An investigation of hysteresis effects as a function of pumping speed, sputtering current, and O2/Ar ratio, in Ti-O2 reactive sputtering processes

Abstract

Understanding of mode transition and hysteresis behavior in reactive sputtering is necessary to widen its applications. The effects of physical pumping speed, sputtering current, and reactive/inert gas ratio on mode transitions and hysteresis in Ti-O2 dc reactive sputtering are examined. As O2 gas flow rate is increased or decreased, mode transition takes place as a consequence of the target poisoning or cleaning. The results obtained explain the important roles of pumping speed and sputtering current on hysteresis. Also, it is found that as pumping speed increases hysteresis width decreases. In addition, for smaller sputtering currents and constant pumping speed, hysteresis width shrinks. The change in transition points as a function of pumping speed and sputtering current are successfully explained by considering getter pumping capacity or getter pumping speed. Elimination of hysteresis is not investigated in this experiment. From the discussion it is suggested that hysteresis is a result of difference in sputtering yields from a poisoned target and from a metallic target, which provides a difference in gettering capacity.