bluuebunny/crossref_metadata_2025 huggingface dataset:
Electroless copper deposition as a seed layer on TiSiN barrier
Authors: Ee Y. C. , Chen Z. , Xu S. , Chan L. , See K. H. , Law S. B.
Published: July 2004

Electroless deposition of copper as a seeding technology has received considerable attention in back-end-of-line device fabrication. This work explores the effects of plasma processing parameters such as argon gas flow rate and nitrogen plasma treatment time on the properties of electrolessly plated Cu on TiSiN barrier layers. The barrier film was produced by a low-frequency inductively coupled plasma process. The properties of deposited electroless copper are characterized by x-ray diffraction, four-point resistivity probe, atomic force microscopy, and field emission scanning electron microscope. The required palladium activation time is greatly reduced on TiSiN compared to TiN. In both cases there exists a preferred (111) crystal orientation in Cu film and the intensity ratio of I(111)/I(200) is very close. The Cu grain size is within the range of 23–34 nm for 84 nm thick film. It is found that argon gas flow rate does not have a significant effect on the resistivity of electroless copper film on TiSiN. However, increasing nitrogen plasma treatment time reduces the resistivity of copper film. The roughness of plated Cu layer largely follows the one of the underlying TiSiN. Good surface coverage of electroless Cu seed layer on TiSiN has been achieved in our experiment.
Nanoscale fatigue and fracture toughness measurements of multilayered thin film structures for digital micromirror devices
Authors: Wei Guohua , Bhushan Bharat , Jacobs S. Joshua
Published: July 2004

The digital micromirror device (DMD), which lies at the heart of Digital Light Processing™ projection display technology by Texas Instruments, Dallas, Texas, comprises a surface-micromachined array of mirrors on a base CMOS substrate. The nanomechanical properties of the thin-film structures used are important to the performance of the DMD. In this article, the nanoscale fatigue and fracture toughness of the single and multilayered thin film structures which are of interest in DMDs, i.e., TiN/Si, SiO2/Si, Al alloy/Si, TiN/Al alloy/Si, and SiO2/TiN/Al alloy/Si, were measured using nanoindentation techniques. The multilayered thin film structures with hard films on soft interlayer exhibit shorter fatigue life and higher ductility than the corresponding top hard films. The hardness plays an important role in determining the indentation fatigue life. Longer fatigue life is associated with higher hardness. The fracture toughness of TiN/Si and SiO2/Si was measured using the strain energy release method.
Analysis of closed loop control and sensor for a reactive sputtering drum coater
Authors: George M. A. , Craves E. A. , Shehab R. , Knox K.
Published: July 2004

The reactive sputtering process is characterized by a hysteresis of reactive gas concentration and reactive gas flow [Schiller, Thin Solid Films 118, 255 (1984); Affinito and Parsons, J. Vac. Sci. Technol A. 2, 1275 (1984)]. The precise control of the reactive sputtering process requires maintaining operation at points on the hysteresis that ensures the desired high sputter flux and deposited thin film stoichiometry. The hysteresis is highly nonlinear in these preferred operating regimes. The practical challenge of meeting this in a reactive sputtering batch coating system requires a control system that can compensate for changes in reaction rate for various sputtered metals, reactive gas sticking coefficients, and system pumping speed. Closed loop control algorithms that rapidly bring the reactive sputtering system to the desired hysteresis steady state operating point are desired for multilayer applications such as thin film interference filters that require many target starts (and stops). Conventional methods of starting the reactive sputtering process such as temporally ramping target power, voltage or current and target shutters are undesirable for precision thin film interference filters. We present a reactive gas sensor and analysis of the proportional-integral-derivative closed loop control algorithm for an industrial reactive sputtering batch drum coater. The key enabler of the control algorithms is a reactive gas sensor employed on these drum coaters that exhibits a temporal response of several hundred milliseconds. We discuss how elements from control theory applied to the reactive sputtering process can determine what points on the hysteresis will be the most difficult to control and the limits to implementation for an industrial system.
Spatially defined immobilization of biomolecules on microstructured polymer substrate
Authors: Hozumi Atsushi , Saito Takao , Shirahata Naoto , Yokogawa Yoshiyuki , Kameyama Tetsuya
Published: July 2004

Chemically and geometrically defined poly (methyl methacrylate) (PMMA) substrates were employed to spatially immobilize biomolecules. First, we irradiated the PMMA substrate with 172 nm vacuum ultraviolet (VUV) light through a photomask to fabricate on its surface well-ordered arrays of micro/nanowells with a depth of 400 nm or less and an average diameter of 5, 10, or 20 μm. The surface of these wells was chemically reactive due to the formation of oxygen-containing functional groups during VUV irradiation, while the surrounding areas remained unreactive. We were therefore able by chemical vapor deposition to selectively and uniformly chemisorb aminosilane, that is, N-(6-aminohexyl)-3-aminopropyltrimethoxysilane (H2N[CH2]6NHCH2CH2CH2Si[OCH3]3, AHAPS) onto the well surfaces without any marked change in the well’s dimensions, as evidenced by x-ray photoelectron spectroscopy and atomic force microscope. Finally, we characterized the micro/nanowell arrays’ property to immobilize bovine serum albumin (BSA) by utilizing antigen-antibody reactions. BSA antibody conjugated with fluorescein isothiocyanate was employed to visualize BSA adsorbed onto the microstructured sample surface coated with the AHAPS layer. We confirmed by fluorescence microscope that BSA indeed adsorbed onto the surfaces of the individual wells and did not adsorb onto the unirradiated regions between the wells.
Investigation of nanotribological and nanomechanical properties of the digital micromirror device by atomic force microscopy
Authors: Liu Huiwen , Bhushan Bharat
Published: July 2004

The digital micromirror device (DMD) is one of the successfully commercialized devices in the emerging field of microelectromechanical systems. In this study, an atomic force microscope (AFM) was used to characterize the surface roughness and the adhesive forces of landing sites. Micromirror tilting measurements on the DMD chip were made using an AFM to obtain the force required to tilt the micromirror. An asperity contact model was used to analyze the contact area and contact stresses between the spring tip and the landing site. Nanoscale bending tests were conducted on the hinge to measure elastic modulus which was needed in the analysis. These data were used to understand the potential mechanisms for “soft” stuck micromirror occurrences.
Arrays of magnetoresistive sensors for nondestructive testing
Authors: Nazarov Alexey V. , da Silva Fabio C. S. , Pappas David P.
Published: July 2004

Magnetic field distributions were measured for test stripline structures with anisotropic magnetoresistive (AMR), thin film Permalloy sensors. Linear arrays of eight barber-pole-type AMR sensors were used to increase the speed of the imaging and stability of scanning. The magnetic field distributions were converted to the distribution of electric current density in a stripline by inverting Maxwell’s equations.
Field emission device with back gated structure
Authors: Mammana V. P. , Jaeger D. , Shenderova O. , McGuire G. E.
Published: July 2004

Analysis and performance optimization of a back-gated field emission device is provided. The device consists of an anode, electron emitting cathodes and gate electrode that are placed below the cathode (“back gate”). The role of a back gate is to control electron emission from the cathode by changing the voltage on the back gate. The top of the cathode is selectively coated with an electron emissive material/structure that presents better emission properties when compared to the material of the cathode. The role of the cathode geometry, back gate voltage, cathode-gate distance, distance between cathode electrodes, the back gate dielectric, as well as field emission characteristics of the emitting material on the top of a cathode were analyzed using continuum electrostatic simulations. The proposed design significantly facilitates fabrication of the field emitting devices while decreasing the amount of charge lost to the gate and potentially reducing the likelihood of catastrophic discharges.
Photoemission study of the translational energy induced oxidation processes on Cu(111)
Authors: Moritani Kousuke , Okada Michio , Sato Seiichi , Goto Seishiro , Kasai Toshio , Yoshigoe Akitaka , Teraoka Yuden
Published: July 2004

The oxidation processes of Cu(111) with a hyperthermal O2 molecular beam (HOMB) were studied using high-resolution x-ray photoemission spectroscopy in conjunction with a synchrotron radiation source. The O-uptake curves were precisely measured at ∼300 K when irradiating with 2.3 and 0.6 eV HOMB on a Cu(111) surface. A Langmuir-type adsorption model at an oxygen coverage (Θ)⩽0.4 ML describes the kinetics of dissociative adsorption in the HOMB incidence. On the other hand, further inefficient oxidation occurs even for the 2.3 eV HOMB irradiation at Θ⩾0.4 ML. A collision-induced absorption mechanism can interpret the slow oxidation process of Cu(111).
Anisotropic infrared optical properties of GaN and sapphire
Authors: Yu G. , Rowell N. L. , Lockwood D. J.
Published: July 2004

Infrared polarized reflectance at three incidence angles (18°, 45°, and 75°) was measured from 300 to 1200 cm−1 for sapphire and GaN/sapphire at 295 K. The approximately 1.5 μm thick film of GaN was grown directly on c-plane sapphire by metal-organic chemical vapor deposition. The optical anisotropy of the sapphire substrate and GaN film was studied by fitting with a suitable model the five- and three-mode polarized reflectance spectra, respectively, at the three different incident angles all simultaneously. In the procedure, we adopted a fitting technique, i.e., fitting the first numerical derivative of the polarized reflectance spectra to improve the accuracy of the phonon parameters and to overcome the inconsistency between the model and measurement over the whole frequency range. Excellent agreement has been obtained between the measured and fitted first derivative reflectance spectra for both the sapphire and GaN/sapphire samples. The infrared optical parameters thus obtained for sapphire and GaN enhance those reported previously.
Preparation and characterization of magnetron sputtered, ultra-thin Cr0.63Mo0.37 films on MgO
Authors: Meyvantsson I. , Olafsson S. , Johnsen K. , Gudmundsson J. T.
Published: July 2004

We report on the preparation of lattice matched heteroepitaxial films in a dc magnetron sputtering discharge. CrxMo1−x thin films were grown on MgO(1 0 0) substrate, choosing the composition of the binary metal alloy to be x=0.63, so that the film is lattice matched to the substrate when the 〈100〉 orientation of the film is parallel to the 〈110〉 orientation of the substrate. Ex situ x-ray diffraction and low angle x-ray reflectivity measurements were performed to determine the film structure, film thickness, as well as the surface and interface roughness. We determine the optimum growth temperature to be 200 °C. Using this temperature 0.4–15 nm thick films were prepared. The resistivity of the films was measured ex situ using a four-point-probe. The resistivity dropped rapidly with increasing thickness. The resistivity versus thickness data was found to be well described with Namba’s model, which includes film roughness as a parameter.
Interaction between metals and organic semiconductors studied by Raman spectroscopy
Authors: Zahn Dietrich R. T. , Salvan Georgeta , Paez Beynor A. , Scholz Reinhard
Published: July 2004

Silver and indium were deposited onto molecular layers of two perylene derivatives, viz. 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) and N,N′-dimethylperylene 3,4,9,10-dicarboximide (DiMe–PTCDI). The interaction between the metals and the organic semiconductors was probed in situ by Raman spectroscopy. The molecular structure is found to be preserved when Ag or In are deposited onto PTCDA and DiMe–PTCDI layers. For In, this is in contrast to previous suggestions of strong reactivity with PTCDA and covalent bond formation between In and O atoms in PTCDA. However, the molecules having direct contact with the metal are involved in a ground state dynamical charge transfer with different strength for Ag and In, resulting in a breakdown of vibrational selection rules. A significant enhancement of Raman internal vibrational modes is observed both for Ag and In deposition as a result of metal-induced surface enhanced Raman scattering (SERS). The enhancement factors observed for the internal modes reflect a rough morphology of the metal films which is influenced by the morphology of the underlying organic film. Moreover, conclusions regarding the indiffusion of the two metals can be drawn from the comparison of the breakdown of the selection rules for the internal modes and the spectral evolution of the external molecular modes.
Study of the optical properties of SiOxNy thin films by effective medium theories
Authors: Tan X. , Wojcik J. , Mascher P.
Published: July 2004

Silicon oxynitride (SiOxNy) films were deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) and covered the entire composition range from silicon dioxide to silicon nitride. The composition of the films was determined by Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), and elastic recoil detection (ERD). These techniques provide the absolute areal concentrations of all elements, including silicon, oxygen, nitrogen, and hydrogen. Additionally, Fourier transform infrared (FTIR) spectroscopy and ellipsometry measurements were performed for the optical characterization of the thin films. Effective medium theories (EMT) were used to model the optical and compositional properties of the SiOxNy films. The refractive index measured by ellipsometry was compared with theoretical calculations using Maxwell–Garnett and Bruggeman equations. The experimental results agree quite well with model data. It is also shown that the concentration of hydrogen in the films has a major influence on the quality of the agreement.
Pretreatment technique for surface improvement of Ru films in Ru-metalorganic chemical vapor deposition
Authors: Han Hee , Kim Jae Jeong , Yoon Do Young
Published: July 2004

The effects of Pd activation on ruthenium (Ru) films grown by metalorganic chemical vapor deposition (MOCVD) using a bis(ethyl-π-cyclopentadienyl) ruthenium [Ru(EtCp)2] as a precursor were investigated. Displacement-deposited Pd particles on TiN substrate play a role of active sites for Ru nucleation. The growth rate was increased as the decomposition of Ru(EtCp)2 was promoted by Pd activation prior to Ru deposition. Moreover, Pd particles dramatically enhanced Ru nucleation at the early stage and the surface roughness of the films considerably reduced. From these results, the possibility of Pd activation as a pretreatment technique for Ru nucleation in Ru–MOCVD is proposed.
Plasma-assisted growth of bilayer silicon-containing coatings for hardness and corrosion resistance
Authors: Xiao Z. G. , Mantei T. D.
Published: July 2004

Hard corrosion-resistant bilayer coatings were grown in a high-density microwave electron cyclotron resonance discharge. The bilayer coatings consist of a relatively soft (0.6–1.5 GPa) polymer-like coating as the adherent bottom layer and a much harder (8–12 GPa) top layer. The polymer underlayers were grown from 100% octamethylcyclotetrasiloxane (OMCTS) while the hard top layer was either silicon dioxide grown from OMCTS in an oxygen plasma or silicon nitride grown from hexamethyldisiloxane in an ammonia plasma. The bilayer structures combined high surface hardness values with good corrosion resistance, surviving 1800–2600 h in an ASTM B117 salt-fog corrosion test.
Stretchable wavy metal interconnects
Authors: Jones Joyelle , Lacour Stéphanie P. , Wagner Sigurd , Suo Zhigang
Published: July 2004

Buckled, wavy metal stripes are promising candidates for interconnects in flexible and stretchable electronics. To obtain wavy metal films, 5 nm of Cr (for adhesion) and 20 nm of Au were evaporated on polydimethyl siloxane (PDMS) prestretched by 25%. The metals buckle to a wave upon release of the PDMS from the prestretched position. The electrical resistance of the Au was measured as a function of applied tensile strain. Results show the metal remains electrically conductive up to 100% strain and maintains electrical continuity under repeated mechanical deformation. Presented are the sample fabrication, surface topography, and results of experiments conducted on these stretchable wavy metals.
Surface phase transitions and related surface defect structures upon reduction of epitaxial WO3(100) thin films: A scanning tunneling microscopy study
Authors: Li M. , Altman E. I. , Posadas A. , Ahn C. H.
Published: July 2004

The evolution of surface morphology and reconstructions induced by reducing epitaxial WO3(100) thin films on LaAlO3(100) were studied using scanning tunneling microscopy (STM). As the films were reduced the surface transformed from p(2×2) to p(5×2) to p(4×2) to p(3×2) and finally to (1×1); at intermediate stages mixtures of the phases were observed. As the surface structure changed the films became progressively darker indicating a connection between surface structure and bulk reduction. The formation of the p(5×2) and p(4×2) structures from the p(2×2) structure could be explained by the ordering of vacancies created by W5+ migration into the bulk into troughs. The ordered troughs gave the surface a stranded appearance in STM images. As the surface was reduced the troughs narrowed to create the p(3×2) surface; reduction of this surface gave way to a (1×1) surface with all the W ions reduced to 5+. Half-height steps due to crystallographic shear planes intersecting the surface characterized the (1×1) surface. Several defect structures were characteristic of the p(n×2) surfaces including domain boundaries oriented parallel to the strands and along [011], in-plane line defects across strands, wide strands, and crosslinks above strands. Structural models for these defects are proposed based on STM results. The [011] domain boundaries are attributed to the formation of stress domains on a reconstructed surface with uniaxial stress induced by the strands and troughs.
Reaction intermediates in high temperature catalytic water formation studied with cavity ringdown spectroscopy
Authors: Hemdal S. , Johansson Å. , Försth M. , Andersson M. , Rosén A.
Published: July 2004

The rotational temperature and concentration of OH in the gas-phase outside a polycrystalline platinum catalyst has been measured using cavity ringdown spectroscopy. A mixture of H2 and O2 gases was used forming a stagnation point flow field outside the catalyst. The temperature of the catalyst was 1500 K, the total pressure in the chamber was 26 Pa, and the relative hydrogen concentration, αH2, was set to 8%. From a Boltzmann plot, the rotational temperature was determined to be 775±24 K, and the amount of OH was calculated from that temperature to be 1.5±0.2×1012 cm−3, 6.5 mm outside the catalyst. A similar experiment has also been performed using a polycrystalline palladium catalyst. However, due to lower amount of OH in the gas-phase outside the Pd catalyst, the number density could not successfully be determined. In this study we have shown that cavity ringdown spectroscopy successfully can be used to quantify desorbed intermediates within a catalytic reaction.
Stacked polymer patterns imprinted using a soft inkpad
Authors: Kong Y. P. , Tan L. , Pang S. W. , Yee A. F.
Published: July 2004

A soft inkpad imprinting technique to produce stacked micrometer and submicrometer polymer patterns on substrates is presented. A thin soft inkpad is used to coat a polymer film onto the protrusions of a surface treated hard mold. The polymer film on the protrusions of the hard mold is then transferred to a substrate. Simultaneously, a negative pattern of the hard mold is formed on the soft inkpad that may also be transferred to a substrate. Numerical simulations are used to study the mechanisms of pattern transfer by soft inkpad imprinting. With the use of polymer blends, both positive and negative polymeric gratings with 700 nm period were produced. The soft inkpad allows multiple transfers of polymers with similar solubilities to the hard mold since no chemical solution is used for coating. High aspect ratio polymer stacks can be formed without alignment. This capability is an important advantage when forming submicrometer and nanometer multiple-layered polymer structures because current nanoimprint systems have limited overlay accuracy.
Self-organized template formation for quantum dot ordering
Authors: Nötzel Richard , Mano Takaaki , Wolter Joachim H.
Published: July 2004

Ordered arrays of quantum dots (QDs) are created by self-organized anisotropic strain engineering of (In,Ga)As/GaAs quantum wire (QWR) superlattice (SL) templates on exactly oriented GaAs (100) substrates by molecular beam epitaxy (MBE). The well-defined one-dimensional arrays of (In,Ga)As QDs formed on top of these templates due to local strain recognition are of excellent structural and optical quality up to room temperature. The QD arrays thus allow for fundamental studies and device operation principles based on single- and multiple carrier- and photon-, and coherent quantum interference effects.
Effect of substrate temperature on crystal orientation and residual stress in radio frequency sputtered gallium–nitride films
Authors: Kusaka Kazuya , Hanabusa Takao , Tominaga Kikuo , Yamauchi Noriyoshi
Published: July 2004

The crystal orientation and residual stress in gallium nitride (GaN) films deposited on a single-crystal (0001) sapphire substrate using a sputtering system are examined through x-ray diffraction measurements as part of a study of low-temperature sputtering techniques for GaN. The rf sputtering system has an isolated deposition chamber to prevent contamination with impurities, and is expected to produce high-purity nitride films. GaN films are deposited at various substrate temperatures and constant gas pressure and input power. This system is found to produce GaN films with good crystal orientation, with the c axes of GaN crystals oriented normal to the substrate surface. The crystal size of films deposited at high temperature is larger than that deposited at low Ts. All films except that deposited at 973 K exhibit compressive residual stress, and this residual stress is found to decrease with increasing temperature. Finally, the film deposited at 973 K was tinged with white, and the surface contained numerous microcracks.
Effect of thickness on ferroelectric properties of Bi3.25La0.75Ti3O12 thin films on Pt/Ti/SiO2/Si substrates
Authors: Kim Kyoung-Tae , Song Sang-Hun , Kim Chang-Il
Published: July 2004

Ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films were fabricated by a metalorganic decomposition deposition aimed at investigating the thickness effect on ferroelectric properties. Both the grain growth behavior and ferroelectric properties (dielectric constant, remanent polarization) were found to be dependent on the thickness of the BLT thin films. We have found that an optimal film thickness occupies the range of 200–325 nm. The decrease in the film thickness below 200 nm causes a decrease in dielectric constant as well as in remanent polarization. The reasons are decreasing grain size and increasing internal strain probably resulted from the electrode/ferroelectric interfacial layer. The increase in the film thickness above 325 nm also leads to decreasing dielectric constant and remanent polarization, but also to increasing coercive field. This may be explained by a formation of interfacial layer with low dielectric constant as well as by the increase in internal strain as determined by x-ray diffraction analysis.
Amorphous fluorocarbon polymer (a-C:F) films obtained by plasma enhanced chemical vapor deposition from perfluoro-octane (C8F18) vapor. II. Dielectric and insulating properties
Authors: Biloiu Costel , Biloiu Ioana Arabela , Sakai Yosuke , Sugawara Hirotake , Ohta Akitsugu
Published: July 2004

Amorphous fluorocarbon polymer films (a-C:F) have been grown by plasma enhanced chemical vapor deposition from a new precursor, namely perfluoro-octane (C8F18) vapor. The dielectric and insulating properties of the films have been assessed by means of capacitance–voltage and current–voltage characteristics, breakdown voltage measurements, scanning electron microscopy, and ellipsometric analyses. In the investigated frequency range, 120 Hz–1 MHz, the films have a low dielectric constant (≈2.4) and a low dielectric loss (⩽3×10−2). The electrical conduction mechanism is ohmic in the weak electric field regime, with a bulk resistivity of 4×1015 Ω cm, and a trap modulated space charge limited conduction in the strong electric field regime. For a film thickness between 1 and 12 μm, the dielectric strength varies with film thickness according to EB∼h−0.53. For a film thickness of 1 μm the film dielectric strength was 2.7 MV/cm while for 12 μm it decreased to 0.9 MV/cm. Measurements of the breakdown voltage in nitrogen gas in the low pressure regime between a-C:F coated cathode and copper anode showed an enhancement of the breakdown voltage by a factor of 2.5 with respect to the case of copper–copper electrodes.
Properties of high-k/ultrahigh purity silicon nitride stacks
Authors: Shi X. , Shriver M. , Zhang Z. , Higman T. , Campbell S. A.
Published: July 2004

Ultrahigh purity (UHP) silicon nitride (Si3N4) was applied as a barrier layer to reduce the reaction of high-k materials with the underlying silicon channel. UHP Si3N4 was grown by rapid thermal nitridation (RTN) in chemically scrubbed ammonia in an ultrahigh vacuum (UHV) chamber. The grown thickness nearly saturates for nitridation times greater than 10 s. This self-limiting thickness increases by about 0.2 nm per 100 °C nitridation temperature from 500 to 900 °C. In situ Auger show that UHP nitride has less than 1% oxygen contamination. The effective charge density of UHP Si3N4 was found to increase with the thickness of nitride layer. The thinnest nitride layers (0.5 nm) have a charge density of approximately 5×1011 cm−2. The peak mobility of field effect transistors made from such a layer are 180 cm2/V s (n channel) and 50 cm2/V s (p channel). Both are about 70% of the value predicted by the universal curve.
Scanning tunneling microscopy studies of oxide growth and etching on Si(5 5 12)
Authors: Skrobiszewski J. L. , Moore J. C. , Dickinson J. W. , Baski A. A.
Published: July 2004

We have used scanning tunneling microscopy to study how the Si(5 5 12) surface morphology evolves when exposed to oxygen at elevated temperatures, in particular when both oxide nucleation and etching occur simultaneously. This study includes results for sample temperatures of 650 to 750 °C at O2 pressures of ∼5×10−7 Torr and exposures of 50 to 600 L. It is already known that the Si(001) surface is significantly disrupted in this transition regime by etch pits and islands caused by etching around oxide-induced pinning sites. For the high-index Si(5 5 12) surface, no etch pits are found on the terraces, but pyramidal or linear islands are observed on terraces and along step edges. Both types of islands incorporate (113) facets, indicating an enhanced stability of this orientation against etching. The absence of etch pits and the presence of well-defined islands qualitatively distinguish the etching behavior of this high-index surface from its low-index counterparts.
Hydrogen pressure dependence of trench corner rounding during hydrogen annealing
Authors: Kuribayashi Hitoshi , Shimizu Ryosuke , Sudoh Koichi , Iwasaki Hiroshi
Published: July 2004

We have investigated the rounding of micron-sized trenches fabricated on Si(001) substrates during annealing in hydrogen ambient in a temperature range of 1000 to 1100 °C, especially the effect of hydrogen pressure on the rate of rounding. Observing the profiles of the trenches annealed under hydrogen pressures from 10 up to 760 Torr by scanning electron microscopy, we have found that the rate of corner rounding decreases with increasing hydrogen pressure. It was also found that these rates of corner rounding are smaller than that during annealing in atmospheric argon ambient. This result suggests that adsorbed hydrogen suppresses the surface self-diffusion, by which the corner rounding occurs. We present the contour map of corner curvature in the process parameter space of hydrogen-pressure versus annealing temperature for an annealing time of 3 min.
Room temperature synthesis of porous SiO2 thin films by plasma enhanced chemical vapor deposition
Authors: Barranco A. , Cotrino J. , Yubero F. , Espinós J. P. , González-Elipe A. R.
Published: July 2004

Silicon dioxide thin films with variable and controlled porosity have been prepared at room temperature by plasma enhanced chemical vapor deposition in an electron cyclotron resonance microwave reactor with a downstream configuration. The procedure consists of the deposition of successive cycles consisting of a sacrificial organic-polymeric layer and, afterward, a silicon dioxide layer. Toluene and oxygen are used as precursors of the organic layers and Si(CH3)3Cl and oxygen for the SiO2. During deposition of the latter, the organic layer is simultaneously burned off. In these conditions, the release of gases produced by oxidation of the organic-polymeric layer take place while the oxide layer is being deposited. Thus, modification of the nucleation and growing mechanism of the silicon oxide thin film take place. The porosity of the final porous SiO2 thin films increases with the thickness of the sacrificial organic layer. The porous SiO2 films prepared with the aforementioned method are free of carbon and chlorine contamination as confirmed by Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. Depending on their porosity, the SiO2 thin films are either transparent or scattered visible light. The former have refractive index lower than that of thermal silicon dioxide and the latter show membranelike behavior in gas diffusion experiments. All the samples have good adhesion to the substrates used for the deposition, either polished Si wafer, glass plates, or standard porous supports. They have columnar microstructure, as determined by scanning electron microscopy. A preliminary ultraviolet-visible characterization of the optically transparent thin films reveals that transmission of light through glass increases by 7%–8% when the porous silica is deposited on this substrate. These films prove to be very efficient as antireflective coatings and are of interest for photovoltaic and similar applications. It is possible to deposit SiO2 thin films with densities as low as 0.65 g/cm3 (corresponding to a porosity of 70%) by adjusting the thickness of the sacrificial and SiO2 layers. The films with high porosity are promising materials for the fabrication and/or modification of diffusion membranes. The gas adsorption properties and the type of porosity of the SiO2 thin films are assessed by adsorption isotherms of toluene at room temperature measured with a quartz crystal monitor device. The gas permeation properties of the films (when used as membranes) are analyzed by studying the diffusion rate of different gases through them.
Theoretical study on deposition temperature during arc ion plating
Authors: Huang M. D. , Lee Y. P. , Dong C. , Wen L. S.
Published: July 2004

A model, based on the laws of energy conservation, for the estimation of substrate temperature during the process of arc ion plating, has been established by considering only the major influencing factors. The calculated temperatures based on this model turn out to be coincident with the experimental ones at different dc biases. The effects of several experimental parameters are also discussed. Using the established model, the substrate temperatures can be predicted, which is very useful for the relevant engineering applications.
Etching yield of SiO2 irradiated by F+, CFx+ (x=1,2,3) ion with energies from 250 to 2000 eV
Authors: Karahashi Kazuhiro , Yanai Ken-ichi , Ishikawa Kenji , Tsuboi Hideo , Kurihara Kazuaki , Nakamura Moritaka
Published: July 2004

Etching yields of SiO2 have been determined for F+, CFx+ (x=1,2,3) ion irradiation with energy ranging from 250 to 2000 eV using a mass-analyzed ion-beam apparatus that can irradiate a single species ion to sample surfaces under an ultrahigh vacuum condition. The etching yield of CFx+ (x=1,2,3) was enhanced by the chemical effects of the ions, and both carbon and fluorine atoms from the incident ions were significant reactants. For lower energies, the etching yield increased with increasing ion energy. Above 1000 eV, the etching yield was gradually saturated with increasing ion energy. In the low ion energy region, steady etching did not occur, and an amorphous fluorinated carbon (a-C:F) film was deposited on the SiO2 surface. The ion energy region in which a-C:F film deposition occurred decreased with increasing fluorine atoms in incident CFx+ (x=1,2,3) ions.
Atomic layer deposition of hafnium oxide and hafnium silicate thin films using liquid precursors and ozone
Authors: Senzaki Yoshihide , Park Seung , Chatham Hood , Bartholomew Lawrence , Nieveen Wesley
Published: July 2004

Atomic layer deposition (ALD) processes for HfO2 and HfxSi1−xO2 high-k dielectric thin films using liquid precursors and ozone were evaluated. Tetrakis(ethylmethylamino)hafnium (TEMAHf) precursor provides HfO2 films with superior quality as compared to Hf(t-butoxide)4 precursor in terms of deposition rate, purity, and electrical properties of the films. ALD processes for hafnium silicate films have been developed by co-injection of TEMAHf and tetrakis(ethylmethylamino) silicon precursors. Alternating pulses of the Hf/Si precursor vapor mixture and ozone allow process temperatures below 400 °C to grow HfxSi1−xO2 film. The Hf and Si precursors can be converted to vapor for delivery to the deposition chamber either by bubbling an inert carrier gas separately through each liquid or by using a liquid vaporization unit. The co-injection process enables the formation of homogeneous single-layer hafnium silicate films as deposited.
Surface composition and structure of Co3O4(110) and the effect of impurity segregation
Authors: Petitto S. C. , Langell M. A.
Published: July 2004

The Co3O4(110) single crystal surface has been characterized by low energy electron diffraction (LEED), Auger electron spectroscopy, and x-ray photoelectron spectroscopy (XPS). LEED analysis of the clean Co3O4(110) spinel surface shows a well-ordered pattern with sharp diffraction features. The XPS spectra are consistent with stoichiometric Co3O4 as determined by the concentration ratio of oxygen to cobalt (CO/CCo) and spectral peak shape. In particular, the cobalt 2p XPS spectra are characteristic of the spinel structure with Co3+ occupying octahedral sites and Co2+ in tetrahedral sites within the lattice. During prolonged heating at 630 K, bulk impurities of K, Ca, Na, and Cu segregated to the surface. Sodium desorbed from the surface as NaOH at 825 K, potassium and calcium were only removed by sputtering since no desorption from the surface was detected for temperatures up to 1000 K. Copper also disappeared upon heating above 700 K, most likely by desorbing although the possibility of diffusion back into the bulk could not be eliminated. The appearance of copper impurities correlated with Co3O4(110) surface reduction to CoO, and the surface could not be fully reoxidized even upon extended oxygen annealing as long as the copper impurity remained on the surface. Upon removal of the Cu from the near-surface region, the surface was easily reoxidized to Co3O4 by O2.
Self-assembled organic thin films on electroplated copper for prevention of corrosion
Authors: Tan Y. S. , Srinivasan M. P. , Pehkonen S. O. , Chooi Simon Y. M.
Published: July 2004

Self-assembled organic thin films of dodecanethiol (DT), mercaptobenzothiazole (MBT), benzotriazole (BTA), imidazole (IMD) and benzothiazole (BT) are formed by adsorption on the surface of copper thin film used in ultralarge-scale integrated circuits. The films are characterized by x-ray photoelectron spectroscopy. The inhibition of corrosion of these organic thin films is investigated in aerated 0.5 M H2SO4 solutions by electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The presence of these films reduced corrosion by blocking the copper surface from the oxygen dissolved in the acid medium. The relative inhibition efficiencies of these inhibiting agents in preventing copper oxidation are found to be in the order of DT>MBT>BT>BTA>IMD. The effectiveness of the inhibitors increased with the temperature, concentration of the inhibitors, and duration of immersion in the solution. An adsorption model is proposed on the basis of variation of the impedance according to the inhibitor concentration. The stability and packing of the inhibitors on the surface appear to be the most important factors in determining the inhibitive efficiency of the inhibitors.
Luminescent characteristics of Se-doped ZnGa2O4:Mn thin film phosphors grown by pulsed laser ablation
Authors: Jeong J. H. , Bae J. S. , Choi B. C. , Yi S. S. , Holloway P. H.
Published: July 2004

Mn-doped ZnGa2O4−xSex (x=0.00, 0.025, 0.05, 0.075 and 0.10) thin film phosphors have been grown using pulsed laser ablation under various growth conditions. Structural characterization was carried out on a series of ZnGa2O4−xSex:Mn2+ films grown on MgO(100) substrates using Zn-rich ceramic targets. Zn-rich ceramic targets were prepared to compensate for loss of vaporization of Zn during deposition. The oxygen pressure was fixed at 100 mTorr and the substrate temperatures were varied from 500 to 700 °C. Luminescence results indicated that MgO (100) is a promising substrate for the growth of high-quality of ZnGa2O4−xSex:Mn2+ films. The crystallinity and surface roughness of the ZnGa2O4−xSex:Mn2+ films are highly dependent on the growth conditions, in particular on the substrate temperature and composition ratio of targets. The crystallinity of the films improved with Se doping. Incorporation of Se into the ZnGa2O4 lattice led to a remarkable increase of photoluminescence. The highest green emission intensity was observed with ZnGa2O3.925Se0.075:Mn2+ films whose brightness was increased by a factor of 3.1 in comparison with that of ZnGa2O4:Mn2+ films. This phosphor is promising for application in flat panel displays.
Low resistivity polycrystalline ZnO:Al thin films prepared by pulsed laser deposition
Authors: Tanaka Hideki , Ihara Kazuhiko , Miyata Toshihiro , Sato Hirotoshi , Minami Tadatsugu
Published: July 2004

The preparation of low resistivity polycrystalline Al-doped ZnO (AZO) thin films on glass substrates by a pulsed laser deposition method is described, including a description of conditions necessary to obtain low resistivity on the order of 1×10−4 Ω cm. The resistivity of transparent conducting AZO films obtained was affected by both the target sintering conditions and the deposition conditions. A decrease in carrier concentration associated with a increase in deposition temperature is ascribed to an increase of oxygen content in the films, resulting from enhancement of oxidation on the substrate surface. An increase in Hall mobility associated with increases of either the deposition temperature or film thickness is attributed to imperfections of the ZnO lattice, as evidenced by improvement of the crystallinity such as an increase of crystallite size. It was found that the mobility is also greatly influenced by a combination of ionized impurity scattering and grain boundary scattering or dislocation scattering. In particular, carrier transport, even in AZO films with high mobility above approximately 30 cm2/V s as well as a carrier concentration on the order of 1020–1021 cm−3, was found to be affected by imperfections of the ZnO lattice.
Valence band x-ray photoelectron spectroscopic studies of phosphorus oxides and phosphates
Authors: Gaskell K. J. , Smith M. M. , Sherwood P. M. A.
Published: July 2004

This article reports the results of a continuing study focused on preparing novel surface chemistries on metal surfaces and the study of phosphorus oxygen-containing compounds. In this article we demonstrate the ability of valence band photoelectron spectroscopy to be able to distinguish between three different crystal structures of phosphorus pentoxide, with the differences interpreted using band structure calculations. The spectral differences are highlighted by the use of difference spectra, with the principal features of the difference spectra being reproduced by difference spectra generated from the calculated spectra. Core-level studies are of little use for differentiating between such similar compounds, while valence band photoemission has been found to be particularly effective at identifying subtle differences in surface chemistry. The ability of valence band x-ray photoelectron spectroscopy to distinguish between different phosphate species is exploited to investigate the formation of oxide-free phosphate, phosphite, hypophosphite, and acid phosphate films. These thin (<100 Å) oxide-free films are studied using valence band photoemission and interpreted using both band structure and cluster calculations which show the films to contain different types of phosphate species.
Characteristics of rapid-thermal-annealed LiCoO2 cathode film for an all-solid-state thin film microbattery
Authors: Kim Han-Ki , Yoon Young Soo
Published: July 2004

We report on the fabrication of a LiCoO2 film for an all-solid-state thin film microbattery by using a rapid-thermal-annealing (RTA) process. The LiCoO2 films were grown by rf magnetron sputtering using a synthesized LiCoO2 target in a [O2/(Ar+O2)] ratio of 10%. Scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) analysis results showed that the surface layer on the as-deposited LiCoO2 film was completely removed by rapid thermal annealing process in oxygen ambient for 20 min. In addition, the thin film microbattery fabricated with the annealed LiCoO2 film shows fairly stable cyclability with a specific discharge capacity of 56.49 μAh/cm2 μm. These results show the possibility of the RTA LiCoO2 film and rapid thermal annealing process being a promising cathode material and annealing process for thin film microbatteries, respectively.
Epitaxial Si/Si(001) thin films obtained by solid phase crystallization
Authors: Kim H. J. , Jeon S. H. , Jeon T. Y. , Noh D. Y.
Published: July 2004

We found that hydrogenated amorphous Si/Si(001) thin films of thickness less than about 1000 Å crystallize into epitaxial silicon during solid phase crystallization. The epitaxial solidification is in contrast to the formation of polycrystalline silicon of thicker amorphous films. The structural properties of the epitaxial Si films were characterized by synchrotron x-ray scattering and transmission electron microscopy. The crystalline order in vertical direction is coherent throughout the film thickness, and the surface remains smooth. There were significant structural defects localized at the interface that distinguish the epilayer from the substrate.
Electrical characterization of B10 doped diamond irradiated with low thermal neutron fluence
Authors: Reed M. L. , Reed M. J. , Jagannadham K. , Verghese K. , Bedair S. M. , El-Masry N. , Butler J. E.
Published: July 2004

A sample of B10 isotope doped diamond was neutron irradiated to a thermal fluence of 1.3×1019 neutron cm−2. The diamond sample was cooled continuously during irradiation in a nuclear reactor. Li7 is formed by nuclear transmutation reaction from B10. Characterization for electrical conductance in the temperature range of 160 K<T<600 K was performed on an unirradiated B10 doped sample and the B10 doped and irradiated sample. The unirradiated diamond sample showed p-type conductance at higher temperature (T>200 K) and p-type surface conductance at lower temperature (T<200 K). The irradiated sample showed decreasing conductance below 230 K and increasing conductance above 230 K with increasing temperature. Furthermore, the conductance showed a decrease above 400 K followed by an increase above 500 K. The observed behavior below 400 K with increase in temperature is interpreted in terms of compensation of surface p-type carriers by n-type bulk carriers generated from Li7 that is formed by nuclear transmutation reaction from B10 atoms. Also, compensation of n-type carriers from Li7 by p-type carriers from B10 is used to interpret the conductance above 400 K. A low concentration of radiation induced defects, absence of defect complexes, and the low activation energy of n-type Li7 are thought responsible for the observed variation of conductance in the irradiated diamond. The present results illustrate that neutron transmutation from B10 doped diamond is a useful method to achieve n-type conductivity in diamond.
Microstructure of plasma-deposited SiO2/TiO2 optical films
Authors: Larouche Stéphane , Szymanowski Hieronim , Klemberg-Sapieha Jolanta E. , Martinu Ludvik , Gujrathi Subhash C.
Published: July 2004

SiO 2 and TiO2, with their high refractive index contrast, are interesting candidates for the fabrication of graded-index optical filters. In this work, SiO2/TiO2 mixtures were prepared by plasma-enhanced chemical vapor deposition from SiCl4 and TiCl4. By controlling the gas flow ratio, it is possible to obtain coatings with refractive index values between 1.48, for SiO2, and 2.35, for TiO2, and with an extinction coefficient below 10−4 in the visible and near-infrared regions. The optical properties of the mixtures do not respect the Bruggeman effective medium approximation that supposes two separate phases. Using a combination of x-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and elastic recoil detection, we demonstrate that SiO2/TiO2 is a single-phase material. Two separate phases can develop at certain compositions by annealing-induced precipitation.
Etching properties of lead–zirconate–titanate thin films in Cl2/Ar and BCl3/Ar gas chemistries
Authors: Koo Seong-Mo , Kim Dong-Pyo , Kim Kyoung-Tae , Song Sang-Hun , Kim Chang-Il
Published: July 2004

Etching characteristics of lead–zirconate–titanate (PZT) thin films fabricated by the sol–gel process were investigated using Cl2/Ar and BCl3/Ar inductively coupled plasma, respectively. The maximum etch rate of PZT thin films was obtained: Cl2 (70%)/Ar (30%) and BCl3 (70%)/Ar (30%) gas mixing ratio. The maximum etch rate was 160 nm/min at Cl2 (70%)/Ar (30%) and 179 nm/min at BCl3 (70%)/Ar (30%). Also, the etch rate was measured by varying the etching parameters such as rf power, dc-bias voltage, and chamber pressure. As rf power was raised, the etch rate of the PZT thin films increased in both Cl2/Ar and BCl3/Ar gas conditions. The increase of dc-bias voltage increases the PZT etch rate, and as the chamber pressure increases, the etch rate of PZT films decreases. Plasma diagnostics were performed using a Langmuir probe.