INFLUENCE OF A DC SUBSTRATE BIAS ON THE RESISTIVITY, COMPOSITION, CRYSTALLITE SIZE AND MICROSTRAIN OF WTI AND WTI-N FILMS

The influence of a d.c. substrate bias on the properties of WTi and WT i-N films deposited by r.f. magnetron sputtering has been studied. The bias voltage was varied from 0 to -200 V. The WTi films structure is b.c.c. W with the presence of the h.c.p. Ti phase at low bias (0 to -5 0 V). For the WTi-N films, the structure is f.c.c. TiN at low bias and b.c.c. W+f.c.c. TiN at high bias (-100 V to -200 V). Both films exhib it the columnar morphology. The titanium fraction in the films is lowe r than in the target and decreases when the bias increases owing to a titanium preferential resputtering caused by the ion bombardment of th e substrate. The same behaviour is found for the film resistivity whic h diminishes when the bias is increased whereas the crystallite size i ncreases. The microstrains have a more complex variation with the bias .