bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoscale patterning of an organosilane monolayer on the basis of tip-induced electrochemistry in atomic force microscopy
Authors: Sugimura Hiroyuki , Okiguchi Keiko , Nakagiri Nobuyuki , Miyashita Masayuki
Published: July 2002

An organosilane trimethylsilyl (TMS) monolayer prepared on silicon (Si) substrate by chemical vapor deposition was successfully applied as a self-developing resist for atomic force microscope (AFM) lithography. The thickness of the monolayer was less than 1 nm. This resist was locally degraded due to electrochemical reactions induced in the junction between a conductive AFM probe and a Si–TMS sample. The generated pattern on the sample was then transferred to the Si substrate by chemical etching using the degraded region as an etching window. Degradation of the monolayer proceeded with both positive and negative sample biases. However, the absolute values of the voltage at which the probe-scanned region began to show etching were +3.0 for Vs>0 and −5.0 V for Vs<0, in a 60% relative humidity air atmosphere. Faster patterning was achieved through increased current flow by applying a higher bias voltage. A 500 μm/s line drawing at Vs=+20.0 V with 2–3 nA was obtained. The number of injected electrons was estimated to be hundreds of times larger than the number of TMS groups in the scanned area. We therefore concluded that only a small part of the current flowing through the probe-sample junction is actually responsible for the degradation.
High resolution electron beam lithography using ZEP-520 and KRS resists at low voltage
Authors: Tanenbaum D. M. , Lo C. W. , Isaacson M. , Craighead H. G. , Rooks M. J. , Lee K. Y. , Huang W. S. , Chang T. H. P.
Published: July 2002

ZEP-520 and KRS resist systems have been evaluated as candidates for use in low voltage electron beam lithography. ZEP-520 is a conventional chain scission resist which has a positive tone for over two orders of magnitude in exposure dose. KRS is a chemically amplified resist which can be easily tone reversed with a sensitivity ∼8 μC/cm2 at 1 keV. Both resist systems are shown to have sensitivities ∼1 μC/cm2 for positive tone area exposures to 1 keV electrons. A decrease in contrast in 50 nm thick resist layers is seen when exposure voltage is lowered from 2 to 1 keV, indicating nonuniform energy deposition over the resist thickness. High resolution single pass lines have been transferred into both Si and SiO2 substrates at both low and high voltages in each resist system without using multilayer resist masks. The ZEP-520 and KRS resists are shown to have resolutions of 50 and 60 nm, respectively, at 1 kV, within a factor of 2 of their high voltage resolutions under identical development conditions. A cusp shaped etch profile in Si allows high aspect ratio 20 nm wide trenches to be fabricated using these resists on bulk Si. Low voltage exposures have been used to pattern gratings with periods as small as 75 and 100 nm in ZEP-520 and KRS, respectively. Low voltage exposures on SiO2 show no indications of pattern distortion due to charging or proximity effects.
Electron-beam-induced deposition of copper compound with low resistivity
Authors: Ochiai Yukinori , Fujita Jun-ichi , Matsui Shinji
Published: July 2002

Electron-beam-induced deposition of copper was performed using hexafluoro-acetyoacetonate copper vinyl-trimethy-silane (HFA⋅Cu⋅VTMS) gas. The deposition was demonstrated by using a 30 keV environmental scanning electron microscope and a 50 keV electron beam lithography system in an atmosphere of precursor gas: HFA⋅Cu⋅VTMS. The deposition rate, composition, and electrical resistivity of the deposited material were measured. The deposition rate was 6.6 nm/(C/cm2) at a pressure of 160 Pa. The resistivity was 3.6 μΩ cm at room temperature deposited at a pressure of 6.7×10−4 Pa. The resistivity is the lowest so far reported.
Emission measurements and simulation of silicon field-emitter arrays with linear planar lenses
Authors: Tang Cha-Mei , Swyden T. A. , Thomason K. A. , Yadon L. N. , Temple D. , Ball C. A. , Palmer W. D. , Mancusi J. E. , Vellenga D. , McGuire G. E.
Published: July 2002

Results of beam collimation experiments on linear field-emitter arrays with linear planar lenses are summarized. The electron beam is imaged on a phosphor screen. In general, as lens voltage is reduced relative to the gate voltage, the elliptically shaped screen images narrow, becoming fine lines with emission currents showing only modest reductions. This reduction of emission current can be overcome by increasing the gate voltage only a few volts without affecting beam collimation. As the lens voltage is reduced, screen current decreases relative to emission current while gate current increases, indicating that some emitted electrons in this linear lens geometry cannot propagate to the anode screen. Experimental data and qualitative modeling are in fair agreement.
Electrical and microstructure analysis of ohmic contacts to p- and n-type GaSb, grown by molecular beam epitaxy
Authors: Vogt A. , Hartnagel H. L. , Miehe G. , Fuess H. , Schmitz J.
Published: July 2002

Pd based and conventional TiPtAu contacts were realized on GaSb grown by molecular beam epitaxy. For p-type GaSb, an undoped sample with an acceptor background concentration of 6.6×1016 cm−3 and for n-type GaSb tellurium-doped samples with donor concentrations of 7.9×1017 and 1.2×1018 cm−3 were used. Circular transmission line patterns were defined on the samples for determining the specific contact resistivity. On n-type GaSb, the metallizations consisted of palladium and one of the dopants germanium or sulphur. Rapid thermal annealing lead to values of 4×10−5 Ω cm2. On p-type GaSb, nonalloyed TiPtAu and alloyed PdGePd contacts were deposited. Values as low as 5.6×10−6 Ω cm2 could be obtained. The interfaces of the TiPtAu, the PdGePd, and PdSPd contacts were studied by high resolution cross-sectional transmission microscopy.
Wavelength dependence of the magneto-optical properties of the interfaces of a Au sandwiched (001) Fe film
Authors: Geerts Wim , Katayama T. , Suzuki Y. , Childress J.
Published: July 2002

The polar ellipticity spectra of the interfaces of epitaxial Fe/Au(001) wedges have been measured. The interface spectra resemble neither the reflection Faraday spectrum of Au nor the thin-film spectra of thin Au sandwiched Fe. The existence of low and high energy peaks suggest that magneto-optical transitions occur from and to the interface states.
Mn 3s multiplet splitting of pseudomorphic Mn overlayers on Ru(001)
Authors: Sham T. K. , Shek M. L. , Hrbek J. , Campen D. G. Van
Published: July 2002

The Mn 3s multiplet splitting for a series of Mn overlayers on Ru(001) has been measured with synchrotron radiation photoemission spectroscopy. These overlayers were prepared by vapor deposition of Mn onto a Ru(001) substrate at a monolayer/minute dosing rate at room temperature. Under these conditions, the Mn overlayers grow pseudomorphically to multilayer coverages. It is found that this system exhibits a noticeable increase in the Mn 3s multiplet splitting and a positive binding energy shift as the coverage increases from monolayer to multilayer (12 ML). These results are attributed to the increase in the atomic volume, and hence the local magnetic moment at the Mn site on the average, with increasing coverage.
Strain-modulated epitaxy: Modification of growth kinetics via patterned, compliant substrates
Authors: Carter-Coman Carrie , Brown April S. , Bicknell-Tassius Robert , Jokerst Nan Marie , Fournier Françoise , Dawson Douglas E.
Published: July 2002

Bonded, thin film compliant substrates can be used to reduce the strain in a lattice-mismatched overlayer during epitaxial growth. We have presented an initial demonstration of the use of thin film GaAs compliant substrates fabricated by epitaxial liftoff or substrates removal and bonded to a mechanical host. This processing approach can be coupled with the patterning of the bonded surface to realize a lateral thickness variation. This thickness variation, in turn, can be used to realize a lateral strain variation in the growing mismatched overlayer. The strain can then be used to modify molecular beam epitaxy (MBE) growth kinetics, such as cation desorption and migration. With this technique the lateral control of composition and thickness can be realized without any surface topography. In this article, we discuss the growth of InGaAs films on compliant substrates produced by epitaxial lift-off and substrate removal. In addition, we discuss the various extrinsic effects associated with the compliant substrates, including the effects of the bonding and the results of MBE temperature cycling experiments. Finally, the characteristics of InGaAs thin films grown on GaAs patterned compliant substrates are presented.
Analysis of cracking efficiency of an atomic hydrogen source, and its effect on desorption of AlxGa1−xAs native oxides
Authors: Wicks G. W. , Rueckwald E. R. , Koch M. W.
Published: July 2002

The absolute cracking efficiency of a commercial atomic hydrogen source is found to be as great as 30%. Negligible recombination of atomic hydrogen into molecular hydrogen occurs in the molecular beam epitaxy chamber. The cracking process can be accurately modeled as an equilibrium process. An atomic hydrogen flux impinging on the surface of GaAs lowers the oxide desorption temperature by ∼100 °C. At temperatures up to 700 °C, atomic hydrogen does not enable the thermal desorption of AlxGa1−xAs oxides for x≳10%–20%.
Simulation of three-dimensional refractory metal step coverage over contact cuts and vias
Authors: Sheergar M. K. , Smy T. , Dew S. K. , Brett M. J.
Published: July 2002

In very large scale integration metalization processes, thin diffusion barrier metal films deposited over vias and contacts are used to inhibit the diffusion of the top metal layer into the underlying junctions. These thin films are normally sputter deposited and their reliability is crucial to die yield and device lifetime. As wafer sizes increase, die at the wafer edge receive a directionally asymmetrical sputter flux, leading to nonuniform and asymmetrical film coverage over vias and contacts. Two three-dimensional (3D) extensions of the two-dimensional (2D) film growth program SIMBAD are presented. The first extension (quasi-3D) assumes a radially symmetrical adatom flux distribution and would be appropriate for the simulation of film deposition on regions near the central axis of a radially symmetrical target. Due to the assumption of a symmetrical flux distribution, the resulting film growth is symmetrical. The second extension (interpolated-3D) does not assume that the flux is symmetrical and is intended for the simulation of asymmetrical film growth off-axis. Both extensions provide a 3D surface of the deposited film and the microstructure and profile of 2D slices through the via or contact. In order to determine the accuracy of the two models, simulations were compared to W films sputter deposited over contacts having an aspect ratio of 3:1. The models were tested for a substrate placed directly under the center of the target. The interpolated-3D model was also tested for asymmetrical fluxes by placing the substrate off-axis by 2.2, 5.0, and 8.1 cm. The comparisons with the experimental results indicate that both the surface profiles and the microstructure of the deposited films were predicted well by the two models. The interpolated 3D model was very successful at predicting deposition profiles for off-axis deposition flux.
Characterization of the Si/SiO2 interface formed by remote plasma enhanced chemical vapor deposition from SiH4/N2O with or without chlorine addition
Authors: Park Young-Bae , Li Xiaodong , Rhee Shi-Woo
Published: July 2002

The Si/SiO2 interface formed by remote plasma enhanced chemical vapor deposition (RPECVD) at low temperature with SiH4/N2O or SiH4/N2O/Cl2 was studied and compared with thermal oxidation. The interface of the CVD SiO2 without chlorine addition is rougher than that with chlorine addition. But the surface roughness of CVD SiO2 films increases with chlorine addition. The thermal oxidation induces strong interface strains, and the strains generated by the CVD SiO2 without chlorine addition are stronger and are distributed more nonuniformly than those by the chlorinated SiO2. It is believed that chlorine addition during RPECVD affects the initial stages of deposition, and chlorine is combined with Si dangling bonds existing at the Si/SiO2 interface through the formation of Si–Clx bonds. It was also found that with chlorine addition during RPECVD, the strained layer thickness, interface trap density, and suboxide density could be lowered significantly.
Image placement errors in x-ray masks induced by changes in resist stress during electron-beam writing
Authors: Acosta R. E. , Puisto Denise
Published: July 2002

Image placement demands for x-ray masks useable in sub-0.25 μm applications have prompted a renewed effort to further reduce or eliminate sources of mask distortion. In this work we studied a phenomenon that so far had been overlooked among the contributors to poor image placement: the large change in stress of some resists upon exposure. For instance, it was found that the stress of PMMA films changes from ≂1×108 dyn/cm2 in the unexposed state to ≂1×107 dyn/cm2 after the exposure dose received during electron-beam (e-beam) writing. Because e-beam writing is a serial process, this stress change induces a dynamic distortion of the mask, since the force applied on the membrane by the resist film varies continuously as writing of the pattern progresses. The stress of PMMA films was determined as a function of dose for exposures using e-beams of 100, 75, and 25 keV energy, broadband UV light (from a Hg lamp), and to x rays from a synchrotron ring with λcharac.=10 Å. In all cases, the stress was found to be a very strong function of the exposure dose at low doses with a slow decay in stress change at larger dose values. The stress changes upon exposure are attributable to changes in molecular weight (MW) distribution, rather than to a reduction in MW only, since the stress of unexposed PMMA films was found to be the same for a wide range (25k to 920k) of initial MW resin. Model experiments demonstrated the correlation between the in-plane distortion (IPD) of membranes and the lowered resist stress. Because of the drastic stress drop at low doses, fogging prior to writing reduces the distortion problem. Other methods thought to reduce resist stress (various annealing cycles, different solvents, plasticizers) proved unsuccessful. The effect of fogging on IPD was measured for several model cases and found to correlate with the lowered resist stress. Initial evaluation of the changes that fogging induces on the lithographic performance of the resist was performed.
X-ray magnetic microscopy and spectroscopy using a third generation synchrotron radiation source
Authors: Young A. T. , Padmore H. A. , Smith N. V.
Published: July 2002

Applications of x-ray magnetic circular dichroism (XMCD) to the study of magnetic materials are described. XMCD spectra can be used to quantitatively determine magnetic properties on an element-specific basis. These spectra are also sensitive to the chemical state and environment of the element being probed. The dichroism effect can also be used to produce images of microscopic magnetic structures and domains. Third generation synchrotron light sources are well suited to these experiments. Current and planned facilities at the Advanced Light Source, the first of the new light sources in the U.S., are described, focusing on a new facility with specialized undulators which will directly produce high flux, high brightness beams of circularly polarized x-rays. With new beamlines which have been optimized for either spectroscopy or microscopy, this facility will provide the capability to provide detailed information about magnetic materials.
Transient response of tapping scanning force microscopy in liquids
Authors: Chen G. Y. , Warmack R. J. , Oden P. I. , Thundat T.
Published: July 2002

Tapping-mode scanning force microscopy in liquids is usually accomplished by acoustic excitation of the cantilever because of the strong viscous damping. Contact of the tip with the sample surface results in a damping of the cantilever amplitude with an anharmonic response. This interaction is modeled as a viscous-damped, one-dimensional harmonic oscillator periodically perturbed by an exponential surface potential. Experimental results verify the validity of the model.
Direct imaging of SiO2 thickness variation on Si using modified atomic force microscope
Authors: Mang K. M. , Khang Y. , Park Y. J. , Kuk Young , Lee S. M. , Williams C. C.
Published: July 2002

Thickness of silicon dioxide was measured by combined atomic force microscopy and nanoscopic C–V spectroscopy. The spatial variation of the oxide thickness and dopant profile on the masked Si were directly imaged. The nanoscopic C–V reveals the same trends as the macroscopic C–V. Shadowing effect of phosphorous ions during implantation was observed from dopant profile in masked Si substrates.
Imaging mechanism and effects of adsorbed water in contact-type scanning capacitance microscopy
Authors: Nakagiri Nobuyuki , Yamamoto Takuma , Sugimura Hiroyuki , Suzuki Yoshihiko
Published: July 2002

In order to demonstrate its unique capabilities, a combined microscope comprised of a scanning capacitance microscope and a contact mode atomic force microscope was used to image a buried structure. The atomic force microscopy images surface topography, while the scanning capacitance microscope simultaneously images buried structure. By applying a modulation technique, the voltage derivative of the capacitance (dC/dV) was used as a scanning capacitance microscope signal. The sample used for the demonstration was a silicon wafer with metal lines 4 nm in thickness covered by a 40-nm-thick layer of silicon oxide. The scanning capacitance microscope image was dependent on the bias voltage applied to the probe and the sample. Since the scanning capacitance microscope signal above the metal lines is zero, the bias voltage dependency of the contrast in scanning capacitance microscope images corresponds directly to the scanning capacitance microscope signal versus V at locations where the metal line is not buried. However, the bias dependency of the contrast did not agree with the scanning capacitance microscope signal observed between metal lines. A possible mechanism for the discrepancy between these bias dependencies is discussed based upon charge deposition on the sample surface caused by tip contact and lateral movement of the charges in the adsorbed water on the sample surface.
Obtaining a physical two-dimensional Cartesian reference
Authors: Takac Michael T. , Ye Jun , Raugh Michael R. , Pease R. Fabian , Berglund C. Neil , Owen Geraint
Published: July 2002

A two-dimensional self-calibration method obtains Cartesian traceability for high-precision tools. The calibration method incorporates group theory principles yielding mathematical solutions to a physical Cartesian reference. The calibration method was developed by Stanford University, Hewlett Packard, IBM and funded by the Semiconductor Research Corporation. The method was applied to Leica’s LMS2000 and LMS2020 systems.
Evaluation of the long-term stability of critical-dimension measurement scanning electron microscopes using a calibration standard
Authors: Mizuno Fumio , Shimizu Minoru , Sasada Katsuhiro , Mizuno Takeshi
Published: July 2002

In critical-dimension measurement using critical-dimension measurement scanning electron microscopes (CD-SEMs), measurement variation due to a long-term instability of CD-SEM cannot be disregarded to achieve a measurement reproducibility of 3 nm, which is required for next-generation subquarter-micron large scale integrations. We have evaluated the long-term stability of the Hitachi S-8820 CD-SEM by using a calibration standard, which has 0.24 μm pitch structures. The results of our evaluation have demonstrated that the use of the calibration standard for CD-SEMs was effective for checking the instability of instruments, which might produce inaccuracy and imprecision of CD measurements, and measurement error due to instrumentation of 1 nm can be achieved by precise control of instrumental parameters using the calibration standard.
Growth mode and defect generation in ZnSe heteroepitaxy on Te-terminated GaAs(001) surfaces
Authors: Ohtake A. , Kuo L. H. , Yasuda T. , Kimura K. , Miwa S. , Yao T. , Nakajima K. , Kimura K.
Published: July 2002

We have studied growth mode and defect generation in heteroepitaxy of ZnSe on Te-terminated GaAs(001) surfaces. The high saturation coverage of Zn on Te-terminated GaAs enhances the layer-by-layer growth of ZnSe. However, high densities of faulted defects (∼5×108/cm2) are generated in the ZnSe film. We have found that the generation of defects is not necessarily ascribed to an island growth mode, but is closely related to the formation of a vacancy-contained Ga–Te interface layer.
Liquid-phase adsorption process of β-picoline on stilbite (010) observed by atomic force microscopy
Authors: Komiyama Masaharu , Gu Minming
Published: July 2002

Liquid-phase adsorption process of β-picoline molecules on a (010) surface of a natural zeolite stilbite was observed by atomic force microscopy (AFM). Initially, the surface was covered with excess multilayer β-picoline molecules. Removal of this excess layer by AFM scanning exposed a possible random-adsorbed monolayer phase. A well-ordered two-dimensional quasihexagonal phase developed slowly, with an estimated rate of ∼6 nm/min. The 2D unit cell dimension of the latter ordered phase was 0.55±0.04 nm. The ordered phase is incommensurate with the substrate surface, although one of the 2D lattice unit vectors of the adsorbed phase makes an angle of ∼50° and ∼100° with respect to the a and c axes of the substrate (010) plane, respectively. From the position of the methyl group in the β-picoline molecule it is estimated that the molecules are adsorbed on the surface with their C–N bond parallel to the surface.
Magnetotransport through mesoscopic antidot arrays
Authors: Xu Hongqi
Published: July 2002

We present a theoretical investigation of the magnetotransport in finite antidot lattices. We have calculated the magnetoconductance, which shows slow and rapid oscillations. To interpret the rapid oscillations, we have studied the magnetoconductance correlation function and the level-spacing distribution of the systems. The results allow us to interpret the rapid oscillations as an effect of the interference of electrons traveling along chaotic trajectories in the antidot lattices. The slow oscillations can be understood in terms of pinned electron orbits around groups of antidots.
Formation of Si nanowire by atomic manipulation with a high temperature scanning tunneling microscope
Authors: Hasunuma R. , Komeda T. , Mukaida H. , Tokumoto H.
Published: July 2002

The formation of Si nanowire during indentation of the scanning tunneling microscope tip onto the Si(111) surface was investigated by changing the sample bias, the temperature, and the tip retraction speed. The wire length at room temperature is in the order of 1 nm, however, the wire was elongated remarkably with either increasing temperature or bias voltage while keeping a positive sample bias. The wire was also elongated when the tip speed was decreased. The typical length was ∼14 nm at 481 °C, +2.0 V and 320 nm/s. In order to explain these results, we proposed a simple model for the wire formation by taking into account the surface diffusion and electromigration effects.
Principle of atomic grating and its application in nanotechnology
Authors: Hao H. W. , Qiao H. , Cheng H. K. , Wei W. W. , Yi W. K.
Published: July 2002

We present here a new method using atomic grating fringe to achieve resolution as high as one-tenth of an atomic lattice in nanometrology system. The principle of this method is as follows: by superposing two scanning probe microscope (SPM) atomic images, when one is rotated to a specific small angle, moire fringes will be observed. These moire fringes have symmetry and larger periodicity than atomic lattice. Comparing the difference of the fringes obtained before and after sample displacement, we can determine the direction and quantity of movement of the sample within one-tenth of the lattice spacing. This method is suitable to characterizing the stability of the SPM instrument and to single atom location and manufacturing.
Preparation of probe tips with well-defined spherical apexes for quantitative scanning force spectroscopy
Authors: Schwarz U. D. , Zwörner O. , Köster P. , Wiesendanger R.
Published: July 2002

A method for the preparation of scanning force microscopy (SFM) tips with spherically shaped tip apexes and known tip radii by exposing commercially available silicon cantilevers to the electron beam of a transmission electron microscope is presented. The spherical shape of the tip apexes was achieved by growth of a contamination layer at the end of the tip using the electron-beam deposition process. Well-defined radii between 7 and 120 nm could be produced. The importance of such tips for quantitative SFM measurements is discussed. Topographical measurements on a special test sample are shown as well as measurements of the frictional force as a function of the loading force as an example for quantitative spectroscopical measurements.
Design optimization for two lens focused ion beam columns
Authors: Wang Li
Published: July 2002

This article systematically analyzes all possible operation modes in a two lens focused ion beam column utilizing analytical formalism and numerical analysis. The non-crossover mode is found to be inherently superior to the crossover mode, and a column in the crossover mode with a single fixed aperture can never realize optimal magnifications for all beam current levels. The non-crossover mode gives the best resolution. The crossover mode, however, offers many attractive features such as simplicity and quick changeover time. Optimization procedures based on operational mode analysis with examples are also given.
Field induced antiferromagnetic ordering in NiS cluster confined in zeolite Y
Authors: Ding Weiping , Zhong Wei , Zhang Ning , Guo Zaibing , Gu Gang , Du Youwei
Published: July 2002

An interesting field induced antiferromagnetic ordering in NiS clusters confined in Y molecular sieve was observed. The NiS cluster-zeolite Y composite exhibits an unusual antiferromagnetic ordering state under a magnetic field of 0.724–1.164 T and paramagnetic behavior out of this field region. The antiferromagnetic ordering can be stable up to 180 K. The phenomenon may be understood by the concept of energy level crossing due to intracluster interaction at a certain magnetic field.
Fabrication of field emission display prototype based on Si field emission arrays with diamond coating
Authors: Givargizov E. I. , Zhirnov V. V. , Chubun N. N. , Stepanova A. N.
Published: July 2002

A new concept of field emission display (FED) based on ungated silicon field emission arrays with diamond coating is proposed. FED prototypes have been fabricated and tested in dc and pulse modes. Sufficiently bright light emission was observed at an anode-to-cathode voltage of 200–300 V.
Design and implementation of a real-time hierarchical parallel postprocessor for 100 keV electron beam lithography
Authors: Muray Lawrence P. , Anderson Erik H. , Boegli Volker
Published: July 2002

A farm of off-the-shelf microprocessors is evaluated for use as a real-time parallel postprocessing subsystem of the Lawrence Berkeley National Laboratory datapath, including backscatter proximity correction. The native data format is GDSII with embedded control. Data storage is fully hierarchical with no intermediate binary pattern data formats. Benchmarks of a four Pentium Pro™ farm, after optimization, demonstrate compatibility with exposure rates of 25 MHz for 32% area fill on a vector scan Gaussian beam e-beam tool. Scalability of the architecture is discussed in detail.
Data analysis methods for evaluating lithographic performance
Authors: Ferguson Richard A. , Martino Ronald M. , Brunner Timothy A.
Published: July 2002

Lithographic improvements obtained from process modifications or application of optical enhancement techniques can often be obscured within experimental noise and inconsistent data analysis techniques. At IBM, the need for a common platform for the accurate analysis of lithographic data led to the development of a new software analysis package entitled LEOPOLD. In this article, the exposure-defocus methodology taken by LEOPOLD for accurate calculation of the total lithographic process window in the presence of experimental noise is outlined; the extension of this method to the evaluation of the common process window through applications in the areas of optical proximity effects, analysis of optical enhancement techniques, and across-field exposure tool characterization is also demonstrated.
Use of attenuated phase masks in extreme ultraviolet lithography
Authors: Wood O. R. , White D. L. , Bjorkholm J. E. , Fetter L. E. , Tennant D. M. , MacDowell A. A. , LaFontaine B. , Kubiak G. D.
Published: July 2002

We have used an attenuated phase mask, a mask with a π-phase shifting attenuator, in extreme ultraviolet lithography at 13.9 nm wavelength to produce resist profiles with sharper, more vertical sidewalls.
Novel illumination system of synchrotron radiation stepper with full field exposure method
Authors: Watanabe Yutaka , Hara Shinichi , Mizusawa Nobutoshi , Fukuda Yasuaki , Uzawa Shunichi
Published: July 2002

We estimate the pattern distortion and the critical dimension (CD) variation due to the thermal distortion under a large exposure field for the full field exposure method. We verify that the effect of the thermal distortion of the mask and wafer on the pattern distortion and the CD variation is small enough under the condition of mass production of devices of 0.1 μm design rule. We present a design of the novel two mirror illumination system which can improve the throughput both by exposing a field as large as 50 mm square and by condensing synchrotron radiation (SR) spread in the horizontal plane. The effects of the variation of the position of the SR source and the mirrors and the size of the SR source on the performance of the stepper are investigated.
Specific behavior of chemically amplified systems with low activation energy under electron-beam exposure: Implementation of 248 and 193 nm resists
Authors: Mortini B. , Tedesco S. , Dal’Zotto B. , Paniez P.
Published: July 2002

Low activation energy resists are studied through two formulations representative of these systems, namely, Shipley 248 nm XP9493 and MCC 193 nm TER-1 resists. It is shown that their specific behavior can be easily demonstrated by using differential scanning calorimetry techniques at different steps of the lithographic process. As these resists present a low activation energy for their deprotection, the postexposure bake (PEB) is not necessary so a comparison between processes with and without a PEB step can be made. Processes without PEB are interesting as they allow deconvolution and an emphasis on different phenomena (evaporation, diffusion, and recompaction) which are of tremendous importance for chemically amplified resists. Finally, processes without PEB can allow a correlation of the mechanisms involved in the resists to lithographic performance.
Time dependence of etch-induced damage generated by an electron cyclotron resonance source
Authors: Berg E. W. , Pang S. W.
Published: July 2002

The effects of etch time on the damage induced during dry etching have been studied. GaAs- and InP-based materials were etched for different times in an electron cyclotron resonance source and the electrical and optical characteristics were measured. Variations in Schottky diode ideality factor (n) and barrier height (φb) were used to measure dry-etch-induced electrical damage at the surface of GaAs after different etch times. The contact resistance of In0.53Ga0.47As, extracted from transmission line measurements, was also investigated for different etch times and compared to the etch time dependence of GaAs. Capacitance–voltage (C–V) measurements from Schottky diodes and photoluminescence (PL) intensity from GaAs/Al0.30Ga0.70As multiple quantum well (MQW) structures were used to investigate the time dependence of the etch damage farther below the surface. The damage in GaAs as shown by n and φb shows marked deterioration after 10 s of etching but improves after longer etching. The contact resistance of In0.53Ga0.47As was found to increase fastest in the first 10 s, but the electrical characteristics did not improve with etch time as the GaAs did. There was no etch time dependence in the C–V measurements from the diodes or the PL spectra from the MQWs, indicating that variations in dry-etch-induced damage with etch time are mostly confined to the surface. Using wet chemical etching, the damage profile was investigated and the most damage was found within ∼15 nm from the surface for GaAs while In0.53Ga0.47As did not return to the original value after removing 20 nm of the surface. This indicates that the damage generation, removal, diffusion, and channeling mechanisms or rates may be different for the two materials. By changing the temperature of the stage during etching from −130 to 350 °C, the etch time dependence of the n and φb of GaAs was affected, indicating that diffusion of defects may be mainly responsible for the variations in electrical characteristics with etch time.
Super-smooth x-ray reflection grating fabrication
Authors: Franke A. E. , Schattenburg M. L. , Gullikson E. M. , Cottam J. , Kahn S. M. , Rasmussen A.
Published: July 2002

Blazed, grazing incidence x-ray reflection gratings are an important component of modern high resolution spectrometers and related x-ray optics. These have traditionally been fabricated by diamond scribing in a ruling engine, or more recently by interferometric lithography followed by ion etching. These traditional methods result in gratings which suffer from a number of deficiencies, including high surface roughness and poor control of the groove profile. These deficiencies lead to poor diffraction efficiency and high levels of scattered light. We have developed a novel fabrication method for fabricating blazed x-ray reflection gratings which utilizes silicon wafers that are cut 0.7° off of the (111) plane. In solutions such as potassium hydroxide (KOH), silicon is etched in 〈111〉 directions orders of magnitude slower than in other directions, resulting in extremely smooth {111} facets. The gratings are patterned using interferometric lithography with 351.1 nm wavelength and transferred into the substrate using tri-level resist processing, reactive-ion etching (RIE), and silicon nitride masking during the KOH etch. The narrow (<0.1 μm) ridge of silicon which supports the nitride mask is removed using a chromium lift-off step followed by a CF4 RIE trench etch. The result is a grating with extremely smooth blaze facets which is suitable for x-ray reflection after evaporative coating with thin Cr/Au. Atomic force microscope images confirm that fabricated gratings have less than a 0.4 nm rms roughness—much smoother than conventional gratings which have over ∼1 nm roughness. Theory predicts that reduced blaze facet roughness increases diffraction efficiency. Experiments and simulations performed at the Lawrence Berkeley Laboratory and Columbia University confirm that efficiency is increased; in fact, measured peak efficiencies reach ∼80% of calculated theoretical limits. Peak grating efficiencies were achieved that are ∼35% greater than that of the best available ruled masters of comparable design.
Techniques and applications of secondary ion mass spectrometry and spreading resistance profiling to measure ultrashallow junction implants down to 0.5 keV B and BF2
Authors: Harrington William L. , Magee Charles W. , Pawlik Marek , Downey Daniel F. , Osburn Carlton M. , Felch Susan B.
Published: July 2002

Secondary ion mass spectrometry and spreading resistance profiling techniques have been used to measure dopant profiles and determine electrical activation in ion-implanted samples with effective ion energies as low as 112 eV (i.e., for 0.5 keV BF2). The analytical protocols will be discussed and used to compare the results for samples implanted with ion energies ranging from 0.5 keV (B and BF2) to 8.9 keV (BF2), with and without Ge preamorphization (with and without solid phase epitaxy anneals at 550 °C for 30 min), and finally annealed at 750–1050 °C for 10 s. Limitations of both analytical techniques for ultrashallow junction characterization and areas where improvements are required are discussed.
Field emission of nitrogen-doped diamond films
Authors: Han I. T. , Lee N. , Lee S. W. , Kim S. H. , Jeon D.
Published: July 2002

The authors investigated field emission characteristics of nitrogen-doped diamond films, which were grown using microwave plasma-enhanced chemical vapor deposition. Nitrogen-doped films showed low turn-on voltages below 2 V/μm. Secondary ion mass spectroscopy was used to compare nitrogen concentrations in the films. Morphologies, Raman spectra, the resistivities, and surface roughness of the films were changed as the nitrogen concentrations varied. The field emission properties of heavily nitrogen doped diamond films were related to the film resistivity, surface morphologies and Raman characteristics.
Study of field electron emission phenomenon associated with N-doped amorphous diamond thin films
Authors: Chen J. , Wei A. X. , Deng S. Z. , Lu Y. , Zheng X. G. , Chen D. H. , Mo D. , Peng S. Q. , Xu N. S.
Published: July 2002

Experiments have been carried out to study the field electron emission characteristics of nitrogen-doped amorphous diamond thin films prepared by magnetic-field filtered carbon ion deposition. A transparent anode imaging technique is used to record the spatial distribution of individual emission sites and the total emission current–voltage characteristics of the films. Also, the optical and electrical properties of the films having different nitrogen-doping levels have been studied. A correlation has been found to exist between the field-emission characteristics and the band gap of the films; i.e., it is found that the films of relatively small optical band gap have low turn-on fields.
Analysis of scanning force microscope force-distance data beyond the Hookian approximation
Authors: Zypman Fredy R. , Eppell Steven J.
Published: July 2002

A new method for obtaining force–distance curves using scanning force microscopy is suggested. The theoretical justification for this method is discussed. The method, involving frequency domain measurements of cantilever motion, is predicted to provide improved force data using standard single point measurement of the cantilever deflection. Shortcomings of the standard Hookian model that are alleviated by our model are discussed. Spectroscopic information and knowledge of the applied force during intermittent contact mode imaging are shown to be more appropriately determined using the new method.
Development of ion and electron dual focused beam apparatus for high spatial resolution three-dimensional microanalysis of solid materials
Authors: Cheng Zhaohui , Sakamoto Tetsuo , Takahashi Masanori , Kuramoto Yasuyuki , Owari Masanori , Nihei Yoshimasa
Published: July 2002

We constructed an ion and electron dual focused beam apparatus to develop a novel three-dimensional (3D) microanalysis technique. In this method, a Ga focused ion beam (Ga FIB) is used as a tool for successive cross sectioning of the sample in the “shave-off” mode, while an electron beam (EB) is used as a primary probe for Auger mapping of the cross sections. Application of postionization with EB to Ga-FIB secondary ion mass and two-dimensional (2D) elemental mapping with Ga-FIB-induced Auger electrons are also in the scope of the apparatus. The 3D microanalysis was applied to a bonding wire on an integrated circuit (IC). A series of EB-induced sample current images of the successive cross sections were obtained as a function of the cross-sectioning position. This result showed the capability to realize the 3D Auger microanalysis. Two-dimensional elemental mapping with Ga-FIB-induced Auger electrons was realized for the first time on the IC surface. Its applicability to surface analysis was evaluated.
Chemically and geometrically enhanced focused ion beam micromachining
Authors: Russell P. E. , Stark T. J. , Griffis D. P. , Phillips J. R. , Jarausch K. F.
Published: July 2002

Improvements in focused ion beam (FIB) material removal rates utilizing geometric and chemical enhancement were investigated. Geometrical optimization of FIB micromachining of Permalloy and diamond was investigated to determine the magnitude of material removal rate gains that could be attained by increasing the angle of the ion beam with respect to the sample surface normal. The combination of geometrical optimization with chemical enhancement (C2Cl4 for Permalloy and H2O and XeF2 for diamond) was then investigated to determine whether additional gains in material removal rate could be attained. FIB sharpening of a diamond nanoindenter tip is also presented as a practical example of diamond micromachining with H2O as the removal rate enhancing species.
Structural characterization of ultrathin nanocrystalline silicon films formed by annealing amorphous silicon
Authors: Lützen J. , Kamal A. H. M. , Kozicki M. N. , Ferry D. K. , Sidorov M. V. , Smith David J.
Published: July 2002

The fabrication and structural characteristics of ultrathin nanocrystallization silicon films is reported. Amorphous Si layers, with nominal thicknesses in the range of 3.5–11 nm, were deposited by low-pressure chemical vapor deposition onto amorphous SiO2 and then crystallized using rapid thermal annealing at temperatures from 650 to 750 °C. High-resolution electron microscopy revealed that the resulting films were comprised almost entirely of Si nanocrystallites with a small fraction of remaining amorphous material. The grain size in the vertical growth direction was controlled by the thickness of the as-deposited amorphous Si film, whereas the lateral grain size was determined by appropriate choice of the annealing conditions.
Emission characteristics of a conical field emission gun
Authors: Yamamoto Youiti , Miyokawa Toshiaki
Published: July 2002

Characteristics of a conical field emission gun (FEG) are measured and discussed. The field emission current from a W emitter is found to obey the Fowler–Nordheim (FN) equation. An expression was given describing the dependence of the mean work function on the curvature radius at the vertex of the emitter. Using scanning electron microscopy, a radius of 1500 Å was measured with which the slope of the FN plot yielded a mean work function of 4.8 eV. The initial value of the emission current, obtained after cleaning the tip by flashing, decays with time due to an increase of the work function caused by the adsorption of residual gases. The measured time dependent mean emission current was interpreted as a weighted superposition of local field emissions from the W(310), (100), (110), (111), and (112) planes. This interpretation resulted in a mean work function of 4.6 eV in good agreement with the value determined from the FN plot. For an accelerating voltage of 15 keV and an emission current of 8 μA after flashing, the dependence of the probe current on the extraction voltage was measured. For Vacc/Vex=1, an angular current density of (41±4) μA/sr was found. Similar measurements of the dependence of the probe current on the ratio Vacc/Vex (accelerating voltage/extraction voltage) made 3 h after flashing yielded (20±6) μA/sr for Vacc=Vex. The transfer efficiency defined as the ratio between probe current and emission current was found to be 0.4%–0.3%.
Etching processes and characteristics for the fabrication of refractory x-ray masks
Authors: Lercel Michael J. , Brooks Cameron J. , Benoit Douglas E. , Surendra Maheswaran
Published: July 2002

Refractory x-ray masks for a wide variety of pattern types were fabricated using tantalum silicon as the absorber material. Both positive (Shipley UVIII®) and negative (Shipley SNR200®) chemically amplified electron beam resists were exposed and the patterns transferred into a silicon oxynitride hardmask. The amorphous TaSi absorber was then etched using a Cl2/O2 reactive ion etch (RIE). From a mask manufacturing standpoint, the challenge is etching the wide variety of feature types that commonly occur in device processing. The overall etch process was characterized for the formation of both freestanding lines (using negative electron beam resist) and narrow trenches (using positive resist). RIE lag, feature shape dependence, and cross-mask uniformity in the etch bias were characterized for feature sizes down to 125 nm. The etch process has been implemented in a pilot line environment and is being used to produce product masks.
Experimental verification of the TEMPTATION (temperature simulation) software tool
Authors: Babin Sergey , Kuzmin Igor Yu.
Published: July 2002

Predicting the temperature rise during electron-beam lithography (EBL) is an important practical problem in the development of new EBL systems and in the optimization of new exposure processes. The TEMPTATION software tool was developed. This software uses an analytic solution of heat propagation in a multilayered substrate. The software attains both high speed and good accuracy. Experimental verification of the software was done. Simulated data were verified versus experiments made with variably shaped EBL systems using three different resists. Change of effective absorbed energy due to heating was simulated and compared to published data. Good agreement of predicted and measured data for both long-range and short-range resist heating was shown.
Adaptive selection of control points for improving accuracy and speed of proximity effect correction
Authors: Lee Soo-Young , Laddha Jayesh
Published: July 2002

A large class of the proximity effect correction schemes being currently used employ so-called control points in their implementation. Control points are the pixel locations in a circuit pattern at which energy received, referred to as exposure, is estimated. Depending on the exposure estimates at control points, the dose to be given to each feature (or subfeature) or the amount of shape modification for each feature is determined. Many proximity correction schemes including the first version of our scheme (PYRAMID 1.0) adopt a fixed selection of control points, which may not be optimal especially for high density, finely feature circuit patterns. Selection of control points greatly affects the accuracy and speed of correction. We have designed a simple but effective method for adaptively selecting control points. In this article we describe the scheme for adaptive control point selection with simulation results showing the successful correction of high-density, fine-feature circuits in less time.
Single layer chemical vapor deposition photoresist for 193 nm deep ultraviolet photolithography
Authors: Nault Mike , Weidman Tim , Sugiarto Dian , Mui David , Lee Carol , Yang John
Published: July 2002

The chemical vapor deposition resist film plasma polymerized methyl silane (PPMS) can be used as a single layer photoresist for optical lithography at 248 and 193 nm wavelengths. Upon exposure, the PPMS undergoes efficient photo oxidation in the presence of air to yield a siloxane network (PPMSO) giving patterns that can be dry developed using a chlorine-HBr plasma. After dry development, the PPMSO can be used to transfer a pattern through organic low κ materials, or can be converted to a silicon dioxide hardmask using a conventional resist stripper, then used to transfer patterns into polysilicon.