bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface characterization by Auger electron spectrometry
Authors: Sickafus E. N.
Published: July 2002

Surface characterization encompasses concepts such as chemical composition, coverage, charge transfer in bonding, electron-state densities, and electron energy levels in surface bonds. Information bearing on these concepts can be obtained by direct or indirect inference from Auger electron spectrometry. Five features of Auger electron spectrometry are defined and used to outline this review. The five features are: (i) characteristic energy, (ii) intensity, (iii) peak shift, (iv) linewidth, and (v) line shape. In nearly all applications of Auger electron spectrometry these features and their combinations are monitored for the characterization of surfaces.
Electrical properties of silicon nitride films prepared by electron cyclotron resonance assisted sputter deposition
Authors: Deenamma Vargheese K. , Mohan Rao G.
Published: July 2002

Silicon nitride films have been deposited using electron cyclotron resonance (ECR) plasma-assisted rf sputter deposition. Variation in composition and electrical properties of the deposited films has been studied. Films with specific resistivity of 1013 Ω cm and a dielectric constant of 7 have been obtained at a ECR power of 100 W (corresponding to an ion flux of 1×1010 cm−3). These films exhibited minimum interface density of 2×1010 eV−1 cm−2 and have a critical field of 5 MV/cm. Detailed electrical characterization of the films has been carried out to study the variation of interface density with ECR power and to identify the conduction mechanism.
Effects of the substrate tilting angle on the molecular beam epitaxial growth of GaAs on Si(110)
Authors: Meléndez-Lira M. , Santana-Aranda M. A. , López-López M. , Tamura M. , Yodo T. , Vidal M. A.
Published: July 2002

We have grown GaAs layers by molecular beam epitaxy on Si(110) substrates with different tilted angles towards the [001] direction. The samples where characterized by atomic force microscopy (AFM), high resolution x-ray diffraction (HRXRD), transmission electron microscopy (TEM), and photoreflectance spectroscopy (PR). The full width at half maximum of the HRXRD reflection peaks and the surface roughness determined by AFM decreased as the off angle increased up to 6°. The increase in the crystal quality of the films was confirmed by the TEM measurements. The PR spectra showed the presence of oscillations above the GaAs band-gap signal associated to built-in internal electric fields. The built-in electric field strength and the GaAs band-gap energy values were obtained by employing the Franz–Keldysh model. We obtained band-gap energy values that suggest the presence of residual strains in the films.
Highly reliable chemical–mechanical polishing process for organic low-k methylsilsesquioxane
Authors: Liu Po-Tsun , Chang Ting-Chang , Huang Ming-Chih , Tsai M. S. , Sze S. M.
Published: July 2002

In this work, chemical–mechanical polishing (CMP) of the organic polymer, methylsilsesquioxane (MSQ), has been investigated. For conventional silicate-based slurry, the CMP removal rate of MSQ is low and many scratches are formed at the surface. Moreover, the dielectric properties of a post-CMP MSQ film are degraded in comparison to the as-cured MSQ. We have proposed a reliable process for the CMP of MSQ which includes a slurry of additive and a post-CMP NH3 plasma treatment. Experimental results show that the modified slurry provides a high polishing rate and uniform surface topography. In addition, the NH3 plasma process can form a thin nitrogen-containing layer on the post-CMP MSQ surface, which enhances the resistance to moisture absorption and copper diffusion.
Effects of titanium sputtering schemes and preamorphization on the junction characteristics of Ti salicide
Authors: Kim Sam-Dong , Park Hyun-Chang , Hwang In-Seok , Rhee Jin-Koo , Park Dae-Gyu
Published: July 2002

We studied the effects of Ge preamorphization (PAM) and Ti deposition method on 0.25 μm Ti-salicide junctions in comparison with As PAM. For each PAM scheme, ion implantations are performed at 2E14 ion/cm2 dose and 20 keV energy using As75 and GeF4 ion sources. Ionized physical vapor deposition and collimated type dc-magnetron sputtering are used for depositing ∼300 Å Ti for this study. Ge PAM showed lower sheet resistance (∼48 Ω /sq.) and better within-wafer uniformity than As PAM at 0.25 μm line width of n+/p-well junctions. This is attributed to enhanced C54-silicidation at n+ junction. At p+ junctions, comparable performance in sheet-resistance reduction at fines lines for both As and Ge PAM schemes. Junction leakage current (JLC) levels are below ∼1E14 A/μm2 at area patterns for all process conditions, whereas no degradation in JLC are shown under Ge PAM condition even at edge-intensive patterns. Junction breakdown voltage and contact resistances are satisfactory at all process conditions.
Incorporating a corner correction scheme into enhanced pattern area density proximity effect correction
Authors: Ea C. S. , Brown A. D.
Published: July 2002

Enhanced pattern area density proximity effect correction (EPADPEC) is an algorithm for performing electron proximity effect correction for direct write electron beam systems. The algorithm is described in C. S. Ea and A. D. Brown [J. Vac. Sci. Technol. B 17, 323 (1999)]. In this article, we describe a corner correction scheme for EPADPEC. The scheme reduces the pullback radius and the absolute area difference at shape corners by at least a factor of 2, at a computation cost increase of 1.7–5.9.
Infrared frequency selective surfaces fabricated using optical lithography and phase-shift masks
Authors: Spector S. J. , Astolfi D. K. , Doran S. P. , Lyszczarz T. M. , Raynolds J. E.
Published: July 2002

A frequency selective surface (FSS) structure has been fabricated for use in a thermophotovoltaic system. The FSS provides a means for reflecting the unusable light below the band gap of the thermophotovoltaic cell while transmitting the usable light above the band gap. This behavior is relatively independent of the light’s incident angle. The fabrication of the FSS was done using optical lithography and a phase-shift mask. The FSS cell consisted of circular slits spaced by 1100 nm. The diameter and width of the circular slits were 870 and 120 nm, respectively. The FSS was predicted to pass wavelengths near 7 μm and reflect wavelengths outside of this pass band. The FSSs fabricated performed as expected with a pass band centered near 5 μm.
Alternating stress field and superhardness effect in TiN/NbN superlattice films
Authors: Geyang Li , Zenghu Han , Jiawan Tian , Junhua Xu , Mingyuan Gu
Published: July 2002

In order to study the superhardness effect of superlattice films, a series of TiN/NbN superlattice films with various modulation periods were synthesized by reactive sputter deposition. X-ray diffraction analysis, transmission electron microscopy, and microhardness analysis were employed to characterize the modulation structure, interface structure and microhardness of these superlattice films. The results show that TiN/NbN films possess good periodic modulation structure and the modulation interfaces are straight and clear. The superlattice films have a face-centered-cubic polycrystalline structure resulting from epitaxial growth. They assume unusual microhardness which can reach a peak value of HK 39.0 GPa at a modulation period of 8.3 nm. It is considered by analysis that the superhardness effect of TiN/NbN superlattice films results from the strengthening effect of an alternating stress field, which is caused by the epitaxial growth of two kinds of materials with different lattice constants.
Relaxed SiGe-on-insulator fabricated via wafer bonding and etch back
Authors: Taraschi Gianni , Langdo Thomas A. , Currie Matthew T. , Fitzgerald Eugene A. , Antoniadis Dimitri A.
Published: July 2002

Relaxed SiGe-on-insulator (SGOI) was fabricated using a bond/etch-back process. Ultrahigh-vacuum chemical vapor deposition was used to grow a SiGe graded buffer on a Si substrate, creating a relaxed Si0.75Ge0.25 virtual substrate. The SiGe graded buffer surface was then polished, and a second ultrahigh-vacuum chemical vapor deposition growth was performed to deposit a strained Si etch stop layer followed by a Si0.75Ge0.25 layer. The wafers were bonded to oxidized Si handle wafers, and the wafer pairs were annealed. The backsides of the SiGe virtual substrates were ground and etched in KOH. Since the KOH etch stops at the 20% Ge region in the graded layer, the remaining SiGe was then removed using a HF:H2O2:CH3COOH (1:2:3) solution. The resulting SGOI structure was characterized using transmission electron microscopy and atomic force microscopy; in addition, etch-pit density measurements revealed a threading dislocation density of about 105 cm−2.
The Sputtering of Nickel–Chromium Alloys
Authors: Patterson W. L. , Shirn G. A.
Published: July 2002

Ni-Cr alloys having the compositions (in at. %) Ni-22 Cr, Ni-42 Cr, and Ni-80 Cr were sputtered in argon in a low-pressure supported discharge. Ion energy was varied from 200 to 1000 eV, ion current density from 0.1 to 0.8 mA/cm2 and pressure from 2 to 6 μ. The ion-pumped sputtering tube was processed as a uhv system. Thin films were deposited on polished silicon, aluminum or sapphire. Results showed that the target composition was preserved in the sputtered films to within ± 1% in each component. Near the surface of the sputtered Ni-22 Cr target, a relative Cr enrichment was found. The alloy sputtering process has been codified in a phenomenological continuity equation, using sputtering yields as parameters. The equation gives quantitatively a transient-state and a steady-state solution. The steady-state solution shows that the sputtered film should have the same composition as the target bulk and that the surface of the target should, in general, change composition.
Excitation-energy-dependent resonances in x-ray emissions under near-threshold electron excitation of the Ce 3d and 4d levels
Authors: Chamberlain M. B. , Baun W. L.
Published: July 2002

Soft x-ray appearance potential spectra of the 3d and 4d levels of polycrystalline cerium metal are reported in this paper. Resonant x-ray emissions are observed when the electron-excitation energy sweeps through the ionization energies of the 3d and 4d levels. The resonant x rays excited at the 3d-level onsets are considerably more intense, and are excited at a lower electron-excitation energy than the 3d-series characteristic x rays. In the neighborhood of the 4d-electron thresholds, four line-like structures extend to ∠8 eV below the 4d-electron binding energies, while two broad and more intense structures occur above the 4d onsets, with the largest one reaching a peak intensity at 12 eV above the 4d thresholds. The resonant emissions apparently arise from the decay of threshold-excited states which are bound to the inner vacancy and have core configurations nd94f3, (n=3,4). The exchange interaction between the three 4f electrons and the respective d-orbital vacancy spreads the 4d-threshold structures over a 20 eV range of excitation energies and the 3d-threshold structures over a much smaller range.
Synthesis and characterization of yttrium oxide (Y2O3) deposits
Authors: Colen M. , Bunshah R. F.
Published: July 2002

The synthesis of yttrium oxide (Y2O3) was accomplished by evaporating elemental yttrium in the presence of oxygen. High-rate physical vapor deposition was employed using both the reactive evaporation (RE) and activated reactive evaporation (ARE) processes. The ARE process resulted in a higher Y2O3/Y ratio for two reasons—more complete reaction and fewer globules of Y being ejected from the molten pool and landing on the deposit surface. The microstructure and mechanical properties of the deposit produced varied with the deposition temperature in accordance with the structural zone model of Movchan and Demchishin. Over a deposition temperature range of 121° to 721 °C, the surface energy, as determined by Hertzian fracture, varied from 645 erg/cm2 to 515 erg/cm2, and the microhardness varied from 320 kg/mm2 to 502 kg/mm2.
Reconstruction of stepped nickel surfaces
Authors: Thapliyal H. V. , Blakely J. M.
Published: July 2002

The morphology of stepped surfaces of nickel has been studied using LEED and AES. LEED study reveals some morphological transitions which are reversible with temperature cycling. At high temperatures the stepped surfaces have arrays of monoatomic height steps. At low temperatures an increase in ordering takes place for clean and carbon covered surfaces. For the case of clean surfaces, steps coalesce to form multiatom height steps. The surfaces are faceted in the presence of carbon as an adsorbate, while step coalescence is inhibited by sulfur adsorption. These transitions are believed to be caused by strong interaction among steps.
EL-3: A high throughput, high resolution e-beam lithography tool
Authors: Moore R. D. , Caccoma G. A. , Pfeiffer H. C. , Weber E. V. , Woodard O. C.
Published: July 2002

EL-3 is IBM’s third generation of e-beam lithography tools developed for the fabrication of semiconductor devices using direct write techniques. The system is designed to operate as a direct write manufacturing tool in a semiconductor factory. EL-3 has a high throughput capability that is competitive with many optical lithography systems. The system has the capability to cover the lithography requirements at 1 μ and above. In addition, the tool can be operated as a highly effective mask maker. EL-3 makes use of many of the state of the art techniques associated with electron beam system lithography. These techniques include (1) LEARN calibrated field scan, (2) high current, variable shaped spot, (3) dual channel deflection of large fields and of subfields, (4) high performance handling of large workpieces (6 1/2 in., 163 mm), and (5) Series/ 1 data handling, system control, and automatic operation EL-3 can expose 30 4 in. (100 mm) wafers per hour at 1.5 μ lithography at 10 μC/cm2 current dose. Four EL-3 tools have been completed and installed. These tools are being used for both development and manufacturing applications. The system and lithography performance achieved with these tools will be discussed, with SEM results shown for various process conditions and different resist materials.
Chemical bonding and charge redistribution: Valence band and core level correlations for the Ni/Si, Pd/Si, and Pt/Si systems
Authors: Grunthaner P. J. , Grunthaner F. J. , Madhukar A.
Published: July 2002

Via a systematic study of the correlation between the core and valence level x-ray photoemission spectra, the nature of the chemical bonding and charge redistribution for bulk transition metal silicides has been examined. Particular emphasis is placed on Pt2Si and PtSi. It is observed that the strength of the metal (d)–silicon ( p) interaction increases in the order Ni2Si<Pd2Si<Pt2Si. It is also observed that both the metal and silicon core lines shift to higher binding energy as the silicides are formed. The notion of charge redistribution for metallic bonds is invoked to explain these data.
Polar-on-nonpolar epitaxy: Sublattice ordering in the nucleation and growth of GaP on Si(211) surfaces
Authors: Wright Steven L. , Inada Masanori , Kroemer Herbert
Published: July 2002

When a binary compound with two different atoms per primitive cell is grown on a lattice- matched elementary substrate in which the two atoms are identical, there exists an inherent ambiguity in the nucleation of the compound, with two different possible atomic arrangements, distinguished by an interchange of the two sublattices of the compound. For defect-free growth, one of the two possible nucleation modes must be suppressed. The problems involved in doing so depend very strongly on the crystallographic orientation of the substrate; for most orientations they are greatly complicated by the additional problem of electrical neutrality at the resulting polar/nonpolar interface. For zincblende-on-diamond growth, the (211) orientation is potentially one of the most promising orientations to overcome both classes of problems. The simplest possible atomic configuration for this orientation exhibits two different classes of bonding sites, some with one dangling bond, some with two, in the correct arrangement to create a strong preference for one of the two atomic configurations. We have grown GaP on Si (211) by MBE. Etching studies have indicated that (under the proper nucleation conditions) the growth is largely free of antiphase disorder, and that the sublattice ordering corresponds to P-atoms bonded to those interface sites that have two back bonds to Si. The likely nucleation sequence is discussed.
Fermi-level pinning and chemical structure of InP–metal interfaces
Authors: Brillson L. J. , Brucker C. F. , Katnani A. D. , Stoffel N. G. , Daniels R. , Margaritondo G.
Published: July 2002

We have used soft x-ray photoemission spectroscopy (SXPS) to investigate the dependence of Fermi-level pinning on chemical structure at InP–metal interfaces. SXPS core level spectra of Al, Ti, Ni, Au, Pd, Ag, and Cu on UHV-cleaved InP(110) surfaces reveal evidence for semiconductor outdiffusion, metal indiffusion, metal-anion bonding and metal-cation alloying. Corresponding Fermi-level movements indicate a range of pinning positions at significantly different energies within the n-type InP band gap. These results demonstrate that the Schottky barrier heights depend sensitively on changes in interface chemical bonding and diffusion, which strongly affect the type of electrically active sites and interfacial layers formed.
Calibration of molecular drag vacuum gages
Authors: McCulloh K. E.
Published: July 2002

In spinning-ball molecular drag gages, the logarithm of the rotational frequency varies linearly with the time integral of the applied pressure under conditions of free molecular motion. An orifice flow standard for calibrating these devices has been developed that passes a measured quantity of gas through the calibration chamber in typically 30 min. The time integral of the calibration pressure can be calculated with an estimated uncertainty less than 1%. A number of gage balls operated in conjunction with three controllers have been calibrated for N2, Ar, and He using this system. Conditions and procedures affecting the performance characteristics of these gages have been investigated, including magnetization of the ball, baking and other conditioning of its surface, and degradation of gas purity by surface contaminants in an unbaked flow system.
Fabrication and characterization of superconducting Pb alloy deposited at −80 °C
Authors: Young P. L. , Josephs R. M. , Stein B. F. , Flannery W. E. , Wang T. C. , Sheppard J. E. , Wetterskog H.
Published: July 2002

In lead alloy Josephson junction integrated circuits, two major problems often lead to device failures. In the region of electrode crossings, poor step coverage can cause shorts between the base electrode and the counterelectrode as well as opens in the counter electrode. Hillock formation on the lead alloy as a result of thermal cycling can rupture the thin oxide barrier. Deposition of the base electrode of the Pb alloy Josephson junction at −196 °C yields films with very fine grains which significantly reduce the problem of hillock formation, at the expense of very stringent requirements on the chamber pressure of the vacuum system. These problems have been alleviated in the present work by depositing the base electrode of the lead alloy Josephson junction on a rotating substrate holder, held at −80 °C, with relatively modest vacuum requirements.
Thermal oxidation of InAsxP1−x
Authors: Schwartz G. P. , Thiel F. A. , Gualtieri G. J.
Published: July 2002

The present Raman scattering study has examined thermally oxidized films on polycrystalline InAsxP1−x for inclusions of Group V based metalloids such as elemental As, P, or AszP1−z. Substrate compositions with x=0.63 and 0.36 were examined. On the alloy with high arsenic content (x=0.63), elemental arsenic was detected in air oxidized films grown at temperatures between 400 and 650 °C. For this alloy composition, the identification of an additional phase involving AszP1−z is hampered by the overlap of its vibrational mode spectrum with modes originating from the substrate. For the alloy with x=0.36, the formation of AszP1−z appears to dominate over the formation of elemental As, although both products can be detected in air oxidized films grown at 650 °C. Of the many possible oxide phases potentially present, only InPO4 could be identified.
1/ f noise in p-n junction diodes
Authors: Kleinpenning T. G. M.
Published: July 2002

A survey is given of the recent literature on 1/ f noise in p-n junction diodes. Two models for the explanation of 1/ f noise are discussed: Hooge’s model assuming mobility fluctuations and McWhorter’s model assuming number fluctuations. Relations for the magnitude of the 1/ f noise based on Hooge’s model are presented for several types of diodes: diffusion current dominated diodes, GR current dominated diodes, long and short diodes, and illuminated photodiodes. These relations are compared with experimental results obtained from diodes made of Si, GaP, and (HgCd)Te. The agreement between experiment and calculated relations is often found to be satisfactory, both for forward and reverse-biased diodes and for illuminated diodes. 1/ f noise relations based on McWhorter’s model are scarce, moreover, they do not sufficiently describe the 1/ f noise in diodes.
Laser ablation of polymers
Authors: Yeh J. T. C.
Published: July 2002

Recently, there has been increasing interest in direct ablation of materials by short-pulse laser beams. Materials under study vary from thin metal films, metal and semiconductor compounds, and inorganic insulators to polymers, including human hair and photoresists. In this paper, a review of the UV laser ablation of polymers is presented. Srinivasan pioneered in the field of polymer ablation by far-UV (193-nm) pulses. Subsequently, polymer ablation with lasers at a few longer wavelengths has been reported. To date, understanding the etching mechanism and identifying the contributions from photochemical and photothermal activities continue to be the outstanding challenge. The technological issues and the material etching behavior, which varies with laser frequency, fluence, laser pulse length, and material optical absorption, will be discussed for microelectronic applications.
Optical emission and laser-induced fluorescence diagnostics in reactive plasmas
Authors: Miller Terry A.
Published: July 2002

An overview of optical diagnostic techniques for low pressure cold plasmas, such as those used in the electronics industry, is presented. Two different aspects of optical emission are considered. In the first, commonly called actinometry, species concentrations are inferred from line intensities, while in the second, translational energies are inferred from linewidths and shifts. In addition, consideration of the advantages of laser-induced fluorescence techniques is given.
High-speed scanning tunneling microscopes
Authors: Gregory S. , Rogers C. T.
Published: July 2002

We are developing scanning tunnel microscopes (STM’s) with which we have attained near-video frame rates. Such rates are necessary for the study of many surface-dynamic phenomena. One microscope uses a thermally stable twelve-piezo-grid ‘‘walker’’ for coarse and fine positioning and scanning. A vertical ‘‘inchworm’’ is used for coarse positioning of the tip. As part of our study of STM design possibilities we have operated an instrument in which crossed graphite fibers form the junction. This instrument has unique properties which shed light on the nature of extremely small vacuum tunnel junctions.
A new symmetric scanning tunneling microscope design
Authors: Davidsson P. , Claeson T. , Pehrson S.
Published: July 2002

A new scanning tunneling microscope (STM) where the traditional xyz tripod is replaced with a central post activated by three symmetrically arranged piezo elements has been built. The sample and the tip are mounted in two easily exchangeable snap-in mounted holders, both accessible from the same side and with one single tool. The sample stage is activated by three differential screws corresponding to the same coordinate axes as the piezo elements. The STM is mounted on a single UHV flange and will fit into a 4-in.-diam vacuum chamber.
An ultrahigh vacuum scanning tunneling microscope with interchangeable samples and tips
Authors: Chiang S. , Wilson R. J. , Gerber Ch. , Hallmark V. M.
Published: July 2002

Our ultrahigh vacuum scanning tunneling microscope (STM) is the first instrument in which both the samples and tips can be replaced in situ and analyzed by routine surface analysis techniques. The STM chamber is connected by a transfer chamber to a VG Escalab surface analysis system equipped with scanning Auger microscopy/scanning electron microscopy, x-ray photoemission spectroscopy, low-energy electron diffraction, and sample cleaning and preparation facilities. We describe the design of the instrument in detail and show high-resolution data which exemplify its performance and lead to determinations of the structure of several surfaces: ((3)1/2×(3)1/2) R30° Ag/Si(111), ((19)1/2×(19)1/2) R23.4° Ni/Si (111), and Au(111) thin films on mica.
Electrohydrodynamic ion emission from molten lithium nitrate
Authors: Panitz J. A. , Pregenzer A. L. , Gerber R. A.
Published: July 2002

Positive ions have been generated at the surface of molten lithium nitrate by applying a high electrostatic field to a thin layer of the molten salt on the apex of a field emitter tip. The ion emission process is characteristic of electrohydrodynamic ion formation, usually observed when a high electric field is applied to the surface of a liquid metal or alloy. With molten lithium nitrate, a single emission site appears at threshold. The divergence of the ion beam is several degrees. At higher field strengths multiple emission sites are observed. An ion species at m/e=76 amu dominates the mass spectrum at all field strengths. This species is identified as a cluster ion (LiNO3 )Li+ . At low source temperatures, (LiNO3 )2 Li+ is also observed. Despite the low ionization potential of lithium (5.4 eV), Li+ accounts for <8% of the total ion current generated by the source under all operating conditions. Multiply charged lithium is not detected in the mass spectra, suggesting the electric field at the Taylor cone apex is not sufficient to field-ionize singly charged species by a postionization process.
Chemical effects in the carbon K
V
V Auger line shapes
Authors: Ramaker David E.
Published: July 2002

We review the results of a consistent quantitative interpretation of the C KVV Auger line shapes of five different gas phase hydrocarbons (methane, ethane, cyclohexane, benzene, and ethylene), three solids (polyethylene, diamond, and graphite), and a molecularly chemisorbed system (ethylene/Ni). The normal kvv line shape accounts for only about one-half of the total experimental intensity for most of the Auger line shapes. The remaining part of the experimental line shape can be attributed to satellites resulting from resonant excitation or dynamic screening processes. The normal kvv Auger line shapes are seen to reflect delocalized holes; however, correlation effects are very evident. Although these screening and correlation effects complicate the interpretation of the line shapes, they provided a means to obtain unique chemical, electronic, and bonding information, and indeed cause the principal differences seen among the experimental line shapes.
Divergence measurements for characterization of the micropatterning quality of broad ion beams
Authors: Huth Ch. , Scheer H.-C. , Schneemann B. , Stoll H.-P.
Published: July 2002

For characterization of the micropatterning qualities of broad ion beam systems we introduce the concept of internal divergence in terms of the ion incidence angle distribution at a point of the processing plane. Methods for determination of this quality are discussed, and measurements are carried out for argon and oxygen for two different ion beam systems. Internal divergence is measured with a two-stage Faraday cup assembly. Results for the divergence angle range from 3° to 9° for Ar as an operating gas, and the values for O2 are 10%–20% lower and show the same dependence on operating conditions of the source. Internal divergence within the beam center region is in good agreement with measured divergence values from literature, but deviates at the beam periphery. Divergence angles there are different primarily due to the discharge chamber plasma inhomogeneity. At high angular resolution of the two-stage cup the beamlet structure of a broad beam can be revealed in both ion beam density and ion incidence angle. Consequences for the processing parameters of ion beam systems in micropatterning are deduced. Local measurement of the internal divergence within the processing plane turns out to be an adequate characterization of an ion beam system for large area etching applications.
Metalorganic chemical vapor deposition of aluminum from trimethylamine alane using Cu and TiN nucleation activators
Authors: Gross M. E. , Cheung K. P. , Fleming C. G. , Kovalchick J. , Heimbrook L. A.
Published: July 2002

High purity Al films have been deposited on TiN and in situ evaporated Cu films on Si in a cold wall low pressure metalorganic chemical vapor deposition reactor using trimethylamine alane. TiN and Cu serve as nucleation layers for Al deposition to replace the commonly used but corrosive TiCl4. Al films deposited on TiN at 250 °C exhibit highly textured (111) orientation, whereas those grown on Cu at 150–350 °C are randomly oriented with some preferential growth in the (100) direction. These films are compared with films grown on Si and SiO2 using TiCl4 activation. Cu serves the additional purpose of diffusing into the Al during deposition to improve the electromigration resistance of the films. Electrical resistivities of the Al films on TiN are 4–6 μΩ cm, roughly twice that of bulk Al. The variation of film morphology with deposition temperature, substrate, and precursor pressure is discussed.
Process compatibility in integrated processing of semiconductor devices in multichamber systems
Authors: Lucovsky G. , Kim S. S. , Fitch J. T. , Wang Cheng , Rudder R. A. , Fountain G. G. , Hattangady S. V. , Markunas R. J.
Published: July 2002

This paper reviews recent results with respect to formation of heterostructure devices in multichamber processing environments with in vacuo surface analysis diagnostics and in situ process monitoring. The emphasis is on the formation of two types of thin film device structures (i) gate stacks for metal–oxide–semiconductor (MOS) devices, including field effect transistors (FETs) and (ii) semiconductor thin film devices including amorphous Si thin film transistors (TFTs) and p-i-n diodes. Thin films of the dielectric and semiconductor materials for these structures have been deposited by low-temperature, remote plasma-enhanced chemical vapor deposition (PECVD). A key step in the processing of these devices is the formation of electronically active interfaces between the various constituent layers. For the MOS structures this generally requires preparation of the semiconductor substrate prior to the deposition of the dielectric film. Our studies indicate that this final substrate processing step is crucial to electrical quality the semiconductor/dielectric interface, and should generally be performed in the same chamber as the dielectric deposition. This observation has prompted us to re-evaluate design criteria for the individual processing chambers in multichamber systems in the context of requiring that chambers dedicated to film deposition should also provide the internal fixtures, gas flow and pressure control that are necessary for substrate processing as well as film deposition.
Imaging atom-probe analysis of an aqueous interface
Authors: Stintz Andreas , Panitz J. A.
Published: July 2002

Aqueous solutions of KCl in contact with tungsten and gold surfaces have been examined for the first time by imaging atom-probe (IAP) mass spectroscopy. The liquid is preserved for IAP analysis by rapidly freezing it on the surface of a field-emitter tip. The tip and the resulting vitreous layer of ice are cryogenically transferred into vacuum where an electric field of ∼10 V/nm is used to field desorb the ice layer from the tip apex at 80 K. Mass spectra of the resulting ions are dominated by peaks at m/z=18 amu (H2 O+ ) and m/z=40 amu (K+ ). The desorption process is characterized by an abrupt onset of ionization during which the entire layer is removed from the tip apex. Desorption characteristics suggest that a layer of vitreous water ice behaves like an insulating film on the tip surface. Desorption images taken as the ice layer is removed show no ordering of water or salt molecules within the layer on a nanometer scale.
Reactive sputtering with an unbalanced magnetron
Authors: Howson R. P. , Ja’fer H. A.
Published: July 2002

An unbalanced magnetron uses changes in the configuration of the magnetic field, which confines the plasma close to the sputtering cathode, to allow some of it to ‘‘leak’’ out to impinge on the substrate. An isolated or insulating substrate will acquire a negative bias and be subject to an ion bombardment at that potential. The creation of biases of up to 100 V with a current of 100 mA is reported. The dependence of the surface bombardment on process parameters such as magnetron power and gas pressure has been evaluated; a general diminution of the bombardment occurs as the pressure is increased beyond 1 mTorr, but the effect becomes greater when oxygen replaces argon as the sputtering gas. The operation of the magnetron under conditions using extra electron injection is shown to result in additional ion current, whilst the bias potential is maintained. The application of such a device to the preparation of thin films of diamond-like carbon, indium–tin oxide, silicon oxide and nitride, and titanium nitride and oxide is described. The etching of a polymer using the unbalanced magnetron as an ion gun is also reported.
Mass spectrometric ion analysis in the sputtering of oxide targets
Authors: Ishibashi K. , Hirata K. , Hosokawa N.
Published: July 2002

Species and energies of impinging ions at the substrate during sputtering were analyzed with a quadrupole mass spectrometer combined with an energy analyzer for different targets of Y1Ba2Cu3O7−x (YBCO), InSnO+5wt %SnO (ITO), ZnO, Pb1Zr0.5Ti0.5O3 (PZT), and Ba1Cu2Ox (BCO). In every target the argon positive ion flux was most intensely observed. Relative intensities of the dominant positive ionized sputtered atoms, normalized by the argon positive ion flux, were 0.3% to 4.5%. The dominant negative ion flux was oxygen negative ions (16O−). Relative intensities were 13% and 18% for YBCO and BCO, respectively. For ITO, ZnO, and PZT, however, they were 0.26% to 0.36%. These results qualitatively agreed with the model of negative-ion formation based on ionization potential and electron affinity values. Emission of a large amount of the oxygen negative ions from the target was a distinguishing feature of Ba containing oxide targets.
Auger electron spectroscopy, x-ray photoelectron spectroscopy, and electron energy-loss spectroscopy studies of MoSi2
Authors: Rastogi R. S. , Vankar V. D. , Chopra K. L.
Published: July 2002

Thin films of MoSi2 synthesized by solid state reaction of Mo/Si(111) structure were investigated by Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS) and electron energy-loss spectroscopy (EELS). In AES spectra of Si LVV of MoSi2 and Si(111), the peak shape changes have been assigned to silicide formation and the associated chemical bonding. XPS studies of Mo(3d), Mo(4p), and Si(2p) core level shows significant shifts due to silicide formation. Valence level spectrum of these films shows the dominating features of metal ‘‘d’’ bands. EELS studies show the distinct shifts in bulk plasmon, surface plasmon and interband transitions as a result of silicide formation. The shifts in EELS spectra of core level have been correlated with XPS results. Using the observed transitions in valence level and core level by EELS and XPS, an energy level diagram of MoSi2 has been proposed.
Photoemission study of diamond (100) surface
Authors: Wu J. , Cao R. , Yang X. , Pianetta P. , Lindau I.
Published: July 2002

The electronic structure of the diamond C(100)-(2×1)/(2×2) has been investigated by means of angle-resolved photoelectron spectroscopy for the first time. A surface-related shift has been observed in the C 1s core-level spectrum. The surface-state band dispersion was measured along the symmetry axis Γ–J′ in the surface Brillouin zone. For k∥=0, there is a very pronounced surface state 1.5 eV below Fermi level EF , and it disperses downwards with increasing k∥. Near the boundary of the surface Brillouin zone J′, we find two states with binding energies of 1.9 and 2.4 eV with respect to EF .
Amorphous and polycrystalline silicon films deposited by electron cyclotron resonance reactive plasma deposition
Authors: Knox R. D. , Dalal V. , Moradi B. , Chumanov G.
Published: July 2002

We describe the preparation and properties of hydrogenated amorphous silicon (a-Si:H) and polycrystalline Si (poly-Si) films deposited by electron cyclotron resonance (ECR) reactive plasma deposition. Hydrogen radicals are generated in a physically remote ECR plasma source and are allowed to interact with silane near the growth surface. By controlling the flux of reactive hydrogen species, polycrystalline and amorphous silicon films were systematically grown. Poly-Si films having large Hall mobilities of 35 cm2/V s were deposited at temperatures as low as 450 °C without subsequent annealing. High-quality a-Si:H films were deposited at temperatures as high as 450 °C. Plasma properties near the growth surface were characterized using both optical emission spectroscopy and Langmuir probe techniques.
In situ scanning tunneling microscopy study of platinum (110) in a reactor cell at high pressures and temperatures
Authors: McIntyre B. J. , Salmeron M. , Somorjai G. A.
Published: July 2002

With a specialized version of a scanning tunneling microscope which allows us to study in situ the atomic structure of surfaces under variable pressures (ultrahigh vacuum—atmospheric) and temperatures (300–425 K), we have investigated the structures of the initially clean (110) surface of single crystal platinum while in environments of hydrogen, oxygen, and carbon monoxide. The surface in 1.6 atm of hydrogen appears to be dominated by various sizes of nested missing-row reconstructions. The surface in 1 atm of carbon monoxide, however, does not have the small scale missing-row reconstructions, but does appear to have flat terraces separated by multiple height steps. The surface in 1 atm of oxygen appears to have enlarged (111) microfacets.
Oxygen detection in thin silicon dioxide layers by low-energy x-ray fluorescence spectrometry
Authors: Kirby Robert E. , Wherry David , Madden Michael
Published: July 2002

Light element detection using low-energy (<2 keV) x-ray fluorescence (XRF) is described. By tuning the energy of the incident x rays to slightly above the absorption edge, the minimum detection limits for low-Z elements can be greatly improved over conventional XRF and signal-to-background is significantly better than that obtainable for electron-excited x-ray spectra using an energy-dispersive detector. In particular, the minimum detectable thickness of SiO2 is experimentally determined to be 0.36 Å (≊0.1 monolayer) film thickness for 1.85 kV anode voltage using a Mg anode with an Al window. Good signal linearity with film thickness is established by comparison with measurements obtained on the same samples using ellipsometry and x-ray photoelectron spectroscopy.
Removing the energetic neutral problem in sputtering
Authors: Window B.
Published: July 2002

The evidence for the reflection of neutral inert gas atoms from the target being bombarded during sputter deposition is reviewed. This evidence includes theory, effects at the target, such as measurements of the fraction of incident energy which enters the target from bombarding ion beams, and effects at the growing film, such as the heating effect, the production of stress, the emission of secondary electrons, and the burial of inert gas atoms. New results are reported for the burial of energetic neutral atoms in simple metals in discharges in argon, krypton, and xenon. These results confirm the presence of a high flux of highly energetic neutrals when the sputter atom is substantially less massive than the target atom, leading to the inert gas being included substitutionally at high concentrations in the growing film. To achieve high purity in sputtered films with heavy atomic materials, xenon rather than argon should be used as the sputter gas. A rethink of sputter plant design shows that this expensive gas can be used economically, with some interesting consequences. The performance of a small system based on this rethink is described.
Reactive ion etching of a-SiC:H films using CCl4 and O2 gas mixture
Authors: Lo T. C. , Huang H. C.
Published: July 2002

Reactive ion etching (RIE) of a-SiC:H thin films in a CCl4/O2 plasma has been investigated. The effects of process parameters, in particular radio-frequency power, oxygen addition, gas flow rate, interelectrode spacing, and pumping speed, on a-SiC:H etch rate and a-SiC:H/oxide etch selectivity are reported. For the RIE of a-SiC:H in CCl4/O2 plasmas, the gas phase plasma chemistry and surface reactions appear to be more important than ion bombardment. Reactive species generated from neutral chemical reactions of oxygen in the discharge play a more dominant role than those generated from the electron impact dissociation processes.
Investigation of roughened silicon surfaces using fractal analysis. I. Two-dimensional variation method
Authors: Spanos L. , Irene E. A.
Published: July 2002

A two-dimensional variation method was used to examine the fractal nature and extract the fractal dimension of rough silicon surfaces prepared by chemical etching and rapid thermal chemical vapor deposition. The measurement of the topography was made with an atomic force microscope and the analysis included traditional characterization parameters as well as fractals. Our results show that the surfaces under investigation exhibited fractal behavior and that the variation method is well suited to extract the fractal dimension from atomic force microscopy data.
Kinetic and mechanistic study of the chemical vapor deposition of titanium dioxide thin films using tetrakis-(isopropoxo)-titanium(IV)
Authors: Fictorie Carl. P. , Evans John F. , Gladfelter Wayne L.
Published: July 2002

The mechanism of TiO2 thin film deposition on single crystal TiO2 by chemical vapor deposition (CVD) using tetrakis(isopropoxo)titanium(IV) (TTIP) has been investigated. The structure of the rutile(100) surface has been shown to form a 1×3 reconstruction using reflection high-energy electron diffraction. Temperature programmed reaction spectroscopy and molecular beam scattering have been employed to probe the kinetics of the reaction of TTIP and to identify reaction products. The deposition mechanism involves two parallel pathways to form TiO2: at lower temperatures (500–650 K) propene and isopropanol are formed as products; at higher temperatures (≳650 K) propene and water are formed as products in a second pathway that becomes dominant. An activation energy of 57±8 kJ/mol has been measured for the first pathway. The results for the single crystal surface are compared to earlier work on polycrystalline substrates.
Energetic particles in the sputtering of an indium–tin oxide target
Authors: Tominaga K. , Chong M. , Shintani Y.
Published: July 2002

Energetic negative ions and neutral atoms were simultaneously observed using a time-of-flight apparatus during indium–tin oxide (ITO) film preparation by conventional planar magnetron sputtering of an ITO target. The sputtering was performed in pure Ar gas and compared with ZnO: Al sputtering. Energetic particles such as O− and O−2 ions and neutral O atoms were detected in the time-of-flight spectra, although the flux intensity of these particles was much less than that found in the ZnO sputtering. It was also found that other particles exist at the same time, which were thought to be reflected Ar atoms or O−3 ions from the target surface. However, the flux intensity of these particles was found to be less than that of the energetic O− ions and O atoms. The strong energetic particles, which primarily bombarded the substrate during the ITO sputtering were found to be energetic O− ions and O atoms.
Effect of the predecomposition of SiF4 on the properties of silicon dioxide deposited at low temperatures using SiF4/SiH4/N2O in a double-plasma process
Authors: Alonso J. C. , Ortiz A. , Falcony C. , García M.
Published: July 2002

A low-temperature (250 °C) plasma deposition process has been developed to prepare silicon dioxide films using SiF4/SiH4/N2O discharge mixtures, decomposing in a separate glow discharge the SiF4 gas just before being fed into the reaction chamber. The deposition rate for these oxides can be higher than 500 Å/min. According to infrared transmittance measurements, the effect of the SiF4 predecomposition is to reduce the amount of hydrogen in the silicon dioxide films. Ellipsometric and chemical etch rate measurements show that films prepared by this approach have better structural properties than those deposited without predecomposing the SiF4 gas. These results suggest that, the silicon–fluorine radicals generated by the predecomposition of the SiF4 gas, change the deposition chemistry in such a way that hinders the incorporation of O–H groups in the films.
Collimated magnetron sputter deposition with grazing angle ion bombardment
Authors: Rossnagel S. M. , Sward R.
Published: July 2002

Collimated magnetron sputter deposition with concurrent grazing angle ion bombardment has been developed as a technique for enhancing the ability to deposit films into trenches and vias. The collimated sputtering technique uses a conventional magnetron cathode operating at low pressure (mTorr) and a physical collimator or directional filter mounted between the cathode/discharge plasma and the sample position. The collimator serves to limit the directionality of the transmitted, sputtered atoms to near-normal incidence. A broad-beam Kaufman-type ion source is mounted on the sample side of the collimator such that the ion beam impacts the sample surface at grazing (5°–15°) incidence. This serves to resputter the depositing film selectively from the topmost regions of the sample surface, while lower areas, such as trenches and vias, are geometrically shielded.
Spatially averaged (global) model of time modulated high density argon plasmas
Authors: Ashida Sumio , Lee C. , Lieberman M. A.
Published: July 2002

The behavior of argon plasmas driven by time modulated power in ‘‘high density’’ plasma reactors is investigated using a global model. The time evolution of the electron temperature and the plasma density is calculated by solving the particle and energy balance equations. In the first stage of power application during the ‘‘on’’ time, the electron temperature rapidly increases above the steady state value. In this region, charged particles accumulate in the plasma due to the relatively higher power applied than for the continuous wave (cw) case. In the first stage of the ‘‘off’’ time, the electron temperature drops quickly, yielding a smaller particle loss (Bohm) velocity. These effects give rise to higher time-average plasma densities than for the cw plasma driven by the same average power. The highest average plasma density obtained was more than twice the density of the cw plasma for a duty ratio of 25%. Even higher plasma densities were obtained for shorter duty ratios. The possibility of controlling chemical reactions in the plasma by changing the modulation period is also shown.