Time and temperature dependent mechanical behavior of Al/Ti thin films application for MEMS

Abstract

Al-Ti alloy is widely used in MEMS components such as RF MEMS switches. When the moving part of MEMS components operating in higher temperature, such as switches and mirrors, their reliability is always an issue which needs to be focused. In order to manufacture a better reliable component, it is needed to clarify such mechanical properties of the materials. Here, we deposit four different kind of Al-Ti alloy films specimens by using sputtering system, and measured the mechanical properties of these films by using Bulge Test. The principle of Bulge Test is to add stress on Al-Ti alloy films from pressure differences, then used Position Sensing Detector(PSD) to measure the height of bulge that caused by the pressure. According to the relation between stress and the height of Bulge the mechanical properties can be measured. The experiment was divided into two parts which are stress-strain ramp tests and creep tests. The stress-strain ramp tests provided the Young's modulus and residual stress of the films and the creep tests were observed for the creep behavior of the films. In the stress-strain ramp tests, it shows that higher titanium content of the Al-Ti alloy film has higher Young's modulus. On the other hand, higher titanium content shows better creep resistance.