Composition of thin films deposited by magnetron sputtering of a CuSn alloy target

Abstract

Copper-tin thin films have been deposited at different substrate temperatures in the range 300–1200 K by magnetron sputtering of a planar circular alloy target Cu-7.8 wt%Sn at Ar pressure 0.8 Pa, discharge voltage 650 V and discharge current 0.8 A. The sputtering region is an annular zone with radii 40 mm and 80 mm. The concentration of Sn in the deposited films decrease in two steps, with essentially different rates, as the substrate temperature increases: low temperature decrease inthe range 300–800 K and high temperature decrease in the range 900–1200 K. A simple phenomenological model for the alloy sputtering and deposition has been proposed. According to this model the sticking of Sn atoms to the surface of the growing film occurs via a preliminary trapping in loosely bound states. Low and high temperature decrease of Sn concentration has been explained considering two loosely bound states. Activation energies 0.12 eV and 1.21 eV have been obtained for desorption of Sn atoms trapped at these states.