The future trends of optical technologies combined with LSI are reviewed. Present problems of LSI, and the possible solutions to these problems through the merger of the optical technology into LSI are discussed. One of the present trends in interconnection between LSI components is the timeserial approach, originally developed for the optical communication. This method is capable of high speed data transfer. The other is a space-parallel approach, arising from the two-dimensional nature of the light propagation. This approach has the capability of performing parallel processing. A hybrid OEIC, possibly on GaAs, is discussed as an example of future photonic LSI. The lack of key devices is a fundamental barrier to the future improvement of photonic LSI. Direct interaction between photons and electrons is a promissing approach. Some of the Author's ideas to promote the merger of photonics and LSI are proposed.

New illumination principle for photolithography is investigated. As the optical microlithography approaches its own limit, it becomes apparent that the simple extrapolation of the present technology is not sufficient for the future demands. This paper introduces the new imaging technology that overcomes such a boundary. First, the basic imaging formulae are analyzed and the illumination light is classified into 4 cases. 3-beam case and 2-beam case carry the object information, and the comparison of these 2 cases is carried out theoretically. It can be shown that the 2-beam case has greater depth of focus than that of the 3-beam case, though it has inferior contrast at the best focus. Since this degradation, however, has little effect, the enlargement of the depth of focus can be achieved. In reality, 2-dimensional imaging must be considered. Quadrupole effect can be deduced by the results of the analysis. It shows great improvement in the depth of focus near resolution limit. As it can be applied to the conventional masks, it can be a promising candidate for fhe future lithography. Experimental results are also shown to demonstrate the analysis.

Fabrication of 0.2 to 0.3 µm features is vital for future ultralarge scale integration devices. An area of particular concern is whether optical lithography can delineate such feature sizes, i.e., less than the exposure wavelength. The use of a phase shift mask is one of the most effective means of improving resolution in optical lithography. This technology basically makes use of the interference between light transmitting through adjacent apertures of the mask. Various types of phase shift masks and their imaging characteristics are discussed and compared with conventional normal transmission masks. To apply these masks effectively to practical patterns, a phase shifter pattern design tool and mask repair method must be established. The phase shifting technology offers a potential to fabricate 0.3 µm features by using the current i-line stepper, and 0.2 µm features by using excimer laser stepper.

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.

Breakdown fields and the charges to breakdown (Q_BD) of oxides increased after UV/Cl₂ pre-oxidation cleaning. This is due to decreased residual metal contaminants on silicon surfaces in the bottom of the LOCOS region after wet cleaning. Treatment in NH₄OH, H₂O₂ and H₂O prior to UV/Cl₂ cleaning suppressed increases in surface roughness and kept leakage currents through the oxides after UV/Cl₂ cleaning as low as those after wet cleaning alone. The large junction leakage currents--caused by metal contaminants introduced during dry etching--decreased after UV/Cl₂ cleaning which removes the contaminated layer.

A new direct projection patterning technique of aluminum using synchrotron radiation (SR) is proposed. It is based on the thermal reaction control effect of SR excitation. In the case of the Si surface, pure thermal growth is possible at 200, however, this growth is suppressed perfectly by SR irradiation. On the other hand, Al growth on the SiO₂ surface is impossible at the same temperature thermally, however, SR has an effect to initiate thermal reaction. Both new effects of SR, suppression and initiation, are clarified to be caused by atomic order level thin layers formed from CVD gases by SR excitation on the surfaces. By using these effects, the direct inverse and normal projection patterning of Al are successfully demonstrated.

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.

Step and Repeat type Electro-Optic sensing system for In Process TFT arrays have been evaluated by several Japanese LCD manufacturers which have proven the unique technology. In this paper, the concept of testing flat panel displays using "Non-contact Voltage Imaging" is described. One of the major problems in the AMLCD industry was the difficulty to do adequate non-contact tesing of the active substrate prior to final assembly. This paper describes the technology of AMLCD pixel and line defects detection that permits full functional testing on the panel during the manufacturing process.

Optical fiber transmission systems have advanced rapidly with the advent of highly advanced electronic and optical devices. This paper introduces several IC technologies required for ultra-high-speed optical transmission and overviews current IC technologies used for the existing and developing optical fiber trunk transmission systems. Future trends in device technologies are also discussed.

High-Definition Television (HDTV) 2 million pixel solid state image sensors with high performances are realized, applicable for 1 inch optical format. Key technical aspects of HDTV image sensors are suppression of smear level by maintaining large optical aperture and high readout signal rate by introducing a dual channel horizontal register. From such a perspective, new HDTV image sensors such as Stack CCD, Frame-Interline Transfer (FIT) CCD and Charge Modulation Device (CMD) are developed.

This paper reviews the development of low temperature poly Si TFT, scattering light valves addressed by TFTs and a brighter video projection system using them, with the attensin of their optical aspects. The first includes main feature which are laser induced crystallization of PECVD a-Si in almost entirely solid phase by high speed scanning CW Ar laser beam. The second includes photo-polymerization induced phase separation method for the preparation of liquid crystal polymer composite (LCPC) material and scattering light valve with low driving voltage of 6 Vrms. The last gives a brighter video screen image with high contrast ratio and includes higher light efficiency through LCPC light valves and projection lens unit by about four times than that of conventional LC light valves with polarizers.

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.

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.

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.

A new optical interconnection system suitable for high-speed ICs using a novel complementary optical interconnection technique has been developed. This system uses paired light sources and photodetectors for optical complementary operation, and greatly lowers the power consumption compared with conventional systems. Analyses and experimental results indicate that this system can operate in the gigabit range, and reduces power consumption to less than 20% of that in conventional systems at 1 Gb/s.

An integrated optoelectronic multiplier based on GaAs optoelectronic device technology, is proposed. The key element is an optoelectronic half-adder logic gate, which is composed of only two GaAs metal-semiconductor-metal photodetectors (MSM-PD's). It operates with a single clock delay, less than 100 ps. An optoelectronic full-adder and a multiplier are also composed of half-adders and surface-emitting laser-diodes (SEL's). Cascadable gates with optical interconnections are integrated. Utilizing improved device fabrication technology, an optoelectronic high-speed multiplier with a minimum number of gates will be realized in LSI.

Three custom LSIs for EB60, a direct wafer exposure electron beam system, have been developed using 0.8 µm BiCMOS and SST bipolar technologies. The three LSIs are i) a shot cycle control LSI for controlling each exposure cycle time, ii) a linear matrix computation LSI for coordinate modification of the exposure pattern data, and iii) a position calculation LSI for determining the precise position of the wafer. These LSIs allow the deflection corrector block of the revised EB60 to be realized on a single board. A new adaptive pipeline control technique which optimizes each shot period according to the exposure data is implemented in the shot-cycle control LSI. The position calculation LSI implements a new, highly effective 2-level pipeline exposure technique, the levels refer to major-field-deflection and minor-field-deflection. The linear-matrix computation LSI is designed not only for the EB60 but also for a wide variety of parallel digital processing applications.

Formation of thin insulating SiO₂ films by anodic oxidation of silicon was studied as a part of investigating an alternative method of fabricating low-cost silicon MIS solar cells. Anodization in the constant-voltage mode was carried out in nonaqueous ethylene glycol solution. The film thickness was carefully measured using an ellipsometer of wavelength 6238 . MIS cell performance was evaluated by comparing the open circuit voltage V_OC and the short circuit current density I_SC with those of the bare Schottky cell (without anodization) under illumination by a tungsten lamp. It was found that anodization in the constant-voltage mode can increase V_OC without reducing I_SC, and that anodization in the constant-voltage mode is more controllable and reproducible. The optimun formation voltage which gives the maximum V_OC of the MIS cell depends on the forming voltage of oxide. A brief discussion on the mechanism for V_OC increase is given.

The diffraction of a plane electromagnetic wave by a parallel-plate waveguide cavity with a thick planar termination is rigorously analyzed for both the E and the H polarization using the Wiener-Hopf technique. Introducing the Fourier transform for the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are solved exactly in a formal sense via the factorization and decomposition procedure. Since the formal solution involves an infinite number of unknowns and branch-cut integrals with unknown integrands, approximation procedures based on rigorous asymptotics are further presented to yield the approximate solution convenient for numerical computations. The scattered field inside and outside the cavity is evaluated by taking the inverse Fourier transform and applying the saddle point method. Representative numerical examples of the monostatic and bistatic radar cross sections are presented for various physical parameters, and the scattering characteristics of the cavity are discussed in detail.

A precise method for determining AlGaAs/GaAs HBT large-signal circuit parameters is presented. In this method, the parameters are extracted from noise parameters and small-signal S-parameters measured under various bias conditions. The measured noise parameters are fitted to the calculated noise parameters derived from an approximation of Hawkins' equations applied to the macroscopic equivalent circuit. The small-signal S-parameters help to determine the large-signal circuit parameters. The derived large-signal parameters were used to design an HBT oscillator. The simulated results using these parameters were in good agreement with the fabricated device performance.