The material importance for reliable RF MEMS

For the past 150 years, the mechanical relay was one of the original building blocks of electrical systems, and for the past few decades many have sought to miniaturize this fundamental electrical building block through MEMS based technologies. The challenge is multidisciplinary in nature, drawing on sound RF design, fabrication processing, packaging and the materials that bring all these elements together. The goal is the near ideal switching element that will enable and drive future innovation in RF communications from handsets through infrastructure. Rooted from over a decade’s research in innovated materials and fabrication processes at GE Global Research, Menlo Microsystem (a GE spin-off) has developed an electrostatically actuated ohmic MEMS switch and relays products capable of switching in ~3usec with sub-ohm resistance while sustaining more than 250V across its open contacts. The materials innovations, based on years of methodical failure mode analysis taking into account material, mechanical and electrical constraints, have delivered creep resistant metal alloy beams and a highly reliable contact that provide reliable switch performance over both operational life and elevated temperature. When applied to RF applications, the ohmic switch is capable of <0.3dB insertion loss from DC to 3GHz and about 1dB insertion loss at 40GHz, combined with the ability to handle RF power of 50W at 900MHz and 25W at 3GHz. A critical advantage of an ohmic switch is linearity. The IP3 of the switch is over 90dBm with 2 tone of 43dBm at 850MHz. The cold switch life cycles is more than 10 billion with hot switching capability of 180 M cycles at 10dBm and more than 1 billion cycles at 0dBm with <5 mdB change in insertion loss over the cycle life. The miniaturization of the mechanical relay through MEMS technology, coupled with materials innovations, can enable a new class of wireless connectivity that more efficiently delivers higher data rates across a broader spectrum than today’s solid state devices. The unit cell scalability of this ohmic MEMS switch architecture enables its RF performance to effectively scale from mW (wireless handsets) to 100s W (wireless infrastructure). The combination of fast microsecond switching speed with high performance broadband (DC to RF) operation will enable the miniaturization of the mechanical relay for wireless communications, infrastructure and the Industrial IOT.