bluuebunny/crossref_metadata_2025_split 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

AbstractIt 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

AbstractFormation 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

AbstractIn 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

AbstractAccelerated 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

AbstractTo 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

AbstractWhen 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

AbstractThe 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

AbstractThis 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

AbstractTo 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

AbstractThis 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

AbstractAs 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

AbstractThis 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

AbstractBulk‐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

AbstractA 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

AbstractTo 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

AbstractA 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

AbstractTo 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

AbstractIn 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.