High-performance metal hard mask process using novel TiN film for 32-nm node Cu interconnect and beyond

One of the most challenging issues in the metal hard mask (MHM) process is controlling the residual stress in TiN mask. This becomes more important as the feature sizes of trenches and vias continue to shrink and the low k-value dielectrics are introduced to Cu interconnect. It is found that the deformation of trenches due to the residual stress in TiN results in Cu voids forming. To overcome this problem, the correlation between the residual stress and the film property of TiN has been investigated. The residual stress in TiN is found to strongly correlate with both the grain size and the crystal structure of TiN, and low residual stress in TiN is accomplished by suppressing the grain growth of TiN. By applying TiN that has a quite fine needle-like structure, the trench deformation can be suppressed and thus the gap filling is perfectly achieved. The MHM process using TiN film that has a needle-like structure is a promising technology for 32-nm node Cu interconnect and beyond.