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.

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.

A new line simulator, SEMALIS has been developed. This simulator can handle complicated lot processings to maintain processing quality and efficient line operations to improve line performance. The current manufacturing line consists of five resource models: lot, process sequence, equipment, lot processing, and line operations. The parameters of these models are defined so as to accurately reflect the state of the line operations. From our simulation results, we confirmed that SEMALIS accurately identifies bottlenecks or starvations where equipment can be added or reduced to optimize equipment utilization through resource planning, and that SEMALIS can also be used to evaluate the long-term effects of line operating methods on the line performance of ASIC manufacturing lines.

In order to establish the advanced and costeffective wet cleaning technology, it is essential to reveal the mechanism of contamination adhesion and removal on Si surfaces in solutions. To reveal the mechanism of noble metal adhesion onto the Si surface in wet processes, the behavior of Cu2+ deposition onto Si surfaces in solutions was investigated. The experimental results reveal the mechanism of electrochemical metallic contamination of noble metals on Si surfaces. Moreover, it was found that, in HF solutions, Si is not directly etched in a form of SiF62- by such an oxidizing agent as Cu2+ but is first turned to oxide and then etched off. For preventing noble metal deposition on Si surfaces, it is necessary not only to keep the noble metals in the solution (i.e. to dissolve noble metals) but also to prevent oxidation/reduction reaction between Si and the noble metal ion. It is found that this oxidation/reduction reaction can be prevented by increasing the redox potential of solutions, injecting surfactants or chelating agents, and making the Si surface covered with oxide. It has been revealed that Cu deposition can be prevented by setting the redox potential of the solution at over 0.75 V vs. NHE. Cu deposition in DHF solutions can be prevented by setting the redox potential at 0.85 V vs. NHE or more. For removing Cu from the Si surface, the same conditions are found to be necessary. Moreover, it is revealed that metallic impurities included in the oxide can be removed only by etching. It is also revealed that chemicals to prevent metal deposition must be used to remove metals such as Cu which easily get redeposited on the bare Si surface. Finally, a new wet cleaning process employing ozonized ultrapure water, NH4OH/H2O2/H2O, and surfactant-injected DHF to replace the conventional RCA cleaning method is proposed.

Multiple TDMA bursts assignment between a base station and a personal terminal will be required for multimedia communications that offers high speed signal transmission such as voice and data simultaneous transmission. This paper proposes a reliable packet transmission method for TDMA based wireless multimedia communications. The proposed method employs an adaptive transmission rate control according to the packet length and a burst diversity technique is applied to improve the frame error rate of a packet. The frame error rate performance has been approximated theoretically by using fade- and infade-duration statistics of a Rayleigh fading channel and a computer simulation has been carried out for two control channels, FACCH/SACCH (Fast/Slow Associated Control CHannel) in the PHS as well as GSM. Both results indicate that the frame error rate is dramatically improved, about one order, when two bursts have different frequency and improved by about 25% when the two bursts have the same frequency.

A detabase system that provides step-by-step guidance for LSI failure analysts has been developed. This system has three main functions: database, navigator, and chip tracking. The datebase stores failure analysis information such as analysis method and failure mechanisms including image data. It also stores conditions and results of each analysis step and decisions to proceeds to the next analysis step. With 2000 failure analysis cases, data retrieval takes 6.6 seconds, a table containing 20 photos is presented in 6.5 seconds, and a different set of data can be displayed in 0.6 seconds. The navigator displays a standard analysis procedure illustrated in flow charts.The chip tracking shows where the particular chip is and what analysis it is undergoing, which is useful for the situation where many chips are simultaneously analyzed. Thus, this system has good enough functions of analysis procedure management and performance of quick data access to make failure analysis easier and more successful.

High-performance ULSI devices require ultraclean silicon surfaces, the complete removal of native oxides, and atomic level flatness and stabilization of the cleaned surfaces against molecular contaminants. Dry cleaning techniques are an attractive alternative to conventional wet processing for future ULSI production using cluster chambers or multi-process cham-bers. Organic contaminants, including photoresist polymers, are effectively removed by photo-excited ozone cleaning. We have found photo-excited halogen radicals to be useful for removing trace metals and native oxides from silicon surfaces without damaging on silicon and silicon-dioxide surfaces. We success-fully terminated hydrogen on (100) silicon surfaces by annealing in pure hydrogen ambient. A dry cleaning system with these sequential processes will be useful in constructing fully-integrated mass-production lines of high-performance ULSI devices.

The realization of scientific manufacturing of ULSIs in the 21st century will require the development of a technical infrastructure of "Ultra Clean Technology" and the firm establishment of the three principles of high performance processes. Three principles are 1)Ultra Clean Si Wafer Surface, 2)Ultra Clean Processing Environment, and 3)Perfect Parameter controlled process. This paper describes the methods of resolving the problems inherent in Ultra Clean Technology, taking as examples issues in quarter-micron or more advanced semiconductor process and manufacturing equipment, particularly when faced with the challenges of plasma dry etching. Issues indispensable to the development of tomorrow's highly accurate and reliable plasma dry etching equipment are the development of technologies for the accurate measurement of plasma parameters, ultra clean gas delivery systems, chamber cleaning technology on an in-situ basis, and simulating the plasma chemistry.This paper also discusses the standardization of semiconductor manufacturing equipment, which is considered one of the ways to reduce the steep rise in production line construction costs. The establishment of Ultra Clean Technology also plays a vital role in this regard.

This paper proposes a new emphasizing three-dimensional pointing device considering user friendliness and lack of cable clutter. The proposed method utilizes five degrees of freedom via the medium of non-verbal voice of human. That is, the spatial direction of the sound source, the type of the voice phoneme and the tone of the voice phoneme are utilized. The input voice is analyzed regarding the above factors and then taking proper effects as previously defined for human interface. In this paper the estimated spatial direction is used for three-dimensional movement for the virtual object as three degrees of freedom. Both of the type and the tone of the voice phoneme are used for remaining two degrees of freedom. Since vocalization of nonverbal human voice is an everyday task, and the intonation of the voice can be quite easily and intentionally controlled by human vocal ability, the proposed scheme is a new three-dimensional spatial interaction medium. In this sense, this paper realizes a cost-effective and handy nonverbal interface scheme without any artificial wearing materials which might give a physical and psychological fatigue. By using the prototype the authors evaluate the performance of the scheme from both of static and dynamic points of view and show some advantages of look and feel, and then prospect possibilities of the application for the proposed scheme.

A goal of a broadband ISDN network is to provide integrated transport for a wide range of applications such as teleconferencing, entertainment video, and file distribution. These require multipoint communications in addition to conventional point-to-point connections. The essential component to provide multipoint communications is a multicast packet switch. In this paper, we propose and analyze a new parallel multicast packet switch which easily approaches a maximum throughput of 100% as the number of fanout and multicast rate are increased. The proposed switch consists of a simple ring network and a point-to-point switch network in parallel. The ring network provides both replication and routing of multicast packets. The point-to-point switch network is responsible for delivering only unicast packets. The ring network provided in this switch overcomes the problems of clock synchronization and unfairness of access in the slotted ring by synchronizing the ring to the time slot used in the point-to-point switch and providing small amount of speed-up. Moreover, the significant drawbacks of the basic cascaded multicast fabric design are removed in this parallel switch which can separate the unicast and multicast packets before entering the switch fabric. The performance analysis shows that this switch with the small size of input/output buffers achieves good performance in delay and throughput, and the packet loss probability less than 10-9.

To realize better bit error rate performance in fast fading environments, this paper proposes the open loop reverse modulation carrier recovery scheme which employs a new open loop carrier extractor and regenerator instead of using a feed back loop. The proposed scheme realizes stable regenerated carrier signals to achieve low bit error rate not only under additive white Gaussian noise environments but also under fast fading environments. Computer simulations clarify that the proposed scheme always achieves better bit error rates than conventional differential detection or coherent detection with feed back loops under the various fading environments examined.

This paper proposes a new block coded quadrature amplitude modulation (BC-QAM) scheme, which is designed by an optimization technique based on simulated annealing. Simulated annealing is an effective nonlinear optimization technique and can be applied to both the discrete and the continuous optimization problems. In this paper, the simulated annealing technique is used to design the optimum BC-QAM signal, which minimizes the upper bound on the bit error rate (BER) in a Rayleigh fading channel. The computer simulation shows that the proposed BC-QAM can improve the BER performance. This paper also proposes a simplified design method to reduce the number of variables to be optimized. The proposed simplified method optimizes the in-phase and quadrature components of the BC-QAM signal separately. The computer simulation also shows that the BC-QAM designed by the simplified method gives little degradation on the BER performance, although the simplified method can significantly reduce the number of optimization variables.

In this paper we analyze the reliability of a simple broadcasting scheme for hypercubes (HCCAST) with random faults. We prove that HCCAST (n) (HCCAST for the n-dimensional hypercube) can tolerate Θ(2n/n) random faulty nodes with a very high probability although it can tolerate only n - 1 faulty nodes in the worst case. By showing that most of the f-fault configurations of the n dimensional hypercube cannot make HCCAST (n) fail unless f is too large, we illustrate that hypercubes are inherently strong enough for tolerating random faults. For a realistic n, the reliability of HCCAST (n) is much better than that of the broadcasting algorithm described in [6] although the latter can asymptotically tolerate faulty links of a constant fraction of all the links. Finally, we compare the fault-tolerant performance of the two broadcasting schemes for n = 15, 16, 17, 18, 19, 20, and we find that for those practical valuse, HCCAST (n) is very reliable.

In order to ensure the reliability and safety of equipment installed in process lines, it is important that maintenance and management should make efficient use of machine diagnosis techniques. Machine diagnosis by means of acoustic signals has hitherto been beset with difficulty, but there is now a strong demand that new acoustic type diagnosis equipment (utilizing acoustic signals) be developed. In response to this demand, the authors recently conducted research on diagnosis of machine faults by means of the processing of acoustic signals. In this research they were able to develop new acoustic type machine diagnosis techniques, and, using these techniques, to develop acoustic diagnosis equipment for practical use.

The family Pk of graphs with proper-path-width at most k is minor-closed. It is known that the number of minimal forbidden minors for a minor-closed family of graphs is finite, but we have few such families for which all the minimal forbidden minors are listed. Although the minimal acyclic forbidden minors are characterized for Pk, all the minimal forbidden minors are known only for P1. This paper lists 36 minimal forbidden minors for P2, and shows that there exist no other minimal forbidden minors for P2.

CAMs (Content Addressable Memories) are functional memories which have functions such as word-parallel equivalence search, bilateral 1-bit data shifting between consecutive words, and word-parallel writing. Since CAMs can be integrated because of their regular structure, massively parallel CAM functions can be executed. Taking advantage of CAMs, Ishiura and Yajima have proposed a parallel fault simulation algorithm using a CAM. This algorithm, however, requires a large amount of CAM storage to simulate large-scale circuits. In this paper, we propose a new massively parallel fault simulation algorithm requiring less CAM storage, and compare it with Ishiura and Yajima's algorithm. Experimental results of the algorithm on CHARGE --the CAM-based hardware engine developed in our laboratory--are also reported.

A new low-power and high-speed CMOS interface circuit is proposed in which signals are transmitted by means of impulse voltage. This mode of transmission is called impulse transmission. Although a termination resistor is used for impedance matching, the current through the output transistors and the termination resistor flows only in transient states and no current flows in stable states. The output buffer and the termination resistor dissipate power only in transient states, so their power dissipation is reduced to 30% that of conventional low-voltage-swing CMOS interface circuits at 160 MHz. The circuit was fabricated by 0.5 µm CMOS technology and was evaluated at a supply voltage of 3.3 V. Experimental results confirm low power of 4.8 mW at 160 MHz and high-speed 870 Mb/s error free point-to-point transmission.

A new approach is presented for recovering the 3-D shape from shading image. Photometric Stereo Method (PSM) is generally based on the direct illumination. PSM in this paper is modified with the indirect diffuse illumination method (IDIM), and then applied to hybrid reflectance model which consists of two components; the Lambertian reflectance and the specular reflectance. Under the hybrid reflectance model and the indirect diffuse illumination circumstances, the 3-D shape of objects can be recovered from the surface normal vector extracted from the surface roughness, the surface reflectance ratio, and the intensity value of a pixel. This method is rapid because of using the reference table, simplifies the restriction condition about the reflectance function in prior studies without any loss in performance, and can be applied to various types of surfaces by defining general reflectance function.

The relative intensity noise (RIN) spectra of DC driven 1.3 µm distributed feedback laser diodes under the influence of external reflections are measured for various currents and reflection lengths. The effective power reflectivities are 310-4-310-3. The enhanced noise is observed when the relaxation oscillation frequency coincides with the external cavity frequency. It is also observed that the RIN spectra with the near end reflections differ from those with the far end reflections. The degradation of the RIN spectra is analyzed with the rate equations numerically. A new reflection noise model, which includes the carrier density change induced by the reflections, is introduced. The near and far end reflections are characterized well by this model. Furthermore, it is found that the reflection induced noise effect can be described well by the far end reflection noise model even when the reflection length is as short as 1 m.

This paper describes ALINX (Advanced Low-voltage Interface Circuit System), a low-power and high-speed interface circuit of submicron CMOS LSI for digital information and telecommunications systems. Differential and single-ended ALINXs are low-voltage swing I/O interface circuits with less than 1.0 V swing from a 1.2 V supply. Specifically, the differential ALINX features a pair of complementary NMOS push-pull drivers operating from a 1.2 V supply, reducing power consumption compared to conventional high-speed interface circuits operating from a 5 V or 3.3 V supply. The DC power consumption is approximately 11% of ECL. We observed 622 Mbps differential transmission with 8 mW power consumption and single-ended transmission at 311 Mbps with 14 mW with a PN23 pseudo-random pattern. We also describe a noise characteristic and ALINX applications to high-speed data buses and LSI for telecommunications systems. A time/space switch LSI with 0.9 W total power consumption was fabricated by 0.5 µm CMOS process technology. This chip can use a plastic QFP.