Role of low-energy ion/surface interactions in controlling microstructure and texture evolution during film growth
Kim, Young-Woon
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https://hdl.handle.net/2142/22226
Description
Title
Role of low-energy ion/surface interactions in controlling microstructure and texture evolution during film growth
Author(s)
Kim, Young-Woon
Issue Date
1995
Doctoral Committee Chair(s)
Greene, Joseph E.
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Metallurgy
Engineering, Materials Science
Language
eng
Abstract
The effects on microstructure and microchemistry of ion irradiation during AlCu film growth on a-SiO$\sb2$ by two directional sputtering techniques--collimated magnetron sputter deposition (CMSD) and ionized magnetron sputter deposition (IMSD)--were investigated. Both sets of films have dense columnar microstructures with (111) preferred orientation (PO). IMSD layers exhibited competitive column growth showing an order of magnitude higher degree of (111) orientation with much smaller azimuthal spread. The IMSD films were tensile while the CMSD films were slightly compressive.
In order to investigate the role of low-energy ion/surface interactions in a more controlled way, I constructed a double-grid, electron-impact, ultra-high-vacuum compatible, low-energy primary-ion deposition (PID) source capable of operating with low-vapor-pressure materials and providing ion current densities $>$100 $\mu$A cm$\sp{-2}$ at d = 400 mm with beam energies of 5-100 eV.
Since the IMSD experiments showed that PO can be controlled by the primary-ion fraction in the growth flux, experiments were conducted to investigate the effects of Al self-ion irradiation in Al layers grown on a-SiO$\sb2.$ All films were strongly (111) with the degree of PO increasing with both increasing ion energy and ion/neutral flux ratio. The mosaicity decreased continuously from 10.6$\sp\circ$ to 2.2$\sp\circ$ as the ion energy E$\sb{\rm Al\sp+}$ increased from 0 to 120 eV. Changing E$\sb{\rm Al\sp+}$ after the formation of a continuous layer had minimal effect on subsequent film texture indicating that the degree of PO is controlled during nucleation and/or coalescence while local pseudomorphic forces dominate thereafter.
The use of PID buffer layers was also investigated for the heteroepitaxial growth of Ge on Si(001). Epitaxial Ge layers with no detectable ion-induced damage were obtained with $\rm E \sb{Ge\sp+}\le15$ eV at $\rm T\sb{s}\ge300\sp\circ C$ and $\rm E \sb{Ge\sp+}\le45$ eV at $\rm T\sb{s}\ge400\sp\circ C$. However, at lower T$\sb{\rm s}$ and/or higher E$\sb{\rm Ge\sp+},$ local amorphous regions were formed within a single-crystalline matrix. Using such buffer layers to partially absorb the Ge/Si mismatch stress, dislocation densities in Ge overlayers were decreased by an order of magnitude.
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