Integrated measurement of Ti and TiN thickness and optical constants using reflectance data through a vacuum chamber window

The thickness and optical constants of titanium and titanium nitride thin films were measured by visible reflectometry through a window of a vacuum deposition system while the wafer was cooling from deposition to room temperature. The measurement system is ultracompact and was designed for integration into semiconductor processing equipment. This integrated metrology tool does not affect the system throughput. The Ti and TiN films were deposited on 300 nm silicon dioxide films on 200 mm diam silicon wafers using an Applied Materials Endura physical vapor deposition system. The system was used to characterize thin metal films with various thicknesses and deposited using conventional dc magnetron sputtering. The optical constants of the Ti and TiN films were modeled through the use of a Lorentz oscillator dispersion model. A variable angle of incidence spectroscopic ellipsometer (VASE)^® was used to measure spectroscopic ellipsometric data at multiple angles of incidence and these data were fit to an optical model. The model obtained from the VASE^® data analysis was then used to fit the visible reflectance data measurements. This article will compare the integrated measurements with measurements from a production metrology tool that measure both ellipsometric and reflectance data from the same location on the wafer, as well as with measurements from a research grade ellipsometer (VASE^®).