Studies of Humidity-Induced Stiction in MEMS

9521288 Zeng他的大学-工业GOALI项目的总体目标是消除或减少“静摩擦”，即微机械微电子系统（MEMS）中存在的微观表面的粘附，这可能导致这种系统的故障。 湿度引起的静摩擦是特别值得关注的。 我们建议通过用有机膜涂覆MEMS表面来缓解这个问题，所述有机膜具有两个这样的涂覆表面在接近时彼此排斥的性质。 因此，表面不能粘附，但保持疏水性。 该项目由内布拉斯加大学林肯分校（UN-L）的物理科学家和ADI公司的工程师合作完成。将被分为四个阶段：1）将合成具有嵌入的极性基团的有机链分子，所述嵌入的极性基团具有平行于分子长轴突出的有效偶极矩。 这些分子将共价键合到构成裸MEMS元件的多晶硅衬底上，因此具有垂直于表面的净偶极矩的自组装单层（SAM）将覆盖衬底。 两个这样的涂层表面将相互排斥。 (2)将使用原子力显微镜（AFM）和化学力显微镜（CFM）来确定SAM的质量，并测量SAM涂覆基材之间的粘附力和摩擦力。 (3)Monte Carlo计算机模拟模型SAM将阐明在真实的偶极SAM中操作的粘滞的分子机制。 来自阶段（2）和（3）的反馈将指导阶段（1）中合成的“智能”SAM涂层的设计。 还将评估湿度可能产生的有害影响。 (4)在实际MEMS（ADXL 50加速度计）中，候选SAM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.