Characterization of Mems Actuators Via Nanoindentation

Nanoindentation has been used to characterize polycrystalline silicon serpentine structures which will become the “framework” for piezoelectric meander line microactuators. These structures are fabricated using silicon wafer surface micromachining processing techniques, and they are suspended about 1 micron above the wafer surface. Normally, nanoindentation equipment is used for materials scratch-testing; however, this equipment was modified so that a probe tip could make contact to the sides of the meander lines, thus enabling known forces to be applied parallel to the wafer surface. For one type of device, the nanoindentaion technique yielded a spring constant of 400 N/m, while simple beam theory gave 1300 N/m and the finite element analysis software ANSYS gave 1200 N/m. This measurement technique holds the promise of being able to apply a known force and then countering that force with piezoelectric actuation to determine the forces that future piezoelectric microactuators will be able to provide.