Study of interactions between α-Ta films and SiO₂ under rapid thermal annealing

The interactions between α-Ta films and SiO₂ after being annealed in the temperature range of 650-850 °C in Ar ambient have been studied using X-ray diffraction (XRD) and sheet resistance measurements. The thermal-induced products are dependent on the annealing temperatures. Under low temperature annealing, the α-Ta films are oxidized at the top and the bottom with increasing sheet resistance, and the oxygen source mainly comes from the annealing ambient and some which dissolved in α-Ta films. Free oxygen and silicon atoms released from SiO₂ substrate enhance the formation of Ta oxide and generate Ta silicides under higher temperature annealing. The formation of two kinds of Ta silicides depends on the quantities of Ta atoms and free Si atoms from SiO₂ at the interface. These interfacial reactions result in the increasing sheet resistance till the formation of dominate TaSi₂. The oxidized Ta(N) interlayer could play an additional barrier on the diffusion of Ta and released Si atoms to improve the thermal stability of α-Ta films.