AVS 47th International Symposium
    MEMS Thursday Sessions
       Session MM-ThA

Paper MM-ThA1
Stress Measurement in MEMS Devices

Thursday, October 5, 2000, 2:00 pm, Room 309

Session: Material Science of MEMS
Presenter: L.A. Starman, Air Force Institute of Technology
Authors: L.A. Starman, Air Force Institute of Technology
J.D. Busbee, Air Force Research Laboratory Materials Directorate
J. Reber, Wright State University
J.F. Maguire, Air Force Research Laboratory Materials Directorate
W.D. Cowan, Air Force Research Laboratory Materials Directorate
Correspondent: Click to Email
Due to the unique structure and small scale of Micro-Electro-Mechanical Systems (MEMS), residual stresses during the deposition processes can have a profound affect on the functionality of the MEMS structures. Typically, the material properties of thin films used in surface micromachining are not controlled during deposition. Currently, few techniques are available to measure the residual stress in MEMS devices, with each having a limited degree of validity. In this paper, Raman imaging spectroscopy is utilized to examine the residual and induced stress in silicon MEMS test structures. As MEMS structures become more complicated, images generated from Raman spectroscopy can provide valuable information on stress fields in the structure. Since the Raman methodology is directly sensitive to stress in the deposited material, the potential exists for this technology to be used both as an in situ quality control device and for the control of gradients in the batch processing. Successful implementation of this technique allows the validation of MEMS designs. We report here the mapping of the complete stress field across a micromirror flexure. Vertical displacement measurements obtained using an interferometric microscope allow the applied stress in the device flexures to be calculated as a conformation of the stress image.