SOLID-PHASE REACTIONS OF DIFFUSION-BARRIERS OF TI AND TIN TO COPPER LAYERS ON SIO2

Thin films of Ti and TiN interposed between the Cu layer and SiO2 are examined as a diffusion barrier as well as an adhesion-promoting layer for Cu metallization technology. Solid-phase reactions and/or interdi ffusion taking place in the Cu/Ti/SiO2/Si and Cu/TiN/SiO2/Si systems a re examined by X-ray diffraction and the depth profiling method using Auger electron spectroscopy and X-ray photoelectron spectroscopy. The reduction of SiO2 through the formation of Ti-oxides occurs at the Ti/ SiO2 interface even in the as-deposited Cu/Ti/SiO2/Si system. In addit ion to this, the formation of Ti5Si3 and interdiffusion which result i n the formation of Cu-Ti intermetallic compounds due to annealing at 4 50 degrees C are evident, and lead to intermixing of the whole system. The use of TiN instead of Ti drastically suppresses the reaction and interdiffusion, and the Cu/TiN/SiO2/Si system is stable even after ann ealing at 850 degrees C, though the incorporation of a small amount of Ti into the Cu layer is observed.