Showing papers on "Electron-beam lithography published in 2002"

Two-dimensional optics with surface plasmon polaritons

Abstract: We report the experimental realization of highly efficient optical elements built up from metal nanostructures to manipulate surface plasmon polaritons propagating along a silver/polymer interface. Mirrors, beamsplitters, and interferometers produced by electron-beam lithography are investigated. The plasmon fields are imaged by detecting the fluorescence of molecules dispersed in the polymer.

Angle-Resolved Nanosphere Lithography: Manipulation of Nanoparticle Size, Shape, and Interparticle Spacing

Abstract: This work presents a novel approach to fine-tuning the size, shape, and interparticle spacing of nanoparticles fabricated by nanosphere lithography (NSL). This approach, termed angle-resolved nanosphere lithography (AR NSL), is a variant of NSL that yields vastly different, and increasingly flexible, nanostructures. This is accomplished by controlling the angle, θ, between the surface normal of the sample assembly and the propagation vector of the material deposition beam. Comparison of experimental results to simulated nanoparticle array geometries generated using an analytical model show excellent qualitative agreement. Using AR NSL, we have demonstrated that it is possible to reduce in-plane nanoparticle dimensions by a factor of 4. This important result shows that it will be possible to achieve fabrication of nanoparticles with precision control of their dimensions in a size regime comparable with the industry standard electron beam lithography. AR NSL provides a massively parallel, rather than serial...

Size effect in mesoscopic epitaxial ferroelectric structures: Increase of piezoelectric response with decreasing feature size

Abstract: An epitaxial 200 nm thick film of Pb(Zr0.40Ti0.60)O3 (PZT) has been deposited by reactive rf magnetron sputtering on conductive Nb-doped SrTiO3 (100) (STO). The patterning process involved electron-beam lithography of polymethylmethacrylate, fabrication of a 75 nm thick Cr hard mask layer by means of a lift-off process, and dry etching of PZT. The smallest PZT features obtained were 100 nm in lateral dimensions. Piezoelectric sensitive scanning force microscopy in the contact mode revealed a strong increase of the piezoelectric response for feature sizes with lateral dimensions below 300 nm. It is proposed that this behavior is mainly due to vanishing a domains.

Simple fabrication scheme for sub-10 nm electrode gaps using electron-beam lithography

Abstract: An innovative and simple method, based on electron-beam (e-beam) overlapping and overexposure techniques, is developed to fabricate sub-10 nm electrode gaps with very good electrical properties. Gaps with 4 to 10 nm spacing can be fabricated using a proper e-beam dose and pattern-developing time. The fabrication yield is nearly 100% for 8–9 nm gaps, but significantly smaller for 3–4 nm gaps. The gap leakage resistance is around 1012–1013 Ω, implying very good isolation. As an example, we present a transport study on a single 8 nm Co particle junction using a 10 nm gap.

Photoluminescence spectroscopy of single silicon quantum dots

Abstract: Photoluminescence (PL) from single silicon quantum dots have been recorded and spectrally resolved at room temperature. The Si nanocrystals (NCs) were fabricated using electron-beam lithography and ...

Directed placement of suspended carbon nanotubes for nanometer-scale assembly

Abstract: Single-wall carbon nanotubes (SWNTs) suspended in an aqueous solution have been placed selectively between two metal electrodes separated by a few tens of nanometers. After the initial patterning of the metal electrodes by electron beam lithography, no further fine-line lithography steps are necessary to achieve directed placement of SWNTs at these dimensions. An ac bias is applied between the two electrodes and the “nanoscale wiring” is completed within seconds. An additional advantage of using ac bias is the enhancement for selectively placing SWNTs between the electrode gap over competing contaminant species in the solution.

Process for forming resist pattern and process for fabricating semiconductor device

Abstract: PROBLEM TO BE SOLVED: To provide a process for forming a resist pattern having a trimming step of novel arrangement. SOLUTION: A resist film 16 is deposited on an underlying film 14 deposited on a wafer 12. A resist material exhibiting such properties as the line width of a resist pattern shrinks through irradiation with an electron beam is used. The resist film is subjected to exposure processing according to a conventional method and then developed to form a resist pattern 18 of a specified line width. Subsequently, the resist pattern 18 is irradiated with an electron beam at an irradiation energy of 100eV-500keV to shrink the line width of the resist pattern 18 thus forming a resist pattern 20 having a shrunk line width. Relation between the level and exposure time of irradiation energy and the shrinkage of line width is established previously, and the level and exposure time of irradiation energy are determined depending on a desired shrinkage width. Finally, the underlying film 14 is etched using the resist pattern 20 having a shrunk line width as a mask thus forming an underlying film pattern 22. COPYRIGHT: (C)2004,JPO

Making electrical contacts to nanowires with a thick oxide coating

Abstract: Techniques are presented for making ohmic contacts to nanowires with a thick oxide coating. Although experiments were carried out on Bi nanowires, the techniques described in this paper are generally applicable to other nanowire systems. Metal electrodes are patterned to individual Bi nanowires using, electron beam lithography. Imaging the chemical reaction on the atomic scale with in situ high-resolution transmission electron microscopy shows that annealing in H-2 or NH3 can reduce the nanowires' oxide coating completely. The high temperatures required for this annealing, however, are not compatible with the lithographic techniques. Low-resistance ohmic contacts to individual bismuth nanowires are achieved using a focused ion beam (FIB) to first sputter away the oxide layer and then deposit Pt contacts. By combining electron beam lithography and FIB techniques, ohmic contacts stable from 2 to 400 K are successfully made to the nanowires. A method for preventing the burnout of nanowires from electrostatic discharge is also developed.

Ethylene Hydrogenation over Platinum Nanoparticle Array Model Catalysts Fabricated by Electron Beam Lithography: Determination of Active Metal Surface Area

Abstract: Pt nanoparticle array model catalysts with 28 ± 2 nm diameters and 100 ± 2 nm interparticle spacing have been fabricated with electron beam lithography on alumina supports. A novel method for cleaning the Pt nanoparticle arrays, involving low dosages of NO2 and CO and mild temperature flashing, was established. This cleaning procedure was crucial for measuring reaction rates over the nanoparticle arrays. The reactivity of the Pt/Al2O3 arrays was compared to a Pt(111) single crystal for the ethylene hydrogenation reaction. The activation energy and the pressure dependence of the H2 and C2H4 on the nanoparticle array were in excellent agreement with the kinetic data on the Pt(111) single-crystal model catalyst. Because the ethylene hydrogenation reaction is structure insensitive, the rate equation for Pt(111) can be applied to the Pt nanoparticle arrays. The calculated turnover frequency led to a calculated active metal surface area that compared very well with an active metal surface area on the basis of g...

Electron optics for multi-beam electron beam lithography tool

Abstract: A charge particle optical column capable of being used in a high throughput, mutli-column, multi-beam electron beam lithography system is disclosed herein. The column has the following properties: purely electrostatic components; small column footprint (20 mm square); multiple, individually focused charge particle beams; telecentric scanning of all beams simultaneously on a wafer for increased depth of field; and conjugate blanking of the charged particle beams for reduced beam blur. An electron gun is disclosed that uses microfabricated field emission sources and a microfabricated aperture-deflector assembly. The aperture-deflector assembly acts as a perfect lens in focusing, steering and blanking a multipicity of electron beams through the back focal plane of an immersion lens located at the bottom of the column. Beam blanking can be performed using a gating signal to decrease beam blur during writing on the wafer.

Nanometer Scale Patterning of Langmuir−Blodgett Films of Gold Nanoparticles by Electron Beam Lithography

Abstract: Electron beam lithography on Langmuir−Blodgett films of alkanethiol-capped gold nanoparticles is shown to be a viable strategy to define nanometer scale structures of such particles Sub-50 nm wide “nanowires”, the thickness of which is controlled at the single particle level, are created with e-beam doses in the mC/cm2 range It is shown that the patterns are formed by radiation-induced cross-linking of the alkyl chains and that they can be contacted and studied electrically

Fabrication and characterization of different types of two-dimensional AlGaAs photonic crystal slabs

Abstract: Photonic crystals having two-dimensional periodicity on a length scale of 320–450 nm are fabricated by electron beam lithography in combination with high-aspect-ratio dry etching. To achieve three-dimensional control of the optical properties, three kinds of dielectric waveguide structures based on AlGaAs heterostructures, that is, semiconductor-clad, air-bridge, and oxide-clad structures, are investigated. The ability to guide light through such photonic crystal devices is demonstrated by optical transmission measurements. Clear photonic band gap effects resulting in 30 dB attenuation of the transmitted light can be observed in the stop-band regions. The measured results are in good agreement with theoretical band-structure calculations and with numerically computed transmission spectra obtained by the finite-difference time-domain method.

Nanometer-spaced electrodes with calibrated separation

Abstract: We have fabricated pairs of platinum electrodes with separation between 20 and 3.5 nm. Our technique combines electron beam lithography and chemical electrodeposition. We show that the measurement of the conductance between the two electrodes through the electrolyte provides an accurate and reproducible way to control their separation. We have tested the robustness of the electrodes by applying large voltages across them and by using them to measure the transport properties of Au nanoclusters. Our results show that the technique reliably produces metallic electrodes with a separation that bridges the minimum scale accessible by electron beam lithography with the atomic scale.

Semiconductor device and a manufacturing method of the same

Abstract: There is disclosed a method for forming micro patterns in a semiconductor integrated circuit device with high productivity and high accuracy. A photolithography having high throughput and electron beam lithography using a reticle and having relatively high throughput and high resolution are selectively used so as to obtain highest throughput while satisfying accuracy and resolution required for each product/layer. In the case of using the electron beam lithography, a non-complementary reticle and a complementary reticle are selectively used so as to obtain highest throughput while satisfying required accuracy and resolution. Thus, productivity and integration can be improved for the semiconductor integrated circuit device.

Optical waveguides with apodized sidewall gratings via spatial-phase-locked electron-beam lithography

Abstract: We describe a technique to fabricate Bragg gratings in the sides of optical waveguides using a single lithographic step. This technique is particularly suited to the apodized gratings required for add/drop filters in dense-wavelength-division multiplexing. Apodization minimizes cross talk between channels and improves the filter response. Silicon-on-insulator rib waveguides with both uniform and apodized gratings were fabricated using direct-write spatial-phase-locked electron-beam lithography (SPLEBL). This approach combines SPLEBL’s pattern-placement accuracy with the flexibility of direct-write device prototyping. The resulting grating-based devices exhibited substantially reduced side-lobe levels.

High efficient light-emitting diodes with antireflection subwavelength gratings

Abstract: A two-dimensional subwavelength grating (SWG) has been fabricated on a GaAlAs light-emitting diode (LED). The SWG is patterned by electron beam lithography and etched by fast atom beam with Cl/sub 2/ and SF/sub 6/ gases. The fabricated grating has 200 nm period and the tapered grating shape with aspect ratio of 1.38 to prevent reflection in the spectral region including 850 nm light emission. The emission is increased by 21.6% at the normal emission angle. The total emittance is increased by 60% with the SWG in comparison with that of the flat surface.

Diamond nanoimprint lithography

Abstract: Electron beam (EB) lithography using polymethylmethacrylate (PMMA) and oxygen gas reactive ion etching (RIE) were used to fabricate fine patterns in a diamond mould. To prevent charge-up during EB lithography, thin conductive polymer was spin-coated over the PMMA resist, yielding dented line patterns 2 μ m wide and 270 nm deep. The diamond mould was pressed into PMMA on a silicon substrate heated to 130, 150 and 170oC at 43.6, 65.4 and 87.2 MPa. All transferred PMMA convex line patterns were 2 μ m wide. Imprinted pattern depth increased with rising temperature and pressure. PMMA patterns on diamond were transferred by the diamond mould at 150oC and 65.4 MPa, yielding convex line patterns 2 μ m wide and 200 nm high. Direct aluminium and copper patterns were obtained using the diamond mould at room temperature and 130.8 MPa. The diamond mould is thus useful for replicating patterns on PMMA and metals.

Low stress development of poly(methylmethacrylate) for high aspect ratio structures

Abstract: Magnetic head fabrication for >100 Gbit/in.2 areal density requires minimum lithographic feature size <0.15 μm, with aspect ratios of 8:1–10:1. Electron-beam lithography can provide adequate resolution for research and development of magnetic heads, and at 100 kV can provide greater than 10:1 aspect ratios in 1–3 μm thick single-layer resist poly(methylmethacrylate). Poly (methylmethacrylate) (PMMA) is well known for withstanding the rigors of plating baths, but at these thicknesses requires a nonswelling, low-stress developer such as the LIGA mixture (also known as “GG Developer (U.S. Patent No. 4,393,129)”). In this work we present the results of isopropyl alcohol:water development for thick PMMA, and describe the dependence of resist contrast on the temperature of the developer. We also demonstrate the advantage of ultrasonic agitation during development. These development techniques have brought resist profiles in PMMA to the theoretical limit predicted by Monte Carlo simulations.

Hydrogen silsesquioxane for direct electron-beam patterning of step and flash imprint lithography templates

Abstract: The feasibility of using hydrogen silsesquioxane (HSQ) to directly pattern the relief layer of step and flash imprint lithography (SFIL) templates has been successfully demonstrated. HSQ is a spin-coatable oxide, which is capable of high resolution electron-beam lithography. Negative acting and nonchemically amplified, HSQ has moderate electron-beam sensitivity and excellent processing latitude. In this novel approach, 6 ×6 × 0.25 in.3 quartz photomask substrates are coated with a 60 nm indium tin oxide (ITO) charge dissipation layer and directly electron-beam written using a 100 nm film of HSQ. Direct patterning of an oxide relief layer eliminates the problems of critical dimension control associated with both chromium and oxide etches, both required processes of previous template fabrication schemes. Resolution of isolated and semidense lines of 30 nm has been demonstrated on imprinted wafers using this type of template. During this evaluation, a failure of the release layer to provide a durable nonstic...

Digital electrostatic electron-beam array lithography

Abstract: A concept for maskless digital electrostatically focused e-beam array direct-write lithography (DEAL) has been developed at Oak Ridge National Laboratory. This concept incorporates a digitally addressable field-emission array (DAFEA) integrated into a logic and control circuit implemented as an integrated circuit. The design goal is for 3 000 000 individually addressable field-emission cathodes with a 4 μm by 8 μm pitch on a single ∼1 cm2 integrated circuit. The DAFEA design includes built-in electrostatic focusing for each emitter with feedback dose-control circuits to drive each emitter for tightly controlled electron delivery. With the electrostatic focusing, an array of ∼460 of these integrated circuits (up to 30 across by ∼23 rows deep) are suspended on a back plane ∼100 μm above a 300 mm semiconductor wafer. This arrangement could lithographically expose an entire 300 mm wafer, with 30 nm pixels, in less than 45 s, with every wafer pixel redundantly illuminated eight times allowing gray-scale edge p...

A reliable scheme for fabricating sub-5 nm co-planar junctions for single-molecule electronics

Abstract: We demonstrate a high yield production scheme to fabricate sub-5 nm co-planar metal–insulator–metal junctions. This involves determining the relationship between the actual gap between the metallic junctions for a given designed gap, and the use of weak developers with ultrasonic agitation to process the exposed resist. This results in an improved process to achieve narrow inter-electrode gaps. The gaps were imaged using an AFM equipped with a carbon nanotube tip to achieve a high degree of accuracy in measurement. The smallest gap unambiguously measured was ~ 2 nm. Gaps with ≤ 5 nm spacing were produced with a very high yield of about 75% for a designed inter-electrode distance of 0 nm. The leakage resistance of the gaps was found to be of the order of 1012 Ω. The entire junction structure was designed to be co-planar to better than 1 nm over 1 μ m2.

Real-time prediction of and correction of proximity resist heating in raster scan particle beam lithography

Abstract: The present invention relates to methods of predicting proximity heating of resists in electron beam lithography in real-time as the writing proceeds enabling beam compensation in current and/or dwell time to be performed during writing. A method of using a precomputed kernel capable of proximity resist temperature evaluation in real-time as beam writing proceeds by scalar product of the kernel with a graded cell size coverage map. A shifted impulse response function is shown to give the kernel values accurate to within a few percent.

Multiple-beam interference lithography with electron beam written gratings

Abstract: Interference lithography with multiple beams provides two-dimensional periodic patterns in a single exposure step. It is possible to obtain various symmetries and shapes such as sparse hole arrays or dots on a hexagonal grid. However, when the number of interfering beams exceeds three, the intensity pattern depends strongly on the relative phases of the beams. In this article we show that this problem can be overcome with a scheme where transmission diffraction gratings written on a single substrate create the interfering beams possessing the required phase relations. The relative phases of the diffracted beams are controlled by the relative positions of the gratings in the substrate plane. We used electron beam lithography with an interferometrically controlled stage to obtain the required precise placement of the gratings. This method enabled us to produce hexagonal and square arrays of holes where we used three and four beam configurations, respectively. Moreover, we created sparse hole arrays that have hexagonal and square symmetries with six and eight beam interference. The experiments were carried out in the extreme ultraviolet region with synchrotron radiation and with laser light in the visible spectrum. The technique requires spatially coherent light but it is achromatic and it is not sensitive to small errors in the alignment of the incoming beam.

Optical device and method of manufacture

Abstract: The present invention provides for a method of producing an optical device by means of electron beam lithography and including the step of varying the characteristics of the electron beam spot during formation of the device and also an apparatus for producing diffractive optical devices and/or holographic devices by means of electron beam lithography and including an electron beam lithograph, controlling and processing means, means for varying the characteristics of the electron beam spot during formation of the device, and wherein the processing means is arranged for compiling and pre-processing data and for providing optimization and allocation control and to optical devices such as those produced thereby.

Challenges in high NA, polarization, and photoresists

Abstract: Optical lithography is being pushed into a regime of extreme-numerical aperture (extreme-NA). The implications of the nonscalar effects of high-NA lithography (above 0.50) have been discussed now for many years. This paper considers the consequences of imaging at numerical apertures above 0.70 with the oblique imaging angles required for low k1 lithography. A new scaling factor, kNA, is introduced to capture the impact of low k1 imaging combined with extreme-NA optics. Extreme-imaging is defined as k1 and kNA values approach 0.25. Polarization effects combined with resist requirements for extreme-NA are addressed, especially as they relate to 157 nm lithography. As these technologies are pursued, careful consideration of optical and resist parameters is needed. Conventional targets for resist index, absorption, diffusion, and reflectivity based on normal incidence imaging may not lead to optimum performance without these considerations. Additionally, methods of local and semi-local mask polarization are discussed using concepts of wire-grid polarizer arrays. Back-side and image-side polarization OPC methods are introduced.