AVS 49th International Symposium
    Microelectromechanical Systems (MEMS) Wednesday Sessions
       Session MM-WeP

Paper MM-WeP5
Characterization of the Residual Stress in Titanium/Platinum and Tantalum/Platinum Thin Film Electrodes used in the Processing of PZT MEMS Devices

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Poster Session
Presenter: R.G. Polcawich, U.S. Army Research Laboratory
Authors: R.G. Polcawich, U.S. Army Research Laboratory
J.P. Clarkson, U.S. Army Research Laboratory
J. Pulskamp, U.S. Army Research Laboratory
A. Wickenden, U.S. Army Research Laboratory
M. Wood, U.S. Army Research Laboratory
K. Kirchner, U.S. Army Research Laboratory
M. Ervin, U.S. Army Research Laboratory
E. Zakar, U.S. Army Research Laboratory
M. Dubey, U.S. Army Research Laboratory
Correspondent: Click to Email
Residual stress in freely suspended MEMS devices is critical for optimal performance. The high temperature anneals required to crystallize lead zirconate titanate (PZT) thin films create stress gradients within the piezoelectric stack yielding non-planar released structures. From our previous studies, tantalum/platinum (200 Å / 1700 Å) metallization used as bottom electrodes for PZT MEMS has contributed the largest residual stress (~850 Mpa) to the multilayer stack. This research focused on using the sputter deposition parameters as a means of producing low stress (~<450 Mpa) Ta/Pt and Ti/Pt metal layers. Ti, Ta, and O diffusion were investigated with Auger electron spectroscopy by using O@super 18@ as a tracer during the anneal process. Additionally, x-ray diffraction and scanning electron microscopy were used to identify the presence of second phase compounds within the Pt metal layer. From this combined analyses, oxygen diffusion and the subsequent formation of TiO@sub 2@ and Ta@sub 2@O@sub 5@ compunds within the Pt matrix was the primary cause of reducing the residual stress in metal stacks with Ta and Ti thin films greater than 200Å.