X-ray characterization of periodic sub-nm surface relief gratings

Line and cross lattices of 260 and 360 nm pitch were prepared by covering p-doped Si(100) substrates with photoresist, structuring and implanting with 3 x 1015 cm-2, 45 keV As+ ions. These doping lattices with n+-p periodicity were investigated by X-ray diffraction (XRD) and reflectivity (XRR). While XRD did not show any signal of the periodic structure, XRR revealed a clear periodic diffraction pattern related to the pitch of the doping lattice. The features of this pattern as a function of the lattice orientation are discussed in detail for the cross lattice. Atomic force microscopy showed that the measured diffraction pattern is caused by a surface relief grating with sub-nm amplitude, which was generated by a final doping-dependent etching step during sample preparation. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)