STRESS EFFECT ON SUSPENDED POLYCRYSTALLINE SILICON MEMBRANES FABRICATED BY MICROMACHINING OF POROUS SILICON

Large polycrystalline silicon membranes in the form of bridges suspend ed 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 membran es (pads) are measured through micro-Raman spectroscopy and a differen t model is used in each case in order to calculate the stresses from t he observed Raman shifts. A detailed study of stress distribution alon g the membranes and pads has been performed, as a function of thicknes s and annealing treatment. The stress profiles reveal variations in st ress along the membranes and pads. (C) 1998 Elsevier Science S.A. All rights reserved.