9521288 Zeng The overall aim t his University-Industry GOALI project is to eliminate or reduce "stiction", the adhesion of microscopic surfaces present in micromachined microelectronic systems (MEMS), which can result in the malfunctioning of such system. Humidity-induced stiction is of particular concern. We propose to alleviate the problem by coating the MEMS surfaces with an organic film having the property that two such coated surfaces repel one another on close approach. The surfaces therefore cannot adhere but remain hydrophobic. The project, which involves a collaboration among physical scientist a the University of Nebraska-Lincoln (UN-L) and engineers at Analog Devices, Inc. of Waltham, MA, will be divided into four phases: 1) Organic chain molecules that have an embedded polar group with an effective dipole moment projecting parallel to the molecular long axis will be synthesized. These molecules will be covalently bonded to the polysilicon substrates that make up the bare MEMS elements, sot hat a self-assembled monolayer (SAM) with a net dipole moment normal to the surface will cover the substrate. Two such coated surfaces will repel each other. (2) Atomic force microscopy (AFM) and chemical force microscopy (CFM) will be used to determine the quality of the SAM's and toe measure the forces of adhesion and friction between SAM-coated substrates. (3) Monte Carlo computer simulations of model SAMs will elucidate the molecular mechanism of stiction that operate in real dipolar SAMs. Feedback from phases (2) and (3) will guide the design of "smart" SAM coatings being synthesized in phase (1). The possible detrimental effects of humidity will also be assessed. (4) The testing of candidate SAMs in an actual MEMS, the ADXL50 accelerometer, will be accomplished by means of standard drop, shock-survival and electrical-capture tests at Analog Devices.
