High-throughput resistivity apparatus for thin-film combinatorial libraries

An apparatus, capable of measuring the dc resistance versus temperature of a 49-member library prepared by thin-film deposition techniques was designed and tested. The library is deposited by dc magnetron sputtering onto 10.16 cm x 10.16 cm alumina substrates on which are placed aluminum masks consisting of 8 mm diam holes cut on a 7 x 7 grid, the center-to-center spacing being 10.15 mm. Electrical contact to the library is made in a standard van der Pauw geometry using 196 spring-loaded, gold-coated pins, four pins for each member of the library. The temperature is controlled using a helium refrigerator in combination with a liquid-nitrogen radiation shield that greatly reduces radiative heating of the sample stage. With the radiation shield, the cold finger is able to sustain a minimum temperature of 7 K and the sample stage a minimum temperature of 27 K. The temperature (27 - 291 K) dependent dc resistivity of a thin-film silver library of varying thickness (48 - 639 nm) is presented to highlight the capabilities of the apparatus. The thickness dependence of both the resistivity and the temperature coefficient of resistivity are quantitatively consistent with the literature. For thicknesses greater than about 100 nm, the room-temperature resistivity (3.4 mu Omega cm) are consistent with Matthiessen's rule for 1% - 2% impurity content, and the temperature coefficient of resistivity is consistent with the bulk value. For thicknesses less than 100 nm, an increase in resistivity by a factor of 8 is found, which may be due to surface and boundary scattering effects; a corresponding increase in the temperature coefficient of resistivity is consistent with a concomitant decrease in the magnitude of the elastic constants and surface scattering effects. (c) 2005 American Institute of Physics.