bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust Stability and H∞ Control of Discrete-Time Jump Linear Systems With Time-Delay: An LMI Approach
Authors: Boukas E. K. , Liu Z. K.
Published: June 2003

This paper considers the class of discrete-time jump linear systems with time-delay and polytopic uncertain parameters. The problems of delay-independent robust stability, stabilization and H∞ control are cast into the framework of linear matrix inequality (LMI) and thus solved by LMI Toolbox of Matlab. By extending the system state, the system with time-delay is converted into a higher dimension Markov jump system without time-delay, and thus can be handled as a standard jump linear system with uncertain parameters. Numerical examples are provided to show the usefulness of the theoretical results.
Performance of Positive Displacement Motor (PDM) Operating On Air
Authors: Samuel G. Robello , Miska Stefan
Published: June 2003

Recent increase in application of horizontal wells and in particular underbalanced drilling, has triggered the necessity of a powerful pneumatic downhole motor. To enhance the technology and make the system effective, a mathematical model is required to identify the opportunities for the modification of power section design. It is well known that the performance of positive displacement motor operating on compressible fluid drops down drastically as compared to the operation under incompressible fluids. The frequent motor replacement during the operation incrementally increases the operating cost despite deriving potential benefits from underbalanced drilling.
Friction Factor Directly From Roughness Measurements
Authors: Sletfjerding Elling , Gudmundsson Jon Steinar
Published: June 2003

Pressure drop experiments on natural gas flow in 150 mm pipes at 80 to 120 bar pressure and high Reynolds number were carried out for pipes smooth to rough surfaces. The roughness was measured with an accurate stylus instrument and analyzed using fractal methods. Using a similar approach to that of Nikuradse the measured friction factor was related to the measured roughness values. Taking the value of the relative roughness and dividing it by the slope of the power spectrum of the measured roughness, a greatly improved fit with the measured friction factor was obtained. Indeed, a new friction factor correlation was obtained, but now formulated in terms of direct measurement of roughness.
Studies of Wavy Stratified and Stratified/Atomization Gas-Liquid Flow
Authors: Vlachos N. A.
Published: June 2003

Studies of wavy stratified and stratified/atomization two-phase flow in horizontal pipes are outlined. Notable features of this flow regime include the appearance of disturbance waves, the atomization onset and the drastic change of the gas/liquid interface profile from flat to “concave.” Liquid-to-wall shear stress tends to decrease circumferentially. A computational procedure for predicting main flow characteristics, which takes into account the above results in its design relations, is first assessed with detailed experimental data and is then combined with a CFD code, aiming at enhancing the predictive capability.
Internal Entropy Generation Limits for Direct Sensible Thermal Storage
Authors: Homan K. O.
Published: June 2003

This paper presents results for the entropy generated internally during the charging and discharging processes of a direct, sensible thermal energy store. The two processes correspond to the inflow of either a low or high temperature liquid stream into an enclosure initially filled with a uniformly high or low temperature liquid, respectively. The level of internal entropy generation due to thermal mixing between the inflow and the initial liquid volume corresponds to losses in the usable fraction of the stored volume and therefore decreased efficiency. Empirically, the observed behavior of direct sensible storage devices spans the range of nearly mixed to highly stratified. In the present work, analytical models for the fully-mixed and ideally-stratified limits are used to bound these behaviors and to analytically determine the corresponding entropy generation levels. The ratio of total entropy generation for the ideally-stratified limit relative to that of the fully-mixed limit is shown to vary as 8/πPe. The limiting behaviors therefore define a continuum of entropy generation levels separated by up to several orders of magnitude for typical Peclet numbers. A published numerical model which accounts for aspects of the observed thermal mixing is then examined in relation to these limits. The model predicts entropy generation levels midway between the limiting behaviors which suggests significant potential for improvements in the efficiency of direct sensible storage devices.
Emission properties of carbon nanotubes grown on various catalytic layers coated glass using plasma-enhanced chemical-vapor deposition with CO gas
Authors: Han Jae-Hee , Choi Sun Hong , Lee Tae Young , Yoo Ji-Beom , Park Chong-Yun , Jung T. W. , Kim H. J. , Park Y. J. , Han I. T. , Heo J. N. , Lee J. H. , Yu SeGi , Yi W. K. , Park G. S. , Lee N. S. , Kim J. M.
Published: June 2003

Using plasma-enhanced chemical-vapor deposition with a gas mixture of CO and NH3, carbon nanotubes (CNTs) were vertically grown on a glass substrate with various catalyst metals and buffer layers. The effects of catalyst metals and buffer layers on the growth and emission characteristics of CNTs have been investigated. The difference in the field-emission characteristics between CNTs with various catalyst metals and buffer layers was mainly attributed to the crystallinity of CNTs, i.e., sp2-binding states of CNTs. These states could be the most effective electron-emission sites.
Electrical and plasma property measurements of a deep reactive ion etching Bosch process
Authors: Abraham I. C. , Woodworth J. R. , Riley M. E. , Miller P. A. , Shul R. J. , Willison C. G.
Published: June 2003

We measured electrical and plasma properties of a deep reactive ion etching Bosch process (Ar/SF6/C4F8) used for micromachining bulk silicon. The plasma-potential oscillations were measured by a glass-enclosed capacitive probe immersed in the plasma. We used rf-potential and current sensors installed at the output of the chuck’s matching network and a calibrated equivalent circuit model to compute the chuck potential wave form. The plasma density and electron temperature were measured using a floating Langmuir double probe. Time-resolved measurements were made throughout the etch and deposition cycles of the Bosch process. Plasma densities in the reactor were quite nonuniform, with plasma densities close to the wafer chuck being more than a factor of 4 lower than densities in the center of the “bulk plasma” formed by the induction coil. Estimates of the ion energy distribution were obtained from a validated numerical model that employed the experimental data. For standard process conditions during the main etch part of the cycle, the chuck potential oscillations were in excess of 100 Vpp, but, because of the low plasma density near the wafer (>2×1010 cm−3) and potential averaging across the resulting large sheath width (600 μm), the width of the calculated argon ion energy distribution (IED) was only 25 eV, for a double peaked IED centered about 80 eV. The influence of rf-bias, plasma density, and ion mass on the IEDs were also investigated.
Interface analysis of atomic layer deposited-TiN gate electrodes on ultrathin SiO2 layers
Authors: Sell Bernhard , Sänger Annette , Krautschneider Wolfgang
Published: June 2003

As new gate materials become increasingly interesting in conjunction with tunnel oxides, new deposition techniques have to be developed that deposit thin metal layers without degrading the gate dielectric. Recently, atomic layer deposition has been identified as a suitable method to deposit refractory metal alloys with well-defined properties. For the first time, a recently developed automated characterization of capacitance–voltage (C–V) curves is employed to identify challenges during the initiation of a metal atomic layer deposition process. While some problems were eliminated by adapting the deposition process, others will require further process or tool modifications to reduce the nonuniformities observed within each wafer. The temperature dependence of the C–V curves indicates an unintended titanium-rich layer at the interface, which disappears after annealing above 800 °C. A further development of the surface pretreatment and subsequent deposition will be necessary to avoid this phenomenon. In this article, a very sensitive procedure to analyze the initiation of a metal atomic layer deposition process is presented.
Real-time, in situ film thickness metrology in a 10 Torr W chemical vapor deposition process using an acoustic sensor
Authors: Henn-Lecordier L. , Kidder J. N. , Rubloff G. W. , Gogol C. A. , Wajid A.
Published: June 2003

Process gases were sampled from the outlet of a tungsten chemical vapor deposition (CVD) reactor into an Inficon Composer™ acoustic sensor for in situ chemical gas sensing and real-time film thickness metrology. Processes were carried out on an Ulvac W CVD cluster tool at 10 Torr from 340 to 400 °C using a H2/WF6 gas mixture. Sampled gases were compressed through a diaphragm pump up to 100 Torr as required for accurate measurements in the acoustic cell. The high depletion of the heavy WF6 precursor (up to 30%) generated a significant variation of the average gas molecular weight and consequently of the mass-dependent resonant frequency measured by the acoustic sensor. The monitored signal was integrated over the process time, and the integrated area was correlated to the deposited W film thickness determined by ex situ measurements. The average error on this in-tool and real-time metrology was less than 1% over 30 wafers processed, either under fixed process conditions or while varying key process variables such as deposition time or temperature. A dynamic physically based simulator was also developed to validate the system response under different process conditions and demonstrate the fundamental understanding of this method. The metrology achieved represents a significant improvement over previously published data [L. Henn-Lecordier et al., J. Vac. Sci. Technol. A 19, 621 (2001)] obtained on the same system but in the sub-Torr process pressure regime, where low depletion rates (around 3%) had limited the metrology to 7% error. With an error less than 1%, this in situ chemical sensing approach could be efficiently exploited for real-time course correction, e.g., using end-point film thickness control.
Integrally gated carbon nanotube field emission cathodes produced by standard microfabrication techniques
Authors: Guillorn M. A. , Hale M. D. , Merkulov V. I. , Simpson M. L. , Eres G. Y. , Cui H. , Puretzky A. A. , Geohegan D. B.
Published: June 2003

The fabrication of carbon nanotube (CNT)-based field-emission devices has recently been an area of intense investigation. Here, we report a simple process for the fabrication of integrally gated CNT field-emission cathodes that uses standard microfabrication techniques. The operation of 3×3 field-emitter arrays produced using this process was investigated and found to behave in a manner consistent with the Fowler–Nordheim model of field emission.
Electrical properties of aluminum oxide films deposited on indium-tin-oxide glasses
Authors: Lee Jiyoul , Kim S. S. , Im Seongil
Published: June 2003

We report on the electrical properties of amorphous aluminum oxide films which are the potential gate dielectric material of organic thin-film transistors. The oxide films were deposited on indium-tin-oxide glasses using rf magnetron sputtering at room temperature under various Ar/O2 ambient of 6:1, 10:1, and Ar only. As measured by Rutherford backscattering spectrometry, the stoichiometry (x:y) of the AlxOy oxide films approaches up to 2:3.5 when the gas ratio increases. The highest breakdown electric field (∼3 MV/cm) was obtained from the samples deposited at the Ar only condition. According to capacitance–voltage measurements, all of our aluminum oxide films show ∼7 as their dielectric constant, k.
Focused ion beam induced surface amorphization and sputter processes
Authors: Basnar B. , Lugstein A. , Wanzenboeck H. , Langfischer H. , Bertagnolli E. , Gornik E.
Published: June 2003

Focused ion beam techniques are among the most important tools for the nanostructuring of surfaces. As the physical phenomena during milling are not fully understood yet, we have applied the phase imaging capabilities of tapping mode atomic force microscopy to the investigation of surface amorphization, sputtering, and redeposition caused by focused ion beam irradiation. We have performed single spot as well as large area (20×20 μm2) irradiation of silicon (100) wafers. We describe the localized formation of amorphous and electrostatically charged domains, which do not correlate to topographic features.
Effect of laser annealing on delta-doped boron for super-steep-retrograded well formation using selective Si epitaxy
Authors: Lee Jung-Ho , Lee Jeong-Youb , Weon Dae-Hee , Hahn Seung-Ho , Lee Seok-Kiu , Ichikawa Masakazu
Published: June 2003

The effect of laser thermal annealing (LTA) on δ-doped B has been investigated for the applications of super-steep-retrograde (SSR) 70 nm n-type metal–oxide–semiconductor field-effect transistors using undoped selective silicon epitaxy. Shallow (⩽50 Å) melting by LTA was found to suppress the B loss, causing an anomalous lowering and fluctuation of threshold voltage (Vt), upon epitaxial channel growth and rapid thermal annealing (RTA). Under the laser fluence of 0.42 J/cm2, the B profile was also observed to freeze without further diffusion upon RTA at 900 °C for 20 s. Significant B loss observed in conventional δ-doped SSR devices stemmed from the hydrogen ambient at 800 °C required for selective silicon epitaxy as well as the rapid B outdiffusion behavior. The laser-induced surface melting decreased the outdiffusion rate by increasing the portion of substitutional B, and also led to a surface roughening which made the B loss from the silicon surface difficult. As a result of LTA, much lower Vt fluctuation with reasonable Vt was obtained along with improved short channel characteristics.
Using electron cyclotron resonance sputtering in the deposition of ultrathin Al2O3 gate dielectrics
Authors: Jin Yoshito , Saito Kunio , Shimada Masaru , Ono Toshiro
Published: June 2003

The gate-dielectric characteristics of an ultrathin Al2O3 film deposited by electron cyclotron resonance sputtering are investigated. The sputtering process is classified as operating in either of two deposition modes: a metal mode and an oxide mode. Characteristics of the deposited films, such as their surface morphology, uniformity of thickness, and degrees of interlayer-oxide formation, are presented for both modes. The electrical characteristics of metal-mode Al2O3 films after annealing in a high vacuum (around 10−4 Pa) are looked at in detail. The metal-mode condition and high-vacuum annealing prevents the formation of interlayer oxide and reduces the flat-band voltage (VFB) shift but also produces a rather large capacitance–voltage (C–V) hysteresis loop. A small equivalent oxide thickness of 1 nm, low values for leakage current of around 2×10−3 A/cm2, and a fixed negative-charge density of 7×1010 cm−2 are demonstrated for the metal-mode films. The large C–V hysteresis loop is reducible by oxidation.
All solid-state rechargeable thin-film microsupercapacitor fabricated with tungsten cosputtered ruthenium oxide electrodes
Authors: Kim Han-Ki , Cho Suk-Ho , Ok Young-Woo , Seong Tae-Yeon , Yoon Young Soo
Published: June 2003

We investigate an all solid-state thin-film microsupercapacitor (TFSC) fabricated with tungsten cosputtered ruthenium oxide electrodes (W-RuO2) and LiPON electrolyte. It is shown that the room-temperature charge–discharge behavior of the TFSC is similar to that of a bulk-type supercapacitor. It is also shown that the W-RuO2-based TFSC exhibits a higher discharge specific capacitance and more stable cyclibility, compared with those of the RuO2-based TFSC. Based on the pseudocapacitance of the oxide electrodes, the cycling behavior of the TFSCs and tungsten cosputtering effect on the electrochemical properties of TFSCs are described.
Chemical mechanical polishing defect reduction via a plasma etch in the 0.15 μm shallow trench isolation process
Authors: Chiu C. M. , Yen T. F. , Chiu K.-F.
Published: June 2003

The resultant surface microscratches due to chemical mechanical polishing (CMP) can cause device failure and reduce production yield in the shallow trench isolation (STI) process. By using a plasma etch process to replace the overpolish step of CMP planarization (CMP+plasma etch), we have reduced 10% of the total defect counts in the 0.15 μm STI process. The CMP microscratches have been effectively smoothened by the additional plasma etch process. The electrical properties of the devices made via the CMP and the CMP+plasma etch processes have been examined and compared. The off-state currents are similar. A higher breakdown voltage is found for the CMP+plasma etch process and can be interpreted by the local electrical-field concentration. Although the n+/p and p+/n junctions fabricated by the CMP+plasma etch processes exhibit slightly larger leakage currents for certain test patterns, due to plasma damage, the products still meet the inline production requirements, and show promising results for yield improvement.
Two-dimensional photonic crystals by focused-ion-beam etching of multilayer membranes
Authors: Wang K. , Filloux P. , Paraire N. , Roca i Cabarrocas P. , Bulkin P.
Published: June 2003

We present an approach for two-dimensional photonic crystal fabrication in prestructured multilayer membranes. We show that well-defined structures with submicronic periodicity can be created by focused-ion-beam etching through the membranes. A photonic band gap around 1.5 μm is observed by spectral measurements, in agreement with theoretical simulations. Further improvements are also proposed.
Photoluminescence and micro-Raman scattering in Mn-doped ZnS nanocrystalline semiconductors
Authors: Yang Richard D. , Tripathy S. , Tay Francis E. H. , Gan L. M. , Chua S. J.
Published: June 2003

Using photoluminescence and Raman scattering, we have studied the optical properties of Mn-doped ZnS nanocrystallites prepared by a microemulsion-hydrothermal method. The PL spectrum shows two distinct peaks in the blue-green region. The PL peak from the nanoparticles, in the region 400–480 nm (3.1–2.6 eV), shifts toward the lower energy with decreasing excitation intensity, which shows that the luminescence originates from the donor–acceptor pair recombination. Such self-activated luminescence could involve the Zn vacancies and Mn acceptors. Micro-Raman scattering measurements on these nanostructured ZnS:Mn crystallites show a low-frequency wing at 315 cm−1 besides the characteristic first-order longitudinal optical phonon at 349 cm−1. The transverse optical phonon from these nanocrystallites at 269 cm−1 along with a much weaker vibrational mode near 220 cm−1 was also observed.
Simple magnetic focusing for an electron gun based on a microtip array
Authors: Barjon J. , Jalabert D. , Levy F.
Published: June 2003

In this article, we propose a compact 10–20 keV electron gun based on a simple magnetic focusing of a dense array of field-emissive microtips. The properties of this magnetic focusing system have been investigated with the view to providing a homogeneous electron beam on a target with a predefined cross section (10 μm×1 mm). The gun focusing performance has been estimated through an analytical calculation based on aberration optics. Because of the large aperture angle of the microtips, the system magnification is mainly due to spherical aberrations. Then, with an experimental setup immersed in a 0.046 T uniform magnetic field, an 80 μm×1 mm beam spot was obtained on a 5.5 kV-biased anode from a 10 μm×1 mm microtip array, located 15 mm from the anode. The 0.6 mA peak emitted current brought the power density to 4 kW/cm2, with a spot size larger than expected from the calculations. An adjustable magnetic field setup has made it possible to get a good understanding of the focusing mechanism. The limited focusing performance obtained in this experiment was attributed to the electric-field nonuniformity inside the vacuum chamber.
Comparison of two surface preparations used in the homoepitaxial growth of silicon films by plasma enhanced chemical vapor deposition
Authors: Reidy Sean , Varhue Walter J. , Lavoie Mark , Mongeon Stephen , Adams Edward
Published: June 2003

The effect of surface preparation on the growth of epitaxial Si films by plasma enhanced chemical vapor deposition was investigated. The surface preparations considered were an ex situ ozone scrub and an in situ Ar/H2-plasma clean. Both methods were found to be effective at removing carbon contamination from the substrate surface which is critical for epitaxial growth. The thin-film quality was determined by Rutherford backscatter spectrometry, high-resolution x-ray diffraction, and transmission electron microscopy. To gain insight into mechanisms controlling the in situ cleaning process, hydrogen was replaced by deuterium in the plasma clean prior to film growth. The film/substrate interface was then analyzed by secondary ion mass spectrometry. Surprisingly, the plasma clean had little influence on the interfacial hydrogen concentration established by the previous hydrofluoric acid dip. It was found that hydrogen remains bound to C and O contaminants at the interface caused by the initial growth surface, and that neither an ex situ process containing an ozone scrub nor an in situ process containing a hydrogen-plasma clean could completely remove them.
Selective epitaxial growth for plugs of high-density devices
Authors: Cheong Woo-Seok , Lee Seok-Kiu , Roh Jae-Sung
Published: June 2003

Silicon-plugging process using selective epitaxial growth by low-pressure chemical vapor deposition is developed for 0.12 μm tech dynamic random access memory application, showing remarkable performance in electronic properties as well as in building structures. Process problems such as selectivity, local nonuniformity of growth rate, and facet generation can be well solved with the help of chemical vapor deposition thermodynamics and growth mechanism based on gas phase reactions. It is also proved that the thermal budget of the selective epitaxial growth (SEG) plug process has no significant influence on phosphorus outdiffusion from the ILD borophosphosilicate glass barrier to cell junction. Low contact resistance of the SEG plug, reaching about one third of that of conventional silicon plug, is attributed to the epitaxial interface between the plug and cell junction. Other good electronic properties such as Idsat and junction leakage strongly suggest that the cell plug using selective epitaxial growth should be a breakthrough in future semiconductor manufacturing.
Depletion- and enhancement-mode In0.49Ga0.51P/InGaAs/AlGaAs high-electron-mobility transistors with high-breakdown voltage
Authors: Li Yih-Juan , Hsu Wei-Chou , Chen Yen-Wei , Shieh Hir-Ming
Published: June 2003

A high-breakdown δ-doped In0.49Ga0.51P/InGaAs/AlGaAs high-electron-mobility transistor (HEMT) grown by low-pressure metalorganic chemical vapor deposition has been fabricated and demonstrated successfully. By using a wet etching gate process, we obtained depletion- and enhancement-mode HEMTs. The fabricated devices (1.5×125 μm2) show that the measured maximum drain saturation current density and extrinsic transconductance are 215 mA/mm and 82 mS/mm for depletion-mode and are 100 mA/mm and 75 mS/mm for enhancement-mode devices, respectively. The gate-to-drain breakdown voltage for both types is over 40 V. The high-breakdown voltage is attributed to the use of an In0.49Ga0.51P Schottky layer, δ-doping, and GaAs subspacer layer.
Fabrication of multiwalled carbon nanotube bridges by poly-methylmethacrylate suspended dispersion
Authors: Lee S.-B. , Teo K. B. K. , Amaratunga G. A. J. , Milne W. I. , Chhowalla M. , Hasko D. G. , Ahmed H.
Published: June 2003

We report on the fabrication of multiwalled carbon nanotube (MWCNT) bridges using poly-methylmethacrylate (PMMA) suspended dispersion. This method makes it possible to suspend nanotubes between metal electrodes, without any chemical etching of the substrate, and to remove unwanted nanotubes from the substrate. Using a spacer layer of PMMA with a known thickness, it is also possible to control the suspended height of the MWCNT bridges. The electrical measurement results on suspended MWCNT bridges reveals that the room temperature resistance ranges from under a kΩ to a few MΩ, with the majority around 2–4 kΩ. It was shown that a plasma-enhanced chemical vapor deposition grown MWCNT with a diameter ∼55 nm can sustain current densities of ∼108 A/cm2, which will make them suitable for applications as integrated field emission cathodes.
Quantification of line-edge roughness of photoresists. II. Scaling and fractal analysis and the best roughness descriptors
Authors: Constantoudis V. , Patsis G. P. , Tserepi A. , Gogolides E.
Published: June 2003

A search for the best and most complete description of line-edge roughness (LER) is presented. The root mean square (rms) value of the edge (sigma value) does not provide a complete characterization of LER since it cannot give information about its spatial complexity. In order to get this missing information, we analyze the detected line edges as found from scanning electron microscope (SEM) image analysis [see Paper I: G. P. Patsis et al., J. Vac. Sci. Technol. B 21, 1008 (2003)] using scaling and fractal concepts. It is shown that the majority of analyzed experimental edges exhibit a self-affine character and thus the suggested parameters for the description of their roughness should be: (1) the sigma value, (2) the correlation length ξ, and (3) the roughness exponent α. The dependencies of ξ and α on various image recording and analysis parameters (magnification, resolution, threshold value, etc.) are thoroughly examined as well as their implications on the calculation of sigma when it is carried out by averaging over the sigmas of a number of segments of the edge. In particular, ξ is shown to be connected to the minimum segment size for which the average sigma becomes independent of the segment size, whereas α seems to be related to the relative contribution of high frequency fluctuations to LER.
Quantification of line-edge roughness of photoresists. I. A comparison between off-line and on-line analysis of top-down scanning electron microscopy images
Authors: Patsis G. P. , Constantoudis V. , Tserepi A. , Gogolides E. , Grozev G.
Published: June 2003

An off-line image analysis algorithm and software is developed for the calculation of line-edge roughness (LER) of resist lines, and is successfully compared with the on-line LER measurements. The effect of several image-processing parameters affecting the fidelity of the off-line LER measurement is examined. The parameters studied include the scanning electron microscopy magnification, the image pixel size dimension, the Gaussian noise-smoothing filter parameters, and the line-edge determination algorithm. The issues of adequate statistics and appropriate sampling frequency are also investigated. The advantages of off-line LER quantification and recommendations for the on-line measurement are discussed. Having introduced a robust algorithm for edge-detection in Paper I, Paper II [V. Constantoudis et al., J. Vac. Sci. Technol. B 21, 1019 (2003)] of this series introduces the appropriate parameters to fully quantify LER.
Nanocomposite coatings within the system Ti–B–N deposited by plasma assisted chemical vapor deposition
Authors: Stoiber M. , Mitterer C. , Schoeberl T. , Badisch E. , Fontalvo G. , Kullmer R.
Published: June 2003

Ti–B–N coatings have been deposited by plasma assisted chemical vapor deposition (PACVD) onto tool steels and were evaluated with respect to their structure, mechanical and tribological properties. The boron content of the coatings investigated was varied from 7 to 52 at. %. All coatings were compared to single-phase TiN and TiB2 films. For increasing boron content, a nanoscaled dual-phase structure consisting of different amounts of TiN and TiB2 phases was found. Likewise, the hardness increased from 20 to a maximum of 36 GPa. VDI indentation as well as surface fatigue testing, where cyclic loads up to 80 kN are applied to the tool surface by cylindrical cemented carbide indenters, indicated excellent coating adhesion. Biaxial stresses were evaluated using a cantilever beam method. In ball-on-disk testing, the lowest friction coefficient of about 0.17–0.22 against a 100Cr6 ball was yielded for TiN coatings and for coatings with boron contents below 9 at. % B. Boron additions exceeding this limit resulted in increasing friction coefficients of up to 0.8. Abrasive wear rates determined using a microscale abrasion tester decreased continuously from 6.9×10−13 to 8.2×10−14 m2/N with increasing boron content from 7 to 52 at. %, respectively. The results obtained indicate that PACVD Ti–B–N coatings are an excellent choice for tribological applications under severe conditions like deep drawing or cold forming.
Atomic force microscopy and x-ray diffraction studies of aluminum-induced crystallization of amorphous silicon in Al/α-Si:H, α-Si:H/Al, and Al/α-Si:H/Al thin film structures
Authors: Kishore Ram , Shaik Arshad , Naseem H. A. , Brown W. D.
Published: June 2003

Amorphous silicon (α-Si:H) films were deposited on both Corning 7059 glass and single-crystalline, silicon (c-Si) substrates in combination with aluminum to create α-Si:H, Al/α-Si:H, α-Si:H/Al, and Al/α-Si:H/Al structures for a study of aluminum-induced crystallization (AIC) of α-Si:H. The α-Si:H was deposited by high-vacuum plasma-enhanced chemical vapor deposition. The structures were then annealed at temperatures between 200 and 500 °C using radiative heating. Optical microscopy was used to observe macro-scale changes in the surface of the films after annealing. The surface microroughness was investigated using atomic force microscopy. X-ray diffraction analysis was performed to study the crystallization changes of the α-Si:H induced by the presence of the Al. The surface roughness, as well as the morphology of these structures exhibit significant changes with annealing. The results show that the smoothest polycrystalline silicon films are obtained for the Al/α-Si:H structure.
High aspect ratio etching of atomic force microscope-patterned nitrided silicon
Authors: Harfenist Steven A. , Yazdanpanah Mehdi M. , Cohn Robert W.
Published: June 2003

Silicon that is nitrided in a pure nitrogen plasma is patterned with voltage applied by an atomic force microscope (AFM). Wet chemical etching into AFM-patterned (110) silicon produced vertical trenches as narrow as 91 nm (for one 757 nm deep trench) and with aspect ratios as large as 8.9:1 (for a 95 nm by 849 nm trench). Compared to the ridge patterns resulting from AFM oxidation and wet etching of hydrogen-passivated silicon, a substantially higher applied voltage is required to pattern nitrided silicon.
Reduction of grain-boundary potential barrier height in polycrystalline silicon with hot H2O-vapor annealing probed using point-contact devices
Authors: Kamiya Toshio , Durrani Zahid A. K. , Ahmed Haroon , Sameshima Toshiyuki , Furuta Yoshikazu , Mizuta Hiroshi , Lloyd Neil
Published: June 2003

The effects of hot H2O-vapor annealing were investigated on local carrier transport properties over a few grain boundaries in polycrystalline silicon. It shows that hot H2O-vapor annealing effectively reduces grain-boundary dangling bonds and the potential barrier height. In addition, it narrows the distribution of the barrier height value significantly. These effects are thought to originate from oxidation in the vicinity of the film surface, and from hydrogenation in the deeper region. Our results suggest that H2O annealing can improve the carrier transport properties by opening up shorter percolation paths and by increasing the effective carrier mobility and density.
Enhanced infrared detection characteristics of VOx films prepared using alternating V2O5 and V layers
Authors: Kang Ho Kwan , Han Yong Hee , Shin Hyun Jun , Moon Sung , Kim To Hoon
Published: June 2003

Multilayer VOx films are reported to improve the infrared (IR) detecting characteristics for application as an IR active layer in a microbolometer. Multilayer VOx films formed from the V2O5/V/V2O5 thin film structure showed some advantages in electrical property control and more effective formation of typically unstable vanadium oxide phases. These phases are difficult to achieve by single-layer VOx film fabrication with conventional reactive sputtering. Multilayer VOx films were fabricated by low temperature oxygen annealing at 300 °C after the alternating deposition of stable V and V2O5 layer using rf sputtering. The electrical measurement and microstructural analysis of annealed films were performed to evaluate the advantage of multilayer VOx film fabrication. Owing to the well-controlled mixed phase formation, including V2O3, VO2, and V2O5 in the annealed V2O5/V/V2O5 multilayer film, the temperature coefficient of resistance value and resistivity of the new multilayer VOx film could be increased up to −2.49%/K and reduced less than 0.1 Ω cm, respectively. A single microbolometer pixel of 50×50 μm2, applying this multilayer VOx film, showed total microbolometer resistance of below 20 kΩ to achieve low noise characteristics.
Correlation between structural and transport properties of silicon thin films deposited at various substrate temperatures
Authors: Roy D. , Das Chandan , Longeaud C. , Houzé F. , Ray S.
Published: June 2003

Intrinsic silicon thin films have been deposited with high and low dilution of hydrogen in silane by radio frequency powered plasma enhanced chemical vapor deposition method at varying substrate temperatures (200 °C⩽Ts⩽370 °C). Structural and transport properties of these films have been studied. With high hydrogen dilution, all the films are microcrystalline over the range of Ts investigated. The grain size (∼300 Å) does not change with Ts but the diffusion length of minority carriers decreases from 200 to 90 nm. With low hydrogen dilution a clear transition from amorphous to microcrystalline phase occurs with increase in Ts. The grain size increases from 88 to 350 Å for the microcrystalline films along with an increase in diffusion length from 90 to 135 nm. The correlation between the structural and transport properties are discussed in terms of hydrogen incorporation in the films. We conclude that low Ts with high hydrogen dilution and high Ts with low hydrogen dilution are two possible combinations for deposition of device quality microcrystalline films.
Individual free-standing carbon nanofibers addressable on the 50 nm scale
Authors: Moser J. , Panepucci R. , Huang Z. P. , Li W. Z. , Ren Z. F. , Usheva A. , Naughton M. J.
Published: June 2003

We report on the fabrication of arrays of free-standing carbon nanofibers (CNFs) individually addressable on the 50 nm scale. The template for CNF growth consists of a set of tungsten leads patterned with a catalyst dot at the tip of each terminal. The fabrication process involves electron-beam lithography, projection photolithography, reactive ion etching, and dc plasma-enhanced chemical vapor deposition. Discharge power is found to drastically influence the morphology of CNFs grown off single catalyst dots.
Exploring metal vapor vacuum arc implanted copper to catalyze electroless-plated copper film on a TaN/FSG/Si assembly
Authors: Chen Uei-Shin , Lin Jian-Hong , Hsieh Wei-Jen , Shih Pai-Shen , Weng Ko-Wei , Wang Da-Yung , Chang Yee-Shyi , Shih Han C.
Published: June 2003

This work attempted to implant a Cu catalyst into a TaN (500 Å)/FSG (1200 Å)/Si assembly using a metal vapor vacuum arc ion implanter. The range of the copper dose was between 5.0×1015 and 1.0×1017 cm−2 and the accelerating voltage ranged from 30 to 50 kV. Both blanked and patterned specimens were subsequently deposited with an electroless-plated Cu film. The specimens as a whole were characterized by secondary ion mass spectrometer (SIMS), x-ray diffraction (XRD), and field emission scanning electron microscope (FESEM). The sheet resistance was measured by a four-point probe. A noticed relationship between SIMS depth profiles and the ion energy was established. The XRD spectra also showed that electroless-plated copper film possessed a strongly characteristic peak of Cu(111) preferred orientation. An excellent gap filling in a 0.2-μm-width (AR 7:1) trench/via was observed by FESEM. The sheet electric resistivity of the specimens was decreased to 1.93 μΩ cm after annealing at 500 °C for 1.5 h under an atmosphere of 10%H2–90%N2.
Real-time observation of electromigration-induced stress changes with imaging x-ray topography
Authors: Solak H. H. , David C. , Gobrecht J. , Drakopoulos M.
Published: June 2003

We have observed the evolution of stress in Al interconnect lines during the electromigration process using x-ray topography in a new imaging configuration. Monochromatic x rays from a synchrotron source were reflected in a symmetric geometry by the Si substrate of the interconnect structure. We used a Fresnel zone plate in an off-axis imaging geometry to obtain magnified images of the sample. The results show the establishment of a constant stress gradient in the steady state where the electromigration damage is halted as well as time-dependent behavior of stress leading to that state. The imaging x-ray topography technique offers a number of advantages including better spatial resolution potential by eliminating the blur that occurs in conventional topography due to the finite distance between the sample and the detector.
Improvement on electron field emission properties of nanocrystalline diamond films by co-doping of boron and nitrogen
Authors: Lin I-Nan , Hsu Tung , Lin Gia-Ming , Chou Yi-Ping , Chen Tong T. , Cheng Hsin-Fung
Published: June 2003

Effect of boron/nitrogen co-doping on the electron field emission characteristics of nanocrystalline diamond films was examined. The diamond grains, which are of faceted geometry and about 0.5–1 μm in size, vary insignificantly due to incorporation of boron and nitrogen species. Raman spectroscopies also do not change with the doping concentration. However, B/N codoping markedly improves the electron field emission properties of the diamond films. The electron field emission current density increases from (Je)B1=20 μA/cm2 for diamond films containing 1 sccm B(OCH3)7, to (Je)B3=250 μA/cm2 for those containing 3 sccm B(OCH3)3. The electron field emission capacity further increases to (Je)B3N3=1750 μA/cm2 for diamond films co-doped with 3 sccm B(OCH3)3 and 3 sccm (NH3)2CO. Atomic force microscopies reveal that the electronic structure of diamonds was markedly modified due to boron/nitrogen co-doping.
Improved room-temperature continuous wave GaAs/AlGaAs and InGaAs/GaAs/AlGaAs lasers fabricated on Si substrates via relaxed graded GexSi1−x buffer layers
Authors: Groenert Michael E. , Pitera Arthur J. , Ram Rajeev J. , Fitzgerald Eugene A.
Published: June 2003

Improved GaAs/AlGaAs quantum well lasers were fabricated with longer lifetimes, higher efficiencies, and lower threshold current densities than previously reported devices on Ge/GeSi relaxed graded buffers on Si substrates. Uncoated broad-area lasers operated continuously at 858 nm with a differential quantum efficiency of 0.40 and a threshold current density of 269 A/cm2. Similar devices fabricated on GaAs substrates demonstrated nearly identical performance. Operating lifetimes on Si substrates were nearly 4 h, a 1 order of magnitude improvement over previous devices. In addition, strained InGaAs quantum well lasers have been operated continuously at room temperature on Ge/GeSi/Si substrates with a differential quantum efficiency of 0.26 and a threshold current density of 700 A/cm2. Electroluminescence analyses of the failure behavior of both types of devices have suggested that recombination-enhanced defect reactions are limiting laser lifetime on Si substrates.
Measurement of V/III ratio using threshold photoemission
Authors: Zinck J. J. , Owen J. H. G. , Barvosa-Carter W.
Published: June 2003

A method for measuring the V/III ratio for epitaxial growth using threshold photoemission is demonstrated. The variation in photoyield observed during reconstruction changes of InAs (001), attributed to the variation of As dimer concentration on the surface, can be used to determine the As incorporation rate, and hence the V/III ratio in situ, in a manner analogous to As-limited reflection high energy electron diffraction oscillation measurements. Although As-limited photoyield oscillations are observed and reported here, the photoyield method for determining the V/III ratio is not dependent on the measurement of oscillations. The photoyield measurement approach is still applicable at high temperatures where step flow growth competes with island nucleation and oscillations are difficult to resolve.
Height measurement of dsDNA and antibodies adsorbed on solid substrates in air by vibrating mode scanning polarization force microscopy
Authors: Li Xiao-jun , Sun Jie-lin , Zhou Xing-fei , Li Gang , He Pin-gang , Fang Yu-zi , Li Min-qian , Hu Jun
Published: June 2003

A method of height measurement based on vibrating mode scanning polarization force microscopy is developed and applied to soft molecules such as dsDNA and antibodies. In the experiment, a bias voltage is applied to a conductive atomic force microscopy (AFM) tip to maintain it farther from the surface during imaging in vibrating mode. By changing amplitude setpoint (Asp) the tip can be lowered from the top of a molecule to the substrate, and the displacement of the tip in the z direction (DZ) approximates the true height of this molecule. This method is first applied to rigid colloidal gold particles and then to dsDNA and antibodies. The measured heights of gold particles are consistent with those in normal tapping mode AFM (TM-AFM). However, the measured heights of dsDNA molecules and antibodies CA125 are much larger than the results in TM-AFM. We deduce that tip pressure might have caused large deformation on soft biomolecules when imaging is performed in TM-AFM.
Coating protecting layers in alternating current-plasma display panels
Authors: Lee W. T. , Im S. J. , Lee D. Y. , Yu SeGi , Kim J. M. , Han J. G. , Lee J. W. , Choi E. H.
Published: June 2003

Two protecting layers, a MgF2/MgO multilayer coated MgO layer and a LaF3 layer coated MgO layer, were studied in order to overcome the weakness of the conventional MgO protecting layer for use in color alternating current (ac) plasma display panels (PDPs). The material characteristics of these protecting layers were examined by carefully changing the growing conditions. The display characteristics were also examined by manufacturing real PDPs using these protecting layers. These two protecting layers had higher secondary electron-emission yields than conventional MgO. It was demonstrated that these two methods were effective for lowering the firing and sustaining voltage of PDPs and also for enhancing the brightness of the panel.
Effects of Ti insertion between Cu and TiN layers on reliability in Cu/Ti/TiN/Ti layered damascene interconnects
Authors: Abe Kazuhide , Onoda Hiroshi
Published: June 2003

We investigated the effects of Ti insertion between Cu and TiN layers on electromigration (EM) in Cu/Ti/TiN/Ti layered damascene interconnects. The Cu damascene interconnects with Ti insertion show an EM lifetime of up to 100 times longer than those without Ti insertion, depending on the inserted Ti thickness. The lifetime improves as Ti thickness increases from 10 to 20 nm. Ti insertion increased the sheet resistance of the layered film after annealing and enhanced the adhesion of Cu to underlayer TiN. The resistance change was mainly caused by formation of Cu–Ti reaction products resulting in reduced cross-sectional area in the Cu film, and was also caused by Ti incorporation into the Cu film. Ti insertion, however, does not have any effect on Cu film microstructure such as median grain size, standard deviation of grain size distribution, and texture. During EM testing, the resistance in Cu interconnects with Ti insertion initially decreases, then rises gradually, and finally increases rapidly until failure occurs. This behavior is probably caused by Ti redistribution in Cu during the EM testing. EM lifetime consists mainly of the time when the interconnect resistance is lower than the initial resistance, that is, the time before void growth occurs (incubation time). Improved Cu adhesion to underlayer TiN is an important factor because the void growth rate of Cu interconnects during EM testing is considerably decreased by Ti insertion. The void growth rate, however, does not depend on Ti thickness and Ti surface treatment before Cu deposition. As a result, EM lifetime is mainly governed by the incubation time, and the void growth rate is determined by Cu EM through the Cu/barrier interface path.
Comparative study of MeV C+ and C2+ ion implantation in GaAs(100): Surface roughness and evaluation of lattice strain
Authors: Kuri G. , Materlik G. , Hagen V. , Wiesendanger R.
Published: June 2003

GaAs(100) single crystal substrates have been implanted with 1.00 MeV C+ and 2.00 MeV C2+ at various ion doses. The surface topography and roughness of the implanted surfaces are studied by atomic force microscopy and x-ray reflectometry. Above a threshold dose, production of surface defects is observed, which results in an overall increase of the rms roughness parameter. The enhanced rms roughnesses induced by monomer and by dimer ions at a given dose are comparable. The influence of C+ and C2+ irradiations on the change of lattice parameter in GaAs, and the effect of thermal annealing, are examined by high-resolution x-ray diffraction. For the as-implanted specimens, an increase of the lattice constant, caused by the accumulation of implantation-induced point defects, has been observed and quantified. Thermal treatment of the implantation damage stimulates an almost complete recovery of the primary defects, leaving the crystal practically free from any lattice strain. The electrical characteristics of the C+ and C2+ implantations are also briefly presented and discussed.
Sub-150 nm, high-aspect-ratio features using near-field phase-shifting contact lithography
Authors: Dang Hai , Tan Jackie Lim-Piu , Horn Mark W.
Published: June 2003

A simple technique, near-field phase shifting contact lithography, is described which can extend the resolution of contact lithography to less than 200 nm. Sub-150 nm, high-aspect-ratio features have been produced using chromeless phase-shifting masks, a Karl Suss MA-6 contact aligner and off-the-shelf SPR 510 photoresist. The technique is neither purely near field nor purely phase shifting considering subwavelength features have been patterned in resists whose thickness is twice the longest exposure wavelength. Conventional 5 in. chrome-on-quartz masks were reactive ion etched to generate precisely varied phase steps from 375 nm to 512 nm using standard CF4 etch chemistries and then stripped of chrome. These masks were then used to expose SPR 510 spun on bare silicon wafers to broadband and filtered UV irradiation. After development in an aqueous base developer, features were examined as a function of exposure wavelengths, shifter depth, resist thickness, resist type, exposure dose, and postexposure bake temperature and time. Features as small as 128 nm with aspect ratios of >5:1 have been printed with this technique with minimal sidewall roughness.