Experimental Measurements of the Strain Energy Release Rate for Stiction-Failed Microcantilevers Using a Single-Cantilever Beam Peel Test

• Published in: Journal of microelectromechanical systems 2007-02, Vol.16 (1), p.38-43
• Main Authors: Leseman, Z.C., Carlson, S.P., Mackin, T.J.
• Format: Article
• Language: English
• Subjects: Adhesion; Adhesives; Beams (radiation); Cantilever; Cantilever beams; Condition monitoring; Displacement; Displacement control; Energy measurement; Equations; Exact sciences and technology; Failure; Fracture mechanics; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mathematical models; Mechanical instruments, equipment and techniques; Micromechanical devices and systems; peel test; Peel tests; Physics; Piezoelectric actuators; Solid modeling; Stiction; strain energy; Strain measurement; Structural beams; Studies; Testing
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2006.883570

In this paper, we present experimental measurements of the strain energy release rate for stiction-failed polysilicon microcantilevers using a newly developed single cantilever beam peel test. Our experiments show that dry-contacting microcantilevers adhere exclusively as tip-stuck, "arc-shaped" stiction failures, while adhesion under "wet" conditions generate exclusively "s-shaped" stiction failures. Microcantilevers were "peeled" from the substrate under displacement control using a piezoelectric actuator attached to one end of an array of microcantilever beams. The crack length was monitored using interferometric imaging, and related to the applied displacement using established equations from linear elastic fracture mechanics. The pull-off forces associated with "arc-shaped" stiction failures were an average value of 89.7 nN, for 1000 mum long beams, and an average value of 123 nN for 1500 mum long beams. Adhesion energies for s-shaped failures were measured as 13.7 mJ/m 2 for IPA released beams and 15.4 mJ/m 2 for deionized water released beams. These values are in good agreement with previous measurements. The proposed experimental method enables application of a simple fracture mechanics model using a standard specimen geometry. These experiments, using both wet and dry adhesion failure conditions, show that the quality of the adhesive failure depends upon the magnitude of the forces pulling the microcantilever into contact with the underlying substrate