Ta as a barrier for the Cu/PtSi, Cu/Si, and Al/PtSi structures

Abstract

The effect of Ta as a barrier is studied for the Cu-PtSi, Cu-Si, and Al-PtSi reactions. Using Cu/Ta/PtSi structure, an extensive mixing among Cu, Ta, and PtSi is observed around 300 °C, with both an increase in the sheet resistance and detection of Cu silicides. Comparison with the reactions of Cu/Ta/Si and Al/Ta/PtSi structures helps in understanding the mechanisms involved. The Cu/Ta/Si structure also shows mixing at 300 °C, and the Al/Ta/PtSi at 450 °C. The work indicates that, for the Cu/Ta/PtSi structures with and without barriers, Cu penetrates through the Ta layer to react with PtSi and Si, forming Cu silicides, releasing Pt for outdiffusion, and diluting the unreacted PtSi. The high affinity of Cu toward Si is suggested to play a major role in such reactions, which is consistent with the work using other barrier materials for the Cu/PtSi/Si structures, including amorphous carbon. © 1990, American Vacuum Society. All rights reserved.