A Hybrid RF MEMS Switch Actuated by the Combination of Bidirectional Thermal Actuations and Electrostatic Holding

• Published in: IEEE transactions on microwave theory and techniques 2020-08, Vol.68 (8), p.3461-3470
• Main Authors: Chae, Uikyu, Yu, Hyun-Yong, Lee, Changhyuk, Cho, Il-Joo
• Format: Article
• Language: English
• Subjects: Actuation; Actuators; Bidirectional actuation; Electric potential; Electrodes; electrostatic holding; Electrostatics; Force; Insertion loss; low actuation voltage; Mechanical properties; Mechanical systems; Metals; Microelectromechanical systems; Microswitches; Power consumption; Radio frequency; Radio frequency microelectro-mechanical system (RF MEMS) switch; Stiction; Switches; thermal actuation; Voltage
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2020.3003553

Radio frequency microelectro-mechanical system (RF MEMS) switches have received attention due to their higher performances at high frequencies compared with semiconductor-based switches. However, most of the previous MEMS switches used electrostatic actuation, which requires a high actuation voltage and has a low actuation force. Herein, we propose a new hybrid RF MEMS switch for low-voltage and low-power operation that is actuated by the combination of bidirectional thermal actuation and electrostatic holding. The proposed hybrid RF MEMS switch is actuated by the combination of two actuation mechanisms, i.e.: 1) bidirectional thermal actuation of the large force with low actuation voltage and 2) electrostatic holding for low-power consumption. The large actuation force enables high signal isolation at the "OFF" state of the switch because of the high initial gap between the signal line and the contact metal. Also, the bidirectional thermal actuator that enables upward actuation prevents any stiction of the membrane, which enhances both the power handling capability and the reliability of the actuator. In this work, we successfully fabricated the proposed RF MEMS switch and measured both its mechanical characteristics and RF characteristics. The required actuation voltage for the switch is less than 0.3 V for thermal actuation, and the required voltage for electrostatic holding is 15.4 V. The power consumption was measured as 3.24~\mu \text{J} per switching. Also, we measured the RF characteristics, and the insertion loss of signals was 0.23 dB at 2.4 GHz, and the isolation of signals was 38.80 dB at 2.4 GHz.