EFFECT OF ANNEALING OF TITANIUM NITRIDE ON THE DIFFUSION BARRIER PROPERTY IN CU METALLIZATION

The diffusion barrier properties of 100 nm thick TiN films, both as deposited and annealed, were investigated in the Cu/TiN/Si metallization system using sheet resistance measurements, etch pit observation, x-ray diffractometry, and cross-sectional transmission electron microscopy (XTEM). No reaction of the Cu with TiN layer was observed up to 650 degrees C for 1 h. However, by Secco etching of the Si surface, etch pits were first observed after annealing at 550 degrees C for 1 h. XTEM analysis shows that the in-diffusion of Cu results in the formation of dislocations in the Si substrate along the projection of Si {111} plane and precipitates (presumably Cu silicides) around the dislocation. Considerable densification of TiN film was achieved by annealing at 450 degrees C for 30 min in N-2 ambient. In Al/TiN/Si system, it is shown that barrier properties are enhanced by annealing the TiN prior to Al deposition. However, in Cu/annealed TiN/Si system, the postannealing temperature at which etch pits are first observed is still 550 degrees C, and the size and density of etch pits are similar to the case of as-deposited TiN. Thus, we conclude that annealing of TiN film does not enhance the diffusion barrier property of TiN in Cu/TiN/Si system as it does in Al/TiN/Si system.