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Sputtering effects during 3D-imaging of
indium-tin-oxide sputtering targets
Reger N., Stadermann F. J., and Ortner H. M. (1998). In
Secondary Ion Mass Spectrometry, SIMS XI (ed. G. Gillen, R.
Lareau, J. Bennett, and F. Stevie), pp. 855-858. John Wiley
& Sons.
ABSTRACT
Thin layers of indium tin oxide are applied as electrical
contacts in flat displays since they are conductive and
optically transparent. Targets are coated with ITO by
reactive magnetron sputtering. A partially reduced
ITO-sputtering target is eroded by a Ar/O plasma. Sputtered
In and Sn atoms are oxidized within the plasma and
redeposited on the substrate. During the sputtering process
small nodules with diameters up to 100µm grow on the
surface of the sputtering target. These nodules cause small
arcs that destabilize the sputtering process. In addition
small particles are eroded from the surface and contaminate
the substrate. It is well known that inhomogeneously
distributed impurities with a lower sputtering yield than
the matrix may cause such nodule growth. In this study we
have used secondary ion mass spectrometry to determine: (1)
whether or not such inhomogeneously distributed impurities
can be found in the ITO-sputtering targets, (2) the
compositions of any impurities found, and (3) the influence
impurities have on the sputtering behavior. SIMS is one of
the few analytical methods being capable of acquiring 3D
images of elemental distributions and is, therefore,
particularly suited for this type of investigation. In
addition, the influence of impurities on sputtering behavior
should be directly seen in the count rates of secondary
ions.
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