Showing papers on "Sputter deposition published in 2009"

21.2: Al and Sn-Doped Zinc Indium Oxide Thin Film Transistors for AMOLED Back-Plane

Abstract: We have fabricated the transparent bottom gate TFTs using Al and Sn-doped zinc indium oxide (AT-ZIO) as an active layer. The AT-ZIO active layer was deposited by RF magnetron sputtering at room temperature, and AT-ZIO TFT showed a field effect mobility of 15.6 cm2/Vs even before annealing. The mobility increased with increasing In2O3 content and post-annealing temperature. The AT-ZIO TFT exhibited afield effect mobility of 33 cm2/Vs, a sub-threshold swing of 0.08 V/dec, and an on/off current ratio of more than 109 after Al2O3 passivation and post-annealing. We have fabricated AMOLED panels with the bottom gate AT-ZIO TFT back-plane successfully.

Mg doping of thermochromic VO2 films enhances the optical transmittance and decreases the metal-insulator transition temperature

Abstract: Thermochromic films of MgxV1−xO2 were made by reactive dc magnetron sputtering onto heated glass. The metal-insulator transition temperature decreased by ∼3 K/at. %Mg, while the optical transmittance increased concomitantly. Specifically, the transmittance of visible light and of solar radiation was enhanced by ∼10% when the Mg content was ∼7 at. %. Our results point at the usefulness of these films for energy efficient fenestration.

Plasma atomic layer deposition system and method

Abstract: An improved gas deposition chamber includes a hollow gas deposition volume formed with a volume expanding top portion and a substantially constant volume cylindrical middle portion. The hollow gas deposition volume may include a volume reducing lower portion. An aerodynamically shaped substrate support chuck is disposed inside gas deposition chamber with a substrate support surface positioned in the constant volume cylindrical middle portion. The volume expanding top portion reduces gas flow velocity between gas input ports and the substrate support surface. The aerodynamic shape of the substrate support chuck reduces drag and helps to promote laminar flow over the substrate support surface. The volume reducing lower portion helps to increase gas flow velocity after the gas has past the substrate support surface. The improved gas deposition chamber is configurable to 200 mm diameter semiconductor wafers using ALD and or PALD coating cycles. An improved coating method includes expanding process gases inside the deposition chamber prior to the process gas reaching surfaces of a substrate being coated. The method further includes compressing the process gases inside the deposition chamber after the process gas has flowed past surfaces of the substrate being coated.

Epitaxial Mn2.5Ga thin films with giant perpendicular magnetic anisotropy for spintronic devices

Abstract: We report on epitaxial growth and magnetic properties of Mn2.5Ga thin films, which were deposited on Cr/MgO single crystal substrates by magnetron sputtering. X-ray diffraction results revealed the epitaxial relationships as Mn2.5Ga(001)[100]∥Cr(001)[110]∥MgO(001)[100]. The presence of (002) and (011) superlattice peaks indicates that the films were crystallized into DO22 ordered structures. The perpendicular magnetic anisotropy (PMA) properties were found to be related to the extent of DO22 chemical ordering. A giant PMA (Kueff=1.2×107 erg/cm3) and low saturation magnetization (Ms=250 emu/cm3) can be obtained for the film with highest chemical ordering parameter (S=0.8).

Structures and properties of hard and superhard nanocomposite coatings

Abstract: Various approaches to creating multicomponent nanocomposite coatings of high and superhigh hardness (from ≈30 to 100–120 GPa) are reviewed with particular emphasis placed on mechanisms underlying the increase in hardness in thin (≤10 μm) coatings. The deposition technologies considered include magnetron sputtering, ion beam-assisted and vacuum arc depositions. A classification of hard and superhard coatings with high thermal stability is given. Possible applications of such nanostructured coatings are discussed and prospects for the field are outlined.

Giant tunneling magnetoresistance up to 330% at room temperature in sputter deposited Co2FeAl/MgO/CoFe magnetic tunnel junctions

Abstract: Magnetoresistance ratio up to 330% at room temperature (700% at 10 K) has been obtained in a spin-valve-type magnetic tunnel junction (MTJ) consisting of a full-Heusler alloy Co2FeAl electrode and a MgO tunnel barrier fabricated on a single crystal MgO (001) substrate by sputtering method. The output voltage of the MTJ at one-half of the zero-bias value was found to be as high as 425 mV, which is the largest reported to date in MTJs using Heusler alloy electrodes. The present finding suggests that Co2FeAl may be one of the most promising candidates for future spintronics devices applications.

Tribological investigation of adaptive Mo2N/MoS2/Ag coatings with high sulfur content

Abstract: Adaptive nanocomposite Mo2N/MoS2/Ag coatings were deposited on Inconel and silicon substrates by magnetron sputtering with individual targets of Mo, MoS2 and Ag. The tetragonal β-Mo2N structure in addition to Ag and MoS2 phases were detected using X-ray diffraction. The elemental composition of the coatings was investigated using Auger electron spectroscopy. The tribological properties of the coatings were studied at room temperature (RT), 350, and 600 °C against Si3N4 balls. The lowest friction coefficients that were obtained were 0.4, 0.3, and 0.1 at RT, 350 °C, and 600 °C, respectively. The average friction coefficient was maintained at 0.1 for more than 300,000 cycles at 600 °C due to the formation of lubricious silver molybdate phases at the contact surfaces. Three types of silver molybdate phases were detected by both X-ray diffraction and micro-Raman spectroscopy in the wear tracks, namely, Ag2Mo4O13, Ag2Mo2O7 and Ag2MoO4 depending on the Mo and Ag contents in the coatings. The superior performance of all three compounds is due to their layered structure with weaker Ag–O bridging bonds. These relatively weak bonds may shear or even break easily at high temperatures to account for the observed friction reduction.

Resistive switching characteristics of ZnO thin film grown on stainless steel for flexible nonvolatile memory devices

Abstract: This paper reports a resistive switching device of Au/ZnO/stainless steel (SS) and its applicability as a flexible resistive random access memory (ReRAM). The Au/ZnO/SS structure was fabricated by radio frequency sputtering deposition of a ZnO thin film on the SS substrate. The fabricated device showed stable unipolar and bipolar resistive switching behaviors with reliable switching responses over 100 cycles. The device performance was not degraded upon bending, which indicates high potential for flexible ReRAM applications.

Effects of nitrogen content on structure and mechanical properties of multi-element (AlCrNbSiTiV)N coating

Abstract: AlCrNbSiTiV metallic and nitride films were deposited by reactive radio-frequency unbalanced magnetron sputtering. The composition, microstructure and mechanical properties of the coatings deposited at different nitrogen flow rates were evaluated. The deposited AlCrNbSiTiV metallic film has an amorphous structure. The nitride films, regardless of the nitrogen flow ratio, were found to have only an FCC structure register on the XRD profiles. A Stoichiometric nitride ratio, i.e. (Al,Cr,Nb,Si,Ti,V) 50 N 50 is attained for a nitrogen flow ratio ( R N ) of 10% and higher. At the lowest nitrogen flow ratio there is a preferred (200) orientation; however the films become less textured at higher nitrogen flow ratios. Nano-grained structures are obtained for all flow ratios, with grain sizes ranging from 8.7 to 12.3 nm. At the highest nitrogen flow rates the coatings have a compressive stress of around 4.5 GPa. The (Al,Cr,Nb,Si,Ti,V) 50 N 50 nitride coatings have both a high hardness and elastic modulus of 41 and 360 GPa, respectively. The maximum H / E ratio occurs at a nitrogen flow ratio of 20%.

High mobility amorphous zinc oxynitride semiconductor material for thin film transistors

Abstract: Zinc oxynitride semiconductor material is produced through a reactive sputtering process in which competition between reactions responsible for the growth of hexagonal zinc oxide (ZnO) and for the growth of cubic zinc nitride (Zn3N2) is promoted. In contrast to processes in which the reaction for either the oxide or the nitride is dominant, the multireaction process yields a substantially amorphous or a highly disordered nanocrystalline film with higher Hall mobility, 47 cm2 V−1 s−1 for the as-deposited film produced at 50 °C and 110 cm2 V−1 s−1 after annealing at 400 °C. In addition, it has been observed that the Hall mobility of the material increases as the carrier concentration decreases in a carrier concentration range where a multicomponent metal oxide semiconductor, indium–gallium–zinc oxide, follows the opposite trend. This indicates that the carrier transports in the single-metal compound and the multimetal compound are probably dominated by different mechanisms. Film stability and thin film tran...

Widely transparent electrodes based on ultrathin metals

Abstract: Transparent electrodes made of single-component ultrathin (<10 nm) metal films (UTMFs) are obtained by sputtering deposition. We show that the optical transparency of the deposited films (chromium and nickel) is comparable to that of indium tin oxide (ITO) in the visible and near-infrared range (0.4-2.5 microm), while it can be significantly higher in the ultraviolet (175-400 nm) and mid-infrared (2.5-25 microm) regions. Despite their very small thickness, the deposited UTMFs are also uniform and continuous over the 10 cm substrate, as it is confirmed by the measured low electrical resistivity. The excellent optical and electrical properties, stability, compatibility with active materials, process simplicity, and potential low cost make UTMFs high-quality transparent electrodes for the optoelectronics industry, seriously competing with widely used transparent conductive oxides, such as ITO.

Use of a biased precoat for reduced first wafer defects in high-density plasma process

Abstract: According to various embodiments, the present teachings include methods for reducing first wafer defects in a high-density plasma chemical vapor deposition process. In an exemplary embodiment, the method can include running a deposition chamber for deposition of film on a first batch of silicon wafers and then cleaning interior surfaces of the deposition chamber. The method can further include inserting a protective electrostatic chuck cover (PEC) wafer on an electrostatic chuck in the deposition chamber and applying power to bias the PEC wafer while simultaneously precoating the deposition chamber with an oxide. The exemplary method can also include re-starting the deposition chamber for deposition of film on a second batch of silicon wafers.

Effect of Ag thickness on electrical transport and optical properties of indium tin oxide–Ag–indium tin oxide multilayers

Abstract: We report the dependence of electronic and optical properties on the Ag thickness in transparent conductive indium tin oxide (ITO)-Ag-ITO (IMI) multilayer films deposited on polyethylene naphthalate flexible substrate by sputtering at room temperature. The electrical properties (such as carrier concentration, mobility, and resistivity) changed significantly with incorporation of Ag between the ITO layers. Comparison of sheet resistance of the IMI multilayers and the calculated sheet resistance of the Ag midlayer indicates that most of the conduction is through the Ag film. The critical thickness of Ag to form a continuous conducting layer is found to be 8 nm using electrical and optical analysis. A conduction mechanism is proposed to elucidate the mobility variation with increased Ag thickness. Carrier transport is limited by either interface scattering or grain-boundary scattering depending on the thickness of the Ag midlayer. Interface scattering is dominant for thinner (5.5–7 nm) Ag and grain-boundary ...

Enhanced p-type conductivity and band gap narrowing in heavily Al doped NiO thin films deposited by RF magnetron sputtering.

Abstract: Stoichiometric NiO, a Mott–Hubbard insulator at room temperature, shows p-type electrical conduction due to the introduction of Ni2+ vacancies (VNi'') and self-doping of Ni3+ ions in the presence of excess oxygen. The electrical conductivity of this important material is low and not sufficient for active device fabrication. Al doped NiO thin films were synthesized by radio frequency (RF) magnetron sputtering on glass substrates at a substrate temperature of 250 °C in an oxygen + argon atmosphere in order to enhance the p-type electrical conductivity. X-ray diffraction studies confirmed the correct phase formation and also oriented growth of NiO thin films. Al doping was confirmed by x-ray photoelectron spectroscopic studies. The structural, electrical and optical properties of the films were investigated as a function of Al doping (0–4 wt%) in the target. The room temperature electrical conductivity increased from 0.01–0.32 S cm −1 for 0–4% Al doping. With increasing Al doping, above the Mott critical carrier density, energy band gap shrinkage was observed. This was explained by the shift of the band edges due to the existence of exchange and correlation energies amongst the electron–electron and hole–hole systems and also by the interaction between the impurity quasi-particle system.

Reactive sputter deposition of TiN layers: modelling the growth by characterization of particle fluxes towards the substrate

Abstract: The growth of reactively sputtered TiN films is discussed. First, an overview of the existing models in the literature that describe the development of the orientation and microstructure is given. Then, these models are critically confronted with the results of experiments published in the literature and performed by the authors. The latter experiments focus especially on the determination of the energy flux and atomic N/Ti flux towards the substrate and lead to the conclusion that these fluxes towards the substrate play a key role in the growth of the TiN films. This relation between these fluxes and the microstructure of the TiN films gives further evidence to the previously published extended structure zone model.

An amorphous Si thin film anode with high capacity and long cycling life for lithium ion batteries

Abstract: A Si thin film of thickness 275 nm was deposited on rough Cu foil by magnetron sputtering for use as lithium ion battery anode material. X-ray diffraction (XRD) and TEM analysis revealed that the Si thin film was completely of amorphous structure. The electrochemical performance of the Si thin film was investigated by cyclic voltammetry and constant current charge/discharge test. The film exhibited a high capacity of 3,134 mAh g−1 at 0.025 C rate. The capacity retention was 61.3% at 0.5 C rate for 500 cycles. An island structure formed on the Cu foil substrate after cycling adhered to the substrate firmly and provided electrical connection. This is the possible reason for the long cycling life of Si thin film anode. Moreover, the cycling performance was further improved by annealing at 300 °C. The Li+ diffusion coefficients (D 0) of Si thin film, measured by cyclic voltammetry, are 1.47 × 10−9 cm2 s−1 and 2.16 × 10−9 cm2 s−1 for different reduced peaks.

Effective surface passivation of crystalline silicon by rf sputtered aluminum oxide

Abstract: In recent years, excellent surface passivation has been achieved on both p-type and n-type surfaces of silicon wafers and solar cells using aluminum oxide deposited by plasma-assisted atomic layer deposition. However, alternative deposition methods may offer practical advantages for large-scale manufacturing of solar cells. In this letter we show that radio-frequency magnetron sputtering is capable of depositing negatively-charged aluminum oxide and achieving good surface passivation both on p-type and n-type silicon wafers. We thus establish that sputtered aluminum oxide is a very promising method for the surface passivation of high efficiency solar cells. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

On the relationship between the peak target current and the morphology of chromium nitride thin films deposited by reactive high power pulsed magnetron sputtering

Abstract: High power pulsed magnetron sputtering (HPPMS) is used to deposit CrN films without external heating at different peak target currents, while the average current is kept constant. Films are also grown by dc magnetron sputtering (dcMS), for reference. The plasma properties, the deposition rate and the morphology of the films are investigated. The plasma analysis reveals that HPPMS provides higher fluxes of ionized species (both gas and sputtered) to the growing film, as compared with dcMS. In addition, the ionic bombardment during HPPMS increases, when the peak target current is increased. The HPPMS films exhibit changes of the density and the surface roughness as the peak target current increased, while the deposition rate decreases drastically. Furthermore, it is found that different thin-film morphologies are obtained starting from a porous columnar morphology for the dcMS films, which turns to a dense columnar one at low peak target currents and ends up to a featureless morphology at high peak target currents for the films grown by HPPMS. A new structure zone model specific for high ionization sputtering is, therefore, outlined.