井上 尚三

In this article, the design and development of a biaxial tensile test device and its specimen are described. The device, which was designed for evaluating the mechanical characteristics of a thin film specimen under in-plane uniaxial and biaxial tensile stress states, consists of four sets of a piezoelectric actuator, a load cell, a linear variable differential transformer (LVDT), and an actuator case including lever structures with displacement amplification function. The structures fabricated by wire electrical discharge machining are able to amplify the actuator's displacement by a factor of 3.8 along the tensile direction. The biaxial test specimen prepared using conventional micromachining processes is composed of a cross-shaped film section and chucking parts supported by silicon springs. After square holes in four chuck parts are respectively hooked with four loading poles, the film section is tensioned to the directions where the poles get away from the center of the specimen. Tensile strain rate can be individually controlled for each tensile direction. Raman spectroscopic stress analyses demonstrated that the developed biaxial tensile test device was able to accurately apply not only uniaxial but also biaxial tensile stress to a single-crystal silicon (SCS) film specimen. [DOI: 10.1115/1.4005348]

In this article, a new technique for controlling crack position and its propagation direction in solder-bonding using Al/Ni exothermic reaction is described. Sputtered Al/Ni multilayer film is able to produce heat instantly by its self-propagating exothermic reaction, and the reactive film can be used as heat source for solder-bonding. During the reaction, however, volume reduction by approximately 12% occurs due to crystal structural change from fcc to bcc and lattice-spacing reduction. Consequently, cracks are produced in the reacted NiAl structure. The cracks negatively affect the strength of the bonded system. We have found a new technique for controlling crack position and its propagation direction. Multiple ignitions for reaction demonstrated that cracks in reacted NiAl film can be controlled. When applying the flash heating technique to wafer-level bonding, cracks are probably produced. If cracks can be fabricated on dicing cut lines by using the simultaneous multiple reactions technique, crack-less solder-bonded Si hermetic packages would be realized.

本研究では，MEMS用構造材料として応用が期待できるZr65Cu17.5Ni10Al7.5を高周波マグネトロンスパッタリング装置で薄膜化し，作製条件が薄膜の内部応力や組成に及ぼす影響を調査した．その結果，薄膜の組成はターゲットから幾分ずれており，作製時のAr圧によって数%程度変化することが分かった．また，ZrCuNiAl金属ガラス薄膜の内部応力は，結晶の金属薄膜と同様にAr圧の増加に伴って圧縮から引張りに遷移することが明らかとなった．

本研究では，スパッタ法により種々の条件で作製したTi-Al多層膜の自己伝播発熱反応を評価することを目的とした．今回作製したどの試料も，室温下では電気的スパークによる外部エネルギーのみでは自己発熱伝播反応を示さず，反応を誘起するためには予熱が必要であった．組成比Ti:Al＝1:3，Bilayer厚50nm，総膜厚10μmとして作製したTi-Al多層膜が最も低い予熱温度で自己伝播発熱反応を示すことがわかった．

In this article, mechanical reliability of solder joints fabricated using Al/Ni reactive film is described. Rectangular solid Si sample with solder-bonded section was prepared for measuring the bond strength using developed four-point bending test equipment. By changing Al/Ni film thickness, interlayer between SnAg solder and Si, and pressure load during bonding, the fracture strength was investigated. In case that 10nm-thick Au/Ni was used as the interlayer, fracture occurred at the interface between the interlayer and Si. On the other hand the specimen with Au/Ni/Cr interlayer fractured at the interface between melted and non-melted SnAg solder. The strength in thick-Al/Ni specimen was higher than that in thin-Al/Ni specimen. It was found that sufficiently melting the solder during Al/Ni flash heating is important for high strength solder joint. © 2012 IEEE.

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 SnAg solder film. During the reaction, the volume is definitely shrunk by 12% because of the 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 parts 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. © 2012 IEEE.

In this article, a technique for non-destructive stress analysis of thermal silicon-oxide (SiOx) film using cathodoluminescence (CL) spectroscopy is described. The uniaxial tensile tester which can be used in a scanning electron microscope (SEM) chamber was developed to apply tensile stress to the film specimen. CL spectra of SiOx film were measured under various tensile stresses. The peak position linearly increased at 7.53x10(-3)eV/GPa with an increase in tensile stress. The peak intensity and half bandwidth changed with an increase in electron beam (EB) irradiation time period. Using Raman spectroscope and transmission electron microscope (TEM), it was found that EB irradiation produced silicon nanocrystals in SiOx film. The nanocrystals as well as applied stress affected CL spectra.

In this paper, in-situ cathodoluminescence (CL) stress analysis of a silicon oxide (SiO(x)) thin film prepared by wet thermal oxidation is described. The specially-developed uniaxial tensile loading jig was used to apply tensile displacement to the SiO(x) film specimen. CL spectra of the specimen during tensile loading were obtained, and the peak position of around 1.85 eV emission band was monitored for tensile stress analysis. The peak position gradually shifted towards higher/lower energy side when tensile displacement increased/decreased. The tensile stress-to-emission energy ratio of 6.21 similar to 8.97 x 10(2) GPa/eV was estimated on the basis of linear elastic theory, which demonstrated that CL is able to provide information on stress induced in the film. Scanning electron microscopy (SEM) revealed that the fracture of SiO(x) and SCS laminated structure occurred at the vicinity of SiO(x) film surface.

This paper describes the development of a bimorph-actuated twin-probe device utilized for uniaxial tensile test to measure tensile elongation of a film specimen. The device consists of two sets of microscale cantilever probes with piezoresistive sensor to detect the position of two gauge marks on a specimen, and multiple pairs of bimorph actuators to produce in-plane motion for scanning those marks. By Joule's heating, the bimorph actuators connecting two cantilever probes are able to move along the tensile direction. When those probes climb the gauge marks having convex line structure, the sensor signals originating from the piezoresistive effect are output by the cantilever's deflection. The elongation of a tensile specimen can be calculated from the moving velocity of cantilever probes and the time difference between two sensor signals. The performance of the device produced through conventional micromachining technologies was investigated. Elongation of single-crystal silicon (SOS) film specimen was measured during uniaxial tensile loading. The mean Young's modulus of 165.1 GPa which was measured by using the device was in good agreement with the analytical value. The proposed bimorph-actuated twin-probe device would be useful for measuring elongation of a film specimen during the tensile test.

In this paper, a new technique for fabricating silicon carbide (Si-C) microelectromechanical systems (MEMS) is described. Slip casting to UV-thick photoresist (SU8) micro mold was carried out for the fabrication of three-dimensional Si-C MEMS parts. Ultrahigh molecular weight polycarbosilane (PCS) was used as the precursor. Si-C nano powder was firstly mixed with a PCS solution, and then the slips were cast into SU8 micro mold fabricated on porous tungsten carbide (WC) plate. Firing at 1273 K was conducted for SU8 evaporation and PCS pyrolysis simultaneously. We have succeeded in producing Si-C ceramics micro gears using the "mu slip casting" technique.

近年，動力やエネルギーを発生させるPower MEMSの開発が進められている．その構造材料には，優れた機械特性と耐熱性が求められるが，MEMSの基礎材料である単結晶Siは耐熱性が乏しく，不適合である。また，CVD等で作られたSiC膜を微細加工するのは困難である．本研究では，超高分子量ポリカルボシランを前駆体とし，泥しょう鋳込み成型法を応用したSiC-MEMSパーツの製作技術を開発する．今回は，その最適化を目的として発表する．

現在， MEMSミラーの低コスト化及び大偏向角化が求められている。著者らは、デバイスのトーションバーにフォトレジスト(SU-8)を用いたMEMSミラーを開発している。その信頼性向上には、SU-8の機械特性を徹底評価し、設計に反映させなければならない。本研究では、引張試験，応力緩和試験及び接着強度試験で、SU8の機械特性を系統的に評価した結果を報告する。

Zr基バルク金属ガラスはこれまでマイクロ材料としては注目されてこなかったが、MEMS用構造材料としても期待できる特性を持つ。本研究ではZr-Ni-Al合金を取り上げ、コンビナトリアル法を用いた組成探索を試みた。３源スパッタ装置で作製した薄膜ライブラリを評価した結果、Zr:Ni:Al=40:30:30付近の組成を持つ薄膜は結晶化温度が550℃以上の安定した非晶質相であることが明らかとなった。

我々は、h-BNターゲットをRFスパッタしてc-BN相を含む薄膜の形成を試みている。今回は、基板バイアス電圧を主たるパラメータとし、基板温度、スパッタガス圧の影響についても併せて調査した。その結果、80V以上のバイアス電圧を印加することで、c-BN相を含む薄膜が得られることがわかった。また、その含有割合は、基板温度が高いほど、またスパッタガス圧が低いほど多くなる傾向が認められた。

In this article, a new technique for controlling crack position and its propagation direction in solder-bonding using Al/Ni exothermic reaction is described. Sputtered Al/Ni multilayer film is able to produce heat instantly by its self-propagating exothermic reaction, and the reactive film can be used as heat source for solder-bonding. During the reaction, however, volume reduction by approximately 12% occurs due to crystal structural change from fcc to bcc and lattice-spacing reduction. Consequently, cracks are produced in the reacted NiAl structure. The cracks negatively affect the strength of the bonded system. We have found a new technique for controlling crack position and its propagation direction. Multiple ignitions for reaction demonstrated that cracks in reacted NiAl film can be controlled. When applying the flash heating technique to wafer-level bonding, cracks are probably produced. If cracks can be fabricated on dicing cut lines by using the simultaneous multiple reactions technique, crack-less solder-bonded Si hermetic packages would be realized. © 2011 IEEE.

In this article, the influence of annealing on the mechanical characteristics of sputtered aluminum-silicon copper (Al-Si-Cu) thin films is described. The in-plane biaxial tensile tester developed by the authors was used for uniaxial and biaxial tensile tests in ambient air. In uniaxial test results, the Young's modulus did not depend on annealing, whereas the yield stress was influenced by annealing. However, both the characteristics were not dependent on strain rate. After biaxial tests with various strain rate ratios, yield stresses were determined by using finite element analysis result. The yield locus in non-annealed films was different from that in annealed films. The yield locus for non-annealed and annealed films could be respectively fitted by using Hill equation with different R values, which indicates that annealed films can deform easily to transversal direction. From Auger spectroscopic analyses, Al2Cu precipitation was made at grain boundary by annealing. The precipitation played a role as a bond between grains consequently, transversal strain in annealed films would have become larger. © 2011 IEEE.

In this study, we developed a novel strain measurement technique for electrochemically aligned collagen (ELAC) fibres using second harmonic generation ( SHG) microscopy. The ELAC fibres were prepared by a typical electrochemical method and were subjected to cross-linking. For comparison with natural collagen fibres, polarization dependency of the prepared ELAC fibres and that of a human Achilles' tendon were evaluated. The results showed that, because of cross-linking, the ELAC fibres exhibit polarization dependency similar to that of the tendon but only in a region close to the tendon. The relationship between SHG and the applied strain was determined by a combination of SHG microscopy and tensile tests. The SHG from the ELAC fibres changed in the high strain region because of the applied stress.

In this study we describe a novel system for measuring the distribution of inhomogeneous mechanical properties of microelectromechanical system (MEMS) devices. Such inhomogeneous properties are important because they can decrease the reliability of MEMS devices. Our technique involves measuring the variation in the relative position and angle between single molecule markers sprayed on a MEMS device, which indicates the amount of local deformation. The distribution of the deformation on the surface of a MEMS device is calculated from local displacements measured using the system. To simultaneously measure the three-dimensional (3D) position and orientation of the markers, we developed a 3D orientation measurement system that consists of an epifluorescence microscope and a polarization mode converter (PMC). We also detected the 3D displacement and orientation of the torsion bar in a MEMS mirror device.

We have investigated the effect of Cu content on the shape memory behavior of Ti-Ni-Cu ternary alloy films deposited by means of triple-source dc magnetron sputtering. The films annealed at 700 °C for 60 min showed thermoelastic martensite transformation accompanied with shape memory effect. Their martensite transformation behavior was found to depend on Cu composition. Films containing more than 15 at.% Cu showed very narrow transformation hysteresis (̃ 13 °C) and high critical stress against plastic deformation (̃ 400 MPa). These characteristics are preferable to be used as important elements of high performance micro-actuators. © 2010 Elsevier B.V.

We have deposited the Ti-Ni-X films having various compositions while keeping the Ti content to be similar to 50at% by means of triple-source dc magnetron sputtering. All of the annealed films showed thermoelastic martensitic transformation. M(s) temperature of the Ti-Ni-Pd films increased with increasing Pd content, and the highest M(s) temperature of similar to 180 degrees C was attained for the Ti-23%Ni-27%Pd film. On the other hand, M(s) temperature of Ti-Ni-Cu films slightly Increases as Cu content increases. The transformation hysteresis is decreased rapidly down to similar to 15-20 degrees C by adding Pd or Cu more than 10at% Both ternary alloy films showed shape memory behavior during thermal cycling tests under various constant stresses. The critical stress against plastic deformation, sigma(c), of the Ti-Ni-Cu films is higher than that of the Ti-Ni-Pd films. The recoverable strain of these ternary alloy films is found to be similar to 2%. Actuation response by Joule's heat induced shape memory effect of Ti-Ni shape memory alloy films was slightly improved by the addition of Pd or Cu into the alloy.

In this paper, we describe the elastic-inelastic mechanical property measurements of a gold-tin (Au-Sn) eutectic solder film. Dual-source direct-current (dc) magnetron sputtering was employed to deposit a Au-20 weight % (wt.%) Sri film. A uniaxial tensile test with in situ X-ray diffraction (XRD) analysis was performed at temperatures ranging from room temperature (RT) to 373 K. The XRD tensile test enabled us to directly measure out-of-plane strain in the Au-Sn film specimen for Poisson's ratio determination. The mean Young's modulus and Poisson's ratio at RT were found to be 51.3 GPa and 0.288, respectively, which were lower than the bulk values. The Young's modulus decreased with an Increase in temperature, whereas the Poisson's ratio showed no change with temperature. In addition, a creep test was carried out at various stresses and temperatures. The steady-state creep deformation behavior could be estimated on the basis of Norton's law. Information on the tensile and creep characteristics would be useful in designing Au-Sn-film-bonded microjoints used in micro-electromechanical systems (MEMS).

This paper describes evaluation of the strength in Ag-Sn-jointed Si specimens heated by Al/Ni film's exothermic reaction The reaction generates heat enough to melt Ag-Sn film for soldering. To measure the strength, four-point micro-bending test technique has been developed The rectangular-solid Si specimens having a Ag-Sn/AlNi/Ag-Sn section were prepared by dicing the bonded Si-wafer under various pressure loads. A higher pressure yielded a better contact condition between Al/Ni and Ag-Sn so that heat-conduction improved; consequently Ag-Sn was melted sufficiently. Al/Ni reactive film has a potential as a micro-heater in soldering for MEMS.

This paper focuses on evaluating the adhesive strength of Ag-Sn solder-jointed single-crystal silicon (SCS) micro specimens. The 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. To measure the adhesive strength of solder-jointed SCS specimens, we developed the four-point bending tester for minute specimens. The rectangular-solid SCS specimens having Ag-Sn/AlNi/Ag-Sn multilayered section were prepared by dicing the bonded SCS wafer. As a result, the fracture strength increased with an increase in pressure load and Al/Ni multilayer film thickness.

We developed a system to analyze microscopic deformation, which can visualize inhomogeneous deformation in MEMS(Micro Electro Mechanical Systems) devices by using single-molecule markers. As MEMS devices become smaller, their mechanical properties seem to become inhomogeneous. This causes an undesirable distribution of deformation and stress, and decreases the reliability of the MEMS devices. We distributed fluorescent single molecules discretely on the microstructure of a MEMS device, and traced their relative displacements and rotations by observation under a three-dimensional orientation microscope, which provided information about normal, torsional, and bending displacements.

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 Young's modulus did not depend on annealing, whereas the yield stress clearly showed annealing dependency. 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.

In this paper, we describe a new production method for microscale silicon carbide (SiC) ceramics parts. Slip casting with SU8 micro mold was carried out for the fabrication of a three-dimensional SiC MEMS component, which was made from polycarbosilane (PCS) precursor-derived SiC nano powder. SiC nano powder was mixed with a PCS solution. The slips were then cast into SU8 micro mold made on porous tungsten carbide (WC) plate. Firing at 1273 K was conducted for SU8 evaporation and PCS pyrolysis. We have succeeded in producing microscale SiC ceramics gears using the "mu slip casting" technique.

This paper describes evaluation of surface stress distribution in single-crystal silicon (SCS) microstructure using laser Raman spectroscope. An in-house uniaxial tensile tester was employed to apply the uniaxial tensile stresses to SCS (001)[100] and (001)[110] film specimens with a number of microscale convex structures. A linear relationship between the applied tensile stress and Raman peak shift increment was obtained from Raman spectroscopy at a flat section of the specimen. Raman spectroscopy was also conducted to observe nonuniform stress distribution around the convex structures under uniaxial tensile loading. In observations around a convex structure, "two-curve fitting" was adopted for the asymmetric spectrum, which had been observed clearly under the tensile stresses of over 1000 MPa. The two-curve fitting was able to separate information of the top corner from that of the bottom one at the edge. The stress distribution estimated by the two peak positions was much closer to finite element analysis (FEA) results than that obtained by the one peak position. (C) 2009 The Japan Society of Applied Physics

This paper describes the mechanical characterization of sputtered aluminum-alloy (Al-alloy) film used as a structural material in microelectromechanical systems (MEMS). The environment-controlled uniaxial tensile test system with elongation measurement image analysis function was developed to investigate the material characteristics at temperatures ranging from room temperature (RT) to 358 K. From the quasi-static tensile test results, no specimen size effect on Young's modulus and yield stress was found, whereas the annealing and temperature influences were clearly observed. To investigate mechanical degradation to cycling loading, the cyclic loading tests were conducted under constant stress- and strain-amplitude modes. In constant stress-amplitude mode, stain amplitude increased with an increase of loading cycles. Almost of the specimens fractured during the tests. Meanwhile, in constant strain-amplitude mode, stress amplitude gradually decreased with increasing cycles, but no fatigue failure was found. The cyclic loading and stress relaxation tests revealed that creep deformation was dominant in the degradation of Al-alloy film subjected to cyclic motion.

This paper focuses on evaluating the adhesive strength of Ag-Sn solder-jointed single-crystal silicon (SCS) micro specimens. The 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. To measure the adhesive strength of solder-jointed SCS specimens, we developed the four-point bending tester for minute specimens. The rectangular-solid SCS specimens having a Ag-Sn/AlNi/Ag-Sn multilayered section were prepared by dicing the bonded SCS wafer under various pressure loads in air and vacuum. As a result, fracture strength increased with an increase of pressure load. The strength of specimens bonded in vacuum was higher than that bonded in air.

This paper focuses on evaluating the adhesive strength of silver-tin (Ag-Sn) solder-jointed single-crystal silicon (SCS) specimens. The exothermic reaction in aluminum-nickel (Al/Ni) multilayer film was used as a heat source for melting the solder film. The reaction generated heat enough to melt Ag-Sn film [1]. To measure the adhesive strength of solder-jointed SCS specimens, we developed the four-point bending tester for minute specimens. The rectangular-solid SCS specimens having an Ag-Sn/AlNi/Ag-Sn section were prepared by dicing the bonded SCS wafer under various pressure loads in air and vacuum. As a result, fracture strength increased with an increase of pressure load. The strength of specimens bonded in vacuum was higher than that bonded in air. ©2009 IEEE.

This paper describes a quantitative measurement method for Young's modulus of nanometer-thick film materials by using a MEMS resonator array. The MEMS resonators fabricated by silicon micromachining techniques were designed to be driven at their resonant frequencies from 6.0 kHz to 35.5 kHz. From the difference in resonant frequencies between before and after deposition of these films onto the resonators, we successfully measured the Young's moduli of Al and plasma-polymerization films made from CH4 and CHF3 gases. The obtained Young's moduli of Al, CH4 and CHF3-derived polymer films were found to be 60.4, 35.7, and 30.0 GPa on average, respectively, and showed no film thickness dependency in the range from 50 to 150 nm. The obtained values for all the films by the resonance tests were comparable to those by tensile and nanoindentation tests. The proposed technique is effective for directly measuring Young's modulus of nanometer-thick film materials. ©2009 IEEE.

This paper describes the mechanical degradation mechanism of sputtered aluminum-alloy (Al-alloy) film used as a structural material in microelectromechanical systems (MEMS). The environment-controlled uniaxial tensile test system with elongation measurement image analysis function was developed to investigate the material characteristics at temperatures ranging from room temperature (RT) to 358 K. From the quasi-static tensile test results, no specimen size effect on Young's modulus and yield stress was found, whereas the annealing and temperature influences were clearly observed. To investigate mechanical degradation to cycling loading, the cyclic loading tests were conducted under constant stressand strain-amplitude modes. In constant stress-amplitude mode, stain amplitude increased with an increase of loading cycles due to creep-like deformation. Almost of the specimens fractured during the tests. Meanwhile, in constant strain-amplitude mode, stress amplitude gradually decreased with increasing cycles due to stress relaxation, but no fatigue failure was found. The cyclic loading and stress relaxation tests revealed that creep deformation was dominant in the degradation of Al-alloy film subjected to cyclic motion. ©2009 IEEE.

This paper describes novel elongation-measurement device utilized for uniaxial tensile test. The device consists of two sets of micro probes with piezoresistive sensor for detection of gauge mark position on specimen, and multiple pairs of bimorph actuators for in-plane motion to scan the gauge mark. The voltage from the sensor is put out by the cantilever deflection when the cantilevers climb the gauge marks. By Joule's heating, movement of the bimorph actuator along one axis was achieved, and detection of gauge mark position was also realized. In the uniaxial tensile test of single-crystal silicon (SCS) film specimen, the mean Young's modulus of 164.0 GPa was able to be measured by using the device. The measured modulus agreed with that derived from CCD-image analysis. The developed device would be useful for measuring elongation of film specimen during the uniaxial tensile test.

This paper presents mechanical characteristics of sputtered Al-Si-Cu film used as a structural material in microelectromechanical systems (MEMS). Novel tensile test technique with an elongation measurement image analysis system has been developed. Uniaxial tensile tests were conducted at temperatures ranging from room temperature (R.T.) to 358 K. No specimen-size effect on Young's modulus, yield stress, and fracture strength, was found, whereas the annealing and temperature effects were clearly observed. To study mechanical degradation mechanism, cyclic loading tests were conducted under constant stress- and strain-amplitude modes. In constant stress-amplitude mode, stain amplitude increased with an increase of loading cycles due to creep-like deformation. Almost of the specimens fractured during the tests. Meanwhile, in constant strain-amplitude mode, stress amplitude gradually decreased with increasing cycles due to stress-relaxation, but no fatigue failure was observed.

This paper describes a simple evaluation method for in-plane Poisson's ratio of thin film materials. We designed an on-chip bending test chip that produces bending of film specimen via torsion bars, when applying normal load to loading levers. Using micro machining technologies, the test chip has been fabricated from SOI wafer. The profile of bent specimen obtained by using optical interference method enabled us to measure in-plane Poisson's ratio of the material. Average measurement value of in-plane Poisson's ratio was 0.079, which deviates by 10% from the anisotropic, finite element analysis of the test chip. The measured value includes approximately 23% error as compared to ideal value for (001)[110] single-crystal silicon (SCS). This is probably caused by strong anisotropy in the material.

This paper describes an experimental analysis method for evaluating surface stress distribution in single-crystalline silicon (SCS) microstructures using laser Raman spectroscope. A biaxial tensile tester designed for film specimens was employed to apply uni/biaxial stresses to SCS specimen having 270-nm-high, 4-mu m-square SCS convex structures in the gauge section. As reported in Transducers 2007, two-curve fitting of Raman spectrum was useful for analyzing stress magnitude at the edge of convex structures. In this study, the partial least-square (PLS) method was adopted for the obtained Raman spectra at the convex edge in order to determine stress components as well as their magnitudes. By using the PLS method, the shear stress component was able to be measured in addition to the normal stress components. The stress magnitude in respective stress components was in very good agreement with that estimated by finite element analysis (FEA).

This paper describes fabrication, characterization, and demonstration of a novel active micro-catheter with Ti-Ni shape memory alloy (SMA) actuators for wide range of forward-looking area to remedy diseased area inside a blood vessel. The developed active micro-catheter consists of eight Ti-Ni SMA spring actuators for catheter actuation, an ultrasonic piezoelectric transducer for forward-looking, a guide wire, a polyurethane tube for catheter coating, and spiral wirings for various flexure motions of catheter by Ti-Ni SMA actuators. The size of the catheter is 3.5 mm in diameter and 60 mm in length of the sum of transducer and actuator sections. Ti-Ni SMA springs were fabricated from a Ti-50at.% Ni sheet by electrochemical etching with a mixed solution of ethanol and lithium chloride. The micro-catheter was assembled by hand under a stereomicroscope. The tip of the produced micro-catheter was able to bend toward at least eight directions by controlling an applied current to Ti-Ni SMA springs. We have demonstrated the effectiveness of the active micro-catheter by carrying out experiments on blood vessels in a small animal.

To further understanding of the effect of Zr content on the shape memory behavior of ternary Ti-Ni-Zr alloy films, ternary alloy films were deposited with various Zr contents using triple source dc magnetron sputtering. Deposited films annealed at 700 degrees C showed martensite transformation accompanied with shape memory behavior. Martensitic transformation start (Ms) temperature of the ternary alloy film was found to increase with increasing Zr content for a Zr content higher than 10 at%. The highest Ms temperature attained was similar to 170 degrees C for a Zr content of 19.5 at%. Critical stress against plastic deformation was found to increase with increasing Zr content up to 10 aft. Although further increase of Zr content caused embrittlement, the Ti(32.3)Ni(48.2)Zr(19.5) film showed a shape memory effect with a recoverable strain of similar to 1.3% under a constant stress of 250 MPa. This indicates that the Ti-Ni-Zr alloy film is a promising candidate for cantilever type micro-actuators. (C) 2008 Elsevier Ltd. All rights reserved.

This paper describes the fatigue life of microscale single-crystal line silicon (SCS) and poly-crystalline silicon (PCS) used in microelectromechanical systems (MEMSs). The fabricated SCS and PCS specimens having nominal dimensions of 20 gm in width, 600 mu m in length, and 2 gm in thickness at the gauge section were subjected to cyclic loading by means of pulsating-tension fatigue test under a constant frequency from 1 to 10 Hz. The average fracture strengths of the SCS and PCS specimens measured by quasi-static tensile test were 3.26 and 2.08 GPa, respectively, which were utilized as the reference stresses in the fatigue test. In the fatigue test, the peak stress and stress amplitude were maintained constant for both the specimens. The number of cycles to failure increased with a decrease in the peak stress. No manifest fatigue limit was observed in both the specimens. The stress ratio parameter, sigma(peak)/sigma(f), gave a good correlation with the number of cycles to failure, and a large scatter of the lifetime data in the SCS specimens was found as compared with the PCS specimens. Scanning electron microscopy (SEM) suggested that a number of latent defects inside or on the surface of the specimen would have influenced the scatter of the fatigue life. Copyright (C) 2008 John Wiley & Sons, Ltd.

This paper describes the micro four-points bending technique developed for measuring mechanical strength of single-crystal silicon micro-specimen bonded with Ag-Sn eutectic solder film. The Young's modulus of silicon measured by the tester was in good agreement with the published value within 2% difference. It shows the tester has good measurement accuracy. Silicon micro-specimen bonded with Ag-Sn solder film was fabricated using Al/Ni multilayer film's exothermic reaction and external heating. The bending strength of the specimen fabricated using the Al/Ni exothermic reaction was lower than that fabricated using external heating.

This paper describes novel biaxial tensile test technique for a film specimen to investigate material responses to uniaxial and biaxial tensile forces. We have developed biaxial tensile tester that consists of four sets of actuator, loadcell, and displacement meter in order to apply an arbitrary amount of tensile force to a film specimen in each axis. With the uniaxial test specimen of sputtered Al-Si-Cu film at room temperature (RT), average Young's modulus of 66.4 GPa and yield stress of 139.1 MPa have been obtained. With the biaxial test specimen, the yield locus has been evaluated by applying biaxial stresses with various strain rate ratios. The obtained yield stresses could be fitted by the yield criterion based on Hill equation, indicating that the flow stress under biaxial stress condition differ from that under uniaxial condition. Information about the yield locus would be useful for the structural design of MEMS including Al-Si-Cu film structures subjected to biaxial stresses.

We have investigated the effect of Pd content on the shape memory behavior of Fe-Pd alloy films. Fe-Pd films with various Pd contents were deposited onto Si wafers with thermal oxide layer using a dc magnetron sputtering apparatus, and they were annealed at 900 degrees C for 60 min followed by iced water quenching. All the annealed films were confirmed to show shape memory behavior by thermal cycling tests under constant stresses. The M, temperature increases with increasing constant stress, obeying the Clasius-Clapeyron law. The M, temperature without stress was determined to be 70 degrees C for Fe-28.5mol%Pd film, and it decreases linearly down to -60 degrees C with increasing the Pd content up to 31mol%. Maximum recoverable strain was nearly constant at 0.7% when the Pd content was from 29 and 30.2mol%. Maximum critical stress against plastic deformation was 300MPa for films containing 29.9mol%Pd films, although it decreases rapidly with decreasing Pd content.

This paper describes novel biaxial tensile test technique for a film specimen to investigate material responses to uniaxial and biaxial tensile forces. We have developed biaxial tensile tester that consists of four sets of actuator, load cell, and displacement meter in order to apply an arbitrary amount of tensile force to a film specimen in each axis. With the uniaxial test specimen of sputtered Al film, average Young's modulus of 35 GPa and yield strength of 115 MPa have been obtained. With the biaxial test specimen, evaluation of the yield locus for Al film has carried out by applying biaxial stresses with various strain rate ratios. The obtained yield stresses could be fitted by the yield criterion based on Logan-Hosford equation. This indicates that the flow stress under biaxial stress condition differ from that under uniaxial condition. Information about the yield locus would be useful for the structural design of MEMS including Al film structures subjected to biaxial stresses.