ICMCTF2003 Session CP-1: Symposium C Poster Session

Monday, April 28, 2003 5:00 PM in Room Town & Country
Monday Afternoon

Time Period MoP Sessions | Topic C Sessions | Time Periods | Topics | ICMCTF2003 Schedule

CP-1-1 Mn-activated Y2O3-Ga2O3 EL Phosphor Thin Films Prepared by r.f. Magnetron Sputtering
T. Minami, Y. Kobayashi, T. Miyata, K. Suzuki (Kanazawa Institute of Technology, Japan)
In this paper, we introduce a new ((Y2O3) 1-X-(Ga2O3) X) multicomponent oxide that has shown promise as a host material for electroluminescent (EL) phosphors. The ((Y2O3) 1-X-(Ga2O3) X):Mn phosphor thin films were prepared on thick BaTiO3 insulating ceramic sheets by r.f. magnetron sputtering using a powder target with a Ga2O3 content (composition, X) in the range from 0 to 100 mol.%. The Mn content (Mn/Mn+Y) atomic ratio in the ((Y2O3) 1-X-(Ga2O3) X):Mn films was varied from 0.2 to 4 at.%. In order to improve the luminescent characteristics, all deposited phosphor thin films were postannealed in an Ar atmosphere for 1 h at 900-1100°C. The postannealed multicomponent oxide phosphor thin films were polycrystalline, irrespective of the Ga2O3 content, as evidenced from x-ray diffraction analyses. The obtained luminescent characteristics of ((Y2O3) 1-X-(Ga2O3) X):Mn thin films were strongly dependent on the preparation conditions as well as the Ga2O3 content. The photoluminescent (PL) and EL emission spectra observed from ((Y2O3) 1-X-(Ga2O3) X):Mn thin films prepared with a Ga2O3 content below approximately 60 mol.% consisted of a single peak at a wavelength of approximately 580 nm. With a Ga2O3 content above approximately 70 mol.%, an emission peak appeared at a wavelength of approximately 510 nm. As a result, the color of both PL and EL emissions changed from yellow to green as the Ga2O3 content was increased. The obtained luminance increased as the Ga2O3 content was increased, reached a maximum at a content of approximately 50 mol.%, and then decreased with a further increase of the content. A high luminance above 7000 cd/m2 was obtained in 1 kHz-driven TFEL devices using a ((Y2O3) 0.5-(Ga2O3) 0.5):Mn thin film prepared with a Ga2O3 content of 50 mol.%. In addition, a luminance above 500 cd/m2 and a luminous efficiency of approximately 10 lm/W were obtained in 60 Hz-driven TFEL devices using this thin film.
CP-1-2 Anisotropic Etching of InP, InGaAs, and InAlAs in Low-bias Inductively Coupled Plasma Using Cl2/BCl3/N2/Ar Mixtures.
J.W. Bae, I. Adesida, H.-K. Kim (University of Illinois at Urbana-Champaign)
The fabrication of quantum well photodetectors(QWP) and related III-V or II-VI based devices requires a lot of patterning steps using either wet or dry processing. Most researches of dry etching of InP and related materials were focused on chlorine-based gas plasmas. By the way, the byproduct generated by chlorine-based plasma, indium chloride, has very low volatility that is responsible for surface roughness and low etch rate. Also, the techniques which removal rate of indium becomes the rate limiting process, and is dictated by the sputtering efficiency aren’t able to give the solution for low damage and vertical etching. Currently, it is not easy to solve the problem between the volatility and the damages. Therefore, there is a critical need for low ion bombardment dry etching process to reduce the damages, and for etching chemistry which can decrease the difference of desorption between InClx and PClx by controlling the volatility of PClx. In the present work, chlorine-based plasma was introduced in an inductively coupled plasma(ICP) reactor for etching of InP, InGaAs, and InAlAs. The substrate bias and temperature were kept below -100V and room temperature to 250°C, respectively. And nitrogen, argon, and boron chloride were used as dilution gases and additive gas, respectively. Especially, nitrogen is one of the dilution gases for chlorine, and is known to be effective in hindering the volatility of PClx by creating non-volatile byproduct such as PNx. Each etch rates were measured from the depth of the etched features with a stylus profilometer before and after removing the SiO2 mask layer in a buffered oxide etchant. The side wall profiles of etched samples were evaluated with a scanning electron microscope(SEM) before removing the SiO2 mask layers. The surface roughness was observed by atomic force microscopy(AFM).
CP-1-3 Inductively Coupled Plasma Etching of ZnO and Effect of BCl3 Plasma Treatment on Ti/Au Ohmic Contact
H.-K. Kim, J.W. Bae, I. Adesida (University of Illinois at Urbana-Champaign); K.-K. Kim, T.-Y. Seong (Kwangju Institute of Science and Technology)
Etching characteristics of ZnO are investigated by means of inductively-coupled- plasma reactive ion etching (ICP-RIE) in BCl3-based plasmas. Etch rates are studied as a function of BCl3/Cl2/Argon chemistries, substrate temperature, ICP coil power, rf power, and working pressure. Surface profilometer, scanning electron microscopy, and atomic force microscopy are used to characterize the etch rate, etch profile, and the surface morphology of the etched samples. It is shown that the etch rate is determined by the BCl3 content in the plasma. Auger electron spectroscopy results demonstrate that the BCl3-based etching process produces a negligible change in the surface stoichiometry of ZnO. In addition, the effect of BCl3 plasma treatment on the Ti/Au ohmic contact on ZnO was investigated. Using BCl3 plasma treatment, we obtained improved room-temperature Ti/Au ohmic contacts on ZnO.
CP-1-4 Development of a MgO Sputtering System for Plasma Display Panel
Y.W. Choi, J.H. Kim (Korea Electrotechnology Research Institute, South Korea)
MgO Sputtering system for PDP application has been developed. This system is manufactured with a vertical In-Line type of 42 inch. The reactive magnetron discharge is applied for the MgO thin film deposition using unipolar power source of 50 kHz. To understand the characteristics of this system, fundamental experiment is being carried out under the several plasma conditions. As a tentative experiment result, a static deposition rate is showing about 23 nm/min at the distance of 53 mm between target and substrate. The texture of the sputtered MgO film shows (111) structure dominantly.
CP-1-5 Ion Beam Induced Erosion and Humidity Effect of MgO Protective Layer Prepared by Vacuum Arc Deposition
J.-K. Kim, E.-S. Lee, S. Lee, D.-H. Kim, D.-G. Kim, G.-H. Lee (Korea Institute of Machinery and Materials (KIMM), South Korea)
MgO films have been suggested as a protective layer for alternating current plasma display panels (AC PDP), which play significant roles in preventing the failure of the dielectric layer from sputtering by ions, in lowering the firing and sustain voltages due to a higher secondary electron emission coefficient (γ), and in allowing higher optical transmittance. In this work, MgO thin films were deposited on glass substrates by vacuum arc deposition equipment using a magnesium metal target at various oxygen gas flows. We investigated structural and optical properties of the MgO protective films. To measure reasonable erosion-rates of the MgO protective layers, we introduced an acceleration test method, namely, Ar + ion beam induced erosion test. We also examined the effect of the moisture on the optical transmittance of the MgO protective layers, which showed that the optical transmittance was decreased with the relative humidity. X-ray diffraction and AFM have been also used to study behaviors of the structure and surface morphology.
CP-1-6 Surface Metallization Effects on the Optical and Dielectric Properties of Nano-Structured Silicon
I.K. Pan, G.Q Yu, Y.Q. Fu, C.Q. Sun, B.K. Tay (Nanyang Technological University, Singapore)
Since the discovery of visible light emission from high porosity structures in 1990, porous silicon (PS) has been regarded as a promising material for applications in the microelectronics such as LEDs, waveguides, optical filters, photovoltaic diodes and various types of sensors. Such devices can be fabricated by either varying the porosity of the PS layer itself or by depositing some other films on the PS surface of metals, semiconducting oxides or polymer films depending on the application. Special efforts have been made to realize light emission diodes using metal-PS structures. Given the large and varied body of work on metal-PS structures, there still remains a basic lack of knowledge regarding the structure and composition of the species actually responsible for the optical and dielectric activity of PS. As a result, a thorough comprehension of the physical phenomena in the metal-PS contact is necessary for PS-related devices. Cu, Al and Ni films of ~10 nm thick were deposited on PS at room temperature using Filtered Cathodic Vacuum Arc (FCVA) system. The porous layer with the thickness of about 50 mm were obtained on p-type (100) Si wafer, by applying 50 mA/cm2 in a HF, C2H5OH and H2O solution. XPS and PL revealed apparent Si 2p core level energy and photoluminescence blueshift for PS modified by Cu, Al and Ni compared with as-grown one. XRD results showed that there was lattice variation for metalized and as-grown PS. The refractive index of these films, measured by ellipsometry, varied with different metals. An explanation based on metalization induced crystal field change provides an insight as to the mechanisms responsible for these changes.
CP-1-7 Comparative Study of ITO Thin Films Deposited at Room Temperature by Magnetron Sputtering using RF and DC Pulsed Power
M. Vives, C. Corbella, A. Pinyol, C. Person, I. Porqueras, E. Bertran (Universitat de Barcelona, Spain)
Indium Tin Oxide (ITO) thin films were deposited on unheated polyester and glass substrates by sputtering technique from a ceramic ITO target, which was powered from 50 W to 200 W by either RF and DC pulsed power sources. All the depositions were made at room temperature from 0.2 Pa to 2.0 Pa of total pressure. The DC pulsed power was modulated at 100 kHz and 80 % of duty cycle. The electric and optical parameters of ITO films were obtained by four-probe, Hall effect and optical transmittance measurements. Thickness measurements by a profilometer provided us the resistivity values and the deposition rate. Conductivities over 1200 S/cm and mobilites of charge carriers higher than 30 cm2V-1s-1 were achieved at low pressures. The photopic transmittance was close to 90 %. The oxygen partial pressure of the residual gas was controlled and it supposed an important drawback in order to obtain high conductivity films. The properties of the films are discussed as a function of technological parameters and the kind of power source used. The films with the lowest square resistance are of great interest for applications as transparent electrodes for large area optoelectronic devices.
CP-1-8 A Study of SiC Etch Characteristics in Fluorine Containing Magnetic Enhanced Inductively Coupled Plasma (MEICP)
D.W. Kim, C.H. Jeong, H.Y. Lee, H.S. Kim (Sungkyunkwan University, South Korea); Y.J. Sung (Samsung Advanced Institute of Technology, South Korea); G.Y. Yeom (Sungkyunkwan University, South Korea)
Silicon carbide(SiC) is one of the attractive semiconductor materials having a wide band gap, high temperature stability, and high thermal conductivity. Therefore, SiC has been used for the fabrication of blue light emitting diodes(LEDs), UV photodiodes, etc. and are studied as the material for the devices which can operate in high power, high temperature, and high frequency environment. To fabricate SiC devices, SiC has to be etched and plasma etching has to be used because of the high chemical stability of SiC. In this study, SiC was etched using a magnetic enhanced inductively coupled plasma(MEICP) in fluorine containing gases such as NF3, SF6, and CF4. The etch characteristics of SiC and etch selectivities over mask materials such as photoresist and metals(Cr, Cu, etc.) were also investigated as a function of operating pressure, inductive power, and additive gas(Ar, O2, etc.). The characteristics of the plasmas were investigated using a Langmuir probe and optical emission spectroscopy. Etch profiles of patterned SiC were observed by a scanning electron microscopy.
CP-1-9 Influence of Target-to-Substrate Distance on the Properties of AZO Films by RF Magnetron Sputtering
S.Hun Jeong, Y.-A. Noh, S.-B. Lee, J.-H. Boo (Sungkyunkwan University, South Korea)
Transparent conductive aluminum-doped ZnO (AZO) films were prepared by RF magnetron sputtering on glass substrates with specifically designed ZnO target using high-purity of zinc oxide (99.99 %) and aluminum hydroxide (99.99 %) powders. Systematic study on dependence of target-to-substrate distance (Dts ) on structural, electrical and optical properties of the as-grown AZO films was mainly investigated in this work. XRD shows that highly preferred (002) orientation AZO crystal was grown in parallel to the substrate while the Dts doesn't effected to peak position. With decreasing Dts the growth rate is increased. The XPS shows that zinc has remained with nearly oxidation state and has been attributed to the presence of excess zinc in the films. The Zn/O ratio in AZO films was increased with increasing growth rate in the films. The as-grown AZO films have an average transmittance of above 85 % at the visible region. The resistivity of the film deposited under Dts of 45 mm with 4 wt.% Al(OH)3 doped ZnO in target was about 9.8x10-2cm, showing a semiconductor property.
Time Period MoP Sessions | Topic C Sessions | Time Periods | Topics | ICMCTF2003 Schedule