Abstract
An innovative micro-test structure for detecting the thermal expansion coefficient (TEC) of metal materials is presented in this work. Throughout this method, a whole temperature sensing moveable structures are supported by four groups of cascaded chevrons beams and packed together. Thermal expansion of the metal material causes the deflection of the cascaded chevrons, which leads to the capacitance variation. By detecting the capacitance value at different temperatures, the TEC value of the metal materials can be calculated. A finite element model has been established to verify the relationship between the TEC of the material and the displacement of the structure on horizontal and vertical directions, thus a function of temperature for different values of TEC can be deduced. In order to verify the analytical model, a suspended-capacitive micro-test structure has been fabricated by MetalMUMPs process and tested in a climate chamber. Test results show that in the temperature range from 30 °C to 80 °C, the TEC of the test material is 13.4 × 10−6 °C−1 with a maximum relative error of 0.8% compared with the given curve of relationship between displacement and temperature.
Highlights
Successful design of a microelectromechanical systems (MEMS) device should take into consideration electrical engineering, mechanical engineering, material processing and microfabrication.In the mechanical design stages, the thermal expansion coefficient (TEC) of the metal structure is one of the most critical properties to be considered [1], which will be directly linked to the flexibility of the support beams and the dynamic characteristics, and further affect the performance of the MEMS devices
This paper presents a novel suspended-test structure for detecting the TEC of metal material
Finite element model is used to verify the relationship between the TEC of the material and displacements of the structure in the horizontal and vertical between the TEC of the material and displacements of the structure in the horizontal and vertical directions
Summary
Successful design of a microelectromechanical systems (MEMS) device should take into consideration electrical engineering, mechanical engineering, material processing and microfabrication. There are a lot of available techniques can be utilized to measure the TEC of metal materials, e.g., current-driven vernier microgauge methods [10,11], optical images and diffraction patterns methods [12,13], as well as x-ray diffraction methods [14], etc Compared with those techniques, capacitance methods are preferable since their higher sensitivity, simpler operation and more flexible readout process [15,16,17]. The novel utilized to verify the relationship between the TEC of the material and displacements of the micro-test structure model has been described in details and analyzed theoretically, while a finite structure in horizontal and vertical directions. Fabricated by MetalMUMPs process has been measured in a climate chamber, with a TEC value of (13.4 ± 0.1) × 10−6 ◦ C−1
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