Showing papers on "Focused ion beam published in 1996"

Focused ion beam applications to solid state devices

Abstract: The current state of focused ion beam (FIB) applications in relation to solid state devices is reviewed, and recent use of FIB technology for lithography, etching, deposition, and doping are described. Etching and deposition have become essential processes for failure analysis and for mask repair in silicon ULSL production. Furthermore, the FIB doping technique has been used to fabricate quantum effect devices.

Ion beam process for deposition of highly wear-resistant optical coatings

Abstract: An ion beam deposition method is provided for manufacturing a coated substrate with improved wear-resistance, and improved lifetime. The substrate is first chemically cleaned to remove contaminants. Secondly, the substrate is inserted into a vacuum chamber onto a substrate holder, and the air therein is evacuated via pump. Then the substrate surface is bombarded with energetic ions from an ion beam source supplied from inert or reactive gas inlets to assist in removing residual hydrocarbons and surface oxides, and activating the surface. After sputter-etching the surface, a protective, wear-resistant coating is deposited by plasma ion beam deposition where a portion of the precursor gases are introduced into the ion beam downstream of the ion source, and hydrogen is introduced directly into the ion source plasma chamber. The plasma ion beam-deposited coating may contain one or more layers. Once the chosen coating thickness is achieved, deposition is terminated, vacuum chamber pressure is increased to atmospheric and the coated substrate products having wear-resistance greater than glass are removed from the chamber. These coated products may be ceramics, architectural glass, analytical instrument windows, automotive windshields, and laser bar code scanners for use in retail stores and supermarkets.

Process method and apparatus using focused ion beam generating means

Abstract: A processing method and a processing apparatus realizing the method use a focused ion beam generator. The apparatus includes a plasma or liquid metal ion source producing ions not influencing electric characteristics of a sample, an ion beam generator for extracting ions from the ion source into an ion beam, an ion beam focusing device for focusing the ion beam, an irradiator for irradiating the focused ion beam onto the sample, and a sample chamber in which the sample to be irradiated for processing is installed. The focused ion beam is irradiated onto a sample such as a silicon wafer or device to conduct on a particular position of the sample a fine machining work, a fine layer accumulation, and an analysis.

Fundamental limits to imaging resolution for focused ion beams

Abstract: This article investigates the limitations on the formation of focused ion beam images from secondary electrons. We use the notion of the information content of an image to account for the effects of resolution, contrast, and signal‐to‐noise ratio and show that there is a competition between the rate at which small features are sputtered away by the primary beam and the rate of collection of secondary electrons. We find that for small features, sputtering is the limit to imaging resolution, and that for extended small features (e.g., layered structures), rearrangement, redeposition, and differential sputtering rates may limit the resolution in some cases.

Cross-sectional sample preparation by focused ion beam : a review of ion-sample interaction

Abstract: A focused ion beam (FIB) was applied for cross-sectional sample preparation with both transmission electron microscopes (TEM) and scanning electron microscopes (SEM). The FIB sample preparation has the advantage of high positioning accuracy for cross sections. On the other hand, a broad ion beam (BIB) has been conventionally used for thinning TEM samples. Although both FIB and BIB use energetic ion beams, they are essentially different from each other in many aspects such as beam size, beam current density, incident angle of the beam with respect to cross sections, and beam scanning (i.e., dynamic or static beam). In this study, FIB cross-sectioning is compared with BIB thinning. We review inherent characteristics such as positioning accuracy and uniformity of cross section, radiation damage, and beam heating. Discussion is held from a view-point of ion beam and sample interaction.

Spatiotemporal near-field spin microscopy in patterned magnetic heterostructures.

Abstract: Low temperature femtosecond-resolved near-field scanning optical microscopy is used to image excitonic spin behavior in locally disordered magnetic semiconductor heterostructures. A contrast between luminescence intensity and polarization profiles yields marked differences between carrier diffusion and spin transport over a spin-dependent energy landscape sharply defined by focused ion beam implantation. Space-time spectroscopies reveal a spin component to the exciton evolution in the presence of a magnetic field. Fundamental limitations on the measurement of circularly polarized luminescence in the near field are also demonstrated.

Focused ion beam metrology

Abstract: A focused ion beam metrology device and method are disclosed. A focused ion beam is used to measure dimensions of semiconductor features, such as top-down linewidth measurement. Low intensity focused ion beams form top view images of the semiconductor. High intensity focused ion beams etch the semiconductor in the presence of etch-enhancing material. A crater is etched to expose a cross-section the of semiconductor. The cross-section is imaged by directing low intensity focused ion beams toward the cross-section. This may be achieved by tilting the semiconductor. A three dimensional profile of a feature may be formed by successively etching the feature top surface and forming a top view image thereof. Overlaying the successive top view images forms the three dimensional profile.

Micrometer-scale machining: tool fabrication and initial results

Abstract: Conventional milling techniques scaled to ultrasmall dimensions have been used to machine polymethyl methacrylate (PMMA) with micrometer-sized milling tools. The object of this work is to achieve machining of a common material over dimensions exceeding 1 mm while holding submicrometer tolerances and micrometer size features. Fabricating the milling tools themselves was also an object of the study. A tool geometry for nominal 25 micrometer diameter cutting tools was found that cuts PMMA with submicrometer tolerances over trench lengths of 2 mm. The tool shape is a simple planar facet cut by focused ion beam milling on ground and polished 25 micrometer diameter steel tool blanks. Pairs of trenches 24 micrometers wide, 26 micrometers deep, 2.3 mm long, with a 14 micrometer separation were milled under various machining conditions. The results indicate that the limits of the machining process in terms of speed, pattern complexity, and tolerances have not been approached. This is the first demonstration of a generic method for microtool making by focused ion beam machining combined with ultraprecision numerically controlled milling. The method is shown to be capable of producing structures and geometries that are considered inaccessible by conventional materials removal techniques, and generally regarded as applications for deep X-ray lithography.

New broad beam gas ion source for industrial application

Abstract: A source delivering a broad, high current ion beam compatible with both chemically active and inert gases has been developed which gives reliable, long term, maintenance‐free operation. It uses a glow discharge with a cold cathode in a magnetic field where a dense uniform plasma is generated in large volumes at low gas pressures. Optimal selection of the electrode configuration and magnetic field ensures operation at pressures lower than 0.1 Pa in pulse–periodic mode (1–10 A discharge current, 1 ms pulse length, 25–50 Hz frequency), and continuous mode (discharge current up to 2 A). The current density of a 15‐cm‐diam beam can reach 10 mA cm−2 in the former, and 1 mAcm−2 in the latter. Tests with a 50‐cm‐diam discharge chamber show the uniformity of the ion emission current to be better than ±10%, confirming that the technology is scaleable, and that beams of up to 2000 cm2 cross‐sectional area can be obtained without loss of beam uniformity through appropriate design of the extraction system. The source is completely reactive gas‐compatible, generating ion beams from oxygen, nitrogen, argon or ionized CH radicals (e.g., using C3H8). Mass‐charge beam analysis shows the beams generated to be of high purity (≳99%). Applications include low energy (1–3 keV) ion beam cleaning of glass, ceramic and metal surfaces prior to the deposition of protective and decorative coatings such as TiN and diamondlike carbon, ion beam assisted deposition, and high energy gas ion implantation using, e.g., pulse–periodic beams of ions with energies up to 50 keV.

Investigations on the topology of structures milled and etched by focused ion beams

Abstract: For high precision micromachining of micro‐ and nanostructures by focused ion beams, the precision of the material removal process is of great importance. In this article, the topological properties of the ion beam generated structures like slope angles of trenches, surface roughness, and induced defects are investigated. The influence of the beam current and scanning strategy on the topological properties will be discussed. In addition, transmission electron microscopy analysis of thin lamellas generated by focused ion beams will be shown.

Friction and pull-off force on silicon surface modified by FIB

Abstract: The friction and adhesion forces have been measured for silicon surfaces with various patterns having cyclic asperity. The patterns are created by using a focused ion beam (FIB) to mill ditches and to deposit platinum mounds. To study the effect of cyclic asperity on the forces, the friction and pull-off forces have been measured between the pattern and a flat, square scanning probe (0.7 μm × 0.7 μm) of an atomic force microscope (AFM). Both the friction and pull-off forces decrease as the asperity increases (i.e., as the ditch depth or mound height increases). The friction force is proportional to the pull-off force, which indicates the importance of reducing the adhesion force when devising lubrication methods for micromachines and microelectromechanical systems (MEMS).

Recent Advances in Vacuum Arc Ion Sources

Abstract: Intense beams of metal ions can be formed from a vacuum arc ion source. This kind of source works well for most of the solid metals of the Periodic Table, and because the ions are, in general, multiply stripped with charge states as high as 4+ to 6+ , the mean energy of the ion beam produced can be 100–200 keV for an extractor voltage in the comfortable range of about 50–75 kV. Broad-beam extraction is convenient, and the time-averaged ion beam current delivered downstream can readily be in the tens of milliamperes range. The vacuum arc ion source has, for these reasons, found good application for metallurgical surface modification: it provides relatively simple and inexpensive access to high dose metal ion implantation. Several important source developments have been demonstrated recently, including very-broad-beam operation, macroparticle removal, charge state enhancement and the formation of gaseous beams. We have made a very-broad-beam source embodiment with beam formation electrodes 50 cm in diameter (area, 2000 cm 2 ), producing a beam with a width of approximately 35 cm for a nominal beam area of about 1000 cm 2 , and a pulsed Ti beam current of about 7 A was formed at a mean ion energy of approximately 100 keV. Separately, we have developed a high efficiency macroparticle-removing magnetic filter and have incorporated such a filter into a vacuum arc ion source so as to form macroparticle-free ion beams. Jointly with researchers at the High Current Electronics Institute, Tomsk, Russia and the Gesellschaft fur Schwerionenforschung, Darmstadt, Germany, we have developed a compact technique for increasing the charge states of ions produced in the vacuum arc plasma, thus providing a simple means of increasing the ion energy at fixed extractor voltage. Finally, operation with mixed metal and gaseous ion species has been demonstrated. In this paper, we briefly review the operation of vacuum arc ion sources and the typical beam and implantation parameters that can be obtained, and describe these source advances and their bearing on metal ion implantation applications.

Tetramethoxysilane as a precursor for focused ion beam and electron beam assisted insulator (SiOx) deposition

Abstract: Focused ion beams are intensively used for device modification by local material removal and ion beam induced metal deposition. With shrinking dimensions on modern multilayer devices, the need for ion beam induced insulator deposition is increasing. In this article, tetramethoxysilane as a precursor for ion beam induced deposition has been investigated. The influence of beam parameters dwell time and loop time on the material deposition rate will be discussed and compared to model calculations. For optimized scanning conditions, a maximum deposition rate of 0.33 μm3/nC was found. Insulating films were also deposited using an electron beam. The chemical composition and electrical properties of these films were compared with the films deposited by the ion beam. For electron beam deposition, the resistivity of the deposited films was 1×106 Ω cm which is two orders of magnitude higher than for ion beam deposited film.

Charged particle beam system with optical microscope

Abstract: A charged particle beam system such as a focused ion beam system includes a vacuum chamber; an optical microscope located so as to have a filed of view within a first region of the chamber; a laser aligned with the optical microscope so as to project a laser beam into the first region; a charged particle beam column located within the chamber and arranged so as to focus a charged particle beam into a second region of the chamber; and specimen support located in the chamber and moveable between a first position in the first region and a second position in the second region. The laser is used to mark a DUT with a registration mark which is visible in the images from the optical microscope and the charged particle beam. The position of the registration mark can be accurately determined in the optical image and the position of features which would otherwise be invisible in the charged particle beam image inferred.

Parallel ion optics and apparatus for high current low energy ion beams

Abstract: A device for the parallel processing of ions is provided. The device may be utilized for thin film deposition or ion implantation and may include the following: an ion source, ion capture and storage ion optics, mass selection ion optics, neutral trapping elements, extraction ion optics, beam neutralization mechanisms, and a substrate on which deposition and thin film growth occurs is provided. Ions are captured and stored within a closely packed array of parallel ion conducting channels. The ion conducting channels transport high current low energy ions from the ion source to irradiate the substrate target. During transport, ion species can be mass selected, merged with ions from multiple sources, and undergo gas phase charge exchange ion molecule reactions. Additionally, neutrals from the ion source, ion-molecule reaction reagent gases, residual background gas, or neutralization of ions may be eliminated from the processing stream by turbo pumping, cryo pumping, and cryocondensation on some of the ion optic elements. Different types of ion optic elements, including elements which are parallel or perpendicular to the ion path, and neutral trapping elements may be combined in different ways to achieve thin film ion deposition over a large homogenous substrate surface.

Integrated circuit having reprogramming cell

Abstract: An integrated circuit is reprogrammable in metal using (a) a set of spare devices, and (b) separate arrays of spare rows and columns. The spare rows are formed in the top metal layer, and the spare columns are formed in the next to the top metal layer (for example, metal layers 4 and 5 of a 5 level metal process). Use of arrays of spare rows/columns facilitates silicon debug of the integrated circuit using FIB (focused ion beam) reprogramming without requiring FIB connections of more than 500 μm.

A proximity ion beam lithography process for high density nanostructures

Abstract: Image contrast in proximity ion beam lithography is limited by scattered ions which enter the opaque regions of the mask and exit through the sidewalls of the mask windows. The scattering angles are widely distributed resulting in a ‘‘proximity effect’’ whose range is on the order of the mask‐to‐wafer gap. This problem becomes more severe with increasing pattern density and sets the resolution limit for high density patterns such as interdigital transducers. The only way to counteract this effect is to limit the ion range to a fraction of the mask thickness so that the scattered ions can be recaptured by adjacent sidewalls. This article explores the dependence of image contrast on resolution, pattern density, and beam energy in proximity ion beam lithography. Patterns with feature sizes in the range from 20 to 50 nm and 0.4 μm pitch have been printed with a linewidth change of only 3 nm for a 10% change in dose.

Biaxial alignment of TiN films prepared by ion beam assisted deposition

Abstract: The biaxial alignment of TiN on Si(111) films prepared by nitrogen ion beam assisted deposition at room temperature was studied. By reactive deposition within a nitrogen environment a preferred {111} orientation was obtained the growing TiN crystallites. In contrast, a nitrogen ion bombardment perpendicular to the surface of the substrate during deposition causes an {001} alignment of the crystallites. A 55° ion beam incidence produces both {111}‐orientation relative to the surface and {100}‐orientation relative to the ion beam. This results in a totally fixed orientation of the crystallites. Simultaneous UV‐light illumination during ion bombardment promotes a uniformly oriented growth.

Modification of field emitter array tip shape by focused ion‐beam irradiation

Abstract: Tip shapes of Si field emitter arrays, fabricated by a conventional dry etching process, have been modified by focused ion‐beam (FIB) irradiation to obtain a sharp cone shape. Flat‐topped Si tips could be sharpened by localized sputtering using FIBs for a short time. Tip shape inspections and repairs were also performed using a FIB system combined with an electron‐beam column to remove metal residues and melted emitters.

Ultrahigh vacuum focused ion beam micromill and articles therefrom

Abstract: An ultrahigh vacuum focused ion beam micromilling apparatus and process are disclosed which can achieve high aspect ratios in a chemical-assist free environment. An ultrahigh vacuum chamber (10) includes a number of ports for viewing to a target substrate, for filming of the target substrate, for insertion or manipulation of the target substrate, and for various analyses of the target substrate. Port (12) can be a view port with port (14) being used for a camera port. Additionally, a durable data storage medium using the micromilling process is disclosed, the durable data storage medium capable of storing, e.g., digital or alphanumeric characters as well as graphical shapes or characters.

Method and apparatus for endpointing while milling an integrated circuit

Abstract: A method and an apparatus for endpoint determination when milling an integrated circuit disposed in a substrate. In one embodiment, the substrate is charged to a first polarity while the well regions and active diffusion regions of the integrated circuit are charged to another polarity thus resulting in an electrical bias at the P-N junctions in the substrate. By powering up the integrated circuit in this fashion during milling, endpoint detection can be accurately determined by using a voltage contrast mechanism such as the imaging detector of a focused ion beam (FIB) milling tool. A diffusion boundary can also be determined in accordance with the teachings of the invention by the use of the stage current monitor of the FIB milling tool. The diffusion boundary is determined in accordance with the teachings of the present invention by a change in contrast as detected by the imaging detector of the FIB milling tool or by a change in the stage current as measured by the stage current monitor of the FIB milling tool. By accurately determining when a diffusion boundary is reached, the present invention reduces the risk of inadvertently destroying diffusion regions when exposing features in an integrated circuit during debug.

Beam induced deposition of an ultraviolet transparent silicon oxide film by focused gallium ion beam

Abstract: We have deposited a silicon oxide (SiOx) film with a high optical transmittance in the DUV region by a focused ion beam induced deposition technique using a gallium ion beam and a mixture of oxygen and TMCTS(1,3,5,7‐tetramethylcyclotetrasiloxane) as a source gas. The optical transmittance of a 0.3 μm thick film is higher than 90% at the wavelength of 250 nm. The transmittance of the deposited SiOx film depends on both the source gas and ion beam irradiation conditions. A scaling to explain the transmittance along with the ion beam conditions is proposed.

Electron Beam Induced Deposition of Pt for Field Emitter Arrays

Abstract: Pt emitters were deposited using electron-beam-induced reaction on overetched Si emitters fabricated by a conventional dry etching process. An emission current of 10 µA was obtained from a 100-tip field emitter array (FEA) at an extraction voltage of 100 V. A prototype of a nanometer-sized field emitter was fabricated using focused ion beam (FIB) etching and electron-beam-induced deposition (EBID).

Dual Function of Thin MoO3 and WO3 Films as Negative and Positive Resists for Focused Ion Beam Lithography

Abstract: Fine patterning and metallization technologies have been studied using a combination of refractory metal oxide ( MoO3 and WO3) resists and Ga+ focused ion beam (FIB) lithography. In this work, it is demonstrated that depending on the preparation condition of the films, these thin oxide films act as either a negative or a positive resist with high-contrast capability. According to the results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses, the negative resist mechanism is possibly due to an FIB-induced structural change from the amorphous to the ordered state, and the positive resist mechanism is due to a change from the polycrystalline to the disordered state. In both the negative and positive cases, the delineated patterns can be directly reduced to fine Mo or W wires. The potential applications of the observed dual function of oxide resists are also discussed.

Dose‐rate effects in GaAs investigated by discrete pulsed implantation using a focused ion beam

Abstract: The dependence of the retained lattice damage upon dose rate was investigated by focused ion beam (FIB) implantation of 210 keV Si++ into GaAs at room temperature. The as‐implanted and postannealed states were characterized by ion channeling and Hall‐effect measurements, respectively. Dose‐rate effects arise from stabilizing interactions between populations of defects produced by different ions, and these experiments were designed to probe the time constants of those interactions. In the context of dose‐rate experiments, direct‐write FIB represents a much more controllable means of implantation over conventional broad beams since the exact timing of dose delivery may be precisely defined and varied. In this work, the final implanted dose was achieved by the successive application of individual flux pulses of constant intensity but of varying duration td and repetition period tr. A consistent trend toward a greater concentration of displaced atoms directly after implantation and a higher sheet resistance a...