Recently, high-dose implantation and low temperature annealing have become one of the key techniques in shallow junction formation. To fabricate shallow junction in quarter-micron CMOS VLSIs, it is well known being important to evaluate the transient enhanced diffusion (TED) of implanted dopants at low temperature furnace annealing, which is caused by the damages of implantation. We have newly studied the TED phenomena by a compact empirical method. This approach has merits of simplicity and better physical intuition, because we can use only minimal parameters to describe the TED phenomena. The other purpose of this work is to evaluate two-dimensional transient enhanced diffusion focusing on phosphorus implant and furnace annealing. Firstly, we defined effective diffusivity of the TED and determined extraction procedure of the model parameters. Number of the TED model parameters is minimized to two, which describe effective enhanced diffusivity and its activation energy. The parameters have been extracted from SIMS profile data obtained from samples which range 1013-31015 cm-2 and 850-950 for phosphorus implanted dose and annealing temperature, respectively. Simulation results with the extracted transient enhanced diffusion parameters show good agreements well with the SIMS data within 2% RMS-error. Critical doses for phosphorus enhanced diffusion have been determined in 950 annealing condition. No transient enhanced diffusion is observed at 950 under the implant dose of 11013 cm-2. Also the transient enhanced diffusivity is leveled off over the dose of 11014 cm-2. It is seen that the critical dose in TED phenomena might be temperature dependent to a certain extent. We have also verified that two-dimensional effect of the TED phenomena experimentally. Two-dimensional phosphorus n- layer is chosen to verify the simulation. It was concluded that the TED has isotropic nature in phosphorus n- diffusion formation.

Directional dry etching of Tantalum is described X-ray lithography absorber patterns. Experiments are carried out using both reactive ion etching in CBrF3-based plasma and electron-cyclotron-resonance ion-stream etching in Cl2-based plasma. Ta absorber patterns with perpendicular sidewalls cannot be obtained by RIE when only CBrF3 gas is used as the etchant. While adding CH4 to CBrF3 effectively improves the undercutting of Ta patterns, it deteriorates etching stability because of the intensive deposition effect of CH4 fractions. By adding an Ar/CH4 mixture gas to CBrF3, it is possible to use RIE to fabricate 0.2-µm Ta absorber patterns with perpendicular sidewalls. ECR ion-stream etching is investigated to obtain high etching selectivity between Ta and SiO2 (etching mask)/SiN (membrane). Adding O2 to the Cl2 etchant improves undercutting without remarkably decreasing etching selectivity. Furthermore, an ECR ion-stream etching method is developed to stably etch Ta absorber patterns finer than 0.2µm. This is successfully applied to X-ray lithography mask fabrication for LSI test devices.

This paper briefly reviews recent studies on free-space photonic switches, and discusses classifications, applications and technical issues to be solved. The free-space photonic switch is a switch that uses light beam interconnections based on free-space optics instead of guided-wave optics. A feature of the free-space switch is its high-density three-dimensional structure that enables compact large-scale switches to be created. In this paper, the free-space switches are classified by their various attributes such as logical network configuration, path-establishment method, number of physical stages, signal-waveform transmission form, interconnection optics and so on. The logical network configuration (topological geometry or topology) is strongly related to the advantages of the free-space switches over the guided-wave switches. The path-establishment method (path-shifting/branching-and-gating) and the number of physical stages (single-stage/multistage) are related to physical switching characteristics. Signal-waveform transmission form (analog/digital) is related to switch application. Interconnection optics (imaging system/micro-beam system) is related to the density and volume of the switching fabric. Examples of the free-space switches (single-stage, analog multistage, digital multistage and photonic ATM switches) are described. Possible applications for analog switches are subscriber-line concentrators, inter-module connectors, and switching networks for parallel or distributed computer systems. Those for digital switches include multistage space-division switches in time-division circuit-switching or packet switching systems (including asynchronous transfer mode [ATM] switching system) for both communications switching systems and parallel/distributed computer systems. Technical issues of the free-space switches (system, device, assembly technique) must be solved before creating practical systems. In particular, the assembly technique is a key issue of the free-space switches.

A software package has been developed for simulating complex silicon and heterostructure devices in 3D. Device geometries are input with a mouse-driven geometric modeler, thus simplifying the definition of complex 3D shapes. Single components of the device are assembled through boolean operations. Tetrahedra are used for grid generation, since any plane-faced geometry can be tessellated with tetrahedra, and point densities can be adapted locally. The use of a novel octree-like data structure leads to oriented grids where desirable. Bad angles that prevent the convergence of the control volume integration scheme are eliminated mostly through topological transformations, thus avoiding the insertion of many redundant grid points. The discretized drift-diffusion equations are solved with an iterative method, using either a decoupled (or Gummel) scheme, or a fully coupled Newton scheme. Alternatively, generated grids can be submitted to a Laplace solver in order to calculate wire capacitances and resistances. Several examples of results illustrate the flexibility and effectiveness of this approach.

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.

This paper presents a new method for resolving lexical (word sense) ambiguities inherent in natural language sentences. The Sentence Analyzer (SENA) was developed to resolve such ambiguities by using constraints and example-based preferences. The ambiguities are packed into a single dependency structure, and grammatical and lexical constraints are applied to it in order to reduce the degree of ambiguity. The application of constraints is realized by a very effective constraint-satisfaction technique. Remaining ambiguities are resolved by the use of preferences calculated from an example-base, which is a set of fully parsed word-to-word dependencies acquired semi-automatically from on-line dictionaries.

In this paper, we present a new technique for the semantic analysis of sentences, including an ambiguity-packing method that generates a packed representation of individual syntactic and semantic structures. This representation is based on a dependency structure with constraints that must be satisfied in the syntax-semantics mapping phase. Complete syntax-semantics mapping is not performed until all ambiguities have been resolved, thus avoiding the combinatorial explosions that sometimes occur when unpacking locally packed ambiguities. A constraint satisfaction technique makes it possible to resolve ambiguities efficiently without unpacking. Disambiguation is the process of applying syntactic and semantic constraints to the possible candidate solutions (such as modifiees, cases, and wordsenses) and removing unsatisfactory condidates. Since several candidates often remain after applying constraints, another kind of knowledge to enable selection of the most plausible candidate solution is required. We call this new knowledge a preference. Both constraints and preferences must be applied to coordination for disambiguation. Either of them alone is insufficient for the purpose, and the interactions between them are important. We also present an algorithm for controlling the interaction between the constraints and the preferences in the disambiguation process. By allowing the preferences to control the application of the constraints, ambiguities can be efficiently resolved, thus avoiding combinatorial explosions.

In this paper, we present a unified model for dialogue understanding involving various sorts of ambiguities, such as lexical, syntactic, semantic, and plan ambiguities. This model is able to estimate and revise the most preferable interpretation of utterances as a dialogue progresses. The model's features successfully capture the dynamic nature of dialogue management. The model consists of two main portions: (1) an extension of first-order logic for maintaining multiple interpretations of ambiguous utterances in a dialogue; (2) a device which estimates and revises the most preferable interpretation from among these multiple interpretations. Since the model is logic-based, it provides a good basis for formulating a rational justification of its current interpretation, which is one of the most desirable aspects in generating helpful responses. These features (contained in our model) are extremely useful for interactive dialogue management.

A photonic inter-module connector for near-future electronic switching systems is demonstrated through the use of silica-based 88 optical switches. A small-scale switch matrix is sufficient because the near-future systems will consist of a limited number of modules. If an active module is affected by a fatal fault or accident, a stand-by module must quickly take its place. The experimental photonic inter-module connector can switch 156-Mbit/s photonic interconnections between seven subscriber-line-concentrator modules and eight circuit-switching modules.

We studied the supply and removal of oil to and from a thin groove and the consequent insertion loss, aiming at matrix optical waveguide switches that utilize optical reflection and transmission effects at the groove. A robot precisely controlled the position of the removal nozzle and the supply needle by a vision servo. The optimum position for the removal nozzle was at the entrance of the groove to a circular oil pool, and the positioning margin was 10-15µm around the optimum position. The on-off ratio of the switching light power at the optimum position was about 30dB. The removal time was proportional to the kinetic viscosity of the oil, and the optimum height of the removal nozzle was independent of the kinetic viscosity of the oil. An analysis of the insertion loss revealed that the main factor in the loss at the reflection is the tilt of the groove wall.

This paper presents a design of low-power CMOS OTA-C filters suitable for on-chip integration of advanced monolithic system LSIs that have analog I/O and digital signal processing capability. First, we discuss the distortion of MOS cross-coupled circuits which have a quite low distortion when the MOS FETs have the square law characteristics. Considering the nonidealities of MOS FET, however, we find that the third harmonic component of signal dominates the total harmonic distortion (THD) of the cross-coupled pair circuit. We propose a new architecture to reduce the 3rd harmonic component. Low distortion operational transconductance amplifiers (OTA) which consist of the proposed low distortion cross-coupled pair are applied to the realization of OTA-Capacitor filters. The SPICE simulation shows that the THD of the filter is 0.0047% and the power dissipation is 22.6 mW.

The Synchronous Optical Network (SONET) technology offers technical possibilities to build high speed transport networks and enables the operator to react quickly to the customers' capacity requirements. Furthermore the advanced SONET equipment, with standardized control and operation features, provides opportunities for new services, such as broadband services, and cost-effective ways to enhance existing services, such as network survivability improvement. But SONET technology can also create a certain degree of complexity in building cost-efficient network, especially in case of SONET Self-Healing Ring (SHR). It is a challenge for network planner to find an effective way to select the most economical SONET ring, or combination of rings, for given demands between a set of nodes that are supposed to be connected in a certain type of ring configuration. Three types of ring are standard today: path unidirectional, 2-fiber line protection bidirectional and 4-fiber line protection bidirectional. For a given network, the choosing of ring architecture based on economical considerations involves two major factors. They are capacity requirement and equipment cost. Capacity requirements of different SONET ring architectures depend upon different conditions. While facility line rate, which is a key factor in deciding what kind self-healing ring can be deployed economically on these requirements. Routing decisions play a key role in deciding the ring capacities required, especially for bidirectional rings. In the paper, we will make the economic study on how SONET SHR architecture works out with a variety of demand patterns, to find criteria for ring selection. We first present two efficient demand loading algorithms for BSHR capacity calculation, and then analyze the results from their application on a variety of demand patterns. The economic study for SONET SHR networks based on different architectures are also discussed.

An analytical method is developed to determine the critical value of the control parameter of a dynamical system above which chaos is initiated. An initial value problem for a dynamical system is shown to be solved with the aid of a continued fraction expansion which converges very rapidly. The result is confirmed by numerical experiments.

The power transfer characteristics of a symmetric nonlinear directional coupler (NLDC) are analyzed rigorously using the beam propagation method based on the finite difference scheme. The NLDC consists of two linear waveguides separated by a Kerr-like nonlinear gap layer. The change of nonlinear refractive index along the coupler is precisely evaluated by making use of the second-order iteration procedure with respect to a small propagation length. For the incidence of TE0 mode of the isolated linear waveguide, the highly accurate numerical results are obtained for the behavior of power transfer, and the coupling length and critical power for optical switching. The dependencies of the coupling length and critical power on the width of the gap layer and the input power levels are discussed, compared with those predicted by the coupled-mode approximations.

For IF direct sampling phase detection method (IFSM) which realizes the arithmetical operations with digital filters by direct A/D (Analog to Digital) conversion of IF (Intermediate Frequency) signal, the method to eliminate DC offset is proposed and developed by using the gate array. A principle of the proposed method and the results of the measurement are shown.

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.

In this paper an identity-based non-interactive key sharing scheme (IDNIKS) is proposed in order to realize the original concept of identity-based cryptosystem, of which secure realization scheme has not been proposed. First the necessary conditions for secure realization of IDNIKS are considered from two different poinrts of view: (i) the possibility to share a common-key non-interactively and (ii) the security for entity's conspiracy. Then a new non-interactive key sharing scheme is proposed, of which security depends on the difficulty of factoring. The most important contribution is to have succeeded in obtaining any entity's secret information as an exponent of the obtainer's identity information. The security of IDNIKS for entity's conspiracy is also considered in details.

In this paper, we investigate the knowledge complexity of interactive proof systems and show that (1) under the blackbox simulation, if a language L has a bounded move public coin interactive proof system with polynomially bounded knowledge complexity in the hint sense, then the language L itself has a one move interactive proof system; and (2) under the blackbox simulation, if a language L has a three move private coin interactive proof system with polynomially bounded knowledge complexity in the hint sense, then the language L itself has a one move interactive proof system. These results imply that as long as the blackbox simulation is concerned, any language L AM＼MA is not allowed to have a bounded move public coin (or three move private coin) interactive proof system with polynomially bounded knowledge complexity in the hint sense unless AM = AM. In addition, we present a definite distinction between knowledge complexity in the hint sense and in the strict oracle sense, i.e., any language in AM (resp. IP) has a two (resp. unbounded) move public coin interactive proof system with polynomially bounded knowledge complexity in the strict oracle sense.

This letter deals with the reliability function in the case of periodic preventive replacement of items in order to increase MTBF, that is, two replacement policies; strictly periodic replacement (SPR) and randomly periodic replacement (RPR). We stress on simple introduction of the reliability theory under preventive replacement policies using the Laplace transform and obtain the theoretical results of SPR and RPR. Then these results are applied to the Weibull distribution and finally in order to show useful information of preventive replacement, the numerical results of SPR are provided.

New focused ion beam (FIB) methods for microscopic cross-sectioning and observation, microscopic crosssectioning and elemental analysis, and aluminum film microstructure observation are presented. The new methods are compared to the conventional methods and the conventional FIB methods, from the four viewpoints such as easiness of analysis, analysis time, spatial resolution, and pinpointing precision. The new FIB methods, as a result, are shown to be the best ones totally judging from the viewpoints shown above.