bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of 1∕4 wave plate by nanocasting lithography
Authors: Yoshikawa Takashi , Konishi Takaaki , Nakajima Masaki , Kikuta Hisao , Kawata Hiroaki , Hirai Yoshihiko
Published: January 2006

Nanocasting lithography is one of the convenient ways to fabricate micronanostructures using various kinds of polymers without special tools. Nanocasting lithography is demonstrated for a 50nm half-pitch pattern, high-aspect-ratio micropillars, and high-aspect-ratio nanogratings for wave plates. The defect, which is caused by an air bubble in the sub-100nm pattern, is successfully eliminated by vacuum baking after spin coating of a polymer. Also, a high-aspect-ratio structure having 400nm pitch and 1.9μm height was successfully fabricated by polycarbonate for 2000×200μm. These structures show a 1∕5 wave shift for the 633nm wavelength.
Passivation of zinc–tin–oxide thin-film transistors
Authors: Hong David , Wager John F.
Published: January 2006

A methodology for the passivation of bottom-gate thin-film transistors (TFTs) utilizing zinc–tin–oxide as the channel layer and silicon dioxide as the passivation layer is presented. This methodology involves annealing of the TFT after channel layer deposition and an additional anneal after thermal evaporation of a SiO2 passivation layer. Passivated zinc–tin–oxide TFTs possess electrical characteristics equivalent to those of unpassivated, air-exposed devices. In contrast, TFT electrical performance is dramatically degraded if a zinc–tin–oxide TFT is covered with a dielectric layer and does not undergo both types of anneal. In addition to silicon dioxide, successful passivation of zinc–tin–oxide TFTs is accomplished using thermally evaporated calcium fluoride, germanium oxide, strontium fluoride, or antimony oxide as passivation dielectrics.
Propagating modes in subwavelength cylindrical holes
Authors: Catrysse Peter B. , Shin Hocheol , Fan Shanhui
Published: January 2006

We analyze subwavelength cylindrical holes in an optically thick metallic film with the metal described by a plasmonic model. We emphasize that such holes always support propagating modes near the surface plasmon frequency, regardless of how small the holes are. Based on this analysis, we design both single holes and hole arrays in which propagating modes play a dominant role in the transport properties of incident light. These structures exhibit a region of operation that to the best of our knowledge has not been probed yet experimentally, while featuring a high packing density and diffraction-less behavior.
Measurement of residual thickness using scatterometry
Authors: Fuard David , Perret Corinne , Farys Vincent , Gourgon Cécile , Schiavone Patrick
Published: January 2006

Nanoimprint lithography (NIL) processes have the characteristic that a residual resist layer is always present between the nanoimprinted features. This residual resist layer must be removed to obtain usable resist masks for pattern transfer. As this resist layer is removed using oxygen-based plasma processes, the residual thickness nonuniformity translates into feature width dispersion. Thus, the uniformity of this residual thickness after imprint remains an important issue for nanoimprint lithography and a reliable metrology procedure is required for. At present, the standard measurement method is based on scanning electron microscopy (SEM) cross section, which is destructive, time consuming, and may sometimes provide only moderate accuracy. The work presented here will assess and show the interest of scatterometry, which is a nondestructive optical method of metrology that can be easily applied to NIL. This measurement procedure exhibits very good accuracy on the two-dimensional-feature geometry determination, especially for residual thickness. Scatterometry also eases time-consuming studies like residual thickness measurement at the local scale or at the wafer scale. Moreover, this article shows that the imprint uniformity studies provide very interesting information on the mold deformation.
Innovative approach to nanoscale device fabrication and low-temperature nitride film growth
Authors: Akhadov Elshan A. , Read D. E. , Mueller Alexander H. , Murray Jacqueline , Hoffbauer Mark A.
Published: January 2006

Energetic neutral beam lithography/epitaxy (ENABLE) was used for etching very high-aspect-ratio nanoscale structures into polymers and for growing templated AlN films at low temperatures. Various methods were used for masking polymeric films for selective etching by energetic oxygen atoms to fabricate sub-100nm structures with aspect ratios exceeding 35:1. ENABLE was also utilized for low-temperature growth of AlN into previously etched polymer templates to directly form AlN wires. By taking advantage of the unique processing capabilities of ENABLE, new opportunities for making delicate nanostructures are made possible.
Traceable calibration of critical-dimension atomic force microscope linewidth measurements with nanometer uncertainty
Authors: Dixson R. G. , Allen R. A. , Guthrie W. F. , Cresswell M. W.
Published: January 2006

The use of critical dimension atomic force microscopes (CD AFMs) in semiconductor manufacturing, both for process control and as a reference metrology tool, is increasing. If the tip width is calibrated consistently between measurements, a CD AFM can function as an excellent width comparator. Relative widths can be measured with uncertainties of 1 nm or less. However, to perform accurate measurements, the absolute tip width must be accurately calibrated. Until recently, conventional methods for accomplishing this had standard uncertainties on the order of 5 nm. Recently developed CD reference materials now make it possible to calibrate absolute tip width with uncertainties at the 1 nm level. The highlights of our method are: (1) the use of single-crystal silicon and preferential etching to pattern well-defined and highly uniform features; (2) the use of high resolution transmission electron microscopy (HRTEM) to access the Si lattice spacing directly as a source of traceable width information, and (3) the use of CD AFM to transfer width information from the HRTEM samples. These standards are known as single crystal critical dimension reference materials (SCCDRM), and prototype SCCDRMs have recently been delivered to SEMATECH Member Companies for evaluation.
Visualization and in situ contacting of carbon nanotubes in a scanning electron microscope
Authors: Croitoru M. D. , Bertsche G. , Kern D. P. , Burkhardt C. , Bauerdick S. , Şahakalkan S. , Roth S.
Published: January 2006

A method for contacting carbon nanotubes on an insulating surface is presented. Tubes which are already connected to prefabricated electrodes can be visualized in the scanning electron microscope exploiting voltage contrast at low beam energies. Additional connections to tubes identified in this way are fabricated by in situ electron beam induced deposition from metalorganic precursors such as tungsten hexacarbonyl. A resistivity of 0.15Ωcm before annealing has been achieved so far with this material.
Defect control in nanoimprint lithography
Authors: Chen Lei , Deng Xuegong , Wang Jian , Takahashi Ken , Liu Feng
Published: January 2006

Major defects encountered in nanoimprint lithography (NIL) process, especially particle and gap associated defects are studied in this article. Unlike in other lithography, a particle induced defect in NIL is larger than the particle itself. To remove the particles, a dry clean process for the nanostructure-patterned surface is explored. The gap-associated defect is a unique phenomenon in NIL, which is induced by the incomplete contact between mold and substrate. The pressure required to eliminate voids during the NIL process is discussed. Based on the studies, both visual particle and void associated defects free 4in. and even larger wafers are achieved.
Nanoscale patterning in application to materials and device structures
Authors: Erbe A. , Jiang W. , Bao Z. , Abusch-Magder D. , Tennant D. M. , Garfunkel E. , Zhitenev N.
Published: January 2006

We present fabrication schemes for nanoscale molecular junctions, which allow the deposition of molecules after the fabrication steps that can uncontrollably affect the electrical properties of the molecular layers. The two techniques described here use shadow mask evaporation and nanotransfer printing. In order to make reliable contacts with the molecules (or molecular monolayers) the morphology of the contacting metals has to be optimized and controlled. We therefore characterize the surfaces of the contacting metals using scanning electron microscopy and scanning probe microscopy at various stages of the fabrication. Based on these results we developed methods to improve the morphology in order to realize more reliable metal-molecule contacts. It is shown that improvement of the surface topography of the metals indeed leads to metal-molecule-metal junctions with a very low failure rate.
Electrodes for carbon nanotube devices by focused electron beam induced deposition of gold
Authors: Brintlinger T. , Fuhrer M. S. , Melngailis J. , Utke I. , Bret T. , Perentes A. , Hoffmann P. , Abourida M. , Doppelt P.
Published: January 2006

Individual carbon nanotubes (CNTs) often occur in randomly dispersed two-dimensional as well as three-dimensional configurations that make device fabrication difficult. Making electrical contact to such CNTs is of practical interest. To this end, we make contact to individual metallic single-walled carbon nanotubes (SWNTs) using the focused electron-beam-induced deposition (FEBID) of pure gold. The SWNTs are grown by chemical vapor deposition on a flat substrate, and the gold leads are made through FEBID using inorganic metallic precursor gas, chloro(trifluorophosphine)gold(I), or AuClPF3, in a high vacuum scanning electron microscope. The same scanning electron microscope is also used to image carbon nanotubes, allowing for simultaneous alignment. We find equivalent one-dimensional resistivities for the SWNTs of 10–15kΩ∕μm for both FEBID gold leads and leads deposited using conventional electron-beam lithography (EBL) and thermal evaporation of gold, suggesting similarly low contact resistances. We use electrostatic force microscopy to verify quantitatively similar contact resistances for one nanotube sample, 10(±6) and 54(±6)kΩ, for FEBID and EBL leads, respectively, with most voltage dropping across the long metallic SWNT.
Reduction of oxide layer on Ru surface by atomic-hydrogen treatment
Authors: Nishiyama I. , Oizumi H. , Motai K. , Izumi A. , Ueno T. , Akiyama H. , Namiki A.
Published: January 2006

The reduction of Ru oxide was examined as a way of cleaning the cap layer of multilayer mirrors in extreme ultraviolet lithography (EUVL). Ru deposited on a Si surface was oxidized using electron cyclotron resonance (ECR) O2 plasma, and then treated with atomic hydrogen generated with a hot tungsten wire. An analysis of the surface composition by x-ray photoelectron spectroscopy and Auger electron spectroscopy revealed that atomic hydrogen removed the Ru oxide resulting from the ECR O2 plasma treatment. Additionally, atomic force microscopy observations showed that this treatment caused no increase in the surface roughness of the Ru. This indicates that the surface oxidation of EUVL mirrors is reversible, and can largely be eliminated by using atomic hydrogen and the proper cap layer.
Dependence of linewidth and its edge roughness on electron beam exposure dose
Authors: Kotera M. , Yagura K. , Niu H.
Published: January 2006

Electron beam lithography simulation is presented. A line pattern edge roughness of a resist after development process is discussed based on simulations of electron scattering in the resist film and the resist development process. Fixed threshold energy model is applied for the simulation and variations of linewidth and the line edge roughness are obtained as functions of the incident electron energy, resist thickness, and electron doses. The energy range calculated is from 1to5keV, the resist thickness ranges from 20to70nm, and the electron dose ranges from 1to100μC∕cm2. The resist assumed is poly(methylmethacrylate) and the film is on a Si substrate. In the present study, the threshold energy density is determined as 1.44×1021(eV∕cm3) to draw a given linewidth of 100nm, then the value of the line edge roughness is obtained. The minimum line edge roughness is obtained when the dose is more than that to produce the designed linewidth. As the dose is increased more than that to obtain the minimum edge roughness, the roughness increases with increasing the dose. For very large doses the roughness decreases with the dose, as it is explained by the statistical characteristics.
Fabrication of enclosed nanochannels using silica nanoparticles
Authors: Xia Deying , Brueck S. R. J.
Published: January 2006

We report a simple and inexpensive approach to the fabrication of enclosed nanoscale channels composed of silica nanoparticles on planar Si surfaces using interferometric lithography to define the long-range pattern in a photoresist film followed by spin-coating self-assembly of colloidal silica nanoparticles and high-temperature calcination to remove the photoresist leaving open nanochannels. Channel structures with channel width and height ranging from ∼100nm to over 1μm were formed over large areas with different particle sizes and channel profiles. The dimensional scale of these ordered arrays of enclosed channels can be easily controlled through the parameters in the photoresist patterning and the spin-coating steps. Complex, multilayer structures have been generated using this approach as well. This process opens a route to fabricating ordered enclosed nanochannels with potential uses in photonics, molecular/biological sensors, biological separations and catalysis.
Formation of Ti–Si–N film using low frequency, high density inductively coupled plasma process
Authors: Ee Y. C. , Chen Z. , Chan L. , See K. H. , Law S. B. , Xu S. , Tsakadze Z. L. , Rutkevych P. P. , Zeng K. Y. , Shen L.
Published: January 2006

Titanium silicon nitride (Ti–Si–N) has emerged as a strong candidate for next generation diffusion barrier material in copper/low-k dielectric back-end-of-line device fabrication. Low frequency, high density inductively coupled plasma process has been developed for the growth of Ti–Si–N film. This work employs the reaction between TixSiy and the nitrogen plasma. Ti–Si–N films have been successfully grown over different process conditions. Film properties were characterized by Rutherford backscattering spectrometry (RBS), x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy, x-ray diffraction (XRD), and four-point resistivity probe. RBS reveals that 2–67at.% of nitrogen can be achieved through the implantation of nitrogen in TixSiy film. XPS and XRD results show that TiN and Si3N4 are successfully formed. As the external bias increases from 100to300V, there is an 80% increase in sheet resistance. Other process conditions investigated do not show a significant effect on film sheet resistance. Increasing argon plasma activation time can significantly increase the implantation depth of nitrogen into TixSiy substrate.
Structural, electrical, and mechanical properties of nc-TiC∕a-SiC nanocomposite thin films
Authors: Eklund P. , Emmerlich J. , Högberg H. , Wilhelmsson O. , Isberg P. , Birch J. , Persson P. O. Å. , Jansson U. , Hultman L.
Published: January 2006

We have synthesized Ti–Si–C nanocomposite thin films by dc magnetron sputtering from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at temperatures from room temperature to 300°C. Electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy showed that the films consisted of nanocrystalline (nc-) TiC and amorphous (a-) SiC, with the possible presence of a small amount of noncarbidic C. The growth mode was columnar, yielding a nodular film-surface morphology. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 and 290GPa, respectively. The electrical resistivity was 330μΩcm for optimal Ar pressure (4mTorr) and substrate temperature (300°C). The resulting nc-TiC∕a-SiC films performed well as electrical contact material. These films’ electrical-contact resistance against Ag was remarkably low, 6μΩ at a contact force of 800N compared to 3.2μΩ for Ag against Ag. The chemical stability of the nc-TiC∕a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive-gas test, with no N, Cl, or S contaminants entering the bulk of the films.
High-efficiency light-emitting device based on silicon nanostructures and tunneling carrier injection
Authors: Wong Hei , Filip V. , Chu P. L.
Published: January 2006

Light-emitting device structure (Si∕SiO2/low-dimensional Si∕Si3N4∕Si) is proposed. The low-dimensional Si governed the photon generation efficiency and energy spectrum whereas the asymmetry barrier heights on both sides formed by the SiO2 and Si3N4, respectively, provide high-efficiency carrier injection based on direct tunneling and maximize the rate of the recombination events taking place in the low-dimensional silicon. Detailed theoretical modeling of carrier transportation in this device structure is developed. Theoretical calculations demonstrate that the recombination rate of carrier with this structure can be as high as 3×1023cm−2s−1 and are governed by the barrier heights, thickness of the dielectric films, and the width of low-dimensional Si region.
Ultra small self-organized nitride nanotips
Authors: Ji L. W. , Fang T. H. , Hung S. C. , Su Y. K. , Chang S. J. , Chuang R. W.
Published: January 2006

Vertical self-organized nanotips were grown on InGaN film via metal-organic chemical vapor deposition (MOCVD) and thermal annealing. It was found that the typical height of these nanotips is 20nm with an average width of 1nm. It was also found that the local density of the vertically grown self-assembled InGaN nanotips could reach 1.6×1013cm−2. The possible formation mechanism of self-assembled nanotips has been also discussed in this work. Such a small size of vertical nanotips could show strong quantum localization effects and have potential applications in field emission devices, near-field microscopy, and blue photonics.
Reactive-ion etching of high-Q and submicron-diameter GaAs∕AlAs micropillar cavities
Authors: Varoutsis S. , Laurent S. , Sagnes I. , Lemaître A. , Ferlazzo L. , Mériadec C. , Patriarche G. , Robert-Philip I. , Abram I.
Published: January 2006

We present a fabrication process allowing the realization of high-Q and small-diameter micropillar cavities. The fabrication involves molecular beam epitaxy, electron-beam lithography, and reactive ion etching (RIE). The introduction of O2 to the SiCl4 RIE plasma and the dynamic adjustment of its flow rate enable the control of the etched profile throughout the process, through the deposition of silicon oxide on the vertical etched surfaces. The resulting cavities have very smooth, straight, and vertical sidewalls and remain optically and mechanically stable for long periods of time. The optical modes sustained by these cavities exhibit record quality factors in excess of 1200 for pillar diameters close to 400nm, which underscores the quality of our process.
Electrical transport of tetragonal boron nanobelts
Authors: Kirihara K. , Wang Z. , Kawaguchi K. , Shimizu Y. , Sasaki T. , Koshizaki N. , Hyodo H. , Soga K. , Kimura K.
Published: January 2006

We measured electrical conductances in single crystalline boron nanobelts having α-tetragonal crystalline structure. The doping experiment of Mg was carried out by vapor diffusion method. We obtained ohmic contacts to both pure and Mg-doped nanobelt by metal electrodes of Ni∕Au bilayer. From the temperature dependence of electrical conductance, we found that the pure boron nanobelt is a semiconductor. The electrical conductivity of pure boron nanobelt was estimated to be on the order of 10−3(Ωcm)−1 at room temperature. After Mg vapor diffusion, the electrical conductance increased by a factor of 100 but a transition to metal was not observed.
Effects of doping type and concentration on precipitation of nanometer arsenic clusters in low-temperature-grown GaAs
Authors: Lee W. N. , Chen Y. F. , Huang J. H. , Guo X. J. , Kuo C. T.
Published: January 2006

In this study, the effects of doping type and concentration on arsenic precipitation in low-temperature-grown GaAs upon postgrowth annealing at 600, 700, and 800 °C were investigated. Three undoped/Si-doped/undoped (i-n-i) regions and three undoped/Be-doped/undoped (i-p-i) regions were grown by low-temperature molecular beam epitaxy. The results show that arsenic precipitation is dependent on doping type and doping concentration. Arsenic depletion was observed in all Be-doped layers for all annealing temperatures. However, a “dual” arsenic precipitation behavior was observed in Si-doped layers: As accumulates in [Si]=2×1018cm−3 doped layers, while it depletes in [Si]=2×1016 and 2×1017cm−3 doped layers. We attribute this “dual” As precipitation phenomenon in Si-doped layers to the different depletion depths.
Electrochemical fabrication of cobalt and nickel tips for scanning tunneling microscopy
Authors: Albonetti Cristiano , Cavallini Massimiliano , Massi Massimiliano , Moulin Jean François , Biscarini Fabio
Published: January 2006

Scanning tunneling microscopy (STM) is a powerful technique to map the distribution of the density of electronics states of conductive surfaces with angstrom (Å) resolution. STM requires sharp conductive tips in order to operate in ambient conditions, which are stable with respect to oxidation. We describe a procedure to obtain high quality tips from wires of different materials such as Co and Ni. We discuss in detail the electrochemical process employed in the fabrication of the tips and assess the shape of the tips by optical microscopy and scanning electron microscopy (SEM). These tips yield high-resolution STM images even after a few weeks of exposure to air.
Acidic acrylic polymers for nanoimprint lithography on flexible substrates
Authors: Liao Wen-chang , Hsu Steve Lien-Chung
Published: January 2006

A series of environmental friendly acidic resists were prepared for nanoimprint lithography on flexible plastic substrates. These resists can be easily removed by an aqueous base solution at the final stripping step instead of using an organic solvent or reactive ion etching (RIE), which is used in conventional imprint processes. The resist polymers were prepared via free radical copolymerization of methylmethacrylate (MMA), n-butylacrylate (n-BA) and methacrylic acid (MAA) monomers. For use on flexible plastic substrates, the glass transition temperatures of these polymers were adjusted to a range of 25–41 °C according to the molar ratio of the monomers. The weight average molecular weights (Mw) of these polymers were between 30 000 and 40000g∕mole measured by GPC. Replications of high-density line and space patterns with resolution of 5μm and 100 nm were obtained on a flexible indium tin oxide/poly(ethylene terephthalate) (ITO/PET) substrate. The subsequent ITO etching pattern was also achieved.
Proton and anion distribution and line edge roughness of chemically amplified electron beam resist
Authors: Kozawa Takahiro , Yamamoto Hiroki , Saeki Akinori , Tagawa Seiichi
Published: January 2006

Nanoscale resist topography such as line edge roughness (LER) or line width roughness (LWR) is the most serious concern in sub-100 nm fabrication. Many factors have been reported to affect LER. However, the cause of LER is still unclear. We calculated proton and anion distribution of chemically amplified electron beam resists in order to make clear the cause of LER. Counter anion distribution is significantly different from proton distribution. Counter anions are inhomogeneously distributed outside a relatively smooth edge of proton distribution. This is caused by the fact that acid generators can react with low-energy (∼0eV) electrons. The inhomodeneous distribution of counter anions outside proton distribution is considered to contribute to LER formation in chemically amplified resists for post optical lithographies.
Towards nano-fluidics by solvent deformation of electron beam resist
Authors: Pearson J. L. , Cumming D. R. S.
Published: January 2006

Improvements in the fabrication technology of planar micro- and nano-fluidic systems are continually being sought. In this work, we demonstrate and characterize a potential method for making planar nano-fluidic channels in cross-linked UV-3 resist using a single-step electron-beam lithography process. Earlier work indicated that the fluids used in the resist development process influenced the final form of the nano-fluidic structures. In this study the development, rinsing and drying conditions for the resist processing have been investigated in detail to find the best conditions for channel formation. The process was then exploited to construct more complex planar nano-fluidic features, including Y- and T-shaped junctions that are required for practical systems.
Ion emission measurements and mirror erosion studies for extreme ultraviolet lithography
Authors: Takenoshita K. , Koay C.-S. , George S. , Teerawattansook S. , Richardson M. , Bakshi V.
Published: January 2006

Mirror erosion by high energy ion emission from extreme UV light sources is one of the main factors contributing to EUVL collector mirror reflectivity degradation. We are measuring ion energy distributions at the mirror distance from the plasma utilizing three different ion diagnostics for the case of tin-doped microscopic droplet laser plasmas. Typical ion energy distributions measured by an electrostatic spectrometer are described. From the ion energy distributions, an estimate of mirror erosion is obtained. The effectiveness of electrostatic field mitigation is evaluated for the EUVL source requirement.
Ultrathin pore-seal film by plasma enhanced chemical vapor deposition SiCH from tetramethylsilane
Authors: Furuya Akira , Yoneda Katsumi , Soda Eiichi , Yoshie Toru , Okamura Hiroshi , Shimada Miyoko , Ohtsuka Nobuyuki , Ogawa Shinichi
Published: January 2006

One important issue for integrating atomic layer deposition (ALD) TaN on a template type porous low-k film is penetration of Ta precursor into the pores. Deposition of a thin film on a patterned sidewall by plasma enhanced chemical vapor deposition (PECVD) is a candidate for pore sealing. We have examined PECVD-SiCH from tetramethylsilane [Si(CH3)4:4MS] as a pore sealant and compared it to PECVD-SiOC from 4MS∕CO2 and SiO2 from tetraethoxysilane [Si(OC2H5)4:TEOS]. ALD-TaN had an incubation time on a blanket SiCH, while it did not on a SiCH patterned wafer. The SiCH had the lowest deposition rate and the highest step coverage which enabled deposition of an ultrathin pore-sealing film as thin as 2nm. Damascene Cu interconnects fabricated by using ALD-TaN barrier metal and the ultrathin SiCH pore-seal demonstrated good electrical characteristics which successfully presented the increase in leakage current due to metal penetration, and it minimized the increase in line resistance by keeping the sealing layer thin.
Ultraviolet-based nanoimprint at reduced environmental pressure
Authors: Fuchs A. , Bender M. , Plachetka U. , Hermanns U. , Kurz H.
Published: January 2006

The essential role of environmental pressure during ultraviolet-based nanoimprint is demonstrated for a series of relevant lithographic properties.
Filling high aspect-ratio nano-structures by atomic layer deposition and its applications in nano-optic devices and integrations
Authors: Wang Jian Jim , Deng Xuegong , Varghese Ron , Nikolov Anguel , Sciortino Paul , Liu Feng , Chen Lei , Liu Xiaoming
Published: January 2006

Atomic layer deposition, a highly uniform and conformal deposition process, was utilized to fill trenches of various high aspect-ratio nano-grating structures. Dielectric (e.g., SiO2), metal (e.g., aluminum), and dielectric/metal (e.g., Au∕SiO2) hybrid nano-gratings with a linewidth down to <50nm and an aspect ratio up to 14:1 (700nm:50nm) were trench-filled with various materials particularly nano-laminate materials such as TiO2∕SiO2 and SiO2∕Al2O3. Various high-performance optical devices such as true-zero-order optical retarders (i.e., wave plates) and nanowire-grid polarizers were realized based on an UV-nanoimprint lithography process and the atomic layer deposition for trench fillings. Thanks to both unique material properties and nano-structure trench filling capability, the atomic layer deposition opens a path for innovative nano-structure based optical devices and integrated optical devices.
Full three-dimensional characterization of 25nm lines for chemically amplified resist simulation
Authors: Landis S. , Pauliac S. , Foucher J. , Thiault J. , de Crecy F.
Published: January 2006

Low molecular weight negative tone chemically amplified resist has been exposed with 100kV electron beam writer with a postexposure bake temperature varying between 85 and 100°C. Isolated lines, with feature size ranging from 20 up to 100nm, have been characterized with scanning electron microscopy and critical dimension atomic force microscopy. A simple kinetic reaction law and lateral acid diffusion into the resist layer were taken into account for the cross-linking reaction simulation. Top view and full three-dimensional measurements of resist feature have been fitted with an analytical expression. A cost function was introduced to extract the reaction order (m) and the acid diffusion coefficient (D) of the second Fick’s law. Whatever the process temperature used, a constant value for m(m=2.6) was found, and D was found to vary from 2to45nm2∕s for a postexposure bake temperature of 85 and 100°C, respectively. Depending on the metrology technology used for resist characterization resist parameter extraction may be significantly impacted, especially for very narrow resist line simulation.
Mechanical characteristics and its annealing effect of diamondlike-carbon nanosprings fabricated by focused-ion-beam chemical vapor deposition
Authors: Nakamatsu Ken-ichiro , Nagase Masao , Igaki Jun-ya , Namatsu Hideo , Matsui Shinji
Published: January 2006

Our investigation of diamondlike-carbon (DLC) nanosprings with a 130-nm spring section diameter, which were fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD), showed for the first time that nanosprings can be stretched. We observed large displacements of the FIB-CVD nanosprings in situ optical microscopy; in other words, the nanosprings showed behavior similar to that of macroscale springs. In addition, we investigated the dependence of the spring constant of the DLC nanosprings on the spring diameter. The spring constants, measured using commercially available cantilevers, ranged from 0.47to0.07N∕m. The diameter dependence of the measured spring constant could be accurately expressed by the conventional formula for a coil spring. The estimated shear modulus of the DLC nanosprings was about 70GPa. This value is very close to the value of conventional coil springs made of steel. Furthermore, We measured the stiffness of the annealed nanospring at 1000°C in vacuum. The stiffness was decreased to approximately half compared to the stiffness of the spring without annealing.
Fabrication and surface chemistry of nanoscale bioarrays designed for the study of cytoskeletal protein binding interactions and their effect on cell motility
Authors: Cherniavskaya O. , Chen C. J. , Heller E. , Sun E. , Provezano J. , Kam L. , Hone J. , Sheetz M. P. , Wind S. J.
Published: January 2006

We have designed a system engineered to mimic biological spatial order. The system consists of nanoscale dots organized into hierarchical arrays in which structural parameters, such as spacing and orientation, are systematically varied. These arrays are used to probe the spatial distributions of binding sites in biomolecules. In this paper, we describe the fabrication process, including lithography and biofunctionalization, and we discuss issues related to surface chemistry that are critical to creating robust, biologically active nanoarrays.
Screening layouts for high-numerical aperture and polarization effects using pattern matching
Authors: McIntyre Gregory R. , Holwill Juliet , Neureuther Andrew , Capodieci Luigi , Zou Yi , Levinson Harry , Kye Jongwook
Published: January 2006

A pattern matching method for quickly estimating the extent to which high-NA and polarization vector effects reduce image quality in projection printing is derived and evaluated for prototypical layout patterns. The angular rotation of the in-incidence plane TM electric field component produces two unwanted effects. It reduces the collinear addition of electric fields at the location of the peak image intensity and, more importantly, it also introduces an electric field component perpendicular to the image plane that acts like stray light. While these imaging effects can be simulated rigorously, the challenge is to quickly screen an entire layout to identify the small subset of regions that must be analyzed more carefully. The approach developed mathematically and evaluated in this paper consists of finding a set of local theoretical patterns having the maximum lateral impact at a reference point. Pattern matching is then used to find areas in a layout that resemble these maximum lateral test functions by scanning them over the entire chip layout. Vulnerability scores, representing linear sensitivity to either high-NA effects or to perturbations of illumination polarization state, are determined for each location from a weighted combination of match factors (the degree of similarity to each pattern). These effects are important as intensity changes of over 40% and 10% can occur with NA and polarization, respectively, even in simple layouts.
Measuring line roughness through aerial image contrast variation using coherent extreme ultraviolet spatial filtering techniques
Authors: Shumway Michael D. , Naulleau Patrick , Goldberg Kenneth A. , Bokor Jeffrey
Published: January 2006

Line edge roughness properties for an extreme ultraviolet photoresist (Rohm and Haas/Shipley 1K) were investigated by varying the aerial image contrast of dense line and space patterns. Aerial image contrast variation was performed in single exposures by programming the modulation information on the mask. No background flood exposures were needed to reduce the contrast. The Micro Exposure Tool at Lawrence Berkeley National Laboratory was used for these experiments. Dense 50nm lines and spaces were printed with contrast levels ranging from 86.4% to 46.8%. Coherence was programmed to be 0.1 for these experiments. Results show that an increase in the aerial image contrast causes a subsequent decrease in the line edge roughness (LER). Similar effects are seen for linewidth roughness (LWR). The LER varied from 3.3nm (at 86.4% contrast) to 8.0nm (at 46.8% contrast). LWR varied from 5.3nm (at 86.4% contrast) to 12.8nm (at 46.8% contrast). All values are three sigma root-mean-square. Only a couple of dense 30nm features would print in this configuration. For these 30nm lines and spaces, the best LER was 5.6nm and LWR was 11.3nm.
Portable coordinate measuring tool
Authors: Jiang Li , Feldman M.
Published: January 2006

The ability to accurately measure the placement of features within a level is becoming increasingly critical in integrated circuit fabrication. In this article the level to be measured is patterned on a transparent wafer in poly(methylmethacrylate) (PMMA) resist to which a blue absorbing dye has been added. The dyed resist is on top of a thin partially transparent aluminum layer and is highly visible when viewed in reflected blue light in an oil immersion microscope. It is placed over a diffraction grating, which is not visible, both because the aluminum layer reflects most of the light and because the grating is far out of focus. In transmitted red laser light the grating can be seen, since various techniques may be used to increase the depth of focus of gratings in collimated monochromatic light. However, the resist pattern is not seen, because the resist is transparent to red light and the immersion oil matches its index of refraction. Measuring the separation between features reduces to measuring their location with respect to individual grating lines, and then counting the number of lines between them. The image placement accuracy of levels measured with two-dimensional gratings will be limited by the accuracy of the gratings—at present less than 2nm.
Extreme ultraviolet focus sensor design optimization
Authors: Goldberg Kenneth A. , Teyssier Maureen M. , Liddle J. Alexander
Published: January 2006

We describe performance modeling and design optimization of a prototype extreme ultraviolet (EUV) focus sensor (FS) designed for use with existing 0.3 numerical aperature (NA) EUV projection-lithography tools. At 0.3 NA and 13.5nm wavelength, the depth of focus at the resolution limit shrinks to 150nm increasing the importance of high-sensitivity focal-plane-detection tools. The FS is a free-standing Ni grating structure that works in concert with a simple mask pattern of regular lines and spaces at constant pitch. The FS pitch matches that of the image-plane aerial-image intensity: it transmits the light with high efficiency when the grating is aligned with the aerial image laterally and longitudinally. Using a single-element photodetector, to detect the transmitted flux, the FS is scanned laterally and longitudinally so the plane of peak aerial-image contrast can be found. The design under consideration has a fixed image-plane pitch of 80nm, with aperture widths of 12–40nm (1–3 wavelengths), and aspect ratios of 2–12. TEMPEST-3D is used to model the light transmission. Careful attention is paid to the annular, partially coherent, unpolarized illumination and to the annular pupil of the Micro-Exposure Tool optics for which the FS is designed. The system design balances the opposing needs of high sensitivity and high throughput optimizing the signal-to-noise ratio in the measured intensity contrast.
Simulation of the cathode surface damages in a HOPFED during ion bombardment
Authors: Zhao Hongping , Lei Wei , Zhang Xiaobing , Li Xiaohua , Wang Qilong
Published: January 2006

Most vacuum devices are hampered by ion bombardment due to residual gases. Sometimes, it causes the breakdown of devices and shortens their life. In this article, the effect of the ion bombardment on the cathode surface in a structure of a field emission display was simulated. In this structure, a special type of spacer was used, named “hop” and “flu” spacer. The trajectories of electrons emitted by a cold cathode were calculated under influence of an electric field. From these calculations, the ionization of a residual gas and the corresponding trajectories of the positive ions were estimated. In this article, we modeled Si microtip and Mo microtip field emitters. Because inert gases are not easily absorbed by the getter, several different types of residual gases, such as neon, argon, krypton, and xenon, were introduced in the simulation. The simulation results show that ion bombardment damages on a silicon target induced by Ar, Kr, and Xe are more destructive than Ne. Also, Ar, Kr, and Xe are shown to be more destructive than Ne to a molybdenum microtip. The results obtained in this article suggest damage on Si is larger than that on Mo under the same ion bombardment and that a molybdenum emitter is more stable than a silicon emitter in a nonideal vacuum environment.
Micromachined Arch-type cantilever as high sensitivity uncooled infrared detector
Authors: Ivanova K. , Ivanov Tzv. , Rangelow I. W.
Published: January 2006

In this article, we discuss an uncooled infrared (IR) detector based on an “arch-type” design realized with advanced microelectromechanical systems technology. Bimaterial microcantilevers undergo bending as their temperature changes due to the absorption of infrared photons. The bending is proportional to dissimilar thermal expansion of the two different materials composing the cantilever. We select the most optimal combination of materials used commonly in the micromachining technology resulting in highest bimaterial effect. Well known SU8 negative resist is one promising candidate having high thermal expansion coefficient (α=52×10−6∕K), and relatively low thermal conductivity (0.2W∕mK). Creating a micromechanical “arch” shaped cantilever a differential stress is induced due to different thermal expansion of middle beam formed from the SU8-film. Moreover, we fabricate a design microcantilever IR detector that consists two unique skills: (i) a Si/SU8 bimaterial system as material combination with beneficial bimaterial effect and (ii) tiny silicon “arch” shaped loop which includes two beams for piezoresistive detection of the bending.
Formation of GaN layer on SiN surface using low-energy Ga ion implantation
Authors: Yanagisawa Junichi , Toda Masaya , Kitamura Takeshi , Matsumoto Hiroyoshi , Akasaka Yoichi
Published: January 2006

As a new method for fabricating gallium nitride (GaN) layers at the outer surface of silicon nitride (SiN) films, low-energy Ga ion irradiation on SiN films was performed, and the composition of the surface and the chemical-bond nature of the irradiated surfaces were measured by x-ray photoelectron spectroscopy (XPS). The peak position of the XPS spectrum of Ga 3d from the Ga irradiated SiN was shifted from the value of the metallic Ga to that of GaN, indicating the formation of GaN on the Ga irradiated SiN surface. Formation of GaN was also confirmed from the XPS spectra of N 1s signals. It was also found that a Ga irradiation energy up to 4keV was useful to form GaN, and the implanted Ga atoms remained on the SiN surface as GaN after an annealing at 500°C for 5min under N2 gas pressure of 1×10−4Torr. Because GaN which was formed is positioned at the outermost region of the Ga irradiated SiN films, the possibility to use this surface as a substrate for the GaN growth is discussed.
Printability of nonsmoothed buried defects in extreme ultraviolet lithography mask blanks
Authors: Farys Vincent , Charpin-Nicolle Christelle , Richard Marieke , Robic Jean-Yves , Muffato Viviane , Quesnel Etienne , Postnikov Sergeï , Schiavone Patrick , Besacier Maxime , Smaali Rafik , Naulleau Patrick
Published: January 2006

One of the most important challenges in extreme ultraviolet lithography is the need to provide mask blanks free of defects. In order to provide experimental results on the printability of buried defects, a dedicated extreme ultraviolet (EUV) mask blank was manufactured using ion beam sputtering (IBS) with a nonsmoothing process. Using this kind of process, the effect of the buried defect is apparent throughout the entire multilayer stack. The disturbance generated in the multilayer, measured using an atomic force microscope (AFM), shows lateral growth and a slight vertical smoothing effect. Here we report the printability results obtained with this kind of defect. One result concerns the influence of the defect density on the printability. We show that the major effect can be attributed to local flare, which depends on the pattern density. In order to better understand the printability mechanism of this kind of buried defect, we also compared the experimental results with electromagnetic simulation.
Asymmetry of aerial image after mask pattern correction for off-axis incident light in extreme ultraviolet lithography
Authors: Sugawara Minoru , Nishiyama Iwao , Takai Mikio
Published: January 2006

In extreme-ultraviolet lithography (EUVL), asymmetry in printed images arises from the off-axis incidence of light illuminating the mask and from the thicknesses of the absorber and buffer layers of the mask. This study examined whether or not the asymmetry of printed images due to off-axis incidence affected pattern edge position error. The pattern edge position error and asymmetry of printed images were investigated using two types of patterns with a critical dimension (CD) of 44nm: nested lines, because they induce asymmetry in the printed image for off-axis incidence even though the mask layout is perfectly symmetrical and T-shaped patterns. The amount of pattern edge position error was found to be almost the same for off-axis and normal incidence, irrespective of the larger asymmetry in the printed image for off-axis incidence, even for thick absorber and buffer layers.
Electron-beam direct writing system employing character projection exposure with production dispatching rule
Authors: Tominaga T. , Nakamae K. , Matsuo T. , Fujioka H. , Nakasugi T. , Tawarayama K.
Published: January 2006

An electron-beam direct writing (EBDW) system with a character projection (CP) aperture is a promising candidate as an effective maskless lithography tool to realize a system on a chip fabrication process at low cost with quick turn-around time. We have proposed an approach to enhance the throughput of an EBDW system by using a production dispatching rule. Through an event-driven simulation analysis in the backend of the line, the effect of production dispatching rules on the throughput and the cost in an EBDW system is evaluated. We considered four kinds of dispatching rules, FIFO, APA, LWKR, and SLACK. FIFO is a usually used dispatching rule and gives the highest priority to the waiting lot that came in first at the EB lithography process. In APA, the highest priority is given to the waiting lot that does not require the CP aperture exchange. In LWKR, the highest priority is given to the waiting lot associated with the job having the least amount of total processing time remaining to be done. In SLACK, the highest priority is given to the waiting lot with the shortest slack. Simulated result shows that the EBDW system with APA enhances the throughput more than 1.2 times as compared to that with FIFO, LWKR, or SLACK, and has a throughput of 5wafers∕h or more. Furthermore, compared with the cost per chip for FIFO, the APA rule reduces the cost/chip by more than 30% at the cost minimum lot arrival rate point.
Advanced electron microscopy needs for nanotechnology and nanomanufacturing
Authors: Postek Michael T. , Villarrubia John S. , Vladár András E.
Published: January 2006

Advances in fundamental nanoscience, design of nanomaterials, and ultimately manufacturing of nanometer scale products all depend to some degree on the capability to accurately and reproducibly measure dimensions, properties, and performance characteristics at the nanoscale. Measurement tools and techniques are needed to image and measure in this realm of research, development, and technology. Currently available metrology tools are also beginning to reach the limits of resolution and accuracy and are not expected to meet future requirements for nanotechnology or nanomanufacturing. Clever approaches to this problem need to be developed. Further, even with the vast array of current tools available, the important question is whether or not they are providing the needed information. Revolutionary approaches to the metrology may be required in the near future. This article discusses some of the issues and potential solutions being undertaken in the scanning electron microscope dimensional metrology project at the National Institute of Standards and Technology.