Abstract
With continuous miniaturization of very large-scale integrated circuits (VLSI), devices generate substantial heat during operation. A rapid increase in operating temperature causes serious reliability concerns and impacts on devices performance. Thin-film thermoelectric cooling devices own the advantages of large cooling power density、fast response time、stability and compatibility with semiconductor process technology. Thus, it becomes one possible solution to VLSI heat dissipation problem. The performance of the thermoelectric device depends closely on the figure of merit of the material. Bi2Te3 compound is known the best thermoelectric material at room temperature presently. In this study, Bi2Te3 layered compound was prepared by DC sputter deposition method. The Bi/Te bilayer thin films were first deposited on SiO2 substrate in sequence, and transformed into Bi-Te compound by thermal treatment through solid state reaction. The effect of Bi/Te thickness ratio on the thermoelectric properties of the Bi-Te composite thin films was investigated. In order to obtain the better planarization and adhesion for thin film integration considerations, the substrate temperature is maintained at room temperature. A Bi thin film annealing process was introduced to improve the thermoelectric properties of Bi-Te composite thin film. The effect of thermal annealing conditions on the microstructure and the thermoelectric properties of Bi-Te composite thin film was also investigated. It is observed that Bi-Te composite thin film has good planarization and poor thermoelectric properties caused likely by imperfect crystalline microstructure when the substrate temperature during deposition is room temperature. Therefore, we introduced an post-annealing step to reduce defects in Bi thin film, which shows a Seebeck coefficient of -78μV/K after 200℃/2hr annealing. According to the results for Bi/Te composite films with different Bi/Te thickness ratio, we speculated that the formation of Bi2Te3 composite retarded further interdiffusion between Bi and Te. Therefore, the residual Bi thin film affected the thermoelectric characteristic of Bi/Te composite thin film.