Effect of H2 Plasma Conditioning on Anodized Al Chamber and Quartz Discs
| dc.contributor.advisor | Donnelly, Vincent M. | |
| dc.contributor.committeeMember | Economou, Demetre J. | |
| dc.contributor.committeeMember | Nikolaou, Michael | |
| dc.contributor.committeeMember | Wolfe, John C. | |
| dc.contributor.committeeMember | Ruchhoeft, Paul | |
| dc.creator | Zhou, Yingliang | |
| dc.date.accessioned | 2022-06-29T22:29:50Z | |
| dc.date.created | May 2021 | |
| dc.date.issued | 2021-05 | |
| dc.date.submitted | May 2021 | |
| dc.date.updated | 2022-06-29T22:29:51Z | |
| dc.description.abstract | In this work, two projects related to semiconductor integrated circuit processing are investigated: (1) H2 plasma conditioning of anodized Al walls of a high density remote plasma source; (2) H2 plasma erosion and roughening of quartz discs. In the first project, experiments were performed in a high power-density (10 – 40 W/cm3), purely inductive plasma in an anodized-Al coated, transformer coupled toroidal plasma (TCTP) source at a pressure of 0.8 Torr. Optical emission spectroscopy was employed to monitor the time-resolved evolution of species from the walls. 4%H2/Ar or 3%N2/9%H2/Ar plasmas, alternated with Ar, O2/Ar or NF3/Ar “cleaning” plasmas were investigated. In Ar plasmas, the H-to-Ar intensity ratio decayed to base line in a stretched exponential manner over ~0.5-1.5 min, reflecting out-diffusion of hydrogen from the prior hydrogen-containing plasma exposure, with larger signals observed after longer exposure to the hydrogen-containing plasma. Compared to Ar plasmas, the amount of evolved hydrogen increases up to ten-fold in NF3/Ar plasmas, while it decreases five-fold in O2/Ar plasmas with no dependence on the duration of the hydrogen-containing plasma. It was shown that formation of HF and OH in NF3/Ar and O2/Ar plasmas does not significantly affect H Balmer- emission intensity, and that the enhancement or suppression is due to F and O impingement on and diffusion into the anodized Al. It is proposed that F reacts with H in the layer to for HF, which diffuses out of the film, while O reacts with diffusing H and binds it as immobile AlOH. A time-dependent 1-D diffusion model was developed, and reproduces most of the observed effects with a H and/or H2 diffusion coefficient that increases as a function of distance from the surface, ascribed to the columnar, porous nature of anodized Al. The second project presents a study of the erosion of SiO2 in the same TCTP. At 0.5Torr, quartz samples were exposed to plasma densities of 1-3 x 1013cm-3 and H atom temperatures of 4000-8000K. Short (e.g. 1 min) H2/Ar plasma exposure followed by long (9 min) plasma-off cool-down periods resulted in higher etching rates and increased erosion, compared to long (e.g. 1 hr) continuous plasma operation, and was ascribed to the higher substrate temperatures reached with continuous plasma operation and a negative dependence of the etching rate on temperature. When exposure to H2/Ar plasmas were alternated with O2/Ar plasmas and plasma–off periods, the etching rate was reduced to near-zero and surface roughness was much reduced. N2/Ar plasma treatments were less effective in reducing the etching rate, while surface roughness was nearly eliminated. A proposed mechanism involves penetration of H below the surface and insertion into Si-O-Si linkages to form SiH and SiOH groups, and crack propagation that leads to shedding of small silica particles. Periodic exposure to O atoms hydroxalizes sub-surface and reforms Si-O-Si linkages, and generates H2O that presumably desorbs. | |
| dc.description.department | Chemical and Biomolecular Engineering, William A. Brookshire Department of | |
| dc.format.digitalOrigin | born digital | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.uri | https://hdl.handle.net/10657/10184 | |
| dc.language.iso | eng | |
| dc.rights | The author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s). | |
| dc.subject | Plasma science and technology | |
| dc.subject | plasma etching processes | |
| dc.subject | surface reactions and plasma-surface interactions | |
| dc.subject | Plasma induced quartz erosion | |
| dc.subject | Laser inteferometry | |
| dc.subject | Atomic force microscopy | |
| dc.subject | Optical emission spectroscopy. | |
| dc.title | Effect of H2 Plasma Conditioning on Anodized Al Chamber and Quartz Discs | |
| dc.type.dcmi | Text | |
| dc.type.genre | Thesis | |
| local.embargo.lift | 2023-05-01 | |
| local.embargo.terms | 2023-05-01 | |
| thesis.degree.college | Cullen College of Engineering | |
| thesis.degree.department | Chemical and Biomolecular Engineering, William A. Brookshire Department of | |
| thesis.degree.discipline | Chemical Engineering | |
| thesis.degree.grantor | University of Houston | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy |
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