Test And Simulation Of MEMS Film Based On Nano-indentation

With the fast developing of the MEMS (Micro-Electro-Mechanical System), thefilms been used in these tiny systems have drawn a dramatic attention, which play thesignificant importance parts in the performance of the whole MEMS system and eventhe devices. It is important to accurately gain the mechanical properties of the films.However, the mechanical properties of the films are extraordinarily different frombulk scales material, especially the films which are of only several nano-meters thick.As the classic mechanical model could not been applied on films, a lot of attemptshave put on the nano-indentation techniques as it could get the relatively accurateresult about the properties of the film. Modern nano-indentation techniques typicallyuse the indenter of known geometry to slowly impress into the surface of the materialbeen tested, and continuously record the movement of the indenter in both loadingand unloading process to get the load-movement curve. After that, the combinationthe measured data of the geology of indenter, the contact area, the load-movementcurve, and the depth of indenter penetration to determine and calculate the mechanicalproperties of the certain material, for instance the elastic modulus and the hardness.This dissertation focuses on the testing process of SiO2film using thenano-indentation testing technique. Firstly, the nano-indentation test is taken on thecertain SiO2film, and gain the elastic modulus and hardness. After that, this process isstimulated by the FEA method by the software of ANSYS. The curve ofload-movement gain through FEA method reaches a great match with the curve takenby the testing machine. Then, the numerical stimulation is combined with thedimension analysis and calculation, which would determine the tangent modulus andthe yield strength of the film been tested. Finally, the result of the FEA stimulation iscompared with the nano-indentation test, which would optimize the stimulation modeltogether with the bilinear mechanical model of the certain film.Other from these discussions above, other non-ideal factors are also taken intoconsideration, for instance, the abrasion of the indenter and the inner stress of the filmcoming from the fabrication process. These non-ideal factors have dramatic influenceon the result of the nano-indentation test. With more abrasion of the indenter, the result of the testing becoming much greater, and the module need amend for accurateresult. Through the process of MEMS fabrication, all the films suffer from thetemperature change from1200K to300K. After investigation of the this factor, theconclusion has been draw that the inner stress of SiO2film is pressing stress, whichwould low the result of the nano-indentation test.