  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 Young's modulus (E/(1-u)).
Associating square and rectangular membranes with different length to width
ratios, the Poisson's 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.
