Showing papers on "Focused ion beam published in 1983"

Maskless etching of a nanometer structure by focused ion beams

Abstract: Microfocused heavy ion beams obtained from liquid metal ion sources of gallium, indium, and tin are bombarded onto silicon and gallium arsenide substrates, and the amorphous regions created are selectively dissolved in suitable etchants (ion bombardment enhanced etching). The area exposure doses required to etch to the depth of the calculated projected range of the incident ions are in the region of 5×10−6∼1×10−5 C/cm2 at accelerating voltages of 30∼50 kV,and the dose dependencies of the etched depths show rapid increases in specified dose regions. Widths of etched depths obtained in line delineations depend on a line exposure dose, and the minimum linewidth clearly obtained is 20∼40 nm for all the ion beams. From measurements of the dose dependencies of linewidth, the beam diameters are evaluated for various conditions of the source operation and of a lens acceptance half‐angle. The virtual crossover diameters that are independent of the half‐angle, are found to be 40∼50 nm for the gallium source and 67 ...

Electron and ion beam apparatus and passivation milling

Abstract: A three element asymmetric lens system having a very low chromatic aberration coefficient is used in conjunction with a TFE electron source having an angular intensity of approximately 10-3 amperes per steradian to achieve precise focusing of the resulting electron beam despite the large energy spread thereof for beam, accelerating ratios in the range from 0.2 to 6.0. In one embodiment, an FI ion source is used in conjunction with the same type of lens system to initially visualize the surface of the integrated circuit. The ion beam then is rapidly focused on and scanned across a small area of passivation over an underlying metal conductor to sputter a hole through the passivation layer to the metal. A secondary electron collecting apparatus detects a large increase in the secondary electron emission when the ion beam reaches the metal. The electron beam then is scanned across the surface of the integrated circuit. The resulting secondary electrons are collected, amplified and input to the intensity control of a CRT, resulting in a display in which the brightness of the location of the milled hole accurately represents the voltage of the metal conductor.

Electrical Properties of Focused-Ion-Beam Boron-Implanted Silicon

Abstract: Electrical properties of 16 keV, focused-ion-beam (FIB) (beam diameter: 1 µm, current density: 50 mA/cm2) boron-implanted silicon layers have been investigated as a function of beam scan speed and ion dose, and compared with those obtained by conventional implantation (current density: 04 µA/cm2) High electrical activation of the FIB implanted layers is obtained by annealing below 800°C as a result of the increase in amorphous zones created in the implanted layers Amorphous zone overlapping is assumed to occur at FIB implantation doses of 3–4×1015 ions/cm2 from the results of electrical activation and the carrier profile of implanted regions annealed at low temperature, if beam scan speed is lowered to about 10-2 cm/s

Focused Si Ion Implantation in GaAs

Abstract: A 160-keV, submicron-focused Si ion implantation in MBE-GaAs was made using a 100 kV maskless implanter with a Au–Si–Be alloy ion source. Obtained Raman spectra indicated that compared with the implantation current densities of an unfocused ion beam, the higher current density (about 104 times greater) of the focused beam resulted in less implantation-induced and residual (after annealing up to 500°C) damage. Moreover, 850°C annealing led to a higher electrical activity of focused implanted Si-ions but almost the same optical quality of conventional implantation.

100 keV focused ion beam system with a E×B mass filter for maskless ion implantation

Abstract: Various liquid metal alloy ion sources and a 100 keV mass separated focused ion beam system have been fabricated and their basic characteristics have been measured. These are mass spectra, energy spread and angular current intensity for ion sources, and focusing characteristics of the system. It was observed that Be–Si–Au ternary alloy ion sources produce doubly charged Be and Si ions and the importance of these ion sources is demonstrated by fabricating a GaAs JFET using a maskless ion implantation technique and by PMMA resist exposure.

Focused ion beam microlithography using an etch‐stop process in gallium‐doped silicon

Abstract: We have found that silicon, when implanted with doses of gallium in excess of 1013 ions/cm2, experiences little or no etching in aqueous caustic solutions. By exploiting a finely focused 40–50 keV gallium ion beam (0.05–0.1 μm diameter) in our scanning ion microscope, we have shown that it is possible to fabricate structures with submicrometer (0.1 μm) features. The silicon behaves as a negative resist with a sensitivity of about 1 μC/cm2. This etch‐stop process is largely insensitive to crystallographic orientation, except for the highly insoluble (111) plane in which damage‐promoted etching occurs.

A 100 kV Maskless Ion-Implantation System with an Au–Si–Be Liquid Metal Ion Source for III-V Compound Semiconductors

Abstract: A newly developed Au–Si–Be liquid metal ion source has been incorporated to a 100 kV focused ion beam system. Among several ion species emitted from the single ion emitter, doubly ionized Si and Be have been selected by the crossed electric and magnetic field (E×B) mass separator and have been formed into a finely focused beam. This new system was found capable of focusing those ions down to a diameter of about 0.1 µm. It has also been found that, using the fine focusing for n- and p-doping, desired ion species (Si++ and Be++) can be exchanged simply by adjusting the electric field of the E×B mass separator.

Selective Si and Be implantation in GaAs using a 100 kV mass‐separating focused ion beam system with an Au–Si–Be liquid metal ion source

Abstract: Submicron Si and Be ion beams have been implanted into GaAs using a 100 kV maskless ion implantation system with a liquid metal ion source which is capable of emitting double ion species (Si++ and Be++). Both ion beams are implanted at 160 keV with the dose of 1013 to 1014 cm−2. The feasibility of the focusing column was demonstrated by forming the submicron width of line patterns of alternative Si and Be doping in GaAs including a pn junction array. The linewidth of the ion implanted area has been evaluated by SEM, after selective etching of the annealed sample. It has been found that high dose implantation results in considerable lateral impurity spread of more than 1 μm even with the focused ion beams with a diameter of 0.1 μm. However, submicron width implantation turns out to be possible with relatively low doses or with shallow dopings.

Non-mass-analyzed ion implantation

Abstract: A non-mass-analyzed ion implantation process wherein two or more species of ions of the same polarity having greatly different ion masses are generated from a compound source material, the ions are accelerated under the application of an electric field, and the accelerated ions are scanned under the application of a magnetic field so as to be implanted into a target at a distribution profile which varies with the species of ions. An ion implantation apparatus can be simplified. A large ion beam current with a large spot size can be used and ions can be implanted to the target at a large dose within a short time. Especially, the non-mass-analyzed ion implantation is advantageously utilized for production of solar batteries.

Maskless etching of GaAs and InP using a scanning microplasma

Abstract: Etching characteristics of GaAs, InP, and other materials using a scanning microplasma have been investigated. This technique utilizes enhanced reaction between a reactive ambient gas and a target at an excited region like a microplasma which is produced by irradiating a scanning focused ion beam. It was observed that the present technique gives an enhanced etching rate over a physical sputter etching and a very smooth etched surface. Dependence of etching rate on bombarding angle and reactant gas flow rate is also measured.

Ion beam carbon layers

Abstract: An article such as a tungsten carbide drill is coated with a hard carbon-rich layer by being first exposed to a beam of ions so as to sputter-clean the surface, and then exposed to a hydrocarbon vapour, while being bombarded with a beam of ions so as to cause cracking of hydrocarbon molecules condensing on the surface, The ion beam preferably consists of nitrogen ions from a twin- anode ion source.

Novel Method for Measuring Intensity Distribution of Focused Ion Beams

Abstract: We have developed a method for directly measuring the diameter of finely-focused ion beams from the response of the secondary electron emission that is obtained when the focused ion beam is scanned across the boundary of an AlGaAs/GaAs junction. Si and Be ion beams with diameters of less than 0.1 µm have been measured with an accuracy of 5% by this method. Thus, this technique is found useful for monitoring beam diameter during the maskless implantation process. Actually, this technique has been used for monitoring the diameters of Be and Si ion beams for the implantation of those beams into GaAs.

Preparation of Nuclear Accelerator Targets by Focused Ion Beam Sputter Deposition

Abstract: A duoplasmatron ion source with einzellens extraction was used to prepare focused beams of 10-30 kV of Ar ions with intensities of 1 mA. An em/m-analysis was performed to study the general behaviour of the source. The composition of the beam was investigated to trace and reduce contaminations from extraneous source materials. The Ar-ion beam was applied to sputter milligram-amounts of chemical elements and enriched isotopes of elements having high melting points, such as Zr, Mo, Ru, Ta, W, Ir, etc. The sputtered substances were collected in thicknesses varying from 0.01-2.0 mg/cm2 onto thin target backings of C, Ti, Cu, or Pb. Self-supported targets were obtained by dissolving backings chemically. Among others, targets of 182W and 184W with thicknesses from 0.19-0.65 mg/cm2 were thus prepared. Sputtering yields were measured for a series of different target materials. The results are discussed in detail. The targets have been fabricated for various experiments involving high intensity heavy ion bombardments with energies of up to 15 MeV/u of 58Ni, 208Pb, and 238U ions at the GSI UNILAC accelerator.

Electron beam probe for charge neutralization studies of heavy ion beams

Abstract: The design and operation of an electron beam probe for ion beam diagnostics is described. Advantages of this method for the analysis of space‐charge neutralization studies are discussed and examples of its applications to heavy ion beams are shown.

Lateral Spreads of Be and Si in GaAs Implanted with a Maskless Ion Implantation System

Abstract: Submicron Si and Be ion beams have been implanted into GaAs using a 100 kV maskless ion implantation system with a liquid metal ion source which is capable of emitting double ion species (Si++ and Be++). Both ion beams are implanted at 160 keV with the dose of 1012 to 1015 cm-2. The profiles of the implanted dopants have been estimated by observing the stain etching patterns on the cleaved planes before and after annealing. It has been found that high dose implantation results in a considerable lateral impurity spread of 1 µm or more, even with the focused ion beams having a diameter of 0.1 µm. However, doping of submicron width can be realized with relatively low doses or with shallow implantation.

Microelectronic and medical applications of an ion beam milling system

Abstract: An ion beam milling system utilizing a Kaufman-type source to etch patterns in conductive, semiconductive and insulating materials was used to examine the surface morphology of resistive thick films, and to modify the surface topography of biomaterials. The ion beam sputter modification of the different materials presently used or under consideration for electronic and implant devices were studied. A Japan Electron Optics Laboratory, model JSM-35 scanning electron microscope was used to examine all the materials tested.

Applications Of Focused Ion Beams

Abstract: A finely focused ion beam system is described. Beams of Ga, In, and Au ions emitted from a liquid metal ion source are routinely focused to spot diameters of ~0.1 to 3.0 μm at a current density of ~0.5 A/cm2 and a beam energy of 20 keV. Focused beams with energies of 1 to 30 keV have also been produced. Three applications are discussed: 1) scanning ion microscopy, 2) mask repair, and 3) ion beam lithography. Scanning ion images illustrating topographic and chemical contrast are presented. The repair of opaque and clear defects in optical masks, and opaque defects in X-ray masks is shown. Defects are imaged with the ion beam and removed by sputter erosion. Edge reconstruction of 0.5μm features is demonstrated. Most repairs take less than 10 sec per μm2. The advantages and limitations of ion beams for lithography are discussed.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Energy Deposition and Heat Flow for Pulsed Laser, Electron and Ion Beam Irradiation

Abstract: Energy deposition in times as short as tens of nanoseconds, with densities of joules/cm2, has emerged in the last few years as a new way of modifying the near surface structures of materials. The initial input came from the use of Q-switched laser pulses to anneal damage in ion implanted semiconductors. Interest in other areas, such as metallurgy, is now growing because of the possibility of forming new phases or new structures. The history of this field is reported in the proceedings of the annual meetings of the Materials Research Society dedicated to this subject since 1978 (Ferris et al., 1979; White and Peercy, 1980; Gibbons et al., 1981).

Multi-function charged particle apparatus

Abstract: An apparatus capable of simultaneous focusing, positioning, and scanning of an ion beam is described. The apparatus uses metallic elements to form the sides of an open-ended substantially box-shaped structure. Application of AC and DC currents to the four corners of the structure create AC and DC fields within the structure that deflect an ion beam so as to perform the functions of positioning, focusing, and scanning. The center of focusing of the ion beam is placed closer to the center of scanning of the ion beam than in conventional ion beam deflection systems. As a result, the tendency of space charge beam blow-up during scanning is greatly diminished. By combining the functions of positioning, focusing, and scanning in one deflection element, the length of an ion beam deflection system is reduced, and the current capability is greatly increased.

Compact Metal-Ion Beam Source Using Thermal Contact Ionizer

Abstract: A small, compact ion beam source which can function in an external magnetic field has been developed for use with a heavy ion beam probe for plasma diagnostics. The source consists of a thermal contact ionizer with a beam material reservoir and an electrostatic lens system for beam acceleration and focusing. The beam can be modulated by means of a beam-extracting electrode. An alkali or an alkali earth metal ion beam was produced at energies up to 3 keV. The source functioned sufficiently well in a magnetic field up to 2 kG. The operating parameters for Cs+ and Ba+ ion beams were investigated in detail. A beam current up to 10 µA and a small diameter of 1 mm at the focusing point were obtained.

An EBIS for Atomic Physics Experiments

Abstract: An electron beam ion source to be used in atomic physics experiments has been designed, constructed and partially tested. The source utilizes a conventional solenoid and an externally launched electron beam. Ultra-high vacuum in the ionization region of the source is provided by a distributed sputter-ion pump. The source is relatively simple in design and easy to operate. Thus far it has been used to produce ~ 300 eV/q multiply charged beams of carbon, nitrogen, oxygen, and possibly titanium.

Focused Ion Beams in Microelectronic Fabrication

Abstract: For more than 20 years the designers and fabricators of integrated circuits and microstructure devices have strived toward smaller features as a means of achieving higher packing density, better performance, and lower cost. The new field of microlithography has emerged as a result of these pressures. The results of these efforts are a wide array of advanced development and production techniques using photooptics, electrons, and X-rays as energy sources for pattern generation and replication. Over the past 3-4 years a new technique, focused ion beam lithography, has emerged as a challenger to these lithography tools for very large-scale integration (VLSI) research and production applications. A number of significant advantages exist when using focused beams in microelectronic fabrication that are not available in the technologies mentioned above. For example, the focused ion beam (FIB) may allow manufacturers to eliminate many of the process steps associated wish conventionai implantation since FIB implants can be performed without lithography and chemical processes. Special implant steps can also be done that are neither practical nor even possible with conventional photomasking techniques.

Ion-beam-neutralizing device

Abstract: PURPOSE:To perform neutralization of a positive ion beam efficiently at a low temperature by placing a secondary electron amplifier tube around a Faraday cage covering an ion beam and pouring secondary electrons discharged from the amplifier tube into a positive ion beam. CONSTITUTION:Gas containing an element such as phosphorus is supplied to an ion source 2 to produce an ion beam 3 which is then separated into specific kinds of ions by means of a magnet 4. The thus obtained specific kinds of ions by being passed through a slit 6 are formed into an implantation ion beam 3' and ion implantation is performed on a wafer 9 placed on the rotary disk 8 of an implantation chamber 7. A filament 10, a liberal electrode 15 and a multi- staged secondary electron amplifier tube 18 are installed outside a Faraday cage 13 covering the ion beam 3' so as to neutralize secondary electrons 12' of the amplifier tube 18 by pouring them into the ion beam 3', thereby extinguishing positive charges existing on the surface of the wafer 9. Therefore it is possible to obtain large secondary electrons with a small electric power and to perform a stable implantation efficiently.

Computer simulations of submicron FIB system optics

Abstract: The design of the optical elements for a focused ion beam (FIB) system having a 50 mm spot size over a 1 mm square field requires extensive computational analysis. We discuss the mathematical techniques applied to the components of interest in this submicron FIB system; the electrostatic lenses, the mass analyzer, and the electrostatic deflectors. The results of ion trajectory calculations predicted for the whole FIB column by the computer code snow are presented. The aberration coefficients to third order and a parametric study of a stigmatic Wien filter whose design includes entrance and exit fringe field effects will be considered. We also cover our optimization algorithms for selecting lens and deflector elements which demonstrate minimal chromatic and spherical aberrations and distortions. A spot symmetry and spot location map for the final 1 mm square field and its 50 nm image constraint is shown for mixed electronic configurations of dynamic focus, dynamic distortion, and dynamic stigmation correct...