MEMS Microphones Enjoying Dynamic Times, Resurgence in Attention

By Jérémie Bouchaud, Principal Analyst, and Richard Dixon, Senior Analyst, MEMS, iSuppli


MEMS microphones are under the spotlight this year with two major acquisitions in the last few months. In May, EPCOS bought Pulse Engineering, while just a few weeks back in August, Bosch acquired Akustica. Despite the recent attention, MEMS microphones are not really new. Knowles, an acoustic component manufacturer also producing conventional Electret Condenser Microphones (ECM), pioneered silicon MEMS microphones 20 years ago initially (with R&D started in 1988) for high-end applications at NASA. The company started to ship to cell-phone companies in 2003. Volumes have grown very rapidly since then, and Knowles announced in August its 1 billionth MEMS microphone (see News section).

Not surprisingly, Knowles is not alone, and iSuppli has identified nine companies currently shipping MEMS microphones to customers and another three sampling or in the R&D phase. Will the market be big enough to feed these companies? In answer to this, iSuppli has just published a report on MEMS microphones, the findings of which we summarize in this issue’s MEMS market brief.


Figure 1: Silicon MEMS Microphone Market

Market Overview

The market for MEMS microphones was in the range of $135 million in 2008 and will more than double in revenue by 2013 to exceed $300 million. By this time, more than a billion units will be shipping annually.

The main applications today and in the future include cell phones, far in front of laptops, and headsets in third place. iSuppli’s Teardown Service also found MEMS microphones in other consumer electronics equipment, such as video cameras (see Teardown of the Month section), and MEMS microphones will also find their way in the near future into ultra-thin DSCs and possibly MP3 players. Noteworthy, suppliers like MEMSTech and Omron also serve the industrial and security markets. In addition, iSuppli has investigated automotive and medical applications, but contrary to other what analysts say, we do not believe that MEMS microphones will ship in this sector in series by 2013.

First Bump in the Road for MEMS Microphones

MEMS microphones have not had a completely smooth ride, hitting a bump in the road in 2009 , as a result of Motorola’s freefall in the mobile handset market. Motorola was the first company to widely adopt MEMS microphones for its mobile handsets, especially the best-selling ultra-thin RAZR, and has adopted MEMS microphones for almost all its phones.

With Motorola dropping from its place as the No. 2 handset manufacturer in 2006 to No. 4 in 2008 and continuing to lose market share in 2009 (source: iSuppli “Wireless Handset Market Shares through Q2 2009”), this has significant implications for the development of the MEMS microphone market. Through numerous iSuppli teardowns, we have been able to estimate the penetration and consumption of MEMS microphones at the top cell-phone makers. The significant growth of MEMS microphones at other handset makers cannot compensate for Motorola’s decline, as Figure 2 clearly indicates.

If one were to superimpose on this the lower overall shipments of cell phones this year by 12% (source: iSuppli Wireless Systems Q2 2009 Market Tracker), as well take into account the significant price erosion this results in a close to modest growth of the overall MEMS microphone market in units and 2% decline in revenue this year.


Figure 2: Motorola’s Freefall Impact on Shipment of MEMS Microphones in Mobile Handsets


MEMS microphones still sell at a higher price than the traditional ECM microphones, from less than $0.35 for analog microphones in high volumes at cell-phone companies to more than $0.80 for digital MEMS microphones selling in high-end acoustic equipment. What justifies this price premium?

If you ask MEMS suppliers, some will describe the ECM as an outdated technology and will start off on a long list of decisive advantages imparted by MEMS. Another group of ECM detractors, consisting of MEMS microphones developers, are in the same camp—even though they conveniently neglect to mention that ECM has not been standing still in the last few years. In this regard, iSuppli asked electronic equipment makers (i.e., leading cell-phone makers), both in the acoustic purchasing and research department, to furnish us with their views.

In essence, being an SMD (surface-mount device) is no longer a true Unique Selling Point (USP) for MEMS. There is no decisive advantage that is true for all possible customers, and each OEM will have its own motivation for choosing to implement MEMS instead of ECM technology. Some choose the form factor delivered by MEMS microphones for integration in ultra-thin phones or cameras, and some do so because they want a digital output; some will favor MEMS microphones for their fast ramp-up (or ramp-down), and yet others will make the choice based on performance.


Motorola RAZR gave momentum to MEMS microphones


Motorola RAZR exploded view


Teardown showing Knowles MEMS microphone (Source: iSuppli Teardown Analysis)

Is the Future Digital?

In fact, MEMS offers a better technology alternative for microphones with digital output than does ECM. This is the reason digital MEMS microphones from Akustica and Knowles are so popular among laptop manufacturers. In laptops the audio signal transits behind the LCD screen where there is strong EMI. A digital MEMS microphone is immune to this interference.

If MEMS microphones work beautifully with laptops, can they do the same with phones? Some trends favor the use of digital microphones in future mobile handsets:

  • Increasing EMI issues in some handsets as the antenna is buried deeper in the device or as smart phones become more complex.
  • New functionalities, such as noise cancellation and beam forming, can benefit from digital signals.
  • A standard interface is emerging—SLIMBus—that should ease implementation of digital acoustic signals.

OEMs remain very comfortable with analog signals, though. Digital MEMS microphones were found by the iSuppli Teardown Service only in Nokia’s handsets, while all the other handsets examined by Teardown used analog microphones. iSuppli believes that the share of digital microphones in handsets will be modest until 2012.


Ultra-small-size analog MEMS microphone (3.76 x 2.95 x 1.1 mm, KRM0300), microphone transducer, and ASIC from Infineon (Source: Hosiden)

The Second Source Issue

At present, MEMS microphones are shipped from nine companies. While this sounds like a flourishing trade, the reality is markedly different. The market leader—Knowles—will account for 85% of the market in 2009, leaving the other eight far behind. Last year, no other company exceeded 7 million units. The fact that one company dominates the market so overwhelmingly is an issue for cell phones, as some OEMs have no wish to rely on one source and are therefore reluctant to switch to MEMS microphone technology.

This year, Infineon and MEMSTech are finally emerging from the mass of small players as second and third sources in significant volume, and both are currently expanding production capacity. Noteworthy, these two companies are partnering with leading ECM companies for the commercialization of MEMS microphones.

What will the supplier landscape look like in 2013? One must differentiate from the high-volume supply in cell phones—with low margins—competing against the ECM on price on the one hand, and against the suppliers on the other hand for higher-end equipment that compete on performance (e.g., the emerging companies ADI and Wolfson). Generally speaking, these observations can be made:

  • There is room and enough segments on the higher end of the market for three to four players.
  • On the lower end, it is not clear whether a second supplier will be successful with fully packaged MEMS microphones to compete along with Knowles against the ECM makers. iSuppli believes, however, that an interesting opportunity exists for MEMS companies to supply microphone dies and ASICs to ECM companies that can package the microphones and sell them by using existing networks. This is the model deployed by Infineon today with Japanese ECM maker Hosiden. Wolfson has also recently started doing the same with other ECMs companies. This way, MEMS companies benefit from the existing brand and sales channels of the established ECM companies and hope to keep higher margins, selling silicon and shrinking die sizes.

iSuppli has just published a thorough analysis of the microphone market and supplier landscape in a 100-page report. The documents include detailed units, ASP revenue by application, and type of microphone (analog versus digital), as well as the profiles of 14 suppliers with their status of commercialization and suppliers’ agreement. Also included is a database of over 75 end products (cell phones, laptops, and cameras) that feature MEMS microphones.

Chipworks: Inside Analog Devices’ New MEMS Strategy

St. J Dixon-Warren, Manager, Process Analysis, Technical Intelligence, Chipworks Inc.

Analog Devices has recently changed their MEMS strategy. Since the introduction of the ADXL50 in 1991, Analog has built their MEMS inertial sensors using their iMEMS technology, which integrated the micromechanical structures and ASIC circuitry on a single die. The development of this technology culminated, in some respects, with the ADXL330, which was launched in 2006. The ADXL330 provided three sense axes in a 4 mm × 4 mm × 1.45 mm LFCSP package. An X-ray of the ADXL330 package, which contains a single integrated chip, is presented in Figure 1.

Figure 1 ADXL330 Package X-Ray

Figure 2 shows that the ADX330 MEMS sensor was fabricated as a single chip, with the MEMS structure in the centre of the die, beneath a hermetic cap, and the ASIC circuitry around the outside edge. The ASIC circuitry uses a single metal, single poly 3 µm BiCMOS process, while the MEMS is fabricated using three layers of polysilicon, with the top 4 µm thick poly 3 being used to form the MEMS structures, as shown in Figure 3.

Figure 2 Decapsulated ADXL330 Chip

Figure 3 ADXL330 MEMS Structures

The integration of BiCMOS and MEMS process technology onto a single die represented a significant technological achievement; however, the price of this integration was significant limitation on the complexity of the circuitry available to device designers, and limitations on the range of MEMS processing possible.

After more than twenty years, Analog has decided to abandon their integrated iMEMS technology, and adopt the more common strategy of using a separate MEMS die and ASIC die wire bonded together in a single package. The ADXL345 represents one of the first examples of Analog’s new strategy.

Figure 4 shows an X-ray of the ADXL345 3 mm × 5 mm × 1 mm LGA package. The X-ray clearly shows the presence of a separate ASIC die and MEMS die, with a hermetic cap. The internal structure of the device is more clearly seen in the SEM micrograph of the decapsulated device, Figure 5.

Figure 4 ADXL345 Package X-Ray

Figure 5 Decapsulated ADXL345 MEMS and ASIC Die

Abandoning their integrated iMEMS technology brings a number of benefits for Analog Devices. It allows the use of more advanced process technology in the ASIC, thus enabling greater functionality, including SPI and I2C digital outputs. It also allows them to more easily adopt a foundry strategy, with the possibility of separate foundries for the MEMS and ASIC die. Apparently, Analog has already started using TSMC to provide some MEMS foundry services.

Chipworks completed a full analysis of the ADXL330 in 2006. We are presently undertaking a detailed analysis of the ADXL345, which will include information on the process used to fabricate the MEMS and ASIC dies, plus a discussion of the MEMS architecture. For further information, please contact the author.


  • Analog Devices ADXL330 Three-Axis ±2 g MEMS Accelerometer Process Review (PPR-0602-801)
  • Analog Devices ADXL330 3-axis Accelerometer ICWorks Surveyor (MEMS) (ICS-0807-802)
  • Analog Devices ADXL345 Digital Accelerometer MEMS Process Review (MPR-0907-802)
  • Analog Devices ADXL345 3-Axis Accelerometer ICWorks Surveyor Report (MEMS) (ICS-0905-801)