X-ray reflectometry – XRR

X-ray reflectometry (XRR) can be used to determine the film thickness, density and boundary layer roughness of ultra-thin films and film systems on very smooth substrates. Film thicknesses of approximately 2–200 nm can be captured. Glass or silicon wafers are the preferred substrates. Accuracies of ~ 0.2 nm are achieved in film thickness determination. XRR is one of the few methods that makes thickness determination possible without weighing and can also determine the roughness of “buried” internal boundary layers between films. Pure thickness determination is also possible on thicker films as long as the roughness of the surfaces is lower.

XRR measurement for precision film thickness determination

XRR measurement for precision film thickness determination. Reflectometry curve of a dual-layer Ag-ZnO film on glass.
© Fraunhofer IST

Reflectometry curve of a dual-layer Ag-ZnO film on glass. The density, layer thicknesses and roughness are determined through the assumption of a model with parameters that are refined until the calculated reflectometry curve (black) optimally coincides with the experimental curve (yellow).