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M. Grosser, U. Schmid:
"Influence of Back Pressure and Plasma Power on Grain Size, Phase Composition and Resistivity of Tantalum Thin Films";
Vortrag: SPIE Europe: Microtechnologies for the New Millennium, Dresden, Deutschland; 04.05.2009 - 08.05.2009; in: "Proceedings of SPIE", Society of Photo-Optical Instrumentation Engineers (SPIE, 7362-7366 (2009), 8 S.

We determined the growth rate, electrical performance and morphology of tantalum (Ta) thin films in a wide range of back pressure (i.e. 0,003-0,06 mbar) and plasma power Pp (i.e. 100-900 W) levels at nominally unheated substrate conditions during deposition. First, Ta thin films with nearly constant thickness (mean value: 230 (±50) nm) were deposited by varying the sputter time in dependence of the plasma power. Next, we increased the sputter time at constant
plasma power to demonstrate that we get a higher resistivity with increasing film thickness as well as at high back pressures when depositing Tantalum predominantly in the beta phase. Doing so, the resistivity of the tantalum thin films can be tailored over two decades at constant film thickness only by tuning these important deposition parameters. Furthermore, X-ray diffraction (XRD) measurements showed a decreasing grain size at samples with a higher resistivity proving the physical basis of this finding. All results can be explained based on the variation in microstructure of the thin
films at different deposition parameters such as the grain size. Furthermore, when knowing the growth rate (i.e. film thickness and sputter time) the corresponding microstructure present in the Ta thin films can be estimated.

Tantalum, sputtering, porosity, structure, electrical resistivity

http://dx.doi.org/10.1117/12.821332