Lubrication of polysilicon micromechanisms with self-assembled monolayers

Technical Report · Mon Jun 01 04:00:00 EDT 1998

DOI:https://doi.org/10.2172/671989· OSTI ID:671989

Srinivasan, U; Foster, J D; Habib, U; Howe, R T; Maboudian, R ^[1]; Senft, D C; Dugger, M T ^[2]

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1. Berkeley Sensor and Actuator Center, CA (United States)
2. Sandia National Labs., Albuquerque, NM (United States)

Here, the authors report on the lubricating effects of self-assembled monolayers (SAMs) on MEMS by measuring static and dynamic friction with two polysilicon surface- micromachined devices. The first test structure is used to study friction between laterally sliding surfaces and with the second, friction between vertical sidewalls can be investigated. Both devices are SAM-coated following the sacrificial oxide etch and the microstructures emerge released and dry from the final water rinse. The coefficient of static friction, {mu}{sub s} was found to decrease from 2.1 {+-} 0.8 for the SiO{sub 2} coating to 0.11 {+-} 0.01 and 0.10 {+-} 0.01 for films derived from octadecyltrichloro-silane (OTS) and 1H,1H,2H,2H-perfluorodecyl-trichlorosilane (FDTS). Both OTS and FDTS SAM-coated structures exhibit dynamic coefficients of friction, {mu}{sub d} of 0.08 {+-} 0.01. These values were found to be independent of the apparent contact area, and remain unchanged after 1 million impacts at 5.6 {micro}N (17 kPa), indicating that these SAMs continue to act as boundary lubricants despite repeated impacts. Measurements during sliding friction from the sidewall friction testing structure give comparable initial {mu}{sub d} values of 0.02 at a contact pressure of 84 MPa. After 15 million wear cycles, {mu}{sub d} was found to rise to 0.27. Wear of the contacting surfaces was examined by SEM. Standard deviations in the {mu} data for SAM treatments indicate uniform coating coverage.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 671989
• Report Number(s): SAND--98-0848C; CONF-980638--; ON: DE98004530; BR: DP0102031
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
ACTUATORS
EXPERIMENTAL DATA
FRICTION
LUBRICANTS
LUBRICATION
MINIATURIZATION
MOTORS
SILICON
SILICON OXIDES
WEAR