# Temperature Effects in Packaged RF MEMS Switches with Optimized Gold Electroplating Process
###### Abstract  
Due to its excellent electrical performance, mechanical reliability, and thermal stability, electroplated gold is still the most commonly used material for movable beams in RF MEMS switches. This paper investigates the influence of process conditions on the quality and growth rate of gold electroplating, and the optimized process parameters for the gold electroplating process are obtained. The characterization of the optimized electroplated gold layer shows that it has small surface roughness and excellent thermal stability. With this optimized gold electroplating process, the RF MEMS switches are fabricated and hermetic packaged. In order to obtain the temperature environment adaptability of the packaged switch, the influence of working temperature is studied. The temperature effects on mechanical performance (includes pull-in voltage and lifetime) and RF performance (includes insertion loss and isolation) are revealed. RF MEMS switch; gold electroplating process; temperature effects; pull-in voltage; lifetime +
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and composite stiffness of the movable beam [11]. [PERSON] et al. developed an SOI-based switch fabrication process. By using single-crystal silicon as the movable beam, the switch achieves a very short switching time and good mechanical stability [12]. By using standard 0.35 mm CMOS technology, [PERSON] et al. proposed an RF MEMS switch with a movable beam made of Al/SiO\({}_{2}\) composite material. Although the RF performance is not outstanding, its biggest advantage is that it can be mass-produced using mature CMOS technology [13]. [PERSON] et al. summarized the material selection and the fabrication technology of RF MEMS switches. Due to its excellent electrical performance, mechanical reliability, and thermal stability, Au is still the most commonly used movable beam material, followed by Al and Cu. The most commonly used manufacturing process for switches is the surface sacrificial layer process, followed by the bulk process. In addition, switch processes compatible with the CMOS process are also receiving increasing attention [14]. After fabrication, switches are usually hermetically packaged to improve their reliability. Packages can isolate dust and moisture in the environment. However, the temperature variation still may have an influence on the switches. To investigate the thermal effects on the reliability of RF MEMS switches, a current density model and a thermal model are coupled to calculate the current density, heat loss, and temperature rise of the switch [15]. [PERSON] et al. measured and discussed the variation of actuation voltage with temperature for clamped-clamped switches and cantilever switches. Experimental results indicate that the performances of cantilever switches are less influenced by the temperature [16]. They also established a lifetime model for the switches and used temperature as an acceleration factor to predict the lifetime of the switches [17]. [PERSON] et al. characterized the temperature acceleration of dielectric charging effects in RF mems switches. A charging model is provided to predict the amount of charging under different temperatures [18]. [PERSON] et al. studied the temperature effect on the mechanical and RF performance of the switch. However, they mainly focused on cryogenic temperatures that are below room temperature [19]. Based on our previous work [20; 21], this paper investigates the influence of process conditions on the quality and growth rate of gold electroplating. With the optimized gold electroplating process, the RF MEMS switches are fabricated and hermetic packaged. In order to obtain the temperature environment adaptability of the packaged switch, the influence of working temperature on the mechanical and RF performance of the switch is studied.