Comments on determining the elastic modulus of a thin film using the micromachined free–free beam

Abstract

The study investigates the vibration characteristics of the micromachined free-free beam through analytical and experimental means. In application, this study employed the resonant frequency of the micromachined free-free beam to successfully extract the elastic modulus of a thin film. As a comparison, the vibration characteristics of a micromachined cantilever have also been studied. This study demonstrates that the micromachined free-free beam is a better test key to extract the thin film elastic modulus when the wafer experiences a relatively long etching time. Moreover, the micromachined cantilever gives a lower bound and the micromachined free-free beam gives an upper bound while determining the thin film elastic modulus. Since the free-free beam is a previously fabricated and modeled micromachined structure, it can be employed as a supplement test key to the cantilever beam approach.

Measuring the thin film elastic modulus with a magnetostrictive sensor

“…For example, micromachining processes are usually employed to fabricate the test structure so that a microscale force can be applied to assess properties. Examples of destructive techniques include the bulge test [7][8][9], microbeam bending [10][11][12], microtensile [13][14][15][16][17][18][19][20], resonant frequency (needs micromachining) [21][22][23][24], etc, and numerous reviews have been published [25][26][27][28][29]. In such testing methods, the manner of fashioning the test structure or applying load to deform it results in destruction of the component.…”