Ki-Young Oh

Interfacial reaction between chemically vapor-deposited HfO2 thin films and a HF-cleaned Si substrate during film growth and postannealing

Interfacial reactions between HfO2 thin films and a Si substrate during thin-film growth and postannealing under a N2 atmosphere were investigated by high-resolution transmission electron microscopy, Auger electron spectroscopy, and electrical measurements of metal–insulator–semiconductor capacitors. HfO2 thin films were deposited on HF-cleaned Si wafers by a chemical-vapor-deposition technique at a wafer temperature of 200 °C using a carbon-free precursor [Hf(NO3)4]. The film thicknesses ranged from 1.5 to 5.6 nm. During the initial stage of film growth, the Si surface oxidized to form a Si-rich hafnium silicate film. With increasing deposition time, Hf-rich hafnium silicate films grew. Postannealing resulted in a double-layered film structure with upper and interfacial layers having dielectric constants of approximately 9.3 and 5.6, respectively. The results were compared with the results from HfO2 films grown on SiO2-passivated Si wafers.

Chemical Vapor Deposition of HfO2 Thin Films Using a Novel Carbon-Free Precursor: Characterization of the Interface with the Silicon Substrate

HfO 2 thin films were deposited on Si wafers by a chemical vapor deposition (CVD) technique at temperatures ranging from 200 to 400°C using a new carbon-free precursor [Hf(NO 3 ) 4 ]. The growth behavior was under a steady state when the interfacial oxide layer was excluded in film thickness estimation by ellipsometry. The as-grown interfacial layer formed at 200°C was apparently composed of Hf, Si, and O. Postannealing under a N 2 atmosphere at temperatures >500°C resulted in a decrease in interfacial layer thickness by decomposition of the Hf-Si-O layer to SiO 2 and HfO 2 The HfO 2 film showed a crystalline microstructrue even in the as-deposited state when the film thickness was 170 A. However, the films were amorphous when the film thickness was <70 A. The dielectric constant of the as-deposited and postannealed HfO 2 thin films were approximately 18 and 22, respectively.

Comparison Study for TiN Films Deposited from Different Method: Chemical Vapor Deposition and Atomic Layer Deposition

This paper compared two different film deposition processes for formation of TiN barrier layers, conventional TiCl 4 -based chemical vapor deposition and atomic layer deposition (ALD). The 30nm thick TiN film deposited by conventional TiCl 4 -based CVD at the process temperature of 600°C followed by NH 3 post-deposition anneal showed about 180 μΩcm of resistivity, over 95 % of step coverage for the pattern aspect ratio of 6 on 0.35 μm contact diameters, and below 2 at.% of chlorine contents in the film. Meanwhile, the films deposited by ALD at 100°C lower process temperature than CVD showed much better film properties even without post-deposition anneal. It showed lower resistivity values and lower chlorine incorporation along with better step coverage characteristics. More detailed material analysis was done by AFM, SEM, and AES.

Electro-mechanical characteristics of lead-zirconate-titanate ceramics under vibration-level change

Electro-mechanical characteristics by changing the vibration-level were studied in lead-zirconate-titanate (PZT) based ceramics using the constant current/velocity driving method. The fractional changes of Youngs modulus and mechanical dissipation factor are a function of the square of the effective vibration velocity. The increase of the dissipated-vibration-energy with the vibration-level change causes heat generation. Ferroelectric hysteresis loss is assumed to affect the dissipated-vibration-energy through the mechanical dissipation factor.

Optical Study of Domains in Antiferroelectric Ceramics

Antiferroelectric ceramics are now highly focused as giant strain actuator materials. In this study, domain formation in antiferroelectric lead zirconate based ceramics (Pb0.99Nb0.02[(Zr0.6Sn0.4)1-yTiy]0.98O3) was observed dynamically under an electric field at various temperatures using a high-resolution charge-coupled-device (CCD) microscope system. Field induced polarization and field induced strain were also measured. No domain was observed without an electric field, but clear domains appeared with an electric field due to the phase transition from an antiferroelectric to a ferroelectric state. Results of the optical study can explain well the electrical properties. The behavior of the field induced domains showed a shape memory effect and the domains were well oriented compared with normal ferroelectric ceramics.

Low temperature metal-organic chemical vapor deposition of (Ba, Sr)TiO3 thin films for capacitor applications

Abstract Low temperature metal-organic chemical vapor deposition (MOCVD) processes for producing high dielectric (Ba, Sr)TiO3 (BST) films studied using a noble dome type reactor, liquid delivery technique and new precursors. One of the problems associated with conventional MOCVD reactors having a shower head was substrate surface-dependent deposition of film composition as well as the thickness, which might result in pattern-dependent deposition of BST films. The new chamber used in this study was capable of controlling both the substrate heater and chamber wall temperatures which successfully eliminated such surface-dependent deposition property. The film composition and thickness were essentially the same on either Pt and SiO2 surfaces when both the wall and heater temperatures were controlled. However, the film composition, thickness and uniformity were differed markedly on the Pt and SiO2 surfaces when only the heater temperature was controlled. Excellent step coverage and smooth (haze-free) surface morpholgy of BST films were obtained from a deposition at 470°C.

Low temperature metal-organic chemical vapor deposition of Ru thin films as electrode for high dielectric capacitors

Abstract Low temperature metal-organic chemical vapor deposition (MOCVD) process of Ru films for use as electrode material was studied using a noble dome type reactor, liquid delivery technique and a new precursor. The films were grown at temperatures ranging from 275°C to 480°C in which film growth was controlled by a surface chemical reaction with a small activation energy of 0.21 eV. The root-mean-squared surface roughness was as low as 23 Å for a film grown at 290°C on a SiO2 surface.

Effect of eutectic lithium sulfate-sodium sulfate flux on the synthesis of lead magnesium niobate

The effect of the amount of sulfate flux (Li2SO4-Na2SO4) on the phase stability and dielectric properties of lead magnesium niobate ceramics prepared by molten salt synthesis, has been studied as a function of calcining and sintering temperatures. The percentage of perovskite phase tended to increase with increasing the amount of flux and calcination temperature. When powders containing the same amount of flux with respect to starting oxides were calcined at 750°C for 2 h, the pyrochlore phase was about 2%. Above 800°C, the perovskite phase was stable at about 97% regardless of the amount of flux. However, the increase of the amount of sulfate flux resulted in an increase of the average particle size and a decrease of dielectric constant. These results can be explained by the sinterability and microstructure analysis.

Preparation and characterization of (Ba,Sr)TiO 3 thin films by liquid source chemical vapor deposition

The cocktail source of BST was prepared by mixing of Ba, Sr, and Ti precursor solution with specific mole ratio. This cocktail source was vaporized and delivered into the warm wall reactor by liquid delivery system(LDS) and gaseous source was distributed by simple structure of gas injector instead of showerhead system. The thickness uniformity of BST on 8 inch wafers were less than 3%. The Ti composition uniformity of our films were less than the 1 at%(1σ ) at stoichiometric and near stoichiometric. Their dielectric constant was about 230 and leakage current density was lower than 10 -8 A/cm 2 under ±1V bias. Excellent step coverage and smooth (haze-free) surface morphology of BST films were obtained by a deposition using a noble dome type reactor. The merit of our warm wall type reactor also will be explained by excellent step coverage and the uniform composition with 3 dimensional structure. Our achievement should be applicable to the capacitor of next generation DRAM.

Metal Organic chemical Vapor Deposition of (Ba, Sr)RuO3 oxide electrode for (Ba, Sr)TiO3 using nozzle type injector

Abstract The oxide electrode (Ba, Sr)RuO3, which enhances the property for (Ba, Sr)TiO3 film owing to its similarity in structure and chemical composition, was deposited on a 4 inch p-type Si wafer by Metal Organic Chemical Vapor Deposition (MOCVD). Instead of a shower head, a quartz nozzle was used for injecting source, which showed effective large area uniformity. Liquid delivery system (LDS) and vaporization cell were utilized for the delivery and vaporization of single cocktail source, respectively. The source feeding rate was controlled by Liquid Mass Flow Controller(LMFC), Ba(TMHD)2, Sr(TMHD)2, Ru(TMHD)3 precursors and solvent [1-EtylePiPerdine(C7H15N)] were mixed together for single cocktail source. Deposition parameters such as the oxygen flow and the source flow rate were sensitive to phase formation, resistivity, and the composition ratio of (Ba, Sr)RuO3 films. Highly (110)-textured (Ba, Sr)RuO3 film was obtained when Ar/O2 ratio of 200/120 seem at 0.05 cc/min of the source flow rate. The process window of stoichiometric composition of BSR film was observed when the source flow rate was 0.075–0.1 cc/min. Oxygen annealing of (Ba, Sr)RuO3 films improved the properties of the films without changing the (110)texture and the resistivity and surface roughness were 500μΩcm and 12.7 Å, respectively.