Studies of Humidity-Induced Stiction in MEMS

9521288 Zeng这个大学-行业目标项目的总体目标是消除或减少“粘连”，即微机械微电子系统（MEMS）中存在的微观表面的粘连，这可能导致系统故障。湿度引起的粘连是特别值得关注的。我们建议通过在MEMS表面涂覆有机薄膜来缓解这个问题，这种有机薄膜具有两个这样的涂层表面在接近时相互排斥的特性。因此，表面不能粘附，但仍保持疏水性。该项目由内布拉斯加州大学林肯分校（unl）的物理科学家和马萨诸塞州沃尔瑟姆市Analog Devices公司的工程师合作完成，将分为四个阶段：1)合成具有嵌入极性基团的有机链分子，其有效偶极矩与分子长轴平行。这些分子将共价结合到构成裸MEMS元件的多晶硅衬底上，这样，具有与表面垂直的净偶极矩的自组装单层（SAM）将覆盖在衬底上。两个这样的涂层表面会相互排斥。(2)原子力显微镜（AFM）和化学力显微镜（CFM）将用于确定SAM的质量，并测量SAM涂层衬底之间的附着力和摩擦力。(3)通过蒙特卡罗计算机模拟模拟模型，阐明了实际偶极地对空晶体的分子粘滞机制。阶段(2)和阶段(3)的反馈将指导阶段(1)合成的“智能”SAM涂层的设计。还将评估湿度可能产生的有害影响。(4)候选SAMs在实际MEMS （ADXL50加速度计）中的测试将通过adi公司的标准跌落、冲击生存和电捕获测试来完成。

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.