Effect of Nitrogen Flow Rate on TaN Diffusion Barrier Layer deposited between a Cu Layer and a Si-Based Substrate

Abstract A TaN x layer was deposited as a barrier between Cu and a p-type Si-based substrate. Various N 2 flow rates were used during deposition along with a fixed Radio Frequency (RF) power and a fixed Ar-sputtering flow rate. The performance of the various TaN x barrier layers was tested and the optimized parameters for preparation were determined. When using a N 2 flow rate of 3.5 sccm and a N 2 /Ar ratio of 1:10 followed by annealing at 700 °C the Ta:N ratio of the TaN x barrier was 10:7. The current leakage of the barrier was lower when using a higher N 2 flow rate during deposition as this produced an amorphous TaN x thin film, and the electric capacitance was relatively greater on insertion of a TaN x layer as a insulation resistance layer when using a higher N 2 flow rate. The surface roughness of the TaN x film, as measured by atomic force microscopy (AFM), slightly increased with increasing N 2 flow rate. The aforementioned processing parameters produced a high-quality amorphous TaN x thin-film layer by adjustment of the TaN x -barrier crystallinity. TaN x barriers produced using the various N 2 flow rates can prevent the diffusion of Cu atoms to the Si substrate. The calculated initial diffusion coefficient of TaN 0.7 annealed at 700 °C, as calculated by Fick's law, was 1.3 × 10 −5  cm 2 /s. X-ray diffraction (XRD) analysis indicated that no Cu-Si compounds were present in the TaN 0.7 layer prepared using a 3.5 sccm N 2 flow rate and a N 2 /Ar ratio of 1:10 followed by annealing at 700 °C.