Measurement and control of impurity distribution in ultra pure gas delivery systems.

Persistent Link:
http://hdl.handle.net/10150/186380
Title:
Measurement and control of impurity distribution in ultra pure gas delivery systems.
Author:
Haider, Asad Mahmood.
Issue Date:
1993
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
As the integrated circuit technology evolves to a greater complexity, the purity of process gases becomes a critical issue requiring extreme diligence in gas handling. There are three major challenges in gas contamination control: Gas purification, gas transport, and metrology of contaminants. In the area of gas purification, a novel integrated purification/filtration technique is developed--the reactive filter. The fundamental concept of a reactive filter involves impregnating the surface of an efficient particle filter with chemically reactive sites. The technique is capable of purifying inert as well as reactive gases to sub parts-per-billion levels of atmospheric contaminants at ambient temperature. Development and evaluation results for the reactive filter are presented. In the area of gas transport, this work has experimentally and theoretically studied the fundamental mechanisms of various sources of impurity intrusion and the fate of impurities in an ultra-pure gas transport system. The contamination sources investigated include impurity adsorption and desorption from transport lines and gas filters, impurity back-diffusion, and impurity permeation through polymeric materials. Fundamental kinetic parameters for impurity adsorption/desorption in stainless steel tubes and ceramic and metallic filters are reported. The desorption kinetics expression developed assumes two energy levels for the desorbing species. A systematic filter outgassing data analysis and normalization technique is presented along with a computer code to simulate a simple gas delivery system. The back-diffusion study developed a mathematical model to predict the extent of back-diffusion for various contaminants in high purity gas lines. Back-diffusion is very sensitive to system pressure. Impurity permeation study was conducted on Kel-F and PFA polymeric tubes. The effect of both temperature and pressure on the permeation coefficients was investigated. In the area of metrology, state-of-the-art analytical tools and techniques like Atmospheric Pressure Ionization Mass Spectroscopy (APIMS) were employed to detect and measure trace impurity levels. APIMS has the advantage of short response times and low parts-per-trillion level detection limit for most impurities of interest.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic.; Chemical engineering.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemical Engineering; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Shadman, Farhang

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleMeasurement and control of impurity distribution in ultra pure gas delivery systems.en_US
dc.creatorHaider, Asad Mahmood.en_US
dc.contributor.authorHaider, Asad Mahmood.en_US
dc.date.issued1993en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractAs the integrated circuit technology evolves to a greater complexity, the purity of process gases becomes a critical issue requiring extreme diligence in gas handling. There are three major challenges in gas contamination control: Gas purification, gas transport, and metrology of contaminants. In the area of gas purification, a novel integrated purification/filtration technique is developed--the reactive filter. The fundamental concept of a reactive filter involves impregnating the surface of an efficient particle filter with chemically reactive sites. The technique is capable of purifying inert as well as reactive gases to sub parts-per-billion levels of atmospheric contaminants at ambient temperature. Development and evaluation results for the reactive filter are presented. In the area of gas transport, this work has experimentally and theoretically studied the fundamental mechanisms of various sources of impurity intrusion and the fate of impurities in an ultra-pure gas transport system. The contamination sources investigated include impurity adsorption and desorption from transport lines and gas filters, impurity back-diffusion, and impurity permeation through polymeric materials. Fundamental kinetic parameters for impurity adsorption/desorption in stainless steel tubes and ceramic and metallic filters are reported. The desorption kinetics expression developed assumes two energy levels for the desorbing species. A systematic filter outgassing data analysis and normalization technique is presented along with a computer code to simulate a simple gas delivery system. The back-diffusion study developed a mathematical model to predict the extent of back-diffusion for various contaminants in high purity gas lines. Back-diffusion is very sensitive to system pressure. Impurity permeation study was conducted on Kel-F and PFA polymeric tubes. The effect of both temperature and pressure on the permeation coefficients was investigated. In the area of metrology, state-of-the-art analytical tools and techniques like Atmospheric Pressure Ionization Mass Spectroscopy (APIMS) were employed to detect and measure trace impurity levels. APIMS has the advantage of short response times and low parts-per-trillion level detection limit for most impurities of interest.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academic.en_US
dc.subjectChemical engineering.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemical Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairShadman, Farhangen_US
dc.contributor.committeememberWendt, Jost O.L.en_US
dc.contributor.committeememberRandolph, Alan D.en_US
dc.contributor.committeememberO'Hanlon, Johnen_US
dc.identifier.proquest9408458en_US
dc.identifier.oclc720410551en_US
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