Structure and non-uniform strain analysis on p-type porous silicon by X-ray reflectometry and X-ray diffraction

Structural properties of porous silicon layers performed on p-type (100) silicon wafers have been studied by X-ray reflectometry and X-ray diffraction techniques. The mean surface porosity of the layers has been obtained by comparing the critical reflection angles of the porous layer and the silicon substrate. The obtained values are in agreement with microgravimetry measurements. The strain of the porous layer as a function of the technological parameters has been analyzed by X-ray diffraction. The origin of the strain in the porous silicon is discussed according to the presence of stress and changes in the porosity across the layer. Finally, a minimum strain condition has been found, allowing the optimization of the fabrication process.