The paper shows some of benefits of multi-unitary decomposition in signal analysis applications. It is emphasized that decompositions of complex discrete-time signals onto a single basis provide an incomplete and in such way potentially misleading image of the signals in signal analysis applications. It is shown that the multi-unitary decimated filter banks which decompose the analyzed signal onto several bases of the given vector space can serve as a tool which provides a more complete information about the signal and at the same time the filter banks can enjoy efficient polyphase component implementation of maximally decimated, i. e. nonredundant, filter banks. An insight into the multi-unitary signal decomposition is provided. It is shown that the multiple-bases representation leads to an efficient computation of frequency domain representations of signals on a dense not necessarily uniform frequency grid. It is also shown that the multiple-bases representation can be useful in the detection of tones in digital implementations of multifrequency signaling, and in receivers of chirp systems. A proof is provided that there are possible benefits of the multiple-bases representations in de-noising applications.

This paper presents a novel approach to pixel decimation for motion estimation in video coding. Early techniques of pixel decimation use regular pixel patterns to evaluate matching criterion. Recent techniques use adaptive pixel patterns and have achieved better efficiency. However, these adaptive techniques require an initial division of a block into a set of uniform regions and therefore are only locally-adaptive in essence. In this paper, we present a globally-adaptive scheme for pixel decimation, in which no regions are fixed at the beginning and pixels are selected only if they have features important to the determination of a match. The experiment results show that when no more than 40 pixels are selected out of a 1616 block, this approach achieves a better search accuracy by 13-22% than the previous locally-adaptive methods which also use features.

A series of transparent photochemical acid-generators (PAGs) has been successfully prepared and investigated to apply ArF excimer-laser lithography. These PAGs were synthesized as new alkylsulfonium salts that have cycloalkyl groups but no aromatic ones. They were almost transparent at 193. 4 nm and have high acid-generation efficiency enough to use for ArF excimer-laser resists. The photochemical reaction of these alkylsulfonium salts occurs mainly due to the S-C bond fission. A resist utilizing the PAGs was capable to resolve a 0. 2µm L/S pattern at a 50-mJ/cm2 dose with an aqueous alkaline developer. These PAGs are promising materials for use in ArF excimer-laser lithography.

A close correlation between the YBa2Cu3Oy film morphology and location of the (100) MgO substrate during growth by excimer laser ablation was obtained. When the susbtrate was placed inside the fringe portion of the laser plume, the spiral shape was most clearly seen on the entire film surface for both the conventional and eclipse ablation methods. When the substrate was placed outside the plume, the spiral growth was less pronounced. On the other hand, when the substrate was placed inside the plume core, marked deformation of the morphology occurred, and the superconducting critical temperature was lowered. This correlation was explained to some extent by the spatial variation of kinetic energy of the flying growth species.

A unified process flow management system (UPFMS) that combines a CIM system, process/device simulator, CAD system, and manufacturing line schedular has been developed. This new system uses a new language called PDL to describe the process flow as common information for all systems. The UPFMS consists of the flow edit section, the flow inspection section, and several types of interface programs to make it suitable for use with other systems. The process flow data described using the PDL in the UPFMS provides data for controlling lots in CIM system. If modification of the process flow data in the CIM system is required, the process flow data is returned to the UPFMS and modified with inspection using a knowledge data base. Then, the error-free process flow data is sent back to the CIM system for Processes after flow inspection. Moreover, the UPFMS, with the new language PDL, generates recipe data for the equipment using an interface program, and recipe data is input to several types of equipment. Furthermore, the PDL process flow data can also be used as input data for the manufacturing line scheduler using another interface program. Mask and layout data in a CAD system can be exchanged among process/device simulators by using the UPFMS, and thus two-dimensional device characteristics. Spice paramenters can be also to be created. The UPFMS combines with CIM system, process/device simulator, CAD system, and the manufacturing line scheduler using common information, PDL. The process flow data created in the UPFMS can be used to control all systems from the simulation to CIM system as common data.

A scalable and flexible ASIC CIM system distributed on UNIX workstations, ORCHARD , has been developed. It is designed from three viewpoints: (1) cost and TAT reduction in system construction, (2) flexibility in data management for quality control, and (3) precise and quick scheduling and effective lot tracking to control TAT for each lot. The concept of a "virtual machine" is introduced to connect equipment having various protocols to a host system. The virtual machine is automatically generated at an average automatic generation ratio of as high as 89%, which leads to a reduction in cost and TAT in system construction. Data for quality control is managed by changing flexibly the "data processing recipe." This recipe defines screen format, data collected from equipment, and data transfered from various databases. Precise scheduling of lots with various levels of priority is achieved by introducing a priority evaluation function, thereby reducing scheduling time to 1/20 that for manual scheduling.

A procedure for preparing a cross-sectional transmission electron microscopy (TEM) micrograph of a specific area is outlined. A specific area in a specimen has been very difficult to observe with TEM, because a particular small area cannot be preselected in the conventional specimen preparation technique using mechanical polishing, dimpling and ion milling. The technique in this paper uses a focused ion beam (FIB) to fabricate a cross-sectional specimen at a desired area. The applications of this specimen preparation technique are illustrated for investigations of particles in the process of fabricating devices and degraded aluminum/aluminum vias. The specimen preparation technique using FIB is useful for observing a specific area. This technique is also useful for shortening the time of specimen preparation and observing wide areas of LSI devices.

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.

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.

256 MbDRAM chips have been fabricated by mix-and-match method using high NA KrF excimer laser stepper and i-line stepper. In the case of KrF stepper, the negative siloxane resist is used for rectangular and wiring patterns and the positive novolak-resin resist is used for hole patterns. Both of these two kinds of resist produce accurate pattern shape, allow-able pattern profile, satisfactory depth of focus and sufficient overlay accuracy for device fabrication in 0.25 µm design rule.

This paper describes the potential of KrF excimer laser lithography for the development and production of 64 M and 256 Mbit DRAMs on the basis of our recent developed results. Quarter micron KrF excimer laser lithography has been developed. A new chemically amplified positive resist realizes high stability and process compatibility for 0.25 micron line and space patterns and 0.35 micron contact hole patterns. This developed resist is characterized as the increase of dissolution characteristics in exposed areas, and hence means the high resolution is obtained. A multiple interference effect was greatly reduced by using our over coat film or anti-reflective coating. This over coat film has no intermixing to the resist and it is simultaneously removed when the resist is developed. This anti-reflective coating has low etch selectivity to the resist, and hence the over coat film is etched away when etching the substrate. The two major results indicate that the KrF excimer laser lithography is promising for the development of 256 MDRAMs.

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.

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.