Sample geometry effect on mechanical property of gold micro-cantilevers by micro-bending test
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Research Letter
Sample geometry effect on mechanical property of gold micro-cantilevers by micro-bending test Kosuke Suzuki, Tso-Fu Mark Chang , Ken Hashigata, Keisuke Asano, and Chun-Yi Chen, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan Takashi Nagoshi, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8560, Japan Daisuke Yamane, Hiroyuki Ito, Katsuyuki Machida, Kazuya Masu, and Masato Sone, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan Address all correspondence to Tso-Fu Mark Chang at [email protected] (Received 27 February 2020; accepted 22 May 2020)
Abstract Sample geometry effects on mechanical strengths of gold micro-cantilevers are evaluated by a micro-bending test. Six micro-cantilevers with the same length of 50 μm are prepared, and the width and the thickness are varied to examine individual effects on the yield stress. The yield stress increases from 428 to 519 MPa when the thickness decreases from 11.1 to 6.0 μm. No obvious dependency is observed when varying the width. The results reveal that the thickness and the width each has a different influence on the yield stresses of micro-cantilevers evaluated by the bending test, which is the sample geometry effect.
Introduction Continuous miniaturization in microelectromechanical system (MEMS) devices while maintaining a high sensitivity is required to meet the requirements in diverse applications. Reducing dimensions of the MEMS component is an effective method to accomplish the miniaturization. Regarding the sensitivity, the Brownian noise of the main component is a critical factor needed to be considered, especially for MEMS devices requiring a low noise level, such as a MEMS accelerometer. The Brownian noise is inversely proportional to the overall mass of the component.[1] This implies an amount of volume (or mass) is needed to have a low noise level. Therefore, it is difficult to achieve miniaturization and high sensitivity at the same time. In our previous studies, a design of MEMS accelerometers composed of gold-based micro-components fabricated by lithography and electrodeposition is proposed to allow further miniaturization of the device.[2,3] The density of gold (19.3 × 103 kg/m3 at 298 K) is higher than most materials commonly used in electronic devices; hence, gold is an effective material for reduction of the Brownian noise. The dimensions of the MEMS accelerometer using gold-based materials as the proof mass can be reduced for nearly one order of magnitude when comparing to dimensions of conventional MEMS accelerometers. While at the same time, the Brownian √noise performance is maintained at a low level of 0.78 mg/ Hz (where g = 9.8 m2/s) at 300 K.[2] Gold is a common material in electronic devices because of the high chemical stability, corrosion resistance, electrical conductivity, and density. In addition, gold electrodeposition is a simple process for fabrications of components in MEMS
devices. On the other ha
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