The effect of substrate temperature for internal stress on sputtered thin film

Abstract

In our recent research, it was found that the effects of ion bombardment for thin films can be estimated using the ion bombardment parameter Pi. Internal stress in sputtered thin films can be classified into thermal stress and true stress. In this study, the internal stress in thin films was evaluated by the changes in evaporant sources (Ni or Al), substrate (Si or glass), and substrate temperature during the deposition. Internal stress in thin films with ion bombardment as a part of true stress was controlled by plasma diagnostics. Thermal stress in the thin films was evaluated from the thermal expansion coefficient of the films and the substrate with the changing substrate temperature during thin film deposition. It was found that internal stress of the films was strongly dependent on thermal stress. Despite the control of ion bombardment by plasma diagnostics, the values of true stress for the films were not continuous. This suggests that in addition to ion bombardment, true stress is also governed by microstructural changes with changing substrate temperature.