Showing papers on "Electron-beam lithography published in 2000"
TL;DR: In this article, the authors report on the resolution limits of EBL in the conventional polymethylmethacrylate (PMMA) organic resist and show that resolution can be pushed below 10 nm for isolated features and dense arrays of periodic structures can be fabricated at a pitch of 30 nm, leading to a density close to 700 Gbit/in2.
1,017 citations
TL;DR: Although the introduction of shorter-wavelength light sources and resolution-enhancement techniques should help maintain the current rate of device miniaturization for several more years, a point will be reached where optical lithography can no longer attain the required feature sizes.
Abstract: The phenomenal rate of increase in the integration density of silicon chips has been sustained in large part by advances in optical lithography--the process that patterns and guides the fabrication of the component semiconductor devices and circuitry. Although the introduction of shorter-wavelength light sources and resolution-enhancement techniques should help maintain the current rate of device miniaturization for several more years, a point will be reached where optical lithography can no longer attain the required feature sizes. Several alternative lithographic techniques under development have the capability to overcome these resolution limits but, at present, no obvious successor to optical lithography has emerged.
764 citations
TL;DR: In this paper, the nano-print process is done in a single layer as well as in a multilayer resist scheme with subsequent O2-plasma etching and metal lift-off.
Abstract: We demonstrate the nanoimprint lithography (NIL) technique with sub 100 nm resolution, on 6 in. Si substrates. The pattern transfer is performed using a specially designed NIL machine optimized to achieve a very high degree of parallelism between stamp and substrate. The stamp is made with the help of electron beam lithography and Ni electroplating achieving features below 100 nm in size. The nanoimprint process is done in a single layer as well as in a multilayer resist scheme with subsequent O2-plasma etching and metal lift-off.
207 citations
TL;DR: In this article, the magnetic properties of permalloy nanodisks were studied by Lorentz transmission electron microscopy and it was shown that the vortex configuration is the most favorable state in zero field conditions of all investigated permalloys.
Abstract: Circular permalloy elements were fabricated by a combination of electron beam lithography, thermal evaporation and liftoff technique on electron transparent membrane substrates. The magnetic properties have been studied by Lorentz transmission electron microscopy. In situ magnetizing experiments have been carried out to obtain information about the nucleation and propagation of magnetic domains within the permalloy nanodisks and to determine the nucleation and saturation fields. The diameter of the patterned elements has been varied between 180 and 950 nm, the height was 15 nm. The experiments showed that the vortex configuration is the most favorable state in zero field conditions of all investigated permalloy nanodisks.
160 citations
TL;DR: In this paper, the fabrication of Fresnel zone plates with a 75 nm minimum feature size and circular gratings with a 20 nm minimum linewidth in polymethyl methacrylate using nanoimprint lithography, and in metals by means of a lift-off technique was demonstrated.
Abstract: We demonstrated the fabrication of Fresnel zone plates with a 75 nm minimum feature size and circular gratings with a 20 nm minimum linewidth in polymethyl methacrylate using nanoimprint lithography, and in metals by means of a lift-off technique. Observation of sharp Moire patterns indicated the high fidelity of nanoimprint lithography in pattern duplication. Our results showed that nanoimprint lithography is a promising technology for patterning integrated optics.
149 citations
TL;DR: A bilayer resist system consisting of hydrogen silsesquioxane (HSQ) as negative tone electron (e)-beam resist top coat and hard baked novolak resist as bottom coat, has been investigated for its ability to yield high aspect ratio nanoscale structures as mentioned in this paper.
Abstract: A bilayer resist system, consisting of hydrogen silsesquioxane (HSQ) as negative tone electron (e)-beam resist top coat and hard baked novolak resist as bottom coat, has been investigated for its ability to yield high aspect ratio nanoscale structures. For comparison, single layer HSQ (hard mask) has been investigated for its resolution, contrast, and process latitude. In single layer HSQ, dense lines and spaces (1:1) have been resolved down to 20 nm and single lines have been obtained with widths less than 15 nm. Processing conditions which result in higher contrasts in HSQ also result in higher horizontal contrasts, i.e., in poorer process latitudes; this effect has previously been observed for other negative tone e-beam resists as well. In the bilayer combination, HSQ allows nanoscale structures with an aspect ratio exceeding 15 to be etched in hard baked novolak resist. Single lines with 800 nm height and 40 nm width, semidense lines and spaces (1:2) with 155 nm height and 25 nm width, and dense lines...
131 citations
TL;DR: In this paper, a diffractive Fresnel zone plate lens was used for short wavelength x-ray radiation microscopy at the Advanced Light Source Synchrotron in Berkeley, California.
Abstract: Short wavelength x-ray radiation microscopy is well suited for a number of material and life science studies. The x-ray microscope (XM1) at the Advanced Light Source Synchrotron in Berkeley, California uses two diffractive Fresnel zone plate lenses. The first is a large condenser lens, which collects soft x-ray radiation from a bending magnet, focuses it, and serves as a linear monochromator. The second is the objective zone plate lens, which magnifies the image of the specimen onto a high-efficiency charge coupled device detector. The objective lens determines the numerical aperture and ultimate resolution. New objective lens zone plates with a minimum linewidth of 25 nm and excellent linewidth control have been fabricated using Berkeley Lab’s 100 keV Nanowriter electron beam lithography tool, a calixarene high-resolution negative resist, and gold electroplating. Although the condenser zone plate is less critical to the resolution of the instrument, its efficiency determines the flux on the sample and ul...
129 citations
TL;DR: In this paper, the fabrication of gold nanostructures using self-assembled monolayers of aliphatic and aromatic thiols as positive and negative electron beam resists is presented.
Abstract: We show the fabrication of gold nanostructures using self-assembled monolayers of aliphatic and aromatic thiols as positive and negative electron beam resists. We applied a simple and versatile proximity printing technique using focused ion beam structured stencil masks and low energy (300 eV) electrons. We also used conventional e-beam lithography with a beam energy of 2.5 keV and doses from 3500 to 80 000 μC/cm2. Gold patterns were generated by wet etching in KCN/KOH and characterized by atomic force microscopy and scanning electron microscopy. The width of the finest lines is ∼20 nm; their edge definition is limited by the isotropic etching process in the polycrystalline gold.
129 citations
TL;DR: In this paper, a single-electron transistor that shows gate modulation at room temperature was presented, and the charge-equivalent noise of the device at 300 K was measured to be ∼4×10−2 ǫe/Hz1/2 at 1 Hz and is expected to be 1000 times lower in the white-noise regime at higher frequencies.
Abstract: We present a lithographically made Al single-electron transistor that shows gate modulation at room temperature. The temperature dependence of the modulation agrees with the orthodox theory, however, energy-level quantization in a tiny metallic island affects the device characteristics below 30 K. The charge-equivalent noise of the device at 300 K was measured to be ∼4×10−2 e/Hz1/2 at 1 Hz and is expected to be 1000 times lower in the white-noise regime at higher frequencies.
116 citations
TL;DR: In this paper, a site-control technique for InAs quantum dots (QDs) on GaAs substrates using a combination of in situ electron-beam (EB) lithography and self-organized molecular-beam epitaxy was studied.
Abstract: We studied a site-control technique for InAs quantum dots (QDs) on GaAs substrates using a combination of in situ electron-beam (EB) lithography and self-organized molecular-beam epitaxy. In small, shallow holes formed on prepatterned mesa structures by EB writing and Cl2 gas etching, QDs were selectively formed, without any formation on the flat region between the patterned holes. The density of the QDs in each hole was dependent on the hole depth, indicating that atomic steps on the GaAs surfaces act as migration barriers to In adatoms. In an array of holes including 5–6 monolayer steps, a single QD was arranged in each hole.
102 citations
TL;DR: The thermal, chemical, and mechanical stability of Pt nanoparticles supported on silica has been measured with transmission electron microscopy and atomic force microscopy (AFM) as discussed by the authors.
Abstract: The thermal, chemical, and mechanical stability of Pt nanoparticles supported on silica has been measured with transmission electron microscopy (TEM) and atomic force microscopy (AFM). The nanoparticle arrays were fabricated using electron beam lithography, which produced uniform particle sizes (20 ± 1 nm) and uniform interparticle distances (150 ± 1 nm). TEM studies provided information about the array periodicity, particle dimensions, and crystallinity of individual particles. Before heat treatments, individual Pt nanoparticles were found to be polycrystalline with crystalline domain sizes of 4−8 nm. After heating to 1000 K in high vacuum (10-7 Torr) and 1 atm H2, the crystalline domain sizes within individual particles grew larger, without noticeable deformation of the array. A similar enlargement of crystalline domains was seen in 1 atm O2 at a lower temperature of 700 K. Using contact mode AFM, the height, periodicity, and adhesion of the particles were determined. On a newly prepared sample, Pt part...
TL;DR: In this paper, the critical aspect ratio of collapse (CARC) as a function of spacing between resist structures was determined for photoresist features with linewidths from 80 to 200 nm, spacing from 100 to 350 nm, and aspect ratios from 2 to 6 for four different resist platforms: acrylic based resist, acrylic resists based upon the Fujitsu platform, cyclo-olefin-maleic anhydride based resists, and Apex E, a poly(hydroxystyrene) based resist.
Abstract: A comparison of collapse behavior was made for photoresist features with linewidths from 80 to 200 nm, spacing from 100 to 350 nm, and aspect ratios from 2 to 6 for four different resist platforms: acrylic based resists, acrylic resists based upon the Fujitsu platform, cyclo-olefin–maleic anhydride based resists, and Apex E, a poly(hydroxystyrene) based resist. The percentage of collapse for different gratings was determined using top-down scanning electron microscope images. A methodology was introduced to compare collapse properties between platforms by determining the critical aspect ratio of collapse (CARC) as a function of spacing between resist structures. We demonstrated the validity of this approach using an extensive set of statistically significant data for Apex E, and we determined that the CARC decreased linearly as the spacing between lines of resist decreased. The physical origin of the approach was discussed in terms of the mechanics of beam bending and the thermodynamics of surface tension. The methodology was applied to limited data sets for other resist platforms. The four resist platforms exhibited different values of CARC at constant spacing and a different dependence of CARC as a function of spacing. Resist performance in terms of collapse properties was ranked in the following order: cyclo-olefin–maleic anhydride resists > poly(hydroxystyrene) resist and acrylic resists based on the Fujitsu platform > acrylic resists.
TL;DR: In this paper, a method for integrating an isolated cell membrane patch into a semiconductor device was presented, where the semiconductor is nanostructured for probing native cell membranes for scanning probe microscopy in situ.
Abstract: We present a method for integrating an isolated cell membrane patch into a semiconductor device. The semiconductor is nanostructured for probing native cell membranes for scanning probe microscopy in situ. Apertures were etched into suspended silicon-nitride layers on a silicon substrate using standard optical lithography as well as electron-beam lithography in combination with reactive ion etching. Apertures of 1 μm diam were routinely fabricated and a reduction in size down to 50 nm was achieved. The stable integration of cell membranes was verified by confocal fluorescence microscopy in situ.
11 Jul 2000
TL;DR: In this article, the authors evaluated and optimized the ultra-high resolution and overlay performance of a Leica EBPG-5000 TFE electron beam lithography system for 3D-device integration.
Abstract: For advanced nanoelectronic device concepts bridging the extended CMOS-world with the ultimate solution of single electron transistors (SETs), reliable lithography in the 10 nm (decanometer) regime has gained top priority in the past. Additionally, any type of nanoscopic 3D-device integration requires an overlay accuracy on the few-nm level. There is, however, a discrepancy between minimum feature sizes and overlay performance usually obtained with current electron beam lithography systems. We have evaluated and optimized the ultra-high resolution and overlay performance of a Leica EBPG-5000 TFE electron beam lithography system.
TL;DR: In this article, a shadow mask method was used to fabricate electrodes with nanometer scale separation, which can be extended to gap sizes of 1 nm and even more than 20 nm.
Abstract: We present a simple shadow mask method to fabricate electrodes with nanometer scale separation. Metal wires with gaps are made by incorporating multiwall carbon nanotubes or single-wall carbon nanotube (SWNT) bundles into a trilayer electron beam lithography process. The simple, highly controllable, and scaleable method has been used to make gaps with widths between 20 and 100 nm and may be extended to gap sizes of 1 nm. We report electron transport measurements of individual SWNTs bridging nanogaps with electrode spacings of approximately 20 nm. Metallic SWNTs exhibit quantum dot behavior with an 80 meV charging energy and a 20 meV energy level splitting. We observe a strong field effect behavior in short semiconducting SWNT segments, evidence for diffusive electron transport in these samples.
TL;DR: In this article, a multilevel surface-relief-type diffractive optical elements are designed which are capable of generating a large number of Gauss-Laguerre modes with arbitrary mode indices in different diffraction orders of the element.
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29 Nov 2000TL;DR: In this paper, a shadow mask method to fabricate electrodes with nanometer scale separation utilizes nanotubes (NTs), which can be used to make gaps with widths between 1 and 100 nm.
Abstract: A shadow mask method to fabricate electrodes with nanometer scale separation utilizes nanotubes (NTs). Metal wires with gaps are made by incorporating multi-wall carbon nanotubes (MWNTs) or single-wall carbon nanotubes (SWNTs) (or bundles thereof) into a tri-layer electron beam lithography process. The simple, highly controllable, and scaleable method can be used to make gaps with widths between 1 and 100 nm. Electronic transport measurements performed on individual SWNTs bridge nanogaps smaller than 30 nm. Metallic SWNTs exhibit quantum dot behavior with an 80 meV charging energy and a 20 meV energy level splitting. Semiconducting SWNTs show an anomalous field effect transistor behavior.
21 Jul 2000
TL;DR: In this article, a new multi-beam concept employing multiple columns each with multiple beams to generate a very large total number of parallel writing beams was discussed, which overcomes the limitations of space-charge interactions and low voltage operation.
Abstract: Electron beam lithography systems have historically had low throughput. The only practical solution to this limitation is an approach using many beams writing simultaneously. For single-column multi-beam systems, including projection optics (SCALPELR and PREVAIL) and blanked aperture arrays, throughput and resolution are limited by space-charge effects. Multibeam micro-column (one beam per column) systems are limited by the need for low voltage operation, electrical connection density and fabrication complexities. In this paper, we discuss a new multi-beam concept employing multiple columns each with multiple beams to generate a very large total number of parallel writing beams. This overcomes the limitations of space-charge interactions and low voltage operation. We also discuss a rationale leading to the optimum number of columns and beams per column. Using this approach we show how production throughputs >= 60 wafers per hour can be achieved at CDs
TL;DR: In this article, the use of electron beam lithography (EBL) techniques to produce novel diffractive optical microstructures for use as anti-counterfeiting devices is discussed.
TL;DR: In this article, a multielectron-beam optical system with correction lens array (CLA) is proposed, which can generate plural intermediate images of the electron source as a multisource, and moreover can compensate field curvature and distortion of the reduction optics.
Abstract: A new multielectron-beam optical system with correction lens array (CLA) is proposed. The CLA is arranged between an electron source and reduction optics. The CLA can generate plural intermediate images of the electron source as a multisource, and moreover can compensate field curvature and distortion of the reduction optics. The proposed system was designed and optimized through simulations. The specifications are field size of 250 μm square, convergence beam angle of 10 mrad, 64×64 beams, individual beam size of φ25 nm, accelerating voltage of 50 kV, and demagnification ratio of 50. The practical resolution for various resist processes is estimated considering the Coulomb interaction effect, and the throughput is simulated. The proposed system offers the possibility of “maskless” electron beam lithography with throughput in excess of 50 wafers/h (8 in.) for the International Technology Roadmap for Semiconductors (ITRS) 100 nm and 70 nm nodes at 3 μC/cm2 resist sensitivity.
TL;DR: A silicon quantum wire transistor, in which electrons are transported through a very narrow wire, has been fabricated using silicon-on-insulator technology, electron beam lithography, anisotropic dry etching, and thermal oxidation as discussed by the authors.
Abstract: A silicon quantum wire transistor, in which electrons are transported through a very narrow wire, has been fabricated using silicon-on-insulator technology, electron beam lithography, anisotropic dry etching, and thermal oxidation. We have obtained the quantum wire with a width of 65 nm, which is fully embedded in silicon dioxide. This narrow dimension of the wire and large potential barrier between silicon and silicon dioxide make the electrons moving through the wire experience one-dimensional confinement. The step-like structure in the conductance versus gate voltage curve, which is a typical evidence of one-dimensional conductance, has been observed at temperatures below 4.2 K. A period of step appearance and a step size have been analyzed to compare experimental characteristics with theoretical calculation.
TL;DR: In this paper, a multilayer mask with an amorphous carbon layer as a key component is used to fabricate nanostructures in oxide materials, especially YBa2Cu3O7−x (YBCO) thin films.
Abstract: We have developed a process to fabricate nanostructures in oxide materials, especially YBa2Cu3O7−x (YBCO) thin films. The fabrication process is based on a multilayer mask with an amorphous carbon layer as a key component. Electron-beam lithography, reactive ion etching, and ion-beam etching have been the supporting techniques for the process. Nanobridges ranging in width from 50 to 170 nm have been fabricated and characterized. The initial YBCO film was 50 nm thick and had a Tc of 86 K. Tc of the fabricated bridges decreased about 3–5 K with respect to the initial film. The level of the critical current density was 4–9×105 A/cm2 at 77 K and 1.6–2×107 A/cm2 at 4.2 K. No increase of the critical current density was observed as the cross-section area became smaller. The process has also been applied to fabricate 30–50 nm wide trenches in a-axis-oriented YBCO on top of a similar-oriented PrBa2Cu3O7−x (PBCO) layer. No supercurrent was observed in such junctions. The current transport was governed by Mott variable range hopping.
TL;DR: In this paper, the authors describe the electron optical column used in the M×M direct-write system, which is capable of meeting the resolution requirements of all future ITRS nodes and has a significant cost of ownership advantage over masked technologies.
Abstract: Electron beam direct-write lithography systems are capable of meeting the resolution requirements of all future ITRS nodes and have a significant cost of ownership advantage over masked technologies, but these systems typically have very poor throughput due to space charge limitations. Ion Diagnostics has developed a multicolumn, multibeam (M×M™) direct-write system that circumvents the space charge limitations by spreading the electron current over the wafer. The resulting lithography system can achieve critical dimensions of less than 100 nm with production throughputs greater than 60 wafers per hour, independent of wafer size. In this article we describe the electron optical column used in this system. We have developed a novel, microfabricated electron gun that produces 32 parallel electron beams that are individually controlled and blanked and contain deflectors that allow the gun optics to act as a perfect lens. Each column is 2 cm×2 cm and can align and scan the 32 beams in parallel on the wafer. The wafer voltage is typically held at 50–100 kV, and backscattered electrons are collected for imaging and alignment information. Theoretical results and some performance results for a prototype column are presented.
TL;DR: In this paper, the potential of local carbon oxidation is exploited to give a parallel lithography approach which uses prepatterned stamps for electron-induced parallel structuring of the carbon film.
Abstract: Nanometer-scale lithography in amorphous carbon layers was carried out by locally oxidizing the carbon under the tip of a scanning probe microscope. Although this patterning technique is able to yield very small structures, its speed is severely limited due to the serial character of the writing process. We exploit the potential of local carbon oxidation to give a parallel lithography approach which uses prepatterned stamps for electron-induced parallel structuring of the carbon film. This technique allows the transfer of complex, three-dimensional patterns into a carbon resist layer within a single process step.
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17 Aug 2000TL;DR: In this paper, a maskless plasma-formed ion beam lithography tool for patterning of sub-50 nm features on large area flat or curved substrate surfaces is presented, which does not require an accelerator column and electrostatic beam scanning components.
Abstract: A maskless plasma-formed ion beam lithography tool provides for patterning of sub-50 nm features on large area flat or curved substrate surfaces. The system is very compact and does not require an accelerator column and electrostatic beam scanning components. The patterns are formed by switching beamlets on or off from a two electrode blanking system with the substrate being scanned mechanically in one dimension. This arrangement can provide a maskless nano-beam lithography tool for economic and high throughput processing.
TL;DR: In this article, a variety of fabrication techniques for single-wall nanotube (SWNT) circuits have been developed, ranging from variants of electron beam lithography to AFM nanomanipulations.
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03 Oct 2000TL;DR: In this article, a method and apparatus for controlling beam emittance by placing a quadrupole lens array in a drift space of an illumination system component was proposed, which can permit independent control of beam current and beam emission, which is beneficial in a Scalpel illumination system.
Abstract: A method and apparatus for controlling beam emittance by placing a quadrupole lens array in a drift space of an illumination system component. The illumination system component may be an electron gun or a liner tube or drift tube, attachable to an electron gun. The quadrupole lens array may be three or more mesh grids or a combination of grids and continuous foils. The quadrupole lens array forms a multitude of microlenses resembling an optical “fly's eye” lens. The quadrupole lens array splits an incoming solid electron beam into a multitude of subbeams, such that the outgoing beam emittance is different from the incoming beam emittance, while beam total current remains unchanged. The method and apparatus permit independent control of beam current and beam emittance, which is beneficial in a SCALPEL illumination system.
21 Jul 2000
TL;DR: In this article, the pattern on a stamp is transferred into a polymer layer on the substrate by repeating a step-and-stamp cycle, and the resist layer is used as etching mask or for fabrication of interdigitated aluminum fingers by lift-off.
Abstract: In this work we describe a new method suitable for large area nanoimprint lithography. In step&stamp process the pattern on a stamp is transferred into a polymer layer on the substrate by repeating a step&stamp cycle. The method is demonstrated by imprinting matrices of test structures on polymer-coated 100 mm silicon wafers. A new polymer, PPM, is used as resist in the experiments. The polymer has been developed to fulfill the demands of imprint lithography. Patterns with sizes down to 400 nm were imprinted into either 100 nm or 340 nm thick PPM resist. After thinning in oxygen plasma, the resist layer is used as etching mask or for fabrication of interdigitated aluminum fingers by lift-off.
TL;DR: In this paper, the authors investigated charge induced pattern distortions in low voltage electron beam lithography in the energy range of 1 to 5 kV and found that significant pattern placement errors and pattern distortions were observed in the case of electrically insulating substrates caused by charge trapping and deflection.
Abstract: Charge induced pattern distortions in low voltage electron beam lithography in the energy range of 1 to 5 kV were investigated. Pattern distortion on conducting substrates such as silicon was found to be small, while significant pattern placement errors and pattern distortions were observed in the case of electrically insulating substrates caused by charge trapping and deflection of the incident electron beam. The nature and magnitude of pattern distortions were found to be influenced by the incident electron energy, pattern size, electrical conductivity, and secondary electron emission coefficient of the substrate. Theoretical modeling predicts the electron beam deflection to be directly proportional to the trapped surface charge density and inversely proportional to the accelerating voltage.
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24 Jul 2000TL;DR: In this paper, an electron beam lithography system consisting of an electron gun, an illumination optical system, and a projection optical system was used to produce an image of a desired character of the CP aperture.
Abstract: An electron beam lithography system 10 comprises an electron gun including a rectangular cathode 1 having an emission surface having an aspect ratio of other than 1, an illumination optical system 3 of an asymmetric lens system including multipole lenses Qa 1 and Qa 2 , a CP aperture 5 , and a projection optical system 8 of a symmetric lens system including multipole lenses Qb 1 through Qb 4 . This electron beam lithography system 10 is used for emitting an electron beam at a low acceleration of 5 kV or less from the rectangular cathode 1 , for controlling the illumination optical system so as to form an image of a desired character of the CP aperture 5 on an isotropic plane of incidence at different demagnifications in minor-axis and major-axis directions in accordance with the aspect ratio of the rectangular cathode 1 , and for controlling the projection optical system 8 so that the electron beam leaving the CP aperture 5 as an aperture image is incident on a substrate 21 at the same demagnification in the minor-axis and major-axis directions and at different incident angles in the minor-axis and major-axis directions while passing through the trajectory without establishing any crossovers.