High density diffusion barrier of ionized metal plasma deposited Ti in Al-0.5%Cu/Ti/SiO2/Si structure

The Ti layer deposited by ionized metal plasma deposition technique and the reacted region between Ti and Al-0.5%Cu, in Al-0.5%Cu/Ti/SiO2 /Si structur e, were characterized by scanning transmission electron microscopy (STEM) a nd Rutherford backscattering spectroscopy (RBS). The results indicate that the Ti layer with a column-like structure grew epitaxially in the close-pac ked [001] direction. This growth mechanism resulted in a high-density Ti la yer in Al-0.5%Cu/Ti/SiO2/Si structure. This epitaxially grown Ti layer has anisotropic diffusion properties that can retard the diffusion of Al across the Ti layer in the initial stage of high temperature Al sputtering or ref low processes. But the column-like Ti crystals recrystallized during furthe r processing, altered the [001] alignment of the crystals to cause the inte rdiffusion of Ti and Al. The reactions between Ti and Al took place subsequ ently and formed the intemetallic Al3Ti, Al5Ti2, TiAl, and Ti3Al layers fro m the surface inwards. As the diffusion of Al in Ti, Ti3Al, and TiAl decrea sed in order, the formation of Ti3Al and TiAl layers further retarded the d iffusion of Al into the SiO2 layer. It can be concluded that the intermetal lic layers play an important role of diffusion barrier that impede the migr ation of Al across the films. (C) 2001 American Vacuum Society.