Introduction
The fabrication of thin film has attracted much attention for many applications such as microelectromechanical systems (MEMS), smart cards, and semiconductor. The fabrication of thin film includes two important processes: 1) deposition, 2) annealing. To obtain desirable properties of the thin film, annealing process is required for the fabrication of thin film. The increase of annealing temperature leads to the improvement in the crystal quality causing changes in its desired properties such as strength and reactivity. The surface morphology exhibits significant change at different annealing temperatures. It is known that the surface morphology is changed due to the change in crystallinity, roughness and grain size. [1] As shown in figure 1 and 2, the Atomic Force Microscope (AFM) measurement shows that the surface roughness of thin film increases with increasing temperatures. [2]
Figure 1. AFM surface roughness measurement at different annealing temperatures
Figure 2. Surface roughness change as a function of annealing temperature
Research has been focused on controlling the desirable thin film properties. Therefore to achieve control over the surface morphology, it is necessary to understand why the surface morphology is changed with annealing temperatures. Even though there are many physical models to describe this, our model is assumed that the surface morphology is changed due to the concurrent interface diffusion and migration of the surface. For this project, the Au (gold) thin film is used to simulate the surface morphology change at different annealing temperatures.
[1] W. Kim, Characteristics of LiCoO2 thin film cathodes according to the annealing ambient for the post-annealing process, Journal of Power Sources 134 (2004) 103-109
[2] Y. Fu, H. Du, S. Zhang, Y. Gu, Stress and surface morphology of TiNiCu thin films: effect of annealing temperature, Surface & Coatings Technology 198 (2005) 389– 394