Friction and Wear Properties of ALD Coated MEMS

Abstract

A comparative study of the microtribological properties of native oxide covered single crystal silicon and silicon coated with atomic layer deposited (ALD) alumina films is presented. The dry friction and wear behavior were investigated using a novel microelectromechanical system (MEMS) tribotester. The coefficient of friction for alumina coated surfaces and for silicon uncoated surfaces was monitored before and after wear. The friction versus normal load curves of uncoated silicon can be described by a Johnson-Kendall-Roberts model with pressure dependent shear strength while for the alumina coated surfaces, a linear dependence between the friction force and the normal load was found. Both uncoated silicon surfaces and alumina coated surfaces showed a decrease of the friction force with the number of sliding cycles.

ALD Applications Beyond Outside IC Technology - Existing and Emerging Possibilities

“…Possible applications range from chemical and corrosion resistant coatings [19] to enhancement of mechanical properties of engineered parts. Examples of enhancements of mechanical properties, investigated for the MEMS applications, are solid lubricants [20] and tribological coatings [21]. High surface conformality of ALD enables reliable coating of complex parts as well, including inside of tubes [22] and cavities.…”

Initial Surface Reactions of TiO2 Atomic Layer Deposition onto SiO2 Surfaces: Density Functional Theory Calculations

“…In contrast to the other techniques tested, ALD allows highly conformal coatings to be deposited on high aspect ratio structures, which are typical of MEMS devices. 6 In fact, a recent report 7 has shown that the tribological characteristics of surfaces can be significantly improved through the use of ALD coatings, due to the highly uniform nature of the deposition. This is quantified with respect to the debris creation and the stability of the friction coefficient.…”

Reducing the adhesion and friction forces of Si by coating ultra-thin Al2O3 films

“…[10][11][12][13] However, the main challenge is to package the MEMS devices to include the vapor feed system. Hard lms, such as diamond-like carbon (DLC), 14,15 tungsten (W), 16,17 silicon carbide (SiC), 18,19 titanium dioxide (TiO 2 ) 20,21 and alumina (Al 2 O 3 ) [22][23][24] can also reduce friction and wear of Si material, while how to coat the complicated structures of MEMS devices conformally is a matter of concern.…”