Stress effect on suspended polycrystalline silicon membranes fabricated by micromachining of porous silicon

Large polycrystalline silicon membranes in the form of bridges suspended over deep monocrystalline silicon cavities have been fabricated by using porous silicon as a sacrificial layer. Stresses within the free-standing membranes as well as within supported polycrystalline membranes (pads) are measured through micro-Raman spectroscopy and a different model is used in each case in order to calculate the stresses from the observed Raman shifts. A detailed study of stress distribution along the membranes and pads has been performed, as a function of thickness and annealing treatment. The stress profiles reveal variations in stress along the membranes and pads. (C) 1998 Elsevier Science S.A. All rights reserved.