Nonlinear characteristics of a DBR (Distributed Bragg Reflector) Cherenkov laser are investigated with the aid of particle simulation, allowing for the nonlinear properties of the electron beam. Numerical results show that the EM power extracted from the cavity is considerably suppressed by the nonlinear effect of the electron beam. Additionally, the extracted EM power is found to be critically dependent on the reflection coefficient of the DBR at the output end. Thus the DBRs at both ends of the cavity should be carefully designed in order to extract the EM power from the cavity efficiently.

Topographical changes induced by optical near-field around photo-irradiated nanoparticles were attained using a pulsed laser with a large peak power as a light source. The arrayed structure of nanoparticles was transcribed on urethane-urea azo copolymer film as dent structure. The experiments by the pulsed laser of different wavelength showed that the topographical change was caused by the light absorption. The dent diameter and the dent depth changed depending on the diameter of nanoparticles.

For plasma simulations, we developed a one-dimensional (1d) Object-Oriented Particle-in-Cell code for X11-based Unix workstations (XOOPIC) by modifying the current two-dimensional version which was originally developed by PTSG (Plasma theory and simulation group) in the University of California at Berkeley. We implemented a simplified field solve and current deposition in the code. We retained three components of particle velocity, although the spatial variation for particle position and field components is limited to one dimension. To verify the function of the 1d code, we perform simulations with typical models such as the Child-Langmuir current model and electromagnetic wave propagation in plasma. In both cases, the simulation results quantitatively agree with the theory.

An epoxy-modified urethane rubber mixed with carbon particles is now chosen as the millimeter-wave absorber material in our study. The absorption characteristics of the absorber is measured under temperature changes. The weatherability of our absorber is also clarified based on absorption characteristics, thickness and hardness of the sample. As a result of the temperature characteristics of the absorber, the difference of the maximum absorption frequency under temperature changes is about 1 GHz, however the absorption of 20 dB or more is obtained between 54 and 58 GHz. The result of accelerated artificial exposure test is that 2.8% of the thickness of our sample is shrunk after 1000 hour exposure, and the hardness of rubber is hardened with increasing test time. It is also confirmed that the deterioration of the absorption ranges from 1 to 3 dB, although the absorption of about 20 dB is kept at the frequency range. As a consequence, it is confirmed that the wave absorber using the epoxy-modified urethane rubber mixed with carbon particles has good weatherability including our desired temperature characteristics, and it is suitable for outdoor use.

We propose a new sampling method for 2D and 3D implicit surfaces. The method is based on a stochastic process defined by the Langevin equation with a Gaussian random-force term. Our Langevin equation describes a stochastic-dynamical particle, which develops in time confined around the sampled implicit surface with small width. Its numerically generated solutions can be easily moved onto the surface strictly with very few iteration of the Newton correction. The method is robust in a sense that an arbitrary number of sample points can be obtained starting from one simple initial condition. It is because (1) the time development of the stochastic-dynamical particle does not terminate even when it reaches the sampled implicit surface, and (2) there is non-zero transition probability from one disconnected component to another. The method works very well for implicit surfaces which are complicated topologically, mathematically, and/or in shape. It also has some advantageous features in rendering 3D implicit surfaces. Many examples of applying our sampling method to real 2D and 3D implicit surfaces are presented.

In order to enhance the energy transfer efficiency in a rectangular Cherenkov laser, we propose to vary properly the permittivity of a loaded dielectric in the transverse direction. With the aid of particle simulation, we investigate the amplification characteristics of the rectangular Cherenkov laser with a dielectric permittivity varied in the transverse direction, demonstrating the effectiveness of our proposal for efficiency enhancement.

Experiment is reported of enhanced backscattering of light in binary and ternary suspensions of rutile and/or alumina particles. With a conventional CCD camera system for observing the phenomena, the angular line shape and the enhancement factor were agreed with the theoretically predicted curve and value. Observation of the angular distribution scattered at the backscattered direction supported the hypothesis proposed by Pine et al. , in which the transport mean free path of the polydisperse mixture can be expressed in terms of summing its reciprocal values weighted over the particle sizes.

In order to enhance the energy transfer efficiency in a Cherenkov laser, we propose to use a tapered waveguide with a dielectric thickness properly varied stepwise in the longitudinal direction. With the aid of particle simulation, we investigate the nonlinear characteristics of the Cherenkov laser with the tapered waveguide, demonstrating the effectiveness of our proposal for efficiency enhancement.

The effects of α-particle-induced parasitic bipolar current on soft errors in submicron 6-transistor SOI SRAMs were numericaly studied. It was shown that the bipolar current induces soft errors and that there exists a critical quantity which determines the soft error occurrence in the SOI SRAMs. Simulated soft error rates were in the same order as those for bulk SRAMs.

Wet cleaning in actual LSI process is difficult to remove contamination perfectly, because the cleaning condition must be moderate to maintain device characteristics and device texture and because wet cleaning is not so effective for the particles generated during processes such as etching, photo lithography and film formation. Particle reduction depends on particle characteristics, i.e. the sticking force and the chemical structure of the particles. Metallic contamination on wafers, depending on the kind of solutions and the metal concentration in cleaning solutions, degrades TDDB characteristics and recom-bination lifetime. Although the lifetime degradation by the metallic contamination is appreciable, it is much smaller than those caused by damage in etching and in ion implantation.

The scaling laws between the design rules and the smallest sizes and numbers of particles capable of causing pattern defects and scrapping dies in semiconductor device manufacturing are described. Simulation with electromagnetic waveguide model indicates the possibility that particles, the sizes of which are of comparable order or even smaller than the wavelength of the lithography irradiation sources, are capable of causing pattern defects. For example, in the future 0.25 µm-design-rule era, the critical sizes of Si, Al, and SiO2 particles are simulated as 120 nm 120 nm, 120 nm 120 nm, and 560 nm 560 nm, respectively, in the case of 0.7 µm-thick chemically-amplified positive photoresist with 47 nm-thick top anti-reflective coating films. Future giga-scale integration era is also predicted.

Systems for removing particulates and gaseous contaminants using the UV/photoelectron method under atmospheric and low pressure conditions have been investigated and its availability has been demonstrated. From experimental results, more than 90 % of particulate contaminants are removed by this method under atomospheric and low pressure conditions. This method can be used to design superclean spaces for wafer stockers, and wafer delivering systems in the LSI fabrication process.

In order to simulate the mechanism of particle growth by film deposition, imaginary-particle formation method has been newly developed. By using this formation method, the particle size, the particle height and the position of particle on a wafer could be controlled very easily. In this study, the imaginary-particles of various size larger than 0.15 micron and various height were formed on a wafer. By using these imaginary-particles, the effects of a deposition method, a film thickness, a particle size and a particle height upon the particle growth were investigated. As deposition methods, low pressure CVD method, plasma CVD method and sputtering method were compared. As a result, in all deposition method, it's clear that the particle growth doesn't depend on the initial size, and is proportional to the film thickness. Their particle growth rates are characterized by the deposition method, and their values are 1.9, 1.1 and 0.64 in low pressure CVD, plasma CVD and sputtering method, respectively. These values can be explained by the step coverage decided by the deposition method. Furthermore, the particle growth on imaginary-particle was compared with that on the real-particle. It is clear that the growth mechanism of the real-particle is closely similar to that of imaginary-particle, and the study by use of the imaginary-particle is very effective to make clear the mechanism of particle growth. Therefore, the particle size which should be controlled before deposition process is necessary to be decided by counting the particle growth shown in this paper.

Coherent and incoherent electromagnetic (EM) waves scattered by many particles are approximately expressed as solutions of integral equations by unconventional multiple scattering method. The particles are randomly displaced from a uniformly ordered distribution, and hence the distribution of particles can change from total uniformity to complete randomness. The approximate expressions of the EM waves are systematically given, independent of the distributions of particles, on the following assumptions. First the particles are identical in material, shape, size and orientation. Second each random displacement of particles from the ordered positions is statistically independent of each other and homogeneous in space. These assumptions may be extended to more general ones but have been used here to make clear the derivation process of the coherent and incoherent EM waves. The approximate expressions of the EM waves are reduced to known ones for both limiting cases: a periodic distribution and a very sparse random distribution. The effective dielectric constant of a random medium containing randomly distributed dielectric spheres can be calculated from the coherent EM wave and compared with those given by conventional methods such as the quasi-crystalline approximation, using the previous results. The comparison indicates the advantage of the method presented here. The present method is expected to be useful for the study of interaction of EM waves with many particles.

This paper describes the new α-particle induced soft error mechanism, the Minority Carrier Outflow (MCO) effect, which may seriously affect the reliability of the scaled DRAMs with three dimensional capacitors. The MCO chargge increases as the device size miniaturizes because of the three dimensional capacitor effect as below. As the device scales down, the storage node volume decreases which results in the higher minority carrier density in the storage node and larger outflow charge. Also as the device plan view miniaturizes, the stack capacitor height or trench depth does not scales down or even increases to keep the storage node capacitance, therefore the initially generated minority carrier becomes larger. A simple analytical MCO model is introduced to evaluate the MCO effect quantitatively. The model agrees well with the three dimensional device simulation. The MCO model predicts that the life time of the minority carrier in the storage node strongly affects the MCO charge, however, even when the life time is as small as the order of 100 ps, the MCO effect can be the major soft error mechanism.

A particle trajectory estimation method from far electromagnetic fields are discussed in this paper. Authors have already presented a trajectory estimation method for single particle system and good agreements between a source particle trajectory and an estimated one have been obtained. For this, this paper discusses twin particles system as an examples of multi-particles systems for simplicity. First of all, it is pointed out that far electromagnetic fields from the twin particles system show quite different aspect from the single particle system using an example, radiation patterns produced by two particles which carry out circular motion. This result tells us that any trajectory estimations for general multi-particles system are almost impossible. However, it is shown that when the distance between the particles is small, the estimation method for the single particle system can be applied to the twin particles system, and that twin particles effects appear as disturbance of estimated trajectory.

We have investigated the relationship between particle removal efficiency and etched depth in SC-1 solution (the mixture composed of ammonium hydroxide, hydrogen peroxide and DI water) for Si wafers. The Si etching rate increases with increasing NH4OH (ammonium hydroxide) concentration. The particle removal efficiency depends on the etched Si depth, and is independent of NH4OH concentration. The minimum required Si etching depth to get over 95% particle removal efficiency is 4 nm. Particles on the Si wafers exponentially decrease with increasing the etched Si depth. However the particle removal efficiency is not affected by particle size ranging from 0.2 to 0.5 µm. The particle removal mechanism on the Si wafers in SC-1 solution is dominated by the lift-off of particles due to Si undercutting and redeposition of the removed particle.

Today, defect sources of LSI device mainly lie in the process equipments. The particles generating in these equipments are introduced onto the wafer, and form the defects resulting in functional failures of LSI device. Thus, reducing these particles is acquired for increasing production yield and higher productivity, and it is important to identify the particle source in the equipment. In this study, we discussed new two methods to identify this source in the equipment used in the production line. The important point of identifing is to estimate the particle generation with short time and high accuracy, and to minimize long time stop of the equipment requiring disassembly. First, we illustrated "particle distribution analysis method." In this method, we showed the procedure to express the particle distribution mathematically. We applied this method to our etching equipment, and could identify the particle source without stopping this etching equipment. Secondly, we illustrated the method of "in-situ particle monitoring method," and applied this method to our AP-CVD equipment. As a result, it was clear the main particle source of this equipment and the procedure for decreasing these particles. By using this method, we could estimate the particle generation at real time in process without stopping this equipment. Thus, both methods shown in this study could estimate the particle generation and identify the particle source with short time and high accuracy. Furthermore, they do not require long time stop of the process equipment and interrupting the production line. Therefore, these methods are concluded to be very useful and effective in LSI manufacturing process.

We deal with a new type ceramic emitter which is used in a cleanroom ionizer system and is composed of a needle-shaped silicon and a rod-shaped silicon carbide ceramics. The discharge test was carried out to investigate the particle generation from the emitter and the degradation of the emitter. As a result, it was found that the ceramic emitter had practically higher performance than a conventional tungsten emitter.

With the use of a two-dimensional model, single laser beam trapping of particles is analyzed as the electromagnetic boundary-value problem. From the numerical results, it is found that the trapping mechanism for this system depends upon the surface field distribution of the object.