The concentrations and characteristics of major components in inorganic gases and fine particles were measured at the photo and etch cleanroom areas in a Taiwan semiconductor factory. The results showed that the major inorganic gases, as expressed in terms of volume concentration, were NH 3 and HF at 7-10 and 4-6 ppbv, respectively. The average PM 2.5 mass concentration were 17.52 and 18.23 μg/m 3 at the photo and etch areas, respectively, with species of Na + , NH 4 + , Cl -and SO 4 2-had the highest concentrations in the PM 2.5 mass. And the inorganic species account for 56% and 62% of the particulate mass, respectively, at the photo and etch areas. Relatively stronger correlations were observed between NH 4 + and SO 4 2-with the correlation coefficient R 2 of 0.62 and 0.82, respectively, at the photo and etch areas; this indicates their common source was possibly from the gas to particle formation process. And NH 3 was found to co-exist with HF at the etch area due to their common source as process chemicals (NH 4 OH and HF) in the wet bench. In the predominant NH 3 -rich environment, ammonia is the basic neutralizing agent to form the ammonium aerosol in a cleanroom.
The adsorption and desorption behaviors of ionic micro-contaminants on the silicon wafers in a cleanroom environment were investigated in this study. The experimental measurements showed that the surface density of ionic contaminants was significantly affected by both the exposure time and the properties of contaminants. The rate parameters of a kinetic model for surface deposition were determined by numerical optimization of fitting the experimental data on surface and ambient concentrations of airborne molecular contaminants (AMCs). Subsequently, the time-dependent deposition velocity and sticking coefficient of ionic species were obtained. The results showed that F , Cl , NO 3 , SO 2 4 , Na + , NH + 4 , K + , and Mg 2+ were the major ionic microcontamination species on the wafer surfaces, with the adsorption rate constant and the sticking coefficient of K + ion being larger than those of other ionic contaminants.After the determination of sticking coefficients, the allowable wafer exposure durations and the maximum ambient concentrations of ionic species were exemplified based on the guideline recommended by the International Technology Roadmap for Semiconductors (ITRS).
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