Research On Surface Effect And Size Effect Of Stiction In Mems

Stiction (or sticking) is a peculiar phenomenon of the microelectromechanical systems (MEMS) and nanoelectromecha-nical systems (NEMS). When the strength of the structure's materials satisfy the demands, the stiction and friction of the MEMS are the mostly cause for their failure. During the course of designing, there has a question that leaved unexhausted, which is how to overcome the stictions between the surfaces of MEMS.For the ratio of surface area to volume is relatively increased, many physical and chemical phenomena of MEMS are different from macroscopic world by the effects of. surface and size. So we shouldn't be limited in the fields of traditional tribology, furthermore, we should go deep into the influence factors of the physics mechanisms of stiction. We have known many factors which affects stiction, five major of them are: capillary force, electrostatic force, van der Waals force, hydrogen bridging and residual stress.In this thesis, firstly, stiction in MEMS was studied, several forces that influence the stiction were also analy-zed. So we found that the capillary force is the dominating force of the stiction in MEMS when it is placed in atmosphere or where there has liquid, and in the condition of vacuum, we should consider the effect of quantum mechanics.Secondly, stiction under the effects of electrostatics, capillary force, residual stress, van der waals force and Casimir force was studied, dimensionless equilibrium constants in equilibrium and unequilibrium conditions werecreate d so as to reflect the configurations' stability. Reflection factors which cause stiction such as surface roughness, surface energy, capillary condesation and meniscus area were considered. We also studied the stiction' s time effect and size effect.Thirdly, the design of the antisticking configuration parameters of different surface forces was studied. The steady antisticking configuration parameter of the microcanti -lever beam under the action of capillary force and the steady antisticking'configuration parameter of the microcavi-ty film under the action of Casimir force was presented.At last, 1H, 1H, 2H, 2H-perflurodecyl —tricholorosilaned (FDTS) , a type of self-assembled monolayer (SAM) was utilized to study the effect of the SAM to stiction.By all this reaserches above, we analyzed several normal forces' effect mechanisms to the stiction in MEMS, some antistiction means were presented to resist stictions in the coruse of designing, producing and using.