Ta thin film resistors reactively sputtered onto substrates mounted on a rotating carousel

Ta thin film resistors have been reactively sputtered in 1.5×10^–5 Torr oxygen and 1.5×10^–5 Torr nitrogen simultaneously, using a d.c. diode system in which the anode is formed by a carousel. The substrates are mounted on this carousel and can be rotated through the discharge. For non-heat-treated films the resistivity increases and the TCR becomes more negative as the carousel rotation speed increases. These changes in electrical properties are attributed to the observed increase in the oxygen concentration and a simultaneous decrease in the nitrogen concentration in the films. The electrical properties are further perturbed by an elongation of the physical structure of the films as a result of carousel rotation. This elongation, which can produce an increased resistivity for a given TCR, is attributed to oblique incidence effects as the substrate rotates into, and out of the discharge. Changes produced in the electrical and structural properties of the films during heat-treatment at 500 C are shown to depend on carousel rotation speed: recrystallization and surface oxidation occur for films deposited onto a rotating carousel, whereas films deposited onto a stationary carousel undergo surface oxidation only, as indicated by the kinetics of the conductance change and the lack of structural changes as shown by transmission electron microscopy.