MEMS Technology and the Pursuit of the Ideal Switch (RFMW Blog)

May 16, 2022

RFMW Blog — May 16, 2022 

MEMS technology and its applications have taken quite a long time to develop. The origins of Microelectromechanical Systems date back to the mid-1970’s but it took nearly another quarter-century for the first commercial MEMS product to be introduced. This was Analog Devices’ ADXL50 accelerometer , which established the company as the pioneer in turning what had been a promising idea into a commercial product.

MEMS sensors and actuators are now widely available from hundreds of vendors, and MEMS accelerometers, for example, have been the universal choice for use in airbag deployment circuits by the automotive industry since the mid-1990s. Digital micromirror devices (so named for their ability to be digitally controlled) have also been used for years to form optical images on projector lenses on movie theatre screens. MEMS-based Inertial Measurement Units are also in widespread use for navigation systems, and other MEMS applications include miniaturized microphones, speakers, energy harvesters for environmental sources, sensors for measuring pressure, gas, and temperature, and several types of strain gauges.

Conspicuous in its absence from this list is the switch, for which MEMS technology is logically an ideal application, as a switch has movable parts (a fundamental feature of MEMS in general). However, a microelectromechanical switch is different than any other type of MEMS device, so much different that developing and commercializing a reliable MEMS switch product has eluded researchers for the past 40+ years. These efforts consumed the resources of many companies, causing nearly all of them to exit the field before they could achieve commercial success. In addition, almost all these efforts were focused on purely RF applications, to the point where MEMS switches had become synonymous with RF MEMS.

Today, only a few companies remain in the field of MEMS switches, principally Analog Devices, Cavendish Kinetics (now Qorvo), who are both focused on RF applications, and Menlo Micro. All three companies have developed their own specific, often proprietary, techniques that have taken many years of effort and funding to realize. Prior to Analog Devices, Cavendish Kinetics, and Menlo Micro, there were dozens of development efforts, dating back to the 1980s, to bring a reliable and cost-effective MEMS switch to market. The reasons why these efforts came up short are numerous, such as limited resources, a lack of fabrication facilities and control of the fabrication process, and most importantly, the inability to find the right materials to solve the unique challenges required to fabricate MEMS switches with the reliability, manufacturability, performance, and the low-cost requirements of a commercial product.

There are good reasons why so much effort and resources were expended on MEMS switch development. A MEMS switch can potentially replace electromechanical and semiconductor switches in their core applications, especially in test and measurement and RF and microwave systems. They are smaller and lighter, consume very little power, switch at high speeds, have almost no insertion loss and very high isolation, can potentially operate well into the millimeter-wave region, and generate little intermodulation distortion—all delivered within the confines of a tiny package.

While Analog Devices and Cavendish have developed commercially available RF MEMS switches, no one has been able to develop MEMS technology that would allow the switch to be used for both RF and high-power applications. The holy grail has always been a universal MEMS switch, able to handle RF up to GHz and AC/DC power up to kV. Menlo Micro’s Ideal Switch™ is proving to be that universal MEMS switch.

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