Younsoo Kim

Composition and electrical properties of metallic Ru thin films deposited using Ru(C6H6)(C6H8) precursor

Metallic ruthenium films were prepared by metalorganic chemical vapor deposition (CVD) using a new precursor named (η6-benzene)(η4-1,3-cyclohexadiene)ruthenium (Ru(C6H6)(C6H8)) in Ar atmosphere, and the absolute composition and electrical properties were investigated. The absolute composition including hydrogen was determined by means of the elastic recoil detection time of flight (ERD-TOF). It was found that carbon contents in the films markedly decreased when tetrahydrofuran (THF) was supplied with the precursor during deposition. The variation in carbon content could be interpreted by the formation of hydrocarbon compounds as well as the formation of carbon oxide, resulting from the reaction between carbon and THF. In particular, Ru films contained hydrogen that originated in the hydrogen atoms in the precursor and was involved in the CVD process due to the catalytic effect of ruthenium on hydrocarbon and hydrogen. It was shown that grain size, among several other factors strongly affected the electrical properties of ruthenium films.

Leakage Current Characteristics of (Ba,Sr)TiO3 Thin Films Deposited on Ru Electrodes Prepared by Metal Organic Chemical Vapor Deposition

Leakage current characteristics of (Ba,Sr)TiO3 (BST) thin films deposited by metal-organic chemical vapor deposition (MOCVD) on Ru bottom electrodes were investigated. CVD-BST thin film on an Ru electrode showed much higher leakage current density than that on the Pt electrode. In the case of the CVD-BST thin film deposited on the PVD-BST(30 A)/Ru or N2O-plasma-treated Ru electrode, the leakage current density showed a very small value of about 2×10-8 A/cm2 at ±1 V and the dielectric loss was about 0.006. It was found that oxygen atoms adsorbed on the surface of the Ru bottom electrode during the deposition of PVD-BST or N2O plasma treatment played a key role in restoring the barrier height at the bottom interface.

Properties of Ru Thin Films Fabricated on TiN by Metal-Organic Chemical Vapor Deposition

Ruthenium (Ru) thin films were fabricated on TiN, as well as on SiO2, by metal-organic chemical vapor deposition using tris(2,4-octanedionato)ruthenium. We characterized the Ru films grown on TiN, and compared them with the films prepared on SiO2. The Ru films deposited on TiN showed weak crystallinity and random grain orientation similar to the films on SiO2, but revealed notably rougher surfaces than the films on SiO2. Moreover, deposition rates on TiN were lower than those on SiO2. These properties of the Ru films grown on TiN originated from the difficulties in nucleation and growth at the initial stage of the deposition. The inferior surface flatness and deposition rate could cause structural instability and poor coverage of the Ru electrode at the bottom of a deep concave hole for a three-dimensional capacitor where the Ru film was in contact with a diffusion barrier metal TiN plug.

Oxidation Characteristics of TiN Film as a Barrier Metal for Bottom-Electrode Ru Film Fabricated from Tris-(2,4-octanedionato)ruthenium

Bottom-electrode Ru films were fabricated on barrier metal TiN films by the reaction of tris-(2,4-octanedionato)ruthenium [Ru(od)3, Ru(C8H13O2)3] precursor and O2 gas. It was observed that the film incorporated the undesirable impurity of oxygen that could oxidize the TiN underlayer during postthermal treatments. To evaluate the oxidation characteristics of barrier metal TiN by the incorporated oxygen, samples with the Ru/TiN film stack were annealed in N2 ambient up to 700°C for 60 s by rapid thermal processing (RTP). No sign of TiN oxidation was observed in analyses by X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy. This was also confirmed by measuring the electrical resistance of a contact hole plugged with poly-Si and connected to the Ru/TiN stack, which shows an acceptable value below 1.3×103 Ω. We also investigated the oxidation characteristics of the Ru/TiN stack by atmospheric O2 gas. The samples were annealed in O2 ambient by RTP at 500°C, 600°C, and 700°C for 60 s. The Ru film began to oxidize to RuO2 at 500°C. With increasing temperature, further oxidations of Ru and TiN occurred simultaneously. Finally, at 700°C, Ru and TiN oxidized completely to RuO2 and rutile TiO2 phases, respectively. These results demonstrate the ease of oxidation of Ru and TiN films in O2 ambient.

Fabrication of Highly Dense Ru Thin Films by High-Temperature Metal-Organic Chemical Vapor Deposition with NH3 Gas as Ru Oxidation Suppressing Agent

We attempted to fabricate highly dense Ru thin films by metal-organic chemical vapor deposition at an elevated temperature of 400°C, employing NH3 gas to suppress Ru oxidation. A solution of 0.2 mol/L tris(2,4-octanedionato)ruthenium [Ru(od)3, Ru(C8H13O2)3] dissolved in n-butylacetate was used as a Ru source and O2 as a reactant gas. It was revealed that NH3 gas effectively eliminated residual oxygen from the Ru films. However, at higher feeding rates of a metal-organic source, Ru films showed poor densities and high electrical resistivities mainly due to significant carbon incorporation. By optimizing Ru(od)3 flow rate to less than 0.3 g/min to reduce contaminating carbon supply, we successfully produced highly dense and conductive Ru films. The best Ru film had a density of 12.2 g/cm3 and a resistivity of 12.0 µΩcm, which were excellent values close to the bulk ones.

Metal organic chemical vapor deposition of ru electrode for (ba,sr)tio3 capacitors

Abstract Ru films were deposited on TiN and SiO2 layers by metal organic chemical vapor deposition (MOCVD) at various deposition temperatures. We have used Ru(C8H13O2)3 as a Ru source and O2 as a reaction gas. The deposition of Ru films was controlled by surface-reaction kinetics with activation energy of 0.83eV below 300°C. The thickness and resistivity of Ru films decreased as increase of crystallinity after rapid thermal anneal (RTA). The dielectric constant and leakage current density of BST film deposited on MOCVD Ru showed 190 and 10−6 A/cm2 at ± 1V, respectively.

Low Temperature Chemical Vapor Deposition of (Ba, Sr)TiO3 Thin Films for High Density Dynamic Random Access Memory Capacitors

(Ba, Sr)TiO3 (BST) films are deposited on 8-inch wafers by the metal organic chemical vapor deposition (MOCVD) technique at a temperature as low as 400°C to obtain conformal step coverage and prevent oxidation of the diffusion barrier of simple stacked capacitors. The problems of low temperature process (formation of protrusions, titanium deficiency, severe thickness deviation) could be successfully overcome by proper modification of the CVD system and process conditions. Retrofitting the vaporizer to obtain flash evaporation of the liquid chemical source and introducing N2O gas as an oxidant were highly effective for reducing the thickness deviation and titanium deficiency. The Pt/BST/Pt capacitor with BST films deposited at 400°C and post-annealed at 700°C for 30 min under nitrogen ambient shows excellent electrical properties (Tox~6.6 A, J~1×10-7 A/cm2 @±1 V), which are satisfactory for application to high density dynamic random access memory (DRAM) capacitors beyond 256 Mbit generation.

Growth of RuO/sub x/ thin films by metalorganic chemical vapor deposition

RuO/sub x/ thin films were deposited on TiN/SiO/sub 2//Si substrates by metal organic chemical vapor deposition (MOCVD) at deposition temperatures of 250/spl deg/C-400/spl deg/ C. We have used Ru(mhd), as a metal organic (MO) source. No films were deposited without the addition of O/sub 2/ gas. RuO/sub 2/ films were deposited at high O/sub 2/ addition. For the deposition of Ru films in the surface reaction controlled region, the activation energy was 0.58 eV. The smooth and well-adherent Ru films had very low resistivities. The microstructure of Ru films was greatly dependent on deposition conditions. Ru films deposited at 27/spl deg/C showed a good step coverage.