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An Experimental Examination of Mems Microactuator Material Issues

Published online by Cambridge University Press:  16 February 2011

T. G. Cooney ,
D. E. Glumac ,
W. P. Robbins  and
L. F. Francis
T. G. Cooney
Affiliation:
Department of Chemical Engineering and Materials Science University of Minnesota, Minneapolis, MN 55455-0132
D. E. Glumac
Affiliation:
Department of Chemical Engineering and Materials Science University of Minnesota, Minneapolis, MN 55455-0132
W. P. Robbins
Affiliation:
Deparment of Electrical Engineering University of Minnesota, Minneapolis, MN 55455-0132
L. F. Francis
Affiliation:
Department of Chemical Engineering and Materials Science University of Minnesota, Minneapolis, MN 55455-0132
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Abstract

Thermally induced interactions between materials in complex microactuator structures were investigated. The device structure contained a combination of a piezoelectric layer (lead zirconate titanate - PZT) an electrode with adhesion layer (Pt/Ti), buffer layer (SiO2 or TiO2), structural material (polysilicon and/or silicon nitride), and sacrificial oxide (SiO2). The presence of a SiO2 sacrificial layer did not affect either the bottom electrode or PZT layer. XRD results showed significant platinum and titanium silicide formation in the Pt/Ti electrode at 700 °C (PZT crystallization temperature) on both polysilicon and silicon nitride structural materials when no buffer layer was used. Auger analysis shows that the Ti adhesion layer oxidizes, that measured levels of silicon increase in the electrode zone, and that electrode elements diffuse into the structural material. Buffer layers of SiO2 (0, 0.1, 0.73, 1.3, 1.5 μm) and amorphous TiO2 (0.065 μm) were inserted between the electrode and the structural material. XRD and sheet resistance measurements demonstrated that SiO2 thicknesses greater than 0.73 μm reduced pyrochlore formation in the PZT and reduced the degradation of the electrode. However, this thickness was incompatible with overall surface micromachining processes. The TiO2 layer effectively prevented pyrochlore formation and electrode degradation, while being compatible with overall actuator processing.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 360 , 1994 , 401
Copyright
Copyright © Materials Research Society 1995

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References

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