Metrologies for mechanical response of micro-and nanoscale systems

Abstract

Thin films and nanomaterials lie at the heart of the burgeoning fields of nanoelectronics and nanotechnology, and the accurate measurement of their properties provides a basis for consistent manufacturing, fair trade, and reliable performance. Introduction of such materials into current and future technologies has opened an entirely new suite of both materials science and measurement science challenges-effects of dimensional scaling play a stronger role in the reliability of thin films and nanomaterials than in any other materials previously known. Surfaces and interfaces can dominate and change behaviors and properties known to develop in bulk materials of the same chemical composition. As a result, extrapolation of bulk responses to the nanoscale is often inaccurate. This chapter describes metrologies developed by NIST scientists and collaborators for mechanical properties of dimensionally constrained materials; these approaches make use of methods inherently sensitive to small volumes. Attention is focused on emerging test methods for several key forms of mechanical response-elasticity, strength, and fatigue. We attempt to avoid excessive duplication of discussion contained in other chapters. Emphasis is placed on structures that are volume constrained, with one or more dimensions less than 1μm and often less than 100 nm. The first metrology is contact-resonance atomic force microscopy (AFM), wherein the mechanical resonance properties of an AFM cantilever in contact with a thin-film or nanoparticle-based specimen are shown to depend sensitively on the elastic properties of a small volume of material beneath the tip. The second metrology is microtensile testing, wherein thin-film specimens are patterned into free-standing tensile specimens by use of integrated circuit fabrication methods, and force-displacement response measured. The third metrology is based on application of controlled Joule heating to patterned thin films on substrates by alternating current, for the purpose of measuring fatigue and strength of thin patterned films on substrates. © Springer Science+Business Media, LLC, 2008.