New critical-dimension controlling technique of off-axis illumination for aperiodic patterns has been developed. By means of arranging not-imaging additional pattern near 0.25 micron isolated patterns, the depth of focus of an isolated pattern was improved as well as the periodic patterns. Simulation and experimental results were verified on a 0.48 numerical-aperture, KrF excimer laser stepper. Using new deep-ultra-violet hardening technique for chemically amplified positive resist, the critical dimension loss of resist pattern was prevented. 0.25 micron design rule pattern was obtained with excellent mask linearity without critical-dimension-loss. The combination techniques are achieved quarter micron design rule complex circuit pattern layouts.

This paper describes the formation of ultra-thin tantalum oxide capacitors, using rapid thermal nitridation (RTN) of the storage-node polycrystalline-silicon surface prior to low-pressure chemical vapor deposition of tantalum oxide, using penta-ethoxy-tantalum [(Ta(OC2H5)5) and oxygen gas mixture. The films are annealed at 600-900 in dry O2 atmosphere. Densification of the as-deposited film by annealing in dry O2 is indispensable to the formation of highly reliable ultra-thin tantalum oxide capacitors. The RTN treatment reduces the SiO2 equivalent thickness and leakage current of the tantalum oxide film, and improves the time dependent dielectric breakdown characteristics of the film.

IC performance simulation for statistical purpose is usually very time-consuming since the scale and complexity of IC have increased greatly in recent years. A common approach for reduction of simulation cost is aimed at the nature of simple modeling instead of actual circuit performance simulations. In this paper,a stochastic interpolation model (SIM) scheme is proposed which overcomes the drawbacks of the existing polynomial-based approximation schemes. First,the dependence of the R2press statistic upon a parameter in SIM is taken into account and by maximizing R2press this enables SIM to achieve the best approximation accuracy in the given sample points without any assumption on the sample data. Next, a sequential sampling strategy based on variance analysis is described to effectively construct SIM during its update process. In each update step, a new sample point with a maximal value of variance is added to the former set of the sample points. The update process will be continued until the desired approximation accuracy is reached. This would eventually lead to the realization of SIM with a quite small number of sample points. Finally, the coefficient of variance is introduced as another criterion for approximation accuracy check other than the R2press statistic. The effectiveness of presented implementation scheme is demonstrated by several numerical examples as well as a statistical circuit analysis example.

A C1 interpolation scheme for constructing surface patch on n-sided region (n5, 6) is presented. The constructed surface patch matches the given boundary curves and cross-boundary slopes on the sides of the n-sided region (n5, 6). This scheme has relatively simple construction, and offers one degree of freedom for adjusting interior shape of the constructed interpolation surface. The polynomial precision set of the scheme includes all the polynomials of degree three or less. The experiments for comparing the proposed scheme with two schemes proposed by Gregory and Varady respectively and also shown.

A technique to realize a transconductance which is relatively insensitive over temperature variations is reported. Simulation results with MOS and bipolar transistors indicate substantial improvement in temperature insensitivity over a range exceeding 100 degrees Celsius. It should find useful applications in analog LSI/VLSI systems operating over a wide range of temperature.

The main problem in statistical pattern recognition is to design a classifier. Many researchers point out that a finite number of training samples causes the practical difficulties and constraints in designing a classifier. However, very little is known about the performance of a classifier in small training sample size situations. In this paper, we compare the classification performance of the well-known classifiers (k-NN, Parzen, Fisher's linear, Quadratic, Modified quadratic, Euclidean distance classifiers) when the number of training samples is small.

A design rule relaxation approach is one of the most important requirements for high density DRAMs. The approach relaxes the design rule of a element in comparison with the memory cell size and provides high density DRAMs with the minimum development of a scaled-down MOS structure and a fine patterning lithography process. This paper describes two design rule relaxation approaches, a close-packed folded (CPF) bit-line cell array layout and a Boosted Dual Word-Line scheme. The CPF cell array provides 1.26 times wider active area pitch and maximum 1.5 times wider isolation width. The Boosted Dual Word-Line scheme provides 2n times wider 1st Al pitch on memory cell array, double word-line driver pitch and 1.5 times larger design rule for 1st Al and contacts under 1st Al. Especially wide design rule of the Boosted Dual Word-Line scheme provides several times depth of focus (DOF) for 1st Al wiring which gives several times higher storage node and larger capacitance for capacitor over bit-line (COB) stacked capacitor cells. These approaches are successfully implemented in a 4 Mb DRAM test chip with a 0.91.8 µm2 memory cell.

Optical parameters of KrF excimer laser stepper are optimized for 0.25 µm level patterning by means of a light intensity simulation method. The light intensity simulation method is applied conventional and two modified illuminations (annular and 4-point) to improve the depth of focus (DOF) at 0.25 µm periodic lines and spaces pattern (L&S). Simulation results obtained are; (1) the DOF of conventional illumination is not sufficient even in the optimum condition (NA=0.5, σ=0.8), (2) more than 1.5 µm DOF could be achieved with an annular illumination, if present resist performance is improved slightly, and (3) wider DOF is obtained in the case of with 4-point illumination. However, the DOF is rather degraded in the specific sized (near double/triple sized) region and oblique pattern, therefore the application of this illumination is restricted into some specific mask layout pattern.

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.

This paper describes Japanese spoken sentence recognition using hybrid language modeling, which combines the advantages of both syntactic and stochastic language models. As the baseline system, we adopted the HMM-LR speech recognition system, with which we have already achieved good performance for Japanese phrase recognition tasks. Several improvements have been made to this system aimed at handling continuously spoken sentences. The first improvement is HMM training with continuous utterances as well as word utterances. In previous implementations, HMMs were trained with only word utterances. Continuous utterances are included in the HMM training data because coarticulation effects are much stronger in continuous utterances. The second improvement is the development of a sentential grammar for Japanese. The sentential grammar was created by combining inter- and intra-phrase CFG grammars, which were developed separately. The third improvement is the incorporation of stochastic linguistic knowledge, which includes stochastic CFG and a bigram model of production rules. The system was evaluated using continuously spoken sentences from a conference registration task that included approximately 750 words. We attained a sentence accuracy of 83.9% in the speaker-dependent condition.

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.

A new mobility model dependent upon electron concentration is presented for studying the screening effect on ionized impurity scattering. By coupling this model with the drift-diffusion and Hartree models, the effects of self-consistent and quasi-equilibrium screening on carrier transport in heavily doped systems are revealed for first time. The transport mechanism is found to be dominated by the electron-concentration-dependent mobility, and transconductance is shown to be determined by effective mobility and changes from degraded to enhanced characteristics with electron concentration modulation.

Among various photonic switching technologies, photonic frequency division multiplexing technology is most promising. In this paper a novel photonic FDM (Frequency Division Multiplexing) system is proposed. The proposed system consists of n (multiplicity of frequencies) independent subnetworks, each of which is identified by a specific frequency, and of which each network topology is identical. When a connection is required by a terminal, the network selects a subnetwork that can afford it, and assigns a frequency representing the selected subnetwork to the terminal. This system eliminates frequency converting devices and traffic concentration equipment, which will reduce the size and cost of the system. A very small sized switching system of very large capacity will be easily realized. In this paper, first we will address the basic concept of the proposed system, and then discuss some technical problems and their solutions concerning network configuration, switch matrix structure, subscriber network configuration, control scheme and frequency multiplicity. Some experimental results are also mentioned.

Impact ionization () in two n+-n--n+ device structures is investigated. Data obtained from self-consistent Monte-Carlo (SCMC) simulations of the devices is used to show that the average energy () of only those high energy electrons contributing to is an appropriate variable for the modeling of . A transport model allowing one to calculate is derived from the Boltzmann transport equation (BTE) and calibrated by the SCMC simulation results. The values of and the coefficient, αii, predicted by the proposed model are in good agreement with the Monte-Carlo data.

The performance of a drift-diffusion device simulator using massively parallel processors is improved by modifying the preconditioner for the iterative solver and by improving the initial guess for the Newton loop. A grid-to-processor mapping scheme is presented to implement the partitioned natural ordering preconditioner on the CM-5. A new preconditioner called the block partitioned natural ordering, which may include fill-ins, improves performance in terms of CPU time and convergence behavior on the CM-5. A multigrid discretization to implement a block Newton initial guess routine is observed to decrease the CPU time by a factor of two. Extensions of the initial guess routine show further reduction in the final fine grid linear iterations.

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.

We investigated the impact of velocity overshoot effect on collector signal delay of bipolar devices by using Monte Carlo simulation method. We found that insertion of an i-layer (lightly doped, intrinsic layer) between base and collector can increase the delay, but the strength of this effect is a function of the i-layer thickness. When the i-layer becomes thinner, the problem of increasing delay seems to disappear. This recovery of delay is realised with a mechanism which is completely different from that in drift-diffusion model.

An advanced model for self-heating effects in power semiconductor devices is derived from principles of irreversible thermodynamics. The importance of the entropy balance equation is emphasized. The governing equations for the coupled transport of charge carriers and heat are valid in both the stationary and transient regimes. Four characteristic effects contributing to the heat generation can be identified: Joule heating, recombination heating, Thomson heating and carrier source heating. Bandgap narrowing effects are included. Hot carrier effects are neglected. Numerical methods to solve the governing equations for the coupled transport of charge carriers and heat are described. Finally, results obtained in simulating latch-up in an IGT are discussed.

As a general basis for constructing a cooperative and flexible dialogue system, we are interested in modelling the inference process of an agent who participates in a dialogue. For this purpose, it is natural and powerful to model it in his general cognitive framework for problem solving. This paper presents such a framework. In this framework, we represent agent's mental states in the form called Mental World Structure, which consists of multiple mental worlds. Each mental world is a set of mental propositions and corresponds to one modal context, that is, a specific point of view. Modalities in an agent's mental states are represented by path expressions, which are first class citizens of the system and can be composed each other to make up composite modalities. With Mental World Structure, we can handle modalities more flexibly than ordinary modal logics, situation theory and other representation systems. We incorporate smoothly into the structure three basic inference procedures, that is, deduction, abduction and truth maintenance. Precise definitions of the structure and the inference procedures are given. Furthermore, we explain as examples, several cooperative dialogues in our framework.

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.