Showing papers on "Focused ion beam published in 1993"

High‐resolution focused ion beams

Abstract: The technology of high‐resolution focused ion beams has advanced dramatically in the past 15 years as focusing systems have evolved from laboratory instruments producing minuscule current densities to high current density tools which have sparked an important new process: direct micromachining at the micrometer level. This development has been due primarily to the exploitation of field emission ion sources and in particular the liquid‐metal ion source. Originally developed in the early 1960’s as a byproduct of the development of electrostatic rocket engines, the liquid‐metal ion source was adapted for focused beam work in the late 1970’s, when it was demonstrated that submicrometer focused ion beams could be produced with current densities greater than 1 A cm−2. Ions can be produced with liquid‐metal ion sources from elements including Al, As, Au, B, Be, Bi, Cs, Cu, Ga, Ge, Fe, In, Li, P, Pb, Pd, Si, Sn, and Zn. In the past decade, focused ion beam systems with liquid‐metal ion sources have had a signific...

Novel scheme for the preparation of transmission electron microscopy specimens with a focused ion beam

Abstract: A novel scheme is presented for the preparation of cross‐section transmission electron microscopy (TEM) specimens, with a focused ion beam (FIB). This scheme is particularly suitable for highly structured substrates, such as integrated circuits. The specimen is made by cutting a thin slice of material from the substrate by sputtering with the FIB. The position of the specimen can be selected with submicron resolution. The specimen is subsequently removed from the substrate and transported to a standard TEM‐specimen holder. A specimen, ready for TEM inspection, can be prepared within 2 hs. The samples are of excellent quality as is illustrated with cross‐section TEM images of FIB‐made specimens of an electrically programmable read‐only memory.

A high-energy electron beam ion trap for production of high-charge high-Z ions

Abstract: We have developed a new high-energy electron beam ion trap, the first laboratory source of low-energy, few-electron, high- Z ions. We describe the device and report measurements of its performance, including the electron beam diameter, current density and energy, and measurements of the ionization balance for several high- Z elements in the trap. This device opens up a wide range of possible experiments in atomic physics, plasma physics, and nuclear physics.

A theory of ion beam induced charge collection

Abstract: The ion beam induced charge technique can image the depletion regions of microelectronic devices through their thick metallization and passivation layers, and buried dislocation networks in semiconductor material by measuring the number of charge carriers created by a focused MeV light ion beam scanning over the sample surface. In this paper it is shown how the charge pulse height can be calculated in terms of the ion type and energy, and the minority carrier diffusion length. The effect of surface layers, depletion layers, ion induced damage, and ion channeling on the measured charge pulse height are also considered. It is shown how this approach can be used to simulate the charge pulse height reduction due to ion induced damage.

Characteristics of gas‐assisted focused ion beam etching

Abstract: Gas‐assisted etching with a finely focused ion beam has been studied. The presence of a reactive gas, in this case Cl2, results in an enhanced etch rate compared to the rate for sputtering for many materials, including Si, Al, and GaAs. Other advantages over sputtering are the absence of redeposited material and the high etch selectivity possible with some material combinations, which has been exploited in the etching of microstructures. In some applications of this technique, a protective layer of low etch rate material is used over the substrate to improve the quality of the etched structure. The characteristics of the etching process have been studied with variation in the scan speed, gas flux, and current density into the scanned area. In general, a high scan speed, high gas flux, and low current density were found to give the maximum enhancement in the etch rate over sputtering. The application of these results to etching over a wide range of experimental conditions is discussed, to give a basis for estimating the etching results that would occur under other conditions.

Focused ion beam lithography

Abstract: Lithography for microelectronics, that is, the exposure and development of resist, is already being carried out in research laboratories at dimensions well below 0.1 μm. In production the minimum dimensions are likely to approach 0.1 μm before the end of the decade. This review will examine the use of focused ion beams for ultrafine lithography. Minimum dimensions down to 0.015 μm have been reported as well as exposure of 0.25 μm thick resist with o.05 μm linewidth for the making of X-ray lithography masks. At this time there are only two techniques for writing original patterns (as opposed to replicating them) at 0.1 μm and below; electron beams and ion beams. Electron beams are at a mature state of development and have advantages in absence of shot noise and in fast deflection capability. Ion beams on the other hand have demonstrated absence of proximity effect and high resist sensitivity, i.e. potentially faster writing speed. The development of the gas field ion source promises hundredfold increase in current density of light ions (H2+, He …) in the beam focal spot. In addition, these light ion beams at high energy can be deflected at the speeds needed for lithography. Thus focused ion beam lithography is a serious candidate for future fine pattern writing.

Focused‐ion beam induced deposition of copper

Abstract: As the dimensions of integrated circuits (ICs) decrease into the submicron range, the problems of circuit delay and interconnect reliability become more urgent. Due to its low resistivity (1.67 μΩ cm) and high electromigration resistance, copper has received attention as a candidate metal for the ICs of the future. In addition, the focused‐ion beam (FIB), with its capability for milling and deposition at linewidths of 0.1 μm or below, has proved useful as a tool for integrated IC ‘‘microsurgery.’’ FIB induced deposition of copper from a novel organometallic precursor compound, Cu(hfac)TMVS, has been achieved using 25–35 keV Ga+ ions from a liquid metal ion source. Submicron copper lines deposited at room temperature from this precursor exhibit resistivities as low as 50 μΩ cm; a sharp drop in these values is noted for deposition above 67 °C, and deposition on a substrate heated above ∼100 °C yields resistivities near those of pure bulk copper. Composition analysis by Auger electron spectroscopy shows the ...

Shallow Si p+‐n junctions fabricated by focused ion beam Ga+ implantation through thin Ti and TiSi2 layers

Abstract: Focused ion beam Ga+ implantation through Ti metal (ITM) and TiSi2 (ITS) layers, followed by rapid thermal annealing (RTA), has been investigated for application in self‐aligned silicide technology. The Ga+ energy was varied from 25 to 50 keV at doses of 1×1013 and 1×1015 cm−2 followed by RTA at 600 °C for 30 s. Depth profiles of the Ga implants were obtained by performing secondary‐ion mass spectrometry. It was observed that higher‐energy and higher‐dose implants yielded good quality p+‐n junction characteristics. Diodes were fabricated to obtain the electrical properties of these silicided junctions. At higher implant energies (≥40 keV) and all doses, I‐V characteristics of ITS diodes showed 100 times lower leakage currents (Ir) than ITM diodes. For low‐energy (<40 keV)/high‐dose implantation the ITS diodes showed a slight improvement in Ir over the ITM diodes, whereas for low‐energy/low‐dose implantation the same Ir was observed.

New characterization method of ion current‐density profile based on damage distribution of Ga+ focused‐ion beam implantation in GaAs

Abstract: A new method is reported for characterizing focused ion probe current distributions based on the comparison between damage simulations and transmission electron microscopy observations. Several focused‐ion beam operation conditions were modeled, such as low‐to‐high source emission currents and variable beam acceptances. At low current and small acceptance, the ion spot exhibits a nearly Gaussian profile, otherwise larger tails are evidenced which can be modeled either by Pearson or ‘‘bi‐Gaussian’’ distributions. The sensitivity of the procedure to the tail extension is highlighted.

An application of scanned focused ion beam milling to studies on the internal morphology of small arthropods

Abstract: For the first time a scanned focused ion beam of approximately 50 nm diameter has been used to prepare biological material. Small defined areas of the surface were removed by ion etching to allow examination of the underlying structures with a scanning electron microscope. Different milling procedures were carried out on two anatomical features in mites of the genus Halarachne (Halarachnidae: Mesostigmata). In the first, square holes were milled into the surface of the peritrematal plate to reveal the structure of the underlying respiratory peritrematal groove. In the second, transverse cuts were made across the shafts of the sensory sensilli which make up the sensory Haller's organ on tarsus I. This latter procedure revealed detail both within the core and walls of sensilli. Details of specimen preparation and milling procedures, as well as suitability and interpretation of results, are presented.

Doping-induced selective area photoluminescence in porous silicon

Abstract: The incubation time (ti) for the onset of porous Si formation by stain etching in HF:HNO3:H2O was observed to be a strong function of dopant type and concentration. For B‐doped p‐Si, ti increased significantly with substrate resistivity (ρ), from ∼0.5 min for 0.004 Ω cm to ∼9 min for 50 Ω cm. P‐doped n‐Si substrates exhibited a ti which decreased with increasing ρ, from ∼10 min for 0.15 Ω cm to ∼8 min for 20 Ω cm. We have utilized the difference in ti between n‐ and p‐type Si to produce selective area photoluminescence (PL) by Ga+ focused ion beam (FIB) implantation doping and B+ broad beam implantation doping of n‐type Si. Using 30 kV FIB Ga+ implantation, PL patterns with submicrometer resolution have been obtained for the first time.

Ion beam implanter for providing cross plane focusing

Abstract: An ion beam implantation system (10). An ion beam (14) is controllably deflected from an initial trajectory as it passes through spaced parallel plates (26, 28) that are biased by a control circuit (29). Once deflected, the ion beam passes through electrodes (32, 33, 34) positioned along a beam travel path that both redeflect the once-deflected ion beam and accelerate the ions to a desired final energy. Ions within the beam exit the accelerator and impact a workpiece at a uniform, controlled impact angel due to ion focusing in a scanning plane and an orthogonal cross plane.

Focused ion beam direct deposition of gold

Abstract: Focused ion beam direct deposition has been developed as a new technique for making patterned metal film directly on substrates. The 20 keV Au+ ion beam is focused, deflected, and finally decelerated to 30–200 eV between the objective lens and substrate. The decelerated beam is deposited on the substrate at room temperature. The beam diameter can be tuned between 0.5 and 8 μm and the beam current varies from 40 pA to 10 nA, corresponding to the beam diameter. Current density was about 20 mA/cm2, so that the deposition rate in the beam spot was estimated about 0.02 μm/s. The purity of gold film was measured with Auger electron spectroscopy and contents of carbon and oxygen, undesirable impurities, were below detection limits. The resistivity was constant at 3.7±0.1 μΩ cm for deposition over the ion energy range of 34–194 eV.

Secondary ion mass spectometry system

Abstract: A focused ion beam is directed toward a sample to be analyzed while iodine vapor is directed toward the sample. The iodine vapor, which is formed by heating solid iodine to a temperature of 30° C. to 50° C., aids in sputtering of material impinged by the ion beam and in enhancing the conversion of neutral to ionic sputtered species. A quadrupole mass analyzer is positioned for receiving secondary ions sputtered from the sample whereby chemical analysis is accomplished. The iodine may be initially handled in a solid state, exhibiting a low vapor pressure, and is then heated to moderate temperatures inside a focused ion beam system without presenting a toxic hazard or requiring external plumbing.

Method for manufacturing a surface acoustic wave device

Abstract: A surface acoustic wave device which can operate at a higher frequency range is produced by irradiation with a focused ion beam to produce a narrower electrode width and narrower spacing width between neighboring electrodes in contact with a piezoelectric body, without degrading the reliability of the device. The surface acoustic wave device includes a piezoelectric body 3 and interdigital electrodes 2a and 2b in close contact with the piezoelectric body 3 and formed by using the focused ion beam. In order to increase the frequency of the device, the piezoelectric body 3 may be formed on a substrate 1, for example of diamond.

Digital scan model for focused ion beam induced gas etching

Abstract: Focused ion beam (FIB), assisted, gas etching has several advantages over physical sputtering in many FIB applications. Advantages include etch rate enhancements of 1–2 orders of magnitude, dramatically reduced redeposition of etched material on sidewalls in high‐aspect ratio structures, and reduced implantation of the primary ion species in the sample. Applications which benefit from FIB gas etching include photomask and x‐ray mask defect repair, integrated circuit modification for failure analysis, and sample preparation for scanning electron microscope and transmission electron microscope analysis. In this article, a simple model is presented which takes into account the ion beam and scanning parameters, gas flux, and basic material constants. Approximate formulas are given in terms of these parameters and compared to experimental results.

Fabrication of high Ic×Rn YBCO-Josephson-junctions on MgO- substrates using a focused-ion-beam system

Abstract: We report on the fabrication of YBCO-Josephson-junctions using a narrow-focused Ga-ion beam to damage the MgO-substrates prior to film deposition. On top of the micro-areas damaged by the ion-beam, the as-grown YBCO-film shows weak-link properties. The final junction was achieved using photolithography and Ar-milling to fabricate a 5 μm wide superconducting line over the damaged area. This method, using only standard techniques, leads to reproducible junctions with a high Ic×Rn product, which is important for some applications and indicates a good barrier quality.

Transmission electron microscopy specimen preparation technique using focused ion beam fabrication: Application to GaAs metal–semiconductor field effect transistors

Abstract: A specimen preparation technique using a focused ion beam to generate cross‐sectional transmission electron microscopy (TEM) samples of GaAs integrated circuits (ICs) was studied. Using a two axes tilting technique it was possible to prepare sample with minimal thickness (∼10 nm) to enhance spatial resolution in TEM and x‐ray spectrometer analysis. This method was applied for failure analysis of degraded GaAs ICs. The interfacial microstructure between the gate metallization and the GaAs substrate, caused by high temperature operation, was also investigated

Multiple‐species ion beams from titanium‐hafnium alloy cathodes in vacuum arc plasmas

Abstract: We have studied the ion spectra of the plasma produced by the metal vapor vacuum arc for the case when the cathode material is a solid solution TiHf alloy of variable composition ratio A vacuum arc ion source was used to generate an intense beam of metal ions and a time‐of‐flight ion charge‐to‐mass diagnostic was used to measure the beam ion species and charge state distributions A range of different cathode compositions was examined, from pure Ti to pure Hf and with five different alloy mixes between these extremes We find that the ratio of ion currents in the multiple‐species ion beam corresponds approximately to the ratio of elements in the cathode, and that the mean charge states of the elemental ion components remain approximately constant as the cathode composition ratio is changed Multispecies metal ion beams can readily be generated in this way and the ion species characteristics of the beam are predictable

Method for correcting a patterned film using an ion beam

Abstract: Patterned film portions are removed from a surface of a flat substrate by irradiation with a focused ion beam without created undesired scars or processing grooves in the substrate surface. This is achieved by applying a masking substance only onto the substrate surface where it is not covered by the patterned film portions, and then using the focused ion beam to etch away the patterned film portions.

Metal ion implantation for large scale surface modification

Abstract: Intense energetic beams of metal ions can be produced by using a metal vapor vacuum arc as the plasma discharge from which the ion beam is formed. We have developed a number of ion sources of this kind and have built a metal ion implantation facility which can produce repetitively pulsed ion beams with mean energy up to several hundred kilo electron volts, pulsed beam current of more than an ampere, and time averaged current of several tens of milliamperes delivered onto a downstream target. We have also done some preliminary work on scaling up this technology to very large size. For example a 50‐cm diam (2000 cm2) set of beam formation electrodes was used to produce a pulsed titanium beam with ion current over 7 A at a mean ion energy of 100 keV. Separately, a dc embodiment has been used to produce a dc titanium ion beam with current over 600 mA, power supply limited in this work, and up to 6 A of dc plasma ion current was maintained for over an hour. We present here a review and summary of this metal io...

Direct writing of gold nanostructures using a gold-cluster compound and a focused ion beam

Abstract: Spin‐coated solid films of the gold‐cluster compound Dodeca‐(triphenylphosphine), hexa(chloro)pentapentacontagold Au55(PPh3)12Cl6 are irradiated with a focused 20‐keV Ga+ focused‐ion beam. The writing speeds on the substrate were ranging from 50 up to 2000 μm/s. This treatment locally decreases the solubility of the metalorganic precursor layer in CH2Cl2. Removal of the nonirradiated part of the surface layer with this solvent, followed by thermal decomposition of the remaining metalorganic nanostructures, leads to conducting gold lines. The width (150–360 nm) and height (20–80 nm) of these metallic lines depend on the ion dose and the original film height of the gold compound. The possible interactions leading to the fixation are briefly discussed.

Maskless writing of submicrometer gratings in fused silica by focused ion beam implantation and differential wet etching

Abstract: Surface relief gratings with submicrometer periods have been fabricated in silica by ion implantation with a focused ion beam, followed by etching in diluted hydrofluoric acid. Implanted silica etches three times faster than unimplanted silica and groove depths of the order of 300 nm have been achieved. The method does not require photolithography or masking layers, allows arbitrary patterns to be defined, and may be used to fabricate diffractive optical elements or grating filters in optical waveguides.

Fused silica masks for printing uniform and phase adjusted gratings for distributed feedback lasers

Abstract: A method for producing durable fused silica self‐interference grating photomasks is described. These masks allow repeated printing of both uniform and phase adjusted gratings. Periods as fine as 200 nm have been demonstrated. The fabrication of these masks via holographic and focused ion beam lithography and their use as a lithography tool are explained. Distributed feedback lasers, with gratings made by this technique, were produced. These lasers operated in a single longitudinal mode at a wavelength of either 1.55 or 1.3 μm.

Microscopic studies of semiconductor lasers utilizing a combination of transmission electron microscopy, electroluminescence imaging, and focused ion beam sputtering

Abstract: The microstructure of semiconductor laser diodes is studied using a combination of focused ion beam sputtering, electroluminescence imaging, and cross‐sectional transmission electron microscopy. Careful control of focused ion beam sputtering allows fabrication of high quality thin membranes for transmission electron microscope imaging, which can be located to submicron accuracy at a given position on the laser active stripe. By correlation with electroluminescence imaging, the membrane may then be positioned at an optically degraded region of the active stripe. In addition, imaging of the complete cross‐sectional laser structure, from substrate to surface contact layers is possible. The applications of these techniques to studies of laser degradation mechanisms are demonstrated and discussed.

Focused ion beam repair: staining of photomasks and reticles

Abstract: Focused ion beam (FIB) repair of chromium defects on photomasks and reticles leaves a post repair stain in the quartz substrate. The wavelength dependent absorption properties of typical stained regions have been measured, showing transition losses up to 80% in the deep UV. A simple model is in good qualitative agreement with the experimental results.