bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonconventional flash annealing on shallow indium implants in silicon
Authors: Gennaro S. , Giubertoni D. , Bersani M. , Foggiato J. , Yoo W. S. , Gwilliam R.
Published: February 2006

The diffusion behavior and the electrical characteristics of indium doped layers in silicon were studied. Indium was implanted in silicon at energies of 70 and 25 keV to doses of 5.8 and 3×1014, respectively. The implants were performed both in amorphous and crystalline silicon. The implants were submitted to a combination of thermal annealing, RTA, and flash annealing to regrow the implanted layers and activate the dopant. Four point probe sheet resistance measurements and Hall effect measurements were carried out to test the electrical properties of the implanted layers. The atomic concentration profiles were assessed using secondary ion mass spectrometry. A drastic increase in the dopant activation was observed following co-implanting with carbon. Moreover, the carbon presence inhibits the indium diffusion and segregation in damaged areas. The preamorphizing treatment affects the indium diffusion in two ways. For low thermal budget anneals the diffusion is suppressed, conversely the diffusion is enhanced under severe annealing conditions.
Extracting active dopant profile information from carrier illumination power curves
Authors: Dortu Fabian , Clarysse Trudo , Loo Roger , Vandervorst Wilfried
Published: February 2006

The carrier illumination (CI) method is an optical nondestructive technique primarily used today for the in-line monitoring of ultrashallow doping profiles in advanced complementary metal oxide semiconductor devices. A CI measurement is basically a differential probe laser reflectivity measurement providing (indirect) information on the underlying active dopant structure. As the signal depends on the doping density as well as the junction depth, no unique answer can be extracted from a single measurement. When analyzing power curves (i.e., the CI signal as a function of the power of the pump laser), it is shown that the shape of the power curves is (simultaneously) extremely sensitive to many different physical parameters, such as junction depth (angstrom), carrier peak density (10%), profile steepness (few nm∕decade), etc. In this work, we present a detailed interpretation and deconvolution method enabling the independent extraction of the peak carrier density and the junction depth for (unknown) chemical vapor deposition-grown box-like profiles (with 1–2nm∕decade steepness). The method is based on the exploitation of two characteristics of the power curve, namely its signal value at a particular (arbitrary) power and the power at which an inflection point (second derivative zero) occurs. The physical interpretation on this approach will be presented and is supported by extensive three-dimensional axisymmetric numerical simulations.
Application of molecular dynamics for low-energy ion implantation in crystalline silicon
Authors: Chan H. Y. , Srinivasan M. P. , Montgomery N. J. , Mulcahy C. P. A. , Biswas S. , Gossmann H.-J. L. , Harris M. , Nordlund K. , Benistant F. , Ng C. M. , Gui D , Chan L.
Published: February 2006

Molecular dynamics (MD) is set to replace Monte Carlo (MC) methods utilizing the binary collision approximation (BCA) in modeling dopant distributions after ion implantation in the low energy regime. Simultaneous nonbinary interactions come into play as the ion slows down; unlike BCA, MD automatically accounts for multiple collisions between ion and its neighboring atoms. In this work, the energy limit below which BCA fails is estimated from density functional theory (DFT) calculations for a wide range of dopants. Impurity profiles are generated using the MD code, MDRANGE. A database consisting of secondary ion mass spectrometry (SIMS) profiles covering a wide range of dopants (B, C, F, N, P, As, Ge, In, and Sb) over the energy regime of 0.5–10keV at critical channeling directions have been set up. The MD simulated profiles show good agreement with SIMS data, which have been obtained either with a quadrupole—or magnetic-sector—based mass spectrometer.
Single-wafer-processed trench-sidewall integration and its application in a micro resonant detector for vacuum monitoring
Authors: Li Xinxin , Xu Wei , Chen Ying , Luo Le , Gu Lei , Liu Min , Cheng Baoluo , Wang Yuelin
Published: February 2006

A trench-sidewall technology is developed for single-wafer-based integration of micro sensors and actuators with in-plane lateral configuration. Piezoresistive sensing and electrostatic actuating elements can be integrated together onto the deep-trench sidewalls of in-plane microelectromechanical structures by sidewall boron diffusion. Adjacent sidewall elements are electrically isolated by previously formed SiO2-refilled trenches. Electric transference from the sidewall to wafer surface is performed via the overlaps between the sidewall-diffusion and previously doped p+ at wafer surface. As a versatile micro-fabrication process, the technology promises to be widely used. As a typical application, a cantilever-shaped micro resonant vacuum detector was formed with both sidewall piezoresistive sensing and electrostatic resonance-driving elements integrated. In addition to satisfactory electric principles measured to verify the trench-sidewall technology, the resonant sensor was used to detect vacuum by measuring the value change of quality factor in terms of vacuum pressure. The detector was successfully embedded into a glass-frit vacuum package to evaluate the vacuum-package performance. The packaged vacuum of near 20 mbar with satisfactory stability of two months was measured.
Investigation of the nonuniformities in polyurethane chemical mechanical planarization pads
Authors: Zantye Parshuram B. , Kumar Ashok , Dallas William , Ostapenko Sergei , Sikder Arun K.
Published: February 2006

We have investigated the spatial variation of specific gravity (nonuniformities) in full size commercial pads for chemical mechanical polishing using a previously described nondestructive ultrasound transmission (UST) technique. After UST analysis, the different regions showing relatively higher and lower ultrasound permeability, which directly correlates with material density, were isolated and subjected to further evaluation of their mechanical properties using dynamic mechanical analysis (DMA) and tribological properties using a bench top chemical mechanical planarization (CMP) tester. Though the evaluated regions did not show significant variation in their tribological properties, presence of such regions in the body of the polishing pads has the potential to induce intermittent process defect during the CMP process.
Optical investigation of the interdot carrier transfer process in InAs∕GaAs quantum-dot heterosystems
Authors: Nee Tzer-En , Wang Jen-Cheng , Shen Hui-Tang , Cheng Chao-Ching , Lin Ray-Ming
Published: February 2006

The carrier-transport characteristics of the low and high surface density InAs∕GaAs quantum-dot (QD) heterosystems are studied in depth using photoluminescence measurements. It is found that both the anomalous temperature- and photoexcitation-dependent phenomena can be attributed to the carrier-thermalization processes. Photogenerated carrier redistribution leads not only to linewidth broadening but also to emission blueshifts for the radiative transitions in QD ensembles under various pump intensities. The short dot distance of a high dot-density system facilitates thermally excited carrier redistribution. However, due to the inhibition of photocarrier transfers, QD heterostructures that have a long interdot spacing exhibit more excitation insensitivity.
Quantum charge transportation in metal-oxide-Si structures with ultrathin oxide
Authors: Filip V. , Wong Hei , Nicolaescu D.
Published: February 2006

Quantum electron dynamics in metal-oxide-silicon structures with ultrathin oxide is calculated. A linear model of the surface-potential energy is used in the calculation. This treatment simplifies the computation for both the interface potential and the field penetration distance in the substrate. The electronic metastable states induced by the internal field penetration in the substrate and the running states in the gate region are then treated separately, with a weak condition for the continuity of the probability density at the substrate-dielectric interface. The probability current in the gate and then the total tunneling current are obtained for different gate voltages. While the spectrum of the transverse energy in the metastable states is assumed as continuous, the emerging probability current is shown to vanish for a finite number of values of the transverse energy, which may be interpreted as standing (bound) states in the structure. This model yields excellent fittings for the experimental data obtained from metal-oxide-semiconductor structures with different ultrathin gate dielectrics.
Optical properties of BC3 nanotubes
Authors: Chen S. C. , Chen I. Y. , Ho Y. H. , Lin M. F.
Published: February 2006

Optical absorption spectra of BC3 nanotubes are studied within the gradient approximation. BC3 nanotubes exhibit rich absorption peaks in the overall frequency because of a lot of one-dimensional energy bands. The threshold absorption frequency is ∼0.15γ0 for all BC3 nanotubes. Absorption peaks are mainly determined by the chirality, radius, and magnetic flux. BC3 nanotubes quite differ from carbon nanotubes in the low- and high-frequency absorption spectra. The calculated results are roughly consistent with the optical measurements, such as the threshold absorption frequency and the existence of the low-frequency absorption peaks.
Nanostenciling through a cm2-wide silicon membrane
Authors: Blech Vincent , Nobuyuki Takama , Kim Beomjoon
Published: February 2006

Nanostenciling is an area-selective technique for patterning surfaces in a single step, by depositing material through a shadow mask. In this article, we propose a cost-efficient technique for the fabrication of a cm2-scale stencil mask with the help of conventional photolithography and wet anisotropic etching. The mask consists of a freely suspended silicon membrane, with micro- and nanoscale apertures. Well-defined Au and Al patterns were transferred onto Si and SiO2∕Si substrates. Issues such as the geometry of the evaporation setup and the surface diffusion of evaporated atoms are discussed.
Nanoscopy of near-field distribution on plasmonic nanostructures
Authors: Luo Xiangang , Lv Yueguang , Du Chunlei , Ma Junxian , Wang Hao , Li Haiying , Yang Gairong , Lin Xiangdi , Yao Hanmin
Published: February 2006

The nanoscopy of the spatial distribution due to the interference of surface-plasmon polaritons (SPPs) on metallic nanostructures has been studied. The results show that the wavelength of plasmon wave becomes short when the thickness of the metallic film decreases because of SPPs coupling on both sides of the metallic structure. The interference of SPPs on the exit side of metallic nanostructures can redistribute the illumination light into nanoscale spatial distribution with high intensity, which beats the Rayleigh diffraction limit. The spatial resolution of sub-50-nm pattern on a metallic nanostructure with a thickness of 60nm was experimentally measured by using a traditional photoresist with an illumination wavelength of 436nm, which verifies the theoretical predictions. The information of the near-field distribution from corrugated metallic nanostructures is important for understanding the underlying physics, as well as for optimizing metallic nanostructures for possible applications.
Effect of buried Si∕SiO2 interface on dopant and defect evolution in preamorphizing implant ultrashallow junction
Authors: Hamilton J. J. , Colombeau B. , Sharp J. A. , Cowern N. E. B. , Kirkby K. J. , Collart E. J. H. , Bersani M. , Giubertoni D.
Published: February 2006

P -type ultrashallow junctions are widely fabricated using Ge preamorphization prior to ultralow-energy boron implantation. However, for future technology nodes, issues arise when bulk silicon is supplanted by silicon-on-insulator (SOI). An understanding of the effect of the buried Si∕SiO2 interface on defect evolution, electrical activation, and diffusion is needed in order to optimize the preamorphization technique. In the present study, boron has been implanted in germanium preamorphized silicon and SOI wafers with different preamorphizing implant conditions. Subsequent to implantation an isothermal annealing study of the samples was carried out. Electrical and structural properties were measured by Hall-effect and secondary-ion-mass spectroscopy techniques. The results show a variety of interesting effects. For the case where the Ge preamorphization end-of-range defects are close to the buried oxide interface, there is less dopant deactivation and less transient-enhanced diffusion, due to a lower interstitial gradient towards the surface.
Characterization of ultralow-energy implants and towards the analysis of three-dimensional dopant distributions using three-dimensional atom-probe tomography
Authors: Thompson Keith , Bunton J. H. , Kelly Thomas F. , Larson David J.
Published: February 2006

The addition of a local electrode geometry has transformed the conventional atom probe into a high-speed, high sensitivity tool capable of mapping three-dimensional (3D) dopant atom distributions in nanoscale volumes of Si. Fields of view exceeding 100nm in diameter and collection rates exceeding 18×106at.∕h are possible with the local electrode geometry. The 3D evolution of dopants, specifically dopant clustering, grain-boundary segregation, shallow-doped B layers, Ni–Si layers, and preamorphization regions, was analyzed. A 200eV B11 implant in Ge-amorphized Si was mapped. The native surface oxide, 8-nm-deep B-doped layer, and Ge distribution were simultaneously mapped in 3D space. A subsequent Ni silicide process was analyzed to show Ni penetration through the doped layer. In a heavily doped poly-Si sample, a cluster of dimensions 2×7×8nm3 and containing 264 B atoms was identified at the intersection of three grains. This shows that annealing highly overdoped thin poly-Si layers does not facilitate uniformly doped and highly conductive gate contact layers for nanoscale complementary metal-oxide semiconductor transistors.
Unique application of atomic force microscopy and scanning capacitance microscopy-two-dimensional-carrier profiling through thick insulating layers
Authors: Chao Kuo-Jen
Published: February 2006

Atomic force microscopy [Binnig et al., Phys. Rev. Lett. 56, 930 (1986)] and scanning capacitance microscopy [Williams et al., Appl. Phys. Lett. 55, 203 (1989)] (AFM/SCM) have been applied to study various implant structures of semiconductor devices. In this work, we present a unique application of AFM/SCM in two-dimensional-carrier profiling through a thick insulating layer. Therefore, AFM/SCM can be applied to delineate the lateral dopant diffusion and even to determine the lateral dopant diffusion length. In addition, an interesting phenomenon is observed when applying AFM/SCM to reveal the lateral dopant diffusion geometries on two different shapes of mask corners: one an obtuse corner and the other an acute corner. While it is reasonable and easily accepted that an obtuse corner in the mask would generally make the corresponding corner of the dopant-diffused region rounder, a shaper corner of the dopant-diffused region is observed on a corresponding acute corner in the mask. This demonstrates the utility of AFM/SCM in process control and failure analysis. Furthermore, three failed Si devices were studied by top-down AFM/SCM. These analyses show that the SCM images are clearly able to identify the nature and location of the three different types of defects. These random defects would be difficult to locate using more conventional cross-sectional analyses.
Gate oxide reliability in an integrated metal-oxide-semiconductor field-effect transistor-microelectromechanical system technology
Authors: Fleming Robert M. , Draper Bruce L.
Published: February 2006

We have demonstrated a simple technique for building n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) and complex micromechanical systems simultaneously instead of serially, allowing a more straightforward integration of complete systems. The fabrication sequence uses few additional process steps and only one additional masking layer compared with a microelectromechanical system (MEMS)-only technology, but exposes the MOSFET gate oxide to the extreme temperatures of MEMS processing. We find that the high-temperature MEMS anneals can greatly change the current-voltage characteristics of the SiO2 gate oxide film. Defects are introduced by the high-temperature processing which result in considerable positive-charge trapping at short times that leads to increased currents using high bias fields and short bias times. At longer times, the current across the oxide decays as 1/time suggesting electron traps that are uniformly distributed in the bulk of the oxide. A traditional reliability evaluation of the thick oxides using time-dependent dielectric breakdown is greatly hampered by excessive impact ionization that occurs at high gate voltages. This makes a rigorous evaluation of gate oxide lifetime at use fields difficult. We do note that while the current below breakdown is altered by the positive-charge trapping, the voltages at breakdown seen in ramps are not severely impacted by the high-temperature annealing. Breakdown voltages of films annealed at the highest of the temperatures studied here are about the same as those of unannealed films. The breakdown fields of these stressed oxides are 10–11MV∕cm, suggesting that reliable SUMMiT™ field-effect transistor process gate oxides can be fabricated as long as the use voltage is well below the onset for impact ionization.
Etch damage and deposition repair of vertical-cavity surface-emitting lasers
Authors: Leisher Paul O. , Raftery James J. , Kasten Ansas M. , Choquette Kent D.
Published: February 2006

Dielectric layers are often employed as etch masks for mesa and trench structures during vertical-cavity surface-emitting laser (VCSEL) fabrication. The removal of these mask layers by reactive ion etching results in unavoidable exposure of the top laser facet to sputtering. This sputtering is experimentally shown to impact the device performance. After a thickness of less than a quarter wavelength (∼60nm) has been removed, the VCSELs are no longer able to achieve lasing threshold. Simulation indicates that the reason for this is a decrease in quality factor by more than an order of magnitude. Consistent with this explanation is that the damage can be partially repaired (allowing laser oscillation) by depositing SiO2 to compensate for the missing semiconductor material.
Advanced electrical imaging of dislocations in Mg–In-codoped GaN films
Authors: Chen Sy-Hann , Hou Sheng-Ping , Hsieh J. H. , Chang F. C. , Chen W. K.
Published: February 2006

Conducting atomic force microscopy and scanning surface-potential microscopy have been applied to image the surfaces of Mg–In-codoped GaN films grown by low-pressure metal-organic chemical-vapor deposition. Biscyclopentadienylmagnesium (CP2Mg) and trimethylindium (TMIn) have been used as the codoping sources in the experiment. The dislocation density at the film surface reduces to the lowest level (∼1.0×109cm−2) when the TMIn∕CP2Mg flow rate ratio is about 1. The dislocation density tends to rise when the flow ratio increases, and carriers of the film accumulate near the rim of the dislocation at an accelerated speed. The work function of dislocation is also found lower than that of nondislocation areas. Such electrical unevenness may seriously influence the light emission of the component, which should not be ignored during fabrication and deserves careful attention.
All-around contact for carbon nanotube field-effect transistors made by ac dielectrophoresis
Authors: Zhang Zhi-Bin , Zhang Shi-Li , Campbell Eleanor E. B.
Published: February 2006

Carbon nanotube field-effect transistors (CNFETs) are fabricated by depositing one bundle of single-walled carbon nanotubes (SWNTs) per device between a pair of predefined Pd electrodes using ac dielectrophoresis. By repeating the process for the formation of the Pd electrodes after the bundle deposition, all-around Pd contacts are made to the SWNT bundles. After the formation of all-around contact, the CNFETs with only semiconducting SWNTs in the bundles retain a strong gate modulation with a high ratio of on to off current Ion∕Ioff⩾106. For the CNFETs with at least one metallic SWNT in the bundles, their gate modulation disappears and carbon nanotube resistors (CNRs) are obtained. The on current Ion of CNFETs is found to be sensitive to the process for the formation of all-around contact. In contrast, the two-probe resistance of CNRs is consistently reduced after the all-around contacts. The electrical measurements also indicate the presence of an interlayer residing at the SWNT/Pd contacts.
Synthesis and characterization of self-catalyzed CuO nanorods on Cu∕TaN∕Si assembly using vacuum-arc Cu deposition and vapor-solid reaction
Authors: Chen U. S. , Chueh Y. L. , Lai S. H. , Chou L. J. , Shih Han C.
Published: February 2006

Large-area arrays of copper oxide (CuO) nanorods were self-catalyzed and selectively grown on a Cu∕TaN∕Si assembly by combining vacuum-arc Cu deposition and vapor-solid reaction. X-ray-diffraction spectra showed the peaks of Cu films and CuO nanorods, respectively. Field-emission scanning electron microscopy images showed semialigned CuO nanorods with diameters of ∼40–80nm. High-resolution transmission electron microscopy images showed the structure of individual CuO nanorods and their [111] growth direction. Auger electron spectroscopy depth profiles showed the elemental distribution of the CuO∕a-TaN∕Si assembly. X-ray photoelectron spectrometry identified the chemical nature of the CuO nanorods. Their electron field-emission properties are discussed from the current-density–voltage curves and Fowler-Nordheim plots.
Coulomb blockade behavior in individual multiwalled carbon nanotubes
Authors: Hsiou Y. F. , Yang Y. J. , Chen C. D. , Chan C. H.
Published: February 2006

In this study, the transport characteristics of multiwalled carbon nanotubes were measured at low temperatures using the multiple-probe technique. Cr metal was used as the electrode material and good Ohmic contact to the tube was obtained. Measurements using two- and four-probe techniques showed Coulomb oscillation with nearly the same period, indicating that the local islands formed inside the nanotube. Our experiments and simulation results suggested that the local barriers existing between electrodes divided our tube into a chain of weakly coupled islands and were responsible for the observed Coulomb blockade behaviors.
In situ growth of single-walled carbon nanotubes by bimetallic technique with/without dielectric support for nanodevice applications
Authors: Shin K. Y. , Su H. C. , Tsai C. H.
Published: February 2006

The single-walled carbon nanotubes (SWNTs) have been considered as an alternative material for nanoelectronics, such as field-effect transistor or nanosensor, due to their unique electronic properties. However, an in situ growth process that can synthesize SWNTs with good position, diameter, and directional control is not yet available. Recent developments on the synthesis of SWNTs by deposition of ultrathin catalyst metal on the support of high specific areas were quite encouraging. In this study, high-yield vertically aligned SWNT arrays are demonstrated by in situ growth process with/without dielectric support material. In the case with dielectric support material, the role of dielectric support layer and the mechanisms of SWNT growth control will be discussed. Then, in the case without dielectric support material, the iron-based catalytic system revealed the ability to grow SWNTs from single-crystal silicon wafer directly, giving rise to the possible application of device structure with specific process module, for example, vertically aligned carbon nanotube field-effect transistor device may need to grow SWNT from doped-silicon area (source or drain well). In these experiments, micro-Raman spectroscopy and high-resolution transmission electron microscopy were utilized to characterize the SWNT properties and structures.
Correction of stray-light-induced proximity effect by complementary double exposure in microlithography
Authors: Kim Young-Chang , De Bisschop Peter , Leunissen Leonardus H. A. , Vandenberghe Geert
Published: February 2006

Stray light (flare) in optical microlithography causes critical dimension (CD) variation. We present a method to correct the CD variation by equalization of the stray-light distribution. This is achieved by doing a second “correction” exposure with the mask that has the reverse tone compared to the mask of the first exposure. A small exposure dose and large defocus are required for the correction exposure to mimic stray light. This correction method has been confirmed by experiments for 100nm features with standard ArF (193nm) lithographic processes.
Binary blends of diblock copolymers as an effective route to multiple length scales in perfect directed self-assembly of diblock copolymer thin films
Authors: Edwards Erik W. , Stoykovich Mark P. , Nealey Paul F. , Solak Harun H.
Published: February 2006

The directed assembly of binary blends of diblock copolymers on chemically nanopatterned substrates was investigated as a means to pattern features of controlled dimensions at the nanoscale. The lamella-forming blends assembled without defects and in registration with underlying chemical surface patterns that had periods LS that were commensurate with the bulk lamellar period of the blends LB. LB was tuned between the bulk lamellar periods of the block copolymers LO1 and LO2.
Heavy ion implantation in Ge: Dramatic radiation induced morphology in Ge
Authors: Janssens T. , Huyghebaert C. , Vanhaeren D. , Winderickx G. , Satta A. , Meuris M. , Vandervorst W.
Published: February 2006

High dose ion implantation of heavy elements in Ge induces a rough surface and profile distortions when measured with secondary ion mass spectrometry. In the case of Sb large subsurface holes are also induced by the implantation. The formation of these subsurface structures starts abruptly at a dose between 5∙1014 and 1015at∕cm2. The addition of a SiO2 capping layer on top of Ge prevents the formation of the surface roughness, but has limited impact on the void formation. These voids originate from vacancy clustering during the implant process. Anneal studies show that it is impossible to remove these structures by annealing, limiting the usefulness of high dose Sb implants in Ge for junction formation. In the case of As implantation a similar surface roughness is seen but no void formation. Adding a cap layer removes the surface roughness in this case and improves the secondary ion mass spectroscopy profiles.
Calculations of effect of anisotropic stress/strain on dopant diffusion in silicon under equilibrium and nonequilibrium conditions
Authors: Dunham Scott T. , Diebel Milan , Ahn Chihak , Shih Chen Luen
Published: February 2006

Understanding changes in dopant diffusion under strain is critical for controlling junction profiles in current and future very large scale integrated technology due to expanding use of large strains to enhance channel mobility. We use density functional theory calculations to investigate the stress dependence of boron (B) and arsenic (As) diffusion including vacancy (V) and interstitial (I) mechanisms under arbitrary stress/strain states. We have also analyzed the effects of stress on I and V diffusion with resulting impact on transient enhanced diffusion and coupled diffusion. For B diffusion, which is primarily mediated by I, we find greatly enhanced diffusion under tensile stress. Due to low symmetry of calculated transition state, we predict strongly anisotropic diffusion under anisotropic strain, with the strongest effects in direction of strain. This has a major impact on control of lateral junction abruptness as seen in two-dimensional simulations. The predicted behavior is consistent with combined analysis of vertical diffusion under biaxial [P. Kuo, J. L. Hoyt, J. F. Gibbons, J. E. Turner, and D. Lefforge, Appl. Phys. Lett. 66, 580 (1995)] and hydrostatic [Zhao et al.] stress. In contrast, we find isotropic As diffusion for both I and V mediated processes. We predict As diffusivity to increase substantially under compressive strain, but to show little change under tensile strain, consistent with experimental observations [N. Sugii, J. Appl. Phys. 96, 261 (2004)].
Crystallographic and electrical characterization of tungsten carbide thin films for Schottky contact of diamond photodiode
Authors: Liao Meiyong , Koide Yasuo , Alvarez Jose
Published: February 2006

Tungsten carbide (WC) thin films are sputter deposited using a WC target on different substrates such as Si (111), Si (100), sapphire (0001), and Si (111) coated with Ti thin film. These films are characterized for their crystallographic structure, composition, electrical resistivity, optical transmittance and oxidation resistance in order to use WC as thermally stable electrodes for diamond devices. Preferentially (100) oriented cubic WC1−x thin films are obtained at room temperature, irrespective of the various deposition conditions and substrates. The electrical resistivity of the films is about 200–300μΩcm. No deterioration of the properties occurs after annealing at 500°C in argon ambient. However, the films suffer from decomposition at 800°C with the depletion of carbon. The well characterized WC and Ti∕WC bilayer are used as Schottky and ohmic contacts of diamond photodiodes, respectively. The excellent Schottky properties with rectifying ratio of 108 and reverse leakage current lower than 10−14A are maintained upon annealing at 500°C for 4h. This work indicates that the WC-based Schottky and ohmic contacts are promising in diamond optoelectronic devices for high-temperature applications.
Electrical resistivity of polycrystalline Cu interconnects with nano-scale linewidth
Authors: Shimada Masahiro , Moriyama Miki , Ito Kazuhiro , Tsukimoto Susumu , Murakami Masanori
Published: February 2006

The maximum electrical conductivities in polycrystalline Cu interconnects with sub-100nm linewidth were extrapolated from the measured resistivities of the Cu interconnects with various linewidths (100–1000nm) using a Mayadas–Shatzkes (MS) model. These polycrystalline Cu interconnects with TiN cap layers were fabricated by the focused ion beam technique. The scattering parameters by the surface and grain boundary, which were needed to extrapolate the resistivities of the sub-100nm Cu interconnects (using the MS model), were determined to be zero and 0.5, respectively. The result suggested that the grain boundary scattering primarily increased the resistivity of the polycrystalline Cu interconnects. We concluded that large grained Cu interconnects and ultrathin barrier layers were essential to realize low resistance nano-scale Cu interconnects in the future ultralarge scale integration devices.
Lithographic flare measurements of Intel’s microexposure tool optics
Authors: Chandhok Manish , Lee Sang H. , Roberts Jeanette , Rice Bryan J. , Cao Heidi B.
Published: February 2006

Measurements of flare as a function of feature size, pitch, and orientation have been made on Intel’s extreme ultraviolet microexposure tool (MET) using a high sensitivity photoresist. The high sensitivity photoresist does not cross-link at the high doses required to measure flare. The predicted value for intrinsic flare for the MET from mid-spatial frequency roughness (MSFR) of mirror surfaces is 3.5%. After addition of the contribution to flare from high order aberrations to that from MSFR, the modeled value is in excellent agreement with the measured flare for the 1μm line of 4%. The measured flare in the horizontal direction is 5% and is higher than the flare in the vertical direction. The point spread function due to scatter has been computed and the modulation transfer function of the system as a function of pitch has also been measured.
Cl
2
∕
O
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-inductively coupled plasma etching of deep hole-type photonic crystals in InP
Authors: Carlström C. F. , van der Heijden R. , Karouta F. , van der Heijden R. W. , Salemink H. W. M. , van der Drift E.
Published: February 2006

We have developed an inductively coupled plasma etching process for fabrication of high-aspect-ratio hole-type photonic crystals in InP, which are of interest for optical devices involving the telecommunication wavelength of 1550nm. The etching was performed at 250°C using Cl2∕O2 chemistry for sidewall passivation. The process yields nearly cylindrical features with an aspect ratio larger than 10 for hole diameters near 0.25μm. This makes them very suitable for high-quality photonic crystal patterns.
Ni-carbon nanotubes nanocomposite for robust microelectromechanical systems fabrication
Authors: Tsai Li-Nuan , Cheng Yu-Ting , Hsu Wensyang , Fang Weileun
Published: February 2006

This article presents a novel fabrication process to enhance the operational performance and reliability of electrothermal microactuators. Carbon nanotubes (CNTs) (outer diameter: 10–20nm, inner diameter: 5–10nm, length: 0.5–200μm) are incorporated in an electrolytic nickel deposition process in which a well-dispersed Ni-CNTs colloidal solution is made by a special acid oxidative method to synthesis a Ni-CNTs nanocomposite for device fabrication. Measurement results show that the microactuator plated with CNTs (0.028g∕L) needs the power requirement less 95% than the pure nickel device at the same output displacement of 3μm. The performance improvement of the electrothermal microactuator made of the nanocomposite, including device strength and power efficiency, has shown to be similar to the Ni-diamond composites (L. N. Tsai, G. R. Shen, Y. T. Cheng, and W. S. Hsu, The 54th Electronic Components and Technology Conference, June 2004, pp. 472–476)). In addition, the E∕ρ ratio of the Ni-CNTs composite can be enhanced to 1.47 times higher than that of pure nickel, which is a fascinating result for resonant device fabrication.
Aligned carbon nanotubes/fibers for applications in vacuum microwave amplifiers
Authors: Milne W. I. , Teo K. B. K. , Minoux E. , Groening O. , Gangloff L. , Hudanski L. , Schnell J.-P. , Dieumegard D. , Peauger F. , Bu I. Y. Y. , Bell M. S. , Legagneux P. , Hasko G. , Amaratunga G. A. J.
Published: February 2006

Most long-range telecommunication systems are based upon microwave links. The transmitters use microwave amplifiers which in the very near future will be required to work at up to 30–100GHz with output power in the region of a few tens of watts. Carbon nanotubes (CNTs), which exhibit extraordinary field emission properties because of their high electrical conductivity, ideal high aspect ratio whisker-like shape for geometrical field enhancement, and remarkable thermal stability, can be used as the emitter in such applications. This article will describe the plasma enhanced chemical vapor deposition growth of vertically aligned carbon nanotubes, and how well controlled arrays of such structures can be grown. We will also describe how high current densities of ∼1A∕cm2, under direct current and 1.5GHz direct modulation, can be obtained from CNT cathodes. These CNT cold cathodes offer considerable weight and size savings over conventional hot cathodes used in microwave applications (e.g., SATCOM, radar).
Comparison of scanning capacitance microscopy and scanning Kelvin probe microscopy in determining two-dimensional doping profiles of Si homostructures
Authors: Park S.-E. , Nguyen N. V. , Kopanski J. J. , Suehle J. S. , Vogel E. M.
Published: February 2006

Two-dimensional (2D) doping profiles of layered, differently doped, n-step Si homostructures were measured by scanning capacitance microscopy (SCM) and scanning Kelvin probe microscopy (SKPM). The calibrated doping concentration of the n-type Si layers was in the range of 4.2×1014cm−3to1.7×1019cm−3. For the SCM images, the measured ΔC∕ΔV signals were converted to 2D doping concentrations using the NIST FASTC2D program. To compare the SCM-based 2D dopant profiles with those obtained by SKPM, a contact potential difference (CPD) between a probe tip and the Si sample surface was measured with SKPM. Using the relation between a work function and a doping concentration of Si, the doping concentrations were extracted from the measured CPD. The SCM results had good agreements with the calibrated data, but the SKPM results showed some differences due to the presence of the top native oxide layer.
Nanoscale layer etching by short-time exposure of substrates to gas discharges using moving patterned shutter
Authors: Oehrlein G. S. , Hua X. , Stolz C. , Jiang P.
Published: February 2006

We use a moving shutter containing slits in close contact with a substrate to control the interaction time of gas discharges with the substrate for nanoscale layer/nanostructure processing. Both shutter and substrate are located on the rf-powered electrode and can be biased relative to the plasma. Once the plasma properties and electrode bias voltage are fully established, the shutter with slits begins to move at a controlled speed across the substrate to expose the substrate for the desired interaction time to the plasma. We show that for a fluorocarbon-based plasma etching process, steady-state etching conditions can be achieved within less than 2s. This approach enables precise removal or deposition of nanoscale layers employing gas discharges.
Investigation of the magnetic susceptibility of nanocomposites obtained in zero-field-cooled conditions
Authors: Jacobsohn L. G. , Hundley M. F. , Thompson J. D. , Dickerson R. M. , Nastasi M.
Published: February 2006

An investigation of the effect of particle size, size dispersion, intensity of applied field, and anisotropy constant on the characteristics of the superparamagnetism of magnetic nanocomposites was carried out using an integral equation for the magnetic susceptibility that assumes uniaxial anisotropy. The nanoscopic phase of the composites is composed of noninteracting randomly oriented single-domain spheres embedded in a nonmagnetic host. A Gaussian distribution for the particle diameter dispersion was used in agreement with experimental results. The results show that the above parameters alter the position and width of the superparamagnetic peak, but only particle size and size dispersion can affect the shape of the high-temperature susceptibility tail above the peak temperature. Higher size dispersion values lead to broader peaks shifted to higher temperatures and flatter high-temperature tails. Simulations of experimental data obtained from cobalt nanocomposites, where the average particle size and size distribution were previously determined by transmission electron microscopy, yielded very good agreement.
Thermal coupling in multishot laser microvia drilling for interconnection application
Authors: Tan B. , Venkatakrishnan K.
Published: February 2006

Microvia for interconnect application was drilled using multishot laser pulses of nanosecond duration. It is observed that time delay between successive pulses have an effect on the shape of the drilled microvias. There is a thresholdlike time delay at which microvia suffers an abrupt deformation which creates voids and complication in the subsequent metallization process. Thermal coupling between successive pulses could be used to explain this phenomenon. To avoid deformation, a longer time delay between subsequent pulses is preferred.
Methods for fabricating Ohmic contacts to nanowires and nanotubes
Authors: Stern E. , Cheng G. , Klemic J. F. , Broomfield E. , Turner-Evans D. , Li C. , Zhou C. , Reed M. A.
Published: February 2006

A comparison of methods to create Ohmic contacts to semiconductor nanowires (NWs) and carbon nanotubes (CNTs) is presented. A Ni∕Au lift-off metallization was used to contact GaN and In2O3 NWs and CNTs using electron-beam (e-beam) or optical lithography. In order to render the metal-semiconductor contacts Ohmic, e-beam-processed devices are found to require a postfabrication, high-temperature anneal, whereas the use of an oxygen plasma prior to metallization is found to be crucial for devices defined by optical lithography.
Fabrication of hybrid bilayer nanostructure by duo-mold imprinting
Authors: Zhao Wei , Low Hong Yee
Published: February 2006

A bilayer scaffold consisting of a thermoplastic and thermoset has been fabricated via duo-mold imprinting method. The molds used in this fabrication are with comparable surface energy. The preferential demolding between the two molds was achieved by utilizing the adhesion difference between the molds and the two polymers while the transfer of the polymers from the mold to the substrate was guided by the large contrast of surface energy between the mold and the substrate. The use of thermoset polymer imparts the thermal and mechanical stabilities into the imprinted structures so that a higher imprinting temperature is feasible. A higher imprinting temperature is found to facilitate the transfer of the imprinted polymer from the mold to the substrate by enhancing the wetting between the polymer and the substrate.
Synthesis and characterization of calixarene derivatives as resist materials for electron-beam lithography
Authors: Aktary Mirwais , Westra Kenneth L. , Freeman Mark R. , Tanaka Yasutaka
Published: February 2006

This article describes the electron-beam resist properties of a class of calixarene derivatives for high-resolution electron-beam lithography. The derivatives, which are based on a calix[4]resorcinarene framework, are unique in that the bridging carbon is functionalized with a long chain (C11) alkyl group. Our studies reveal that the electron-beam sensitivity of the calix[4]resorcinarenes is markedly lower than a standard calix[6]arene material, consistent with the increase in sensitivity that is observed with the number of monomers for these systems. Comparison of the sensitivity of the calix[4]resorcinarenes with four member calix[4]arenes from the literature reveals very similar values, indicating that chemical modification at the bridging carbon has no appreciable effect on sensitivity. The minimum linewidth resolution of the calix[4]resorcinarenes under our experimental conditions was found to be approximately 50nm at a threshold line dose of 65nC∕cm. Our results also demonstrate the ability to chemically modify calixarene compounds at the bridging carbon position while maintaining electron-beam sensitivity. These findings are intended to open avenues for more extensive modification schemes in developing resist materials for high-resolution electron-beam lithography.
Thermal simulations of three-dimensional integrated multichip module with GaN power amplifier and Si modulator
Authors: Anderson T. J. , Ren F. , Covert L. , Lin J. , Pearton S. J.
Published: February 2006

A finite-element simulation was used to quantitatively estimate the heat transfer in a three-dimensional multichip module (MCM) consisting of a GaN power amplifier with solder-bump-bonded Si modulator and integrated antenna on a high-resistivity SiC substrate under various conditions of power density and substrate and epi thicknesses via wire thickness and effective heat transfer coefficient. The maximum temperature in the integrated-antenna approach occurred in the center of the MCM. At a GaN power amplifier power level of 3W∕mm, a steady-state temperature of ∼125°C was reached in ∼20s. Bulk GaN substrates were also found to provide good thermal transfer characteristics, while sapphire produced an increase in temperature almost a factor of 3 higher than for SiC. At a power density of 10W∕mm, the steady-state operating temperature was ∼400°C even with SiC substrates.
Effect of rapid thermal annealing on the optical and electrical properties of metamorphic high electron mobility transistor structures with composite InGaAs∕InP channel
Authors: Liu Yuwei , Wang Hong
Published: February 2006

The electrical and optical properties of metamorphic InGaAs∕InP composite channel high electron mobility transistor (HEMT) structures subjected to rapid thermal annealing (RTA) are systematically investigated in the temperature range of 350–650°C. The metamorphic structures exhibit different degradation behaviors in different temperature ranges as compared to lattice-matched (control) structure. For the samples annealed at temperature lower than 550°C, increase in annealing temperature results in a larger degradation of sheet carrier density (ns) and photoluminescence (PL) intensity. However, no further reduction of ns was observed in the metamorphic samples after RTA at temperature higher than 550°C. An improvement of PL intensity in the temperature range of 550–650°C for metamorphic samples was even observed. This behavior is absent in the lattice-matched HEMT structures. Possible mechanisms governing the change of the electrical and optical properties in metamorphice HEMT structures are discussed. Our experimental results reveal that, compared to the lattice-matched structures, the InP HEMT structures grown on GaAs using metamorphic structure could present similar thermal stability up to 650°C even though a metamorphic strain-relief buffer is included. This may partially ease the concerns on the thermal stability of the metamorphic HEMT structures.
Luminescent and structural characteristics of ZnO nanorods fabricated by postannealing
Authors: Lin Chin-Ching , Liao Hung-Chou , Chen San-Yuan , Cheng Syh-Yuh
Published: February 2006

Well-aligned ZnO nanorods grown on silicon substrates buffered with ZnO film were postannealed at 200–1000°C in various atmospheres. The optical properties of ZnO nanorods were much improved by annealing at high temperatures in both atmospheres of N2 and O2. This improvement was ascribed to the decrease in structure defects as compared to as-grown ZnO nanorods. However, for the ZnO nanorods annealed in H2∕N2, a stronger UV emission occurs at 600°C; above that the UV emission rapidly disappeared, which was attributed to the collapse of the ZnO nanorods due to H2 etching during a higher-temperature annealing in H2∕N2. The crystallinity and optical properties of the ZnO nanorods can be controlled by postannealing treatment.