Thermomechanical Behavior of Tantalum Thin Films: The Effects of Oxygen and the β–α Phase Transformation

Abstract

ABSTRACTβ-Ta films were prepared in an ultra-high vacuum sputter deposition system, and the stresses that arose during thermal cycles to 750° C were measured using an in situ substrate curvature measurement system. The oxygen content in the environment was controlled during both deposition and thermomechanical testing. In films with no added oxygen, phase transformation from β to α takes place in distinct “jumps.” Addition of controlled amounts of oxygen to the annealing atmosphere led to increases in compressive stress, inhibited the phase transformation, and altered the magnitudes of the “jumps” in stress. The stresses in Ta films were found to be sensitive to oxygen content as well as thermal history.