bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of cross-sectional transmission electron microscopy specimens of obliquely deposited magnetic thin films on a flexible tape
Authors: Keim Enrico G. , Bijker Martin D. , Lodder J. Cock
Published: July 2002

In this article a method is described for preparing cross sections of obliquely deposited metal thin films on polymer substrates for transmission electron microscopy (TEM) observation. The layers of interest are brittle in nature and therefore it is difficult to obtain suitable TEM samples with conventional methods. Apart from the sample preparation method some details of the deposition technique will be elucidated.
Understanding the evolution of trench profiles in the via-first dual damascene integration scheme
Authors: Kropewnicki Tom , Doan Kenny , Tang Betty , Björkman Claes
Published: July 2002

The introduction of copper interconnects into integrated circuits has increased the use of dual damascene dielectric etch applications because copper films are difficult to plasma etch. Fencing and faceting around the via hole during the trench etch of the via-first dual damascene integration scheme are particularly detrimental and can lead to problems during copper metallization and ultimately to device failure. Therefore, it is imperative that the evolution of these features be understood so that they can be avoided. In this article we will begin with an overview of the via-first dual damascene integration scheme. Experimental results will then be presented that indicate the evolution of these features is heavily dependent upon the existing via profile and whether bottom antireflection coating and/or photoresist is in the via hole prior to starting the trench etch. An empirical model for fence formation was then confirmed by a simple profile simulator written in Visual Basic. Finally, several options for avoiding the evolution of fencing and faceting during the trench etch will be proposed.
Cornell Electron Storage Ring phase-III interaction region vacuum chamber
Authors: He Yun , Li Yulin , Mistry Nariman B. , Greenwald Shlomo
Published: July 2002

Two 115 in. long copper ultrahigh vacuum (UHV) chambers for the Cornell Electron Storage Ring (CESR) interaction region were fabricated. These chambers are a part of the phase-III upgrade project for the CESR storage ring. They incorporate several novel features including a remotely engaging differentially pumped Viton O ring sealed UHV flange, two rf shielded bellows joints, and inner stepped masking for synchrotron radiation. The fabrication of these chambers incorporates multistage electron beam welding to maintain the strict tolerance required for installation through superconducting and permanent quadrupole magnets. Before final welding, a series of electron beam welding setup tests were done to work out a welding procedure for optimizing the welding parameters and avoiding contamination in the weld zone. In this article we will describe the design, fabrication, welding, leak checking, and final UHV performance testing of these chambers.
Determination of magnetostriction for spin-valve devices with 5.0 and 10.0 nm Permalloy layers
Authors: Gafron T. J. , Russek S. E. , Burkett S. L.
Published: July 2002

The objective of this study is to determine the extent of magnetostriction in spin valves. Spin valves were fabricated on a silicon substrate using dc magnetron sputter deposition techniques with the following structure: Ta5.0/NiFe5.0 or 10.0/Co1.0/Cu3.0/Co3.0/Ru0.6/Co2.0/FeMn10.0/Ta5.0, where the subscripts denote the layer thickness in nanometers. The Permalloy composition used in these studies was Ni80Fe20. Spin valves were created in a serpentine shape to maximize the total magnetostriction (ΔL/L) by increasing the device length per die area. Device widths of between 1 and 40 μm with lengths of 1000–40 000 μm were fabricated. Devices were subjected to an external magnetic field while a mechanical force was applied to the backside of the substrate. An increase in the anisotropy field Hk, is observed with increasing stress. This increase is observed for all devices tested but is more distinct for those containing the 5.0 nm Permalloy. Results show that maximum magnetostriction occurs abruptly at lower stress values for the 10.0 nm Permalloy while magnetostriction for the 5.0 nm Permalloy occurs gradually over a wider range of stress values. Magnetoresistance measurements also show an inverse relationship between applied stress and (ΔR/R) performance. Magnetostriction analysis becomes critical as both device complexity and integration levels increase.
Interaction of chlorodifluoromethane with ultrathin solid water films
Authors: Safarik D. J. , Meyer R. J. , Mullins C. B.
Published: July 2002

The kinetics and dynamics of chlorodifluoromethane (CHF2Cl) adsorption on and desorption from 30-bilayer-thick amorphous solid water (ASW) and crystalline ice (CI) films were studied utilizing molecular beam techniques and thermal desorption spectroscopy. The adsorbed state and desorption kinetics of CHF2Cl are sensitive to the surface structure and, hence, the degree of crystallinity of ice. Chlorodifluoromethane binds more strongly to CI than ASW and desorbs at a higher temperature during thermal desorption spectroscopy (TDS), altering the spectrum line shape and allowing differentiation between the two phases. Adsorbed states and thus the TDS line shape also respond to structural changes on the ASW surface prior to the onset of crystallization. The value of the condensation coefficient (α), a measure of CHF2Cl adsorption kinetics and dynamics, is high on both surfaces (∼1). However, a small but reproducible variation of α with the phase of solid water can be used to distinguish ASW from CI. The sensitivity of CHF2Cl adsorption and desorption to ice surface structure can contribute information about the phase and morphology of bulk ice, provided that the structure of the surface reflects that of the bulk.
Supermagnetron plasma chemical vapor deposition and qualitative analysis of electrically conductive diamond-like amorphous carbon films
Authors: Kinoshita Haruhisa , Yoshida Masahiro
Published: July 2002

Using the i-C4H10/N2 supermagnetron plasma chemical vapor deposition method, electrically conductive diamond-like amorphous carbon (DAC) films with nitrogen (DAC:N) were formed on Si and SiO2 wafers. Resistivity and hardness were measured as a function of N2 concentration, rf power, total gas pressure, and wafer stage temperature. With an increase in the N2 concentration (up to 70%), rf power, and wafer stage temperature, DAC:N film resistivity decreased. Fourier transform infrared spectroscopy measurements revealed that an increase in electrical conductivity was attributed to the creation of C–N, C≡N, and N–H bonds in DAC:N films. By preheating the wafers using H2-plasma cleaning, the resistivity of the DAC:N film decreased with an increase in H2-plasma rf power. Using a preheated wafer, the lowest resistivity of 0.034 Ω cm was obtained at an N2 concentration of 65% and upper- and lower-electrode rf powers of 1 kW/1 kW.
Self-organization of large-area periodic nanowire arrays by glancing incidence ion bombardment of CaF2(111) surfaces
Authors: Batzill Matthias , Bardou François , Snowdon Ken J.
Published: July 2002

The fabrication of well-ordered nanowire arrays over large areas is a challenge with many potential applications. Here we report a novel glancing incidence ion beam assisted self-organization approach to form periodic wire arrays over large areas on a CaF2(111) substrate. Preferential erosion of fluorine by the 4.5 keV Ar+ ion beam creates a surface enriched in calcium. The calcium self-organizes in elongated island structures of preferential width and separation. If the sample is irradiated along a fixed azimuth we observe nanowires with ∼10 nm periodicity and wire lengths of at least several micrometers oriented along the azimuthal direction of ion beam incidence. Electrical conductivity measurements reveal an anisotropy in conductivity of at least three orders of magnitude.
Simulation of the production of atomic hydrogen in a low-pressure-arc-discharge-based source
Authors: Kagadei V. A. , Kozyrev A. V. , Proskurovsky D. I. , Osipov I. V.
Published: July 2002

A model is proposed to simulate the production of atomic hydrogen in a low-pressure arc discharge. As a first step of simulation, the electron and ion densities, the currents of ions and fast and plasma electrons, and the currents of thermionic emission and secondary electrons have been calculated and then, based on the criterion for self-sustaining of the discharge current, calculations of the current–voltage characteristics are in good agreement with those obtained experimentally. The second step of simulation involved calculations of the atomic hydrogen production rates. The model takes into account the following mechanisms for the generation and death of hydrogen atoms: impact dissociation of molecules by fast electrons, dissociation by plasma thermal electrons, dissociation at the surface of a self-heating cathode, and recombination of atoms at cold walls of a discharge cell. A theoretical analysis has shown that the three channels for the generation of atomic hydrogen make comparable contributions to the average rate of generation of atomic particles. Comparison of experimental and calculated dependences of the atomic hydrogen density on the discharge parameters shows that the proposed model provides an adequate description of the process of production of atomic hydrogen.
Improved etch characteristics of SiO2 by the enhanced inductively coupled plasma
Authors: Cho S.-B. , Song H.-Y. , Park S.-G. , O B.-H.
Published: July 2002

The generation of active species for silicon dioxide etch and the formation of passivation layers on Si or photoresist is important for etching contact holes of high aspect ratio in sub-half-micron technology. Some methods use a process gas with high C/F ratio chemistry, such as C4F8, and/or apply a pulsed plasma technique, or radical control by chamber-wall modification. As a simple novel method, enhanced inductively coupled plasma (E-ICP) is expected to control the plasma characteristics by changing its E-ICP frequency; we tested the feasibility of using E-ICP for the process of contact hole etching. Scanning electron microscope images of etched profiles for micropatterns of 1 and 0.3 μm are shown to compare to the results by CW-ICP, magnetized-ICP, and E-ICP.
Preparation and characterization of p-type Sb2Te3 and n-type Bi2Te3 thin films grown by coevaporation
Authors: Zou Helin , Rowe D. M. , Min Gao
Published: July 2002

p -type antimony telluride thin films and n-type bismuth telluride thin films have been deposited by coevaporation on glass substrates. The conditions for deposition have been investigated as a function of substrate temperature (Ts), flux ratio (Fr=F(Te)/F(Sb, Bi)) and optimized to achieve a high thermoelectric power factor. The quality of deposited films, e.g. structure, composition and morphology, has been examined by x-ray diffraction, energy dispersive x-ray analysis, flame atomic absorption spectroscopy, and with an atomic force microscope. The thermoelectric properties of the thin films have been evaluated by room temperature measurement of the Seebeck coefficient, Hall coefficient, and electrical resistivity. Both the crystallinity and the transport properties are strongly affected by nonstoichiometry with the highly stoichiometric samples exhibiting a high crystallinity and high thermoelectric power factor. The Seebeck coefficient and electrical conductivity of p-type Sb2Te3 thin film (αp, σp) and n-type Bi2Te3 thin films (αn, σn) were found to be about 185 μV/K, 0.32×103 Ω−1 cm−1 and −228 μV/K, 0.77×103 Ω−1 cm−1, respectively. The results indicate that good quality antimony telluride and bismuth telluride thin films grown by coevaporation are promising candidate materials for use in the fabrication of micro-Peltier modules.
Atomic force microscopy studies of self-assembled Si1−xGex islands produced by controlled relaxation of strained films
Authors: Bashir R. , Chao K.-J. , Kabir A. E.
Published: July 2002

Self-assembled Si1−xGex islands were studied in detail using atomic force microscopy. The self-assembled Si1−xGex islands were formed by a novel two-step process. First, highly strained Si1−xGex thin films (with x∼0.4) were selectively grown on a silicon wafer by chemical vapor deposition at 650 °C. The growth was followed by an annealing step performed in hydrogen at 750 °C at reduced pressure conditions for specific times. The size and distribution of the islands was found to be a function of the annealing conditions and an ordered pattern could be achieved with specific annealing conditions. This growth process shows a new way of creating device islands, which are confined within oxide regions and could be ordered, for applications in optical and electronic devices on silicon.
Growth of in situ CoSi2 layer by metalorganic chemical vapor deposition on Si tips and its field-emission properties
Authors: Wook Han Byung , Sung Rhee Hwa , Tae Ahn Byung
Published: July 2002

We prepared Si emitters coated with a metalorganic chemical vapor deposited CoSi2 layer to improve emission properties. The CoSi2 layer was grown in situ by reactive chemical vapor deposition of cyclopentadienyl dicarbonyl cobalt at 650 °C. The CoSi2 layer was conformally deposited on the Si emitter tips and had a twinned structure at the epitaxial CoSi2/Si interface in the partial region. The CoSi2-coated Si emitters showed an enhanced emission due to the increase in the number of emitting sites from the Fowler–Nordheim plot. The fluctuation of emission current was reduced by the CoSi2 coating. But the long-term stability was not much improved, which may be due to the decrease of the field enhancement factor and the number of emitting sites of the CoSi2-coated Si tip.
Microtwin formation mechanism in GaP/AlGaInP/GaAs double heterostructure light-emitting diodes
Authors: Zeng W. , Li Y. S. , Ji G. , Huang N. Y. , Wang J. J. , Zong X. F.
Published: July 2002

Cross-section transmission electron microscopy and high resolution electron microscopy were done to investigate the microtwins in GaP/(AlxGa1−x)0.52In0.48P/GaAs double heterostructure light-emitting diodes. There is a difference between the microtwins extending from the GaP/ (AlxGa1−x)0.52In0.48P interface into the GaP layer, and the microtwins existing in the GaP layer. High resolution electron microscopy measurements show that the length of microtwins extending from the GaP/AlGaInP interface along 〈112〉 directions is proportional to their thickness, while the microtwins in the GaP layer do not agree with that relationship. Also, it is not apparent that those microtwins extending from the interface contain more than seven atom layers. A formation mechanism of those microtwins extending from the interface was proposed and calculations were performed. The theoretical results are in agreement with the experimental measurements.
Analytic expression of the average energy of the field electrons from the n-type semiconductors
Authors: Chung Moon S. , Yoon Byung-G. , Seo Hyun S. , Cutler Paul H. , Miskovsky Nicholas M.
Published: July 2002

We have derived an analytic expression of the average energy of field electrons emitted from n-type semiconductors, for the first time. The average energy is obtained in terms of the hypergeometric and the Lerch transcendental functions. The analytic expression exhibits the apparent dependence of the average energy on the applied field, carrier concentration, and temperature. It also gives numerical values of the average energy in excellent agreement with those calculated using the full band structure calculation.
Simulation of planar deflection systems for field emission devices
Authors: Cui Zheng
Published: July 2002

Planar electron optical systems, with emphasis on planar deflectors, were investigated by computer simulation in three dimensions (3D). The simulations were carried out using a computer program based on the surface charge density method, with a coordinate system to assist meshing of boundary elements. Simulation of electron trajectories in 3D offers the possibility to see the final spot on an anode plane, helping to optimize the electron optical design. Three types of planar deflectors, split ring, microstrip, and horizontal bars were investigated to demonstrate their capability of deflecting electrons from a field emitter or a field emitter array. Some applications for these planar deflection systems have been suggested. Simple to fabricate and easy to be integrated with a field emitter are the biggest advantages for these planar electron optical systems. With the assistance of computer simulation, a better performance from these planar systems can also be achieved.
Comparison of phosgene formation from adsorption of carbon tetrachloride on oxygen modified Ir(111) and oxygen modified Ir(110)
Authors: Meyer R. J. , Reeves C. T. , Safarik D. J. , Allen D. T. , Mullins C. B.
Published: July 2002

The production of phosgene was observed when a pure carbon tetrachloride molecular beam was impinged on the oxygen modified Ir (111) and Ir(110) surfaces. Although the mechanism of phosgene formation is believed to be identical on the two surfaces, important differences in reactivity were observed. The phosgene production of oxygen modified Ir(111) was greater than the oxygen modified Ir(110) surface. Oxygen atoms are more tightly bound to the Ir(110) surface making it less reactive for the production of phosgene. Formation of the surface oxide on Ir(110) (which begins to occur if the surface is heated above 550 K) reduces adsorption of carbon tetrachloride, which necessarily decreases phosgene formation. The Ir(110) surface may also cause a more rapid decomposition of the adsorbed CCl2 intermediate. Phosgene production on oxygen modified Ir(110) also demonstrated a maximum at 500 K, whereas phosgene production on oxygen modified Ir(111) decreased with increasing temperature.
Real-time feedback control of electron density in inductively coupled plasmas
Authors: Chang Cheng-Hung , Leou Keh-Chyang , Lin Chaung
Published: July 2002

The real-time feedback control of electron density was performed in an inductively coupled plasma (ICP). A 36 GHz heterodyne interferometer was adopted as the sensor for electron density measurement. The actuator was rf power which drove the ICP antenna. The results show that the electron density in an ICP system is a type 0 system. Therefore, a proportional-integral controller is necessary to eliminate steady-state error. A prefilter was designed to smooth the desired step change of electron density so that the variation of rf power became mild. A feedforward compensator was added to reduce the disturbance effect resulting from pressure change. The experimental results showed that the control system could quickly track the desired electron density and compensate the electron density variation resulting from pressure disturbance.
Epitaxial VN(001) Grown and Analyzed In situ by XPS and UPS. II. Analysis of Ar+ Sputter Etched Layers
Authors: Haasch R. T. , Lee T. -Y. , Gall D. , Greene J. E. , Petrov I.
Published: July 2002

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to study epitaxial VN(001) layers grown in situ which were Ar+ sputter etched. The films were deposited on MgO(001) at 650 °C in pure N2 discharges maintained at a pressure of 5 mTorr (0.67 Pa) and shown to have a N/V ratio of 1.06 ± 0.02 by Rutherford backscattering (RBS). The films were sputter etched with 3 keV Ar+ at an angle of 40° to a constant nitrogen-to-vanadium ratio. A Mg Kα x-ray source was used to obtain the XPS data, while the UPS data was generated by He I and He II UV radiation. The sputter etched films were found to have a N/V ratio of 0.46, indicating a preferential removal of nitrogen.
Structural and electrical characteristics of chemical vapor deposited W/n-Si0.83Ge0.17/Si(001) and chemical vapor deposited WSix/n-Si0.83Ge0.17/Si(001)
Authors: Jang Y. C. , Shin D. O. , Kim K. S. , Shim K.-H. , Lee N.-E. , Youn S. P. , Roh K. J. , Roh Y. H.
Published: July 2002

Structural and electrical properties of chemical vapor deposited (CVD) W/n-Si0.83Ge0.17/Si(001) and CVD–WSix/n-Si0.83Ge0.17/Si(001) were studied by structural, chemical, and electrical characterizations. W and WSix layers were deposited on n-Si0.83Ge0.17/Si(001) and n-Si(001) at the growth temperature Ts=350–550 °C by low-pressure chemical vapor deposition utilizing WF6 and SiH4 source gases. Structural and chemical properties of CVD–W/n-Si0.83Ge0.17(001) and CVD–WSix/n-Si0.83Ge0.17(001) interfaces were analyzed by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, Rutherford backscattering spectroscopy, and Auger electron spectroscopy. Interfaces of CVD–WSix/n-Si0.83Ge0.17(001) were much sharper than those of CVD–W/n-Si0.83Ge0.17(001). Interfaces of CVD–W/n-Si0.83Ge0.17(001) are very rough presumably due to encroachment of SiGe layers caused by etching reaction of SiGe layers by WF6. Electrical properties of the CVD–W/n-Si0.83Ge0.17(001) and CVD–WSix/n-Si0.83Ge0.17(001) Schottky diodes were characterized by the current–voltage measurements. The measured effective Schottky barrier heights (φBn) of the CVD–W/n-Si0.83Ge0.17(001) Schottky contacts were 0.56±0.01 eV as the deposition temperature, Ts, of W layers increases from 350 to 550 °C, and CVD–WSix/n-Si0.83Ge0.17(001) Schottky contacts with CVD–WSix layers grown at Ts=350 °C showed the φBn values similar to those of CVD–W/n-Si0.83Ge0.17(001).
Plasma etch profiles of passivated open-area trenches
Authors: Abraham-Shrauner Barbara
Published: July 2002

The evolution of an etch profile of an open-area half trench is modeled. The etching of silicon dioxide is by a hydrofluorocarbon plasma, CHF3/CF4/Ar, in a magnetically enhanced reactive ion etching reactor. Two noticeable characteristics of the scanning electron microscope micrographs, the constant slope sidewall and microtrenching, are included in the model. The constant slope sidewall is due to sidewall passivation and the equation for the sidewall arises from a nonlinear evolution equation. Microtrenching can arise from the bombarding anisotropic ions that reach the bottom corner of the half trench to a greater degree than the deposition neutrals but may be enhanced by reflection of ions from the half trench and photoresist sidewalls. The etch rate expression due to the reflected ions is derived as an approximate analytical expression for small grazing angles and an energy threshold. The reflected ions do not contribute significantly to microtrenching for our etch profiles.
Investigation of the morphology of the initial growth of the aromatic molecule p-quaterphenyl on NaCl (001)
Authors: Kintzel E. J. , Smilgies D.-M. , Skofronick J. G. , Safron S. A. , Van Winkle D. H. , Trelenberg T. W. , Akhadov E. A. , Flaherty F. A.
Published: July 2002

Investigations of the structural properties of the initial layers of p-quaterphenyl (p-4P) vapor deposited onto NaCl (001) have been carried out using atomic force microscopy (AFM), grazing incidence x-ray diffraction (GIXRD), and helium atom scattering (HAS). A series of AFM images reveal accumulations of p-4P molecules around surface defects. Film thicknesses determined from height analyses of these images are in reasonable agreement with those found using GIXRD. The GIXRD studies indicate that p-4P films vapor-deposited at ambient temperature are composed of crystallites oriented with the long molecular axis nearly perpendicular to the NaCl (001) surface. For a nominally three-monolayer film, the b axis of the crystallites appears preferentially oriented along the substrate’s [110] azimuth, but with increasing thickness the x-ray features resemble those from two-dimensional (2D) powders. The diffraction peaks found in the HAS investigation at ∼50 K for a thick film grown at ∼200 K are similarly consistent with a 2D powder. The principal difference from the room temperature GIXRD experiments on thick films is that the a and b lattice parameters of the monoclinic unit cell appear doubled in length at ∼50 K.
Field emission from heat-treated cobalt-containing amorphous carbon composite films on glass substrate
Authors: Li Y. J. , Lau S. P. , Tay B. K. , Sun Z. , Chen G. Y. , Chen J. S. , Ding X. Z.
Published: July 2002

Cobalt-containing amorphous carbon composite films have been prepared by filtered cathodic vacuum arc technique (FCVA) with a cobalt-containing graphite target on nickel-coated Corning glass at room temperature. After heat treating at 550 °C in a mixture of acetylene and nitrogen gases, field emission properties of the a-C:Co films were significantly improved. Relatively uniform emission sites and a low threshold electric field of 2 V/μm were obtained without conditioning. The relatively low threshold field is probably attributed to both the graphitization of the composite films caused by cobalt catalyst and modified surface conditions by the heat-treatment process. Moreover, the heat-treated samples still remained a smooth surface with a root mean square roughness of about 22 nm, which could be possibly used to prepare gated carbon emitter array for field emission display.
Effects of color phosphors on the lifetime of field emission carbon thin films
Authors: Thuesen L. H.
Published: July 2002

Tests were performed on Field Emission Picture Element Technology, Inc. carbon thin film cathodes to characterize the effects of phosphors on the emission lifetime. The cathodes were tested in sealed, glass tubes in a diode configuration. The phosphors in the tubes were ZnS:AgAl (blue), ZnS:CuAl (green), and YVO4:Eu (red). After lifetesting, before and after comparisons of the cathode current versus voltage characteristics were made. Due to the large variance in the data, the results did not clearly separate all of the different phosphors’ effects on lifetime. However, there was some indication that the tubes with blue phosphor had a longer lifetime than the green. The tests with the red phosphor produced mixed results with some of the devices having a lifetime similar to the blue but others having a much longer lifetime. The results with the red phosphor point to the role of phosphor screen preparation in extending the life of the cathode.
Growth and characterization of MnAs/ZnSe ferromagnet/semiconductor hybrid heterostructures
Authors: Chun S. H. , Berry J. J. , Ku K. C. , Samarth N. , Malajovich I. , Awschalom D. D.
Published: July 2002

We report a detailed study of the molecular beam epitaxy of MnAs/ZnSe heterostructures on GaAs (100) substrates under varying growth conditions. As with the MnAs/GaAs system, these MnAs/ZnSe epilayers show ferromagnetism at room temperature, although with different structural and magnetic characteristics. We study the impact of parameters such as the As/Mn beam equivalent pressure ratio, substrate temperature, templating, and substrate misorientation on the MnAs/ZnSe heterostructures utilizing in situ reflectance high energy electron diffraction, as well as ex situ x-ray diffraction and atomic force microscopy. This structural information is correlated with magnetic properties obtained from magneto-optical Kerr effect and superconducting quantum interference device magnetometry. Finally, we discuss preliminary studies on the properties of MnAs/ZnSe/MnAs trilayers for spin-valve type applications.
Epitaxial growth of cubic SiC thin films on silicon using single molecular precursors by metalorganic chemical vapor deposition
Authors: Boo J.-H. , Lee S.-B. , Lee K.-W. , Yu K.-S. , Kim Y. , Yeon S. H. , Jung I. N.
Published: July 2002

Heteroepitaxial cubic SiC thin films have been deposited on silicon substrates at temperatures in the range of 750–1000 °C using single molecular precursors by the metalorganic chemical vapor deposition (CVD) method. Single-crystalline, crack-free, stoichiometric cubic SiC films were successfully grown on both Si(001) and Si(111) substrates without surface carbonization at as low as temperature of 920 °C with 1,3-disilabutane, H3Si–CH2–SiH2–CH3, as a liquid single source precursor which contains silicon and carbon in 1:1 ratio. Cubic SiC thin films highly oriented in the [001] direction were also obtained on Si(001) using either a liquid mixture of 1,3,5-trisilapentane (TSP), H3Si–CH2–SiH2–CH2–SiH3, and 2,4,6-trisilaheptane (TSH) at 980 °C or 2,6-dimethyl-2,4,6-trisilaheptane (DMTSH), H3C–SiH(CH3)–CH2–SiH2–CH2–SiH(CH3)–CH3 at 950 °C without carrier gas. These growth temperatures were much lower than conventional CVD growth temperatures, and this is a report of cubic SiC film growth using the single molecular precursors of trisilaalkanes (i.e., DMTSH and TSP+TSH). The as-grown SiC films were characterized by in situ reflection high-energy electron diffraction and by ex situ x-ray diffraction, transmission electron diffraction, scanning electron microscopy, Auger electron spectroscopy, and Rutherford backscattering spectroscopy
Characterization of thin photosensitive polyimide films for future metallization schemes
Authors: Alford T. L. , Zou Y. L. , Gadre Kaustubh S. , Theodore N. David , Chen W.
Published: July 2002

Photosensitive polyimide (PSPI) is being integrated as potential low dielectric constant layers in next generation advanced silver metallization. These dielectrics have excellent thermal stability as represented by a thermal decomposition temperature of 450 °C and an average thermal expansion coefficient of 20×10−6/°C. This results in a low stress (<26 MPa) in the polyimide film as measured during in situ curing and cooling cycles. The morphology and structure of two types of polyimides, 3,3′,4,4′-biphenyl tetracarboxylic acid dianhydride-p-phenylenediamine (BPDA/PPD) and the PSPI based on BPDA/PPD, have been investigated in this work. Both refractive indices measurements and x-ray scans indicated that the 85 °C dried BPDA/PPD is slightly anisotropic, but the dried PSPI films are isotropic. Both polyimide films cured at 300 °C exhibit optical anisotropy with the average in-plane refractive index of 1.74 and the out-of-plane index of 1.62, indicating a strong preference of polymer chains to orient along the film plane. The dielectric constants were 3.0 and 2.6 in the in-plane and out-of-plane directions, respectively. The reduced number of process steps associated with PSPI and Ag etch over conventional Cu chemical mechanical polishing, shows great potential in terms of future process integration.
Pt–metal oxide aerogel catalysts: X-ray photoemission investigation
Authors: Nelson A. J. , Reynolds John G. , Sanner R. D. , Coronado P. R. , Hair L. M.
Published: July 2002

X-ray photoemission spectroscopy was used to study Pt–metal oxide aerogel catalysts that have been developed to respond to increased NOx emissions of lean-burn engines. Lean-burn engines, critical components of low and zero emission vehicles, produce much higher levels of engine-out NOx and current three-way catalytic converters are not sufficient to meet Clean Air Act standards. Platinum catalysts were formed by the reaction of modified Pt coordination compounds with selected transition–metal alkoxides through sol–gel techniques into aerogels. Photoemission measurements of the Pt 4f, Si 2p, Ti 2p, O 1s, and C 1s core lines were used to evaluate the chemistry of the material after each processing step. Results indicate Pt–O bonding and reduced Pt disbursed in the aerogel. In addition, Si 2p, Ti 2p, and O 1s binding energies indicate an oxo-bridged network structure.
Gas-source molecular beam expitaxy of GaInNP/GaAs and a study of its band lineup
Authors: Hong Y. G. , André R. , Tu C. W.
Published: July 2002

We report gas-source molecular beam epitaxy of high-quality Ga1−xInxNyP1−y/GaAs heterostructures grown on a GaAs (100) substrate. Bulk Ga1−xInxNyP1−y, as well as Ga1−xInxNyP1−y/GaAs, quantum well (QW) samples were grown and characterized by a high-resolution x-ray rocking curve and photoluminescence (PL). With nitrogen incorporation, the PL peak redshifts, indicating band gap reduction. Rapid thermal annealing for 10 s in a 100% N2 ambient with 700 °C temperature improves the Ga0.46In0.54N0.005P0.995PL intensity by a factor of 10 and reduces the linewidth to two fifths. We use both bulk and QW PL experimental data to determine band lineup for Ga1−xInxNyP1−y/GaAs heterostructure. Most of the band reduction is attributed from the conduction band with nitrogen incorporation.
Molecular beam epitaxy growth and characterization of ZnTe:Cr2+ layers on GaAs(100)
Authors: Sadofyev Yu. G. , Pevtsov V. F. , Dianov E. M. , Trubenko P. A. , Korshkov M. V.
Published: July 2002

The chromium-doped ZnTe layers were grown by molecular beam epitaxy technology on the GaAs substrates. The metallic chromium was used as a dopant. The characteristic emission of the Cr2+ ions that is incorporated into ZnTe epilayers was obtained. However, the attempt of doping by CrI3 has shown that the halides induce a deterioration of the surface morphology and are inefficient dopants for II–VI semiconductors.
Growth of giant magnetoresistance multilayers: Effects of processing conditions during radio-frequency diode deposition
Authors: Zou W. , Wadley H. N. G. , Zhou X. W. , Ghosal S. , Kosut R. , Brownell D.
Published: July 2002

The magnetotransport properties of giant magnetoresistance multilayers are significantly effected by the atomic-scale structure of the interfaces between the nonferromagnetic conducting and ferromagnetic (FM) metal layers. The interfacial roughness and the extent of intermixing at these interfaces are both known to be important. A combination of experimental and multiscale modeling studies have been used to investigate control of interface structure during multilayer growth by rf diode deposition and the consequences of such control for magnetotransport. Experiments were conducted to evaluate the dependence of the magnetotransport properties of NiFeCo/CoFe/CuAgAu multilayers upon the growth conditions (background pressure, input power), and to link the roughness of vapor-deposited copper layers to the same process parameters. These experimental studies reveal the existence of intermediate background pressure (20 mTorr) and plasma power (175 W) that resulted in the highest magnetoresistance and a strong sensitivity of copper layer surface roughness to both the power and pressure at which deposition was conducted. By using a combination of modeling technologies, the deposition process conditions have been linked to the atomic fluxes incident upon the sample surface. This was then used to determine the atomic-scale roughness of the film. Energetic metal atoms (and inert gas ions) were found to have very strong effects upon interfacial structure. The models revealed an increase in interfacial roughness when metal (or inert gas ion) translational energy was decreased by either reducing the plasma power and/or increasing the background pressure. Because high-energy metal impacts activated atomic jumping near the impact sites, high plasma power, low background pressure process conditions resulted in the smoothest interface films. However, these conditions were also conducive to more energetic Ar+ ion bombardment, which was shown by molecular dynamics modeling to induce mixing of the FM on the copper interface. Intermediate plasma powers/background pressures result in the most perfect interfaces and best magnetotransport. The insights gained by the modeling approach indicate a need to avoid any energetic ion bombardment during the early growth stages of each new layer. This could be accomplished by operating at low power and/or high pressure for the first few monolayers of each layer growth and may provide a growth strategy for further improvement in magnetotransport performance.
Optical-constant tunable (ZrO2)x/(Cr2O3)y/(Al2O3)1−x−y optical superlattices for attenuated phase shift mask in ArF lithography
Authors: Lai F. D. , Wang L. A.
Published: July 2002

( ZrO 2 ) x /( Cr 2 O 3 ) y /( Al 2 O 3 ) 1−x−y optical superlattices composed of ten film stacks with ∼9 nm thickness in each stack, which includes the stoichiometric ZrO2, Cr2O3, and Al2O3 layers, are obtained by using rf unbalanced magnetron sputtering in an atmosphere of argon and oxygen. Binding energies of Cr 2p3/2, Al 2p3/2, and Zr 3d5/2 identified by x-ray photoelectron spectroscopy (XPS) are consistent with those of the theoretical Al2O3, Cr2O3, and ZrO2 XPS spectrum, respectively. The dielectric constants of (ZrO2)0.4/(Cr2O3)y/(Al2O3)0.6−y and (ZrO2)x/(Cr2O3)0.6/(Al2O3)0.4−x optical superlattices are illustrated to satisfy the effective medium approximation. By controlling the thickness percentage of ZrO2, Cr2O3, and Al2O3, the optical constant tunable (ZrO2)x/(Cr2O3)y/(Al2O3)1−x−y optical superlattices can meet the optical requirements of a material blank for an attenuated phase shift mask (APSM). A quadrangular area of thickness percentage of (ZrO2, Cr2O3) that meets the requirement of optical constants for an APSM blank is found to be bounded by (0, 0.25), (0, 0.45), (0.35, 0.65), and (0.45, 0.40).
Compact synchrotron radiation lithography system for 70 nm device manufacturing
Authors: Miyatake Tsutomu , Li Xuan , Hirose Sayumi , Monzen Toshio , Fujii Kiyoshi , Suzuki Katsumi
Published: July 2002

We report on the performance and reliability of our synchrotron radiation (SR) based x-ray lithography (XRL) system installed in Tanashi Works of Sumitomo Heavy Industries, Ltd. Our XRL facilities include a compact racetrack-type SR light source “AURORA-2S” (A2S), the injector microtron, a 3-m-long beamline, and the second version x-ray aligner. In 2000, A2S proved the beam lifetime of 16 h in regular operation at the designed beam current 500 mA. The XRL beamline offers a high-dose exposure rate of over 43 mW/cm2 on a wafer at beam current 500 mA. The x-ray aligner achieved an overlay accuracy better than 16 nm (3σ) using a video-based scattered-light alignment (SLA) system. In the SLA, edge scattering on matrix array patterns provides multispot video images for mask to wafer alignment. A 70 nm line and space (L/S) pattern was replicated with a gap of 15 μm. In resolution enhancement exposure, we replicated a 100 nm L/S and 1 100 nm hole pattern using a 200 nm L/S and a 200 nm hole pattern of x-ray mask, respectively.
Investigation of molecular beam epitaxial NdF3/Si(111) heterostructures by atomic force microscopy and x-ray diffractometry
Authors: Ko J. M. , Durbin S. D. , Fukuda T. , Inaba K.
Published: July 2002

NdF 3 layers were grown on Si(111) substrates at 400, 550, and 700 °C by molecular beam epitaxy. The surface morphology observations by atomic force microscopy indicated that the NdF3 layers on Si(111) substrates grew as islands associated with screw dislocations, which coalesced less densely at higher growth temperatures. The layers grown at higher temperatures were more susceptible to formation of microcracks due to larger mismatch of the thermal expansion coefficient. The orientational relationship between NdF3 layers and Si(111) substrates was confirmed to be NdF3(0002)〈11−20〉‖Si(111)〈1−10〉 by x-ray diffraction measurement. As a function of growth temperature and layer thickness, the crystallinity of resulting layers in terms of full width at half maximum values was investigated. In particular, for NdF3 layers grown at a high temperature of 700 °C, lattice relaxation and crystallinity degradation with layer thickening were found.
Materials aspects, electrical performance, and scalability of Ni silicide towards sub-0.13 μm technologies
Authors: Lauwers Anne , Steegen An , de Potter Muriel , Lindsay Richard , Satta Alessandra , Bender Hugo , Maex K.
Published: July 2002

Ni-silicide phase formation with and without a Ti capping layer was studied by sheet resistance, x-ray diffraction and transmission electron microscopy. Ni monosilicide is found to be the stable phase in a temperature range from 400 to 600 °C. At lower temperatures the Ni2Si phase is found to be present. For temperatures higher than 700 °C NiSi is converted into NiSi2. Pyramidal NiSi2 precipitates were found to grow epitaxially along the Si〈111〉 planes for annealing temperatures as low as 310 °C. The epitaxial NiSi2 grains were found to disappear when the annealing temperature is increased. Stress buildup during Ni silicidation was measured in situ and could be correlated to the formation of the different Ni-silicide phases. The stress induced by Ni-monosilicide formation compares favorably to the stress induced by Co disilicide and Ti disilicide. The average silicon consumption required to obtain a certain sheet resistance was found to be 35% lower for Ni monosilicide compared for Co disilicide. It was found that a two-step process is needed to obtain complete conversion to the preferred Ni-monosilicide phase without lateral silicide growth. The sheet resistance of Ni-silicided narrow poly-Si and active area lines was found to be low, even when Ni silicide was formed without a Ti cap. No degradation of the Ni silicide on the narrow poly-Si lines was observed when the silicidation temperature was increased to 600 °C. The reverse bias leakage of shallow Ni-silicided and Co-silicided square diodes was compared for varying junction depths and varying silicide thicknesses. For similar junction depth and similar sheet resistance, a lower reverse bias leakage current was obtained for a Ni-silicided junction compared to its Co-silicided counterpart. This may be attributed to the reduced Si consumption of Ni monosilicide compared to Co disilicide.
Comparative study of resolution limiting factors in electron beam lithography using the edge roughness evaluation method
Authors: Yoshizawa Masaki , Moriya Shigeru
Published: July 2002

Resolution capabilities of a Nikon 100 kV experimental column of electron beam (EB) projection lithography, a proof of concept column of low energy electron beam proximity projection lithography (LEEPL), and a variable-shaped EB direct writer were compared using a negative-type chemically amplified resist. Line edge roughness and resolution limit of an isolated line were 2.8 and 40 nm for the Nikon experimental column, and were 4.9 and 52 nm for the EB direct writer at the resist thickness of 250 nm, while they were 10.7 and 61 nm for LEEPL, and were 9.6 and 57 nm for the EB direct writer at the resist thickness of 70 nm. Quantitative influences of resolution limiting factors such as electron-optical beam blur and resist performance were analyzed using the edge roughness evaluation method. The analysis shows that the Nikon experimental column has an ability to resolve 35 nm patterns if resolution performance of the resist is 10% improved. In the high-throughput EB stepper system with a large beam current, it is necessary for resolving 50 nm patterns to keep the electron-optical beam blur under 36 nm. It is known about LEEPL that a necessary and sufficient condition for realizing 50 nm patterns is to develop a 50 nm thick resist having the same resolution performance as the conventional resist dedicated for the use with thicker film thickness, and to obtain a 50 nm pattern mask having the same aperture roughness as the conventional mask with 70 nm patterns.
Steady-state direct-current plasma immersion ion implantation using a multipolar magnetic field electron cyclotron resonance plasma source
Authors: Zeng Xuchu , Tong Honghui , Fu Ricky King-Yu , Chu Paul K. , Xu Zejin , Chen Qingchuan
Published: July 2002

In semiconductor plasma immersion ion implantation (PIII) applications such as the synthesis of silicon-on-insulator by hydrogen PIII and ion cut, only ions arriving at the top surface of the sample stage are important. The ions implanted into the other surfaces of the sample chuck actually not only decrease the efficiency of the power supply and plasma source but also give rise to metallic contamination. In addition, low energy ions introduced by the initial plasma sheath propagation, pulse rise time, and pulse fall time introduce a large surface hydrogen concentration that creates surface damage and affects the wafer bonding efficacy. We have theoretically demonstrated direct-current PIII (DC-PIII) which retains the x–y immersion characteristic while simultaneously reducing this low energy ion component, obviating the need for the expensive power modulator, and extending the voltage ceiling that is no longer limited by the vacuum chamber and power modulator. In this article, we describe our hydrogen DC-PIII experiments using a conducting grid placed between the wafer stage and a multipolar electron cyclotron resonance plasma source. The grounded grid stops the propagation of the plasma sheath, thereby removing the vacuum chamber size limitation. Ions are formed in the plasma sustained by an external plasma source above the grid and accelerated through the lower zone to be implanted into the wafer biased by only a dc power supply. Atomic force microscopy, hydrogen forward scattering, and secondary ion mass spectrometry analyses indicate uniform hydrogen PIII into a 100 mm silicon wafer and the surface hydrogen component is indeed reduced significantly compared to conventional pulsed PIII.
Improvement of the SiO2/Si interface characteristics by two-step deposition with intermediate plasma treatment using O2/He gas
Authors: Yi Chung , Kim Hyo Uk , Rhee Shi Woo , Oh Sang Ho , Park Chan-Gyung
Published: July 2002

We studied two-step deposition with an O2/He intermediate plasma treatment to improve the SiO2/Si interface characteristics. Using this method, we can minimize the plasma damage on the Si surface and improve the interface characteristics such as intermediate oxidation states, interface trap density Dit, and Vfb shift. The interface characteristics were improved with the intermediate plasma treatment after a 6 nm first oxide deposition. The number of Si atoms (NSiOx) in the suboxide region, compared with the sample without plasma treatment, was decreased 14.7% and a sixfold ring structure became dominant. Interface trap density was decreased from 1.65×1011/eV cm2 to 6.87×1010/eV cm2 by the oxygen incorporation in the transition region. The moderate oxygen incorporation near the SiO2/Si interface reduced the Vfb shift due to the decrease of the fixed oxide charge.
Experimental study of electron beam projection lithography mask defect printability
Authors: Kojima Yoshinori , Katakura Norihiro , Tomo Yoichi , Takenaka Hiroshi , Yoshida Akira , Shimizu Isao , Yamabe Masaki
Published: July 2002

Mask defect printability of electron beam projection lithography (EPL) was investigated. We fabricated EPL chip reticles including programmed defects. The design of these programmed defects was based on semiconductor equipment and materials international (SEMI) standards, but we modified it from the original to a new design for the 100–70 nm node. In our defect printability experiment, Nikon’s electron beam (EB) projection experimental column was used as an exposure tool with those chip reticles. The acceleration voltage of the electron beam was 100 kV. In the case of the “size shift” defects, the correlation between the defect size on the reticle (×1/4) and the critical dimension (CD) change on the wafer is linear and the defect down to 40 nm was printed. Furthermore mask error enhancement factor is nearly equal to 1. This is the advantage of the EPL over the optical lithography. On the other hand, in the case of “dot” defects, defects smaller than 100 nm on the reticle has a small impact on the CD change. The allowable defect size with a criterion of a given ΔCD became larger at the defocus condition.