Laser Rapid Sintering of Metallo-Organic Derived Oxide Films
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LASER RAPID SINTERING OF METALLO-ORGANIC DERIVED OXIDE FILMS. Rong-Fuh Louh and Relva C. Buchanan, Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801
ABSTRACT Oxide films of ZrO2 , Y20 3, yttria stabilized zirconia (YSZ), and high Tc superconducting YBa2Cu3O7-x and Bi-Sr-Ca-Cu-O films were produced by spin coating metallo-organic precursors onto Si, ZrO 2 and MgO single crystal substrates. Densification of these oxide films, after pyrolysis of organic constituents, was achieved by scanning a Nd:YAG laser beam across the film surface. Surface morphology, microstructures, spatial grain size distribution, compositional variations, defects and physical properties of laser sintered films were characterized using SEM, EDS, TEM, SIMS, XRD and 4-point electrical resistivity probe. Laser processing parameters, deposited film thickness and organic bum-off showed strong influences on the film densification behavior. This paper focuses on pursuing optimum conditions for obtaining dense, uniform sintered patterns in oxide films and on understanding the film-substrate interaction and dynamics of nucleation and growth via the laser rapid sintering process. I. INTRODUCTION Single shot pulses from a Nd:YAG laser have been successfully used to generate different sized via holes and patterns in unfired ceramic sheets (e.g. BaTiO 3) for electronic packaging applications 11,21. The laser power could also be controlled to generate structures such as via channels or to sinter selected areas in the green sheets. With changes in pulse energy level and profile, the laser beam can also be used to sinter line patterns in several deposited thin oxide films. Laser direct writing is a one-step, mask-free process to produce patterns of different geometry in various types of thin films. Previous work of laser direct writing on thin films include laser-induced chemical vapor deposition (LCVD) for depositing conductor lines such as Au, Cu, and Ag on semiconductors 13-51 or silicon ribbon sensors 161,and laser-induced ablation and etching to produce patterns in ferroelectric films and high Tc superconducting films 17,81. Laser sintering of thick oxide films was demonstrated by Mitsuishi and coworkers using a ruby laser to sinter VO thick films on A120 3 substrates 19,101. More recently CO2 laser was used in the process of sintering BaTiO 3 green sheet to attain high density in much shorter firing time, compared to conventional means 111. Laser induced sintering and densification of thin films is analogous to the rapid thermal annealing (RTA) which has been widely employed in the microelectronic industry. In our work selective patterning and densification of metalloorganic derived oxide films were carried out by rapid laser sintering with a laser beam Mat. Res. Soc. Symp. Proc. Vol. 201.
1991 Materials Research Society
526
deflection system. In laser rapid sintering, microstructure development in the film is controlled by the initial nuclei density and the coalescence of nuclei into islands. Densification is
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