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" Fundamental study of clean rooms "
S. M. R. Sadjadi
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1112612
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| Doc. No
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TLpq303870751
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| Main Entry
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S. M. R. Sadjadi
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| Title & Author
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Fundamental study of clean rooms\ S. M. R. Sadjadi
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| College
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University of Minnesota
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| Date
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1990
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| student score
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1990
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| Degree
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Ph.D.
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| Page No
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265
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| Abstract
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Several critical issues affecting the operation of new generation of cleanrooms are studied. Methods are suggested for predicting major sources of contamination in cleanrooms. Finally, a computer code is developed to predict contamination levels in a cleanroom. This code can be used as a tool in cleanroom design. The subject of detection of leaks in filters has been ignored for several years. Today's semiconductor industry requires extreme levels of cleanliness inside their fabrication factories. At the present time, contamination levels of less than 1 particle/ft of particles larger than 0.1 mum in diameter is required. Leading manufacturers in the industry require removal of particles larger than 0.05 mum, and in next several years, this limit will be pushed down to 0.01 mum. As a result, even minute amounts of very small particles near fabrication area can be detrimental to successful production of high speed, and high density micro-circuits. Undetected small leaks in HEPA (high efficiency particulate air) or ULPA (ultra low penetration air) filters is a very important contamination source. Behavior and characteristics of pin-hole leaks are studied theoretically and experimentally. Instruments and necessary procedures are developed for detecting leaks as small as 2 mum in diameter. In the so-called VLF (vertical laminar flow) clean room, it is desired that the air flow be unidirectional, and uniform across the entire ceiling grid. The effect of plenum geometry on air flow uniformity in clean rooms is studied experimentally and in theory. A new realistic numerical approach to the problem of flow distribution in cleanrooms is developed. Ambient aerosol penetrating through the filtration system of cleanroom is the major source of particles smaller than 0.2 mum inside cleanrooms. A method is suggested for predicting ambient aerosol concentrations theoretically. This model is verified using available data collected since 1960's, for four different locations in the western, southern, southwestern, and northern parts of the United States. A representative sample of typical particle generation rate, and distribution for particles larger than 0.01 mum, by people inside cleanrooms is collected. Finally, a computer program is developed. This program can predict the performance of a cleanroom as a function of several different variables including ambient aerosol, HEPA, and ULPA filters, pre-filters, leak flow rates, dimensions of cleanroom, air recirculation rate, total air flow rate, and contamination sources originating inside cleanrooms.
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Aerosols
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Applied sciences
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Leak detection
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Mechanical engineering
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