The diffusion barrier properties of 100nm-thick films, in the as-deposited or annealed condition, were investigated in a Cu/TiN/Si metallization system by using sheet resistance measurements, etch pit techniques, X-ray diffractometry, and cross-sectional transmission electron microscopy. No reaction of the Cu with the TiN layer was observed during exposure to temperatures of up to 650C for 1h. Secco etching of the Si surface revealed etch pits after annealing (550C, 1h). Cross-sectional transmission electron microscopic analysis showed that the in-diffusion of Cu resulted in the formation of dislocations in the Si substrate along the projection of the Si (111) plane, with precipitates (probably Cu silicides) around the dislocation. Considerable densification of the TiN films was obtained by annealing (450C, 0.5h, N2). In the case of an Al/TiN/Si system, it was shown that the barrier properties were enhanced by annealing the TiN before Al deposition. In the case of the Cu/annealed-TiN/Si system, the post-annealing temperature at which etch pits were first observed was still 550C, and the size and density of the etch pits were similar to those in the case of as-deposited TiN. It was concluded that annealing of the TiN film did not enhance its diffusion barrier properties in the Cu/TiN/Si system to the same extent as it did in the Al/TiN/Si system.

K.C.Park, K.B.Kim: Journal of the Electrochemical Society, 1995, 142[9], 3109-15