MATERIAL CHARACTERISATION AT THE MICRO SCALE THROUGH ON-CHIP TESTS

A series of on-chip test structures where designed, modeled and fabricated for on-chip fracture characterization of 0.7 µm thick polysilicon film. The first test structure is rotational and actuated by comb- fingers capacitors which develop a force sufficient to load the specimens up to rupture; it allow the determination of Young modulus and rupture strength. The second kind of test structure is actuated in the direction orthogonal to the substrate by means of a system of parallel plate actuators, four specimens placed at the four corners of the device are loaded in bending and torsion; they are conceived in order to estimate the value of the shear elastic modulus of the polysilicon film. The third test structure is again actuated by parallel plate capacitors in the direction orthogonal to the substrate and able to load up to rupture a couple of specimens in bending in the plane orthogonal to the substrate; this device has been built in order to measure the resistance of the polysilicon film in these particular loading conditions and to evaluate the possible influence of grain morphology on the mechanical responses. The three different on-chip test structures are briefly described in the paper and the first obtained experimental results are presented and discussed.