Reaction and Transport of Multiple Species During Plasma Etching
Folta, James Allen
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https://hdl.handle.net/2142/69798
Description
Title
Reaction and Transport of Multiple Species During Plasma Etching
Author(s)
Folta, James Allen
Issue Date
1988
Doctoral Committee Chair(s)
Alkire, Richard C.
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Engineering, Electronics and Electrical
Abstract
The nature of transport and reaction of multiple species in plasma reactors was analyzed in order to determine the effect of operating conditions and design variables upon the etch rate distribution and throughput. Epoxy and photoresist films on closely-spaced silicon wafers were etched by reactive species generated in a 13.56 MHz O$\sb2$/CF$\sb4$ plasma, which was confined from direct contact with the substrates. Additionally, epoxy drill smear was etched from the sidewalls of holes drilled in multilayer printed wiring boards.
Experiments were performed to examine the chemistry of the etching reactions in the absence of mass transport, followed by studies in which transport and reaction of the etchant species were coupled. Plasma and etching diagnostic techniques included X-ray photoelectron spectroscopy (XPS or ESCA), optical emission spectroscopy (OES), mass spectroscopy, and multi-channel laser interferometry. A mathematical model describing diffusion of etchant species and reaction at the substrate surface was formulated for comparison with the experimental results.
Experimental and theoretical results indicated that increased CF$\sb4$ content in the feed stream served to fluorinate the more-accessible regions of polymer to a greater extent than the less-accessible regions. Such behavior served to suppress the etch rate in the more-accessible regions and enhance the etch rate in the less-accessible regions, thereby improving etch rate uniformity and reactor throughput significantly, both for closely-spaced wafers and for the removal of epoxy drill smear from holes in printed wiring boards.
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