Anti-stiction treatments improve the peformance of devices such as microphones, accelerometers, and micro-switches.
Advanced Stiction Control of MEMS devices and other super-critical components allows designers to push their performance limits to new levels, opening up higher value market spaces and creating longer-lived, higher-reliability devices. The RPX-540 has the widest process window for the application of a multitude of anti-stiction coatings, such as those presented on the right.
Stiction is the static friction that needs to be overcome to enable relative motion of stationary objects in contact.
In MEMS (Micro-electro-mechanical systems) devices, stiction is often attributed for the device failure of sensors with moving actuators or masses. By applying a molecular layer of low surface energy organics, stiction can be mitigated or even eliminated. This allows for higher device reliability.
Shown below are number of chemistries that can be applied to surfaces to reduce the surface energy.
Cantilever beams which are used to measure stiction. (Ref: Ashurst, W. R., Carraro, C., and Maboudian, R., “Vapor Phase Anti-Stiction Coatings for MEMS,” IEEE Transactions on Device and Materials Reliability, Vol.)
PETS (Pentafuorophenylpropyltrichlorosilane) is a fluroinate ring structure used to create hydrophobic surfaces. The cyclical ring structure offers greater stability than straight chain molecules. Typical applications are in the area of optical coatings.
FDTS (Heptadecafuoro-1,1,2,2,-tetra-hydrodecyl)trichlorosilane is a long chain perfluoronated silane for producing hydrophobic surfaces. With its Teflon-like properties, FDTS is often used to chemically passivate surfaces. Applications include anti-stiction coatings for MEMS devices such as cantilevers, microphones, moving displays and can be used as an anti-stick release layer for nano-imprinting. The long (C-10) alkyl-chain promotes a self-assembling monolayer formation. Treated surfaces typically have surface energies of 12 dynes/cm.
FOTS (Tridecafuoro-1,1,2,2,-Tetrahydrooctyl)trichlorosilane is very similar to FDTS, having a slightly shorter C-8 chain instead of a C-10. Often used to lower the coefficient of friction silicon substrates, FOTS is a lower cost alternative to FDTS and often provides nearly the same functionality for most applications.
OTS (n-Octadecyltrichorosilane) (C-18) is a long chain hydrocarbon hydrophobic self assembling monolayer (SAM). OTS isomers have the highest concentration of terminal silane substitution. OTS is used for many hydrophobic and oleophobic coatings. OTS is often very difficult in vapor applications as a result of its very low vapor pressure. However, the RPX has the ability to deliver OTS due to its novel Vaporrix gas delivery system.
TMCS (Trimethylchlorosilane) is one of the most broadly used and economical silyation precursors. TMCS is often used in GC-Chromatography and other applications to passivate surfaces.
For a further explanation of the deposition technology and precursors available, consult the brochure below.
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