bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ observation of carbon-nanopillar tubulization process
Authors: Ichihashi Toshinari , Ishida Masahiko , Ochiai Yukinori , Fujita Jun-ichi
Published: December 2004

We observed the tubulization process of amorphous carbon nanopillars using an in situ transmission electron microscopy. Amorphous carbon nanopillars were grown by electron-beam-induced chemical vapor deposition on an iron-doped carbon foundation. Amorphous carbon nanopillars were transformed into graphitic tubules by annealing at about 650°C in the presence of iron nanoparticles supplied from the iron-doped carbon foundation. A molten catalyst nanoparticle penetrated an amorphous carbon nanopillar, dissolving it and leaving a graphite track behind. This graphitic nanotube synthesis technique using nanofabrication promises to bring about a great advance in nanotube electronic devices.
Influence of glass substrate surface roughness on extreme ultraviolet reflectivity of Mo∕Si multilayer
Authors: Miyagaki Shinji , Yamanashi Hiromasa , Yamaguchi Atsuko , Nishiyama Iwao
Published: December 2004

The influence of the surface roughness of a glass substrate on the extreme ultraviolet (EUV) reflectivity of Mo∕Si multilayer deposited on it by ASET’s helicon sputtering system was investigated. Deposition by helicon sputtering was found to produce a smoothing effect on the multilayer. That is, surface roughness with a spatial period below 100nm is smoothed out, but that with a spatial period longer than 100nm is not. The result is that the rms roughness of a Mo∕Si multilayer is slightly smaller than that of the substrate. The EUV reflectivity of the multilayer improved as the rms roughness decreased down to 0.30nm, and than leveled off at about 65% below that value, indicating that the EUV reflectivity is limited by some factor(s) other than surface roughness. However, a relatively high EUV reflectivity of 65% was obtained, even for an rms roughness of about 0.30nm.
Interferometric in situ alignment for UV-based nanoimprint
Authors: Fuchs A. , Vratzov B. , Wahlbrink T. , Georgiev Y. , Kurz H.
Published: December 2004

A high precision alignment concept is evaluated for suitability in UV-based nanoimprint lithography. Through three consecutive alignment steps an overlay accuracy of 50nm is obtained with ample room for further improvements.
Effect of electrostatic chucking and substrate thickness uniformity on extreme ultraviolet lithography mask flatness
Authors: Mikkelson A. , Engelstad R. , Sohn J. , Lovell E.
Published: December 2004

Extreme ultraviolet lithography (EUVL) is one of the leading candidates for next-generation lithography in the sub-45 nm regime. Successful implementation of this technology will depend upon advancements in many areas, including the quality of the mask system to control image placement errors. Such errors will occur at the wafer as a result of height variations of the patterned (frontside) mask surface (i.e., its nonflatness). The Semiconductor Equipment and Materials International EUVL Mask Standard (SEMI P37) specifies that the mask frontside and backside nonflatness be no more than 50 nm peak-to-valley (P-V). Currently, the lowest level of freestanding flatness of EUVL mask substrates from production-level polishing and finishing techniques is about 200 nm P-V. The frontside and backside of typical (and representative) EUVL substrates were measured for flatness and these surfaces were represented mathematically using Legendre polynomials. The Legendre coefficients were then utilized in a finite element model to predict the effect of chucking on the flatness of these substrates. One of the significant conclusions of this research is that the substrate thickness nonuniformity has a dominant effect on the flatness of the patterned surface after chucking.
Preliminary evaluation of surface plasmon enhanced light transmission with a scanning 257nm ultraviolet microscope
Authors: Maldonado Juan R. , Coyle Steven T. , Varner Jeffery K. , Moore Richard C. , Stark P. R. H. , Larson D. N.
Published: December 2004

Surface plasmon enhanced illumination (SPEI) devices could be useful in multielectron beam lithography systems to meet the roadmap requirements for mask- and direct write applications by creating arrays of light beams, or in conjunction with a photoemitter to produce a very stable array of electron beams from a patterned photocathode. Preliminary experiments were performed with a scanning 257nm UV transmission microscope to evaluate the performance of SPEI devices. Light transmission enhancement relative to simple apertures greater than 200× were obtained with these devices utilizing apertures as small as 60nm diameter. The results will be presented in this article together with other possible advantages for e-beam applications.
Modeling, fabrication, and experimental application of clear x-ray phase masks
Authors: Malueg Daniel H. , Taylor James W. , Thielman Don , Leonard Quinn , Dhuey Scott , Cerrina Franco
Published: December 2004

Phase-shifting masks are widely used in optical lithography, and the question is whether the technology can be extended to much shorter wavelengths. We have extensively modeled the use of clear phase-mask materials as absorbers for x-ray exposures. Similar to the optical domain, the imaging from x-ray phase masks is highly nonlinear, and thus can be used to produce a feature reduction of 3–5× compared to the mask pattern. This observation suggests that mask fabrication might be easier, but the technique is most suited for less dense pattern requirements. In this article we review some of the salient modeling, examine the requirements for effective fabrication of the masks, and provide some experimental verification of this approach to reach the sub-50nm region. It is not essential to have exactly a 180° phase shift in the clear material, because mask feature reductions can be achieved with 45, 90, 180, and 270° shifts by choosing the appropriate thicknesses of the clear material. A mask with a 235nm feature and a 45° thickness is transformed into a 134nm aerial feature, but the same dose for a 180° thickness results in an 86nm feature. The best resolution is obtained in the so-called bright peak enhanced x-ray phase mask (BPEXPM) mode with thicknesses appropriate to 180° or greater. Previous modeling of the clear phase feature indicated a strong dependence on the wall slope, and fabrication processes are being pursued to verify the modeling and demonstrate the slope dependence on the feature profile. Silicon nitride with a phase shift of 126° is currently employed, but other materials could also be used in the mask fabrication. Experimentally, we are pursuing the feature width reduction achieved from correctly fabricated masks to produce gate width structures at the sub-50nm region.
Optimum mode of operation for a low energy focused ion beam system
Authors: Rauscher Michael , Plies Erich
Published: December 2004

The system design and mode of operation for a dedicated low energy focused ion beam system based on immersion optics is presented. The ion beam is accelerated using a gun lens and the intermediate lens space is set on high potential. Beam retarding to the landing energy is accomplished within the objective lens. With this design the target is field free and can be kept on ground potential. As all voltage levels are comparatively low, both gun as well as objective lens can be operated in accel mode, thus improving system performance. The influence of Coulomb interactions is also taken into account. Calculations predict a spot size of approximately 80nm and a corresponding probe current density of 1A∕cm2 at a working distance of 15mm and a final beam energy of 3keV, respectively.
Experimental relationship between work function and dipole moment on ErO∕W(100) and LuO∕W(100) emitter surfaces
Authors: Saito Y. , Yada K. , Minami K. , Nakane H. , Adachi H.
Published: December 2004

A sharp reduction of work function occurs on a tungsten (100) surface after modifying of the surface with Er or Lu and oxygen and lasts for several hours. The fabricating process is similar to that of the standard ZrO∕W(100) Schottky emitter. The calculated work functions with the aid of Fowler–Nordheim plot are 1.8eV for ErO∕W(100) and 2.3eV for LuO∕W(100). These work functions are extremely low in comparison with both 4.6eV for bare W(100) and 2.9eV for ZrO∕W(100). The electrical dipole moments of complex pairs ErO and LuO are evaluated to be about 6.3 and 4.5D, respectively.
Direct spherical and chromatic aberration correction for charged particle optical systems
Authors: Turnbull William
Published: December 2004

A method to correct spherical and chromatic aberrations is described. The system provides complete physical and optical separation between first the first-order optics and higher order correctors. Calculations indicate subangstrom beams may be realized.
High-speed and high-precision deflectors applied in electron beam lithography system based on scanning electron microscopy
Authors: Liu Zhuming , Gu Wenqi
Published: December 2004

To develop a nano-lithography system based on scanning electron microscopy, a high-speed and high-precision deflection system including two prelens magnetic deflectors is introduced in this article. Best length ratio between two deflectors is achieved, which attributes to high sensitivity without loss of resolution. Some trade-off has been taken between aberrations and landing angle to get optimum performance of deflection system. The art of wire electron discharge machining is used to guarantee geometric accuracy and lower inductance. Frequency response test and lithographic experiments confirm the design.
Stress estimation of patterned films using a high-energy electron beam
Authors: Mizuno Fumio , Toshinawa Takumi
Published: December 2004

A scanning electron microscope using an electron beam with energy more than several tens of keV enables us to observe features that are concealed under the specimen surface. By use of this method, nondestructive and in-line stress estimation of patterned films on a production wafer can be made. This method has been applied to a photoresist pattern, and the results showed mechanical properties of the patterned resist film.
Plasma doping technology for fabrication of nanoscale metal-oxide-semiconductor devices
Authors: Cho Won-ju , Im Kiju , Ahn Chang-Geun , Yang Jong-Heon , Oh Jihun , Baek In-Bok , Lee Seongjae
Published: December 2004

We developed a plasma doping (PLAD) technique which is appropriate for the nanoscale metal-oxide-semiconductor field effect transistors (MOSFETs) fabrications. Silicon-on-insulator (SOI) n-MOSFETs with a 50-nm-length metal gate and a 100-nm-channel width were successfully fabricated. The source and drain extensions (SDE) of SOI n-MOSFETs were formed using a plasma doping technique. The advantage of this process is the exclusion of additional activation annealing after introduction of impurity in SDE, which resulted in a laterally abrupt source/drain (S/D) junction profile. We can obtain a low sheet resistance by the PLAD technique and low damaged shallow junctions. A trigate structure SOI n-MOSFET with a gate length of 50nm fabricated by high-temperature plasma doping revealed suppressed short-channel effects.
Alpha-prototype system for zone-plate-array lithography
Authors: Menon Rajesh , Patel Amil , Moon Euclid E. , Smith Henry I.
Published: December 2004

In this article, we present lithography results from a continuous-scan zone-plate-array lithography (ZPAL) system using the grating light valve (GLV) as the multiplexing element. ZPAL is an optical-maskless-lithography technique, in which an array of diffractive lenses (e.g., zone plates) focuses incident light into an array of spots on a photoresist-coated substrate. The intensity of the light incident on each lens is controlled by the GLV. By scanning the wafer and appropriately modulating the incident light, patterns are written in a “dot-matrix” fashion. We have incorporated the elements of ZPAL into an alpha-prototype system. We describe this system and characterize its lithographic performance.
Electron beam lithography for data storage: Quantifying the proximity effect as a function of CAD design and thin metal layers
Authors: Eckert Andrew , Mountfield Keith
Published: December 2004

We have characterized the e-beam proximity effect as it applies to the write pole break-point angle of magnetic recording heads. These narrow isolated negative resist lines have been measured using an automated CD-SEM. The CD data allows us to quantify the e-beam proximity effect on silicon wafers with thin metallic films of varying thickness. Nickel and tantalum have atomic numbers of 28 and 73, respectively, and this difference is quantified by the increase in the CD of the Ta films compared to Ni. The CD was found to change at a rate of 0.17nm per degree of break-point angle for the Ni films, and 0.25nm per degree for Ta. We have analyzed the experimental data by comparing it to two relevant models. First, we compare the data to the traditional expression used to describe e-beam exposure, a double Gaussian. From both the CD data and the double Gaussian, we calculate a proximity effect term we refer to as the dose fraction. This dose fraction has a linear relationship with the “eta” parameter, which also relates the contribution of forward to back scattered electrons in the final exposure profile. We determine both a dose fraction, and the “eta” parameter, for each substrate material and thickness. Second, we compare this dose fraction term to a simple Rutherford elastic scattering model. The final outcome of this work is a quantifiable measure of how the break-point angle contributes to the final CD of the write pole when employing e-beam lithography. This work also demonstrates a practical way to quantify the e-beam proximity effect by the calculation of dose fraction and “eta” as a metric of metal layer material and thickness.
Effect of fluoroalkyl substituents on the reactions of alkylchlorosilanes with mold surfaces for nanoimprint lithography
Authors: Chen Jem-Kun , Ko Fu-Hsiang , Hsieh Kuen-Fong , Chou Cheng-Tung , Chang Feng-Chih
Published: December 2004

We have applied trichloro(3,3,3-trifluoropropyl)silane (FPTS) and trichloro(1H,1H,2H, 2H-perfluorooctyl)silane (FOTS) for the preparation of self-assembled film on a silicon mold for use as releasing, antisticking layers for nanoimprint lithography. From contact angle measurements, we have determined the surface energies of the molds in terms of their Lewis acid, Lewis base, and van der Waals components. The surface energies of the FPTS- and FOTS-derived film decreased as the annealing temperature and immersion time increased. Suitable self-assembled films were prepared by annealing at 150°C for at least 1h. The surface roughnesses of the self-assembled film formed from FPTS and FOTS were 0.468 and 0.189nm, respectively. The lower surface energy and roughness of the FOTS-derived film on the silicon mold prevent both the adhesion and defect-formation problems from occurring during resist imprinting. The self-assembled films prepared on the mold are resistant to immersion in acid and base, but treatment with oxygen plasma has an adverse effect on these molds’ stabilities.
Fabrication and characterization of Au island single-electron transistors with CrOx step edge junctions
Authors: Luo Xiangning , Orlov Alexei O. , Snider Gregory L.
Published: December 2004

Single-electron transistors fabricated using Au islands and CrOx resistive microstrips are reported. To investigate the occurrence of Coulomb blockade in these devices, three types of device designs have been tested. Typical single-electron behavior, conductance modulation by the gate, is observed in the devices which had small overlap area with the gold island. Electron transport mechanism of CrOx resistors is discussed and a hypothesis of the formation of step edge junctions at the edges of granular metal microstrips is given as the explanation for the experimental results.
Assembled micro-electromechanical-systems microcolumn from a single layer silicon process
Authors: Saini R. , Jandric Z. , Tsui K. , Udeshi T. , Tuggle D.
Published: December 2004

We report a novel microcolumn fabrication method using automated micro-electro-mechanical-systems (MEMS) assembly. Different microcolumn components, including deflectors, lens elements, and apertures, are fabricated on a highly doped 50μm thick silicon-on-insulator (SOI) wafer. These components with compliant connectors are then assembled onto compliant MEMS sockets fabricated on the same wafer using MEMS NanoEffectors™ and automated assembly. The self-aligning nature of MEMS sockets yields submicron lateral alignment and less than 0.1° angular misalignment. The measured resonant frequency is 593Hz for first generation assembled components; the footprint of the microcolumn is less than 1cm2. We have successfully built a mechanical prototype microcolumn for technology demonstration and as a proof of concept. Second generation design is under development.
Ag metallization on silicides with nitride barriers
Authors: Mitan M. M. , Kim H. C. , Alford T. L. , Mayer J. W. , Malgas G. F. , Adams Daniel
Published: December 2004

The thermal stability of Ag thin films on Ti–O–N/silicides (CoSi2 and NiSi) is investigated with various characterization techniques in this study. A Ti–O–N film was used as a diffusion barrier for Ag metallization. Silicide thin films are prepared by solid phase reactions utilizing metal/silicon bilayer structure. Rutherford backscattering spectrometry (RBS) of annealed films reveals Ag film changes to occur at 650°C. Optical microscopy shows voids in the Ag film on the Ti–O–N diffusion barrier for temperature above 600°C. Increasing anneal temperature up to 700°C produces high density of voids in Ag films. Atomic force microscopy (AFM) shows the morphology of the voids that occur in the Ag film on the Ti–O–N barrier. RBS indicates some amount of Ag loss from the annealed samples at high temperatures. Secondary ion mass spectroscopy (SIMS) depth profiling reveals Ag diffusions to Ti–O–N/silicides/Si structures. We discuss the thermal stability and failure mechanism of Ag films on Ti–O–N/silicides/Si annealed at various temperatures.
Synthesis of tin-incorporated nanocomposite diamond like carbon films by plasma enhanced chemical vapor deposition and their characterization
Authors: Kundoo S. , Saha P. , Chattopadhyay K. K.
Published: December 2004

Sn-incorporated nanocomposite diamond like carbon (DLC) films were synthesized using direct current plasma enhanced chemical vapor deposition method. The precursor gas used was acetylene. For Sn incorporation, SnCl2∙2H2O dissolved in methanol was used. Fourier-transform infrared spectroscopy measurements showed different vibrational modes of tetrahedrally bonded carbon and also some small peaks due to SnC bonding vibrations. Transmission electron microscopy image and electron diffraction patterns also confirmed the incorporation of nanocrystalline Sn particles into the amorphous DLC matrix. Due to the presence of Sn clusters, the Tauc gap of the films decreased sharply, compared to the intrinsic material. It was found that the resistivity of Sn-incorporated DLC films decreased drastically (by eight orders of magnitude) compared to the undoped DLC film. Also, the films exhibited good field emission properties at a lower turn-on field.
Effects of applied voltages on planarization efficiency of Cu electropolishing
Authors: Chang Shih-Chieh , Wang Ying-Lang
Published: December 2004

Copper electropolishing (Cu-EP) was recently investigated to be a next generation technology for planarizing damascene copper interconnections. In this study, effects of applied voltages on microscaled planarization efficiency (PE) of Cu-EP are discussed. It was found that the initial polishing rate and the formation time of a viscous layer were crucial for the PE of Cu-EP because only a thin copper film should be removed. A higher polishing rate outside of a feature and a more resistive diffusion layer covered inside of a feature resulted in a higher step-height reduction on a copper film.
Low temperature growth of amorphous Si nanoparticles in oxide matrix for efficient visible photoluminescence
Authors: Ma L. B. , Ji A. L. , Liu C. , Wang Y. Q. , Cao Z. X.
Published: December 2004

We report a low temperature procedure for the fabrication of highly luminescent silicon nanoparticles in silicon-rich oxide films. A number density over 1012∕cm2 has been achieved for silicon particles of about 3nm in size by plasma-enhanced chemical vapor deposition at a substrate temperature of 30°C. Such deposits, when post-annealed at 500°C for 2 min, manifested a photoluminescence two orders of magnitude more intense than those samples grown at 250°C. Strong photoluminescence in the whole visible light range has been measured in samples prepared with this low-temperature procedure. The present results indicate the feasibility of fabricating silicon-based light-emitting devices with moderate processing temperatures.
Fabrication and properties of ultranano, nano, and microcrystalline diamond membranes and sheets
Authors: Reinhard D. K. , Grotjohn T. A. , Becker M. , Yaran M. K. , Schuelke T. , Asmussen J.
Published: December 2004

Thin diamond membranes and free-standing sheets are of interest for a variety of potential applications. This article describes the film nucleation, microwave plasma-assisted chemical-vapor-deposition synthesis, and subsequent processing steps required to make free-standing strong and flexible diamond foils of several cm2. Films are initially deposited on silicon wafers as ultrananocyrstalline, nanocrystalline, or microcrystalline diamond by varying selected deposition parameters including gas composition, nucleation, power, substrate temperature, and pressure. Subsequently the diamond is separated from the original substrate and applied either to new substrates or to frames. Diamond membranes and sheets with thickness between 1 and 3μm have been fabricated from each of these film types. The sheets are drapable and can be applied to curved surfaces and wrapped around cylinders. Properties of the films including optical transmission, Young’s modulus and fracture strength are described. Several examples of foils and associated frames and substrates are given.
Lithographic patterning of a highly metallized polymer resist system and pyrolytic or plasma treatment to afford ferromagnetic ceramics
Authors: Clendenning Scott B. , Manners I.
Published: December 2004

The highly metallized polymer cobalt-clusterized polyferrocenylsilane (Co-PFS) has been shown to act as a negative-tone resist for electron-beam lithography and UV-photolithography. Ferromagnetic ceramics containing Fe∕Co alloy nanoparticles result from subsequent pyrolysis or reactive ion etching in a secondary magnetic field.
Optimum dose for shot noise limited CD uniformity in electron-beam lithography
Authors: Kruit P. , Steenbrink S. , Jager R. , Wieland M.
Published: December 2004

To maximize the performance of an electron-beam lithography system the resist sensitivity must be chosen carefully. Very sensitive resists require only a low illumination dose, thus increasing the throughput. However, shot noise effects may give rise to unacceptable line edge roughness and variations in critical dimension (CD). In this study, the physical parameters which influence the effect of shot noise statistics on CD uniformity (CD-u) and linewidth roughness (LWR) are determined and an analytical model for CD-u and LWR is derived. It is found that the CD-u and LWR depend on the dose, the Gaussian beam probe size, the diffusion length dr of secondary electrons and acids in resist. The influence of background dose and non-shot-noise dose variations must also be taken into account. Monte Carlo simulations are performed to obtain the statistical variation of the two-dimensional solubility distribution of illuminated resist in a developer. The results of this simulation are used to validate the model. For the CD-u and the LWR, different expressions were found for describing the effect of the shot noise because, to describe the LWR, an extra factor must be incorporated to include the effect that spatial frequencies lower than 2 CDs do not have a contribution. Also, the area over which the dose must be integrated for the shot noise calculation is different for CD-u and LWR. For CD-u this area depends on dr∙CD, for LWR on dr2. From the model it can be concluded that shot noise has a significant effect on both the CD uniformity and the LWR and cannot be neglected in the optimization of the dose for high-throughput electron-beam lithography. With the specific relation between the current and the resolution of an e-beam tool, an expression for CD uniformity is found from which the throughput can be maximized for the required CD-u by optimizing the dose, probe size, and diffusion parameter. The background dose and the other dose variations are input parameters for such an optimization. For electron-beam systems with a typical resolution of 30nm and a required CD uniformity contribution of 3.5nm (3σ) due to all dose variations, a dose of 30μC∕cm2 is needed if 20% background and 3% (3σ) non-shot-noise dose variations are taken into account.
Electric-field-directed growth of carbon nanotubes in two dimensions
Authors: Nojeh Alireza , Ural Ant , Pease R. Fabian , Dai Hongjie
Published: December 2004

The interplay between mechanical and electronic properties in carbon nanotubes leads to interesting characteristics in devices such as a nanotube cross structure. The fabrication of nanotube devices has often been based on random growth or deposition of nanotubes and subsequently searching for those in desired locations with proper orientations. Obviously we want to be able to make such devices controllably. We present data on extending the technique of one-dimensional alignment of nanotubes using electric field to two dimensions in order to make more complicated structures such as nanotube crosses. It appears that nanotubes assemble in the regions of the most intense electric field. Also, they tend to follow the local field lines, even in nonuniform fields. Furthermore, they tend to grow away from negative toward positive polarities.
Probe shape measurement in an electron beam lithography system
Authors: Liddle J. Alexander , Naulleau Patrick , Schmid Gerard
Published: December 2004

We have devised a method of quantifying the size and shape of the probe in a Gaussian-beam lithography system. The technique is robust, being insensitive to noise, but is sensitive to changes in the probe size of as little as ±0.5nm. We have determined that the probe shape of our system is indeed well fit by a Gaussian, with a best-focus full-width half-maximum of 6.5±1nm. We are able readily to quantify the effects of astigmatism on the system. In addition, the approach we describe can be extended to deal with arbitrary point-spread functions.
Evaluation of outgassing from a fluorinated resist for 157nm lithography
Authors: Irie Shigeo , Hagiwara Takuya , Fujii Kiyoshi , Itakura Yasuo , Kawasa Youichi , Egawa Keiji , Uchino Ikuo , Sumitani Akira , Itani Toshiro
Published: December 2004

We have evaluated the outgassing products and the in situ transmittance of a contaminated CaF2 substrate for monocyclic fluoropolymers with four protecting groups: methoxymethyl (MOM), tert-butoxycarbonyl (t-BOC), menthoxymethyl, and 2-cyclohexylcyclohexyloxymethyl. We found little correlation between the total amount of outgassing from the polymer and the decreasing rate of the CaF2 substrate transmittance caused by outgassing adhesion. Although the MOM protecting group generated the largest amount of outgassing products, the most substantial decrease in the transmittance was observed for the t-BOC protecting group. Therefore, the absorption coefficient of the outgassing-contaminated CaF2 substrate appears to be more sensitive to the type of protecting group, especially the t-BOC protecting group including a t-butyl unit. We conclude that in terms of material design of the fluoropolymer resist for 157nm lithography, we need to pay attention to the protecting group of polymers, especially the protecting group including a t-butyl unit, which generates isobutene product during 157nm irradiation.
Lithographically directed deposition of silica nanoparticles using spin coating
Authors: Xia Deying , Brueck S. R. J.
Published: December 2004

Directed self-assembly is an important direction for the extension of patterning to the nanoscale regime and below. Here, examples are given of both individual particle placement and composite structure formation involving assemblies of many nanometer scale particles, both on patterned surfaces and on planar surfaces where the photoresist is used as a sacrificial layer to define the pattern and is subsequently removed. The underlying technologies employed in these experiments include interferometric lithography to define large-area, nanometer-scale patterns and directed self-assembly by spin coating to control particle placement. Three sizes of silica nanoparticles (mean diameters: 78, 50, and 15nm) were employed for spin-coating processes. Single linear silica particle chain patterns and isolated two-dimensional particle patterns were easily formed on patterned surfaces. Silica particle rows, cross networks, and isolated posts with controllable thickness could be formed on flat surfaces using this approach. Directed self-assembly using nanoscale lithography and spin coating is a facile approach to the extension of lithographic techniques to the nanoscale.
Pinning effect of microliquid drop on geometrical complex substrates composed with different surface energy materials
Authors: Yamanaka Masaki , Okada Akira , Kawai Akira
Published: December 2004

Wetting behavior of microliquid drop on a geometrical complex substrate is analyzed quantitatively. In order to analyze pinning effect in liquid spreading, the array of isolated square patterns is formed by the photolithography. The square patterns on flat substrate are composed with the combination of higher and lower surface energy materials. Two types of complex substrates, isolated polar and continuous polar patterns, are fabricated. The test liquids, de-ionized water, ethylene glycol and diiodomethane, are sessile dropped on the complex substrate. Particularly, the isolated polar pattern acts to pin the polar liquid spreading. The combination of a polar liquid and an isolated polar substrate has strong interaction on each other. However, in the case of the continuous polar pattern, the wetting behavior of liquid drop can be explained due to Cassie’s equation. The contribution of the polar material to the wetting property on geometrical complex substrate can be clarified.
GaAs
-based 1.3μm microlasers with photonic crystal mirrors
Authors: Scherer H. , Gollub D. , Kamp M. , Forchel A.
Published: December 2004

We present results of GaAs-based microlasers with photonic crystal mirrors. The lasers are fabricated from GaAs∕AlGaAs layer structures with a doub1e GaInNAs quantum well emitting at 1.3μm wavelength. The devices are realized as ridge waveguide lasers with two coupled cavities and a total length between 175 and 600μm. Photonic crystals are used to define the front and back mirrors of the lasers. Threshold currents around 40mA and output power levels of 80mW were achieved. Single-mode emission with 30dB side-mode suppression ratio is obtained due to mode interference between the two cavities.
Modeling and simulation of chemically amplified electron beam, x-ray, and EUV resist processes
Authors: Kozawa Takahiro , Saeki Akinori , Tagawa Seiichi
Published: December 2004

With the shrinkage of feature sizes, ever precise accuracy has been required for process simulators because of the importance of nanoscale resist topography such as line edge roughness. Formation processes of latent images in chemically amplified electron beam (EB), x-ray, and EUV resists are different from both chemically amplified photoresists used in optical lithography and conventional, nonchemically amplified EB resists. A new simulation scheme precisely based on reaction mechanisms is necessary to reproduce resist patterns for the postoptical lithographies. We proposed a method to simulate electron dynamics in chemically amplified resists and to calculate the acid distribution around an ionization point with a typical parameter set.
Sub-100 nm lithography using ultrashort wavelength of surface plasmons
Authors: Srituravanich W. , Fang N. , Durant S. , Ambati M. , Sun C. , Zhang X.
Published: December 2004

The development of a nanolithography technique utilizing ultrashort wavelength of surface plasmons (SPs) is presented in this article. The mask consists of silver thin film perforated with two-dimensional hole arrays exhibiting superior confinement due to SPs with a wavelength equal to 14 of that of the illuminating light (365 nm). This short wavelength of SPs can confine the field on an area much smaller compared to the excitation light wavelength, leading to the higher resolution lithography than conventional photolithography methods. Finite-difference time-domain simulations show significantly enhanced electric field and tight confinement of the near-field profile obtained from silver plasmonic masks, where features as small as 30 nm can be resolved. Furthermore, the lithography experiments have been performed with demonstration of sub-100 nm spatial resolution.
Fabrication of diamond-like amorphous carbon cantilever resonators
Authors: Chua Daniel H. C. , Milne W. I. , Sheeja D. , Tay B. K. , Schneider D.
Published: December 2004

Amorphous carbon (a-C) films were deposited by an off-plane double bend filtered cathodic vacuum arc technique fitted with a plasma immersion ion implantation system. High resolution XPS measurements showed these films have an sp3 content of about 60%. Laser-surface acoustic wave measurements have shown such films to have a Young’s modulus and density of 310GPa and 2.33g∕cm3. 1.2μm thick a-C films were grown and subsequently patterned into 150μm×50μm cantilevers using standard photolithography. Residual stress measurements were obtained from the curvature of bend of the cantilever. An accurate knowledge of the microstructural properties will in turn give accurate modeling results. Simulation results showed that such free-standing cantilevers fabricated with amorphous carbon films have resonant frequency much higher than standard polysilicon cantilevers. As such, free-standing diamond-like amorphous carbon cantilevers had been fabricated. The resonant frequency of these cantilevers was measured by laser vibrometer to be ∼108MHz, in very good agreement with simulation results.
High aspect ratio pattern transfer in imprint lithography using a hybrid mold
Authors: Liao Wen-Chang , Hsu Steve Lien-Chung
Published: December 2004

A new method has been developed to obtain high aspect ratio patterns transfer by using a combination of imprint lithography and photolithography through a hybrid mold on a flexible transparent plastic substrate. The hybrid mold was fabricated by optical lithography and wet etching of a commercial blank template containing photoresist, chromium and transparent glass. Etching barrier used in this method was a negative photoresist with a low softening point to achieve the pattern transfer on a flexible plastic substrate. After imprinting and the following development by an aqueous Na2CO3 solution, high aspect ratio patterns contributed by imprint and mask were successfully transferred. Using this method, we were able to obtain the desired high aspect ratio patterns on the plastic substrate without using expensive or specific photoresists. It was also easy to remove the residual layer that usually has to be treated by reactive ion etching (RIE) in conventional imprinting process.
Silicon nitride gate dielectric for top-gated carbon nanotube field effect transistors
Authors: Li Shengdong , Yu Zhen , Burke Peter J.
Published: December 2004

We develop and demonstrate a process to fabricate top-gated carbon nanotube transistors using silicon nitride as the gate dielectric. I-V curves of these silicon nitride gated nanotube transistors are measured.
Process development and characterization of antisticking layers on nickel-based stamps designed for nanoimprint lithography
Authors: Keil M. , Beck M. , Frennesson G. , Theander E. , Bolmsjö E. , Montelius L. , Heidari B.
Published: December 2004

Thin films of different derivatives of fluorinated alkyl phosphoric acids have been deposited from aqueous solutions onto surfaces of oxidized polycrystalline nickel stamps, which are commonly used in several industrial applications of nanoimprint lithography (NIL). The films have been established in order to increase the antiadhesion tendencies at the stamp polymer interface. Thicknesses, chemical compositions, and purities of the films as well as binding mechanisms to the stamp surfaces have been determined by photoelectron spectroscopy (XPS). The results demonstrate the adsorption of highly pure films having thicknesses in the monomolecular region, whose chemical compositions are characterized by large ratios of fluorinated to nonfluorinated carbon species. The high ionic nature of Ni-oxide benefits strong ionic linkages between the phosphate groups of the fluorinated antisticking film and the stamp surface, allowing a large-scale production of imprints with patterned stamps having feature sizes down to 100 nm.
High resolution lithography with PDMS molds
Authors: Bender M. , Plachetka U. , Ran J. , Fuchs A. , Vratzov B. , Kurz H. , Glinsner T. , Lindner F.
Published: December 2004

The resolution, dimension stability, and reproducibility of the Soft UV-Nanoimprint is investigated. The potential for imprinting nanostructures with flexible molds in UV-curable resists in the 100nm regime are explored and the limitations analyzed. The dimensional stability of imprinted patterns is determined by the deformation of the mold that in term depends on the geometry of the structures and the imprint pressure applied.
Representation of nonrectangular features for exposure estimation and proximity effect correction in electron-beam lithography
Authors: Lee S.-Y. , Hu F. , Ji J.
Published: December 2004

In most proximity effect correction schemes, circuit features are assumed to be rectangular. However, there are many circuit patterns which contain nonrectangular shapes of features such as circles, circular arcs, polygons, etc. In this article, efficient ways to handle such features for exposure estimation required in proximity effect correction are proposed. A hierarchical approach, where a nonrectangular feature is partitioned into correction shapes first, and then each correction shape may be further decomposed into exposure shapes if necessary, is taken in order to develop efficient and generally applicable schemes. Specifically, for exposure estimation, four schemes (direct, slicing, hybrid, and coordinate transformation methods) are described, of which performances have been analyzed through an extensive simulation.
Comparison of tilting and piston mirror elements for 65nm node spatial light modulator optical maskless lithography
Authors: Watson G. P. , Aksyuk V. , Tennant D. M. , Cirelli R. A.
Published: December 2004

Spatial light modulator (SLM) maskless lithography, an optical technology that replaces photomasks with an adjustable array of microelectromechanical mirrors can potentially complement conventional, mask-based, lithography. The usefulness of this technology depends on whether it can print features at least as well as conventional tools and can keep pace with the International Technology Roadmap for Semiconductors. In particular, any SLM-based tool developed now must be capable of printing 50nm or smaller gates and 130nm pitch lines and spaces using 193nm light as is being planned for the 65nm half-pitch node. SLM mirrors may be designed to tilt or shift in depth (piston). Aerial image simulations presented here show that 65nm node features formed by piston mirrors have the same process latitude as tilt mirrors with a numerical aperture (NA) of 1.1. In addition, piston mirrors exhibit the added benefit that they may be arranged to mimic alternating aperture phase shift photomasks. Isolated and dense features of 65nm node dimensions can be printed with a reduced NA of 0.90. This form of phase shifting may be required at the 65nm ITRS node both for conventional and maskless lithography applications.
Gated photocathode arrays as sources for multibeam electron nanolithography
Authors: McCarthy Jack , Simonson Ron
Published: December 2004

Multiple electron beams will need to expose large areas of resist in parallel rapidly if maskless electron lithography of high-density nanoscale structures is to become a production tool. This will require large arrays of gated submicron scale sources for multiple beams with gate changeable currents. In this research and development a small 3×3 array was fabricated using a computer controlled focused ion beam milling machine (FIB). This gated array electron source was tested first in a vacuum chamber without optics to test the operation of the gates in preparation for installation in a column with electrostatic lenses, stigmation, steering, scanning and secondary electron imaging. A primary goal for the project is the exposure of nanoscale lines in resist. The fabrication of a 3×3 test array used a combination of sputter deposition, FIB microforming and micromachining of the necessary metals and insulators. The photoemitting film for each of the gated sources was a FIB deposited 15 nm thick layer of Pt. The initial tests on these gated photocathodes are encouraging, by changing the gate voltage we can change the photoemission current. In addition to the work on the fabrication of the gated arrays, blanket thin film materials are being tested for stability and photoyield for possible use in the gated arrays. In this work a range of thicknesses of glow discharge carbon was deposited on the Ti coated substrates. The 20 nm thick carbon film produced the best performance, a stable 7nA∕mW photoyield. Carbon photocathodes 15 nm, 30 nm, and 60 nm thicknesses were stable but lower at 3.7, 3.6, and 1.3nA∕mW, respectively. A new experimental chamber is currently under construction to allow us to investigate the feasibility of using our gated photocathode arrays to expose PMMA or other suitable electron sensitive resist materials. The photoelectron column is made from a modified FEI 600 series FIB column.
Effects of flare in extreme ultraviolet lithography: Learning from the engineering test stand
Authors: Chandhok Manish , Lee Sang H. , Bacuita Terence
Published: December 2004

One of the technical challenges for introducing extreme ultraviolet lithography (13.5 nm) into high volume manufacturing is flare. Flare reduces aerial image contrast and creates critical dimension (CD) variations across the die due to local chrome density dependent flare variations. Therefore, it is important to experimentally characterize flare on a full-field stepper and develop methods to mitigate and compensate for its effects. In this article, the impact of flare on depth of focus and exposure latitude are experimentally quantified using the engineering test stand. In addition, we report a marked increase in line width roughness due to high levels of flare in the optical system. A technique for the extraction of the point spread function due to scatter using density dependent CD data has been demonstrated for more accurate flare variation compensation.
Hydrogen in Si–Si bond center and platelet-like defect configurations in amorphous hydrogenated silicon
Authors: Agarwal Sumit , Hoex Bram , van de Sanden M.C.M. , Maroudas Dimitrios , Aydil Eray S.
Published: December 2004

Hydrogen and deuterium in bond-centered (BC) and platelet-like configurations were detected in hydrogenated (and deuterated) amorphous silicon thin films deposited from SiH4 and SiD4 plasmas. Infrared absorptions due to these configurations were measured using in situ multiple total internal reflection Fourier transform infrared spectroscopy in a differential mode, where changes in the as-deposited a-Si:H(D) films were observed during D2(H2) plasma exposure. This method coupled with preferential replacement of H(D) by D(H) in BC and platelet-like configurations over the isolated bulk SiH(SiD) configurations enabled detection of these modes without interference from the strong SiH(SiD) absorptions. The Si–H(D) stretching modes for BC hydrogen and BC deuterium were observed at ∼1950 and ∼1420cm−1, respectively, while those for platelet-like hydrogen and deuterium were detected at ∼2033 and ∼1480cm−1, respectively.
3D proximity effect correction based on the simplified electron energy flux model in electron-beam lithography
Authors: Osawa Morimi , Ogino Kozo , Hoshino Hiromi , Machida Yasuhide , Arimoto Hiroshi
Published: December 2004

We have confirmed the adequacy of simplified electron energy flux (SEEF) model which can be used in proximity effect correction (PEC) in electron beam lithography. The SEEF model enables calculation of the backscattering energy in a multiwiring structure by obtaining a transmission and reflection energy flux map. We prepared a substrate which contained three pairs of W-plug layers and inter-metal dielectric (IMD) layers, and obtained parameters for correction. The extracted transmittance and reflectance were 1 and 0 for the dielectrics, and 0 and 1.7 for the W plugs. The backscattering energies calculated by using these parameters corresponded with experimental data under the various conditions. We also extracted the scattering range of incident and reflected electrons in dielectrics. We found that the ranges of the reflected electrons were greater than those of the incident electrons because of a wider spread of angle. PEC based on the SEEF model enabled high CD accuracy even at the end of the W-plug area. We thus confirmed that the SEEF model can accommodate complex effects, such as scattering in a multiwiring structure or the screening effect, by following the electron’s path.
Direct imprint of sub-10nm features into metal using diamond and SiC stamps
Authors: Lister K. A. , Thoms S. , Macintyre D. S. , Wilkinson C. D. W. , Weaver J. M. R. , Casey B. G.
Published: December 2004

We demonstrate the transfer of sub-10nm features into nickel using a hard stamp. Nanostructures were transferred directly from diamond and SiC in a single step by pressing the stamp into nickel at room temperature. The patterns were generated using ultrahigh resolution electron beam lithography. Patterns were transferred to the diamond and SiC using RIE etching with an O2 plasma used for the diamond and a SF6+O2 mixture used for the SiC. Hydrogen Silsesquioxane was used as a resist and served as a mask in the plasma etching.
Formation of 15nm scale Coulomb blockade structures in silicon by electron beam lithography with a bilayer resist process
Authors: Park S.-J. , Liddle J. A. , Persaud A. , Allen F. I. , Schenkel T. , Bokor J.
Published: December 2004

We have formed Coulomb blockade structures with widths of 15–30nm in silicon-on-insulator (SOI) by electron beam lithography (EBL) in a bilayer resist process. The bilayer structure consisted of HSQ (hydrogen silsesquioxane) and AZ organic resist. The organic resist protects the buried oxide and allows removal of exposed HSQ features with hydrofluoric acid (HF). Measurements at 4.2K show pronounced Coulomb blockade signatures for 15nm wide wires. This bilayer resist process provides direct lithographic access to 15nm level features in SOI without the need for size reduction by oxidation.