Columnar microstructure and stress measurements in amorphous W0.75Si0.25 thin films

Abstract

Columnar microstructure has been observed in direct-current sputter deposited amorphous metal thin films of W0.75Si0.25. Transmission electron microscopy was used to examine the films, both in cross section and plan view. Individual columns are 50–150 Å in diameter and the morphology is typical of a zone 1 structure. In contrast, films of the same composition deposited by magnetron sputtering did not exhibit a columnar microstructure. The dc sputtered films were also found to be in tensile stress when deposited on silicon substrates. Measured stresses ranged from 6.5×108 Pa for 4000 Å films with a linear increase to 8×108 Pa for 33 000 Å films. For films thinner than 4000 Å the stress in the films dropped off rapidly. The linear increase in stress seen was attributed to mutual attractive forces between adjacent columns.