Shozo Inoue

This paper reports on two types of fabrication methods for Si nanowires (NWs) using focused ion beam (FIB), photolithography, TMAH anisotropic wet-etching, and sacrificial oxidation. Type A specimens made from silicon-on-nothing (SON) membranes are produced by FIB system's probe manipulation and film deposition functions. The mean Young's modulus of FIB-fabricated NWs evaluated by tensile testing in SEM using electrostatic actuated MEMS device is 129 GPa. After vacuum annealing, the Young's modulus is increased to 168 GPa. Type B specimens are produced by wire-thinning technique using sacrificial oxidation and oxide film removal. We succeeded in making freestanding bridge Si NW with the width of 76 nm.

Focused ion beam (FIB) is one of strong nanofabrication tools for Si and its related devices. In this study, To produce ultra-fine Si nanowires less than 50nm, we propose a new nanostructure fabrication technique using FIB and anisotropic etching. Si nanowires of several tens of nm could be formed, and it was found that the nanowires consisted of Ga ion doped amorphous Si. Uniaxial tensile test of the nanowires was performed to directly measure the Young's modulus and fracture strength.

The piezoresistive effect in silicon nanowires has attracted a great deal of interest for NEWS devices. Most of the piezoresistive SiNWs reported in the literature were fabricated using the bottom up method or top down processes such as electron beam lithography(EBL). Focused ion beam(FIB), on the other hand, is more compatible with CMOS integration than the bottom up method, and is simpler and more capable of fabricating very narrow Si nanostructures compared to EBL and photolithography. Taking the advantages of FIB, this paper presents for the first time the piezoresistive effect of p-type SiNWs fabricated using FIB implantation and wet etching. The SiNWs were locally amorphized by Ga ion implantation, selective wet-etched, and thermally annealed at 700℃. A relatively large gauge factor of approximately 47 was found in the annealed SiNWs indicting the potential of using the piezoresistive effect in top-down fabricated SiNWs for developing NEMS sensors.

Sputtered multilayered films with sub-100nm thick bilayers made of titanium and silicon show self-propagating explosive reaction. The reaction has attractive characteristics, such as easy fabrication, easy activation, temperature rise up to 1000degC, self-propagation, rapid propagation, non-oxidation-reduction reaction (the films can react everywhere), and zero emissions. In this paper, we compare heat performance characteristics in sputtered Ti/SiO multilayer films with those in Ti/Si multilayer films. Both the films have reacted by applying electrical power. After the reaction, there is no difference in the product between the two films. Ti/SiO multilayer films have found not to react by mechanical shock.

Porous nanoparticles are very attractive as a carrier for next generation drug delivery. To reliably deliver the proper amount of a drug with to the diseased part, the size and porosity of the nanoparticles should be controlled precisely. The atomized heating method is one of the promising techniques for producing porous nanoparticles. To date, with the technique, porous nanoparticles made of various metal oxides, such as alumina, silica, and titania, have been made from these nano powders with the diameter of 10nm. The purpose of this study is to precisely control the particle shape and size, pore size, and porosity of porous silica nanoparticles fabricated using the atomized heating method. The produced silica nanoparticles are subjected to strength test in a scanning electron microscope.

In this paper, the influence of vacuum annealing on the mechanical properties of gold (Au) bonding wires is described. Au bonding wires with the diameter of 25μm are subjected to quasi-static uniaxial tensile tests at laboratory air. The bonding wire specimens are prepared by the attachment of a wire to a silicon (Si) frame fabricated by deep reactive ion etching (DRIE). The Young's modulus and 0.2% offset yield strangth are 113GPa and 310MPa on average. By annealing at 100〜300℃ for 10min in vacuum, the Young's modulus value gradually decreases with increasing annealing temperature, whereas the yield strangth value drastically drops in the annealed wires at over 200℃. The annealing effect is discussed in the light of a change in the number of recrystallized grains in the wires.

Focused ion beam (FIB) is well known as a powerful tool for directly forming micro/nano-scale 3D mechanical structures without photolithography. By using FIB with Ga+ ions, we are able to conduct local etching as well as Ga+ ion implantation. The combination of the ion doping and alkali wet etching to a single crystal silicon wafer enables us to fabricate a nanometer-thick Ga+ ion doped amorphous silicon membrane. The silicon nano-membrane will be utilizable as nano mechanical elements, such as nano force/pressure sensors and nano oscillators in nanoelectromechanical systems. If the nano-membrane can be reshaped to arbitral 3D shape, the utility value will increase. The purpose of this study is to develop silicon nano-membrane reshaping technique using Ga+ ion implantation with FIB. The membrane is made by the combination of Ga+ ion implantation and wet etching, and it is bent to arbitrary angles by controlling the beam irradiationcondition. The silicon origami technique allows us to manufacture a micron-sized airplane from a silicon nano-membrane.

In this paper, we evaluate the adhesive strength of Ag-Sn solder-jointed single-crystal silicon (SCS) micro specimens. The exothermic reaction in Al/Ni multilayer film is used as a heat source, which is able to generate heat enough to melt the solder film. To investigate the influence of solder thickness on the bonding strength of the SCS samples with solder joint, especially developed four-point bending tester is used. As a result, the bond strength is largest when solder thickness is 4μm.

Focused-ion-beam (FIB) is one of strong nanofabrication tools for silicon (Si) and its related devices. By FIB fabrication, the surface damages with Ga ion implantation are definitely induced, which will reduce the mechanical reliability of Si devices. Annealing in high vacuum at 700℃ is known to be effective for the modification of these damaged portions. To improve the reliability, investigating the influences of surface damage, and annealing on the mechanical properties is important. In this study, quasi-static tensile tests of Si nanowires (NWs) fabricated using FIB were carried out to examine the mechanical properties. Then the relationship between the damage and annealing was investigated through energy-dispersive X-ray diffraction (EDX) analysis and cross-sectional transmission electron microscopy (TEM) observation.

Sputtered Al/Ni multilayer films show self-propagating exothermic reaction, which can be provided by just applying very small energy into the films. The reaction performances are known to depend on the light-metal and transition-metals combination, the bilayer thickness, and the entire film thickness. For example, the film with 100-nm-bilayer thickness and 30-μm-entire-film thickness can provide the heat energy of 1300 J/g, which corresponds to approximately 500℃. The authors are developing room temperature solder bonding technique using the reactive films for MEMS hermetic packages. During the reaction, cracking occurs due to volume shrinkage. Cracks in the bonded portion definitely lead to fatal errors and problems in the light of the seal performance and mechanical reliability. In this presentation, cracking and deformation phenomena are evaluated by means of X-ray transmission observation and energy dispersive X-ray analysis. Long-term sealing performance is also reported.

Self-propagating exothermic reactive films are one of attractive functional materials in MEMS field. The reactive materials with nanometer-thick multilayers consisting of light metal and transition metal possess attractive features, such as instant heat generation, self-propagation of reaction, rapid cooling, reactive in every atmosphere, and no emissions. The authors have been proposing the use of the reactive materials as local heat source for soldering in hermetic packages for MEMS. However, it is often seen that the reaction propagation stops at the half-way. In this paper, the size limit of Al/Ni reactive films for self-propagating explosive reaction on a Si wafer and SiO_x is reported to investigate the cause of the reaction stop.

Cemented carbide is typically used as material for working tool because it has superior characteristics, such as very high Young's modulus, excellent rigidity, good chemical inertness, and good thermal stability. This research focuses on investigating the possibility of WC-Co cemented carbide as structural material in MEMS. WC-Co cemented carbide nanowires (NWs) are prepared using focused ion beam (FIB) fabrication technique. The NWs are tensioned using a MEMS tensile test device that we have developed. The Young's modulus and fracture strength are affected by sample size, WC-to-Co ratio, and the WC-Co interface angle to tensile direction.

In this work, we investigate the effect of thickness ratio of Ti/Si constituent layer, bilayer thickness and total thickness on the self-propagating reaction behavior. It is presented that the Ti-Si multilayer films of Ti:Si = 1:2 show intensive self-propagating reaction. The films can react instantly by just applying mechanical shock. The multilayer films with the bilayer thickness of 〜25 nm appear to need the least energy to ignite the self-propagating reaction regardless of the Ti/Si thickness ratio.

This paper describes the influences of specimen size, focused ion beam (FIB) induced damage, and high vacuum annealing on the mechanical properties of silicon (Si) nanowires (NWs) evaluated by tensile testing in a FE-SEM. Si NWs made from silicon-on-nothing (SON) membranes are produced by deep reactive ion etching (DRIE) and annealing. FIB system's probe manipulation and film deposition functions are used to directly bond them onto the sample stage of a tensile test device and to fabricate Si NWs. The mean Young's modulus and strength of FIB-damaged NWs are 129.1 GPa and 5.6 GPa, respectively. After annealing, the Young's modulus is increased to 168.4 GPa, whereas the strength is decreased due to morphology degradation.

Mechanical properties of hard coatings are usually characterized by nano-indentation, scratch-test and ball-on-disk friction-test. However, the durability of the hard coatings under practical usage sometimes does not coincide the results of these tests. Development of a new method which can evaluate their durability under practical usage is expected. We proposed a new friction test for evaluating the durability of hard coatings in the last spring meeting, which utilized the friction welding apparatus. One of the problems of this method was that the load is too high for our purpose. In this work, we have used a new apparatus which can lighten the friction load, and evaluated the durability of a DLC film.

Multilayered films with sub-100nm thick bilayers made of light metal and transition metal shows self-propagating explosive reaction, which is attractive as local heat source. By using the films, the authors have so far succeeded in flash solder bonding of Si wafers for hermetic package. However, multilayered films restrict applications because finely forming the films to free dimensions is difficult. To explore other applications, fabricating micro-sized particles having exothermic reaction function is required. In this paper, a new technique for fabricating exothermic reactive micro-scale particles is described. A dual-source magnetron sputtering apparatus was used for particle fabrication. The heat generation performance of the particles was compared to that of the films using differential scanning calorimeter (DSC) and high speed charge coupled device (CCD) camera.

Self-propagating exothermic reactive films are one of attractive functional materials in MEMS field. The reactive materials with nanometer-thick multilayers consisting of light metal and transition metal possess attractive features, such as instant heat generation, self-propagation of reaction, rapid cooling, reactive in every atmosphere, and no emissions. The authors propose the use of the reactive materials as local heat source for soldering in hermetic packages for MEMS. However, it is often seen that the propagation of the reaction stops at the half-way. In this paper, the size limit of Al/Ni reactive films for self-propagating explosive reaction on a Si wafer is reported first, to investigate the cause of the reaction stop. Then the influence of bonded area size on cracking in reactive soldering is presented.

In this paper, we focus on evaluating the adhesive strength of Ag-Sn solder-jointed single-crystal silicon (SCS) micro specimens. Exothermic reaction in Al/Ni multilayer film was used as a heat source for melting the solder film. The reaction could generate heat enough to melt Ag-Sn film within 1 sec. To measure the mechanical properties of as-deposited and reacted Al/Ni films and the adhesive strength of solder-jointed SCS specimens, uniaxial tensile test equipment and four-point bending test equipment developed by the authors were used. For the bending test, the rectangular-solid SCS specimens having Ag-Sn/AINi/Ag-Sn multilayered section were prepared by dicing the bonded SCS wafer. The strength was increased with an increase in pressure load and Al/Ni multilayer film thickness.

This paper describes the effects of specimen size, focused ion beam (FIB) damage, and ultra-high vacuum (UHV) annealing on the mechanical properties of sub-100nm-size silicon (Si) nanowires (NWs) evaluated by tensile testing. Si NWs were made from silicon-on-nothing (SON) membranes that were produced by deep reactive ion etching (DRIE) fabrication and UHV annealing. FIB system's probe manipulation and film deposition functions were used to directly bond them onto the sample stage of a tensile test device and to fabricate Si NWs. The mean Young's modulus and strength of FIB-damaged NWs were found to be 129.1GPa and 5.6GPa, respectively. After 1000℃/700℃ annealing in UHV, the Young's modulus was increased to 168.4GPa, whereas the strength was decreased due to morphology degradation.

In this article, a new low-temperature solder bonding technique using Al/Ni exothermic reactive film is described. Al/Ni reactive film is able to generate heat enough to melt solder film. During the reaction, the volume is definitely shrunk by 12% because of changes in crystallographic structure and lattice constant. The volume shrinkage yields cracking in reacted NiAl. In this study we focus on the control of crack position and its propagation direction for realizing crack-less solder bonding using Al/Ni exothermic film. A multiple ignitions system to simultaneously start the reaction from several points was developed. It was demonstrated that major cracks were produced at the portion where two reactions ran into each other. By changing reaction start point, Al/Ni film's thickness and the overlap width, crack-less solder bonding in 20mm-square silicon chips was achieved.

In this article, the influences of specimen size and deformation-mode on the fracture strength of single-crystal silicon (SCS) micro-beam structures are described. We have designed and developed a new materials test device that is able to apply pure torsion, uniaxial-tension, bending, torsion-bending-combined, and torsion-tension-combined deformations to a micro-scale beam specimen. The specimen made of SCS consists of a SCS plate supported by two SCS micro-beams, and a frame, and was fabricated by deep reactive ion etching (DRIE) with the same fabrication recipe. All the SCS specimens tested in those deformation-modes were fractured in a brittle manner at a laboratory temperature. The fractured strength was calculated assuming that all the specimens had an ideal flat surface, and the data were arranged using two-parameter Weibull distribution function. Both the specimen size and deformation-mode dependencies were apparently found. To estimate the "true" strength, finite element analyses (FEAs) using the models that included scalloping sidewalls were carried out. The revised strength data that were estimated by multiplying stress concentration factors into the original data suggested that no deformation-mode dependency on strength existed.

Non-contact stress evaluation is required for nano-scale devices related to LSI and MEMS to improve their characteristics and reliability. Raman spectroscopy is known to measure surface stress of silicon without contacts and damages, but it cannot be applied to silicon-oxide(Si0_x) film that is commonly used as a passivation layer in silicon MEMS. We have proposed the stress measurement method for SiO_x, films using cathodoluminescence (CL) spectroscopy. However the CL stress measurement has a potential damaging the SiO_x, because electron beam (EB) irradiation is used for excitation of a specimen. To investigate the damage, we conducted Raman spectroscopic analysis and transmission electron microscope (TEM) observation. From Raman spectroscopic analysis, it found that stress distribution was changed at around EB irradiation spots. This change was probably caused by a structural change in SiO_x film or some damage at SiO_x/Si interface by the irradiation. And the TEM observation identified that EB irradiation produced silicon nanocrystals in SiO_x film. To measure the stress in SiO_x film using CL spectroscopy without any damages, EB irradiation condition without silicon nanocrystals generation must be specified

In this article, a new low-temperature solder bonding technique using Al/Ni exothermic reactive film is described. Al/Ni reactive film is able to generate heat enough to melt solder film. During the reaction, the volume is definitely shrunk by 12% because of changes in crystallographic structure and lattice constant. The volume shrinkage yields cracking in reacted NiAl. In this study we focus on the control of crack position and its propagation direction for realizing crack-less solder bonding using Al/Ni exothermic film. A multiple ignitions system to simultaneously start the reaction from several points was developed. It was demonstrated that major cracks were produced at the portion where two reactions ran into each other. By changing reaction start point, Al/Ni film's thickness and the overlap width, crack-less solder bonding in 20mm-square silicon chips was achieved.

In this article, the development of mechanical characteristics evaluation technique for FIB-processed nanostructures is described. We designed the on-chip tensile testing device, which consists of a nano-specimen, electrostatic actuator for stretching the specimen, and capacitance sensor for measuring tensile displacement. A theoretical resolution of 1 nm in tensile displacement was achieved. The uniaxial tensile force was derived using the spring constant of suspended beams with theoretical resolution of 15 nN. In addition, we developed a new nano-testing technique that is the combination of on-chip tensile testing device and nano-sampling technique using FIB. By using the technique, the Young's modulus of Si nanowire was measured to be 168.8 GPa, which is close to the ideal value of SCS (001)[110]. The tensile strength was 8.3 GPa, indicating that there is a size effect on the strength.

We have developed biaxial tensile tester for thin film materials, which is able to measure mechanical properties under uniaxial and biaxial tensile stress states. This paper focuses on evaluating the effect of annealing on mechanical characteristics of Al-Si-Cu film deposited by sputtering. The yield stress under biaxial stress state definitely differed from that under uniaxial state. The obtained yield loci were well approximated by Hill's yield function with different R values. The annealing effect on yield stress was discussed using Auger spectroscopy results.

This paper describes evaluation of bond strength in MEMS soldering package heated by using Al/Ni multilayer film. Al/Ni multilayer film deposited by DC magnetron sputtering shows self-propagating exothermic reaction. By applying a spark to the reactive film, the film generates heat enough to melt eutectic solder film. The heat of reaction depended on Al/Ni bilayer thickness and the total film thickness. We used the Al/Ni multilayer film as a local heat source in MEMS soldering packages. The solder film-bonded silicon elements by the local heating was fabricated without other external heat sources. The bond strength examined by blister test for package was evaluated by weibull distribution.

We have deposited stainless steel films onto glass slides under various ion bombardment conditions by de unbalanced magnetron sputtering. The apparatus was equipped with an external coil around the magnetron cathode which allows us to alter the ion flux to the substrate. A commercial SUS304 steel disk (phi 50 mm x 2 mm) was used as a target. The sputtering gas was Ar (99.999%) and its pressure ranged from 0.2 to 1.0 Pa. The applied de power and external coil current were also varied in the range P-dc = 100 similar to 220 W and I-c = -3 similar to4 A, respectively. The crystal structure, composition, internal stress, corrosion resistance and hardness of deposited films were examined. The deposited films showed bcc structure with strong (110) preferred orientation. The film surface looks like martensite with very fine grain. The Cr composition in deposited films appeared to decrease about 2 mass% compared to target material. The ion bombardment showed very small effect on the structure and the composition of deposited films. The corrosion resistance and the hardness of the films seemed to be much better than bulk material.

Ti-C films have been deposited onto slide glasses using a sputtering apparatus having dual planar magnetron cathodes. Applied de power for both Ti and graphite target was varied independently between 0-200 W for depositing Ti-C films with various C/Ti ratios. The substrates were not intentionally heated during deposition. The structure, composition and morphology of films were examined by XRD, AES and AFM. Carbon composition in the deposited Ti-C films increased with the power ratio of C/Ti as expected. However, the carbon concentration tends to be higher than designed from both deposition rates. This phenomenon is remarkable at lower C/Ti power ratio. The sticking coefficient of carbon atoms seemed to increase when Ti is cosputtered. The interplanar spacing of (0 0 2) Ti changed from 0.235 nm to 0.245 nm when C/Ti power ratio increased up to 0.2. It was found that crystalline TIC films are grown when C/Ti power ratio is between 0.4 and 4. The films deposited at 2 of C/Ti power ratio showed near-stoichiometric composition. (C) 2000 Elsevier Science Ltd. All rights reserved.

The influence of nitrogen partial pressure (P(N2)) and argon partial pressure (P(Ar)) on internal stress, crystallographic structure, and resistivity have been investigated for reactively sputtered Ti-N films in order to get some insight into the influence of deposition parameters. Ti-N films were deposited onto glass substrates by r.f. reactive magnetron sputtering using a plasma emission monitoring control system. The r.f. power applied was kept constant at 300 W during deposition, and the substrate temperature was room temperature. When P(Ar) is 0.4 Pa and P(N2) is 1 x 10(-3) Pa or higher, films deposited become single phase of TiN, although preferential orientations of films change with P(N2) Ti-N films deposited at a P(N2) Of 2-6 x 10(-3) Pa become a gold color, and the resistivity becomes minimum. The internal stress of deposited Ti-N films changes as a function of both argon and nitrogen partial pressure, and films deposited at a low P(Ar) tend to have high compressive stress. The internal stress is also related to preferred orientation of films. Films having the (001) preferential orientation show higher compressive stress than those having the (111) preferred orientation. (C) 1999 Elsevier Science S.A. All rights reserved.

The process of rf reactive magnetron sputtering is suitable for depositing TiN films, because of its applicability for large-area processing. This process, however, shows the so-called hysteresis when the reactive gas is controlled by constant flow rate, which leads to a relatively poor reproducibility. In this paper, it is shown that the closed-loop nitrogen flow control by plasma emission monitoring (PEM) provides a stable reactive sputtering under a wide range of nitrogen partial pressure. The influence of the nitrogen partial pressure on the Ti-N film composition, crystallographic structure and resistivity was also investigated. The Ti-N films deposited at the nitrogen partial pressure of 2 similar to 5 x 10(-3) Pa revealed the minimum resistivity and appeared to be stoichiometric TiN. The PEM control system makes it possible to stably control this range of nitrogen partial pressure. This system also provides high rate film processing.