Authors: M. Jobin, V. Sidorenko, R. Foschia
Affilation: Ecole Ingenieurs Geneve, Switzerland
Pages: 889 - 891
Keywords: membrane, MEMS, interference microscope, phase shift, nanomechanics, silicon nitride
The accurate mechanical characterisation of thin membranes is recognized of prime importance for the development of membrane-based MEMS. To address this issue, we have built a measurement system which uses a nanoindentor to apply a well controlled force on one side of the membrane, while the deformation is recorded simultaneously on the other side with a home-made interferometric microscope. The use of a nanoindentor ensures a highly localised load on the membrane and the interferometric microscope allows us to measure deformations down to nanometric scale. The available forces enable deformations ranging from a few nanometers to membrane rupture. We have used optically transparent silicon nitride membrane up to 500nm thick The deformation is totally reversible without any measurable residual stress for loads up to 1000 uN. We measured rupture for loads ranging from 1600uN to 1700uN. The measured membrane spring constant at the center of the membrane is 169 N/m, close to the expected 140N/m given by the theory. The measured spring constant increases up to 301 N/m when the tip is brought close to a corner. Clear nanometric deformation of the membrane can be obtained under successive loads.