Papers

ICMCTF2002 Session H4-1: Novel Materials and Processes

Thursday, April 25, 2002 8:30 AM in Room Royal Palm 4-6

Thursday Morning

Start	Invited?	Item
8:30 AM		H4-1-1 High Performance Transparent Conducting Oxide Thin Films Grown by Pulsed Laser Deposition for Organic Light-emitting Diodes H. Kim, J.S. Horwitz, W.H. Kim, Z.H. Kafafi, D.B. Chrisey (US Naval Research Laboratory) High quality transparent conducting oxide (TCO) thin films have been grown by pulsed laser deposition (PLD) on glass, plastic and single crystal substrates such as sapphire, MgO and yttria stabilized zirconia (YSZ) for use in organic light emitting diodes (OLEDs). Critical electrode issues for the OLED are the optical transparency, electrical resistivity, work function and surface roughness of TCO films. Films were deposited using a KrF excimer laser (248nm, 30 ns FWHM) at fluences of 1 - 2 J/cm² at substrate temperatures ranging from 25°C to 600°C in oxygen pressures ranging from 1 to 100 mTorr. Structural, electrical and optical properties of the films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Hall effect measurements and UV/VIS/NIR spectroscopy. In this talk, we report our work on the synthesis, doping, and characterization of indium- and zinc-based TCO phases including In₂O₃:Sn, In₂O₃:Zr, ZnO:Al, ZnO:Ga, and ZnO:Zr. For ITO films (100 nm thick) deposited on glass at 300°C in 10 mTorr of oxygen, a resistivity of ~2 x 10^â€“4 Ω-cm was observed. The average transmission in the visible range (400 - 700 nm) was about 90 % and the film surface roughness was about 0.5 nm. The Hall mobility and carrier density for ITO films (50 - 400 nm thickness) were observed to be in the range of 24 - 27 cm²/V-s and 5 - 10 x 10²⁰ cm^-3, respectively. We have used the ITO films, deposited by PLD on glass, plastic and single crystal YSZ substrates, as the anode contact in OLEDs. ITO based devices showed an external quantum efficiency of about 0.8 - 1.1 % at 100 A/m², which is comparable to that of a device fabricated using commercially available sputter-deposited ITO films. The properties of these films grown on various substrates will be compared and the use of these films as transparent anodes for OLEDs will be discussed.
9:10 AM		H4-1-3 Microstructural Comparison of Metallic Thin-films Created by Ion Beam Ablation and Sputtering/Electron Beam Evaporation* T.J. Renk, P.P. Provencio (Sandia National Laboratories); M. Kawamura (Kitami Institute of Technology, Japan) We are investigating the microstructure (grain size and orientation, dislocation density, etc) of metallic thin films formed by two different deposition processes: 1) either magnetron sputtering or electron beam evaporation from Pt, Er, and Sc targets; and 2) pulsed ion beam ablation (PIBD) of similar targets. In the later process, a beam of variable ion species (H, C, N) impinges on the target at fluences up to 10 J/cm², leading to ablation and redeposition onto a substrate. Typical target distances are 40 cm, with the target-substrate distance variable from 10 to 25 cm. The substrate can be heated at up to 700C. After film preparation, both types of samples were analyzed by cross-sectional Transmission Electron Microscopy (TEM). In the case of a 1 µm Pt film, the microstructure produced by PIBD differs significantly from a layer produced by magnetron sputtering. In the latter, approximately 1 µm-tall vertical-tending, columnar grains with parallel columnar dislocations are observed, extending the length of the layer thickness. In contrast, the PIBD-formed layer exhibits a nano-crystalline structure, with vertical and randomly oriented grains as small as 5 nm to several hundred nm in size. The dislocations tend to be vertical but are terminated by grain boundaries and do not extend through the thickness of the layer. Heating the substrate to 200C appears to enlarge the grain size. We also plan to produce and study Er and Sc films by PIBD, and compare them to films produced by electron beam evaporation. The effect of doping the PIBD layers with small amounts of other metals will be investigated. Latest results will be presented. * Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Co., under US DOE Contract DE-AC04-94AL85000.
9:30 AM		H4-1-4 Deposition of Silicon Nitride at Atmospheric Pressure G.R. Nowling (University of California, Los Angeles); S.E. Babayan (Surfx Technologies); V. Jankovic, R.F. Hicks (University of California, Los Angeles) Silicon nitride films were deposited downstream of a non-equilibrium, atmospheric pressure plasma source. This novel device produces a stable plasma over large areas suitable for processing a wide range of materials. The discharged was produced by flowing nitrogen and helium through two perforated electrodes, driven by 13.56 MHz radio frequency power. Deposition occurred by mixing silane with the plasma effluent, and directing the gas flow onto a rotating silicon substrate heated to between 100 and 500 °C. A maximum growth rate of 1300±130 Å/min was observed, which is 3 to 10 times higher than that recorded in low-pressure, remote PECVD systems. Varying the N₂/SiH₄ feed ratio from 5.4 to 54.0 caused the film stochiometry to shift from SiN_1.2 to SiN_1.45. Minimum impurity concentrations of 0.04% carbon, 3.6% oxygen and 13.6% hydrogen were obtained at 500 °C and an N₂/SiH₄ feed ratio of 22.6. The growth rate increased with increasing silane and nitrogen partial pressures, but was invariant with respect to substrate temperature and rotational speed. The deposition rate also decreased sharply with distance from the plasma. These results combined with emission spectra taken of the afterglow suggest that gas-phase reactions between nitrogen atoms and silane play an important role in the reaction mechanism. At the meeting, we will discuss the potential of atmospheric pressure plasmas for enhancing thin film coating processes.
10:30 AM		H4-1-7 Microstructure and Electrical Properties of (Pb, Sr)TiO₃ Thin Films for Tunable Microwave Device C.I. Kim (Chung-Ang University, KOREA); C.I. Lee (Ansan College of Technology, Korea); K.T. Kim (Chung-Ang University, KOREA) Electrical tunable ferroelectric thin film devices rely on the variation of a ferroelectric material^'s dielectric constant with application of an electric field. (Ba,Sr)TiO₃ (BST) series, (Pb,Ca)TiO₃ (PCT) series and (Pb,Sr)TiO₃ (PST) series are promising ferroelectric materials for tunable microwave device applications such as electronically tunable mixers, delay lines, filters and phase shifters. The requirements of ferroelectric materials are low dielectric constant, high tunability, low losses and low leakage current. Since PST thin films for tunable microwave device is not widely studied, we investigated on the structural, electrical properties of PST thin films as a function of Pb/Sr compositions prepared using Sol-Gel method. The films were characterized by x-ray diffraction (XRD), Auger electron microscopy (AES), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy(TEM) and atomic force microscopy (AFM). The electrical measurements were conducted in the metal-insulator-metal (MIM) capacitor configuration. MIM capacitors with 0.2mm Pt dots were formed by sputter deposition. Capacitance, dissipation factor, and dielectric permitivity were measured with an HP 4192A impedance analyzer. The films insulating properties, leakage current(I_L), were evaluated via I-V measurements using a HP 4140B semiconductor test system.
10:50 AM		H4-1-8 Integration of a Stack of Two Fluorine Doped Silicon Oxide Film with ULSI Interconnect Metallization Y.L. Cheng (National Chiao Tung University, Taiwan, ROC); Y.L. Wang (Taiwan Semiconductor Manufacturing Company, Taiwan, ROC); J.K. Lan (National Chiao Tung University, Taiwan, ROC); J.K. Wang (Taiwan Semiconducor Manufacturing Company, Taiwan, ROC) A major challenge for back-end interconnect technology as device geometries shrink is the development of low dielectric constant materials with good gap-filling properties that are suitable for microelectronics manufacturing. Recently, Fluorosilicate Glass (FSG) with low dielectric constant received much attention for manufacturing. Although FSG film have been demonstrated as a potential inter-metal dielectric (IMD) for sub-half micro devices, the integration of a stack of two kinds of fluorine doped silicon oxide films depositing on HDP-CVD system and PECVD system was less investigated. In this research, a very stable process was demonstrated for a stack of HDP-CVD FSG and PECVD FSG layers, considering stable and throughput. The integration issues were evaluated. The crack due to multi-level metal technology was eliminated when implementing a higher compressive stress PECVD FSG film as capping layer. We also have 11% capacitance reduction comparing a stack of FSG films to undoped silicon oxide. No problem occurs for via photo, via etching and chemical mechanical polishing of FSG film. The via-resistance of a stack of FSG layers as well as full HDP-FSG scheme is comparable. These results are very promising for the integration of FSG films as inter-metal dielectric for devices..
11:10 AM		H4-1-9 Metal-organic Chemical Vapor Deposition NbxTa(1-x)N Films for Diffusion W.C. Gau, C.W. Wu (National Tsing Hua University, Taiwan, ROC); T.C. Chang (National Sun Yat-Sen University, Taiwan, ROC); P.T. Liu (National Nano Device Laboratory, Taiwan, ROC); C.J. Chu, C.H. Chen (Nanmat Technology Co., LTD., Taiwan, ROC); L.J. Chen (National Tsing Hua University, Taiwan, ROC) Abstract: In this study, a novel metallic barrier of Nb_xTa_(1-x)N for copper metallization has been investigated for the first time. The _xTa_(1-x)N barrier was prepared by metal-organic chemical vapor deposition (MOCVD) at 375°C with tetrakis-diethylamido-niobium (TDEAN) and pentakis-diethylamido-tantalum (PDEAT) as precursors. Amorphous thin films can be obtained by thermal deposition at temperatures from 500° to 600° C. The activation energy of the MOCVD process was 0.82 eV. By the incorporation of NH₃ gas into reactants, MOCVD deposition temperature and carbon concentration in the Nb_xTa_(1-x)N film were both further reduced. In addition, NH₃-plasma post-treatment was implemented to prevent oxygen including into the barrier film. SIMS analysis was utilized to confirm the main compositions of Nb and Ta in the metallic barrier. The films were subsequently characterized by x-ray diffraction (XRD), Auger electron spectroscopy (AES), and transmission electron microscopy (TEM). Depth profile and the chemical environment of elements in the films were analyzed by x-ray photoelectron spectroscopy (XPS).
11:30 AM		H4-1-10 Copper Surface Protection with a Completely Enclosed Copper Structure for a Damascene Process T.C. Wang (Taiwan Semiconductor Manufacturing Co. & National Chiao-Tung Univ., Taiwan); T.E. Hsieh (National Chiao-Tung University, Taiwan, ROC); Y.L. Wang (Taiwan Semiconductor Manufacturing Co. & National Chiao-Tung Univ., Taiwan, ROC); K.W. Chena (Taiwan Semiconductor Manufacturing Co., Ltd. & National Chiao-Tung Univ., Taiwan, ROC); Y.K. Lina (Taiwan Semiconductor Manufacturing Co., Ltd., Taiwan, ROC) As integrated circuit manufactures are moving to copper interconnection for their most advanced products, protection of Cu surfaces presents a big challenge for the back-end-of-line manufacturing process. Cu damages, such as Cu corrosion and oxidation, are often observed on wafers with open Cu surface in the presence of moisture and/or acidic gases. Cu corrosion destroys Cu surface. On the other hand, Cu oxide results in poor adhesion both at Cu/barrier layer and Cu/stop layer interfaces. Cu oxide also enhances Cu hillock during thermal process. In this paper, a novel Cu dual damascene structure which completely encloses Cu surface with a barrier layer was introduced and thus avoids Cu corrosion and oxidation due to isolation with moisture and acidic.