Properties of hard tungsten films prepared by sputtering

Abstract

The structure and properties of sputtered tungsten films up to 28 μm in thickness are reported. Hardnesses of more than 1700 kg/mm2 have been obtained for these films, this being several times the value of bulk tungsten. It has been found that hardness can be varied by changing the pressure, bias voltage, or power during sputtering. The hardness of these films is approximately constant with temperature up to 500 °C, in contrast to the hardness of bulk tungsten which decreases with temperature. Grain size has been estimated from the line broadening of x-ray diffraction peaks and by transmission electron microscopy. It has been found that hardness and grain size follow the Hall—Petch relationship. © 1988, American Vacuum Society. All rights reserved.