High Resolution X-Ray Diffractometric, Topographic and Reflectometric Studies of Epitaxial Layers on Porous Silicon Destined for Exfoliation

The presently studied substrates for manufacturing freestanding silicon epitaxial layers contained two porous layers with different porosities. The upper layers of significantly lower porosity after annealing provided smooth surfaces for deposition of epitaxial layers and the deeper layers of greater porosity enabling easier exfoliation epitaxial foil. The layered structures have been studied by means of synchrotron diffraction topography and by recording of rocking curves from small local area. The most effective method of revealing defects in freestanding exfoliated layers were Bragg-case projection topographs and ‘zebra’ pattern monochromatic beam topographs providing a map of sample curvature. The samples have been additionally examined by means of high-resolution diffractometry and reflectometry.The porous layers without epitaxial deposition provided strong narrow maximum at low angle side of the substrate maximum common for both of the porous layers. The most probable effect of the deposition of epitaxial layer is the decrease of lattice parameter in the upper layer with lower porosity, which provided the maxima in the diffraction curves located on low angle side of the substrate maximum. The topographic investigations revealed some defects in deposited epitaxial layers, connected with some irregularities of the annealed porous layer. Very characteristic common defects were large caverns, overgrown in the epitaxial process with the diameters of several tenths of micrometers and defects (possibly the overgrown submicron caverns), associated with some bundles of dislocations resolved in the topographs. In layers of large thickness, the characteristic long black and white stripes along <110> have also been observed, which most probably were stacking faults with dislocation loops