bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Experimental and Theoretical LEED Spectra for Al
Authors: Baudoing R. , deBersuder L. , Gaubert C. , Hoffstein V. , Lauzier J. , Taub H.
Published: July 2002

We present a comparison between the experimental and theoretical LEED rotation diagrams obtained from the (001) surface of Al. The experiment was performed at E=20 eV over a large range of polar angles with the help of a new LEED goniometer which permits us to vary the polar angle between 0° and 90° and the azimuthal angle between 0° and 360° without opening the system. Realizing that rotation diagrams (which exhibit most directly dynamical effects) constitute perhaps the most crucial test of any dynamical theory of LEED, we have performed calculations using the following formalisms: multiple scattering theory of McRae–Kambe, band structure-matching, one-dimensional multiple scattering model, and inelastic collision model. The results of these calculations (performed for the same incidence conditions) are compared and their relationship with experiment is discussed.
Surface Potentials of Xenon Adsorbed on Nickel
Authors: Baker B. G. , Johnson B. B.
Published: July 2002

Photoelectric emission from well-annealed evaporated nickel films can be resolved by computation to determine the work functions of the crystal planes exposed at the surface. This technique has been applied to interpret surface potential measurements for xenon adsorbed on nickel films. The surface potential was found to increase with coverage, the upper limiting values being 0.16 eV for the (111) plane and 0.30 eV for the (100) plane. Much higher values, up to 0.95 eV, were found for rough surfaces of low initial work function. The variation of surface potential with coverage on the (100) plane was found to be stepwise suggesting the existence of at least two submonolayer ordered surface lattices for adsorbed xenon.
Linearity of a Heavily Loaded Quartz Crystal Microbalance
Authors: Denison D. R.
Published: July 2002

A study of the linearity of a digital microbalance was made to determine microbalance performance with high crystal loading. The 5-MHz crystals were loaded by 30Å/sec deposition of Al in 40 kÅ steps and Cu in 8 kÅ steps. The film thickness, measured on an adjacent quartz, optical flat, was compared with the indicated film thickness of the microbalance (computed from crystal period shift). The data presented, which show linearity within ±0.3%, agrees with a theory that postulates no elastic loss within the deposited film. However, a transient phenomenon is observed with both Al and Cu that could result in microbalance errors of greater than 5%. Deposits of up to 25 mg/cm2 (950 kÅ of Al) were studied to evaluate the magnitude of this potential error.
Theory of Critical Behavior in Films
Authors: Bergman D. J. , Imry Y. , Deutscher G. , Alexander S.
Published: July 2002

The critical behavior of a thin film which is an intermediate case between a two-dimensional and three-dimensional system is considered and its various modes of critical behavior analyzed. This is used to find scaling-type relations among the two-dimensional and three-dimensional critical indices. We show that a great deal of information on the critical behavior can be obtained from measurements of the thickness dependence of the amplitudes of the various critically diverging quantities.
Electronic Structure of Ultrathin Transition and Noble Metal Films with Simple Metal Interfaces
Authors: Cooper Bernard R.
Published: July 2002

We have developed a technique within the framework of the Green's function method for calculating the changes in electronic structure of d-band metals associated with going from a bulk to an ultrathin (oligatomic) film geometry. The formal result making high quality calculations of this type practical is that the film problem with a vanishing wavefunction boundary condition has electronic eigenfunctions which, within the film boundaries, are identical to those of an appropriately defined three-dimensional periodic tetragonal complex lattice. The boundary where the wave functions are constrained to vanish can lie outside the physical boundary limiting the region where the potential corresponds to the d-band metal, and can vary with energy. This has enabled us to allow for electron leakage from the d-band metal film and accurately simulate either the situation of a d-band metal film suspended in vacuum, or the more experimentally realizable situation of an ultrathin film of a d-band metal with interfaces with a simple metal. We show results for the latter situation for a monlayer of copper. These calculations predict striking changes from bulk behavior in agreement with photoemission experiments.
Field Effects in Extremely Thin Crystals of Bi8Te7S5
Authors: Grote U. H. , Soonpaa H. H.
Published: July 2002

Field effect conductivity measurements have been performed on extremely thin crystals of Bi8Te7S5. Only the thinnest (5 atoms thick) crystals show an unusual behavior, which can be readily explained in terms of the Fermi sphere, which does not intersect quantized Fermi momentum levels at zero bias. It is shown that both the volume density of carriers and the spacing of quantized kF levels increase at the same rate with decreasing sample thickness; thus the limitation in the observability of quantized kF levels is in the areal carrier density σ that the dielectric material between the film and the gate will allow.
Liquid Crystal Displays
Authors: Goodman L. A.
Published: July 2002

The various steps in the application of liquid crystals to displays are reviewed. First, the general classifications of liquid crystals and some common compounds are presented. Then, electrode materials and techniques for cell construction are discussed. Next, the diverse surface orientation methods are discussed. The electro-optic effects are classified by origin, that is, whether they result solely from dielectric forces or from the combination of dielectric and conduction stimuli. Different techniques for addressing liquid crystal displays are given. Finally, present and future applications are mentioned.
Sputtered Platinum as Substrate for Ferroelectric Film Deposition
Authors: Vogel S. F. , Barlow I. C.
Published: July 2002

Strongly adherent platinum films, 0.5 μ thick, were obtained on single-crystal alumina (sapphire) and polycrystalline alumina chips by sputtering platinum first in oxygen, then in argon, and subsequently heating the films at 930 °C in air. The crystal structure and orientation, as well as the related topography of the films, were characterized by x-ray diffraction and scanning electron microscopy, respectively.
Relativistic Electron-Beam Pumped uv Gas Lasers
Authors: Dreyfus R. W. , Hodgson R. T.
Published: July 2002

Stimulated emission occurs when (ortho- and para-) H2, HD, D2, CO, Ne, and N2 are excited by a 4-GW electron beam. The beam is generated by a Febetron, model 706, and propagates 2.3 m through the gases at 8–100-Torr pressures. Propagation is aided by an externally applied ∼ 10 kG magnetic field. Collisions involving primary, secondary, and cascade electrons transfer ≤ 0.1% of the energy from the electron beam to produce population inversions. The small-collision cross sections for relativistic electrons act as the primary limitation to the transfer of more energy to the gas molecules. Dependence of the laser energy on isotopes and temperature indicates that the spectral linewidth is due to Doppler broadening, and consequently higher power and optical gain are available by cooling the gases to ∼ 90 K or lower. The additional optical gain allows lasing to be observed at shorter wavelengths (1098 Å as compared to 1161 Å) and at higher powers near 1200 Å (∼ 5 kW/ cm2 as compared to 0.5 kW/cm2) than reported previously.
Inelastic electron tunneling spectroscopy of phenol and hydroquinone chemisorbed on alumina
Authors: Lewis B. F. , Bowser W. M. , Horn J. L. , Luu T. , Weinberg W. H.
Published: July 2002

Inelastic electron tunneling spectroscopy has been used to probe the irreversible chemisorption of C6H5OH and 1,4-C6H4(OH)2 on a thin amorphous film of Al2O3. This spectroscopy yields a representation of the vibronic excitations of the chemical bonds in the adspecies, i.e., the tunneling spectra are analogous to ir spectra. The C6H5OH is found to adsorb predominately as C6H5O− with a small amount of adsorption as C6H5OH. The 1,4-C6H4(OH)2 is found to adsorb predominately as C6H4(OH)O− and perhaps to a smaller extent as C6H4O22−. Extensive hydrogen bonding is observed among adsorbates and between adsorbates and the hydroxylated alumina surface.
Abstract: Production electron-beam-welding equipment
Authors: Samuelson Fred H.
Published: July 2002

Design considerations for production electron-beam equipment, such as power level, filament lifetime, improved beam characteristics, and stability of beam location are briefly reviewed. The main features and requirements of three types of electron-beam-welding systems (partial vacuum, nonvacuum, and high vacuum) developed by Hamilton Standard are described in detail. Of particular note is their telefocus electron gun which is claimed to provide focus control that is independent of beam current.
Vacuum sintering of stainless steel
Authors: Otto George
Published: July 2002

The vacuum-sintering operation at The Maytag Company is discussed in detail; work with several types of stainless steels is described. The focus is chiefly on type 304-L, since the bulk of Maytag’s experience has been with this material. A typical vacuum-sintering cycle is also described. Photomicrographs showing normal and abnormal microstructures of as-sintered 304 stainless, as well as the microstructure of 410 stainless with carbon additions are summarized.
The role of the metal-semiconductor interface in silicon integrated circuit technology
Authors: Andrews J. M.
Published: July 2002

A typical medium-scale integrated (MSI) circuit requires hundreds of metal-semiconductor (M–S) junctions that are utilized for rectification, interconnection of device elements, and termination to external circuits. Comparison has been made between two metallization technologies, based upon the possible metallurgical reactions with Si: (1) nonreactive, such as evaporated aluminum, and (2) reactive, such as PtSi. Ohmic and rectifying contacts have been contrasted on the basis of the dominant current conduction mechanisms at the M–S interface. Current transport has been characterized in terms of the height and thickness of the potential energy barrier arising from thermal equilibrium among charge carriers between dissimilar conductors. Thermionic emission of electrons and holes provides the first illustration of conduction over a thick potential barrier (≫100 Å), resulting in a rectifying contact (Schottky barrier diode). Thus, Schottky diode currents are exponentially dependent upon potential barrier height and inverse temperature. The contrasting illustration deals with a thin barrier (≪100 Å) that conducts electrons and holes by quantum mechanical tunneling and forms ohmic contacts with resistance controlled only by contact size and underlying silicon resistivity. The final section covers two possible problems associated with silicon integrated circuit (SIC) fabrication. In the first example, a layer of oxide, too thin to be visible by optical interference (<500 Å), can prevent proper contact formation. A method of observation, which makes use of hydrostatic surface tension, has been presented with experimental results on SiO2 films. Successive etching has revealed a detection limit of 11–13 Å. The second deleterious phenomenon to be treated is the electrical degradation of Schottky barrier rectification associated with nonplanar penetration of metals into silicon. The destruction of the planar M–S interface could result from either undesired alloy eutectics or metallic precipitation.
Phase development in annealed zirconia-titania nanolaminates
Authors: DeLoach J. D. , Shibilski J. J. , Crape C. R. , Aita C. R.
Published: July 2002

Phase development was studied in sputter-deposited and annealed ZrO2–TiO2 nanolaminate films on fused silica substrates. The goal was to understand phase evolution as these structures moved toward thermodynamic equilibrium. The results show that diffusive amorphization to form α-ZTO was the first reaction of the as-deposited constituents at low temperature (700 °C). Growth of α-ZTO was self-limited, and a second metastable reaction product with an incommensurate α-PbO2-type lattice, ss-ZTO, formed with time at temperature. Terminal phases formed only when the annealing temperature was raised to 1000 °C, thereby lifting kinetic constraints to diffusion. The terminal phases were ZrTiO4 or ZrTi2O6, depending upon film stoichiometry. This study demonstrates that in the absence of a physical driving force to promote layer registration upon low temperature annealing, constituents react to lower the system’s free energy via a series of metastable phases that involve limited atomic rearrangement. Equilibrium phases are formed only after the kinetic constraints to diffusion are relaxed.
Extreme ultraviolet alignment and testing of a four-mirror ring field extreme ultraviolet optical system
Authors: Goldberg Kenneth A. , Naulleau Patrick , Batson Phillip , Denham Paul , Anderson Erik H. , Chapman Henry , Bokor Jeffrey
Published: July 2002

Extreme ultraviolet (EUV) interferometry has been used to characterize and align a recently fabricated, 4× reduction, four-mirror, aspheric optical system designed for EUV lithography. This system is called the Engineering Test Stand Set-1 Optic. An EUV phase-shifting point diffraction interferometer constructed on an undulator beamline at the Advanced Light Source was used to perform high-accuracy wavefront measurements during several alignment iterations. For each iteration, the alignment algorithm used 35 wavefront measurements recorded across the 26-mm-wide image-side ring field. Adjustments were made to systematically reduce the root mean square wavefront error magnitude to approximately 1 nm, bringing the system to nearly diffraction-limited performance.
Demagnifying immersion magnetic lenses used for projection electron beam lithography without crossovers
Authors: Cheng Min , Tang Tiantong
Published: July 2002

Curvilinear-axis electron optical focusing and aberration theory of wide electron beams in immersion magnetic lenses, which can be used for projection electron beam lithography, are put forward, and second-order aberration formulas have been derived using the symbolic manipulation software MATHEMATICA®. A program was written to calculate numerically the wide beam Gaussian focusing and aberration properties of these lenses by using the curvilinear-axis theory. The magnetic structures that have convergent force lines have been studied. As an example, lenses with an analytical axial magnetic field distribution are calculated. The results show that wide beam projection images without crossovers can be formed with demagnified lateral magnification, and with a submicron and nanometer lateral resolution over a larger field size.
Zone-plate-array lithography using synchrotron radiation
Authors: Pépin A. , Decanini D. , Chen Y.
Published: July 2002

We present our results in the design and development of a multiple-beam x-ray pattern generator based on an array of Fresnel zone plates (FZPs). Exposures have been carried out using a synchrotron source at SuperACO (France), a PC-controlled piezoelectric scanning stage, and an array of FZPs fabricated by high resolution electron-beam lithography and reactive-ion etching of a tungsten absorber. In particular, we have implemented an array of apertures using a self-aligned process in order to minimize background intensity coming from diffraction orders other than the positive first order. We show that even with polychromatic synchrotron radiation and relatively low resolution FZPs, patterns of various geometries could be successfully written in poly(methylmethacrylate) resist and submicrometer resolution was obtained after metal liftoff.
Fabrication of 30 nm T gates using SiNx as a supporting and definition layer
Authors: Chen Y. , Edgar D. , Li X. , Macintyre D. , Thoms S.
Published: July 2002

A new process has been developed to fabricate 30 nm T gates for high performance metal–semiconductor field effect transistors and high electron mobility transistors. The fabrication of short gate length T gates becomes increasingly difficult as the footwidth of the gate is made smaller and this is particularly true when the footwidth is less than 50 nm. In this process a thin SiNx layer is deposited on the substrate prior to the application of a bilayer of poly(methylmethacrylate)/Shipley UVIII resist. After resist patterning by electron beam lithography the nitride layer is etched at a low bias voltage that causes negligible substrate damage. This process step helps to define the gate footwidth and improves mechanical stability of the gate. The measured gate resistance was 375 Ω/mm.
Lithographic patterning and confocal imaging with zone plates
Authors: Gil Darı́o , Menon Rajesh , Carter D. J. D. , Smith Henry I.
Published: July 2002

Zone-plate-array lithography (ZPAL) uses an array of zone plates, combined with an array of micromechanical mirrors or shutters, to pattern features on a substrate without a mask. In this article, we investigate the patterning characteristics of individual zone plates. We show patterns printed with pixel-dose modulation (gray scaling) and subpixel beam stepping. Using a combination of these techniques for linewidth control, edge placement, and proximity-effect correction, ZPAL can produce arbitrary patterns with features as small as the focal spot of a zone plate. We also demonstrate the use of zone plates in a confocal-microscopy mode for placing the substrate at the focus of the zone plates, and for imaging. Zone-plate-array scanning-confocal microscopy (ZPAM) could be useful for gapping and alignment in ZPAL, and possibly for wafer or mask inspection at deep ultraviolet wavelengths.
Doped CHx microshells prepared by radio frequency plasma enhanced chemical vapor deposition for inertial confinement fusion experiments
Authors: Theobald M. , Baclet P. , Legaie O. , Durand J.
Published: July 2002

French targets prepared for inertial confinement fusion experiments, to be shot on the Laser Mégajoule facility, are organic (CHx) microshells. The microshell, that contains the deuterium–tritium mixture (DT), is placed in a gold holraum that converts the laser light into an x-ray flow. It is an indirect drive to reach ignition. This microshell, whose role is an ablator to initiate compression of the target, is fabricated by plasma polymerization of organic precursors. In these implosion experiments, it is necessary to control the preheat of the deuterium–tritium fusible mixture in the capsule, and the ablation front instability, by doping the ablator layer with a small quantity of high Z material. The germanium or bromine doping of the CHx enables the control of the microshell opacity to prevent the preheat of DT from high energetic x rays. Titanium is used to diagnostises the implosion of the target. The coating properties evolve with the amount of dopant incorporated in the CHx matrix. Evolution of the deposition rate, the roughness, the thermal stability, or the optical gap (UV/visible spectroscopy) are studied in this article. Concentration and homogeneity of the dopants are also determined as well as the chemical bindings between the dopants and the hydrocarbon matrix. Many characterizations are done by scanning electron microscopy, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, or Fourier-transform infrared.
Hydrogenation characteristics and observation of disintegration conditions of Ti–Mo and Ni-coated Ti–Mo thin films
Authors: Shi L. Q. , Zhou Z. Y. , Zhao G. Q. , He M. H.
Published: July 2002

The hydrogenation characteristics of the sputtered Ti–Mo (α–β alloy) films (∼900 nm) with and without Ni coating were investigated using high-energy non-Rutherford backscattering (non-RBS) and elastic recoil detection techniques. It was found that the Ti–Mo alloy had a good hydrogen absorption capability compared with pure Ti, and showed a high resistance to C contamination as well. It was also demonstrated that with a top layer of thin Ni film on the Ti–Mo, an improvement in hydrogenation capability was achieved. The non-RBS spectra revealed that the Ni layer reduced the surface contamination of C and O impurities effectively and, therefore, promoted hydrogen absorption activation. On the other hand, there was little change in their maximum hydrogen storage capability with increasing Mo concentration (Mo <20 at. %), and the phases in the samples hydrogenated at 473 K were composed of a δ hydride and a β-solid solution. Once the Mo content approached 20 at. %, the δ phase disappeared and only the β phase existed in the film. The durability of the sputtered films on the Mo substrate against the hydrogen absorption/desorption was also measured with the hydrogen absorption–desorption cycles method, and a significant improvement was obtained.
Aqueous base development and acid diffusion length optimization in negative epoxy resist for electron beam lithography
Authors: Glezos N. , Argitis P. , Velessiotis D. , Raptis I. , Hatzakis M. , Hudek P. , Kostic I.
Published: July 2002

A new aqueous base developable, chemically amplified negative resist based on epoxy chemistry is evaluated for high-resolution, high-speed e-beam lithography. This resist is formulated using partially hydrogenated poly(hydroxy styrene) and epoxy novolac polymers. Degree of hydrogenation controls the aqueous base solubility and microphase separation phenomena. Reduction of edge roughness compared to the pure epoxy systems is observed whereas the absence of swelling phenomena allows lithography up to 100 nm regime and a sensitivity of 4–8 μC/cm2 at 50 keV. The diffusion coefficient has been evaluated both from high-resolution line and dot exposures and it is found to be 5×10−14 cm2/s for the optimal thermal processing conditions selected.
Oxide nanodots and ultrathin layers fabricated on silicon using nonfocused multicharged ion beams
Authors: Borsoni G. , Gros-Jean M. , Korwin-Pawlowski M. L. , Laffitte R. , Le Roux V. , Vallier L.
Published: July 2002

We have used slow multicharged argon ions in ultrahigh vacuum with a partial pressure of oxygen to form ultrathin (subnanometer) oxide dots of a few tens of nanometer diameter on a silicon surface. The main characteristic of this technique is that the incident multicharged ion does not penetrate below the surface, so there is no implantation-induced modifications of the substrate. Thus, we utilized a unique possibility provided by the multicharged ions interaction with surfaces of solids, the noncontact trampoline effect, to open the bonds of hydrogenated silicon, and replace it with oxygen. This article presents the fundamentals of slow multicharged ion interaction with a surface, the experimental multicharged ion beam line build at X-ion laboratory, and obtained results of oxide dot formation on silicon, using them as a mask in a reactive ion etching process to grow three-dimensional crystalline silicon structures. Potential applications are in nanoflash–multidot type nonvolatile memories.
Fracture resistance enhancement of diamond-like carbon/nitrogenated diamond-like carbon multilayer deposited by electron cyclotron resonance microwave plasma chemical vapor deposition
Authors: Qi J. , Lai K. H. , Bello I. , Lee C. S. , Lee S. T. , Luo J. B. , Wen S. Z.
Published: July 2002

Diamond-like carbon (DLC), nitrogenated diamond-like carbon (CNx) and multilayered DLC/CNx films of 350 nm overall thickness were deposited on Si (100) substrates by using an electron cyclotron resonance microwave plasma chemical vapor deposition system. The deposited films were investigated for the fracture resistance using nanoindentation and nanoscratch methods in combination with scanning electron microscopy. In nanoindentation fracture tests, the film fracture was detected by the discontinuities in the load-displacement curves. The abrupt increase in the friction force between the tip and films during nanoscratch fracture tests was taken as a criterion for film fracture. Both the nanoindentation and nanoscratch fracture tests revealed that the DLC/CNx multilayer exhibited substantially higher critical load than that measured for either DLC or CNx films, though there was no obvious enhancement in the multilayer hardness and elastic modulus while the multilayer internal stress was between that of DLC and CNx. This study suggests that the fracture resistance of hard coatings can be improved by the design of a suitable multilayer structure.
Printing characteristics of proximity x-ray lithography and comparison with optical lithography at 100 and 70 nm technology nodes
Authors: Hasegawa M. , Nakayama Y. , Yamaguchi K. , Matsui Y. , Terasawa T.
Published: July 2002

The printing characteristics of proximity x-ray lithography (PXL) were compared with those of ArF and F2 optical lithography using model patterns of memory and logic devices at 100 and 70 nm technology nodes. Aerial-image simulations of both optical lithography and PXL were carried out, and exposure experiments were performed to confirm the simulation results for PXL. Both the aerial images and the exposure results show that PXL has sufficient resolution for patterns with a 100 nm minimum feature size without the need for any additional resolution enhancement techniques (RETs). It exhibits better pattern printing fidelity than either ArF or F2 lithography with strong RETs, such as an alternate-type phase shift mask and off-axis illumination techniques. PXL provides a wide latitude (on the order of microns) in the proximity gap, and is robust with regard to critical dimension errors in mask patterns. For the optical lithography, the fidelity for complex patterns and the narrow depth of focus (DOF) are still issues to be resolved. At the 70 nm node, PXL provides acceptable resolution even at a gap of 10 μm, while F2 lithography requires further advanced RETs to achieve sufficient resolution and an acceptable DOF.
Substrate dependence of InGaAs quantum dots grown by molecular beam epitaxy
Authors: Jiang Weihong , Xu Huaizhe , Xu Bo , Zhou Wei , Gong Qian , Ding Ding , Liang Jiben , Wang Zhanguo
Published: July 2002

A systematic study of self-organized In0.5Ga0.5As quantum dots (QDs) and islands grown by molecular beam epitaxy on (100) and (n11) A/B GaAs substrates is given, where n varies from 1 to 5. Low-temperature photoluminescence results show that the properties of the dots have a strong dependence on the substrate orientation as revealed by atomic force microscopy, consistent with the differences in size, shape, and distribution of QDs on different substrates. From (100) to (111) surface, the photoluminescence peak position of dots on B surfaces is found to blueshift more than that on A surfaces. QDs are also formed on (511) A surface. The positional distribution of these dots exhibits a wavy shape, which is related to the corrugated structure of this surface. Two kinds of islands are formed on (111) A surface, but further work is needed to explain the mechanism of these islands.
Enhanced coercivity by substrate bias configuration in Co-based alloy thin film
Authors: Jin Ding , Wang Jian Ping , Gong Hao
Published: July 2002

Using the substrate bias configuration in a single sputtering process, Co-based alloy triple-layer magnetic thin films were deposited. A coercivity increase was obtained in both room-temperature-deposited and high-temperature-deposited (300 °C) films, and the coercivity was optimized in a NB–B–NB (NB: no bias and B: bias applied in sputtering) type of bias configuration. Dislocation and voids introduced by bias sputtering and the diffusion at the grain boundary and interfaces were proposed to explain the improvement of coercivity. The bias-configured sputtering triple-magnetic-layer structure was suggested as a new approach to improve the magnetic properties, which maintain the advantage of multi-magnetic-layer media.
Pattern characterization of deep-ultraviolet photoresists by near-field infrared microscopy
Authors: Dragnea Bogdan , Preusser Jan , Szarko Jodi M. , Leone Stephen R. , Hinsberg William D.
Published: July 2002

Chemical contrast at subwavelength spatial resolution (λ/10) is achieved using a fiber-based, infrared near-field microscope, at 3 μm wavelength. Chemically amplified polymer photoresists (poly(t-butylmethacrylate)), patterned by ultraviolet radiation and 250 nm thick, are imaged using infrared (IR) wavelengths situated around the OH stretch band of the polymer, a region sensitive to photochemical changes associated with latent image formation. The key technical points that enable near-field infrared absorption measurements down to 0.05% absorption sensitivity are discussed together with the major contrast mechanisms involved in image formation. The measurements are complemented by confirming studies using confocal infrared microscopy and depth profiling. The exposure dose dependence of the acid catalyzed chemistry, after the postexposure bake step, was studied on line/space patterned samples. The OH subgroup absorption maps of the patterned polymer film exhibit features that are not present in the topographical changes (shrinkage) induced by the postexposure polymer chemistry and illustrate significant potential of the IR near-field microscopy as an analytical tool for polymer chemical physics.
Electron emission from silicon tips coated with sol-gel (Ba0.67Sr0.33)TiO3 ferroelectric thin film
Authors: Kang W. P. , Wisitsora-at A. , Davidson J. L. , Tan O. K. , Zhu W. G. , Li Q. , Xu J. F.
Published: July 2002

Electron emissions from arrays of silicon tips coated with barium strontium titanate (BST) (Ba0.67Sr0.33)TiO3 ferroelectric thin film have been investigated. Sol-gel technique was used to prepare the (Ba0.67Sr0.33)TiO3 ferroelectric solution. A conformal and stable (Ba0.67Sr0.33)TiO3 thin film coating of ∼30 nm on silicon tips was achieved by spin coating and thermal annealing. Silicon tips coated with BST ferroelectric film show considerable improvement in electron emission. The coated tips have low turn-on electric fields ranging from 4 to 10 V/μm, which are significantly lower than that of the uncoated silicon tips with turn-on electric field of ∼70 V/μm. Fowler–Nordheim (F–N) plots of the emission data confirm that the emission conformed to F–N emission behavior and indicate that the coated silicon tips have a lower work function than the uncoated silicon tips. Sol-gel ferroelectric thin film coating is an efficient and practical way to improve silicon tip emission behavior.
Carbon nanotube-based electron gun for electron microscopy
Authors: Leopold John G. , Zik Ory , Cheifetz Eli , Rosenblatt David
Published: July 2002

A novel electron-gun design is proposed with a single carbon nanotube grown in a microfabricated conducting crater within a conducting substrate separated by an insulating layer from an apertured gate. The operating field-emission parameters for such a device are chosen from experiments by using geometric scaling resulting from electrostatic arguments. With these parameters the electron-beam formation and propagation was simulated using a ray-tracing code. The novel design produces a nearly parallel electron beam of high source brightness, low-power leakage, and negligible wall encounters, advantageous for microcolumn scanning electron microscopy, lithography, and other applications.
Wedge emitter fabrication using focused ion beam
Authors: Ochiai C. , Sawada A. , Noriyasu H. , Takai M. , Hosono A. , Okuda S.
Published: July 2002

Mo field emitters with a lateral wedge have been fabricated using a dual beam system consisting of a focused ion beam (FIB) and a field emission electron beam. A FIB process was applied to the fabrication of a lateral-type wedge field emitter. An emitter–collector gap for the wedge emitter gap produced by physical sputtering of the Mo layer on SiO2/Si by a FIB and subsequent wet etching of the underlying silicon dioxide layer. Controlled gaps of 10–500 nm could be obtained by raster scanning of a FIB. An emission current of up to 2 μA was observed for a wedge emitter with a gap of 100 nm.
Identification and sizing of particle defects in semiconductor-wafer processing
Authors: Yoo Seong-Ho , Weygand James , Scherer Juergen , Davis Lawrence , Liu Benjamin , Christenson Kurt , Butterbaugh Jeffery , Narayanswami Natraj
Published: July 2002

An experimental study of the sizing of submicron particles on semiconductor wafers is presented. The objective of the study was to determine the accuracy of a state-of-the-art optical wafer scanner, by comparing its size response with that of two well established techniques, namely, differential mobility analysis (DMA) and secondary electron microscopy (SEM). Test particles used include polystyrene–latex spheres and SiO2, Si3N4, W, and Cu particles of 64, 107, and 202 nm nominal (DMA) sizes. The scanner-indicated sizes using the oblique and normal operational modes were compared to the DMA sizes and to average sizes determined from the SEM images. Results show that the scanner-indicated size is comparable to the SEM-indicated size. However, both the scanner size and SEM size exhibit large distributions for a given nominal (DMA) size. The discrepancies are due to a combination of factors such as the effects of particle shape and material, and the presence of larger, doubly charged particles among those analyzed. A comparison of the normal and oblique scanner operational mode results for the scanner further show that the normal mode undersizes particles somewhat. These results collectively indicate that accurate sizing of complex and unknown submicron sized particles on semiconductor wafers is not an easy task. A thorough understanding of the scanner response to a variety of process particles is essential for the meaningful interpretation of scanning results.
Formation of potentially protective oxide-free phosphate films on titanium characterized by valence band x-ray photoelectron spectroscopy
Authors: Rotole John A. , Gaskell Karen , Comte Alex , Sherwood Peter M. A.
Published: July 2002

This paper reports the results of a continuing study focused on preparing novel surface chemistries on metal surfaces. In this paper we report how it is possible to prepare oxide-free titanium metal surfaces protected by a film consisting of phosphate. The surface is prepared by electrochemical treatment in an anaerobic cell which allows electrochemistry to be conducted on samples located in a vacuum system attached to an x-ray photoelectron spectrometer. When a clean metal surface is subjected to electrochemical treatment in aqueous orthophosphoric acid an oxide-free phosphate film can be formed on the metal which is stable on subsequent air exposure. Compositional variations were found with potential and other factors. Identical electrochemical treatment of as-received titanium metal yielded samples that had a surface consisting largely of oxide. The chemical composition of these surface films was studied by core level and valence band x-ray photoelectron spectroscopy. Valence band photoemission interpreted by band structure calculations was found to be especially effective in understanding subtle differences in surface chemistry, enabling the clear identification of phosphate (being able to distinguish between orthophosphate and metaphosphate films) and its distinction from surface oxide. Valance band spectra calculated from band structure calculations for TiO, Ti2O3, TiO2, TiC, TiPO4, and TiP2O7 are reported.
Surface potential measurement with high spatial resolution using a scanning Auger electron microscope
Authors: Sakai Y. , Kudo M. , Nielsen C.
Published: July 2002

The microscopic surface potential distributions were measured from the onset energies of secondary electron spectra using a scanning Auger electron microscope. The spatial resolution is several tens of nanometers and a sensitivity of the surface potential measurement is 0.05 eV. We demonstrated the calibration of the instrument for local surface potential analysis based on the onset energy measurement of the secondary electron spectrum. Several applications of this technique for Ni polycrystal grains of different orientations, and a potential profile along the p–n junction of a light-emitting diode were demonstrated.
Probe diagnostic development for electron beam produced plasmas
Authors: Blackwell D. D. , Walton S. G. , Leonhardt D. , Murphy D. P. , Fernsler R. F. , Amatucci W. E. , Meger R. A.
Published: July 2002

A variety of diagnostics have been fielded in different plasma sources to provide new information about the large area plasma processing system (LAPPS) at NRL. Specifically, a high resolution digital Langmuir probe system and ion flux/energy diagnostics have been employed in pulsed and dc electron beam produced plasmas as well as in an inductively coupled source as a baseline experiment. rf induced dc bias, ion flux, electron and ion temperature, and plasma potential in the proximity of rf powered electrodes placed into these plasmas were measured. It is found that the LAPPS plasma channel is essentially unaffected by the presence of the rf voltage, with the net ion flux unchanging in the presence of rf. These findings are consistent with earlier theoretical models of LAPPS [Manheimer et al., Plasma Sources Sci. Technol. 9, 370 (2000)].
Spatially resolved measurements of the capacitance by scanning tunneling microscope combined with a capacitance bridge
Authors: Arakawa Hitoshi , Nishitani Ryusuke
Published: July 2002

We have measured spatially resolved capacitance between a metal surface and the tip of a scanning tunneling microscope (STM) by using a capacitance bridge combined with STM. The spatial variation of the capacitance can be correlated with the topographic image for the carbon grating and the gold film with a capacitance resolution of about 10 aF (1aF=10−18 F). The observed spatial resolution is about 50 nm along the surface as well as normal to the surface. The spatial resolution of this method is discussed in relation to the STM-tip radius and the corrugation of the sample. The resolution estimated by theoretical calculations is consistent with the experimental results.
High speed, dry etching of Fe for integration of magnetic devices in microelectronics
Authors: Andriesse M. S. P. , van der Drift E. , Sloof W. G.
Published: July 2002

Dry etch behavior of Fe in inductively coupled chlorine-based plasma at elevated temperatures has been investigated. Etch rates up to 300 nm/min at 190 °C were achieved, with good selectivity towards SiO2 and Al2O3 masks. Etching did not take place in pure Cl2 plasma or Ar/Cl2 plasma, but required the addition of a few percent BCl3 or SiCl4. The process was found to be a combination of spontaneous and ion enhanced chemical etching. Simultaneous exposure to ultraviolet light from an external source did not enhance the etch rate, but did shorten the inhibition time of the etching.
Critical dimension error analysis for 0.13 μm photolithography and beyond
Authors: Gau Tsai-Sheng , Yen Anthony , Chen Jeng-Horng , Yu Shinn-Sheng , Chen Chun-Kuang , Ke Chih-Ming , Lin Burn J. , Wang Ping-Ting C.
Published: July 2002

This article reports on a comprehensive study of critical dimension (CD) error analysis for the 0.13 μm generation and beyond. Systematic CD distribution is extracted by averaging nine wafers. The remaining noise signals are treated as random CD errors. Systematic CD error is further broken down into intra- and interfield CD errors by Fourier analysis. Interfield CD error is brought in comparison with the temperature distribution of postexposure bake hot plate, and they are found in good match. A polynomial expansion method further decomposes the interfield distribution into tilt and spiral parts, which are supposedly contributed by hot-plate and spin modules. The random CD error is also analyzed in this article.
Thermomechanical distortions of the PREVAIL mask system during exposure
Authors: Lee P.-T. , Martin C. , Engelstad R. , Lovell E. G. , Robinson C. , Flamholz A.
Published: July 2002

All next-generation lithography (NGL) technologies will be faced with meeting the stringent error budgets for the sub-100 nm regime. One of the major contributors to overlay error in NGL masks is the thermomechanical distortions induced during exposure. The focus of this research is to identify the thermal and structural response of the PREVAIL mask system under typical exposure conditions. Three-dimensional finite element (FE) models were used to simulate the thermomechanical response of the 100 mm PREVAIL prototype mask. Due to the relative size of the pattern features, equivalent modeling techniques were employed for computational expedience. Equivalent thermal properties such as thermal conductivity and thermal emissivity were calculated for the perforated membrane as functions of the void fraction. The resulting mask temperature distributions were used as input into the FE structural model, where equivalent stiffness properties were employed to determine the corresponding thermal displacements. The stitching errors between adjacent subfields were also investigated in this article.
Simulating the response of electron-beam projection lithography masks under standardized mounting techniques
Authors: Chen C.-f. , Engelstad R. L. , Lovell E. G. , Novembre A. E.
Published: July 2002

The mounting standard based upon a proposed four-pad electrostatic chuck for the 200 mm PREVAIL and SCALPEL® masks was assessed to support the electron-beam projection lithography (EPL) mask standardization process. Using numerical simulations, comparative studies were performed to investigate the mask response during fabrication, pattern transfer, and mounting, employing the IBM Falcon/Nighteagle layout as a pattern-specific design for both EPL masks. The results indicated that consistent mounting schemes in the e-beam writer and exposure tool minimized the in-plane distortion (IPD). The proposed chucking configuration appeared to be robust for both EPL technologies for controlling IPD. With additional support enhancement beneath the major strut across the center of the grillage area of the mask, the IPD can be reduced to negligible values.
Influence of sub-100 nm scattering on high-energy electron beam lithography
Authors: Anderson Erik H. , Olynick Deirdre L. , Chao Weilun , Harteneck Bruce , Veklerov Eugene
Published: July 2002

Electron beam lithography tools have evolved in the direction of higher beam energy in order to achieve high-resolution, fine feature definition. As the beam energy is increased, the “forward” scattering is reduced and the “backscatter” range is increased. Over the years, tools became available data 20 then 50 kV, and now 100 kV operation is common. Operation at higher voltages has several advantages, such as better resolution and process latitude due to reduced forward scattering, and a few disadvantages such as higher dose requirements, substrate heating, and lower contrast for backscatter electron alignment and calibration signals (due to reduced primary electron backscattering generation in thin film). The backscatter range for 100 kV on silicon is about 27 μm compared to 8 μm at 50 kV resulting in different strategies for efficient proximity correction. However, even at 100 kV, scattering in an intermediate range is observed and must be taken into account in order to achieve good linewidth control at the highest resolution. Measurements of the scattering range for both 50 and 100 kV have been made using the point exposure distribution measurement technique [S. A. Rishton and D. P. Kern, J. Vac. Sci. Technol. B 5, 135 (1987)]. For comparison, measurements taken on the same wafer at different voltages show that 50 and 100 kV scattering range functions overlap, after normalizing for the different resist sensitivity, at length scales below 0.5 μm, suggesting a common mechanism, which is independent of the initial electron energy. For thin resists, this suggests that the significant resolution difference between 50 and 100 kV lithography is limited to the “forward” scattering effect as the incident electrons traverse the resist. Extrapolating the scattering function to the approximate beam diameter of 10 nm allows an impulse response function to be numerically determined. The convolution of this function gives reasonably good agreement with dose versus linewidth measurements.
Processing and characterization of ultralow-dielectric constant organosilicate
Authors: Yang Shu , Pai Janice C.-H. , Pai Chien-Shing , Dabbagh Gary , Nalamasu Omkaram , Reichmanis Elsa , Seputro Joko , Obeng Yaw S.
Published: July 2002

A class of nanoporous organosilicate has been developed that can reach an ultralow-dielectric constant (k⩽2). In this approach a series of triblock polymers, poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO), are used as sacrificial materials in silicon based spin-on matrices, poly(methylsilsesquioxane) (MSQ) to generate pores when heated above 400 °C. To improve the electrical and mechanical properties, different parameters, such as temperatures, heating rates, polymer molecular weights, copolymer compositions, and the molecular weight of MSQ prepolymers, were studied. Heating temperatures and ramping rates have no large effect on dielectric constants and dielectric breakdown strength. However, at a higher temperature, 500 °C, the mechanical properties are found stronger than those from 400 °C. A higher molecular weight of MSQ prepolymer will also lead to higher mechanical properties of the final porous MSQ, while no temperature effect is observed. Block copolymers with different molecular weights and compositions give similar dielectric constants depending on the polymer loading in MSQ and no substantial change in the dielectric strength of the films with different compositions.
Electron–electron interactions in multibeam lithography columns
Authors: Mankos M. , Sagle A. , Coyle S. T. , Fernandez A.
Published: July 2002

We have used Monte Carlo simulations to evaluate electron–electron (e–e) interactions in multibeam lithography columns. For a linear array of 32 beams with variable length from 40 to 400 μm at the photocathode, the spot size and placement were calculated for total beam currents of up to 800 nA at the substrate. In general, the e–e interactions are reduced when the linear array size is increased, therefore reducing the total beam blur. However, this is not true for placement errors induced by e–e interactions, specifically when the absolute magnitude of the error at the edge of the array is considered. We have used a multibeam test bed, equipped with a magnification stack for high spatial resolution imaging of the photoemission, to evaluate experimentally the effect of e–e interactions.
Electron beam inspection system based on the projection imaging electron microscope
Authors: Miyoshi Motosuke , Yamazaki Yuichiro , Nagahama Ichirota , Onishi Atsushi , Okumura Katsuya
Published: July 2002

An electron beam inspection system based on the projection imaging electron microscope was developed and the proof-of-concept system has been constructed and evaluated. The secondary electrons are projected through the projection imaging optics and imaged onto the image detection system. The projected secondary electron image is amplified by the microchannel plate and converted to an optical image by the fluorescent screen and detected by the 2048 element, eight-tap time delay and integration (TDI) image sensor. The stage is linearly moved in synchronism with the TDI signal output data rate, and then, the secondary electron image is continuously captured. The spatial resolution of around 0.1 μm has been obtained in this experiment. Several images obtained by the TDI imaging mode are also demonstrated.