This paper was written for LSI engineers in order to demonstrate the effect of optical interconnections in LSIs to improve both the speed and power performances of 0.5 and 0.2 µm CMOS microprocessors. The feasibilities and problems regarding new micronsize optoelectronic devices as well as associated electronics are discussed. Actual circuit structures clocks and bus lines used for optical interconnection are discussed. Newly designed optical interconnections and the speed power performances are compared with those of the original electrical interconnection systems.

We have demonstrated the successful fabrication of the monolithic integration of a GaAs metalsemiconductor field-effect transistor (MESFET), an AlGaAs/InGaAs laser and a p-n photodetector grown on a SiO2 backcoated p-Si substrate using selective regrowth by metalorganic chemical vapor deposition (MOCVD). The use of SiO2 backcoated Si substrate is effective in suppressing unintentional Si autodoping and obtaining a good pinch-off GaAs MESFET. The MESFET with 2.5400 µm2 gate exhibited a transconductance of 90 mS/mm and a threshold voltage of 2.2 V. The reliability of the laser on the Si substrate can be improved by the strain-relieved AlGaAs/InGaAs laser with the InGaAs intermediate layer. The longest lifetime of the laser is 8 h at 27. During the GaAs layer growth, the p-n photodetector is formed near the surface of the p-Si substrate by diffusing the As atoms.

Recent progress in high-speed semiconductor devices and integrated circuits (ICs) has outpaced the conventional measuring and testing instruments. With advent of ultrashort-pulse laser technology, the electro-optic sampling (EOS) technique based on the Pockels effect has become the most promising solution way of overcoming the frequency limit, whose bandwidth is approaching a terahertz. This paper reviews recent progress on the research of the EOS technniques for measuring ultrahigh-speed electronic devices and ICs. It describes both the principle of the EOS and the key technologies used for noncontact probing of ICs. Internal-node measurements of state-of-the-art high-speed ICs are also presented.

Optical interconnection is a rapidly expanding field of optical signal transmission, but it places some stringent requirements on optical devices. This paper introduces the current device characteristics of lasers and photodiodes and discusses the possibility of intra/inter wafer optical interconnection.

A unification-based Japanese parser has been implemented for an experimental Japanese-to-English spoken language translation system (SL-TRANS). The parser consists of a unification-based spoken-style Japanese grammar and an active chart parser. The grammar handles the syntactic, semantic, and pragmatic constraints in an integrated fashion using HPSG-based framework in order to cope with speech recognition errors. The parser takes multiple sentential candidates from the HMM-LR speech recognizer, and produces a semantic representation associated with the best scoring parse based on acoustic and linguistic plausibility. The unification-based parser has been tested using 12 dialogues in the conference registration domain, which include 261 sentences uttered by one male speaker. The sentence recognition accuracy of the underlying speech recognizer is 73.6% for the top candidate, and 83.5% for the top three candidates, where the test-set perplexity of the CFG grammar is 65. By ruling out erroneous speech recognition results using various linguistic constraints, the parser improves the sentence recognition accuracy up to 81.6% for the top candidate, and 85.8% for the top three candidates. From the experiment result, we found that the combination of syntactic restriction, selectional restriction and coordinate structure restriction can provide a sufficient restriction to rule out the recognition errors between case-marking particles with the same vowel, which are the type of errors most likely to occur. However, we also found that it is necessary to use pragmatic information, such as topic, presupposition, and discourse structure, to rule out the recognition errors involved with topicalizing particles and sentence final particles.

Reduction in the illumination wavelength for exposure leads to higher resolution while keeping the depth of focus. Thus, KrF excimer laser lithography has been positioned as the next generation lithography tool behind g/i-line optical lithography, and many studies have been investigated. In the early days, the excimer laser lithography had many inherent problems, such as inadequate reliability, difficult maintainability, high operating cost, and low resolution and sensitivity of resist materials. However, the performance of the excimer laser stepper has been improved and chemical amplification resists have been developed for the past decade. At present, KrF excimer lithography has reached the level of trial manufacturing of lower submicron ULSI devices beyond 64 Mbit DRAMs.

This paper discusses three approaches for combining an efficient LR parser and phoneme-context-dependent HMMs and compares them through continuous speech recognition experiments. In continuous speech recognition, phoneme-context-dependent allophonic models are considered very helpful for enhancing the recognition accuracy. They precisely represent allophonic variations caused by the difference in phoneme-contexts. With grammatical constraints based on a context free grammar (CFG), a generalized LR parser is one of the most efficient parsing algorithms for speech recognition. Therefore, the combination of allophonic models and a generalized LR parser is a powerful scheme enabling accurate and efficient speech recognition. In this paper, three phoneme-context-dependent LR parsing algorithms are proposed, which make it possible to drive allophonic HMMs. The algorithms are outlined as follows: (1) Algorithm for predicting the phonemic context dynamically in the LR parser using a phoneme-context-independent LR table. (2) Algorithm for converting an LR table into a phoneme-context-dependent LR table. (3) Algorithm for converting a CFG into a phoneme-context-dependent CFG. This paper also includes discussion of the results of recognition experiments, and a comparison of performance and efficiency of these three algorithms.

Recent progress on photoexcited process applications to fabricating of VLSI and flat panel devices in Japan has been reviewed. The excimer laser melt technique makes it possible to form large-grain poly-Si film on a glass substrate, improving TFT electrical characteristics, and to fill metals into high-aspect-ratio contact holes in VLSI metallization. Scanning of CW laser in poly-Si film led to growth of a single-crystal Si layer on SiO2 to fabricate 3-D (dimensional) devices successfully. Direct writing with pyrolytic reaction was put into practice for interconnection restructuring. In the photochemical process, lower temperature epitaxial growth of Si and dry cleaning of a Si wafer employing Hg lamp irradiation were noted. Directional etching was performed by sidewall film formation, while resolution of better than 0.5 µm was difficult to obtain due to diffraction limit. It was proposed that higher resolution would be obtained by introduction of a nonlinear process which enhanced pattern contrast.

This is a partly expository paper discussing how point processes with certain "bursty" features can be qualitatively modelled by the Markovian arrival process, a generalization of the Poisson or Bernoulli processes which can be used to obtain algorithmically tractable matrix solutions to a variety of problems in probability models.

The interface between laser-recrystallized Si and SiO2 is investigated by means of capacitance-voltage curve measurements. The recrystallization is performed by scanning cw Ar+ laser. The change in the C-V curves shows that the laser-recrystallization generates positive charge and the fast interface states at the Si-SiO2 interface, and creates n-type defects in recrystallized bulk silicon. Nominal interface charge increases linearly with a laser power. The increase in the charge is enhanced by fast laser-beam scanning velocity. The change in the C-V curve is suppressed, if a substrate is heated up to 450 during recrystallization. Complete recovery of the induced change in the C-V curves requires a subsequent furnace annealing at a temperature as high as 1100. These phenomena are explained by the generation of oxygen vacancy at the Si-SiO2 interface and quenched-in point defects in the recrystallized Si. The oxygen vacancy is produced by a reaction between the melted Si and SiO2. The quenched-in defects are produced during fast cooling of the melted Si.

The static characteristics of GaInAs(P)/GaInAsP quantum well laser diodes (QW LDs), with graded-index separate-confinement-heterostructure (GRIN-SCH) grown by metalorganic chemical vapor deposition (MOCVD), have been investigated experimentally in terms of threshold current density, internal waveguide loss, differential quantum efficiency and light output power. Very low threshold current density of 410 A/cm2, high characteristic temperature of 113 K, low internal waveguide loss of 5 cm-1, high differential quantum efficiency of 82% and high light output power of 100 mW were obtained in 1.3 µm GRIN-SCH multiple quantum well (MQW) LDs by optimizing the quantum well structure including confinement layer and cavity design. Excellent uniformity for the threshold current, quantum efficiency and emission wavelength was obtained in all MOCVD grown buried heterostructure GRIN-SCH MQW LDs. Lasing characteristics of 1.5 µm GRIN-SCH MQW LDs are also described.

A detailed numerical solution of the design criteria of in-phase lateral and single-longitudinal-mode operation GaInAsP/InP DFB laser arrays is presented. The analysis, including broad-area pumped and stripe-geometry pumped index-guided arrays, was carried out on the basis of the eigenvalue equation method. It is shown that there exists a cut-off array pitch co, at which all of the higher-order array modes are cut off. For the pitch larger than the cut-off pitch co, the modal discrimination is evaluated by the threshold gain difference between the in-phase lateral and higher-order array modes. As a result, the modal discrimination was found to decrease with the increase of the number of elements and the array pitch which is limited to be smaller than twice the cut-off pitch co to attain a stable in-phase lateral- and single-longitudinal-mode operation.

This paper investigates a two-class priority queue with decrementing service of a parameter (k1=, k2=k,1k) which operates as follows: Starting once a class-1 message service, a single server serves all messages in queue 1 until it becomes empty. After service completion in queue 1, the server switches over to queue 2 and continues serving messages in queue 2 until either queue 2 becomes empty, or the number of messages decreases to k less than that found upon the server's arrival at queue 2, whichever occurs first. It is assumed that arrival streams are Poissonian, message service times are generally distributed, and switch-over times are zero. We derive queue-length generating functions and LSTs of message waiting time distributions.

Stability property of an optically injection-locked semiconductor laser taking account of gain saturation is discussed. Numerical analysis shows that stable locking region is broadened due to gain saturation. This is because of rapid damping of relaxation oscillation due to gain saturation. It is also found that stable locking region is also broadened with increasing injection current since damping of relaxation oscillation becomes strong with increasing injection current. Numerical calculations of lasing spectrum show that the magnitude of sidepeaks appeared at harmonics of relaxation oscillation frequency under unstable locking condition are suppressed due to gain saturation.

The pressure waveforms indicated on a catheter manometer system are subject to serious distortion due to the resonance of the catheter itself, or the compliance of a particular transducer. Although several methods have been proposed for improving those characteristics, they ahave never been put into practice. We have focused on the transfer function of the catheter manometer, and made a pilot system, using the natural observation method. This method has been suggested as a means of studying the structure of the instantaneous waveform. In this manner, we were able to increace the bandwidth in the ferquency domain and reduce the ringing in the time domain. Correction was performed automatically, using a step wave. Reproduction of the waveform with a flushing device, was a task of equal simplicity, that allowed us to estimate the system parameters so that the response waveform became step-like. In the experiment, our system provided distortion-free left-ventricular pressure waveform measurements and exact evaluation of the cardiac pumping system. The values obtained came much closer to the original figures arrived at by the catheter-tip manometer system.

This paper describes a new trial of dynamical parameter estimation for the actual room acoustic system, in a practical case when the input excitation is polluted by a background noise in contrast with the usual case when the output observation is polluted. The room acoustic system is first formulated as a discrete time model, by taking into consideration the original standpoint defining the system parameter and the existence of the background noise polluting the input excitation. Then, the recurrence estimation algorithm on a reverberation time of room is dynamically derived from Bayesian viewpoint (based on the statistical information of background noise and instantaneously observed data), which is applicable to the actual situation with the non-Gaussian type sound fluctuation, the non-linear observation, and the input background noise. Finally, the theoretical result is experimentally confirmed by applying it to the actual estimation problem of a reverberation time.

We have successfully developed an optical receiver and a laser driver circuit which were implemented with 0.35 µm GaAs JFETs (junction Field Effect Transistors). The 0.35 µm GaAs. JFET had the typical transconductance of 480 mS/mm with small drain conductance. An interdigit MSM (Metal Semiconductor Metal) -type photodetector and the JFETs were monolithically integrated on a GaAs substrate for the optical receiver. The fabricated optical receiver demonstrated Gb/s operation with a very low power consumption of 8.2 mW. The laser driver circuit operated at up to 4.0 Gb/s.

A conflict detection support method for combining additional telecommunication services with existing services is proposed. In this method, telecommunication services are described by the STR (State Transition Rule) method which specifies a set of state transition rules. Though conflict detection in the past depended on manual analysis by the designer, with this method, conflict candidates are mechanically narrowed down and indicated to the designer. All conflicts between five actual telecommunication service descriptions are detected in an experiment using a system developed in line with the proposed method.

In LOTOS, requirements for a distributed system are described as a service definition. On the protocol level, each node (protocol entity) must exchange some data values and synchronization messages to provide a service described in a service definition. The tuple of the specifications of all nodes in the system which provide the service is called as a protocol specification. In order to develop the communication programs satisfying a given service definition, it is very important to develop the correct protocol specification. For this purpose, the simulation of protocol specifications is useful and it is desirable that the designer can observe how a protocol specification is executed in parallel and how synchronization messages are exchanged among the nodes. Therefore, we have developed a new tool named PROSPEX. For a given pair of a service definition and a protocol specification, it executes the protocol specification in parallel and shows its execution process graphically on X Window System. If the protocol specification executes an event sequence which does not satisfy the service definition, then PROSPEX informs it to the designer. In this paper, the design and usefulness of PROSPEX are described.

Public switching systems are intensively realtime and multi-processing, very large, long-lived, and frequently modified. Programs that control switching systems are therefore required not only to have run-time efficiency but also to be easy to maintain and extend. This paper proposes a Concurrent Object Model and an Object-Oriented Switching Program Structure. The Concurrent Object Model ensures simple and efficient real-time multi-processing. This model allows logical switching components to be implemented as "objects" in software, and the structure of the program coincides with the structure of the logical model. The program structure proposed here uses distributed call processing, which allows building-block-structured switching systems. A prototype switching program proved the effectiveness of this approach and showed that the static and dynamic overheads are within the capacity of present VLSI technology.