A physical model to predict stiction in MEMS

Abstract

In the paper, the hardness of silicon is wrongly stated as 850 kg mm2, where this should read 8500 kg mm2. In addition, the typical standard deviation of the distribution of the summit heights in the Greenwood–Williamson model has been overestimated, and should read about 1 nm instead of 3 nm. The result is that the calculated plasticity index becomes smaller, and hence the paper overestimates the amount of plastic deformation that occurs in silicon MEMS contacting surfaces. The value of the plasticity index with the new numbers becomes now 2.6 instead of the 22 reported in the original paper. This is fairly close to 1.0 which is the lower limit of `mainly plastic deformation'. The remark that for a true understanding of the deformation mode at the contact interface one should employ computer modeling as in [23] is therefore really important.

Attractors near grazing–sliding bifurcations

“…The occurrence of 'stiction' (static forces) implies that, for instance, a slowly moving activated arm of a robot may exhibit 'jitters' due to the presence of stick-slip motion of mechanical elements. Auto-adhesion or stiction is also an important reliability issue in micro-electromechanical systems [3]. In the mechanical examples given the presence of 'stiction' implies switching between the dynamics with the kinematic friction force, and the dynamics characterised by the static friction force.…”

Computation of Adhesive Forces Due to Van Der Waals and Capillary Effects on Realistic Rough Surfaces

“…The solution of such a problem represents a formidable task: to the Authors' knowledge, nobody has formulated a suitable algorithm for the case of surfaces with generic shape. A simple (though inexact) estimate can be obtained by considering an adaptation of the aforementioned PFA (see [7] and [8]). The force is computed point-wise by considering that the capillary attraction is kept constant and equal to the Laplace pressure until a critical separation is reached, after which the force is suddenly dropped to zero:…”

“…The stochastic nature of the actual rough surface has been considered in many papers, most of which [6] are based on simplified models of elastic-plastic deformation. In [7] a simpler model has been adopted, in the sense that rigid-plastic behavior of asperities has been considered and that adhesive forces have been estimated on the basis of the average surface separation.…”

MEMS Reliability Review

“…Another common contributor to stiction is chemical bonding between contact surfaces [32]. One common example is hydrogen bonding, which is associated with water on surfaces.…”