bluuebunny/crossref_metadata_2025 huggingface dataset:
Graphitization of Fe-doped amorphous carbon pillars grown by focused-ion-beam-induced chemical-vapor deposition
Authors: Fujita J. , Ishida M. , Ichihashi T. , Ochiai Y. , Kaito T. , Matsui S.
Published: December 2002

Graphitization of amorphous carbon pillar grown by focused-ion-beam-induced chemical-vapor deposition was demonstrated using an iron catalyst. The graphitization was induced by iron particles at the top of the pillar that were locally doped. Such graphitization of amorphous carbon seems to be based on solid phase crystallization, where homo-epitaxial growth on a graphite template appeared to have occurred. The original three-dimensional shape of an as-grown structure survived solid phase graphitization at 820 °C.
Nanoscale electron beam lithography and etching for fully depleted silicon-on-insulator devices
Authors: Dreeskornfeld L. , Hartwich J. , Kretz J. , Risch L. , Roesner W. , Schmitt-Landsiedel D.
Published: December 2002

This article describes the process integration and optimization of nanoscale electron beam lithography and etching for the fabrication of fully depleted silicon-on-insulator devices with ultrathin bodies. For the fabrication, standard complementary metal–oxide–semiconductor (CMOS) production line processes with an optimized process flow were supplemented by advanced nanoscale patterning. The nanoscale processes have to fulfill several requirements, such as sub 20 nm exposure with small line edge roughness as well as sub 20 nm highly selective etching with vertical sidewalls. The development and optimization of these fully integrated CMOS processes, which require no additional shrinking step, is shown in this work. 18 nm wide features in calixarene negative tone resist and highly anisotropic etching of sub 30 nm structures with a selectivity to tetraethylorthosilicate of in excess of 300:1 are demonstrated.
Evaluation of the ion bombardment energy on silicon dioxide films deposited from O2/TEOS plasmas on Si and unstrained Si0.83Ge0.17/Si substrates
Authors: Goghero D. , Goullet A. , Lebrizoual L. , Meyer F. , Turban G.
Published: December 2002

Silicon dioxide films are deposited on Si and unstrained Si0.83Ge0.17 from O2/tetraethylorthosilicate plasmas in a helicon reactor operated at low pressure (2 mTorr). The effect of the negative dc self-bias voltage (0 to −200 V) on the film properties is investigated. X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry measurements have been performed on ultrathin (∼5 nm) films to gain better insight into the quality of the dielectric/semiconductor interface. We observed that the ion bombardment energy is responsible for the amorphization of the substrate, which is in agreement with the TRIM (transport and range of ions in matter) simulation results. In the case of SiGe samples, a GeO2 phase is detected in the XPS spectra which increases with the applied bias. Changes on the vibrational properties are observed on thick films (500 nm) while refractive index and p-etch measurements are only slightly sensitive to the voltage applied to the substrate. Complementary electrical measurements have been carried out on metal–oxide–semiconductor capacitors. For films deposited on Si substrates, C–V measurements indicated a degradation of the electrical properties with increasing energy of the impinging ions. The results obtained on SiGe samples exhibit typical negative fixed charges in the oxide with a rather low density of interface states (Dit∼5×1011 cm−2 eV−1).
Cryogenic cleavage used in gold substrate production
Authors: Mazurkiewicz Jakub , Mearns Freya J. , Losic Dusan , Weeks Laura , Waclawik Eric R. , Rogers Craig T. , Shapter Joseph G. , Gooding J. Justin
Published: December 2002

An improved method for the production of ultralarge flat and patterned gold surfaces for use in scanning probe studies using a procedure based on epitaxial gold growth on mica is described. The approach is superior in terms of simplicity and reliability without any loss of substrate quality. The gold surface is glued onto an aluminum stub with two part ceramic or polyester glue. The mica is removed by immersing the sample in liquid nitrogen. The liquid nitrogen causes differential contraction of the mica and gold resulting in clean separation to leave large atomically flat planes or patterned features.
Beam-focusing characteristics of the diamond-film field emission arrays with parallel emitter, gates, and in-plane lens
Authors: Zeng Baoqing , Liu Yang , Yang Zhonghai , Qian Shangjie , Yang Chongfeng
Published: December 2002

A focusing structure of field-emission arrays (FEAs) made of a parallel planar emitter, gate, and in-plane lens is suggested. Using the particle-in-cell simulation code MAGIC, the diamond-film FEAs made of a strip planar emitter, a parallel gate, and an anode with and without an in-plane lens have been simulated. The electron-beam streamlines and the x-py phase show that the in-plane lens focuses the electron beam. For a typical model, the beam width decreases about 1/10 for every cell, and the transverse velocity decreases from ±5.5×106 to ±0.4×106 m/s when including the in-plane lens. This structure can be used as a moderated field-emission cathode to emit a collimated electron beam, such as in field-emission displays.
Effects of Ar inductively coupled plasma exposure on 4H-SiC Schottky rectifiers
Authors: Ip K. , Nigam S. , Lee K. P. , Baik K. H. , Chung G. Y. , MacMillan M. F. , Ren F. , Pearton S. J.
Published: December 2002

4H-SiC Schottky rectifiers were exposed to inductively coupled Ar plasmas as a function of source power (150–750 W), rf chuck power (75–350 W), and process pressure (5–30 mTorr). The reverse breakdown voltage (VB) was increased by increases in both incident ion energy and ion flux, with the former having the strongest influence. As an example, Ar plasma exposure at ion energies of ∼335 eV led to an increase in VB from approximately −500 to −950 V. These results suggest strategies for minimizing plasma-induced damage during both deposition and etching steps used in the fabrication of SiC rectifiers.
Plasma assisted deposition of nanocrystalline BCN thin films and property characterization
Authors: Cao Z. X. , Liu L. M. , Oechsner H.
Published: December 2002

Electron-cyclotron-wave-resonance plasma assisted deposition is an effective technique for preparing superhard materials. In this work, nanocrystalline BCN thin films were grown on Si(001) wafers and Corning glass substrates, where the growing surface was bombarded with nitrogen plasma at energies between 60 and 180 eV. Energy-dispersive x-ray analysis revealed the formation of very clean, homogeneous films with a bulk composition around B42C33N25, which changes only slightly with ion energy. Under an atomic force microscope the films displayed a morphology composed of crystallites of about 200 nm in lateral size in cubic habits. Both the x-ray photoelectron spectroscopy and infrared absorption indicated that the deposits are ternary BCN compounds. The films are highly transparent and hard; the Vicker’s hardness scatters in the range of 26–28 GPa. Strong photoluminescence peaked at 430 nm was detected on the as-deposited specimens at room temperature. The band gap for the deposits was estimated to be circa 3.0 eV.
Investigations of pulse current electrodeposition for damascene copper metals
Authors: Chang Shih-Chieh , Shieh Jia-Min , Dai Bau-Tong , Feng Ming-Shiann
Published: December 2002

The influence of current density, duty cycle, and frequency of the applied pulse current on film qualities of electroplated copper was discussed. With various filled damascene structures, the corresponding filling power was optimized in a range of pulse current frequency. The optimized pulse current plating in conjunction with a leveler-free electrolyte resulted in a defect-free filling in approximate 100 nm damascenes and reduced the resistivity of Cu deposits.
Direct patterning of nanostructures by field-induced deposition from a scanning tunneling microscope tip
Authors: Houel A. , Tonneau D. , Bonnail N. , Dallaporta H. , Safarov V. I.
Published: December 2002

The process of local-field-induced deposition on a surface facing a scanning tunneling microscope (STM) tip has been investigated for several tip-sample systems. Applying negative voltage pulses, atoms can be transferred from the STM tip to the surface and, for example, platinum dots and lines have been drawn on gold or silicon samples by this technique. In this latter case, a discussion is proposed on growth mechanisms involved in field-induced deposition processes on the basis of growth kinetics studies. When positive voltage pulses are applied to a silicon sample placed in tunneling conditions with a STM tip, silicon nanofeatures are elaborated on the substrate surface by field-enhanced surface diffusion of silicon atoms.
Texture and resistivity of dilute binary Cu(Al), Cu(In), Cu(Ti), Cu(Nb), Cu(Ir), and Cu(W) alloy thin films
Authors: Gungor A. , Barmak K. , Rollett A. D. , Cabral C. , Harper J. M. E.
Published: December 2002

Annealing of dilute Cu(Al), Cu(In), Cu(Ti), Cu(Nb), Cu(Ir), and Cu(W) alloy films resulted in the lowest resistivity for Cu(Ti) and Cu(In) and the strongest 〈111〉 fiber texture also for Cu(Ti). Electron-beam evaporated films with compositions in the range of 2.0–4.2 at. % and thicknesses in the range of 420–560 nm were annealed at 400 °C for 5 h. Four-point probe resistance measurements, x-ray diffraction, Rutherford backscattering, and particle-induced x-ray emission were used to characterize the films and to follow the changes in film texture, phase constitution, and resistivity upon annealing. The behavior of the alloy films was compared and contrasted with that for a pure evaporated Cu film.
Assessment of extreme ultraviolet-induced charging of subtractive metal lithography masks
Authors: Klebanoff L. E. , Clift W. M. , Franco N. , Bostedt C. , Terminello L. J.
Published: December 2002

An assessment was made of the extent of charging induced in a patterned multilayer-based extreme ultraviolet (EUV) mask and a model mask structure by exposure to EUV radiation. An aluminum subtractive metal lithography mask, consisting of ∼1700 Å of Al spaced from underlying Mo/Si multilayer by ∼500–700 Å of SiO2, was taken as representative of subtractive metal masks in general. Photoelectron spectra measured from patterned and model mask Al samples during EUV exposures were compared with spectra from samples known not to be charging. These studies indicate that EUV-induced charging of the Al absorber layer in the subtractive metal masks is zero to within ∼0.4 V accuracy. We speculate that the mask does not charge up due to an increase in the electrical conduction of the SiO2 spacer layer upon EUV irradiation. Irradiation of the spacer will create large numbers of low-energy secondary electrons in the SiO2 conduction band, providing a conducting path from the Al absorber layer to the electrically grounded Mo/Si multilayer.
Electrical conductivity of sidewall-deposited fluorocarbon polymer in SiO2 etching processes
Authors: Shimmura T. , Soda S. , Samukawa S. , Koyanagi M. , Hane K.
Published: December 2002

High-aspect-ratio SiO2 contact hole etching is one of the key processes in the fabrication of ultralarge scale integration devices. However, there are many serious problems, such as charge-build-up damage, etching-stop, and microloading effects. Charge accumulation in high-aspect-ratio contact holes during etching is one of the main causes of these problems. In SiO2 etching using fluorocarbon gases, it is well known that a fluorocarbon film is deposited on the underlayer surface and sidewall of contact holes. It is also predicted that an increase in the conductivity of the fluorocarbon film deposited on the SiO2 sidewall markedly reduces the charging potential in the high-aspect-ratio contact holes because of the high conductivity of the deposited polymer. To clarify these phenomena, it is necessary to obtain quantitative measurements of the conductivity of the sidewall surfaces in contact holes. Therefore, we fabricated the sensing device using semiconductor production technology, and monitored sidewall current of SiO2 contact holes on the silicon wafer. The relationship between the chemical structure and sidewall current of the fluorocarbon films deposited in contact holes is investigated. We have found that highly cross-linked and unsaturated fluorocarbon polymer causes high sidewall conductivity in SiO2 contact holes. It is suggested that the deposited fluorocarbon film reduces the charging potential during the SiO2 etching process.
Effects of Ti addition on the morphology, interfacial reaction, and diffusion of Cu on SiO2
Authors: Liu C. J. , Jeng J. S. , Chen J. S. , Lin Y. K.
Published: December 2002

In this work, thin films of pure Cu, and Cu with 0.02 or 2.98 wt % Ti were deposited on SiO2 covered Si substrates. The samples were annealed at 500–800 °C in vacuum to investigate their morphological evolution, interfacial reaction, and diffusion. X-ray diffraction reveals Cu(111) and Cu(200) peaks for pure Cu and Cu(0.02 wt % Ti) films. However, the Cu(2.98 wt % Ti) film exhibits a very weak Cu(200) peak, indicating that this film is textured in 〈111〉 orientation. Concurrently, scanning electron microscopy shows that the grain size of the Cu(2.98 wt % Ti) film is significantly smaller than those of pure Cu and Cu(0.02 wt % Ti) films. In addition, Cu(2.98 wt % Ti) film remains smooth after annealing up to 800 °C, while the other two films become discontinuous. X-ray photoelectron spectroscopy indicates that a TiOx layer has formed at the Cu(0.02 wt % Ti)/SiO2 and Cu(2.98 wt % Ti)/SiO2 interfaces after 700 °C annealing. Nevertheless, the TiOx layer is thicker in the Cu(2.98 wt % Ti) system than in the Cu(0.02 wt % Ti) system. Consequently, the Cu(2.98 wt % Ti) film shows no diffusion of Cu into SiO2 at temperatures up to 700 °C. Connections between the segregation of Ti addition and the morphological/interfacial characteristics are discussed.
Direct printing of polymer microstructures on flat and spherical surfaces using a letterpress technique
Authors: Miller Scott M. , Troian Sandra M. , Wagner Sigurd
Published: December 2002

We have developed a letterpress technique capable of printing polymer films with micrometer scale feature sizes onto flat or spherically shaped nonporous substrates. This printing technique deposits polymer only in desired regions thereby eliminating subsequent developing and subtraction steps. Flat or curved printing plates, which are fabricated from either rigid or deformable materials, are used to transfer thin molten polymer films onto flat target substrates. By deforming the printing plates into a spherical shape, it is also possible to print patterned films onto the concave side of a spherically deformed target substrate. These printed films serve as good resists for both wet chemical etching and reactive ion etching. Interferometric measurements of the polymer film thickness are used to probe physical mechanisms affecting printing instabilities, pattern fidelity, and edge resolution. Our experimental study indicates that this letterpress technique may prove suitable for high-throughput device fabrication involving large-area microelectronics.
Thickness metrology and end point control in W chemical vapor deposition process from SiH4/WF6 using in situ mass spectrometry
Authors: Xu Y. , Gougousi T. , Henn-Lecordier L. , Liu Y. , Cho S. , Rubloff G. W.
Published: December 2002

Real-time, in situ chemical sensing has been applied to achieve reaction metrology and advanced process control in a low pressure tungsten chemical vapor deposition process based on WF6 and SiH4 reactants (silane reduction process). Using mass spectrometry as the sensor to detect both product generation (H2) and reactant depletion (SiH4) at wafer temperature of 200–250 °C, these signals provided a direct real-time measurement of deposited film thickness with an uncertainty less than 2%, and this thickness metrology signal was employed to achieve real-time process end point control. When reactant conversion rates are sufficient (∼20% in this case) as often occurs in manufacturing processes, the thickness metrology (1.0%–1.5%) and control (∼1.5%–2.0%) accuracies are in the regime needed for meaningful application of advanced process control. Since the in situ sensor delivers a metrology signal in real time, real-time process control is achieved, enabling compensation for random process disturbances during an individual process cycle as well as for systematic wafer-to-wafer process drifts. These results are promising for manufacturing from the standpoints of metrology accuracy and application in real-time control.
Characteristics of ultrathin Ta and TaN films
Authors: Rossnagel S. M.
Published: December 2002

The electrical resistivity of thin films of Ta and TaN has been examined as a function of film thickness and other processing parameters. The films were deposited by magnetron sputtering of Ta cathodes with Ar, or mixtures of Ar and N2 for the case of TaN. Ta films deposited on silicon dioxide or Cu surfaces were always beta phase, and showed little resistance increase as the thickness was reduced. The TaN films were deposited in a broad range of compositions, depending on reactive gas flow and system configuration, and showed strong increases in resistivity as thickness was decreased. Ta films deposited on TaNx with x equal to or greater than 1, an electrical resistivity greater than 300 mΩ cm, and with thickness greater than 2 nm were alpha phase, and showed significant increases in resistivity as thickness was reduced. The application and electrical properties of these films as diffusion barriers in interconnect structures depends strongly on the thicknesses at the contact points at the bottoms of vias and only weakly on the phase of the Ta. The resistivity of the barrier films on via and trench sidewalls is high enough to be irrelevant to circuit performance.
Structure and size distribution of TiO2 nanoparticles deposited on stainless steel mesh
Authors: Li W. , Shah S. Ismat , Sung M. , Huang C.-P.
Published: December 2002

Doped and undoped TiO2 nanoparticles with narrow size distribution were deposited on stainless steel mesh substrates by metalorganic chemical vapor deposition. The chemical composition of TiO2 nanoparticles was measured by energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy. X-ray diffraction and transmission electron microscopy were performed to investigate the size and the size distribution of particles as well as the structural phase transitions. For pure TiO2, the results showed that anatase polycrystalline nanoparticles with average size from 23 to 31 nm were obtained for substrate temperatures between 350 and 600 °C. Particles deposited below 350 °C were x-ray amorphous and rutile began to precipitate at temperatures above 700 °C. The particles synthesized at 600 °C had the smallest size and narrowest size distribution. In order to study the dopant effects on the photocatalytic properties, growth temperature of 600 °C was selected to prepare 1 at. % Nd3+ doped TiO2 nanoparticles. The results of photodegradation of the pollutant 2-chlorophenol solution irradiated under ultraviolet light showed that 1 at. % of Nd3+ doped TiO2 had an enhanced degradation of the pollutant. The enhancement of photocatalytic efficiency by doped nanoparticles was ascribed to the large surface area and trapping induced prolonged lifetime of holes.
Surface diffusion and size evolution of nanostructures in laser-focused atomic deposition
Authors: Zhong Jianxin , Wells Jack C. , Braiman Yehuda
Published: December 2002

We examine the effect of adatom diffusion on the size broadening of nanostructures in laser-focused deposition by considering two major diffusion processes, namely, terrace diffusion and step-edge descending. We find that adatom diffusion sets a limit of the structure size no matter how well focused the atomic beam. A criterion is derived from rate-equation analysis to predict the limiting size of the structure, which is further confirmed by kinetic Monte Carlo simulations. The criterion suggests that, for a given growth system, the structure feature size can be minimized by increasing deposition flux rate or by decreasing growth temperature. Applications of the criterion to existing experiments are also discussed.
Digital electrostatic electron-beam array lithography
Authors: Baylor L. R. , Lowndes D. H. , Simpson M. L. , Thomas C. E. , Guillorn M. A. , Merkulov V. I. , Whealton J. H. , Ellis E. D. , Hensley D. K. , Melechko A. V.
Published: December 2002

A concept for maskless digital electrostatically focused e-beam array direct-write lithography (DEAL) has been developed at Oak Ridge National Laboratory. This concept incorporates a digitally addressable field-emission array (DAFEA) integrated into a logic and control circuit implemented as an integrated circuit. The design goal is for 3 000 000 individually addressable field-emission cathodes with a 4 μm by 8 μm pitch on a single ∼1 cm2 integrated circuit. The DAFEA design includes built-in electrostatic focusing for each emitter with feedback dose-control circuits to drive each emitter for tightly controlled electron delivery. With the electrostatic focusing, an array of ∼460 of these integrated circuits (up to 30 across by ∼23 rows deep) are suspended on a back plane ∼100 μm above a 300 mm semiconductor wafer. This arrangement could lithographically expose an entire 300 mm wafer, with 30 nm pixels, in less than 45 s, with every wafer pixel redundantly illuminated eight times allowing gray-scale edge placement. Only ∼1.5 cm of wafer motion is required for complete wafer exposure. High-speed data paths are proposed to program the patterns into the DAFEA to be written to the wafer. The DEAL concept thus requires no mask and can be extended to the 10 nm linewidth regime.
Efficient phase defect modeling using domain decomposition methods
Authors: Adam Konstantinos , Neureuther Andrew R.
Published: December 2002

The domain decomposition method is adapted for the simulation of alternating phase shifting masks that bear phase defects. The scattered signal from a defective mask layout is approximated by the sum of the defect-free signal and a perturbation signal that results from a rigorous electromagnetic simulation of an isolated defect. The perturbation signals are generated off-line by creating a database of scattered electromagnetic fields from various relevant phase defects. Comparison of images of defective masks resulting from the adapted domain decomposition method and from rigorous mask simulations of the complete defective masks show that the normalized mean square error of the method is less than 0.3%.
Maskless lithography using low-energy electron beam: Recent results for proof-of-concept system
Authors: Nakasugi T. , Ando A. , Inanami R. , Sasaki N. , Ota T. , Nagano O. , Yamazaki Y. , Sugihara K. , Mori I. , Miyoshi M. , Okumura K. , Fujioka H.
Published: December 2002

In order to realize a system on a chip fabrication at low cost with quick turn-around-time, we have proposed a maskless lithography strategy, a low-energy electron-beam direct writing (LEEBDW) system with a common character projection (CP) aperture. This article presents a status report on our proof-of-concept (POC) system. We have developed a compact EB column consisting of small electrostatic lenses and deflectors. The experimental results for our POC system indicated that the patterns corresponding to 50-nm-node logic devices can be obtained with CP exposure at the incident energy of 5 keV. The technique to reduce the raw process time using a scanning electron microscope function of LEEBDW system is also reported.
Generalized scanning beam interference lithography system for patterning gratings with variable period progressions
Authors: Pati G. S. , Heilmann R. K. , Konkola P. T. , Joo C. , Chen C. G. , Murphy E. , Schattenburg M. L.
Published: December 2002

We demonstrate a versatile interference lithography system that can continuously vary the pattern period and orientation during fabrication of general periodic structures in one or two dimensions. Initial experimental results, using closed-loop beam steering control and double exposures on a stationary substrate, are obtained in order to illustrate its principle of operation. A fringe-locking scheme for phase control is also demonstrated including discussion of issues related to future system developments.
Suppression of secondary electron blur by using Br-containing resists in x-ray lithography
Authors: Kise K. , Marumoto K. , Watanabe H. , Itoga K. , Kumada T. , Sumitani H. , Kitayama T. , Amemiya M. , Watanabe Y. , Uda K.
Published: December 2002

Second generation proximity x-ray lithography (PXL-II), which uses shorter incident x-ray wavelengths and resist materials, is expected to be a candidate for next generation lithography. In the PXL-II technique, the x-ray wavelength absorbed in the resist becomes shorter, but degradation of the pattern quality due to secondary electron blur has not been sufficiently evaluated. In this article, we present our investigation of the secondary electron blur’s suppression in Br-containing resist using a lithographic simulator and a Monte Carlo simulator for electron scattering. By introducing the Br element into resist materials, the electron stopping power improves. In addition, secondary electron blur is suppressed in regions with wavelengths shorter than that of the Br absorption edge. In order to evaluate pattern resolution, the image contrast of the lateral absorbed image in the resist is defined. We found that image contrast is improved in Br-containing resist for the wavelength range down to about 4.5 Å, which is suitable for PXL-II. We also show that it should be possible to extend PXL-II for resolutions of less than 40 nm at a narrower gap.
Optical imaging properties of dense phase shift feature patterns
Authors: Fritze M. , Tyrrell B. , Mallen R. , Wheeler B. , Rhyins P. , Martin P.
Published: December 2002

Optical lithography resolution enhancement methods are continuing to develop, driven by the semiconductor industry’s requirements for imaging subwavelength feature sizes. In the phase shift area, pattern decomposition into multiple exposures has been found to be useful and is finding its way into production. Recently, layout construction based on dense fine-pattern imaging has received increasing interest. This type of approach can minimize the proximity and other spatial frequency effects that otherwise limit strong phase shift technologies. Simple fine-feature template masks are easier and cheaper to fabricate and inspect as well as offering the potential to be reused for multiple designs. In this article, imaging and process issues specific to dense phase shift patterns are explored both experimentally and through simulation. Progress is reported in applying our gratings of regular arrays and trim exposures for ultralarge scale integrated circuit lithography (GRATEFUL) imaging method to fine features in both x and y orientations. The use of a graytone trim mask to vary fine-feature dimensions in a dual-exposure, strong phase shift process has been explored. We have also studied multiple-exposure lithography using one mask and varying illumination between exposures.
Characteristics of multiwalled carbon nanotube nanobridges fabricated by poly(methylmethacrylate) suspended dispersion
Authors: Lee S.-B. , Teo K. B. K. , Robinson L. A. W. , Teh A. S. , Chhowalla M. , Hasko D. G. , Amaratunga G. A. J. , Milne W. I. , Ahmed H.
Published: December 2002

We report on the transport characteristics of individual multiwalled carbon nanotube/nanofibers (MWCNTs) grown by plasma-enhanced chemical vapor deposition (PECVD). The measurements were performed on individual MWCNT nanobridges suspended by sputtered Nb contacts. Temperature dependent measurements of conductance revealed that the conductance is dominated by a contribution from thermally activated carriers. High-field measurements show that the PECVD grown MWCNTs are able to carry high current densities (∼108 A/cm2) and after reaching a critical limit, break down in segments of nanotube shells while still being electrically stable. The high-density current transport and reliability make PECVD grown MWCNTs good candidates for applications as field emission cathodes and nanoelectronic interconnects.
Dynamic studies of hard pellicle response during exposure scanning
Authors: Cotte Eric P. , Abdo Amr Y. , Engelstad Roxann L. , Lovell Edward G.
Published: December 2002

Meeting the stringent image placement error budgets for 157 nm lithography in the sub-90 nm regime requires that mask-related distortions be minimized, corrected, or possibly eliminated. One of the sources of image placement error is the pellicle system. Static pellicle-induced distortions have previously been characterized, both experimentally and numerically. This article focuses on the dynamic response of modified fused silica (hard) pellicles during exposure scanning and takes into account inertia effects as well as fluid/structure interactions. Parametric studies were performed to identify conditions causing the pellicle behavior to become dynamic. Distortions of the 800-μm-thick hard pellicle for different acceleration pulse widths were assessed, both numerically and analytically, and the agreement was excellent. The results presented here will facilitate the establishment of pellicle standards for 157 nm lithography.
Prototype raster multibeam lithography tool
Authors: Coyle S. T. , Holmgren D. , Chen X. , Thomas T. , Sagle A. , Maldonado J. , Shamoun B. , Allen P. , Gesley M.
Published: December 2002

A prototype raster multibeam lithography tool was constructed and is being evaluated for use as a mask writer at the 50 nm node. The photocathode illumination module (PIM) focuses a linear brush of 32 individually modulated laser beams into 300 nm full width at half maximum spots on the surface of a photocathode. The PIM has been module tested with satisfactory results and integrated into the prototype tool. A new electron-beam photocathode gun and column have also been integrated into the tool. The tool has generated a linear array of 32 electron beams which have been magnified and focused onto a YAG screen as well as demagnified and scanned across a knife edge. Preliminary results have produced 86 nm spots at the writing plane.
Characterization of and imprint results using indium tin oxide-based step and flash imprint lithography templates
Authors: Dauksher W. J. , Nordquist K. J. , Mancini D. P. , Resnick D. J. , Baker J. H. , Hooper A. E. , Talin A. A. , Bailey T. C. , Lemonds A. M. , Sreenivasan S. V. , Ekerdt J. G. , Willson C. G.
Published: December 2002

As compared to quartz relief structures currently employed, indium tin oxide-based (ITO-based) step and flash imprint lithography templates offer advantages in terms of electron-beam writing, scanning electron microscope inspection, and pattern transfer. The material properties of the ITO have been completely characterized, and data is presented for resistivity, crystal structure, transmission, stress, surface roughness, adhesion, composition, and etch characteristics. For a 600 Å annealed ITO film, the resistivity is approximately 3.5×102 Ω/sq and the optical transmission 77% at 365 nm. The atomic film composition was found to be 31.5% In, 4.3% Sn, and 64.2% O by x-ray photoelectron spectroscopy. When contrasted with SiO2 films, temperature programmed desorption data suggests that hydroxyl groups on the ITO surface bind H2O less strongly but are more abundant. Ultimate verification of compatibility was obtained by imprinting features into an etch barrier layer using an ITO-based template. The fidelity of 20 nm isolated and semi-isolated features, the smallest features present on the template, was successfully reproduced via the imprinting process.
Electron projection lithography tool development status
Authors: Miura Takaharu
Published: December 2002

In the development of an electron beam projection lithography (EPL) tool, the most important tasks are to develop the high-speed vacuum stage system, reliable vacuum body system, and total control system. Nikon has a long history of over 22 years in precision stage development for its optical lithography tools as well as over 10 years in electron beam (EB) instrument development such as the EB 60 with NTT. Recently, optical lithography stages have been developed based on air bearing and linear motor technologies. It is desirable and of minimum risk to utilize those technologies for the EPL system in order to shorten the total time period of development, but the requirements for the EB stage, body, and system control are much different from their optical counterparts and much more difficult. In this article development and implementation of the EPL vacuum stage system, vacuum body system, vacuum loader system, and control system are discussed and overviewed.
Morphology and luminescence of porous GaN generated via Pt-assisted electroless etching
Authors: Dı́az Diego J. , Williamson Todd L. , Adesida Ilesanmi , Bohn Paul W. , Molnar Richard J.
Published: December 2002

Porous gallium nitride (PGaN) is produced by Pt-assisted electroless etching of GaN. Ultrathin Pt films are sputtered onto the surface of GaN, and etching is carried out in a 1:2:1 or 1:2:2 solution of CH3OH:HF:H2O2. Etching proceeds by first forming a network of small pores, after which ridge structures form, with the porous network in trenches between the ridges. As the etch progresses further the sidewalls of the ridges become steeper, and then the ridges start to disappear. Cathodoluminescence (CL) spectroscopy and imaging show the ridges to be optically inactive, suggesting that the ridges might arise from grain boundaries or dislocations present ins the starting GaN material. CL emission is confined to the porous areas between the ridges. CL properties of the PGaN vary depending on the source of the original, nonporous GaN material. Undoped and unintentionally doped hydride vapor phase epitaxy materials produce PGaN which shows only band gap emission at 368 nm before and after etching, whereas PGaN produced from the Si-doped metalorganic chemical vapor deposited material exhibits two blueshifted luminescence bands at 358 and 326 nm. The origin of the 358 nm blueshifted emission can plausibly be explained by quantum confinement effects, but the 326 nm band can only be explained by other mechanisms, such as the creation of specific surface states by etching. The etched morphology is very similar among the different types of GaN substrates used, however the difference in light emission properties must be ascribed to growth conditions, or to the nature and concentration of the dopants.
Polymer microring resonators fabricated by nanoimprint technique
Authors: Chao Chung-yen , Guo L. Jay
Published: December 2002

Microring optical resonators have important applications in integrated photonic circuits for optical communications. We have developed two methods to fabricate polymer microring devices based on the nanoimprint technique. The first method uses a hard mold to directly imprint a polymer film to form optical waveguides in microring devices. We have demonstrated polymethylmethacrylate, polystyrene, and polycarbonate microring resonators fabricated using this technique. The second method employs a template filling approach, which allows a thicker waveguide to be fabricated, as well as polymers that are difficult to directly imprint. Optical filtering behavior of a microring resonator is demonstrated with a Q factor as high as 5800. The technique developed in this work could offer a cost-effective method to fabricate integrated photonic circuits based on polymer microring resonators.
Process integration of self-assembled polymer templates into silicon nanofabrication
Authors: Guarini K. W. , Black C. T. , Zhang Y. , Kim H. , Sikorski E. M. , Babich I. V.
Published: December 2002

Self-assembled diblock copolymer thin films are used as sacrificial layers for the transfer of dense nanoscale patterns into more robust materials. We detail the processes used to achieve highly uniform nanoporous dielectric films, high-aspect-ratio nanotextured silicon, silicon nitride dot arrays, silicon pillar arrays, and silicon tip arrays. All techniques are compatible with standard semiconductor fabrication processes. We also discuss the possible applications of each resulting nanometer-scale structure, including high surface area substrates for capacitors and biochips, quantum dot arrays for nonvolatile memories, and silicon pillar arrays for vertical transistors or field-emission displays.
Fabrication and electrical characterization of top gate single-wall carbon nanotube field-effect transistors
Authors: Wind S. J. , Appenzeller J. , Martel R. , Derycke V. , Avouris P.
Published: December 2002

We describe the fabrication of single-wall carbon nanotube field-effect transistors in a conventional metal–oxide–semiconductor field-effect transistor structure, with gate electrodes above the conduction channel separated from the channel by a thin dielectric. We use these devices to study the performance improvements achieved by reducing the gate-to-channel separation. The top gate structure offers certain structural advantages over earlier, back gated carbon nanotube devices. In addition, these devices exhibit excellent electrical characteristics, including steep subthreshold slope and high transconductance, at gate voltages close to 1 V. The measured device characteristics are significantly better than previously reported carbon nanotube devices, providing further motivation to explore the use of carbon nanotubes for future nanoelectronic applications.
Electron projection lithography mask format layer stress measurement and simulation of pattern transfer distortion
Authors: Reu P. L. , Chen C.-F. , Engelstad R. L. , Lovell E. G. , Bayer T. , Greschner J. , Kalt S. , Weiss H. , Wood O. R. , Mackay R. S.
Published: December 2002

Electron projection lithography (EPL) is one of the leading candidates for the sub-65 nm lithography node. The development of a low-distortion mask is critical to the success of EPL. This article proposes and analyzes two new EPL mask formats described as a “corrugated-continuous membrane mask” and a “carbon-continuous membrane mask.” Novel process flows for the manufacture of these masks have been developed at Team Nanotec GmbH. Resonant frequency stress measurements of the ultrathin membrane bilayers were completed and subsequently used in the finite element simulation of the mask fabrication and pattern transfer. The new mask types have the benefits of the lower distortions of a typical continuous membrane mask, but maintain the advantage of the higher throughput stencil format because of the ultrathin films. In addition, the proposed masks remove the need for pattern splitting typically used with complementary systems.
Collimated point-source x-ray nanolithography
Authors: Forber R. A. , Chen Z. W. , Menon R. , Grygier R. , Mrowka S. , Turcu I. C. E. , Gaeta C. J. , Cassidy K. , Smith Henry I.
Published: December 2002

The most efficient use of radiation point sources for x-ray lithography requires a collimator to capture a large fraction of spherically emitted radiation and deliver the rays with acceptable divergence properties. We describe an x-ray point source utilizing a polycapillary collimator. The optical performance of the collimator was measured and is described. Dense line-space patterns (∼100 nm lines) were printed in poly(methylmethacrylate) using a mask-wafer gap of 16 μm. Lithography results are consistent with modeling analysis.
Stencil reticle inspection using a deep ultraviolet microscope
Authors: Okada Masashi , Katakura Norihiro , Kawata Shintaro
Published: December 2002

A reticle inspection is one of the important issues in next-generation lithography systems. In this article, a feasibility of a deep ultraviolet (DUV) microscope is described for an inspection tool of a stencil-type reticle for an electron-beam stepper. The resolution and contrast of the DUV microscope are superior to those of the conventional optical microscope using a visible light illumination. Moreover, the DUV image clearly shows particulate contaminations inside the line pattern of the stencil reticle. Although simulation results show that the transmission image of the contact hole pattern is low contrast compared to that of the line pattern, it is possible to improve the visibility of the contact hole pattern.
Copper device editing: Strategy for focused ion beam milling of copper
Authors: Casey J. David , Phaneuf Michael , Chandler Clive , Megorden Michael , Noll Kathryn E. , Schuman Richard , Gannon Thomas J. , Krechmer Alex , Monforte David , Antoniou Nicholas , Bassom Neil , Li Jian , Carleson Peter , Huynh Chuong
Published: December 2002

Focused ion beam (FIB) methodologies for successfully milling copper (U.S. Patent No. 6,322,672 B1) have been demonstrated. Approaches to milling copper (Cu) are required because standard FIB mill procedures produce rough, uneven cuts that are unsuitable for circuit edits, a principal FIB function. Efforts to develop gas assisted etching (GAE) processes which would smoothly mill Cu failed because Cu halides are not volatile and remain on the substrate as corrosive electrically conductive debris. Single crystal studies show that Cu grains with different crystal orientations vary in mill rate by as much as 4×. Moreover, the (110) crystal orientation, which mills most slowly, forms a Cu3Ga phase when milled with a focused Ga ion beam. This phase is particularly resistant to milling and, in polycrystalline Cu, propagates during the milling operation, contributing to the uneven trench profiles. CoppeRx, a novel scan strategy, cleanly and uniformly removes polycrystalline Cu with minimal damage to the underlying dielectric. CoppeRx minimizes the formation and propagation of the Cu3Ga phase and equalizes the etch rates of the Cu crystal orientations. The CoppeRx strategy includes the milling of an “egg crate” topography to minimize the propagation of the Cu3Ga phase and the creation of a heavy atom sacrificial layer of the Cu surface (U.S. Patent Application No. 20010053605) which scatters the incident Ga ion beam, thereby reducing the channeling influence on Cu milling rates. This heavy atom layer is created by flowing W(CO)6 vapor during the FIB milling process. The CoppeRx scan strategy is especially beneficial for milling thick (>0.8 μm) Cu structures with large, prominent grains. Because Cu interconnect lines are relatively thin (<0.4–0.5 μm), grain-related milling roughness is less of a problem. The CoppeRx egg crate topography and W scattering layer are not required. Instead, the successful cutting of 40 ohm Cu interconnect lines to produce >20 M ohm open circuits is achieved by flowing O2 or H2O during the milling process (U.S. Patent No. 6,322,672B1). The O2/H2O flow smoothes the Cu milling by producing an amorphous surface oxide, thereby reducing channeling, and by enhancing the etch selectivity for Cu relative to the surrounding and underlying SiO2 based dielectric. These interconnect cuts have been routinely done at the bottom of high aspect ratio holes (e.g., 1×1×9 μm).
Development of a mask-scan electron beam mask writer
Authors: Nishimura Shinsuke , Shimizu Mitsuko , Mitsui Soichiro , Akeno Kiminobu , Kusakabe Hideo , Ogasawara Munehiro , Hayashi Ryuji , Yanaga Shinji , Kobayashi Noboru , Tojo Toru
Published: December 2002

Mask-scan strategy for writing large complex patterns such as oblique lines and contact holes with assist bar and serif is more effective for decreasing the number of shots than is variable shaped beam (VSB) strategy and character projection strategy. In a simple case, the number of shots for writing the oblique lines can be as small as 1/600 of that of VSB strategy. Oblique parallel lines of 250 nm width and assist bar of 120 nm width were projected using the mask-scan strategy.
Photopatternable sol-gel for compound semiconductor processing
Authors: Fallahi Mahmoud , Bedford Robert , Lu Dong
Published: December 2002

A simple technique using hybrid organic–inorganic sol-gel films for compound semiconductor processing is proposed and demonstrated. The dual organic and inorganic nature of the hybrid sol-gel films allows high quality photopatternability and robust masking for the dry-etching process. The sol-gel channels on GaAs and InP are fabricated and high-aspect-ratio dry etching of semiconductors is shown. In addition, the potential of the hybrid sol-gel as a planarizing layer on deep-etched InP with overcut and undercut profiles is demonstrated.
Role of oxygen in semiconductor negative electron affinity photocathodes
Authors: Machuca Francisco , Liu Zhi , Sun Yun , Pianetta P. , Spicer W. E. , Pease R. F. W.
Published: December 2002

Source contamination, photovoltage effects, and stimulated electron desorption of cesium are factors that determine the initial high performance and longevity of negative electron affinity electron sources. As part of the study of these factors, we investigate the effect of oxygen contamination during the activation process and operation of a traditional GaAs (100) and a novel GaN (0001) emitter. We use synchrotron radiation photoemission spectroscopy, a focused mercury arc discharge lamp, and a helium neon (HeNe) laser to obtain simultaneously elemental analyses of the emitting surface and the corresponding total quantum yield at various stages, respectively, for GaN and GaAs. Our results indicate: (1) carbon uptake does not occur in our carbon free system over time, (2) oxygen uptake is observed for both GaN (0001) and GaAs (100) activated surfaces, a property common to the chemistry of the Cs/O adlayer, (3) the oxygen species appears to change over time and the initial species is assigned to an ion of nondissociated oxygen in the Cs/O activation layer, (4) the chemical changes of the Cs/O adlayer are not accompanied by a significant loss of cesium from the surface, and (5) the onset of decay of the quantum yield begins at a later time for the GaN (0001) emitter in comparison to the GaAs (100) electron source. A chemical model for the activation layer and its transformation over time is developed, consistent with points (1) through (4) in a separate report [F. Machuca et al. (unpublished)]. The complete account of the decay of the quantum yield of both Cs/O activated III–V emitters is compared and discussed in this article.
Prediction of fabrication distortions in step and flash imprint lithography templates
Authors: Martin C. J. , Engelstad R. L. , Lovell E. G. , Resnick D. J. , Weisbrod E. J.
Published: December 2002

Step and flash imprint lithography (SFIL) is an alternative approach for printing sub-100 nm features that relies on chemical and mechanical techniques to transfer patterns. The imprint process requires no projection optics and is performed at room temperature with low imprint pressures to reduce thermal and mechanical template distortions. Because imprint lithographies are 1× pattern transfer processes that preclude magnification corrections, the minimization of template distortions during fabrication and imprinting is critical. The processes and materials used in the fabrication of SFIL templates are similar to those used in the manufacturing of optical masks. The various process steps have been simulated using finite element techniques in order to predict the resulting pattern distortions. Two proposed template fabrication schemes were modeled, the resulting pattern distortions compared, and the error sources were quantified.
Proximity and heating effects during electron-beam patterning of ultraviolet lithography masks
Authors: Lu B. , Wasson J. R. , Weisbrod E. J. , Masnyj Z. , Mangat P. J. S. , Nordquist K. , Resnick D.
Published: December 2002

Proximity effects and resist heating during high energy electron-beam (e-beam) patterning of extreme ultraviolet lithography (EUVL) mask were investigated for the 50 nm node and beyond. These effects were observed experimentally on both silicon wafers and standard 6025 photomasks coated with two different EUVL absorber stacks. Monte Carlo and resist simulations were used for proximity effect correction and resist heating effect verification. The estimated temperature change during electron-beam writing was also attempted using the finite element method.