Rocking curve: Crystal surface evaluation


Rocking curve measurements are sensitive to defects and strain fields within the crystal lattice. Combining this technique with a mapping stage allows to scan a crystal surface and determine faulty areas. In lattice matched thin films, rocking curves can also be used to study layer thickness, superlattice period, strain and composition profile, lattice mismatch, ternary composition, and relaxation.

A wafer surface must meet very high standards of cleanliness and homogeneity. Manufacturers are striving to grow crystals with as few as possible dislocations and defects. In particular for SiC, the elimination of dislocations has provided new fields of application for this material.

By equipping an Omega/Theta diffractometer with a mapping stage and a double crystal, a Rocking Curve mapping of a certain reflection over the crystal surface can be measured. The image shows the result of such a mapping of an SiC wafer. The inner parts of the wafer exhibit a two to three times larger FWHM of the Rocking curve. This may be related to either scratches on the surface or growth-induced defects.