Development of an in-line X-ray reflectivity technique for metal film thickness measurement

Non-destructive measurement of thin film (particularly metal film) thickness less than 10 nm has been a challenging task. In this work, we showed that it is possible to obtain the thickness of ultra-thin tantalum films within seconds using a fixed-angle, energy dispersive X-ray reflectivity technique by a conventional, low-energy X-ray copper or chromium source (20 kV/20 mA/400W) and using Parratt reflectivity modeling. We compared this fixed angle, energy dispersive result with more conventional fixed energy, angular dispersive reflectivity to establish the validity of the method and provide error estimates for fast thickness modeling. This X-ray technique is particularly useful for very thin diffusion barrier measurements in future microelectronics applications