X-ray Metrology, wafer

X-ray Reflectivity (XRR)

The technology

Beam Path Slit Slit, X-ray Metrology
XRR experiment

The picture shows a typical setup of an XRR experiment. The configuration can be adjusted with monochromator and analyzer crystals, Soller slit and knife-edge collimator to optimize the measurement conditions that match the sample.

Also called X-ray Reflectometry. This is a non-contact, non-destructive analytical technique to determine thickness, density, roughness and interstitial roughness of thin films. When X-rays are irradiated on to the sample at very low angles there is total reflection of X-rays from the sample surface. As the angle of irradiation is gradually increased beyond a certain angle called critical angle, which is dependent on the material, X-rays are reflected from the interfaces of the sample and give rise to interference fringes. The periodicity of the fringes is proportional to the thickness of the film, the fall of intensity is proportional to the roughness of the film and amplitude of the fringes is proportional to the density of the top and bottom layers. XRR is an absolute measurement technique from first principles. XRR and XRF are considered as complementary techniques.

D8 FABLINE – X-ray Reflectivity Study of Ultra Thin HfO2 Films
(PDF application report)