MEMS Switches: On or Off?
For the purpose of this article, iSuppli provides an extended definition of RF MEMS. These are components such as:
RF MEMS relays from DC to microwave frequencies up to 100 GHz
RF MEMS switched capacitors, sometimes called varactors
Simple on-off MEMS switches that do not transmit a signal, as a replacement of conventional Reed-, mechanical snap- or even Hall switches
Status of MEMS Switches Today
The current status of the MEMS switch market is summarized in the table. Essentially, RF MEMS switches are produced in appreciable volume by Advantest, mostly for its own Automated Test Equipment (ATE) applications.
Table caption: Overview of activities in RF MEMS and MEMS switches (source, iSuppli) Click image for larger version.
Non-RF applications are essentially limited to medical applications such as smart pills, which can accommodate higher costs. Asulab and MEMSCAP are players here, although other companies like OKI are targeting this space.
Sampling today, in small volumes for evaluation at end customer but not yet implemented in series in real applications, are Panasonic and Omron for ATE and RF test, Radant for test in defense and civilian applications (Radant was unable to export outside the United States in the past due to its military funding and is now free to sell on the free market). Also sampling are WiSpry, with a varactor component for cell-phone applications and serial production expected this year (see this issue, news); and French utility company Schneider Electric. Schneider owns Kavlico (MEMS pressure sensors) and SDA (MEMS gyroscopes), and develops MEMS switches for its own industrial equipment and outside the group.
Development is very active at a number of companies like X-COM for military and instrumentation. Commercial samples should be available this year through its partner Teledyne, in addition to products being available from Baolab, a Spanish start-up looking to service cell-phone applications and planning to sample first devices in 2010. Maxim is aiming at instrumentation (ATE and RF), but there are also development programs at several semiconductor groups, including Fujitsu, Toshiba, Mitsubishi and Freescale, ADI, Alps, OKI, and at defense and aerospace companies like Raytheon, Rockwell, and EADS. The early stage of development of RF MEMS switches and varactors is taking place at Protronor Swedish start-up MultusMEMS.
The market for MEMS switches remains small (see Figure 1). But though still at the beginning of the curve, revenue dropped in 2008 as Magfusion went off the radar and the ATE equipment market collapsed in the second half of the year.
In 2013, iSuppli expects the total market to be in the range of $160 million. The main application fields will be mobile handsets, instrumentation, and defense and telecom infrastructure. What some consider an optimistic forecast is actually very conservative compared to projections from other analysts, who see an explosion of the market from $5 million in 2007 to $700 million in just five years (a CAGR of 168%)!
The major trends for RF components in mobile handsets are summarized as follows (from iSuppli's wireless team in its recent Topical Report, RF Components: Adapt or Die – Maybe Darwin Was Un to Something):
Tunable matching circuitry is a must for multimode, multiband handsets
New RF technologies for high data rates (HSPA+ and LTE) require higher linearity
Multiband PAs are being introduced to support both polar and linear transmit architectures
Considering its superior performance in linearity, RF MEMS switches and varactors are ideal candidates for impedance matching networks in front of a reconfigurable power amplifier, as demonstrated by RFMD and WiSpry, or for the antenna matching function, which is being pursued by EPCOS.
Caption: Tunable Impedance Matching Device (TIM), Tunable Digital Capacitor (TDC), and Antenna Tuner (TA) on 8" CMOS wafer (Courtesy: WiSpry)
iSuppli does not expect RF MEMS to be adopted by the majority of the market in the next four years for this function The reason is that emerging technologies such as ferroelectric varactors as well as CMOS switches from companies like Peregrine, which not only have made great strides but also have performed as well as MEMS in terms of linearity.
In addition, there are only two credible candidates for supplying RF MEMS switches and varactors in the next three years—WiSpry and EPCOS—although other companies to watch are Skyworks and Baolab.
While the potential market for MEMS switches in ATE and RF Test well exceeds $100 million, iSuppli expects that MEMS will have grabbed only a portion of it by 2013. MEMS have been used since 2005, but iSuppli does not expect a significant uptake before 2011 or 2012 for the following reasons:
The ATE market is in a slump along with the entire manufacturing and test equipment chain for semiconductors today. This slows the implementation of new technologies.
While test companies love RF MEMS in theory, iSuppli has noticed a growing skepticism/caution regarding its adoption. This follows the bankruptcy of several suppliers with which test companies have cooperated, as well as repeated issues with MEMS reliability.
Finally, experience shows that a number of iterations occur in the design of MEMS switches and relays for test companies, and that it often takes several years to go from commercial sampling to serial implementation.iSuppli also takes note of a growing interest in MEMS switches (and not relays) as simple on-off switches to function as replacement for Reed switches in other industrial applications. Schneider Electric is the company to watch in this space.