HIGH-RESOLUTION AND ENERGY-FILTERING TEM STUDY OF INTERFACIAL STRUCTURE AND REACTION IN ADVANCED MATERIALS PROCESSING

High resolution TEM becomes more powerful when coupled with a Gatan im aging filler (GIF). It gives both structural and compositional informa tion simultaneously with subnanometer and nanometer resolution. respec tively. By means of these combined techniques, the failure mechanism o f diffusion barrier layers in IC devices, having the structure of Al-1 %Si-0.5%CuiTiNITi/Si substrate, was investigated. In non-oxygen stuffe d samples thermally stressed at 550 degrees C for 1 h serious Al spike s below contacts were observed where metal layer Ti also reacted with Si substrate to form C49-TiSi2 and was consumed completely. TiN and Al become unstable due to high temperature thermal stress and reacted in to TiAl3 and AlN. Decomposition of TiN degraded the function of the ba rrier layer, and so a diffusion path at the weakest point of the conta ct corner was opened for metal Al alloy to diffuse through the barrier layer and to form a spike below the TiN layer. We also showed that th e oxygen-stuffing processes after each TiN/Ti deposition enhances the barrier capability against Al/Si diffusion in thermal stress. It was f ound that Ti and TiN were oxidized to form titanium oxide which reacte d with the Al alloy. As a result, Al2O3 and TiAl3 were found above the TiN layer. Therefore, it is concluded that oxidation during oxygen-st uffing processes provides a means to inhibit diffusion in thermal stre ss processes, and maintains integrity of the stack structure. (C) 1998 Acta Metallurgica Inc.