Characterization and Reduction of MEMS Sidewall Friction Using Novel Microtribometer and Localized Lubrication Method

A novel microtribometer is developed to characterize microelectromechanical systems (MEMS) sidewall friction with high resolution. The design is based on a rotational grating displacement sensing mechanism, with which 1.2-nm sensing sensitivity can be achieved. Employing it, the adhesion force (1.85 μN) and the coefficients of static (0.801) and kinetic (0.363) frictions on the sidewall of an as-fabricated MEMS device have been measured. Besides these, the whole process of stick-slip associated with the movement under friction, including the transition between static and kinetic frictional states, has also been clearly revealed. To reduce friction, a localized lubrication method is developed, with which liquid lubricant can be applied directly onto the desired region without affecting other components on the same device. From the experimental results, reduced values in adhesion force (1.23 μN ) and coefficients of friction (0.262 for static and 0.183 for kinetic) are obtained in the same MEMS device after lubrication treatment, demonstrating improved frictional performance.