Shinji Nagamachi

Focused ion beam direct deposition of gold

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.

Focused ion‐beam direct deposition of metal thin film

Focused ion‐beam direct deposition has been developed as a new method for fabricating patterned metal films directly on substrates. The principle of this method is to perform ion‐beam deposition by low‐energy focused ion beams. We designed and constructed a low‐energy focused ion‐beam apparatus for direct deposition. Metal ions are extracted from liquid metal ion source, accelerated to 20 keV for single charged ions, focused, mass separated, deflected, and finally, decelerated to 30–1000 eV in this system. The beam diameter estimated by the deposited linewidth 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 for the Au+ ion in the energy range from 30 to 200 eV. The sticking probabilities of ion‐beam deposition were measured and the critical energies for Au+, Cu+, Al+, and Nb2+ were about 210, 230, 800, and 1300 eV, respectively. The purity of gold film was measured by Auger electron spectroscopy and secondary‐ion‐mass spectroscopy. The c...

Focused ion beam direct deposition and its applications

We developed focused ion beam direct deposition as a new method for fabricating patterned metal films directly on substrates. We designed and constructed a focused ion beam apparatus which satisfied demanded capabilities for direct deposition such as low energy and fine focused beam, high beam current density, high vacuum condition, changeability of ion species, precise and wide range patterning, sample observation by an optical microscope, and quick sample exchange. We also developed liquid alloy–metal ion sources for conductive materials, superconductive material and magnetic material. We tried to apply the focused ion beam direct deposition method to IC modification, surface acoustic wave (SAW) devices, SQUIDs, multilayers, and probing on small crystals. In SAW devices, SQUIDs, and multilayers, fabricated devices had comparable performance to devices fabricated by ordinary photolithographic processes. In IC modification and probing on small crystals, a low resistant and flexible connection was confirme...

Focused ion beam direct deposition of superconductive thin film

Focused ion beam direct deposition of niobium has been developed as a technique for fabricating superconductive thin films. A Nb2+ ion beam extracted from a Nb10–Au50–Cu40 liquid metal ion source was accelerated to 40 keV, focused, deflected and finally decelerated to 50–1000 eV. The beam current density was 0.4–2 mA/cm2 and the minimum deposited linewidth was about 0.5 μm. The sticking probability of the Nb2+ ion beam and the critical temperature of deposited niobium films were measured. The deposition at different deposition rates and different residual gas pressure were performed. A clear relation was obtained between the critical temperature and the concentration of contaminations. This relation is consistent with the published relation for bulk niobium if it is assumed that the sticking probability of residual gas is 0.2. However, dependence of the critical temperature on ion energy was not observed.

GIANT MAGNETORESISTANCE IN CO/CU MULTILAYERS FABRICATED BY FOCUSED ION-BEAM DIRECT DEPOSITION

We report the direct deposition of patterned multilayers that exhibit giant magnetoresistance without any lithographic processes. We fabricated Co/Cu multilayers by the focused ion‐beam direct deposition method and measured the magnetoresistance characteristics of the multilayers. The fabricated Co/Cu multilayers are 14×76 μm2 in size and consist of 12 layers of Co thin film with the thickness of 20 A and 11 layers of Cu thin film with the thickness of 13–22 A on the GaAs substrate. We used a 108 eV Co2+ ion beam and 54 eV Cu+ ion beam extracted from a Co–Cu–Au–Nb alloy ion source. The measured magnetoresistance ratio of giant magnetoresistance was 6.7% in the case of the Co(20 A)/Cu(21 A) multilayer. Experimental results show precise controllability of the thickness and the additional capability of the focused ion‐beam direct deposition method.

An RFQ accelerator system for MeV ion implantation

Abstract A 4-vane-type Radio-Frequency Quadrupole (RFQ) accelerator system for MeV ion implantation has been constructed and ion beams of boron and nitrogen have been accelerated successfully up to an energy of 1.01 and 1.22 MeV, respectively. The acceleration of phosphorus is now ongoing. The design was performed with two computer codes called SUPERFISH and PARMTEQ. The energy of the accelerated ions was measured by Rutherford backscattering spectroscopy. The obtained values agreed well with the designed ones. Thus we have confirmed the validity of our design and have found the possibility that the present RFQ will break through the production-use difficulty of MeV ion implantation.

Low-energy focused ion-beam system for direct deposition

Low energy focused ion beam direct deposition has been developed as a new method for fabricating patterned metal films directly on substrate. The principle of this technique is to perform ion beam deposition by using a very low energy focused ion beam. A low energy focused ion beam system for direct deposition has been designed and constructed. In this system the desired material is ionized, separated from undesired ion species, focused, deflected, and decelerated to the optimum deposition energy. The main components of the system are a liquid metal ion source, a mass filter, two Einzel lenses, double octapole deflectors, and an electrically floating sample stage. The beam energy can be continuously varied from 0 eV to 20 keV for single charged ions. The beam diameter can be tuned between 0.5 and 8 micrometers and the beam current varies from 40 pA to 10 nA corresponding to the beam diameter for Au+ ion in the energy range from 30 eV to 200 eV. The purity of deposited gold film was measured by Auger electron spectroscopy and concentrations of carbon and oxygen were below detection limits. The resistivity of gold film was 3.7 +/- 0.1 (mu) (Omega) cm. Currently, new applications of this deposition method are being developed.

Application of the focused ion beam technique to the direct fabrication of vertical‐type field emitters

The focused ion beam (FIB) technique has been applied to the direct fabrication of vertical‐type field emitters for vacuum microelectronics. A gate and emitter can be formed directly by etching metal/insulator/semiconductor (MIS) structure with an FIB. A rotationally deflected FIB erodes the metal surface to produce a ring‐shaped groove, and finally produces a small protrusion made of semiconductor (field emitter). The present process is simple, self‐aligned, and a direct process which does not require the electrode material to have a specified chemical property. In the present study, sputter etched structures have been evaluated with a dynamical simulation, and compared with those fabricated under the similar condition. The calculated structure agreed with the fabricated structure, which means the present simulation gives a reasonable estimation of the FIB fabricated structures. Also, attempts have been made to optimize fabrication conditions and emitter materials.

Optical properties of a low energy focused ion beam apparatus for direct deposition

We designed and constructed a low energy focused ion beam apparatus for direct deposition. The optical properties of our lens system were calculated to obtain its optimum shape and arrangement for a low energy (50–100 eV) and fine focused (<1 μm) ion beams. We evaluated magnification, chromatic aberration, and spherical aberration. Using the apparatus based on our design, we deposited a focused ion beam and deduced the beam diameter from linewidth measurement of the deposited film. The diameter of 50–200 eV Au+ beams could be tuned between 0.4–7 μm corresponding to beam currents of 40 pA–10 nA. The current density was constant at about 30 mA/ cm2. At lower currents, the minimum beam diameter was limited to 0.35 μm. These experimental results agree with calculated results qualitatively, but quantitative differences exist. Assumptions, based on Ga+ ion sources, seem to cause the differences. If we adopt our measured energy dispersion (30 eV) and angular current density (10 μA/sr) and assume the virtual sour...