Use this URL to cite or link to this record in EThOS: | https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680121 |
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Title: | Harnessing the non-linear coupling of odd harmonics for control of charged particle dynamics in radio-frequency plasmas | ||||
Author: | Gibson, Andrew Robert | ||||
Awarding Body: | Queen's University Belfast | ||||
Current Institution: | Queen's University Belfast | ||||
Date of Award: | 2015 | ||||
Availability of Full Text: |
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Abstract: | |||||
Over the past number of years multiple frequency capacitively coupled plasmas have achieved widespread
usage in plasma based nano-fabrication. However,the control of charged particle dynamics in such
discharges is often limited by poor understanding of the non-linear coupling between the frequencies used.
This is particularly true for plasmas produced in molecular gases. such as oxygen. where long-lived reactive
neutral species can significantly affect the dynamics of charged particles. As these gases are used
frequently in industry. it is crucial to achieve better understanding of their characteristics under multiple
frequency excitation.
In order to understand the dynamics of non-linear frequency coupling. this work proposes a novel dual
frequency excitation scheme utilizing odd harmonics. The odd harmonic approach has been studied
systematically utilizing both numerical simulations and experiments in plasmas produced in molecular
oxygen gas. Through these Investigations it has been demonstrated that the frequencies used and the ratio
to which they contribute to the resultant voltage waveform have significant influence over the final plasma
parameters. This occurs through electron heating and ionization mode transitions which are non~linearly
dependent upon the frequency contributions to the overall voltage waveform.
A specific scheme for controlling the ion bombardment energy and ion flux to the substrate in Industrial
plasma applications. using frequencies of 13.56 MHz and 40.68 MHz has been proposed. It has been
predicted. through numerical simulations. and confirmed through experimental measurements. that the
proposed scheme offers enhanced control of plasma properties over a wide parameter range. Furthermore.
a critical benchmark study has been performed by undertaking a quantitative comparison between the
results of state-of-the-art numerical simulations and experimental data. This has identified areas where
further improvement in the understanding and modelling of oxygen plasmas is required in order to utilize
numerical simulations in a truly quantitative manner for process design and control.
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Supervisor: | Not available | Sponsor: | Not available | ||
Qualification Name: | Thesis (Ph.D.) | Qualification Level: | Doctoral | ||
EThOS ID: | uk.bl.ethos.680121 | DOI: | Not available | ||
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