Showing papers on "Lithography published in 2002"

Protein Nanoarrays Generated By Dip-Pen Nanolithography

Abstract: Dip-pen nanolithography was used to construct arrays of proteins with 100- to 350-nanometer features. These nanoarrays exhibit almost no detectable nonspecific binding of proteins to their passivated portions even in complex mixtures of proteins, and therefore provide the opportunity to study a variety of surface-mediated biological recognition processes. For example, reactions involving the protein features and antigens in complex solutions can be screened easily by atomic force microscopy. As further proof-of-concept, these arrays were used to study cellular adhesion at the submicrometer scale.

Improved pattern transfer in soft lithography using composite stamps

Abstract: Composite stamps composed of two layersa stiff layer supported by a flexible layerextend the capabilities of soft lithography to the generation of 50−100-nm features. The preparation of these stamps was adapted from a procedure originally developed by Schmid et al. (Macromolecules 2000, 33, 3042) for microcontact printing. This paper demonstrates how pattern transfer using other soft lithographic techniquesmicromolding in capillaries, microtransfer molding, and phase-shifting lithographycan be improved using two-layer stamps relative to stamps made of Sylgard 184 poly(dimethylsiloxane).

Ink-jet printed nanoparticle microelectromechanical systems

Abstract: Reports a method to additively build three-dimensional (3-D) microelectromechanical systems (MEMS) and electrical circuitry by ink-jet printing nanoparticle metal colloids. Fabricating metallic structures from nanoparticles avoids the extreme processing conditions required for standard lithographic fabrication and molten-metal-droplet deposition. Nanoparticles typically measure 1 to 100 nm in diameter and can be sintered at plastic-compatible temperatures as low as 300/spl deg/C to form material nearly indistinguishable from the bulk material. Multiple ink-jet print heads mounted to a computer-controlled 3-axis gantry deposit the 10% by weight metal colloid ink layer-by-layer onto a heated substrate to make two-dimensional (2-D) and 3-D structures. We report a high-Q resonant inductive coil, linear and rotary electrostatic-drive motors, and in-plane and vertical electrothermal actuators. The devices, printed in minutes with a 100 /spl mu/m feature size, were made out of silver and gold material with high conductivity,and feature as many as 400 layers, insulators, 10:1 vertical aspect ratios, and etch-released mechanical structure. These results suggest a route to a desktop or large-area MEMS fabrication system characterized by many layers, low cost, and data-driven fabrication for rapid turn-around time, and represent the first use of ink-jet printing to build active MEMS.

Sequence-specific molecular lithography on single DNA molecules.

Abstract: Recent advances in the realization of individual molecular-scale electronic devices emphasize the need for novel tools and concepts capable of assembling such devices into large-scale functional circuits. We demonstrated sequence-specific molecular lithography on substrate DNA molecules by harnessing homologous recombination by RecA protein. In a sequence-specific manner, we patterned the coating of DNA with metal, localized labeled molecular objects and grew metal islands on specific sites along the DNA substrate, and generated molecularly accurate stable DNA junctions for patterning the DNA substrate connectivity. In our molecular lithography, the information encoded in the DNA molecules replaces the masks used in conventional microelectronics, and the RecA protein serves as the resist. The molecular lithography works with high resolution over a broad range of length scales from nanometers to many micrometers.

Ultrafast and direct imprint of nanostructures in silicon

Abstract: The fabrication of micrometre- and nanometre-scale devices in silicon typically involves lithography and etching. These processes are costly and tend to be either limited in their resolution or slow in their throughput1. Recent work has demonstrated the possibility of patterning substrates on the nanometre scale by ‘imprinting’2,3 or directed self-assembly4, although an etching step is still required to generate the final structures. We have devised and here demonstrate a rapid technique for patterning nanostructures in silicon that does not require etching. In our technique—which we call ‘laser-assisted direct imprint’ (LADI)—a single excimer laser pulse melts a thin surface layer of silicon, and a mould is embossed into the resulting liquid layer. A variety of structures with resolution better than 10 nm have been imprinted into silicon using LADI, and the embossing time is less than 250 ns. The high resolution and speed of LADI, which we attribute to molten silicon's low viscosity (one-third that of water), could open up a variety of applications and be extended to other materials and processing techniques.

Fabrication of nanostructures with long-range order using block copolymer lithography

Abstract: Block copolymer lithography makes use of the self-assembling properties of block copolymers to pattern nanoscale features over large areas. Although the resulting patterns have good short-range order, the lack of long-range order limits their utility in some applications. This work presents a lithographically assisted self-assembly method that allows ordered arrays of nanostructures to be formed by spin casting a block copolymer over surfaces patterned with shallow grooves. The ordered block copolymer domain patterns are then transferred into an underlying silica film using a single etching step to create a well-ordered hierarchical structure consisting of arrays of silica pillars with 20 nm feature sizes and aspect ratios greater than 3.

Fabrication of 10 nm enclosed nanofluidic channels

Abstract: We made uniform arrays of nanometer scale structures using nanoimprint lithography over large areas (100 mm wafers). The nanofluidic channels were further narrowed and sealed by techniques that are based on nonuniform deposition. The resulting sealed channels have a cross section as small as 10 nm by 50 nm, of great importance for confining biological molecules into ultrasmall spaces. These techniques can be valuable fabrication tools for Nanoelectromechanical Systems and Micro/Nano Total Analysis Systems.

Step and repeat imprint lithography processes

Abstract: The present invention is directed to methods for patterning a substrate by imprint lithography. Imprint lithography is a process in which a liquid is dispensed onto a substrate. A template is brought into contact with the liquid and the liquid is cured. The cured liquid includes an imprint of any patterns formed in the template. In one embodiment, the imprint process is designed to imprint only a portion of the substrate. The remainder of the substrate is imprinted by moving the template to a different portion of the template and repeating the imprint lithography process.

A new fabrication process for ultra-thick microfluidic microstructures utilizing SU-8 photoresist

Abstract: In this paper we describe a new process for fabricating ultra-thick microfluidic devices utilizing SU-8 50 negative photoresist (PR) by standard UV lithography. Instead of using a conventional spin coater, a simple 'constant-volume-injection' method is used to create a thick SU-8 PR film up to 1.5 mm with a single coating. The SU-8 PR is self-planarized during the modified soft-baking process and forms a highly-uniform surface without any edge bead effect, which commonly occurs while using a spin coater. Photomasks can be in close contact with the PR and a better lithographic image can be generated. Experimental data show that the average thickness is 494.32 ± 17.13 μm for a 500 μm thick film (n = 7) and the uniformity is less than 3.1% over a 10 × 10 cm2 area. In this study, the temperatures for the soft-baking process and post-exposure baking are 120 °C and 60 °C, respectively. These proved to be capable of reducing the processing time and of obtaining a better pattern definition of the SU-8 structures. We also report on an innovative photomask design for fabricating ultra-deep trenches, which prevents the structures from cracking and distorting during developing and hard-baking processes. In this paper, two microfluidic structures have been demonstrated using the developed novel methods, including a micronozzle for thruster applications and a microfluidic device with micropost arrays for bioanalytical applications.

Fabrication of 70 nm channel length polymer organic thin-film transistors using nanoimprint lithography

Abstract: We report on the fabrication of short-channel polymer organic thin-film transistors (OTFTs) using nanoimprint lithography. Currently, there is significant interest in OTFTs due to their potential application in inexpensive, large-area electronics. However, polymer carrier mobilities are typically poor, and thus to increase the OTFT drive current per unit area, there is a need for short-channel devices. We have fabricated working devices with channel lengths from 1 μm down to 70 nm with high yields. The performance of these devices was studied as the channel length was reduced. We find that drive current density increases as expected, while the on/off current ratio remains 104. However, at short-channel lengths, OTFTs no longer saturate due to space charge limiting current effects.

A spacer patterning technology for nanoscale CMOS

Abstract: A spacer patterning technology using a sacrificial layer and a chemical vapor deposition (CVD) spacer layer has been developed, and is demonstrated to achieve sub-7 nm structures with conventional dry etching. The minimum-sized features are defined not by the photolithography but by the CVD film thickness. Therefore, this technology yields critical dimension (CD) variations of minimum-sized features much smaller than that achieved by optical or e-beam lithography. In addition, it also provides a doubling of device density for a given lithography pitch. This method is used to pattern silicon fins for double-gate metal-oxide semiconductor field effect transistors (MOSFETs) (FinFETs) and gate electrode structures for ultrathin body MOSFETs. Process details are presented.

Step and repeat imprint lithography systems

Abstract: Described are systems for patterning a substrate by imprint lithography. Imprint lithography systems include an imprint head configured to hold a template in a spaced relation to a substrate. The imprint lithography system is configured to dispense an activating light curable liquid onto a substrate or template. The system includes a light source that applies activating light to cure the activating light curable liquid.

Nanoscale CMOS spacer FinFET for the terabit era

Abstract: A spacer lithography process technology, which uses a sacrificial layer and spacer layer formed by chemical vapor deposition (CVD), has been developed. It has been applied to make a sub-40-nm Si-fin structure for a double-gate FinFET with conventional dry etching for the first time. The minimum-sized features are defined not by the photolithography but by the CVD film thickness. Therefore, this spacer lithography technology yields better critical dimension uniformity than conventional optical or e-beam lithography and defines smaller features beyond the limit of current lithography technology. It also provides a doubling of feature density for a given lithography pitch, which increases current by a factor of two. To demonstrate this spacer lithography technology, Si-fin structures have been patterned for planar double-gate CMOS FinFET devices.

Adjustment of masks for integrated circuit fabrication

Abstract: A pattern-dependent model is used to predict characteristics of an integrated circuit that is to be fabricated in accordance with a design by a process. The process includes (a) a fabrication process that will impart topographical variation to the integrated circuit and (b) a lithography or etch process, the lithography or etch process using a mask produced from the design. The lithography or etch process and the fabrication process interact to cause the predicted characteristics to differ from the design. The mask is adjusted in response to characteristics predicted by the model, to reduce the effect of the interacting of the lithography or etch process and the fabrication process. A location on an integrated circuit is predicted for which a lithography tool would not produce a satisfactory feature dimension without a degree of adjustment of the tool during fabrication to accommodate a focus limitation of the tool, and the design of at least one mask derived from the design is adjusted to enable the lithography tool to produce a satisfactory feature dimension at the locations. A virtual adjustment is effected of a distance of a lithographic tool from a location in a region of a wafer, the virtual adjustment being effected by using a mask having a mask layout that has been generated based on a pattern-dependent model prediction that the location in the region of the wafer would not otherwise have a satisfactory feature dimension due to a focus limitation of the lithographic tool. A pattern-dependent model is used to predict topography variations that will occur in an integrated circuit as a result of processing up to a predetermined lithographic process step, and designs of masks used in the lithographic process step are adjusted to accommodate the topography variations.

Alignment methods for imprint lithography

Abstract: Described are methods for patterning a substrate by imprint lithography. Imprint lithography is a process in which a liquid is dispensed onto a substrate. A template is brought into contact with the liquid and the liquid is cured. The cured liquid includes an imprint of any patterns formed in the template. Alignment of the template with the substrate is performed prior to curing the liquid. Alignment of the template with the substrate includes rotational alignment of the template with respect to the substrate.

Capillary Force Lithography: Large‐Area Patterning, Self‐Organization, and Anisotropic Dewetting

Abstract: This article gives an overview on a new lithographic technique called capillary force lithography for large-area patterning. The technique simply involves placing a polydimethylsiloxane mold on a polymer film, which is then heated above the glass-transition temperature of the polymer. Various useful microstructures can be obtained by sequential applications of the technique through self-organization. Dewetting, which can be observed in capillary force lithography for relatively thin films, is also described as a new pathway for realizing anisotropic dewetting.

Alignment systems for imprint lithography

Abstract: Described are systems for patterning a substrate by imprint lithography. Imprint lithography systems include an imprint head configured to hold a template in a spaced relation to a substrate. The imprint lithography system is configured to dispense an activating light curable liquid onto a substrate or template. The system includes a light source that applies activating light to cure the activating light curable liquid. Multiple optical imaging devices are used to align the template with the substrate.

Fabrication of photonic crystals in silicon-on-insulator using 248-nm deep UV lithography

Abstract: We demonstrate wavelength-scale photonic nanostructures, including photonic crystals, fabricated in silicon-on-insulator using deep ultraviolet (UV) lithography. We discuss the mass-manufacturing capabilities of deep UV lithography compared to e-beam lithography. This is illustrated with experimental results. Finally, we present some of the issues that arise when trying to use established complementary metal-oxide-semiconductor processes for the fabrication of photonic integrated circuits.

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.

Fabrication of magnetic microfiltration systems using soft lithography

Abstract: Arrays of nickel posts were used as magnetic elements in a microfiltration device that is compatible with microfluidic systems. The combination of microtransfer molding—a soft lithography technique—and electrodeposition generated nickel posts ∼7 μm in height and ∼15 μm in diameter inside a microfluidic channel. Once magnetized by a magnetic field from an external, permanent, neodymium–iron–boron magnet, these nickel posts generated strong magnetic field gradients and efficiently trapped superparamagnetic beads moving past them in a flowing stream of water. These nickel post arrays were also used to separate magnetic beads from nonmagnetic beads.

Nanoscale patterning of magnetic islands by imprint lithography using a flexible mold

Abstract: A nanomolding process for producing 55-nm-diameter magnetic islands over 3-cm-wide areas is described. A master pattern of SiO2 pillars is used to form a polymeric mold, which is in turn used to mold a photopolymer resist film. This latter film is used as a resist for etching SiO2, yielding a pattern of pillars. Finally, an 11-nm-CoPt multilayer is deposited. Magnetic force microscopy reveals that the film on top of each pillar is a magnetically isolated single domain that switches independently.

Fabrication of aligned microstructures with a single elastomeric stamp.

Abstract: The fabrication of complex patterns of aligned microstructures has required the use of multiple applications of lithography. Here we describe an approach for microfabrication that encodes the two-dimensional spatial information of several photomasks onto a single elastomeric stamp by mapping each photomask onto distinct heights on the surface of the stamp. Pressing the stamp against a surface collapses the topography of the stamp such that each recessed layer contacts the surface in stepwise sequence; the greater the applied pressure, the larger the area of the stamp that contacts the surface. After contact of each new layer with the surface, we use techniques of soft lithography (microcontact printing, microfluidics, and patterning through membranes) to pattern the surfaces that contact the stamp and those that do not with inorganic, organic, or living materials. Microfabrication through the use of multilevel stamps provides a promising alternative to conventional lithography for the construction of multicomponent, aligned surfaces; these structures may find use as components of microfluidic devices or biological patterns.

Generation of 30-50 nm structures using easily fabricated, composite PDMS masks.

Abstract: This communication demonstrates an approach to generate simple nanostructures with critical dimensions down to 30 nm over cm2-sized areas using composite PDMS masks. These masks were patterned with feature sizes down to 100 nm. When used in phase-shifting lithography, these masks generated arrays of structures in photoresist with line widths as small as 30 nm, slots in metal with features down to 40 nm, and wells in epoxy with diameters as small as 100 nm. The wells were used to prepare arrays of uniformly sized nanocrystals of salts.

Holder, system, and process for improving overlay in lithography

Abstract: A deformable holder, system, and process where long range errors (any of lithography, metrology, or overlay errors) between the image of a mask and an existing pattern on a wafer from a number of potential sources are corrected The long range errors are determined using either a through-the-lens alignment metrology system or an around-the-lens metrology system Deformation values are determined to compensate for the longe range errors The deformation values are determined by either solving simultaneous equations or by finite-element linear-stress-analysis (FEA) The mask or wafer is then distorted, in-plane, by an amount related to the determined deformation values using an actuator such an a piezoelectric ceramic to push or pull the mask or wafer to substantially realign the projected image of the mask and the existing pattern on the wafer

Capacitive-type humidity sensors fabricated using the offset lithographic printing process

Abstract: This paper reports on the fabrication of a novel capacitive-type relative humidity sensor of which the electrode films are deposited using the high speed printing process, offset lithography. Parallel-plate capacitor sensor structures have been formed with a number of humidity sensitive polymers including polyimide and polyethersulphone (PES). Details of the fabrication process and sensor characteristics such as linearity, sensitivity and response time are included.

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.

Fabrication of Arrays of Microlenses with Controlled Profiles Using Gray-Scale Microlens Projection Photolithography

Abstract: This paper demonstrates the use of microlens projection lithography using gray-scale masks to fabricate arrays of microstructures in photoresist In microlens projection lithography, an array of microlenses (diameter d = 1−1000 μm) reduces a common, centimeter-scale pattern in an illuminated mask to a corresponding pattern of micrometer-scale images in its image plane The pattern of intensity projected by the array of microlenses depends on the shape and gray-level distribution of the pattern on the illuminated mask and on the shape and pattern of the lenses The distribution of intensity in the microimages could be adjusted using gray-scale masks After the recording of this intensity distribution in layers of photoresist and developing, the developed resist showed arrays of 3D microstructures over areas larger than 10 cm2 We used these arrays of 3D microstructures as masters and cast transparent elastomer onto them to generate complementary replicas For a specific microlens array and a fixed light so

A novel approach to produce biologically relevant chemical patterns at the nanometer scale: Selective molecular assembly patterning combined with colloidal lithography

Abstract: A novel patterning technique that combines colloidal patterning with selective adsorption of organic molecules has been used to chemically pattern metal oxide surfaces at length scales down to 50 nm. Lithographic nanofabrication using surface-assembled colloids as etch masks (“colloidal lithography”) was used to create nanopillars of TiO2 (50−90 nm in diameter, ∼20 nm in height) on whole oxidized silicon or quartz wafer substrates. These nanopillars were then rendered hydrophobic by the selective self-assembly of an organophosphate, whereas a poly(ethylene glycol)-grafted copolymer was adsorbed onto the surrounding SiO2 rendering it protein resistant. This resulted in a two-component chemical pattern, displaying contrast with respect to protein adsorption (protein-adhesive pillars on nonadsorbing background). This property allows for efficient translation of the lithographic pattern into a surface protein pattern by two simple dip-and-rinse processes in aqueous solutions. The feasibility of the method and...

Near-field two-photon nanolithography using an apertureless optical probe

Abstract: Near-field two-photon optical lithography is demonstrated by using ∼120 fs laser pulses at 790 nm in an apertureless near-field optical microscope, which produces lithographic features with ∼70 nm resolution. The technique takes advantage of the field enhancement at the extremity of a metallic probe to induce nanoscale two-photon absorption and polymerization in a commercial photoresist, SU-8. Even without optimization of the resist or laser pulses, the spatial resolution of this technique is as high as λ/10, nearly a factor of 2 better than techniques based on far field two-photon lithography.