr0.26TiO3 to 368 for Ba0.48Sr0.43TiO3.

Achieving High Dielectric Constants in Tetragonal Single‐Phase ZrHfO2 Thin Films through the Atomic Layer Deposition Process Using a Mixed Precursor

“…Rutile TiO 2 ( k ≈ 100) and SrTiO 3 ( k ≈ 150) have been extensively studied as high‐ k dielectric materials. [ 12–20 ] However, numerous issues need to be overcome. These materials have a small bandgap ( E g of approximately 3.0–3.2 eV), which results in high leakage current and necessitates the development of new electrode materials to replace TiN, which is mainly used as the electrode material.…”

Enhanced Piezoresponse and Dielectric Properties for Ba1-XSrXTiO3 Composition Ultrathin Films by the High-Throughput Method

“…Costa et al have prepared Ba 1-x Sr x TiO 3 films by the conventional solid reaction method [12]. Le et al have grown Ba 1-x Sr x TiO 3 films using the atomic layer deposition technique (ALD) [13]. However, the conventional methods only focus on fabricating BSTO thin films with a single Ba/Sr ratio [14,15].…”

Composition and annealing effects on the linear electro‐optic response of solution‐deposited barium strontium titanate

“…BST thin films have been deposited by a wide range of vacuum‐based techniques such as molecular beam epitaxy (MBE), 10 RF sputtering, 7 pulsed laser deposition, 11 and chemical vapor deposition 12 . Atomic layer deposition has also shown promise in producing ultra‐thin BTO and BST films with relatively high dielectric response 13‐17 . A number of chemical solution methods have also been explored, 18‐21 and these methods offer some advantages over their vacuum‐based counterparts, such as relaxed equipment requirements and improved scalability.…”

“…12 Atomic layer deposition has also shown promise in producing ultra-thin BTO and BST films with relatively high dielectric response. [13][14][15][16][17] A number of chemical solution methods have also been explored, [18][19][20][21] and these methods offer some advantages over their vacuum-based counterparts, such as relaxed equipment requirements and improved scalability.…”