Junction leakage current of trench isolation devices is strongly influenced by trench configuration. The origin of the leakage current is the mechanical stress that is generated by the differential thermal expansion between the Si substrate and the SiO2 filled isolation trench during the isolation forming process. A two-dimensional mechanical stress simulation was used to analyze trench-isolated devices. The simulated distribution and magnitude of stress were found to agree with Raman spectroscopic measurements of actual devices. The stress in the deeper regions between deep trenches is likely to increase greatly as the size of devices diminishes, so it is important to reduce this stress and thus suppress junction leakage current.

A new kind of optical local area network (LAN), using a demand assign wavelength division multiple access (DA-WDMA) scheme, has been proposed. The proposed LAN consists of two parts; an ordinary standardized LAN and an overlaid network using wavelength division (WD) channels. The proposed network can provide bit-rate independent communication channels on the ordinary LAN without limiting the capacities for the other channels. It also exhibits upgrade possibilities from present standardized networks. An access controller, which consists of software in addition to the ordinary LAN controller, a digital signal processor (DSP) etc., was developed for DA-WDMA control. The network node operation has been demonstrated using guided-wave acousto-optic (AO) mode converters as a tunable wavelength add-drop multiplexer (ADM).

To realize a high performance optical subscriber network a route reconnect switch is desired which has bistability, polarization and wavelength independence and compactness. This paper proposes an electrocapillarity optical (ECO) switch, in which a micro-mirror formed by a mercury droplet is driven by electrocapillarity. This switch has a potential for use in bistable waveguide matrix switches, which are suitable for route reconnection in the optical subscriber network. A theoretical model is presented that the driving force of the electrocapillarity originates in an electrically induced gradient in the surface tension of the mercury-electrolyte interface where an electrical double layer is formed. The experimentally obtained relation between the flow velocity of a mercury droplet and the electric current in an electrocapillary system is well described by this model. A prototype of the ECO switch is made using a resin molded single-mode fiber with a slit sawed in it in which a electrocapillary system is made. Optical switching is demonstrated and possible improvements in switching performance are discussed.

In order to achieve an efficient and reliable prediction of device performance by numerical device simulation, a discretization mesh must be generated with an adequate, but not redundant, density of mesh points. However, manual mesh optimization requires user's trial and error. This task annoys the user considerably, especially when the device operation is not well known, or the required mesh-point density strongly depends on the bias condition, or else the manipulation of the mesh is difficult as is expected in 3D. Since these situations often happen in designing advanced VLSI devices, it is highly desirable to automatically optimize the mesh. Adaptive meshing techniques realize automatic optimization by refining the mesh according to the discretization error estimated from the solution. The performance of mesh optimization depends on a posteriori error indicators adopted to evaluate the discretization error. In particular, to obtain a precise terminal-current value, a reliable error indicator for the current continuity equation is necessary. In this paper, adaptive meshing based on the current continuity equation is investigated. A heuristic error indicator is proposed, and a methodology to extend a theoretical error indicator proposed for the finite element method to the requirements of device simulation is presented. The theoretical indicator is based on the energy norm of the flux-density error and is applicable to both Poisson and current continuity equations regardless of the mesh-element shape. These error indicators have been incorporated into the adaptive-mesh device-simulator HFIELDS, and their practicality is examined by MOSFET simulation. Both indicators can produce a mesh with sufficient node density in the channel region, and precise drain current values are obtained on the optimized meshes. The theoretical indicator is superior because it provides a better optimization performance, and is applicable to general mesh elements.

An efficient method which integrates a 2-D energy transport model, impact ionization model, gate current model, a discretized gate-capacitor EPROM model, and a post-processing quasi-transient programming/erase method, was developed for deep-submicron EPROM/Flash device simulation. The predicted results showed on the average better than 90% accuracy, and it took only few minutes CPU time on a SUN/SPARC2 to generate EPROM/Flash Vt shift curves.

A unified model for frequency-dependent characteristics of transconductance and output resistance is presented that incorporates the dynamics of quasi-Fermi levels. Using this model, multiple-frequency dispersion and pulse-narrowing phenomena in GaAs MESFETs are demonstrated based on the drift-diffusion transport theory and a Schockley-Read-Hall-type deep trap model, where rate equations for multiple trapping processes are analyzed self-consistently. It is shown that the complex frequency dependence is due to both spatial and temporal effects of multiple traps.

This paper describes a segment driver IC for high-quality liquid-crystal-displays (LCDs). Major design issues in the segment driver IC are a wide signal bandwidth and excessive output-offset variation both within a chip and between chips. After clarifying the trade-off relation between the signal bandwidth and the output-offset variation originated from conventional sample-and-hold (S/H) circuits, two wide-band S/H circuits with low output-offset variation have been introduced. The basic ideas for the proposed S/H circuits are to improve timing of the sampling pulses applied to MOS analog switches and to prevent channel charge injection onto a storage capacitor when the switches turn off. The inter-chip offset-cancellation technique has been also introduced by using an additional S/H circuit. Two test chips were implemented using the above S/H circuits for demonstration purposes. The intra-chip output-offset standard deviation of 9.5 mVrms with a 3dB bandwidth of 50 MHz was achieved. The inter-chip output-offset standard deviation was reduced to 5.1 mVrms by using the inter-chip offset-cancellation technique. The evaluation of picture quality of an LCD using the chips shows the applicability of the proposed approaches to displays used for multimedia applications.

This paper describes an implementation of the finite element method to examine the effects of actual lip shape on the sound radiation. A three-dimensional finite element approach by Galerkin method was used. The accuracy of the calculation of finite element method for the sound radiation was tested by comparing it with the exact solutions for a circular piston radiator on an infinite baffle. Using a set of finite element models of the vocal tract, we calculated the responses to a pure tone input and the sound fields over the frequency range of 100 Hz-7 kHz. The transfer functions are examined in detail for vowels /a/ and /i/ when the shape of the actual lips is simplified as a planeradiation surface. The effects of lip shape on the distribution of sound pressures are also shown in both the vocal tract and the surrounding space of the mouth opening.

A simulation model for arsenic diffusion in polycrystalline silicon has been developed considering dynamic dopant clustering and polysilicon grain growth kinetics tightly coupled with dopant diffusion and segregation. It was assumed that the polysilicon layer consists of column-like grains surrounded by thin grain-boundaries, so that one dimensional description is permissible for dopant diffusion. The dynamic clustering model was introduced for describing arsenic activation in polysilicon grains, considering the solubility limit increase for arsenic in a polysilicon. For a grain-growth calculation, a previous formula was modified to include a local concentration dependence. The simulation results show that these effects are significant for a high dose implantation case.

Photonic ATM switching systems with Terabit/s throughput are desirable for future broadband ISDN systems. Since electronic LSI-based ATM switching systems are planned to have the throughput of 160Gb/s, a photonic ATM switching system should take the role of the highest layer in a hybrid switching network which includes electronic LSI-based ATM switching systems as its sub-system. This report discusses the state-of-the-art photonic devices needed for a frequency-self-routing ATM photonic switching system with maximum throughput of 5Tb/s. This kind of systems seems to be a moderate system for the first phase photonic switching system with no insuperable obstacle for initiating development, even though none of the devices and technologies required have yet been developed to meet the specifications. On the contrary, for realizing further enlarged throughput as the second-phase photonic switching system, there are huge fundamental research projects still remaining for establishing the technology utilizing the spectrum broadened over 120nm and highly-dense FDM technologies based on homodyne coherent detection, if supposing a simple architecture. "Ultra devices" seem to be the photonic devices based on new tailored materials of which gain and refractive index are designed to realize ultra-wide spectrum utilization.

The demand for large-capacity photonic switching systems will increase as regular broadband ISDN (B-ISDN) spreads and full-motion video terminals replace telephones. Large-scale and economical optical fiber transmission lines have been built based on time-division (TD) multiplexing. To reduce costs, it is important to increase the channel multiplexity of both transmission and switching systems by using TD and wavelength-division (WD) or frequency-division (FD) technologies. We surveyed photonic switching systems' architecture and switching network structures. Switching can be divided into circuit or synchronous transfer mode (STM) switching, and asynchronous transfer mode (ATM) switching. A variety of photonic STM and ATM switching systems based on the two switching technologies have recently been proposed and demonstrated.

A new method for simulation of etching and deposition processes has been developed. This method is based on fundamental morphological operations derived from image and signal processing. As the material surface during simulation moves in time, the geometry either increases or decreases. If the simulation geometry is considered as a two-valued image (material or vacuum), etching and deposition processes can be simulated by means of the erosion and dilation operation. Together with a cellular material representation this method allows an accurate and stable simulation of three-dimensional arbitrary structures. Simulation results for several etching and deposition problems demonstrate accuracy and generality of our method.

It has become more important to shorten development periods of high performance computer systems and their LSIs. During debugging of computer prototypes, logic designers request very frequent LSI refabrication to change logic circuits and to add some functions in spite of their extensive logic simulation by several GFLOPS supercomputers. To meet these demands, an automated on-chip direct wiring modification system has been developed, which enables wire-cut and via-digging by a precise focused ion beam machine, and via-filling and jumper-writing by a laser CVD machine, directly on pre-redesign (original) chips. This modification system was applied to LSI reworks during the development of Hitachi large scale computers M-880 and S-3800, and contributed to shorten system debugging period by four to six months.

This paper points out that there are two types of claw free families with respect to a level of claw freeness. We formulate them as weak claw free families and strong claw free families. Then, we present sufficient conditions for each type of claw free families. (A similar result is known for weak claw free families.) They are represented as some algebraic forms of one way functions. A new example of strong claw free families is also given.

Student contradictions are the essentials of concepts and knowledge acquisition processes of a student, in the course of tutoring. This paper presents a new perspective to represent student contradictions and a student modeling architecture to capture them. The formulation of a student modeling mechanism enables flexible decision making by using information obtained from students. A nonmonotonic and inductive student model inference system HSMIS has been developed and formulated to cope with modeling contradictions, which basically embodies advanced representation power, sufficiently high adaptability and generality. The HSMIS is evaluated and compared with other representative systems in order to demonstrate its effectiveness.

The connection admission control is one of preventive traffic control in ATM networks. The one objective of connection admission control is to keep the network load moderate so as to achieve a performance objective associated with quality of services (QOS). Because the cell loss rate is more sensitive to offered load than the average queuing delay in ATM networks, QOS requirement associated with cell loss rate is considered. The connection admission control acts as one of the major roles in traffic control. The job of connection admission control is to make an acceptance decision for connection set-up request to control the network load. This paper proposed and evaluated a connection admission control method. The proposed method is suitable for real time operation even in large diversity of connection types, because the amount of calculation for connection admission control is reduced remarkably compared to conventional algorithms. Moreover, the amount of calculation for the algorithm does not increase even when the number of connection types increases. The proposed method uses probability function for the number of cells transferred from multiplexed connections and uses recursive equations in estimating cell loss rate.

A Si metal insulator semiconductor tunnel emitter transistor (Si MIS TET) which is a new type of bipolar transistor was fabricated and its electrical properties for the temperature range of 100 K - 300 K were investigated. The common emitter mode current gain obtained was 75 at 300 K and 74 at 100 K. It was confirmed by measuring the temperature dependence of the base current that the inversion base layer indeed functioned as a base of the Si MIS TET. The current gain of the Si MIS TET did not decrease at low temperature of 100 K, though the current gain of the conventional Si bipolar transistor decreases at low temperature due to the emitter bandgap narrowing in heavily doped emitter. This origin was that the carrier injection mechanism between the emitter and the base was tunneling.

A transmission data format for high-speed optical parallel interconnections is proposed and a 4-channel transmitter and receiver link module operating at up to 1.2 Gb/s per channel is demonstrated. The data format features "Group Multiplexing and Coding." In this scheme, input several tens channels are multiplexed and coded in group into reduced channels, resulting in burst-mode compatible, skew-free transmission, and low power-consumption of a link module. Experiments with fabricated modules comfirm that our data coding in multichannel optical transmission is promising for use in high-speed interconnections in information and switching systems.

This paper considers the subliminal channel, hidden in an identification scheme, for transferring signatures. We observe the direct parallelization of the Fiat-Shamir identification scheme has a subliminal channel for the transmission of the digital signature. A positive aspect of this hidden channel supplies us how to transfer signatures without secure channels. As a formulation of such application, we introduce a new notion called privately recordable signature. The privately recordable signature is generated in an interactive protocol between a signer and a verifier, and only the verifier can keep the signatures although no third adversary can record the signatures. ln this scheme, then the disclosure of the verifier's private coin turns the signer's signature into the ordinary digital signature which is verified by anybody with the singer's public key. The basic idea of our construction suggests the novel primitive that a transferring securely signatures without secret channels could be constructed using only one-way function (without trapdoor).

This paper describes the current situations and future directions of intelligent CAI researches/development in Japan. Then necessity of intelligence in CAIs/Educational systems are thought over corresponding to the model of teaching and the cognitive model of human learning like the situated learning, knowledge construction and so on. Originally, the main aims of ITSs/ICAIs are to tealize the high level environment of individual teaching/learning. So it is the most important to incorporate the intellectual function of teaching into the system. Whatever kinds of teaching purposes ITSs have, they have the quite complex structure which consists of the domain knowledge base (Expert system), student model, the tutoring knowledge base, the powerful human interface, and sophisticated inference engine with plural functions by artificial intelligence technology. In this paper, the technological and educational points of view are discussed, surveyed and summarized based on intelligent teaching functions of ITSs/ICAIs. Moreover, the meaning of new paradigm from ITSs to ILE are mentioned under the new technology of networking and multi-media.