DECAY LENGTH OF THE PRESSURE-DEPENDENT DEPOSITION RATE FOR MAGNETRON SPUTTERING

The pressure dependence of the deposition rate for magnetron sputter d eposition of various elemental semiconductors and metals was investiga ted by x-ray measurements on sputtered films and quartz monitor measur ements. It was found that for all elements investigated the dependence of the rate Phi on pressure-distance (pd) is well described by Phi = Phi(0) (1 - e(-cpd))/cpd. The value of c equals the inverse characteri stic pressure-distance product (pd)(0), which is the characteristics o f the exponential decay of rate with pressure for low pressures. The e xperimental data of (pd)(0) vary from 4.6 Pa cm for aluminum to 120 Pa cm for tungsten. It is shown that (pd)(0) depend on both material spe cific properties and process parameters. The material specific propert ies are mainly the atomic mass and diameter, and the surface binding e nergy. The process parameters target voltage and power density act via the increase of the mean free path and the reduction of gas density, respectively, on (pd)(0). As a first approximation, the characteristic pressure-distance product for argon as sputtering gas is proportional to the product of target atomic mass, average atomic energy and therm al mean free path. (C) 1998 American Vacuum Society. [S0734-2101(98)05 504-3].