Characterization of Adhesion Force in MEMS at High Temperature Using Thermally Actuated Microstructures

New microstructures for the measurement of the interfacial adhesion force between polycrystalline silicon surfaces in micro- and nanoelectromechanical systems and at elevated temperatures are introduced. The devices consist of bilayer cantilever beams with different coefficients of thermal expansion, which carry a rigid plate with a dimple as one of the contacting surfaces. A landing pad patterned on the substrate serves as the second contact surface. Thermal actuation and structural force stored in the beams initiate and terminate, respectively, the contact between the dimple and the landing pad. The presented designs eliminate the effect of the electrostatic force caused by trapped charges at the contact surfaces and drastically reduce the capillary force caused by ambient humidity, both of which may contribute to the adhesion forces measured by other techniques. This allows us to separately measure different sources of adhesion force. The measurement results show that in the absence of electrostatic and capillary forces, the value of the adhesion force is notably reduced and is independent of contact area over the examined range.