MEMS die size grows, test evolves, and other trends

December 26, 2011 — Yole Développement studies the evolution of inertial micro electro mechanical systems (MEMS) and magnetometers and provides reverse costing analysis of the MEMS devices in "Technology Trends for Inertial MEMS," volumes 1 & 2. The report considers 23 MEMS devices.

Four identifiable trends are revealed: future generation of sensors will deliver functions; sensor fusion, combining data from different sensors, is on the rise; new architectures are emerging; and price pressure is still very strong (5% drop per quarter for consumer applications), said Laurent Robin, activity leader, inertial MEMS devices and technologies at Yole Développement.

Yole’s report shares market drivers for inertial MEMS, including consumer, automotive, and high-end applications. Packaging and test trends for the devices are discussed. Over the last 3 years, inertial MEMS & magnetometers have been subject to dramatic market & technological evolutions. This has been driven by a large increase of the consumer market: mobile phones and tablets for accelerometers; gaming for gyros; mobile phones for magnetometers.

Along with “stand-alone” MEMS devices, inertial combo sensors, a combination of several inertial sensors into a single package, are also coming. Main applications are consumer (e.g. accelerometer with magnetometer or accelerometer with gyro) and automotive for ESC and rollover functions first.

On the technical side, form factor is ever decreasing with reduced footprint and thickness. And power consumption has been reduced to a few microA while performances are still increasing. The most successful type for inertial MEMS is based on capacitive transduction. Reasons are simplicity of the sensor element, no requirement for exotic materials, low power consumption and good stability over temperature. But will comb-drive architecture for accelerometers continue to be the main detection principle as MEMS die size keeps shrinking?

Regarding gyroscopes, most are falling into the categories of tuning vibrating fork/plate (STM, Bosch) or vibrating shells (Silicon Sensing Systems). This very common design gives ease of fabrication and possible integration in standard IC manufacturing industry.

For magnetometers, Hall Effect has been the dominant technology for a long time, but today it is changing as Magneto Impedance, Giant Magneto Resistance and Anisotropic Magneto Resistance are used. A new approach, Lorentz effect based on MEMS technology, is currently in R&D (VTT and others). This could bring easier integration in MEMS combo sensors.

"Testing has been also subject to strong evolution over the last years," said Dr. Eric Mounier, senior analyst, MEMS Devices & Technologies at Yole Développement. For example, combo sensors will require new test solutions compared to “stand-alone” sensors. Beyond the usual wafer-level electrical test and package-level electrical and mechanical or functional testing, these sensor combos will need module level testing and calibration of the combined sensors. If they include an MCU in the package, the communication between the sensors and the MCU will also need to be tested. Solutions need to be cost effective with high throughput to test multiple axes of multiple devices, either in parallel or in separate modules, rather like separate chambers in IC equipment.

The world of MEMS testing has moved in the last several years from internal development at MEMS makers to co-development with test suppliers to commercial off the-shelf equipment. So combo solutions that can test all axes of the module in a single tool for higher throughput will also likely be co-developed with the test equipment suppliers and available commercially. Assembly and test houses may also start to offer these test services on an outsource basis for fabless or fab-light MEMS makers. The Yole Développement report will analyze the latest trends in MEMS testing.

In order to understand the key evolutionary changes, a total of 23 different MEMS devices (9 accelerometers, 10 gyros, 3 combos and 1 magnetometer) — mostly consumer MEMS — have been disassembled, analyzed and cost simulations have been constructed for MEMS, ASIC and Packaging/Test. One of the key features of the reports is that ASICs have been analyzed as well. The MEMS have been analyzed and production costs have been simulated by System Plus Consulting, the reverse costing specialist company. The teardown analysis results have been compared in terms of performance, total cost, MEMS size, ASIC lithography node, ASIC size, package size, year for market introduction.

From its analysis, Yole Développement found there is a clear MEMS die size decrease over 2007-2011. For example, in 2008, the average size for an accelerometer (3-axis) was 4-5mm². 3 years later, size is about 2mm². ASIC size has been following the same trend with a lithography node in the range 0.18-0.35μ today. "With latest ST announcement about the use of through silicon vias for inertial, we can expect even lower cost and size in the future," said Robin. The same analysis has been performed for gyros comps, combos and magnetometers.

Companies cited in the report:
Accutronic, Advanced Microsensors, Advantest, Afore, Aichi, AIS/SSS, AKM, Analog Devices, ASE, Baolab, Bosch Sensortec, CascadeMicrotech, CEA Leti, Colibrys, Epson Toyocom, Freescale, Gladiator Technologies, Honeywell, Invensense, Jyve, Kionix, KYEC, Litef, Memsic, Multitest, Murata, Panasonic, Polytec, Qualtre, Rohm, Sensonor, Sensordynamics, Sony, SPEA, SSS, STM, Systron Donner,TEL, Teradyne, Thales, Tronics, VTI, VTT, Yamaha

Dr. Eric Mounier has a PhD in microelectronics from the INPG in Grenoble. He previously worked atCEA LETI R&D lab in Grenoble, France in Marketing dept. Since 1998 he is a co-founder of Yole Developpement, a market research company based in France. At Yole Developpement, Dr. Eric Mounier is in charge of market analysis for MEMS, equipment & material. He is Chief Editor of Micronews, and MEMS’Trends magazines (Magazine on MEMS Technologies & Markets).

Laurent Robin is in charge of the Inertial MEMS & Sensors market research at Yole Developpement. He previously worked at image sensor company e2v Technologies (Grenoble, France) and at EM Microelectronics (Switzerland). He holds a Physics Engineering degree from the National Institute of Applied Sciences in Toulouse. He was also granted a Master Degree in Technology & Innovation Management from EM Lyon Business School, France.

Yole Développement provides market research, technology analysis, strategy consulting, media in addition to finance services. Access the report catalog at www.yole.fr.

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