Sinter-patterning of oxide dielectric and high critical transition temperature films by pulsed neodymium:YAG laser
Louh, Rong-Fuh
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https://hdl.handle.net/2142/21337
Description
Title
Sinter-patterning of oxide dielectric and high critical transition temperature films by pulsed neodymium:YAG laser
Author(s)
Louh, Rong-Fuh
Issue Date
1991
Doctoral Committee Chair(s)
Buchanan, Relva C.
Department of Study
Materials Science and Engineering
Discipline
Materials Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
Using metallo-organic precursors formulated based on metal carboxylates, various oxide dielectric films (ZrO$\sb2$, Y$\sb2$O$\sb3$ yttria stabilized zirconium (YSZ)), perovskite based oxide films (BaTiO$\sb3$, SrTiO$\sb3$, CaTiO$\sb3$, YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$), and Bi$\sb4$Ti$\sb3$O$\sb{12}$ film were fabricated by spin coating onto single crystal substrates such as Si, ZrO$\sb2$ and MgO.
Different microstructures and line patterns were generated by varying the laser pulse energy level and profile. Laser processing parameters, deposited film thickness and organic burn-off showed strong influence on the film densification behavior in terms of grain size development and pore elimination. With changes in input pulse energy and focusing conditions, the laser beam was also used to sinter line patterns in several deposited thin and thick films. Tighter pore size distribution was found with the focused condition.
Basically, the optimal focusing conditions used for laser sintering of different patterns (such as areas, lines, or dots) was found to depend on the spacing between the adjacent sintered spots and on the pulse energy. With laser irradiation at energy densities higher than the threshold value, liquid phase recrystallization, caused by rapid quenching of the oxide films from high temperature was formed from increasing energy density or the laser beam dwell time. Densification of the thin films by laser beams of different wavelength (Nd:YAG and ArF excimer lasers) was found to give rise to similar results, indicating that laser sintering of the pyrolyzed carboxylate-derived films is primarily controlled by photothermal rather than by photochemical effects.
The high T$\sb{\rm c}$ films patterning by this technique were found to exhibit high T$\sb{\rm c}$ properties comparable to other techniques. The results of magnetic SQUID measurement show the laser patterned YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$ films on ZrO$\sb2$/Si substrates to exhibit T$\sb{\rm c}$ above 80 K and $\Delta$T$\sb{\rm c} \sim$ 3K. Dielectric properties of laser-sintered BaTiO$\sb3$ and Bi$\sb4$Ti$\sb3$O$\sb{12}$ films were observed to be approximately the same as those of film specimens processed by rapid zone firing. This laser process has thus been shown to offer significant potential for thin film patterning, a technique which can be applied to both insulation and passivation uses in integrated circuit devices and packages. (Abstract shortened with permission of author.)
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