In this paper, we propose an algorithm of O(|V|min{k,|V|,|A|}|A|) time complexity for finding all k-edge-connected components of a given digraph D=(V,A) and a positive integer k. When D is symmetric, incorporating a preprocessing reduces this time complexity to O(|A|+|V|2+|V|min{k,|V|}min{k|V|,|A|}), which is at most O(|A|+k2|V|2).

Surface reconstruction and visualization from sparse and incomplete surface data is a fundamental problem and has received growing attention in both computer vision and graphics. This paper presents a computational scheme for realistic visualization of free-formed surfaces from 3D range images. The novelty of this scheme is that by integrating computer vision and computer graphics techniques, we dynamically construct a mesh representation of the arbitrary view of the surfaces, from a view-invariant shape description obtained from 3D range images. We outline the principle of this scheme and describle the frame work of a graphical reconstruction model, we call arbitrarily oriented meshes', which is developed based on differential geometry. The experimental results on real range data of human faces are shown.

We propose a high-speed SOI bipolar transistor fabricated using bonding and thinning techniques. It is important to replace SOI area except for devices with thick SiO2 to reduce parasitic capacitance. A thin SOI film with a thin buried layer helps meet this requirement. We formed a 1-µm-thick SOI film with a 0.7-µm-thick buried layer by ion implantation before wafer bonding pulse-field-assisted bonding and selective polishing. Devices were completely isolated by thick SiO2 using a thin SOI film and the LOCOS process. We fabricated epitaxial base transistors (EBTs) on bonded SOI. Our transistors had a cutoff frequency of 32 GHz.

A speech analysis/synthesis system that relies on a time-varying Auto Regressive Moving Average (ARMA) process and the Short-Time Fourier Transform (STFT) is proposed. The narrowband components in speech are represented in the frequency domain by a set of harmonic components, while the broadband random components are represented by a time-varying ARMA process. The time-varying ARMA model has a dual function, namely, it creates a spectral envelope that fits accurately the harmonic STFT components, and provides for the spectral representation of the broadband components of speech. The proposed model essentially combines the features of waveform coders by employing the STFT and the features of traditional vocoders by incorporating an appropriately shaped noise sequence.

Fiber-optic local area networks (LANs) with Fiber Distributed Digital Interface (FDDI) protocol have come into use as backbones connecting other small LANs. This paper describes the current status of LANs, reviews a number of issues that stand in the way of further development and look at the future of LANs. Demands for wide-area networks (WANs) connecting LANs and multimedia LANs including voice and image capability has been extremely strong, spurring progress in geographical expansion and throughput increase, now over 100Mbit/s. The logical choice of transmission medium for next-generation systems is single-mode optical fiber, not only for backbone LANs but also, eventually, for floor LANs.

The subject of the paper is to propose an O(|V|+|E|) algorithm for the 3-edge-connectivity augmentation problem (UW-3-ECA) defined by "Given an undirected graph G0=(V,E), find an edge set E of minimum cardinality such that the graph (V,EE ) (denoted as G0+E ) is 3-edge-connected, where each edge of E connects distinct vertices of V." Such a set E is called a solution to the problem. Let UW-3-ECA(S) (UW-3-ECA(M), respectively) denote UW-3-ECA in which G0+E is required to be simple (G0+E may have multiple edges). Note that we can assume that G0 is simple in UW-3-ECA(S). UW-3-ECA(M) is divided into two subproblems (1) and (2) as follows: (1) finding all k-edge-connected components of a given graph for every k3, and (2) determining a minimum set of edges whose addition to G0 result in a 3-edge-connected graph. Concerning the subproblem (1), we use an O(|V|+|E|) algorithm that has already been existing. The paper proposes an O(|V|+|E|) algorithm for the subproblem (2). Combining these algorithms makes an O(|V|+|E|) algorithm for finding a solution to UW-3-ECA(M). Furthermore, it is shown that a solution E to UW-3-ECA(M) is also a solution to UW-3-ECA(S) if |V|4, partly solving an open problem UW-k-ECA(S) that is a generalization of UW-3-ECA(S).

Improvement of fatigue behavior of a fusion spliced portion on a carbon-coated fiber is achieved by recoating carbon using a thermal-CVD process with a CO2 laser as a local heat source. The fatigue parameters, so-called n-values, of 121 and 94 are obtained on the non-spliced portion and the spliced portion, respectively. Assuming a life time prediction model, these high values have been proved to have an advantage in a long-term reliability and to be sufficient in a practical submarine cable use.

This paper proposes a surveillance system concept, which includes the analysis of fiber fault factors and monitored items, the architecture for diagnosing fiber degradation and the system configuration. Fiber faults are classified into two types. One is fiber failure caused by fiber axial tensile strain and the other is fiber loss increase caused by fiber bending and the absorption of hydrogen molecules. It was found that there is an urgent need for fiber axial strain monitoring, sensitive loss monitoring operating at longer wavelengths and water sensing, in order to detect the origin and early indications of these faults before the service is affected. Moreover, an algorithm for predicting and diagnosing fiber faults based on the detected results was investigated and systematized.

Optical soliton transmissions at 10 and 20Gbit/s over 1000km with the use of erbium-doped fiber amplifiers are described in detail. For the 10Gbit/s experiment, a bit error rate (BER) of below 110-13 was obtained with 220-1 pseudorandom patterns and the power penalty was less than 0.1dB. In the 20Gbit/s experiment optical multiplexing and demultiplexing techniques were used and a BER of below 110-12 was obtained with 223-1 pseudorandom patterns under a penalty-free condition. A new technique for sending soliton pulses over ultralong distances is presented which incorporates synchronous shaping and retiming using a high speed optical modulator. Some experimental results over 1 million km at 7.210Gbit/s are described. This technique enables us to overcome the Gordon-Haus limit, the accumulation of amplified spontaneous emission (ASE), and the effect of interaction forces between adjacent solitons. It is also shown by computer runs and a simple analysis that a one hundred million km soliton transmission is possible by means of soliton transmission controls in the time and frequency domains. This means that limit-free transmission is possible.

The path diversity improvement inherent in direct sequence spread spectrum (DS/SS) signalling under multi-path propagation environments is investigated for mobile/personal radio communications systems that employ DPSK modulation. The bit error rate (BER) performance of post-demodulation selection diversity reception is theoretically analyzed in the presence of noise-only-paths in the time window for diversity combining. Results of laboratory experiments conducted to evaluate the BER performance are also presented. It is shown that the experimental results agree well with the theoretical BER.

A new capacitor over bit-line (COB) stacked capacitor memory cell was developed using a local interconnect poly-silicon layer to arrange a capacitor contact between bit-lines. This memory cell enables usable capacitor area to increase and capacitor contact hole depth to decrease. The hemispherical grain (HSG) silicon, whose effective surface area is twice that of ordinary poly-silicon, was utilized for the storage node to increase the storage capacitance without increasing the storage node height. The feasibility of achieving a 1.8 µm2 memory cell with 30 fF storage capacitance using a 7 nm-SiO2-equivalent dielectric film and a 0.5 µm-high HSG storage node has been verified for 64 MbDRAMs by a test memory device using a 0.4 µm CMOS process.

A new technique for evaluating gate oxide reliability using photon emission method has been developed. This method enables the measurements of the initial breakdown characteristics, reliability testing and failure analysis consistently. From the experimental results, followings are clarified for the first time using this technique. Failure modes in the initial characteristics have close correlation to TDDB characteristics and both characteristics correspond to the location of breakdown spot. The results suggest measures to improve the reliability of gate oxide and the existance of new failure mechanism.

Two kinds of nitrided ultrathin (510 nm) SiO2 films were formed on the silicon (100) face using rapid thermal NH3-nitridation (RTN) and rapid thermal N2O-oxynitridation (RTON) technologies. The MOS capacitors with RTN SiO2 film showed that by Fowler-Nordheim (F-N) electron injection, both electron trap density and low-field leakage increase by the NH3-nitridation. In addition, the charge-to-breakdown (QBD) value decreases owing to NH3-nitridation. By contrast, RTON SiO2 films exhibited extremely low electron trap density, almost no increase of the leakage current, and large QBD value above 200C/cm2. The oxide film composition was evaluated by secondary ion mass spectroscopy (SIMS). The chemical bonding states were also examined by Fourier transform-infrared reflection attenuated total reflectance (FT-IR ATR) and X-ray photoelectron spectroscopy (XPS) measurements. These results indicate that although a large number of nitrogen (N) atoms are incorporated by the RTN and RTON, only the RTN process generates the hydrogen-related species such as NH and SiH bounds in the film, whereas the RTON film indicates only SiN bonds in bulk SiO2. From the dielectric and physical properties of the oxide films, it is considered that the oxide wearout by high-field stress is the result of the electron trapping process, in which anomalous leakage due to trap-assisted tunneling near the injected interface rapidly increases, leading to irreversible oxide failure.

The effects of low temperature etching for sub-half micron multi-layer resist are investigated. The low temperature etching with pure O2 gas provides higher anisotropic profiles than with an additional gas such as Cl2, N2. This is caused by the difference in the formative process of the side wall protection. With pure O2 gas at 80, highly anisotropic profiles for 0.35 µm patterns can be performed while the maximum tolerable width loss is below 0.03 µm.

Phosphorus-doped amorphous or polycrystalline silicon can yield a conformal, low resistance, thermallystable plug for the high-aspect-ratio, sub-half-micron contactholes found in current development prototypes of future 64 and 256 Mega-bit DRAMs. When directly contacted to a silicide layer, however, such as WSix found in polycide gate or bit line metallization/contact structures, the outdiffusion of phosphorus from the doped-silicon layer into the silicide can occur, resulting in an increase in resistance. The characteristics of both the doped-silicon and WSix layers influence the outdiffusion. The grain size of the doped silicon appears to control diffusion at the WSix/doped-silicon interface while the transition of WSix from an as-deposited amorphous to a post-annealed polycrystalline state appears to help cause uniform phosphorus diffusion throughout the silicide film. The results of phosphorus pre-doping of the silicide to reduce the effects of outdiffusion are dependent upon the relative material volumes and interfacial areas of the layers. Due to the effectiveness of the TiN barrier layer/Ti contact layer structure used in Al-based contacts, Ti and TiN were evaluated on their ability to prevent phosphorus outdiffusion. Ti reacts easily with doped silicon and to some extent with WSix, thereby allowing phosphorus to outdiffuse through the TiSix into the overlying WSix. TiN, however, is very effective in preventing phosphorus outdiffusion and preserving polycide interface smoothness. A WSix/TiN/Ti metallization layer on an in situ-doped (ISD) silicon layer with ISD silicon-plugged contactholes yields contact resistances comparable to P+-implanted or non-implanted WSix layers on similar ISD layers/plugs for contact sizes greater than approximately 0.5 µm but for contacts of 0.4 µm or below the trend in contact resistance is lowest for the polycide with TiN barrier/Ti contact interlayers. A 20 nm-thick TiN film retains its barrier characteristics even after a 4-hour 850 anneal and is applicable to the silicide-on-doped-silicon structures of future DRAM and other ULSI devices.

The performance of copper interconnects formed by the low-kinetic-energy ion bombardment process has been investigated. The copper films formed on SiO2 by this technology under a sufficient amount of ion energy deposition exhibit perfect orientation conversion from Cu (111) to Cu (100) upon post-metallization thermal annealing. We have discovered such crystal orientation conversion is always accompanied by a giant-grain growth as large as 100 µm. The copper film resistivity decreases due to the decrease in the grain boundary scattering, when the giant-grain growth occurs in the film. The resistivity of giant-grain copper film at a room temperature is 1.76 µΩcm which is almost equal to the bulk resistivity of copper. Furthermore, a new-accelerated electromigration life-test method has been developed to evaluate copper interconnects having large electromigration resistance within a very short period of test time. The essence of the new method is the acceleration by a large-current-stress of more than 107 A/cm2 and to utilize the self heating of test interconnect for giving temperature stress. In order to avoid uncontrollable thermal runaway and resultant interconnect melting, we adopted a very efficient cooling system that immediately removes Joule heat and keeps the interconnect temperature constant. As a result, copper interconnects formed by the low-kinetic-energy ion bombardment process exhibit three orders of magnitude longer lifetime at 300 K than Al alloy interconnects.

Copper contamination behavior is studied, depending on the pH level, conductivity type P or N of a silicon substrate, and contamination method of copper. If the pH level of a copper containing solution is adjusted by using ammonia, copper atoms and ammonia molecules produce copper ion complexes. Accordingly, the amount of copper adsorption on the substrate surface is decreased. When N-type silicon substrates are contaminated by means of copper containing solutions, copper atoms on the surfaces diffuse into bulk crystal even at room temperature. But for P-type silicon substrates, copper atoms are transferred into bulk crystal only after high temperature annealing. In the case of silicon substrates contaminated by contact with metallic copper, no copper atom diffusion into bulk crystal was observed. The above mentioned copper contamination behavior can be explained by the charge transfer interaction of copper atoms with silicon substrates.

In this work, we introduce a fuzzy inference in conventional backpropagation learning algorithm, for networks of neuron like units. This procedure repeatedly adjusts the learning parameters and leads the system to converge at the earliest possible time. This technique is appropriate in a sense that optimum learning parameters are being applied in every learning cycle automatically, whereas the conventional backpropagation doesn't contain any well-defined rule regarding the proper determination of the value of learning parameters.

Gradient-based methods for the computation of the velocity from image sequences assume that the velocity field varies smoothly over image. This creates difficulties at regions where the image intensity changes abruptly such as the occluding contours or region boundaries. In this letter, we propose a method to overcome these difficulties by incorporating the information of discontinuities in image intensity into a standard local optimization method. The presented method is applied to the synthetic and real images. The results show that the velocity field computed by the proposed method is less blurred at region boundaries than that of the standard method.

Hot carrier reliability due to residual damage in the gate oxide created by synchrotron X-ray irradiation is investigated for subquarter-micrometer NMOSFETs under a wide irradiation-dose range (103,000 mJ/cm2). Although irradiation-induced interface-traps and positive charges are completely eliminated after 400 post-metalization-annealing, neutral electron traps partially remain. The effects of the residual trapa on hot-carrier degradation can be negligible when gate oxides thinner than about 5 nm are used, and it is found that there is no effect of irradiation damage on interface-trap generation due to injected hot-carriers. It is concluded that the influence of synchrotron radiation X-ray lithography on hot-carrier-induced degradation in subquarter-micrometer NMOSFETs can be negligible.