Stress and resistivity control in sputtered molybdenum films and comparison with sputtered gold

Abstract

Dc bias sputtering has been used to obtain molybdenum films with total stress varying controllably from +10¹⁰to < −10¹⁰ dyne per sq cm. These results were obtained for films approximately 3000 Å thick sputtered onto thermally oxidized silicon at substrate-holder temperatures from 70° to 230°C, with dc bias as the major parameter. 1000 Å films exhibit an even greater range of stress. Bias and substrate-holder temperature control also permits minimization of resistivity which is correlated with the impurity content of the films. Electron microprobe analysis shows a high oxygen content for zero-biased films, which decreases with increasing negative bias, as does the resistivity. The argon (sputtering ambient) content of the films increases as the negative bias increases from −110 to −200 volts. These changes with bias are qualitatively what would be expected based upon the preferential resputtering of oxygen and upon the embedding of the more energetic argon atoms at higher bias. The stress level, resistivity, and impurity content of dc bias sputtered gold films exhibit much less variation with bias than for molybdenum films, which is consistent with the difference in oxide formation properties of the two metals.