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Vol.40, No.8, 897 ~ 903, 2002
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| Title |
| Research Papers / Electronic , Magnetic & Optical Materials : Evaluation of Temperature Effect on Elastic Properties for Si Materials using Electrostatically Actuated Microelectromechanical Systems |
| 정성훈Sung Hoon Jung,이세호Se Ho Lee,정증현Jeung Hyun Jeong,권동일Dong Il Kwon |
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| Abstract |
| Electrostatically actuated testing devices were used to estimate the elastic modulus of single-crystalline Si for microeletromechanical systems. The devices were moved laterally by alternating electrostatic force at a series of frequencies, and then a resonance frequency was determined, with temperature cycling, by detecting the maximum displacement. The elastic modulus was calculated from the detected resonance frequency by Rayleigh`s energy method. The elastic modulus decreased with heating and then increased with cooling, but after thermal cycle the specimen showed a permanent change to a value lower than the initial one. This phenomenon can be explained, to some extent, by the temperature-dependent variation in interatomic force of Si atoms, but the permanent change in elastic modulus implies that it may also be caused by the formation of a thermal oxide layer on the Si with increasing temperature. Composite bending theory was invoked to analyze the oxide effect and the thickness of the oxide layer formed during thermal cycling was estimated from the permanent change in the resonance frequency. The existence of the oxide layer was confirmed by field emission scanning electron microscopy. Finally, the method for compensating the decreasing elastic modulus with increasing temperature were proposed by using the temperature coefficient of elastic modulus. |
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| Key Words |
| Microelectromechanical system , Single - crystalline Si , Resonance frequency , Elastic modulus , Temperature effect , Thermal oxide |
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