This paper describes the cleanliness levels for the manufacturing environment and silicon wafer surface required by International Technology Roadmap for Semiconductors 2003. Concerning the contamination level for particles there is no significant revision from the 2001 version. As for AMCs, the required level of organic contaminants is expressed in terms of C16H34 instead of CH4. Table 114 of Technology Requirement for Wafer Environmental Contamination Control summarizes the levels of Surface Molecular Contaminants (SMCs) which are the adsorbed amounts of SMCs after 24-hour exposure of wafer to the air in FOUP (Front Opening Unified Pod) , Pod, Mini-environment as well as clean room air. Recent levels of detection limits of various analytical methods are discussed, and the analysis results for both SMCs on silicon wafer exposed to the air in carrier case and the AMCs in the atmosphere are introduced.
The storage capacity of hard disk drives (HDD) for personal computers has increased by more than ten thousands times for the last decade. Meanwhile, the gap between disk and head (flying height) has decreased from submicrometers to a few nanometers. Hence, the lower flying height leads to more sensitive disk to surface contamination to link to fatal failures. There have been many studies reporting that the disk surface contamination was related with the adsorption of VOCs and the corrosion of magnetic layer in the disk. However, the surface contamination derived from SO2 gas in the surroundings has been discussed insufficiently. In this work, we aimed at elucidating the mechanism of the disk surface contamination and the subsequent particle formation by exposing HDD disks to SO2 gas intentionally, followed by the evaluation of their operation performance during the endurance test. As a result, we found that a large quantity of sulfate and nickel, which was a main component of the disk substrate layer, was detected on the SO2-contaminated disk surface, while a small quantity of cobalt, which was a main one of the magnetic layer after a series of endurance tests. From these findings, we inferred the following mechanism of surface contamination of HDD disk in the coexistence of SO2 and water. Nickel is supplied from the substrate layer to the top one through holes and cracks in the films of disk owing to the corrosion triggered by adsorbed water. Eventually, it is deposited on the surface as nickel sulfate to be released in the form of particles by contact with the head.
A new-type of air purification reactor which can simultaneously remove gaseous contaminants and fine particles was developed and evaluated in this study. Two short wavelengths of UV light (185 nm and 254 nm) , irradiated from a single UV source, were separated with an optical filter and used respectively for the gas-to-particle photochemical conversion of organic gases and for the charging of particles generated with the UV/photoelectron method. This technique was applied to remove typical gaseous contaminants in clean rooms, low concentrations of di-n-butyl phthalate (DBP) , dioctyl phthalate (DOP) and low molecular-weight cyclosiloxane (LMCS) . The particles converted from their vapors were effectively removed by the UV/photoelectron method and trapped on an ozone-decomposition catalyst (ODC) , which was used to decompose O3 formed by 185 nm UV irradiation. Furthermore, the effect of photocatalyst was also investigated for the decomposition of organic gaseous compounds under irradiation of short-wavelength UV light. It became clear that the photocatalyst contributed to promote the mineralization of intermediate products.
Heat island is a serious problem these days. In this study, the temperature variation during the summer nights induced by aerosol is evaluated using a numerical simulation taking into account vapor condensation. Since the particle size of aerosol is smaller than the wavelength of the earth radiation, it was thought that the temperature was not influenced by aerosol during the night. However it is also suspected that the night temperature is high due to the increase in aerosol diameter by condensation. The numerical simulation assumed that the aerosol consists of ammonium sulfate and that the aerosol's vertical concentration profile has the same pattern as that of the observed extinction coefficient of aerosol by Lidar. The simulation showed the temperature rise depends on the aerosol particle density, i.e., the rise in temperature at the aerosol particle density of 105/cm3 is 0.4 degree higher than that at 103/cm3. Since the aerosol particle density in an urban area is generally higher than that in a rural area, it is expected that the descent in the night temperature in the urban area is smaller compared to that in the rural. The heat island analysis carried out for Tokyo as an example revealed that the contribution of aerosol to the heat island is almost the same as that of anthropogenic heat.
The fiber biopersistence is an important factor in estimating the carcinogenicity and fibrogenicity of fibers. In order to explore the biopersistence of Japanese glasswools in the lung, we examined the clearance of deposited fibers in fibers-exposed rat lungs. The tested fibers were glasswools of GFA10 and GFA20 used conventionally in Japan, and CM44 as the control. Values of KNB (Index of Solubility) of GFA10, GFA20 and CM44 were 28.4, 30.3 and 26.74 respectively. Rats were exposed to 2 mg of each fiber intratracheally and sacrificed at 1, 3 days, 2 and 4 weeks after the instillation. The whole lung from the rat was ashed by O2 plasma reactor. The number of recovered fibers longer than 20 μm in rat lungs was counted using scanning electric microscope (SEM) , and the clearance half-times of fibers were calculated by single exponential regression of the fibers. The clearance half-times of fibers with length > 20 μm for GFA10, GFA20 and CM44 from the lung were 9, 8, and 6 days, respectively. The half-times of all glasswools are shorter than 40 days of the clearance half-times in short term biopersistence test by intratracheal instillation regulated by Directive 97/69/EU. SEM microphotographs revealed that recovered fibers had a rough surface and some thin fibers were curled as fibers with high solubility. Taken together, we established the short term biopersistence test by intratracheal instillation, and these data suggested that 2 Japanese glasswools might be biosoluble fibers in the lung.