Effects of Ti addition on the morphology, interfacial reaction, and diffusion of Cu on SiO2

In this work, thin films of pure Cu, and Cu with 0.02 or 2.98 wt % Ti were deposited on SiO2 covered Si substrates. The samples were annealed at 500–800 °C in vacuum to investigate their morphological evolution, interfacial reaction, and diffusion. X-ray diffraction reveals Cu(111) and Cu(200) peaks for pure Cu and Cu(0.02 wt % Ti) films. However, the Cu(2.98 wt % Ti) film exhibits a very weak Cu(200) peak, indicating that this film is textured in 〈111〉 orientation. Concurrently, scanning electron microscopy shows that the grain size of the Cu(2.98 wt % Ti) film is significantly smaller than those of pure Cu and Cu(0.02 wt % Ti) films. In addition, Cu(2.98 wt % Ti) film remains smooth after annealing up to 800 °C, while the other two films become discontinuous. X-ray photoelectron spectroscopy indicates that a TiOx layer has formed at the Cu(0.02 wt % Ti)/SiO2 and Cu(2.98 wt % Ti)/SiO2 interfaces after 700 °C annealing. Nevertheless, the TiOx layer is thicker in the Cu(2.98 wt % Ti) system than in the Cu(0.02 wt % Ti) system. Consequently, the Cu(2.98 wt % Ti) film shows no diffusion of Cu into SiO2 at temperatures up to 700 °C. Connections between the segregation of Ti addition and the morphological/interfacial characteristics are discussed.