Fabrication of C54-TiSi 2 Thin Films Using Cathodic Arc Deposition and Rapid Thermal Annealing

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1052-DD06-29

Fabrication of C54-TiSi2 Thin Films Using Cathodic Arc Deposition and Rapid Thermal Annealing Hui Xia1, William R. Knudsen2, and Paul L. Bergstrom1,3 1 Department of Materials Science and Engineering, Michigan Technological University, Houghton, MI, 49931 2 College of Engineering, Michigan Technological University, Houghon, MI, 49931 3 Department of Electrical and Computer Engineering, Michigan Technological University, Houghton, MI, 49931 ABSTRACT An enabling material for high density microelectronics technologies, C54-TiSi2 thin films can be used in many related integrated microsystem technologies to reduce the RC delay and improve the dynamic performance due to its low electrical resistivity and high thermal stability. In this paper, C54-TiSi2 thin films were prepared for the first time using cathodic arc deposition with rapid thermal annealing. The impact of energetic ion bombardment on the film microstructure and subsequent C49-C54 phase transformation during annealing were studied. The TiSi2 compound was used as the cathode material and substrate bias was varied to control the ion energy during the film growth. Rutherford backscattering spectrometry and transmission electron microscopy were utilized to characterize the film composition and microstructure. The composition of the resultant TiSix thin films varied from x=2.4 to x=1.4 when the substrate bias was varied from a floating self-bias to –200V. The films deposited at room temperature were amorphous with a phase separation at the nano scale. The Si atoms were seen to segregate on the boundary of Ti-rich domains and the domain size increased with the magnitude of the substrate bias. For a 90nm-thick TiSi2 film deposited on a SiO2/Si substrate, the kinetics of the C49-C54 phase transformation was studied by measuring the change of film resistivity upon rapid thermal annealing. It was found that the C49-C54 phase transition temperature was higher (>900°C) for the arc-deposited TiSi2 thin films compared to evaporated or sputtered films. The activation energy of the C49-C54 transformation was calculated to be 6.1±0.2eV. INTRODUCTION Due to its low electrical resistivity and high thermal stability, C54-TiSi2 is a promising material in some MEMS applications, such as RF MEMS, to reduce the RC delay and improve the dynamic performance. Compared to heavily doped polysilicon, C54-TiSi2 has a much lower resistivity (15–20µΩ⋅cm) and similar mechanical properties, thus it can serve as either a highly conductive coating or structural material in surface micromachining. C54-TiSi2 is usually prepared by annealing a thin layer of Ti in contact with Si substrates or through the crystallization of co-deposited amorphous TiSi2 thin films [1]. In both cases, the stable

orthorhombic face-centered C54-TiSi2 is formed through the phase transformation from a metastable orthorhombic base-centered C49-TiSi2 during high temperature annealing. The C49-C54 phase transformation is a critical step in the fabrication of C54-TiSi2 thin films and it has been reported to be

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