Conference Abstracts

Group B: Devices

Session 8: Optical and Display Devices

Session 11: Semiconductor Devices I

Session 14: Storage Devices

Session 19: Semiconductor Devices II


Session 8: Optical and Display Devices

8-1 Title Silica Bragg fiber taper for subwavelength beam generation
Author(s) L. Ma and Y. Matsuura
Abstract We fabricate small silica glass fiber taper with a Bragg multilayer cladding for generation of subwavelength-sized beam. Simulation results suggest that silica Bragg fiber taper generate a beam spot with the size half of working wavelength due to strong confinement of the multilayer cladding. In experiment, tapered fibers with 1.1 µm cores and 0.9 µm mode field diameters for 850 nm laser diode are successfully fabricated by a sputtering technique. Tapers with subwavelength core for 785 nm laser radiation are now under investigation. These ultra-small core silica Bragg fiber taper devices are candidates as the mode couplers for fiber nanodevices.

8-2 Title DEVELOPMENT OF DUAL-WAVELENGTH LIGHT SOURCE FOR THz-WAVE GENERATION
Author(s) C. Ndiaye, T. Sugiyama, S. Nagano K. Suizu, and H. Ito
Abstract Tunable dual-wavelength light sources generating high-peak power pulses with narrow spectral linewidth are of great interest for a wide range of applications such as THz wave generation and so on. We have developed a dual wavelength tunable light source operating in the 1550nm window, based on intensity modulation of two tunable continuous wave lasers followed by an optical amplification system. In this paper, the characteristics of this light source are reported.

8-3 Title High-Precision Measurement of Polar Anchoring Strength using Psi Delta Hybrid aligned liquid crystal cell Method
Author(s) Y. Ohno, T. Ishinabe, T. Miyashita and T. Uchida
Abstract We devised a new measurement method: the Psi Delta Hybrid aligned liquid crystal cell (PDH) method, for the surface polar anchoring strength. We clarified that the alignment distribution of hybrid aligned liquid crystals can be determined by measuring the angular dependence of the amplitude ratios Psi and the phase differences Delta in the perpendicular direction to the alignment plane. The polar anchoring strengths measured using PDH method are constant to cell thickness, therefore, we confirmed the validity of PDH method.

8-4 Title Accurate Measurement of Viscosities of n-type Liquid Crystals using VA mode Cells
Author(s) Y. Kuratomi, T. Miyashita, T. Kishimoto T. Ishinabe and T. Uchida
Abstract Lately, n-type liquid crystals are widely used especially for large size LCDs. The key to improve the quality of moving pictures of LCDs is precise analysis of the response properties. However, there is not yet any established measurement method of viscosities of n-type liquid crystals. To measure the viscosities, we tried to apply the measurement method for p-type liquid crystals which have been proposed recently, but found there is a severe problem. In the presentation, we will show how we have solved the problem and successfully measured the viscosities.

8-5 Title Properties of Splay-to-Bend Transition Using Multi-Rubbing (MR) Method in OCB-Mode LCD
Author(s) K. Kuboki, A. Akiyama, T. Miyashita and T. Uchida
Abstract Optically compensated bend (OCB) mode liquid crystal displays (LCDs), which show fast response, require an initial transition from splay to bend alignment. We clarified that a disclination, which was formed between splay and twist alignment, acted as a nucleus of the transition. Based on these results, we devised a new method to create the nucleus by forming the disclination in an OCB cell using partial rubbing process.

8-6 Title Analysis of the surface order parameter of liquid crystal on a polymer surface using the phase transition droplet method
Author(s) O. S. Joon, K. Kuboki, T. Miyashita and T. Uchida
Abstract We have investigated the relationship between the contact angle cosƒ¦ of a phase transition droplet and the surface order parameter Ss of the LC, and found that there exist a linear relationship between them. We have also found that a slight birefringence of LC was observed even at the isotropic temperature, which indicates ordered LC layer exist on the PIs surface. On the other hand, in case of the other alignment layer, such as PVA, the birefringence did not observed at the isotropic temperature and the relationship between cosƒ¦ and Ss largely deviated from the straight line.

8-7 Title Proposal of SUL utilizing new soft magnetic material with negative uniaxial magnetocrystalline anisotropy
Author(s) A. Hashimoto, S. Saito and M. Takahashi
Abstract The suppression of spike noise and wide adjacent track erasure (WATE) are important technical issues in the development of a perpendicular recording medium (PRM). As a solution to both of these problems, this paper presents a type of soft magnetic underlayer (SUL) with negative uniaxial perpendicular magnetic anisotropy. CoIr with the disordered hcp structure is selected as a negative Kugrain material, and c-plane- oriented CoIr films with various Ir contents are prepared for experimental evaluation. A PRM fabricated using the CoIr SUL is confirmed to display substantially lower spike noise and WATE compared to conventional structures.

8-8 Title Waveguide for wide band terahertz transmission
Author(s) Yoshie Ohta, Tomoyu Yamashita and Hiromasa Ito
Abstract Recently there are some studies on waveguides in the terahertz (THz) band such as stainless wire, dielectric ribbons and photonic crystal fiber, and so on. However, they are not flexible or long length waveguide. We demonstrated ultra wideband THz-wave transmission through flexible inner silver-coated hollow fiber using widely tunable THz-wave generator. The inner diameter of 304mm long silver-coated hollow fiber was 1mm. THz-wave transmission in 1-15THz was almost uniform.

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Session 11: Semiconductor Devices I

11-1 Title Fabrication of FBAR Filter for Wireless Communication
Author(s) Y. Aota, S. Tanifuji, Y. Sakyu, H. Oguma, S. Kameda, H. Nakase, T. Takagi and K. Tsubouchi
Abstract The demand of high data rate wireless transmission is increasing@and the 5-GHz band wireless local area network (WLAN) is expected to achieve high data rate transmissions of more than 100Mbps. In the WLAN system, the radio frequency (RF) filter is a key device.@For the RF filter, we employ a film bulk acoustic resonator (FBAR) filter. The FBAR filter has better cut-off characteristic, smaller insertion loss and smaller size than the other RF filters such as surface acoustic wave (SAW) filters and dielectric filters. Therefore the FBAR filter is the most suitable filter for the WLAN system.

11-2 Title An Object Extraction CMOS Image Sensor with 12-bit Column-Parallel ADCs and ALUs
Author(s) T. Tate, H. Kanto, Y. Motohashi, T. Kubo, S. Sugawa, K. Kotani and T. Ohmi
Abstract The technology of object categorization is highly demanded in various applications, such as, human recognition, scene segmentation, monitoring FA/ITS, image database construction. However, it is difficult to realize the object categorization from the frame image. The fundamental technology for a high quality and high functionality CMOS image sensor has been reported. The CMOS image sensor having the capabilities of the 12bit column-parallel AD conversion, the object categorization pre-processing at every sub- frame images and the high quality frame image output is developed. The image sensor can be utilized in various image processing applications.

11-3 Title A Novel Bitline Direct Sense Circuit that uses a Feedback System for High-Speed Flash Memory
Author(s) T. Kadowaki, H. Nakamura, H. Sakuraba and F. Masuoka
Abstract In this paper, we propose a novel bitline direct sense circuit for high-speed Flash memory. Our proposed sense circuit controls the drivability of the bitline charging transistor by using a feedback system. This allows us to obtain high-speed bitline charging and readout. Despite an increase in circuit complexity, our proposed sense circuit produces a negligible increase in chip size. We also analyzed the possibility of oscillations in our feedback system and showed that our proposed sense circuit can operate stably. Therefore, our proposed sense circuit can realize high speeds and stable read operations for Flash memory.

11-4 Title Performance Analysis of Variant X-tree Clock Distribution Networks
Author(s) X. Zhang, X. Jiang and S. Horiguchi
Abstract Variant X-Tree is a class of novel non-orthogonal clock distribution networks (CDNs) proposed recently based on the idea of efficient X- Architecture wiring within VLSI chips. In this paper, we first study the layout features of a variant X-Tree CDN, we then propose closed- form statistical models for evaluating the skew and delay of the CDN. The comparison between the theoretical results and the simulation results indicates that the proposed statistical models can be used to efficiently and rapidly evaluate the performance of the variant X-Tree CDNs.

11-5 Title A Study of Nanoscale Surrounding-Gate-Transistor
Author(s) T. Hidaka, H. Amikawa, H. Nakamura, H. Sakuraba and F. Masuoka
Abstract In this paper, we demonstrate that the vertical silicon pillar for Surrounding Gate Transistor (SGT) can be fabricated by using Electron Cyclotron Resonance (ECR) plasma etching with precise control of O2 flow rate in Cl2 / O2 mixtures. As the percentage of O2 is increased above 10%, the subtrench depth decreases gradually and approaches zero. However, as the percentage of O2 is increased further more, ggrassh surrounding the vertical silicon pillar are formed. The results show that an optimal condition of the O2 percentage for successful silicon pillar fabrication is at 10%.

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Session 14: Storage Devices

14-1 Title Pt Content Dependence of Magnetic Properties of CoPt/Ru Patterned Films
Author(s) K. Mitsuzuka, T. Shimatsu, N. Kikuchi, O. Kitakami and H. Muraoka
Abstract The magnetic properties of dot arrays made of CoPt/Ru perpendicular films were examined as a function of Pt content. The remanence coercivity, Hr, for CoPt dot arrays decreased as the Pt content decreased due to the reduction of effective magnetic anisotropy. The value of E0/kBT (kB is the Boltzmann constant and T is the absolute temperature) reduced as the Pt content decreased. However, E0/kBT still had a high of 440 even at 14 at%Pt content. We successfully demonstrated the reduction of Hr on reducing the Pt content, whilst simultaneously maintaining a high thermal stability.

14-2 Title Magnetic properties and Recording performances for (Co-Pt)-SiO2/Co-SiO2 Hard/Soft-Stacked Granular Perpendicular Media
Author(s) Y. Inaba, T. Shimatsu, O. Kitakami and H. Muraoka
Abstract The magnetic properties and recording performance of hard/soft- stacked media consisting of a magnetically hard 9nm-thick (Co-Pt)- SiO2 layer underneath a thin (2-3nm) soft granular layer were studied. The use of a Co-SiO2 soft layer, which has the highest saturation magnetization of the soft layer, <Mssoft>, in the present study, was very effective at improving the recording resolution, D50. The reduction of remanence coercivity, Hr, was achieved by controlling the interfacial exchange coupling, moreover, a high- <Mssoft> enhanced the Hr reduction. The Hr reduction improved recording writability without degrading D50, the signal to medium noise ratio, and thermal stability.

14-3 Title Magnetization reversal in the positive-/negative-Ku stacked ECC media
Author(s) N. Itagaki, S. Saito, A. Hashimoto and M. Takahashi
Abstract Much attention has been paid for exchange coupled composite (ECC) media consist of grains with magnetically hard and soft parts surrounded by some oxide boundaries. According to R. H. Victrafs first proposal on ECC media, thermal stability is kept by the hard part, besides, switching field of hard part is reduced. However, in this media, spin-twisted structure, which assists switching, is hardly formed in the hard part. Therefore in this presentation, we introduce the unique newly material, the hcp disordered Co-Ir alloy with negative uniaxial magnetic anisotropy, and propose the ECC media using this new CoIr-SiO2 granular film.

14-4 Title Current Induced Magnetization Switching amd CPP-GMR in 30 nm diameter Spin Values
Author(s) S. Isogami, M. Tsunoda and M. Takahashi
Abstract It is well known that CIMS is a promising technique to realize high density MRAM from a viewpoint of power consumption. In order to reduce the operating current in such new devices, smaller spin valve is indispensable. In this study, we have newly developed EB assisted CVD hard mask method. CIMS observation was demonstrated in CPP-GMR spin valves with nominal size of 30-80 nm in diameter fabricated using EB assisted CVD hard masks. Then we considered size effect on the CIMS phenomena.

14-5 Title Effect of axial ratio on magnetism of bct and fct Fe-N
Author(s) K. Sunaga
Abstract The effect of axial ratio and atomic volume on magnetism of bct and fct Fe-N was examined. In both cases of bct and fct Fe-N, magnetic moment increases with increasing atomic volume. In the case of bct Fe-N, the J does not change against both atomic volume and axial ratio. On the other hand, in the case of fct Fe-N, J increases with increasing atomic volume and slightly decreases with increasing axial ratio. We can expect to further enhance magnetic moment with relatively high Tc, in the intermediate state of bct and fct Fe-N.

14-6 Title Magnetic Properties to Optimize the Ku2 Effect in Perpendicular Recording Media
Author(s) H. Sato, T. Shimatsu, O. Kitakami and H. Muraoka
Abstract We calculated the optimal values of the first and second order uniaxial magnetic anisotropy energy terms, Ku1 and Ku2, for thermal stability and writability in perpendicular media which utilize the Ku2 effect. The magnetic energy barrier ΔE for the remanent state with demagnetizing field 4πMs was calculated for various Ku1 and Ku2 values, and we obtained the grain volume, Vgrain, to satisfy ΔEVgrain, /kT=60 for thermal stability (k is the Boltzmann constant, and T the absolute temperature). Moreover, the switching field was calculated assuming a saturation field less than 16 kOe for good writability.

14-7 Title Alternate Monatic Layered Fe-Co Superlattice with Artificial Structure and its Application
Author(s) I. C. Chu, G. Tottori, M. Doi and M. Sahashi
Abstract It is an important criterion of program correctness that a program accesses resources in a valid manner. For example, a file that has been opened should be eventually closed, and some methods of an object must be invoked in a specific order. So far, most of the methods to verify this kind of property have been proposed in rather specific contexts (like studies of memory management and verification of lock primitives). We formalize a general problem of verifying resource usages as resource usage verification in lambda calculus including resources and exceptions, and proposed a type-based method to solve the resource usage verification problem.

14-8 Title Preparation and application of Air-stable Fe nanoparticles
Author(s) H. Yang and M. Takahashi
Abstract Superparamagnetic Fe nanoparticles assemblies with high saturation magnetization (Ms) can realize high susceptibility and permeability and thus become good candidates for high-frequence magnetic materials. But metallic Fe nanoparticles are highly sensitive to oxidation in air, which has traditionally made Fe nanoparticles difficult to study and inconvenient for practical applications. To improve the stability of Fe nanoparticles, core-shell structures such as Fe/SiO2, Fe/Pt, and Fe/Au have been tried. Magnetic measurement revealed that the Ms was over 180 emu/g at room temperature. Time-dependent magnetization showed that the magnetic moment of Fe/Pt and Fe/Au core-shell nanoparticles, had a decrease of less than 5 % over 6 hours.

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Session 19: Semiconductor Devices II

19-1 Title Si-MOSFET Class-B Pushpull Amplifier For Wireless
Author(s) K. Shimoyama, S. Kameda, H. Nakase, T. Takagi and K. Tsubouchi
Abstract We have already proposed a silicon (Si) radio frequency (RF) Class-B complementary push-pull power amplifier (PA) using 0.35μm Si complementary metal oxide semiconductor field effect transistors (CMOS) multipurpose process for third generation cellular phone system. In this paper, we propose a Si RF Class-B push-pull PA for IEEE 802.11a wireless local area network (LAN) employing 0.18μm Si-CMOS process. Using the Agilent Advanced Design System (ADS) simulator, we have evaluated the output power (Pout) and power-added efficiency (PAE) of the proposed power amplifier.

19-2 Title Strain Relaxation during Si1-x-yGexCy Epitaxial Growth on Si(100)
Author(s) K. Kim, M. Sakuraba and J. Murota
Abstract On strain relaxation during Si1-x-y GexCy epitaxial growth on Si(100) using an ultraclean hot-wall low- pressure chemical vapor deposition at 500 oC, carbon doping effect has been investigated. The depth profile of the strain in Si1-x-yGexCy films is measured by X-ray diffraction and Raman scattering spectroscopy combined with wet etching technique. It is confirmed that the strain relaxation of Si1-xGex film (x=0.45) occurs uniformly at every depth from the surface to the heterointerface. On the other hand, the strain relaxation occurs partially in the surface part of Si1-x-yGexCy films (x=0.45, y=0.016), although the bottom part near the heterointerface is still strained.

19-3 Title Strained Si/Si1-xGex/Si(100) Heterostructure Formed by Stripe-Shape Patterning
Author(s) J. Uhm, M. Sakuraba and J. Murota
Abstract In stripe patterned Si/Si1-xGex/Si(100) heterostructure, strain control of the capping Si and Si1- xGex layers has been investigated. The Raman scattering results indicate that strain relaxation in the Si1-xGex layer and introduction of tensile strain into the capping Si layer are induced by the stripe pattern formation. The degree of strain relaxation in the Si1-xGex layer is strongly dependent on the stripe width, the capping Si layer thickness, and the Si1-xGex layer thickness. The resistivity shows an increase of electron and hole conductivity for the tensile strained capping Si layer.

19-4 Title Preparation and Electrical Properties of Ultrathin Stacked Si3N4/High-k Dielectric Pr3Si6N11 Films grown in Radical Reaction Based MOCVD Systems
Author(s) H. Wakamatsu, M. Higuchi, I. Takahashi, A. Teramoto and T. Ohmi
Abstract We developed ultrathin stacked Si3N4/High-k dielectric Pr3Si6N11 gate dielectrics suitable for the advanced metal-insulator-semiconductor (MIS) devices. The Pr3Si6N11 was prepared by a newly developed radical reaction based metal-organic chemical vapor deposition (MOCVD) on the ultrathin Si3N 4 interfacial layer. Since the stacked High-k dielectrics do not contain large amount of H* and N2* radical damage defects, we could perform low-temperature high- k dielectric integration process without any additional interfacial layer formation in the Si substrate. We achieved low capacitance equivalent oxide thickness (CET) and low leakage current density that are acceptable for the ultrathin gate dielectrics for sub-100nm gate length MIS transistors.

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