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Nanoscale deformation of MEMS materials

Published online by Cambridge University Press:  24 March 2011

A J Lockwood ,
A Padmanabhan ,
R J T Bunyan  and
B J Inkson
A J Lockwood
Affiliation:
Department of Engineering Materials, The University of Sheffield, Sheffield, S1 3JD, UK
A Padmanabhan
Affiliation:
Department of Engineering Materials, The University of Sheffield, Sheffield, S1 3JD, UK
R J T Bunyan
Affiliation:
MEMS Division, QinetiQ, Malvern Technology Centre, Malvern, Worcestershire, WR14 3PS, UK
B J Inkson
Affiliation:
Department of Engineering Materials, The University of Sheffield, Sheffield, S1 3JD, UK
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Abstract

Using a novel in-situ TEM triboprobe holder, nanoscale structures formed from polysilicon MEMS materials have been loaded to characterise the failure mechanisms of reduced scale components. Nanobridges with cross-section dimensions much less than 1μm have been deformed using both single, high displacement indentation and low displacement cyclic fatigue. In both deformation modes, significant residual plastic deformation is measured, occurring and accumulating in the polysilicon. This can be seen as a gradual curvature along the entire crossbeam upon unloading. Where the radius of curvature is very high, fracture of the beams at the centre point was generally also seen. When loading at much lower displacement but under fatigue conditions, localised heating around the moving contact point initiates carbon migration, forming a very strong bond. A high tensile force was needed to severe the contact during unload. Such in-situ techniques demonstrate a range of time dependant failure modes which can be overlooked using post-mortem analysis. In particular, the combined effect of localised frictional heating and contamination on the reliability of components that repeatedly comes into contact with one another.

Keywords

microelectro-mechanical (MEMS)transmission electron microscopy (TEM)nano-indentation
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1297: Symposium P – Deformation Mechanisms, Microstructure Evolution and Mechanical Properties of Nanoscale Materials , 2011 , mrsf10-1297-p07-09
Copyright
Copyright © Materials Research Society 2011

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References

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