TiSiN sputtered films as Copper diffusion barriers

TiSiN and TiSiC films were prepared by co-sputtering physical vapor deposition. The 10 nm thick layers were tested as barrier for copper diffusion and compared to the most commonly used reference barriers TaN/Ta and TiN. The diffusion study was carried out by monitoring the sheet resistance variation of the copper layer as function of temperature. With this method, if a copper diffusion through the barrier occurs, a strong increase of the sheet resistance is observed, testifying the failure of the barrier. Sheet resistance variation in a temperature range from 30°C to 500°C was tested under Nitrogen atmosphere. To confirm the results obtained by the temperature-resistance method, the barriers performances were characterized by time-of-flight secondary ion mass spectrometry (ToF-SIMS). In this case, the samples were scanned to follow the copper depth profile after annealing at 500°C for 10 hours. Even though TaN/Ta remains the best copper barrier, TiSiN films show good potential as starting point for the development of alternative barrier materials.