Preliminary experiments on non-destructive quantitative analysis of water vapor density in halogen lamps have been carried out. A working curve showing a relation between absorbance and water vapor density was successfully obtained by using frequency-stabilized InGaAsP/InP semiconductor laser spectrometric system.

The paper discusses the possibility of building semiconductor lasers whose wavelength stays nearly constant with ambient temperature variation. Several factors affecting the lasing wavelength change with temperature variation in both distributed feedback lasers and Fabry-Perot lasers are addressed and the optimum design of bandgap temperature dependence for the active layer material is discussed. It is pointed out that the most important challenge we face in building temperature-insensitive wavelength lasers is the development of a temperature-insensitive bandgap material for the active layer. Based on published data, it is speculated that such a laser could be developed using a Hg1-xCdxTe/CdTe double heterostructure. Although no data is available yet, we expect a Ga1-xInxAs1-yBiy III-V alloy semiconductor can be used for this purpose. Recently reported T1xIn1-x-yGayP III-V alloy semiconductor might be another promising candidate. Such lasers will greatly advance applications of WDM (Wavelength-Division-Multiplexing) technology to optical fiber communication systems and contribute to network innovations.

Mechanism of the noise generation caused by the optical feedback in semiconductor laser was experimentally determined. Two types of the mode competition phenomena were confirmed to be the generating mechanisms. Applicability of the self-sustained pulsation to be a noise reduction method was also discussed.

We discuss fabrication of InGaAs quantum dot structures using the self-assembling growth technique with the Stranski-Krastanow growth mode in MOCVD, including optical ploperties of the nano-structures. The formation process of the quantum dot islands was clarified by observing the samples grown under various conditions with an atomic force microscope. A trial for self-alignment of the quantum dots was also investigated. On the basis of these results, as the first step toward the ultimate semiconductor lasers in which both electrons and photons are fully quantized, a vertical microcavity InGaAs/GaAs quantum dot laser was demonstrated. Finally a perspective of the quantum dot lasers is discussed, including the bottleneck issues and the impact of the quantum dot structures for reducing threshold current in wide bandgap lasers such as GaN lasers.

We report on the formation technique and the first observation of visible light emission from silicon nanoparticles (<10nm) embedded in CaF22 Iayers grown on Si(111) substrates by using codeposition of Si and CaF2. It is shown that the size and density of silicon particles embedded in the CaF2 layer can be controlled by varying the substrate temperature and the evaporation rates of CaF2 and Si. The photoluminescence (PL) spectra of Si nanoparticles embedded in CaF2 thin films were investigated. The blue or green light emissions obtained using a He-Cd laser (λ=325nm) could be seen with the naked eye even at room temperature for the first time. It is shown that the PL intensity strongly depends on growth conditions such as the Si:CaF2 flux ratio and the growth temperature. The PL spectra were also changed by in situ annealing process. These phenomena can be explained qualitatively by the quantum size effect of Si nanoparticles embedded in CaF2 barriers.

The mesh-connected computers with hyperbus broadcasting are an extension of the mesh-connected computers with multiple broadcasting. Instead of using local buses, we use global buses to connect processors. Such a strategy efficiently reduces the time complexity of the semigroup problem from O(N) to O(log N). Also, the matrix multiplication and the transitive closure problems are solved in O(log N) and O(log2 N) time, respectively. Then, based on these operations, several interesting problems such as the connected recognition problem, the articulation problem, the dominator problem, the bridge problem, the sorting problem, the minimum spanning tree problem and the bipartite graph recognition problem can be solved in the order of polylogarithmic time.

Copper strips plated with Sn-Pb eutectic solder were hot pressure-bonded to gold thin-film wiring. It was proven that a Au-Sn alloy forms at the interconnection between the gold thin film and the copper strip, but that there is virtually no Pb present in the interconnection. Au, Sn, and Pb were observed on the surfaces of the copper strips and the gold thin film outside of the connection area.

One of the important properties of multihop network is the mean internodal distance to evaluate the transmission delay, and the connective semi-random network achieves smaller mean internodal distance than other networks. However, the results are shown only by computer simulation and no theoretical analysis is investigated. Moreover, the network connective probability of the connective semi-random network is relatively small. In this paper, we propose the restricted connective semi-random network whose network connective probability is larger than that of the conventional connective semi-random network. And we theoretically analyze the mean internodal distance and the network connective probability of these two networks. It is shown that if the restriction is loose, the mean internodal distance of our model is almost the same as that of the conventional model, whereas the network connective probability of our model is larger than that of the conventional model. Moreover, the theoretical analyzed results of the mean internodal distance agree well with the simulated results in the conventional model and our model with small restriction.

There have been semantics for logic programs as sets of definite clauses over sequence domains in [2],[6]. The sequence of substitutions caused by resolutions for logic programs can be captured by a fixpoint of a functional [3],[16]. In [15], a functional is regarded as a behaviour of a dataflow network, the semantics over sequence domains induces dataflow computing for logic programs. Also it may provide a transformation of logic programs to functional programs[16]. Motivated by dataflow computing constructions for logic programming, this paper deals with fixpoint semantics over sequence domains for logic programs with equations and negations. A transformation, representing deductions caused by resolutions and narrowings, is associated with a logic program with equations, modified from the operator in [18], so that it may be represented by a continuous functional over a sequence domain, and its least fixpoint is well-defined. An explicit construction of such a continuous functional of sequence variables is necessary for dataflow computing, and we should prove that the functional of sequence variables can exactly represent the transformation concerned with sets. For a general logic program, a functional is constructed over a sequence domain so that it may reflect a consistency-preserving renewal function for the pair of atom sets on the basis of the 3-valued logic approach as in [7], and [11]. It is a problem to construct the domain for the functional representing a generation of atom sets interpreted as true and negation as failure in the generation, for general logic programs. The functional is monotonic over a complete partial order and its least fixpoint is well-defined, although the least fixpoint is not always obtained by the limit of finite computing, because of the functional being not necessarily continuous.

The most troublesome problem in automated X-ray mask inspection is how to exactly determine the threshold level for extracting the pattern portions of each scanning electron microscopic (SEM) image. An exact determination is difficult because the histogram shows, in most cases, a complicated multi-modal pattern and the true threshold level often varies with each successive image. This paper presents a novel thresholding approach for segmenting SEM images of X-ray masks. In this approach, the shape of the histogram of each image is iteratively analyzed until a threshold value minimizing the cost of the correspondence with a reference histogram and satisfying criteria for determining thresholds is obtained. This new approach is used in an automated inspection system. When the input image resolution is set to 0.05µm/pixel, experiments confirm 0.1µm defects are unfailingly detected.

We propose burst based bandwidth reservation method called FRP (Fast Reservation Protocol) in ATM LAN with general topology, and evaluate its performance. In FRP, the bandwidth is allocated on each link on burst basis, not on call basis. This enables an effective use of network resources when it is applied to highly bursty traffic, which can be typically found in data communications. The problem of FRP is that VCs traversing the different number of links experience different blocking probabilities as can be found in the conventional circuit-switching networks. In this paper, we treat a fairness issue in FRP-based ATM local area networks. The Max-Min flow control is adopted as the fair bandwidth allocation method to accomplish the fairness in the throughput. However, the original Max-Min flow control works in a centralized fashion, which is not desirable in the FRP-based ATM LAN. We therefore propose a "semi"-distributed Max-Min flow control suitable to FRP, in which each switch maintains its own local information about bandwidth usage of the connected links. Through simulation experiments, we show that the proposed semi-distributed Max-Min flow control can achieve the fairness among VCs as the original Max-Min flow control when the propagation delays are not large and the number of VCs is not so much.

The scaling laws between the design rules and the smallest sizes and numbers of particles capable of causing pattern defects and scrapping dies in semiconductor device manufacturing are described. Simulation with electromagnetic waveguide model indicates the possibility that particles, the sizes of which are of comparable order or even smaller than the wavelength of the lithography irradiation sources, are capable of causing pattern defects. For example, in the future 0.25 µm-design-rule era, the critical sizes of Si, Al, and SiO2 particles are simulated as 120 nm 120 nm, 120 nm 120 nm, and 560 nm 560 nm, respectively, in the case of 0.7 µm-thick chemically-amplified positive photoresist with 47 nm-thick top anti-reflective coating films. Future giga-scale integration era is also predicted.

A new electron-beam wafer inspection system has been developed. The system has a resolution of 5 nm or better, and is applicable to quarter-micron devices such as 256 Mbit DRAMs. The most remarkable feature of this system is that a specimen stage is built in the objective lens and allows a working distance (WD) of 0. "WD=0"minimizes the effect of lens aberrations, and maximizes the resolving power. Innovative designs to achieve WD=0 are as follows: (1)A large objective lens of 730-mm width 730-mm depth 620-mm height that serves as a specimen chamber, has been developed. (2)A hollow specimen stage made of non-magnetic materials has been developed.It allows the lower pole piece and magnetic coile of the objective lens inside it. (3)Acoustic motors made of non-magnetic materials are em-ployed for use in vacuum.

A new yield prediction model has been developed, which can successfully describe the actual chip fabrication yield. It basically consists of modeling of particles deposited on wafer surface, considering the change in their size and spatial distribution due to the subsequent processing steps and a new concept of virtual line width in pattern layouts. It is confirmed that this yield prediction model serves as an effective navigator for improvement/optimization of fabrication lines such as pointing out the process step/equipments to be modified for yield improvements.

We studied effects of 50-200-keV electrons on semiconductor devices using BEASTLI (backscattered electron assisting LSI inspection) method. When irradiating semiconduc-tor devices with such high-energy electrons, we have to note two phenomena. The first is surface charging and the second is device damage. In our study of surface charging, we found that a net positive charge was formed on the device surface. The positive surface charges do not cause serious influence for observation so that we can inspect wafers without problems. The positive surface charging may be brought about because most incident electrons penetrate the device layer and reach the conducting substrate of the semiconductor device. For the device damage, we studied MOS devices which were sensitive to electron-beam irradiation. By applying a 400- annealing to electron-beam irradiated MOS devices, we could restore the initial characteris-tics of MOS devices. However, in order to recover hot-carrier degradation due to neutral traps, we had to apply a 900- annealing to the electron-beam irradiated MOS devices. Thus, BEASTLI could be successfully used by providing an apporopri-ate annealing to the electron-beam irradiated MOS devices.

ElectroStatic Discharge (ESD) testing of integrated circuits subjects circuit elements to very high currents for short periods of time. A modified Transmission Line Pulse (TLP) measurement system for characterizing transistors and other circuit elements under high currents for ESD performance prediction and understanding is presented which can both stress devices and measure leakage. For the TLP system to yield useful information test structures are needed which vary the important design parameters for the circuit elements. Guidelines for transistor test structure design for use with the system are presented and demonstrated for PMOS transistors.

External modulators, which have smaller chirping characteristics than laser diode direct modulation, are desired for high-speed and long-distance optical fiber communication systems. This paper reviews semiconductor and Ti:LiNbO3 guided-wave high-speed optical modulators. Since several effects exist for semiconductor materials, various kinds of semiconductor optical modulators have been investigated. Among these, absorption type intensity modulators based on Franz-Keldysh effect in bulk materials and quantum confined stark effect in multiple quantum well materials, are promising because of compactness, low drive voltage nature and integration ease with DFB lasers. Recent progress on semiconductor absorption modulators and DFB-LD integrated semiconductor modulators is discussed with emphasis on a novel fabrication method using selective area growth by MOVPE (Metal Organic Vapor Phase Epitaxy). The Ti:LiNbO3 optical modulators are also important, due to the advantage of superior chirping characteristics and wide bandwidth. Since the Ti:LiNbO3 optical modulator has low propagation loss and low conductor loss natures for optical waves and microwaves, respectively, the traveling-wave electrode configuration is suitable for high-speed operation. Here, broadband Ti:LiNbO3 optical modulators are discussed with emphasis on traveling-wave electrode design.

If a general Petri net N = (S, T, F, Mo) is transition-live under Mo, it is evident that each maximal structural deadlock SDL(D) in N as well as each minimal structural deadlock MSDL (ND) in each D is also transition-live under Mo. However, since the converse of the latter of the above is not always true, it is important to obtain the conditions for this converse to be true if we want to have a useful necessary and sufficient "initial-marking-based" or "structural" liveness condition for N. Up to now, usefull and well-known structural or initial-marking-based necessary and sufficient liveness conditions of Petri nets have only been those of an asymmetric choice (AC) net and its subclasses such as an EFC net, an FC net, an FCF net, MG, and SM. However, all the above subclasses are activated only by real or virtual deadlock-trap properties which are local liveness for each minimal deadlocks; in other words, the above topics of this paper are unconditionally satisfied in those subclasses because of their special structure of nets. In this paper, a necessary and sufficient structural liveness condition for a general Petri net N with globally structural live minimal structural deadlocks is presented as follows: The next () or () is satisfied. () N has no SDL D. () If N has at least one SDL D, () or () is satisfied under the condition that each MSDL ND in N is transition-live under Mo. () N has no singular MSDL (α) (i.e., (α-) and (α-)). () If N has at least one singular MSDL (α-)((α-), resp.), every semi-MDSL ()((), resp.) NDS = (SDS, TDS, FDS, MoDS with respect to each singular MSDL (α-)((α-), resp.), is transition-live under the MoDS under the condition of "the condition (**)", where the locally structural liveness for this NDS means (1) or (2)((3), resp.) of Lemma 4-4 and "the condition (**)" is defined in Lemma 4-7 of this paper. The relationship between the above results and the liveness problem for N is also shown.

Conceptual graph formalism is a knowledge representation language in AI based on a graphical form of logic. Although logic is the basis of the conceptual graph theory, there is a strongly felt absence of a formal treatment of conceptual graphs as a logic programming language. In this paper, we develop the notion of a conceptual graph program as a kind of graph-based order-sorted logic program. First, we define the syntax of the conceptual graph program by specifying its major syntactic elements. Then, we develop a kind of model theoretic semantics and fixpoint semantics of the conceptual graph program. Finally, we show that the two types of semantics coincide for the conceptual graph programs.

A low contact resistivity of 4.410-7 Ωcm2 for AlGaAs/GaAs HBTs was realized using Pt/Ti/Pt/Au base metal and a 81019 cm-3 highly-doped base. A high fmax of 170 GHz was achieved by reducing a base resistance. The formation of oxide-free interface between an AlGaAs graded base and Pt-based metal was demonstrated with Auger electron spectroscopy. The optimization of the growth condition conquered the rapid current-induced degradation in the highly Be-doped HBTs. An extremely wide bandwidth of 40 GHz was attained by a Darlington feeback amplifier fabricated using these high-fmax HBTs. These properties indicate that the application of AlGaAs/GaAs HBTs can be expected to extend to future ultrahigh-speed optical transmission systems.