Showing papers on "Lithography published in 2004"

Improving resolution in photolithography with a phase-shifting mask

Abstract: The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10× tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

Low-loss SOI photonic wires and ring resonators fabricated with deep UV lithography

Abstract: We demonstrate single-mode photonic wires in silicon-on-insulator with propagation loss as low as 2.4 dB/cm, fabricated with deep ultraviolet lithography and dry etching. We have also made compact racetrack and ring resonators functioning as add-drop filters, attaining Q values larger than 3000 and low add-drop crosstalk.

Nanowire Arrays Defined by Nanoimprint Lithography

Abstract: We demonstrate the use of nanoimprint lithography to define arrays of vertical InP nanowires. Each nanowire is individually seeded from a catalyzing gold particle and then grown via vapor-liquid-solid growth in a metal-organic vapor phase epitaxy system. The diameter and position of each nanowire can be controlled to create engineered arrays, demonstrated with a hexagonal photonic crystal pattern. This combination of nanoimprint and self-assembly of nanostructures is attractive for photonics and electronics, as well as in life sciences.

Polymer Imprint Lithography with Molecular-Scale Resolution

Abstract: We show that small diameter, single-walled carbon nanotubes can serve as templates for performing polymer imprint lithography with feature sizes as small as 2 nm − comparable to the size of an individual molecule. The angstrom level uniformity in the critical dimensions of the features provided by this unusual type of template provides a unique ability to investigate systematically the resolution of imprint lithography at this molecular scale. Collective results of experiments with several polymer formulations for the molds and the molded materials suggest that the density of cross-links is an important molecular parameter that influences the ultimate resolution in this process. Optimized materials enable reliable, repetitive patterning in this single nanometer range.

High-Resolution Soft Lithography: Enabling Materials for Nanotechnologies†

Abstract: The availability of commercially viable nanofabrication processes is key to realizing the potential of nanotechnologies, especially in the fields of photonics, electronics, and proteomics. The imprint lithographic (IL) technique is a case in point, an alternative to photolithography for manufacturing integrated circuits, nanofluidic and other devices with sub100-nm features. However, it is becoming increasingly clear that new materials are needed to advance IL methods to their putative limits. We recently reported the fabrication of organic-solvent resistant, microfluidic devices with features on the order of hundreds of microns made from photocurable perfluoropolyethers (PFPEs). PFPE-based materials are liquids at room temperature and can be photochemically cross-linked to yield highly fluorinated, solvent resistant, chemically robust, durable, elastomers with a modulus of 4.0 MPa. Herein we report the successful use of PFPE-based materials in high-resolution imprint lithography. Imprint lithography can be roughly broken into two areas: 1) so-called soft lithographic techniques, such as solventassisted micro-molding (SAMIM), micro-molding in capillaries (MIMIC), and microcontact printing (MCP), and 2) rigid imprint techniques, such as nanocontact molding (NCM), “step and flash” imprint lithography (S-FIL), and nanoimprint lithography (NIL). Polydimethylsiloxane (PDMS)

Methods for fabricating isolated micro- and nano- structures using soft or imprint lithography

Abstract: The presently disclosed subject matter describes the use of fluorinated elastomer-based materials, in particular perfluoropolyether (PFPE)-based materials, in high-resolution soft or imprint lithographic applications, such as micro- and nanoscale replica molding, and the first nano-contact molding of organic materials to generate high fidelity features using an elastomeric mold. Accordingly, the presently disclosed subject matter describes a method for producing free-standing, isolated nanostructures of any shape using soft or imprint lithography techniques.

System and method for lithography simulation

Abstract: In one aspect, the present invention is directed to a technique of, and system for simulating, verifying, inspecting, characterizing, determining and/or evaluating the lithographic designs, techniques and/or systems, and/or individual functions performed thereby or components used therein. In one embodiment, the present invention is a system and method that accelerates lithography simulation, inspection, characterization and/or evaluation of the optical characteristics and/or properties, as well as the effects and/or interactions of lithographic systems and processing techniques.

Nanotransfer printing by use of noncovalent surface forces: Applications to thin-film transistors that use single-walled carbon nanotube networks and semiconducting polymers

Abstract: We report a purely additive nanotransfer printing process that uses noncovalent surface forces to guide the transfer of thin metal films from low-energy surfaces of high-resolution stamps to a variety of substrates. Structures with dimensions as small as a few hundred nanometers, with edge roughness as small as 10nm are demonstrated. Metal multilayer stacks patterned in this way have electrical resistances that are the same as those formed by evaporation and conventional lithography. Thin-film transistors that use source/drain electrodes printed directly onto thin films of the semiconducting polymer regioregular polythiophene and networks of single-walled carbon nanotubes exhibit device mobilities and on/off ratios that are comparable to or higher than those of devices fabricated using standard methods.

Optical tweezers applied to a microfluidic system

Abstract: We will demonstrate how optical tweezers can be combined with a microfluidic system to create a versatile microlaboratory. Cells are moved between reservoirs filled with different media by means of optical tweezers. We show that the cells, on a timescale of a few seconds, can be moved from one reservoir to another without the media being dragged along with them. The system is demonstrated with an experiment where we expose E. coli bacteria to different fluorescent markers. We will also discuss how the system can be used as an advanced cell sorter. It can favorably be used to sort out a small fraction of cells from a large population, in particular when advanced microscopic techniques are required to distinguish various cells. Patterns of channels and reservoirs were generated in a computer and transferred to a mask using either a sophisticated electron beam technique or a standard laser printer. Lithographic methods were applied to create microchannels in rubber silicon (PDMS). Media were transported in the channels using electroosmotic flow. The optical system consisted of a combined confocal and epi-fluorescence microscope, dual optical tweezers and a laser scalpel.

Gold Nanoparticle Patterning of Silicon Wafers Using Chemical e-Beam Lithography

Abstract: This paper demonstrates a novel facile method for fabrication of patterned arrays of gold nanoparticles on Si/SiO2 by combining electron beam lithography and self-assembly techniques. Our strategy is to use direct-write electron beam patterning to convert nitro functionality in self-assembled monolayers of 3-(4-nitrophenoxy)-propyltrimethoxysilane to amino functionality, forming chemically well-defined surface architectures on the 100 nm scale. These nanopatterns are employed to guide the assembly of citrate-passivated gold nanoparticles according to their different affinities for amino and nitro groups. This kind of nanoparticle assembly offers an attractive new option for nanoparticle patterning a silicon surface, as relevant, for example, to biosensors, electronics, and optical devices.

Edge spreading lithography and its application to the fabrication of mesoscopic gold and silver rings.

Abstract: A new form of edge lithography, edge spreading lithography (ESL), has been demonstrated and applied to the formation of coinage metal rings. In this process, alkanethiols are delivered from a flat PDMS stamp to the surface of a metal film through a two-dimensional array of spherical silica colloids. The thiols further spread on the metal surface, forming highly ordered SAMs in the form of a ring pattern. Following lift-off of beads, the pattern in the SAMs can be transferred into the metal film through wet chemical etching, with SAMs serving as the resist. The dimensions of the rings can be readily controlled by several parameters such as the beads diameter, the concentration of the thiol solution, and the contact time between the stamp and the silica beads.

Lithographic printing plate precursor and lithographic printing method

Abstract: A lithographic printing plate precursor includes an image-recording layer and a protective layer containing a stratiform compound, wherein at least one of the image-recording layer and the protective layer contains a polymer containing as a repeating unit, a structural unit having an ammonium structure.

Nanometer-scale pattern registration and alignment by directed diblock copolymer self-assembly

Abstract: We describe a fabrication method that combines the alignment capabilities of optical lithography with the sub-lithographic dimensions achievable using self-assembled diblock copolymer films. We use surface topography to direct the assembly of in-plane cylindrical copolymer domains so as to subdivide larger patterns defined using optical lithography, in the process registering the location of each 20-nm polymer domain to the lithographic pattern. Our approach provides an application for self-assembly in the fabrication of complex microelectronic circuits entailing alignment of multiple patterned layers. We detail the influence of such process parameters as lithographic pattern dimensions and density, copolymer film thickness, and anneal time on the quality of the resulting nanometer-scale-domain registration.

Photonic crystals through holographic lithography: Simple cubic, diamond-like, and gyroid-like structures

Abstract: We show how to fabricate three basic photonic crystal structures with simple cubic, fcc, and bcc translational symmetry by interference lithography. The structures are fabricable by the interference of beams launched from the same half space. The simple cubic structure is size scalable while the structure with fcc translational symmetry possesses two band gaps. Both these structures are experimentally realized.

Fabrication of Stimulus-Responsive Nanopatterned Polymer Brushes by Scanning-Probe Lithography

Abstract: Stimulus-responsive, surface confined poly(N-isopropylacrylamide) (pNIPAAM) brush nanopatterns were prepared on gold-coated silicon substrates in a “grafting-from” approach that combines “nanoshaving”, a scanning probe lithography method, with surface-initiated polymerization using atom transfer radical polymerization (ATRP). The reversible, stimulus-responsive conformational height change of these nanopatterned polymer brushes was demonstrated by inverse transition cycling in water, and water−methanol mixtures (1:1, v:v). Our findings are consistent with the behavior of laterally confined and covalently attached polymer chains, where chain mobility is restricted largely to the out-of-plane direction. Our nanofabrication approach is generic and can likely be extended to a wide range of vinyl monomers.

Toward Atomic-Scale Device Fabrication in Silicon Using Scanning Probe Microscopy

Abstract: We present a complete fabrication process for the creation of robust nano-and atomic-scale devices in silicon using a scanning tunneling microscope (STM). In particular we develop registration markers which, in combination with a custom-designed STM-scanning electron microscope (SEM) system, solve one of the key fabrication problems - connecting the STM-patterned buried phosphorus-doped devices, fabricated in the ultrahigh vacuum environment, to the outside world. The first devices demonstrate the feasibility of this technology and confirm the presence of quantum confinement in devices as electron propagation is laterally constricted by STM patterning.

Ten- to 50-nm-long quasi-ballistic carbon nanotube devices obtained without complex lithography

Abstract: A simple method combining photolithography and shadow (or angle) evaporation is developed to fabricate single-walled carbon nanotube (SWCNT) devices with tube lengths of ≈10–50 nm between metal contacts. Large numbers of such short devices are obtained without the need of complex tools such as electron beam lithography. Metallic SWCNTs with lengths of ≈10 nm, near the mean free path of lop ≈ 15 nm for optical phonon scattering, exhibit nearly ballistic transport at high biases and can carry unprecedented 100-μA currents per tube. Semiconducting SWCNT fieldeffect transistors with ≈50-nm channel lengths are routinely produced to achieve quasi-ballistic operations for molecular transistors. The results demonstrate highly length-scaled and high-performance interconnects and transistors realized with SWCNTs.

Ordered block-copolymer assembly using nanoimprint lithography

Abstract: Nanoimprint lithography and self-assembly of poly(styrene)-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer are combined to induce order in the phase-separated domains Tailored periodic arrays of poly(methyl methacrylate) (PMMA) cylinders normal or parallel to neutralized silicon surfaces can be formed inside the gap of imprint molds This method opens up a new route to the controlled phase separation of block copolymers with precise placement of the phase-separated domains

A method of forming stepped structures employing imprint lithography

Abstract: The present invention provides a method for forming a stepped structure on a substrate that features transferring, into the substrate, an inverse shape of the stepped structure disposed on the substrate.

Organic light-emitting diodes formed by soft contact lamination.

Abstract: Although tremendous progress has been made in organic light-emitting diodes (OLEDs), with few exceptions they are fabricated in the standard way by sequentially depositing active layers and electrodes onto a substrate. Here we describe a different approach for building OLEDs, which is based on physical lamination of thin metal electrodes supported by an elastomeric layer against an electroluminescent organic. This method relies only on van der Waals interactions to establish spatially homogeneous, intimate contacts between the electrodes and the organic. We find that devices fabricated in this manner have better performance than those constructed with standard processing techniques. The lamination approach avoids forms of disruption that can be introduced at the electrode/organic interface by metal evaporation and has a reduced sensitivity to pinhole or partial pinhole defects. In addition, because this form of “soft” contact lamination is intrinsically compatible with the techniques of soft lithography, it is easy to build patterned OLEDs with feature sizes into the nanometer regime. This method provides a new route to OLEDs for applications ranging from high performance displays to storage and lithography systems that rely on subwavelength light sources.

Lithographic printing with polarized light

Abstract: The present invention provides systems and methods for improved lithographic printing with polarized light. In embodiments of the present invention, polarized light (radially or tangentially polarized) is used to illuminate a phase-shift mask (PSM) and produce an exposure beam. A negative photoresist layer is then exposed by light in the exposure beam. A chromeless PSM can be used. In further embodiments of the present invention, radially polarized light is used to illuminate a mask and produce an exposure beam. A positive photoresist layer is then exposed by light in the exposure beam. The mask can be an attenuating PSM or binary mask. A very high image quality is obtained even when printing contact holes at various pitches in low k applications.

Refractive index system monitor and control for immersion lithography

Abstract: A system and/or method are disclosed for measuring and/or controlling refractive index (n) and/or lithographic constant (k) of an immersion medium utilized in connection with immersion lithography. A known grating structure is built upon a substrate. A refractive index monitoring component facilitates measuring and/or controlling the immersion medium by utilizing detected light scattered from the known grating structure.

Development of a deep silicon phase Fresnel lens using Gray-scale lithography and deep reactive ion etching

Abstract: We report the first fabrication and development of a deep phase Fresnel lens (PFL) in silicon through the use of gray-scale lithography and deep-reactive ion etching (DRIE). A Gaussian tail approximation is introduced as a method of predicting the height of photoresist gray levels given the relative amount of transmitted light through a gray-scale optical mask. Device mask design is accomplished through command-line scripting in a CAD tool to precisely define the millions of pixels required to generate the appropriate profile in photoresist. Etch selectivity during DRIE pattern transfer is accurately controlled to produce the desired scaling factor between the photoresist and silicon profiles. As a demonstration of this technology, a 1.6-mm diameter PFL is etched 43 /spl mu/m into silicon with each grating profile designed to focus 8.4 keV photons a distance of 118 m.

Matching the Resolution of Electron Beam Lithography by Scanning Near-Field Photolithography

Abstract: Molecular features with widths of only 20 nm have been fabricated in self-assembled monolayers of alkanethiols on gold using a new lithographic tool, scanning near-field photolithography, based upon the use of a near-field scanning optical microscope (NSOM) coupled to a UV laser. Quite unexpectedly it has proved possible to routinely fabricate structures significantly smaller than the aperture in the NSOM probe. This exceptional performance is strongly correlated with the morphology of the gold film. In particular, the best results are achieved on films with comparatively small grain sizes. In contrast, the use of atomically flat, epitaxially deposited gold films leads to a minimum feature size comparable to the aperture diameter (ca 50 nm). It is concluded that nonradiative interactions (possibly the excitation of surface plasmons) between the gold substrate and the fiber lead to a pronounced focusing of the electric field beneath the aperture.

A rapid prototyping technique for the fabrication of solvent-resistant structures

Abstract: We demonstrate a rapid prototyping technique for the fabrication of solvent-resistant channels up to and exceeding one millimeter in height. The fabrication of channels with such dimensions by conventional lithography would be both challenging and time consuming. Furthermore, we show that this technology can be used to fabricate channels with a depth that varies linearly with distance. This technique requires only a long-wavelength ultraviolet source, a mask made by a desktop printer and a commercially available optical adhesive. We demonstrate two lithographic methods: one that fabricates channels sealed between glass plates (close-faced) and one that fabricates structures on a single plate (open-faced). The latter is fully compatible with silicon replication techniques to make fluid handling devices.

Immersion lithography and its impact on semiconductor manufacturing

Abstract: ArF lithography is approaching its limit past the 90-nm node. F2 lithography using 157-nm light seems to be a natural extension to the next node. However, several key problems in F2 lithography are still insurmountable. Thin-film pellicle material cannot withstand more than 10 exposures. Hard pellicle technology is far from being manufacture worthy. Ditto for the F2 resist systems. Despite great progresses made, the CaF2 material still suffers from quality and quantity problems. On the other hand, ArF lithography using water immersion between the front lens element and the photoresist effectively reduces the 193-nm wavelength to 135 nm and opens up room for improvement in resolution and depth of focus (DOF). We give a systematic examination of immersion lithography, analyze and evaluate the diffraction, required, and available DOFs in a dry and an immersion system. We also analyze the effects of polarization to dry and immersion imaging. These phenomena are included in simulations to study the imaging of critical layers such as poly, contact, and metal layers for the 65-, 45-, and 32-nm nodes using 193- and 157-nm, dry and immersion systems. The imaging feasibility of 157-nm immersion to the 22-nm node is briefly studied. In addition to the imaging comparison, the impacts and challenges to employ these lithography systems are also covered.

Liquid-filled balloons for immersion lithography

Abstract: A liquid-filled balloon may be positioned between a workpiece, such as a semiconductor structure covered with a photoresist, and a lithography light source. The balloon includes a thin membrane that exhibits good optical and physical properties. Liquid contained in the balloon also exhibits good optical properties, including a refractive index higher than that of air. Light from the lithography light source passes through a mask, through a top layer of the balloon membrane, through the contained liquid, through a bottom layer of the balloon membrane, and onto the workpiece where it alters portions of the photoresist. As the liquid has a low absorption and a higher refractive index than air, the liquid-filled balloon system enhances resolution. Thus, the balloon provides optical benefits of liquid immersion without the complications of maintaining a liquid between (and in contact with) a lithographic light source mechanism and workpiece.