Atomic Absorption Spectroscopy: An In Situ Diagnostic for Sputter Deposition of Y-Ba-Cu-Oxide
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ATOMIC ABSORPTION SPECTROSCOPY: AN IN SITU DIAGNOSTIC FOR SPUTTER DEPOSITION OF Y-BA-CU-OXIDE G. METZGER, A. J. BLAIR, and C. B. FLEDDERMANN Center for High Technology Materials, University of New Mexico, Albuquerque, NM 87 131. ABSTRACT Atomic absorption spectroscopy (AAS) has been used as an in situ diagnostic tool to study sputtering of high-temperature superconductors. Hollow-cathode lamps were used as line sources to measure relative atomic species concentrations during sputtering of Y-Ba-Cuoxide targets using a Kaufman ion gun. The AAS measurements showed that the fluxes of ground state Ba and Cu ejected from a composite target during argon- and oxygen-ion bombardment varied greatly with sputtering parameters. Measurements were made of the effects of changes in ion-beam energy, ion flux to the target, and target temperature. In addition, the variation in atomic densities of Ba and Cu with distance from the target were measured. For comparison, AAS measurements during argon- and oxygen-ion sputtering of a pure copper target were also performed. The AAS results were verified by measuring stoichiometry variations of thin films deposited under identical conditions. INTRODUCTION Sputter deposition is a widely used technology for depositing a variety of thin films encompassing many different technologies (rf sputtering, magnetron sputtering, ion-beam sputtering, etc.) and several different types of materials (insulators, optical coatings, etc.) Development of detailed understanding and process control of sputtering are hampered by the lack of suitable, real-time, in situ diagnostics. Emission spectroscopy on the sputtered particles has been used for this purpose for a variety of materials [I], and has also been applied to the deposition of high-temperature superconducting thin films in rf sputtering [2] and in ion-beam sputtering [3-51. Although it is easily implemented, emission spectroscopy suffers from the disadvantage that the species accessed are those that have been sputtered from the target in an excited state, or (for rf sputtering) have been excited in the plasma. In the absence of detailed knowledge of the excitation mechanisms in the target and the plasma, detection of excited species yields little information about the sputtering processes taking place at the target. In addition, it is difficult to obtain quantitative information about species densities from emission spectroscopy. By far, the most numerous species ejected from the target are ground state atoms [I) which are not measured in emission experiments. Atomic absorption spectroscopy overcomes these limitations by providing a means for monitoring ground state atoms, yielding a more accurate picture of the sputtering process. In this paper, the use of atomic absorption spectroscopy for detecting ground state atoms ejected from a Y-Ba-Cu-oxide target by ion-beam sputtering is discussed. ATOMIC ABSORPTION SPECTROSCOPY
Absorption spectroscopy utilizes the absorption of light from a broadband or line source as it traverses an absorbing medium to det
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