Chee Won Chung

Effect of Oxygen Concentration on Properties of Indium Zinc Oxide Thin Films for Flexible Dye-Sensitized Solar Cell

Indium zinc oxide (In2O3–ZnO, IZO) thin films were prepared with variation of oxygen concentration in Ar sputtering gas using rf magnetron sputtering system. Transmittance was greatly improved from 75 to 90% since surface roughness slightly decreased by adding oxygen and low resistivity of 3.28×10-4 Ω cm was achieved at 0.4% oxygen concentration. The performance of dye sensitized solar cell (DSSC) was also studied by fabricating cells with IZO thin films using UV/ozone treatment. According to the results, the efficiency was strongly affected by both transmittance and resistivity of IZO thin films deposited at different oxygen concentrations. Finally, the highest efficiency of 3.11% was achieved from IZO films deposited with 0.4% oxygen concentration, which exhibits a promising application of IZO thin films to flexible DSSC.

INVESTIGATION ON ETCH CHARACTERISTICS OF GESBTE THIN FILMS FOR PHASE-CHANGE MEMORY

ABSTRACT Inductively coupled plasma reactive ion etching of GeSbTe (GST) thin films with a photoresist mask was carried out in a Cl2/Ar gas. The monotonous increase in etch rate with increasing Cl2 concentration indicates that the etching of GST films obeys the reactive ion etching mechanism. The etch rates increased with increasing coil rf power and dc-bias voltage. The etch profiles was improved with decreasing coil rf power and dc-bias voltage and gas pressure gave little influence on the etch profile. The x-ray photoelectron spectroscopy analysis reveals that the rate limiting step in GST etching study is the etching of Te. Anisotropic etching of GST films was achieved using a Cl2/Ar chemistry at the optimized etch conditions.

Inductively coupled plasma etching of a Pb(Zr x Ti 1-x )O 3 thin film in a HBr/Ar plasma

The etching of Pb(ZrxTi1-x)O3 (PZT) thin films was performed using HBr/Ar gas in an inductively coupled plasma. The etch rate and etch profile of the PZT films were investigated as a function of the gas concentration of the HBr/Ar mixture. In addition, the etch parameters, including coil power, dc bias and gas pressure, were examined to characterize the etching process of the PZT films. An enhancement of the etch rate with increasing gas concentration was found, which indicates that PZT etching by HBr/Ar follows the reactive ion etching mechanism. It was found that the maximum etch rate and selectivity for Pt films was around 40% HBr under the etch conditions used in this study. From X-ray photoelectron spectroscopy (XPS) analysis, it was observed that the Pb component in PZT solid solution showed a faster etching than the Zr and Ti components. The etch rate and the degree of anisotropy of the PZT films were enhanced by increasing the coil power and dc-bias voltage, and by lowering the gas pressure. An etch rate of 900 A/min and a steep etch profile of > 70° could be achieved with HBr/Ar chemistry.

Effect of pre-annealing on physical and electrical properties of SrBi2Ta2O9 thin films prepared by chemical solution deposition

Abstract SrBi2Ta2O9 (SBT) thin films with Bi layered-perovskite structure were formed by chemical solution deposition method. The effects of pre-annealing on physical and electrical properties of SBT thin films were investigated by employing rapid thermal annealing (RTA) and furnace annealing. SBT thin films pre-annealed by furnace after each spin-coating exhibited better surface morphology and electrical properties than those pre-annealed by RTA. The crystallization mechanisms of SBT thin films with pre-annealing by RTA and furnace were examined by X-ray diffraction (XRD) analysis and scanning electron micrograph (SEM). Finally, the optimum condition of furnace pre-annealing (700°C for 30 min) was found to give remanent polarization (2Pr) of about 20 μC/cm2, leakage current density of less than 10−7 A/cm2, and breakdown voltage of 15 V.

Platinum etching using a TiO2 hard mask in an O2/Cl2/Ar plasma

The dry etch behavior of Pt films using a TiO2 hard mask was investigated with an O2/Cl2/Ar gas chemistry in an inductively coupled plasma. The variations in etch rates and etch profiles of both the Pt films and the TiO2 masks were examined as a function of Cl2 and O2 concentration. It was found that the ratio of O2 to Cl2 concentration strongly influenced the etch selectivity of the Pt film relative to the TiO2 mask. X-ray photoelectron spectroscopy indicates that the addition of O2 to the gas mix causes a decrease in the TiO2 etch rate as a result of the oxidation of Ti2O3 and TiO species. It is proposed that these oxides arise via the reduction of TiO2 in the presence of a Cl2/Ar plasma. A 1 μm ×1 μm minimum feature size was successfully etched with this TiO2 mask material, yielding a sidewall of approximately 75° in slope that did not exhibit redeposition or residue.

Effects of Oxide Electrode on PbZrxTi1-xO3 Thin Films Prepared by Metalorganic Chemical Vapor Deposition.

The effect of the RuOx /Pt multilayer electrode on the microstructure and ferroelectric properties of PbZrx Ti1-x O3 (x=0.52) prepared by metalorganic chemical vapor deposition (MOCVD) were studied. The variation of RuOx thickness resulted in changes in the RuOx surface morphology. These modifications of RuOx surfaces caused changes in the texture, surface morphology and ferroelectric properties of lead zirconate titanate (PZT) thin films deposited on the multilayer electrodes. The improvements in the ferroelectric properties were attributed to the altered microstructure. Remanent polarization (P r) and coercive voltage (V c) of the multilayer PZT capacitors were estimated to be 22 µ C/cm2 and 0.7 V at 5 V, respectively. The multilayer PZT capacitors did not degrade up to 1012 cycles at 2 V. In this study, the factors of the deposition of PZT on RuOx /Pt multilayer electrode by MOCVD were investigated and the integration process of the Pt/RuOx /PZT/RuOx /Pt capacitor was also discussed.

Dry etching of Pt/PbZrxTi1−xO3/Pt thin film capacitors in an inductively coupled plasma (ICP)

Abstract Dry etching of PbZrxTi1−xO3(PZT) and Pt thin films was studied with Cl2/C2F6/Ar gas in an Inductively Coupled Plasma (ICP). The etch rates were investigated at various etching conditions including etch gas, coil RF power, DC bias, and gas pressure. For the etching of PZT film, chemical enhancement was found. Under etching conditions used in this study, the etch rate of 430 to 1500 A/min was obtained for PZT film and the etch rate of Pt film was in the range of 120 to 1890 A/min. Selectivity of PZT to Pt was controllable in the range of 0·32 to 6·17. For the fabrication of Pt/PZT/Pt thin film capacitors, the etching process using the conventional photolithography has been developed with high etch rates and good selectivities for both PZT and Pt films.

Inductively Coupled Plasma Etching of Pb(ZrxTi1- x)O3 Thin Films in Cl2/C2F6/Ar and HBr/Ar Plasmas

Pb(ZrxTi1-x)O3 thin films were etched in an inductively coupled plasma by using various etch gases such as Cl2/Ar, C2F6/Ar, Cl2/C2F6/Ar and HBr/Ar. The etch rates and etch profiles for each etch gas were investigated. Fast etch rates were obtained in chlorine-containing etch gases (e.g., Cl2/Ar and Cl2/C2F6/Ar), and clean and steep etch profiles were achieved in Cl2/Cv2F6/Ar or HBr/Ar gases. The gas mixture of Cl2 and C2F6 was proposed to give a fast etch rate and a steep sidewall angle of etched patterns. The optimum gas mixture of Cl2C2F6/Ar was found by varying the gas ratio of Cl2 to C2F6. On the other hand, HBr/Ar gas as an alternative for etching of the Pb(ZrxTi1-x)O3 films was examined. Cl2/C2F6/Ar and HBr/Ar etch gases were compared with respect to etch rate, etch profile and electrical properties.

High Density Plasma Etching of Iridium Thin Films in a Cl2/O2/Ar Plasma

Dry etching of iridium films using a TiN mask was studied with a Cl 2 /O 2 /Ar gas mix in an inductively coupled plasma. The variations in etch rates and etch profiles of iridium films and TiN masks were investigated as a function of O 2 and Cl 2 concentrations. The etch rate of iridium film in this study was in the range 50-100 nm/min. It was found that the ratio of O 2 to Cl 2 concentration in an etch gas strongly influenced the etch selectivity of the iridium film relative to the TiN mask, which in turn impacted the etch profile of iridium films. By increasing coil power and bias voltage, or by decreasing gas pressure, the etch rate and selectivity of iridium films were increased and the etch profile was improved. Iridium etching with a residue-free steep sidewall of 70-80° was achieved.

Effects of substrate modification on the growth and characteristics of mocvd PZT

Abstract Pb(ZrxTi1-x)O3 thin films(PZT) were deposited on Pt/Ti/SiO2/Si(100) and RuO2/Pt/Ti/SiO2/Si(100) substrates by metal-organic chemical vapor deposition(MOCVD). The surface morphology of the Pt substrate was altered with the deposition temperature and thickness. The variations in the microstructure of PZT films were investigated as a function of substrate morphology. In addition, the effects of RuO2/Pt multilayer electrode on the microstructure and electrical properties of PZT capacitor were also studied. Finally, the PZT capacitors integrated on 4” wafer with multilayer electrode were evaluated.