Optimization and control of PVD TiN uniformity

Thin titanium nitride (TiN/sub x/) films have numerous applications in VLSI metallization technology. One of the main uses of this material is as a barrier layer for Al interconnect. The demand for barrier material is to prevent interdiffusion while maintaining low resistivity. Thus, uniformity is desired in both composition and thickness. Standard reactive ion sputtering is a widely used deposition technique well suited for TiN/sub x/ barriers. Physical properties and uniformity of the TiN films are strongly dependent on deposition conditions. In a production environment, however, sputtered films need to be reproducible and uniform across the wafer´s diameter. Although TiN/sub x/ thickness and uniformity data is commonly derived from sheet resistance measurements, sheet resistance is sensitive to stoichiometry as well as thickness and can give incorrect results. To optimize deposition conditions for uniform thickness and monitor TiN/sub x/ films in production environment, a more reliable metrology control is needed. This paper presents results of a reactive sputtering process optimization using production multiple angle-of-incidence (MAI) ellipsometer with blue laser (wavelength of 459nm) as the metrology tool.