A Nano- to Macroscale Tribological Study of PFTS and TCP Lubricants for Si MEMS Applications

Abstract

The reliability and lifetime of cyclic contacting Si MEMS is limited by adhesion and their tribological performance. In this study, the tribological effects of adding a lubricant (tricresyl phosphate, TCP) to a bound self-assembled monolayer (perfluorodecyltrichlorosilane, PFTS) at different length scales were examined using a quartz crystal microbalance (QCM), an atomic force microscope (AFM), a reciprocating microtribometer, and a macroscopic reciprocating tribometer. The results showed that the addition of TCP to a PFTS layer increased the number of cycles possessing low friction and wear by at least a factor of four in the macroscopoic tribometer. Differences in friction response over the range of experimental scales were correlated to contact size and pressure. QCM measurements of TCP on PFTS showed a non-zero slip time, which suggests favorable tribological performance in larger length-scale regimes. This non-zero slip time also may indicate TCP mobility.

Friction characteristics of polymers applicable to small-scale devices

“…There is so evidence for trends compared to these fluctuations and so the CoF for these PTFE samples appears to be independent of normal load and track length under these test conditions. This is a little surprising because most literature reports an asymptotically decreasing trend of CoF with sub-newton loads 9,22,23,24 . On the other hand, these measurements cover only a limited range of loads and the measured CoFs are a little above the typical for conventional tests, so the results are not necessarily inconsistent with expectations.…”

“…Consequently, the instruments have low primary resonant frequencies. High-resolution commercial instruments based on low stiffness sensing elements can only deliver measurements at low speed and with poor dynamic response, be they standard micro/nano-tribometer designs or based on AFM 9 . This restriction might not matter all that much for hard, high melting temperature materials that have tended to be used in MEMS.…”

A Survey of the 2010 Quartz Crystal Microbalance Literature

“…The construction of surfaces of pyridine molecules on a poly(chloro‐p‐xylylene) support were analysed and used to bind nickel or cobalt to produce catalytically active films (Malvadkar et al ., ). Surfaces of perfluorodecyltrichlorosilane coated with the lubricant tricresyl phosphate were analysed using a variety of techniques, including QCM to assess the tribological performance of the surface (Miller et al ., ). The production of molecular films was investigated and monitored by QCM using trimethylaluminum, ethanolamine and maleic anhydride (Seghete et al ., ) and surfaces of pyrrole monomers on TiO 2 with the photopolymerisation to polypyrrole monitored by QCM (Strandwitz et al ., ).…”

Frictional Behavior of Micro/Nanotextured Surfaces Investigated by Atomic Force Microscope: A Review

“…56,87 However, for textured surfaces, the results will vary with the size of the AFM tip. Figure 4 shows the schematic diagrams of the AFM tips with di®erent curvature radii sliding on 61 When the radius or the sharpness of the tip is changed, the adhesive force will be changed due to the changes in the meniscus force and the actual contact area.…”