Temperature effect on the mechanical properties of gold nano films with different thickness

The microelectronic industry has been growing rapidly over the past 10-20 years, as has its reliance on thin-film deposition techniques for components manufacturing. As modern devices generate quite a bit of heat and peak temperatures can reach over 100°C, there is a need to provide adequate cooling for a device to stay operable. A series of chrome gold films with various thicknesses were prepared on silicon substrate. The structural and surface morphology, adhesion, friction, Young's modulus and hardness of this thin film were studied for three different thicknesses under temperature variations between 20 to 100°C. The variation of the film thickness and temperature affects the structure, surface and mechanical properties of Cr/Au thin films. Obviously these thermal cycles are unavoidable and eventually lead to thermal fatigue damage and device failure. Consequently, the knowledge of mechanical properties of thin films at elevated temperatures is required for proper chip design and reliability assessments. Elastic modulus and hardness are two important mechanical properties of the thin-film structural materials used in microelectromechanical systems. The mechanical properties of electroplated chrome-gold thin film are found to be highly dependent on the manufacturing process and also of the thin film thickness. On the other hand it is important to find the effect of temperature on these properties. Investigated samples are made of thin layers of chromium and gold with differences in thickness. The three levels of nominal thicknesses of Au films are: 100, 300 and 500 nm. In order to obtain the relations between surface pattern/surface chemistry and nanotribological properties and adhesive behaviors of the films were evaluated with a noise- and vibration-isolated and environment-controlled XE 70-AFM from Park Systems, using the contact mode. The tests were performed at temperatures between 10°C - 100°C and at a relative humidity RH of 40%. Each measurement was repeated many times in order to improve the accuracy of the experimental results.