A Novel Micro Tensile Testing Instrument with Replaceable Testing Specimen by Parylene Passivation Technique
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1052-DD02-08
A Novel Micro Tensile Testing Instrument with Replaceable Testing Specimen by Parylene Passivation Technique Yung-Dong Lau1, Tso-Chi Chang1, Hong Hocheng1, Rongshun Chen1,2, and Weileun Fang1,2 1 Department of Power Mechanical Engineering, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan 2 Institute of NanoEngineering and MicroSystems, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan ABSTRACT This study has successfully demonstrated a novel tensile testing approach to mount the thin film test specimen onto a MEMS instrument using microfabrication processes. The MEMS instrument consists of a thermal actuator, differential capacitance sensor, and supporting spring. The thermal actuator applies a tensile load on the test specimen to characterize the Young’s modulus and the residual stress of the thin film. As compare with the existing approaches, the problems and difficulties resulting from the alignment and assembly of a thin film test specimen with the testing instrument can be prevented. Furthermore, the parylene passivation technique with the MEMS fabrication process allows the user to change the test materials easily. In application, the present approach has been employed to determine the Young’s modulus and the residual stress of Al films. INTRODUCTION There are many thin-film mechanical testing approaches have been reported, for instance, the micro tensile test, the cantilever beam bending test, the nanoindentation test, and the bulge test [1-4]. However, it remains a challenge to precisely apply load as well as to determine the deformation during a thin-film material test. Moreover, it is not straightforward to prepare and place a thin film specimen during a test. In summary, the specimen preparation is one of the key sources of measurement error for thin-film mechanical testing. In general, the conventional tensile testing machine contains a loading module, sensing module, and gripping mechanism. Because they match in size, load, and displacement, MEMS devices are appropriate for the mechanical testing of thin film materials. In [1], the micro fabrication process is only employed to prepare the test specimen, on-chip loading and displacement sensing is not available. MEMS actuators are used in [5] for micro tensile testing, but they may still have problems and difficulties from the alignment and assembly of a thin film specimen with the testing instrument. In [6], an on-chip tensile testing setup was fabricated and integrated using the MUMPs process. However, the test specimen is limited to the poly-silicon film only. This study demonstrates a novel micro tensile testing instrument with replaceable testing specimen using a parylene passivation technique. Parylene is a very inert chemically to the various etches tested, it only had a significant etch rate in the oxygen plasma. Parylene is also biocompatible and has relatively low gas permeability [7]. Thus, parylene can be used to protect the test specimen during etching proce
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