Investigation of the divided deposition method of TiN thin films for metal-insulator-metal capacitor applications

TiCl4-based chemical vapor deposition (CVD) of TiN films was studied for the application of the top electrode of TiN/Ta2O5/TiN metal–insulator–metal (MIM) capacitors in embedded dynamic random-access memories (eDRAMs). In order to achieve a low level of capacitor leakage current, TiN-CVD at low deposition temperatures of 450°C or less was effective. At such low deposition temperatures, the resistivity of the TiN films increased rapidly as the film thickness decreased. On the other hand, the density of the anomalous growth substances on the TiN film surfaces was higher for the thicker TiN films. We clarified that these two problems were simultaneously unsolvable by means of the usual TiCl4-based TiN-CVD method. In order to avoid the appearance of these phenomena, we applied the divided TiN deposition method to the top electrode formation of the MIM capacitors. This method consists of several repetitions of the deposition step and a subsequent NH3 annealing step. The low film resistivity (~1800 µΩ cm) and the low capacitor leakage current were achieved without the anomalous growth by using the divided deposition method at 350°C. It is expected to be a promising method for the top electrode formation of MIM capacitor structures of the eDRAMs.