Barrier properties and failure mechanism of Ta–Si–N thin films for Cu interconnection

Cosputtered Ta–Si–N amorphous films of ten different compositions were investigated as a barrier material for Cu interconnection. The films of relatively low nitrogen content (<47 at. %) undergo an abrupt failure with the formation of tantalum silicides and copper silicide between Si and Cu during annealing. ${\mathrm{Ta}}_{\mathrm{43}}{\mathrm{Si}}_{\mathrm{4}}{\mathrm{N}}_{\mathrm{53}}$ thin film is readily crystallized into ${\mathrm{TaN}}_x$ in spite of a remarkable chemical stability with Cu. The films containing nitrogen more than 51 at. % are sacrificial barriers which show the formation of ${\mathrm{Cu}}_{\mathrm{3}}\mathrm{Si}$ phase at Ta–Si–N/Cu interface even before the films crystallize to form tantalum silicide. According to electrical tests, the barriers which show the sacrificial characteristics are most effective and show no electrical degradation even after annealing at $\text{500\hspace{0.17em}°}\mathrm{C}$ for an hour in Si/Cu and $\text{525\hspace{0.17em}°}\mathrm{C}$ for an hour in ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/Cu}$ metallization.