Effect of silicon nitride coating thickness on fatigue of silicon microbeams |
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| Affiliation: | 1. Faculty of Mechanical Engineering, TU Ko?ice, Department of Design, Transportation and Logistics, Letná 9, 040 01 Ko?ice, Slovak Republic;2. Faculty of Mechanical Engineering, TU Ko?ice, Department of Applied Mechanics and Mechatronics, Letná 9, 040 01 Ko?ice, Slovak Republic;1. School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore;2. Department of Mechanical Engineering, National Institute of Technology, Rourkela 769008, India;1. Department of Mathematics, Khorasgan Branch, Islamic Azad University, Khorasgan, Isfahan, Iran;2. Department of Mathematics, Mobarakeh Branch, Islamic Azad University, Mobarakeh, Isfahan, Iran;3. Department of Science, Bushehr Branch, Islamic Azad University, Bushehr, Iran;1. Dept. ELEC, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium;2. University of Gävle, Kungsbäcksvägen 47, 801 76 Gävle, Sweden;3. Dept. SURF, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium;1. WorleyParsons Canada, Edmonton Operations, Canada;2. Department of Mechanical Engineering, University of Alberta, Canada |
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| Abstract: | In this paper, two silicon nitride layers with thickness, 0.2 and 0.4 μm, are coated onto single crystal silicon (SCS) in order to achieve Si3N4/Si cantilever microbeams. The effect of LPCVD silicon nitride surface coatings on fatigue properties of SCS cantilever microbeams is investigated. Fatigue testing is conducted at both 40 Hz and 100 Hz. Typical S–N (strain amplitude–fatigue cycle) curves of the beams are achieved and correlated fatigue failure modes are investigated. It is found that thinner Si3N4 coating of 0.2 μm results in better fatigue lives of Si3N4/Si beams than thicker Si3N4 coating of 0.4 μm. Both thinner and thicker coated beams have major fatigue crack planes along {1 1 1} planes; however, thicker coated beams possess specific failure mode of delamination, which is not found in thinner coated beams. Delamination reduces the reinforcing effect of thicker Si3N4 coating and leads to its shorter fatigue life. For thicker coated beams, fatigue life at 100 Hz is longer than that at 40 Hz. The mechanism for delamination and the effect of cyclic frequency is investigated, and factors for better fatigue life are proposed. |
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| Keywords: | Silicon nitride Thickness Coating Fatigue Cyclic frequency Delamination |
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