bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth process of thin chemical vapor deposition‐aluminum films and its underlayer dependence—real‐time monitoring of reflected light intensity at the depositing surface
Authors: Kobayashi Akiko , Sekiguchi Atsushi , Okada Osamu , Hosokawa Naokichi , Sugai Kazumi , Kishida Shyunji , Okabayashi Hidekazu , Shinzawa Tsutomu , Yako Tadaaki , Kadokura Hidekimi
Published: July 2007

It is known that the reflectivity of aluminum (Al) film deposited by chemical vapor deposition (CVD) decreases with an increase of film thickness as its surface roughens. A thin, smooth film is effective for filling small holes and narrow trenches by confonmal deposition, but a rough surface is not effective.

In this study, a real‐time monitoring of the CVD‐A1 film deposition process has been attempted by measuring the reflected light intensity at the depositing film surface. By finishing the deposition when the monitored reflected light intensity of the He‐Ne laser reached the maximum, a film with a very smooth surface could be reproduced. Furthermore, the lower limitation of smooth continuous film thickness was compared for four different cases.

Investigated underlayers were Ti and TiN deposited by sputtering (SPT). On these underlayers, CVD‐Al film was deposited without exposure to atmosphere or with exposure to atmosphere prior to the deposition, resulting in a total of four deposition conditions. The results showed that Al film deposited on TiN without exposure to atmosphere had the thinnest and the smoothest continuous film among the four. Since the thickness was 60 nm, the filling of 0.12‐μm diameter holes or 0.12‐μm wide trenches can be expected by this process.
Formation of TiN/Ti adhesion layers by collimated sputtering
Authors: Ohsaki Akihiko , Fujisawa Masahiko , Kotani Hideo
Published: July 2007

Formation of a TiN/Ti adhesion layer by collimated sputtering for a structured surface with a high aspect ratio was investigated. The bottom coverage was simulated and the simulated and experimental results were compared. As a result, it was found that the simulated and experimental results were in agreement if the scattering of sputtered particles by gas was small.

Three‐dimensional simulation of wall coverage predicted a formation of constriction at the top of the contact hole and the formation of constriction was confirmed experimentally. The formation of constriction caused the peeling of an adhesion layer when a chemical vapor deposition (CVD) tungsten film was deposited. To avoid the formation of constriction, a tapered contact hole was used. It was found also that the contact resistance and junction leakage characteristics were improved by collimation sputtering when an adhesion layer was deposited in the contact holes with a high aspect ratio. It was concluded that this technology is advantageous in contact formation in devices with submicron structures.
Finite element analysis of plane wave diffraction from anisotropic dielectric gratings
Authors: Ohkawa Yuichi , Tsuji Yasuhide , Koshiba Masanori
Published: July 2007

In this paper, the formulation of the analysis based on the finite element method is presented for the first time for an anisotropic dielectric grating. By this analysis method, the diffraction characteristics of a plane wave by an anisotropic dielectric grating with an arbitrary shape can be computed easily. The finite element method is applied to the region corresponding to one period containing an anisotropic dielectric grating. The analytical relationships are applied to the boundaries on the incident and transmitted sides while the periodic boundary condition is applied to all other boundaries. Specifically, an index modulated grating and a groove grating are chosen for the analysis of the diffraction characteristics when the TE and TM waves are coupled. From the comparison with the analysis results by the coupled‐mode theory and the spatial harmonic expansion method, the validity of the present method is confirmed.
Long‐term reliability of Er‐doped fibers in hydrogen environments
Authors: Koyano Yasushi , Kakui Motoki , Kashiwada Tomonori , Onishi Masashi , Shigematsu Masayuki , Kanamori Hiroo , Nishimura Masayuki
Published: July 2007

Accelerated tests of Er‐doped fibers in hydrogen environments are carried out and as the evidence of their long‐term utilization, the degradations in loss and gain are estimated. The hydrogen‐induced loss‐increase in Er‐doped fibers with 0 to 3 percent aluminum (Al) content is formulated. As the results of quantitative investigations, it is understood that during 25 years of use, there is almost no transmission loss increase in 1.55 μm wavelength region and at hydrogen partial pressure of 0.001 atm and 40°C if there is no Al content.

In case of 1 wt% Al content, the loss increase is 0.04 dB/20 m while it is 0.08 dB/20 m if the Al content is 3 wt%. Further, it is possible to describe the gain degradations, under hydrogen environment, by the increase of background losses. Under the forementioned conditions, the gain degradation is estimated to be 0.07 dB if the Al content is 1 wt% and 0.15 dB if the content is 3 wt%. Therefore, it becomes clear that their characteristics are immune to hydrogen environment in real applications.
Measurement errors in effective channel‐length extraction
Authors: Terada Kazuo
Published: July 2007

To evaluate the accuracy of the effective channel‐length extraction method, the behavior of the measurement errors in the least‐square method, used twice in the extraction procedure, is studied. It is found that the increased number of data are mainly effective in suppressing the dispersion of the measurement data; these data are also somewhat effective in reducing the actual measurement errors. Based on this result, the actual effective channel‐length extraction using experimental MOSFET data is studied. It is observed in the samples used here that the linear relation between total MOSFET resistance and design channel length changes in short channel region. It is found in such a case that as many reference MOSFETs as possible, including both short and long MOSFETs, should be used.
Switched capacitor circuits with compensator for clock feedthrough effects
Authors: Masunari Hayato , Jyo Yoichi
Published: July 2007

When a switched capacitor circuit is constructed, a provision for output offset voltage generation by the effect of the clock feedthrough charge is indispensable. Especially in the circuit made of individual components using commercially available analog switches, this effect is significant.

In this paper, the generation mechanism of the feedthrough charge in an analog switch is analyzed and a circuit configuration method is proposed for compensation of the feedthrough effect for the integrator as the most fundamental switched capacitor circuit. Also, by a comparison experiment, with the conventional method, the effectiveness of the proposed circuit is confirmed.

The circuit size is larger as an integrator itself than the one by the conventional method. However, even in the case with a multiple cascading of the integrators such as in a higher‐order filter, the feedthrough compensation is possible with only one feedback loop so that the overhead for the increased circuit size can be reduced. According to the trial circuit, the output offset voltage can be suppressed to the level of several millivolts. Hence, the present method can be applied to various operating circuits with high accuracy.
An insulated gate bipolar transistor with high surge endurance
Authors: Tokura Norihito , Okabe Naoto , Hara Kunihiko
Published: July 2007

The relationship between the device property under drain‐source breakdown and device structure parameters of insulated gate bipolar transistors was simulated. Then the following facts were revealed: 1) the impurity concentration in the n−drain layer and the layer thickness determine the breakdown mode. One such mode is the avalanche‐suppressed punch‐through mode proposed by the authors, where the depletion layer in the n−drain layer reaches the p+drain substrate and breakdown is caused by the hole injection from the p+drain substrate to the n−drain layer. Another mode is the nonpunch‐through mode, where avalanche takes place in the neighborhood of the junction between the p body layer and n−drain layer, causing breakdown; 2) the breakdown energy spreads more and the hot carrier concentration near the device surface is lower in the avalanche‐suppressed insulated gate bipolar transistor than in the nonpunch‐through insulated gate bipolar transistor. As a result, the breakdown resistance of the former transistor is higher than that of the latter transistor; and 3) it was found that the breakdown voltage is more stable against the changes in the drain current and temperature in the former transistor than in the latter transistor. It was found also that the former transistor has a higher surge energy endurance than the latter transistor.
Improved spin‐on glass process with multilevel metallization
Authors: Ohashi Naofumi , Nezu Hiroki , Owada Nobuo , Hirasawa Shigeki
Published: July 2007

This paper reports on recent improvements in organic spin‐on glass (SOG) planarization technology combined with etch‐back process. A general rule has been established for SOG planarization mechanism that is suitable for every kind of wiring pattern distribution. This general rule, the volume constant rule, shows that the SOG volume in a certain projection length along the horizontal direction is constant and independent of the wiring width. Based on this rule, it is found that the SOG planarization process margin can be increased significantly by decreasing the plasma SiO2 (= P‐SiO2) layer thickness underneath the SOG layer.

The characteristics of this newly developed organic SOG material have been investigated. This new organic SOG material developed by Hitachi Chemical Company, Ltd. (HSG‐2209S‐R7) has heat reflow capability that causes the movement of SOG on the wires to the space during the second baking; this results in improvements in local planarization and decrease in the SOG thickness on the wires.

A six‐level metallization test structure for a logic LSI has been successfully created using the optimized process conditions.
Characterization of TiN/TiSi2bilayer formed by sputter deposition from a TiN0.4alloy target and subsequent lamp annealing and its application to a contact system
Authors: Nakamura Hiroki , Fushimi Kimihisa
Published: July 2007

To develop a thermally stable barrier metal for interconnections in LSI, films deposited by sputtering a Ti‐rich TiN0.4target were investigated (in what follows, the film deposited in this manner will be referred to as TiN0.4). Both film quality and the electrical property of the Al‐alloy/Si contact with thin barrier metal were evaluated. It was found that the TiN layer formed by this method was twice as thick as the TiN layer formed by the conventional method, the TiN/TiSi2layer formed was smooth and the silicide layer was five times thinner than when the conventional method was used. The TiN layer formed by nitridation of TiN0.4(50 nm)/Si had a grain structure with a grain size of approximately 10 nm and was strongly oriented to TiN (200). In the silicide layer, the grain size was approximately 50 nm and a semistable phase was formed. It was also found that contact resistance to N+Si was similar to that formed by using the conventional Ti nitridation method while the contact resistance to P+Si was slightly lower than when the conventional method was used. In addition, it was found that the contact resistance became lowest when the rapid thermal nitridation (RTN) temperature was approximately 700°C and the formed film was stable when it was thermally treated. When a Ti layer was used, the N+/P junction showed a leakage problem after it was annealed at temperatures higher than 450°C. However, when TiN0.4was used, no leakage problem was observed even when the junction was annealed at 525 °C. These superior junction characteristics were due to the thermally stable and thick TiN layer.
Temperature‐compensated crystal oscillators
Authors: Ueno Yoshifusa
Published: July 2007

This review paper describes the basic principle of temperature‐compensated quartz oscillators (TCXOs) which are employed extensively in both industrial and consumer electronics.

A brief history of quartz oscillators and artificial quartz crystals is given at the beginning followed by a discussion on the recent applications of TCXOs.

Direct and indirect methods for compensating the effects of temperature on oscillation frequency in temperature‐compensated crystal oscillators which consume low power and are miniature are then described.

In the directly temperature‐compensated crystal oscillators, temperature compensation networks (TCNs) can be either of the serial type or of the parallel type. In this paper, the function of a TCN is described using a parallel‐type network as an example.

In the indirectly temperature‐compensated crystal oscillators, the functions of a TCN are discussed separately in high, intermediate and low‐temperature regions. Digitally controlled temperature‐compensated crystal oscillators are also included in this paper as the high‐precision temperature‐compensated crystal oscillators.

Some outstanding issues in TCXOs are discussed, and a new type of TCXOs have been proposed to overcome the shortcomings of conventional TCXOs.
Propagation properties of love wave‐type surface‐acoustic wave on α‐quartz
Authors: Isobe Atsushi , Hikita Mitsutaka , Asai Kengo
Published: July 2007

As a piezoelectric substrate for surface acoustic wave devices, the LST cut quartz has good temperature characteristics and low propagation loss. However, as the thickness of the metal electrodes on the substrate surface is increased, propagation loss also increases. Further, the electromechanical coupling coefficient is small. In this paper, a cut angle of the quartz substrate is sought that has excellent temperature stability, low propagation loss, and a large electromechanical coupling coefficient in the present of metal electrode films. For the rotated Y‐cut substrate in the neighborhood of the LST cut, the propagating surface acoustic wave (SAW) mode changes from the leaky surface wave to the Love wave‐type surface acoustic wave for which no propagation loss occurs in theory while the electromechanical coupling coefficient increased to 0.5 percent at the maximum if gold is used for the electrodes and the propagation direction of the SAW is shifted from the X axis. This is shown by simulation. By experiment, it is shown that the second‐order temperature coefficient is on the same order as that of the ST‐cut quartz substrate.
A high‐pass/lowpass phase shifter with resistive matching networks
Authors: Iyama Yoshitada , Iida Akio , Ishida Osami , Urasaki Syuji , Andoh Naoto
Published: July 2007

This paper proposes a high‐pass/lowpass phase shifter with improved reflection and phase‐shift characteristics using resistive matching networks. The circuit configuration, reflection characteristics, phase‐shift error‐reduction methods, and the design results are described. The relationship between the reflection of the single‐pole, double‐throw (SPDT) switch and the phase‐shift error is discussed in the high‐pass/lowpass phase shifter using filters to switch the SPDT switch. The reflection of the SPDT switch caused by the parasitic resistance of the switching device is investigated, and an impedance matching method using the resistive matching networks is proposed to reduce reflection. The calculation results for an S‐band phase shifter with the resistive matching networks show that the matching can be achieved even for switching devices with resistance and that the phase‐shift error can be reduced. An S‐band, 90° single‐bit phase shifter has been designed and a low return loss of better than 19 dB and a phase‐shift error of less than 4° are achieved, which confirms the usefulness of the resistive matching networks.
Bulk‐type domain reversal grating of LiTaO3 crystal fabricated by direct electric field
Authors: Sato Manabu , Ohashi Motoki , Abedin Kazi Sarwar , Takyu Choichi , Ito Hiromasa
Published: July 2007

Bulk‐type domain reversal gratings of LiTaO3 crystal were fabricated at room temperature by the direct electric field method. The nonlinear optical property of the crystal was evaluated by quasi‐phase matching. The period of the bulk‐type domain reversal gratings on an LiTaO3 substrate was 7.5 μm and the domain reversal extended to the entire substrate thickness of 500 μm. The experimental normalization efficiency was 0.46 % W cm in second‐order quasi‐phase matching and was close to the theoretical value (0.48%W cm). This result indicates that high‐efficiency nonlinear interaction could be achieved by using the bulk‐type domain reversal grating. The bulk‐type domain reversal grating of nonlinear optical crystal such as LiTaO3 is expected to be useful for compact nonlinear optical devices and integrated laser sources.
Enhanced nitridation of silicon at low temperature by ultraviolet irradiation
Authors: Ishikawa Yutaka , Tamagawa Tomohisa
Published: July 2007

A method to enhance nitridation of silicon at low temperature by ultraviolet irradiation is proposed and the nitridation mechanism by this method is discussed. The nitridation of silicon is carried out by irradiating an ultraviolet beam from a low‐pressure mercury lamp on the silicon substrate covered with a thin layer of ammonia. In this method, the attenuation of the ultraviolet beam is small and ammonia is decomposed effectively on the silicon surface. As a result, silicon nitridation is accomplished at a temperature lower by 300°C than in the conventional thermal decomposition method.

The nitride film contained a small amount of free oxygen, which is the result from the natural oxide film on the silicon surface and is not introduced during the nitridation process. The silicon nitridation progresses by the diffusion of the nitriding species through the nitride film and the reaction between the nitriding species and silicon on the silicon surface. Both diffusion and reaction are enhanced by ultraviolet irradiation. The active species caused by the decomposition of ammonia by ultraviolet irradiation play an important role in the enhancement of the nitridation. At the same time, the effect of surface excitation by ultraviolet irradiation is not negligible.
Influence of contact hole profile and underlayer materials on aluminum reflow filling properties
Authors: Ito Nobukazu , Yamada Yoshiaki , Kikuta Kuniko , Kikkawan Takamaro , Huo Donald Tai‐Chan
Published: July 2007

To investigate the reflow filling property of Al‐Si‐Cu in a contact hole with a high aspect ratio, the influences of the contact hole profile and underlayer material on the filling property were evaluated. It was found that in order to fill a contact hole, the wall of the contact hole must be covered with an Al‐Si‐Cu layer thicker than a certain thickness, prior to reflow. The minimum thickness of the Al‐Si‐Cu layer on the wall, that is, step‐coverage, was dependent on the aspect ratio of the contact hole. Therefore, the reflow filling property was restricted by the aspect ratio of the contact hole. In addition, it was found that the minimum thickness of the Al‐Si‐Cu layer could be reduced if Ti or TiSi2was used as the underlayer for reflow, resulting in the increase of the aspect ratio.

When TiSi2was used, the alloy spikes, which were always observed when Ti was used, could be avoided. Therefore, it was found that TiSi2was excellent as an underlayer material when Al reflow was employed for filling contact holes.
Ripple current analysis of an electrolytic capacitor in power factor correctors
Authors: Shoyama Masahito , Kurachi Toshiaki , Ninomiya Tamotsu
Published: July 2007

A large electrolytic capacitor usually is employed at the output terminal of power factor correction circuits to suppress the high‐frequency switching ripple voltage as well as the low‐frequency ripple voltage. Due to the equivalent series resistance of the electrolytic capacitor, the capacitor current causes power loss which increases its temperature and may shorten its life. Thus, it is important to estimate accurately the effective value of the capacitor current for a proper choice of the capacitor and to maintain the expected life of the capacitor.

This paper presents a detailed analysis of the ripple current of an electrolytic capacitor in the boost‐type power factor correction circuit. The ripple current is divided into two components, namely, the low‐frequency and the high‐frequency components. The root‐meansquare value of the capacitor current is divided for both frequency components. The analytical results are confirmed by experiments.
Analysis of current densities induced inside a human model by the two‐step process method combining the surface‐charge integral equation and the finite‐element method
Authors: Chiba Atsuo , Isaka Katsuo
Published: July 2007

To analyze the density of the current induced in the human body by the coupling phenomena of the ac electric field and the human body, the integral‐equation method and the finite‐element method have been proposed. However, there is no effective method for the analysis of the induced current density including the directional component in the model with a three‐dimensional human body shape by taking into account the conductivity of human tissues.

The authors have developed a method for the analysis of the induced current density in the three‐dimensional shape model by a two‐step process consisting of: (1) the derivation of the induced current flowing in from the surface of the human model by the surface charge method; and (2) the application of these values as the boundary values of the finite‐element method using an isoparametric hexahedral element. The model can analyze the induced current density in the model by directly considering the conductivity and the permittivity of the human tissues. The results of the analysis of the induced current density in the present model have been confirmed from the experimental results of the metallic human model with the identical shape.
Voltage controlled self‐temperature compensated crystal oscillators with NS‐GT cut quartz resonators
Authors: Kawashima Hirofumi , Sunaga Kenji
Published: July 2007

In this paper, voltage controlled self‐temperature compensated oscillators made with NS‐GT cut quartz resonators (VC‐S‐TCXOs in what follows) are introduced and their frequency stability (obtained by controlling input voltage to VC‐S‐TCXO) is discussed. An oscillator circuit consists of a CMOS inverter, a variable capacitor diode, resistors, and capacitors. The primary oscillator frequency of the coupled quartz resonator is first derived from the electric equivalent circuit of the oscillator. The oscillator frequency is given by a function of the coupling coefficient, which in turn is given as a function of the load capacitanceCL. Since frequency stability by controlling the input voltage to VC‐S‐TCXO is dictated by the VC circuit, the VC circuit was investigated in detail in order for the circuit independent of temperature to be obtained. Using the VC circuit, the oscillator frequency was controlled by the input voltage and the temperature stability of the oscillator frequency was less than 4 × 10−9at a temperature range of ‐30 to 85 °C. Furthermore, it has been demonstrated experimentally that the frequency stability of the VC‐S‐TCXO directly after voltage control does not depend on the frequency temperature characteristics of the quartz resonator, time interval between the voltage control, or rate of temperature change.
A new algorithm for transient analysis of electromagnetic wave systems
Authors: Kuroiwa Takashi , Hosono Toshio
Published: July 2007

In the analysis of a general linear system including the electromagnetic wave transmission systems, it is often necessary to derive system functions such as the immittance function and the transfer function from the frequency characteristics. In solving these problems, it is possible to use the Herglotz‐Cauer theorem for the immittance function and Hosono's theorem for the transfer function. In these theorems, it is necessary to calculate integrals on the frequency when the system function is derived. There are a limited number of cases that can be solved analytically. However, when Hosono's theorem is combined with the fast inversion of Laplace transform (FILT), it is predicted that such a combination is a powerful tool for analyzing the transient phenomena of the electromagnetic wave propagating in plasma, waveguides, and optical fibers. To confirm such a prediction, the transient phenomena of the electromagnetic wave propagating in a plasma were analyzed as an example so that the effectiveness was supported.
Fast ROM macrocells for ASICs
Authors: Shibata Nobutaro
Published: July 2007

SRAMs and ROMs are installed on high‐performance ASICs as the memory macrocells. This paper discusses the design of mask ROMs as the macrocells from the viewpoint of the high‐speed and low‐power dissipation. NOR‐type memory cell array configuration is adopted, and the memory content is set using the LSI mask for contact process. A memory cell programming method is proposed where the source of the MOS transistor and the GND line are connected or disconnected according to the memory content. In this method, the adjacent colls can share the contact area to a bit‐line. This helps to reduce the p‐n junction capacitance, which dominates the parasitic capacitance of the bit‐line, to be halved. Using a reference voltage generator, the bit‐line is controlled close to GND level, which improves the detection sensitivity of the current‐mirror sense amplifiers. The small‐amplitude operation of the bit‐lines is realized and the access time is reduced. As a technique to reduce the power dissipation, the virtual GND lines are introduced, which are controlled by the column address signals. The lines are controlled to the floating state in the stand‐by mode so that the dynamic power dissipation is reduced. A test chip was designed and fabricated by a 0.5‐μm CMOS process, and the address access time of 7.2 ns was obtained for the 4‐K word × 4‐bit organization.
Circularly polarized absolute‐value rays in stratified absorbing media
Authors: Tokumaru Shinobu
Published: July 2007

To provide an example of circularly polarized absolute‐value rays in a nondispersive absorbing medium, the theory of ray tracing is presented in the case in which a plane wave is incident on a planar layered medium. Specific tracing methods are presented for the loci of the real phase plane normal, the loci of the projection ray related to the flow line of the normalized Poynting flux, the loci of the circularly polarized absolute‐value rays, and the intensities of these rays. The relationships to Poynting flux and their tracing method are described. Further, in the planar layered medium, an anisotropic projection ray index of refraction is introduced to the projection ray. It is shown that Fermat's principle holds under this index of refraction. On the other hand, Fermat's principle also holds in the tracing of the trajectory of the real‐phase plane normal. In Fermat's principle of the projection ray, its relationship to the energy flux density is new.
A magnetostatic wave radiation impedance of symmetric slot line in signal‐to‐noise enhancer
Authors: Asao Hideki , Miyazaki Moriyasu , Oh‐Hashi Hideyuki , Ishida Osami
Published: July 2007

In a slot‐line‐type signal‐to‐noise enhancer for a magnetostatic wave, it is shown theoretically and confirmed experimentally that enhancement can be improved by the symmetric slot‐line structure with yttrium iron garnet (YIG) films on both sides of the slot line and by the layered structure of high permittivity materials. It is shown that the improvement in the amount of enhancement requires an increased attenuation constant of the slot line caused by the conversion loss of the linear operation to the magnetostatic wave. The magnetostatic wave radiation impedance is then derived by recognizing the contribution of the magnetic flux density normal to the slot plane among the electromagnetic field components traveling along the slot line to the conversion of the magnetostatic wave. By means of this radiation impedance, the attenuation constant is derived for the symmetric slot line and the slot line with a high permittivity layered structure so that improvement to enhancement is clarified.
Analysis and experiment on phase‐conjugate reflectivity of CAT mirror
Authors: Yamada Hiroshi , Okamoto Atsushi , Enbutsu Koji , Mishima Teruhito , Sato Kunihiro , Sakuraba Ichiro
Published: July 2007

The effects that the arrangement of light rays inside the photorefractive crystals have on the reflectivity of CAT mirrors are analyzed anew. Experiments are performed using BaTiO3 crystal and the measured results are compared with those of numerical calculations.

First, for generation of beam fanning in photo‐refractive crystals, three different cases of generation are considered, i.e., at the plane of incidence of the crystal, in the range of maximum coupling coefficient, and in the range of maximum coupling strength. Next, the light‐ray incident conditions (incident position, incident angle, and beam radius) and the generating position of beam‐fanning associated with variations of light‐ray arrangement inside the photorefractive crystal are simulated. In each of these three cases, the phase‐conjugate reflectivity is estimated via numerical calculations from which the effects that light‐ray arrangement have on reflectivity is clarified.

Finally, experiments are carried out using a BaTiO3 crystal and the measured data are compared with the simulated results. It is shown that if the angle of the incident beam with respect to the crystal is large, beam‐fanning is generated at the position where the coupling coefficient is at its maximum. When the angle of incidence is small and in the range of small values of the position of incidence, beam‐fanning occurs in the plane of incidence of the crystal. Using this analysis, the light‐ray arrangement required in achieving high phase‐conjugate reflectivity is clarified.
Effects of specimen shape on the measurement of the electromechanical coupling coefficient in inclined electrodes
Authors: Adachi Yutaka , Takenaka Tadashi
Published: July 2007

The electromechanical coupling coefficient k can be determined by measuring the frequency characteristics of admittance. However, it is known that the specimen shape affects the measurement of the admittance frequency characteristics. In this paper, the finite element method was employed to investigate the effects of sample electrode inclination on the electromechanical coupling coefficients. The results indicate that the electromechanical coupling coefficients for the stretching vibration mode (31) of a rectangle, the stretching vibration mode (33) of a bar, and the expansion vibration mode (p) of a disk decrease when the sample electrodes are inclined. No spurious vibration was observed in the transverse vibration of (31) and (p) modes when the sample electrodes were inclined. However, a spurious vibration was observed in the longitudinal vibration of the (33) mode. These observations were confirmed by experiment.
Ultrasonic motor based on coupled longitudinal‐bending vibrations of a diagonally symmetric piezoelectric ceramic plate
Authors: Aoyagi Manabu , Tomikawa Yoshiro
Published: July 2007

This paper discusses the operating principle and performance characteristics of an ultrasonic motor based on the coupled longitudinal‐bending vibrations of a diagonally symmetric piezoelectric ceramic plate. It is well known that longitudinal and bending vibrations couple with each other in a diagonally symmetric piezoelectric ceramic plate.

The objective of this investigation is to design a simple and thin ultrasonic motor based on these coupled mode vibrations. The design of a stator for an ultrasonic motor was optimized with respect to vibration mode, capacitance ratio, and direction of vibratory displacement by employing the finite element method. A simple ultrasonic motor was built and its performance was tested. The results indicate that its load characteristics vary widely depending on the contact point of the rotor and the geometry of a piezoelectric plate. Furthermore, attempts were made to equalize load characteristics for bidirectional operations. The efforts revealed that it is possible to equalize the rotation rate, but it is difficult to equalize efficiencies for bidirectional operations. By incorporating a self‐oscillation circuit with an inverter, it is possible to run the motor bidirectionally in a single‐phase mode.
New microscope for measuring the distribution of nonlinear dielectric properties
Authors: Cho Yasuo , Kirihara Akio , Saeki Takahiro
Published: July 2007

This paper describes a new technique for imaging the distribution of nonlinear dielectric constants of ferroelectric materials. This technique is based on the principle that the nonlinear (third‐order) dielectric constants (third‐rank tensor) are very sensitive to the state of the spontaneous polarization and the quality of the crystallization of materials, while the linear (second‐order) dielectric constants (second‐rank tensor) are insensitive to them. Applying this principle, a new microscope for measuring the distribution of nonlinear dielectric properties is developed. This new microscope is used to observe the distribution of the polarization of ferroelectric materials such as lead zirconate titanate (PZT) ceramic and piezoelectric polymer.
Transmission loss of thick‐film conductor lines at microwave frequency
Authors: Ogawa Toshio , Kamimura Noritaka
Published: July 2007

In the hybrid integrated circuit systems which process the RF signal for communications, the transmission loss tends to increase as the frequency is increased, which is a significant problem in the circuit design. The authors have considered thick‐film conductors as conductor materials for the circuit because the thick film is of relatively low cost and can be mass produced. The transmission loss of the RF signal in such a circuit was evaluated experimentally up to 20 GHz.

It was found that high‐purity alumina (99.5 percent) is suitable as ceramic substrate material, the transmission loss is too large to be practical in the Ag/Pd conductor system and the transmission losses are not very different and are in the practical range for Au, Ag, Ag/Pt, and Cu conductors. Contrary to the general belief, it was found that the transmission loss can be reduced if the surface of the ceramic substrate is made rough. In order to find the reason, the fine structures of the cross section of the thick‐film conductor was investigated.
Effect of switching interval on some characteristics of relay contacts
Authors: Kubono Takayoshi , Mogami Masahiko
Published: July 2007

A normal, open electrical contact pair, mounted in a small relay, was used to make and break repeatedly a dc, 30V/3 Ω resistive circuit up to 100 thousand times; and the relationship between data for each switching and switching interval are analyzed in this paper. Four kinds of switching intervals are set by changing the frequency of applying the rated voltage to drive the electromagnetic coil.

No special relationship was found between four different switching operation intervals and data for bounce number at make, arc duration at make/break, and contact resistance at 500 ms after the 10‐A current began to flow.

On the other hand, the following points became clear through the experiments.

— Temperature at the backside of contacts at 500 ms after the 10‐A current began to flow changes drastically by the difference of the switching interval.

— Temperature rise changed linearly and was proportional to the contact resistance at each switching interval.

— The more frequent the switching interval, the larger the proportional coefficient.

By these results of experiments, the following facts were concluded.

— Temperature of electric contact increases with Joule heating of contact resistance and the resistance of the conductor including supporting arms.

— The shorter the period of the separated contacts, the larger the temperature difference between measuring point and room temperature became.
Nanohenry inductance measurement using a low parasitic‐inductance probe
Authors: Shimizu Hiroya , Nagata Tatsuya , Nakamura Atsushi
Published: July 2007

The increased speeds of logic circuitry make the electrical characteristics of LSI packages more important. This is especially true of inductance, which is the main source of simultaneous switching noise (SSN). To improve the accuracy of SSN simulations, inductance models of LSI packages should be represented by inductance matrices; and, thus, to construct precise models, it is necessary to have an inductance measurement method.

A new inductance measurement method of nanohenry‐order accuracy is proposed that uses an LCR‐meter. Since the parasitic inductance of measurement probes usually decreases accuracy, a special probe with minimized parasitic inductance was developed.

The new measurement method has the additional advantage of high spatial resolution. The results of measurements proved to be in good agreement with calculations.
Elastic wave energy‐trapping and its application to piezoelectric devices
Authors: Nakamura Kiyoshi
Published: July 2007

If it is possible to trap elastic wave energy in a localized region of an elastic solid, it is possible to support the solid at a location where no vibration occurs. This enables highly reliable, low‐loss piezoelectric devices to be developed. In this paper various energy‐trapping elastic wave phenomena and vibration are discussed and their applications to various piezoelectric devices such as strip resonators, monolithic filters, piezoelectric transformers, vibratory gyroscopes and SAW devices are described.
Enzyme biosensor based on surface acoustic wave device
Authors: Kondoh Jun , Imayama Teruo , Matsui Yoshikazu , Shiokawa Showko
Published: July 2007

In a shear horizontal surface acoustic wave (SH‐SAW) propagating through a piezoelectric crystal, shear wave and piezoelectric potential due to piezoelectric effect are combined. SH‐SAW can be useful for chemical sensing in the liquid phase. When the load liquid and propagation surface are in contact, the change in the electrical property of the liquid can be detected due to the acoustoelectric interaction. This paper describes a new type of acoustoelectric biosensor with an enzyme membrane on the SH‐SAW propagating plane for detecting pH change in liquid and reports that the SH‐SAW enzyme sensor with urease is highly sensitive in detecting urea. In addition, this paper describes the detection limit, aging characteristic, and high sensitivity of the detector.
Pyroelectric infrared sensor using PZT thin plate on diaphragm as sensitive elements
Authors: Taniguchi Yoshiharu , Murakami Kensuke , Kobayashi Hiroshi , Tanaka Shosaku
Published: July 2007

To improve performance characteristics of a pyro‐electric infrared sensor, especially voltage responsivity (Rv), noise equivalent power (NEP), and response speed, it is necessary to reduce the heat capacity of an infrared sensing element which is made of Pb(Zr, Ti)O3 (PZT) ceramics. A new design for a sensor whose sensing element is made of a thin bulk PZT ceramic plate mounted on a diaphragm fabricated by the Si micromachining method has been proposed and its prototypes have been tested.

The prototype sensor has a PZT ceramic plate which is about 10‐μm thick and has a sensing area of 1 × 2 mm2. The new sensor has an Rv value of 36.3 to 37.9 mV/μW which is about five times higher than a pyroelectric sensor with a 100‐μm thick PZT bulk ceramic plate. The amount of sensor noise was expected to be reduced by half. However, the amount of sensor noise increased by a factor of two. Because of the increase in the sensor noise, the values of NEP were 1.8 to 3.3 × 10−2 μW, which is a factor of two to three smaller than the NEP value of the bulk sensor. Furthermore, the rise time decreased to 31 to 35 ms, which is 10 to 20 percent shorter than that of the bulk sensor. Thus, the reduction of sensor noise will be an important challenge for the future.
Application of screen‐printed rare earth oxide protective film to alternating‐current plasma display panels
Authors: Koiwa Ichiro , Kanehara Takao , Mita Juro
Published: July 2007

Screen‐printed protective film of rare earth oxides (La2O3, Gd2O3, Dy2O3, Y2O3, and Yb2O3) was applied to ac‐plasma display panels. Screen‐printed rare earth protective films have higher luminous efficiencies than a sputtered MgO protective film. However, it is difficult to obtain a low firing voltage (Vf) from screen‐printed rare earth oxide protective films.

Only the La2O3 protective film has a lower firing voltage than the sputtered MgO protective film. Gd2O3 has the lowest sustaining voltage (VS) which is 54 V lower than that of the sputtered MgO protective film. Since rare earth oxide powders with high crystallinity exhibit superior discharge characteristics, it is necessary to improve the crystallinity of the powders. In order to obtain a high luminous efficiency, it is necessary to have a low discharge current. Both Y2O3 and La2O3 have a high current‐limiting effect. The current‐limiting effect is related closely to cell resistance. Since Dy2O3 has a low cell resistance, its current‐limiting effect is low. Gd2O3 has the highest luminance per unit discharge current. If it is possible to reduce the discharge current of Gd2O3 further, it is possible to obtain a higher luminous efficiency. Every screen‐printed rare earth oxide film has an excellent protective effect. However, from the viewpoint of low discharge voltage and high luminous efficiency, La2O3 and Gd2O3 are superior to all other rare earth oxides due to their low discharge voltage and high luminous efficiency.
Reliability of tape automated bonding using Au‐Sn alloy
Authors: Shibata Susumu , Kimura Masaru
Published: July 2007

This paper describes the relationship between the tape automated bonding (TAB) condition and reliability.

When too much bonding pressure is applied in inner lead bonding, the bonding characteristic of a finger in contact with a bonding tool edge tends to degrade. When bonding pressure exceeds 21.0 kg/mm2, the finger penetrates a bump, causing damage in the Al pad. The size of the finger is much larger than that of the solder bump. However, if the bonding condition is appropriate, the bonded section is reliable. Adhesive thermal resistance for securing Cu fingers on the TAB tape determines the upper limit of inner lead‐bonding temperature. The alloy is formed during bonding operation. The alloy formation is not sufficient at 380°C, but it is sufficient at 500°C. In outer lead bonding, bonding pressure should be controlled to prevent the substrate surface from cracking. Increasing pad length and width and reducing the temperature difference between the bonding tool and test piece were effective in preventing cracks. In both inner lead and outer lead bonding, the damage of fingers, separation of the bump from the pad, and substrate surface cracking must be taken into account in addition to the properties of the bonded area.
Head‐positioning control system for small‐sized hard disk drives
Authors: Yamada Takehito , Takakura Shinji
Published: July 2007

High track density has been achieved by adopting an H∞ controller with a feed‐forward compensator using adaptive filter theory in a sector servo system. In applying the H∞ control theory, a state‐space model of an augmented plant was constructed considering the input location of the disturbance. Moreover, to reduce repeatable runout, an experiment involving a feed‐forward control system including an adaptive FIR filter was performed. As a result, the head‐positioning accuracy was improved by approximately 15 percent compared to the case without feed forward. A 0.15‐μm head‐positioning accuracy was achieved. This level of accuracy means that a track density of 310 tracks/mm (8100 TPI) can be realized.
Low‐cost and high‐quality method of outline font transformation
Authors: Wada Hiroshi , Wakisaka Shinji , Sato Hiroko , Hayashi Shigeo , Kiriyama Norio
Published: July 2007

The outline font is used widely in operational amplifier (OA) equipment since the expansion and modification of a character can be realized with a high quality. The authors developed a system which realizes LSI with a low cost that can expand the outline font with a high quality, aiming at the installation on a low‐cost note‐type word processor. The proposed system executes the character correction, the affine transformation, the third‐order Bezier curve interpolation, the outline generation, the painting, and the memory clear processings which are needed in the outline font expansion.

The processings are divided into two blocks from the viewpoint of the processing time, and the blocks are processed by a pipeline. The vertical/horizontal scaling of the character is indispensable as a function of the word processor. The vertical/horizontal operation is included in the operation matrix of the affine transformation, which helps to suppress the increase of the processing time.

To cope with the fluctuation of the line width due to the operation error, a powerful character correction function is installed in order to improve the quality. By those considerations of the architecture, all outline font expansion processings are installed on the single‐chip LSI, which is realized on 8.5 mm × 8.5 mm, by CMOS 1.0‐μm process. The expansion speed of 860 characters/s (64 × 64 dot) is realized.
Formation of copper interconnects by the reflow of sputtered copper films
Authors: Abe Kazuhide , Harada Yusuke , Hashimoto Keiichi , Onoda Hiroshi
Published: July 2007

The formation of Cu interconnects using conventional sputtering and reflow processes has been studied. The use of W, Mo, and TiN underlayers makes it possible to fill grooves with Cu at reflow temperatures as low as 450°C. There is a close relationship between filling characteristics and agglomeration. Cu films agglomerate more easily on W, Mo, and TiN underlayers than on TiW and Ta underlayers because of their low Cu wetta‐bility. It was found also that Cu agglomeration was affected drastically by underlayer surface roughness. By adding the CMP process to the conventional sputtering and reflow processes, Cu interconnects down to 0.6 jim in width have been fabricated successfully. The resistivity of the interconnects is about 1.9 μω.cm.
Finite‐volume/time‐domain analysis of electromagnetic wave propagation in two‐dimensional tunnels with fundamental junctions
Authors: Uchida Kazunori , Matsunaga Toshiaki , Han Kyung‐Koo , Kim Ki‐Chai
Published: July 2007

The problem of electromagnetic wave propagation in tunnels with branches and bends, such as those that would be found in an underground shopping center, has been analyzed with the finite‐volume/time‐domain (FV‐TD) method. The FVTD method is based on difference equations discretized by a volume integration of Maxwell's equations for arbitrarily small polygonal cells. In this method, the medium constants within the infinitesimal cell are constant and their values differ from cell to cell. Therefore, this method can easily handle the boundary value problem with an arbitrary shape that contains inhomogeneous media. In homogeneous media, the FVTD method and the finite‐difference/time‐domain (FDTD) method are equivalent in the Descartes coordinate system. In one application of the FVTD method, numerical calculations were made for tunnel structures that are typically difficult to analyze. To prove the usefulness of the FVTD method, a microwave simulation experiment was done. The numerical and experimental values were shown to agree well.