In this paper, the bulge test is used to determine the mechanical properties of very thin dielectric membranes. Commonly, this experimental method permits to determine the residual stress (s0) and biaxial Youngs modulus (E/(1-u)). Associating square
and rectangular membranes with different length to width ratios, the Poissons ratio (u) can also be determined. LPCVD Si3N4 monolayer and Si3N4/SiO2 bilayer membranes, with thicknesses down to 100 nm, have been characterized giving results in agreement with literature for Si3N4, E = 212 $pm$ 14 GPa, s0 = 420 $pm$ 8 and u = 0.29.
