Thermal and Plasma-Enhanced Atomic Layer Deposition of TiN Using TDMAT and NH 3 on Particles Agitated in a Rotary Reactor Delphine Longrie,* ,† Davy Deduytsche, † Jo Haemers, † Philippe F. Smet, ‡ Kris Driesen, § and Christophe Detavernier* ,† † CoCooN and ‡ LumiLab, Department of Solid State Sciences, Ghent University, 9000 Gent, Belgium § Umicore, 2250 Olen, Belgium ABSTRACT: Titanium nitride (TiN) shows metallic-type elec- trical behavior and is therefore an interesting material to improve the conductivity of a wide variety of powders. Atomic layer deposition (ALD) is an excellent technique for achieving the desired ultrathin but conformal coatings. To conformally coat large amounts of particles using ALD, agitation of the particles and efficient reactant usage are necessary. Thermal and plasma- enhanced ALD growth of TiN using tetrakis(dimethylamino) titanium (TDMAT) and NH 3 as precursors on agitated particles was performed using a rotary reactor to deposit TiN on ZnO submicrometer powder. The NH 3 plasma pulse was monitored using in situ mass spectrometry (MS) and optical emission spectroscopy (OES) measurements to gain insight into the reaction mechanism of the plasma-enhanced process. X-ray photoelectron spectroscopy (XPS) and powder resistivity measurements were performed to determine the influence of the deposition process on the composition and conductivity of the deposited TiN layers. KEYWORDS: atomic layer deposition, plasma-enhanced ALD, titanium nitride, rotary reactor, particle coating, optical emission spectroscopy 1. INTRODUCTION Titanium nitride (TiN) is already used in microelectronics as a conductive barrier between the device and the metal contacts that operate it. The TiN films block the diffusion of metal atoms from the contact into the silicon, while still being conductive enough to provide a good electrical connection. 1 In the 45 nm chip design technology, TiN is even used as a metal material that increases transistor performance when used in combination with high permittivity gate dielectrics. However, applications for ultrathin TiN layers are not limited to electronics alone since thin TiN films could also prove useful for various powder applications, e.g., enhancing the con- ductivity of lithium titanate spinel (LTS) powder for use in lithium-ion batteries. 2 Atomic layer deposition (ALD) is a thin film deposition technique that is able to deposit ultrathin, uniform, and conformal layers. The ALD process, consisting of two sequential, self-limiting surface chemical reactions, has been shown to provide the desired coating in a variety of systems on planar substrates and into high-aspect-ratio structures. 3-7 More recently, ALD on powders has gained in interest leading to the deposition of oxides (Al 2 O 3 , SiO 2 , TiO 2 , SnO 2 , Fe 2 O 3 , ZnO, CoO), nitrides (AlN, BN), phosphates (TiPO 4 ), and metals (Pt, Pd) on a wide variety of powders including oxides, metals, and polymers. 8-14 Initial ALD work on powders was performed on small quantities of stationary powder supported on a tungsten grid, but this proved to be unscalable to larger quantities of powder. 15-23 To overcome this scaling problem, fluidized bed reactors (FBRs) have been adapted for allowing ALD depositions on the fluidized particles, and they have been proven for a wide variety of processes. 8-13,23-28 Alternatively, McCormick et al. reported a rotary reactor for performing ALD on powders. In this reactor, the particles were agitated mechanically through rotation of a porous metal cyclinder instead of being fluidized, making static reactant exposures possible. This increased the contact time between the powder surface and the reactant molecules, thus increasing the reactant efficiency, especially if the sticking coefficient of the precursors was low. 29 The reactor was used for the deposition of Al 2 O 3 and W on various particles. 23,30-33 On planar substrates plasma-enhanced ALD (PE-ALD) has been shown to improve the material properties of some ALD deposited materials, leading to higher film densities, lower impurity contents, and better electronic properties of the deposited films. 34,35 Due to the higher reactivity of the plasma species, less thermal energy is required to drive the surface Received: February 3, 2014 Accepted: April 29, 2014 Research Article www.acsami.org © XXXX American Chemical Society A dx.doi.org/10.1021/am5007222 | ACS Appl. Mater. Interfaces XXXX, XXX, XXX-XXX