Microwave Engineering Europe - November 2008 - (Page 16) 16 MEMS MEMS market demands new foundry strategies By Loring Wirbel , Director, EE Times Market Intelligence Unit hen Freescale Semiconductor transferred a MEMS process from Sendai, Japan, to its Oak Hill fab here earlier this year, the company didn’t make a lot of noise about a new business strategy to accompany its second internal source. Freescale now offers MEMS foundry services at its Austin fab, and will work with product developers on a range of thin-film materials and processes to optimize MEMS for specific applications. The MEMS foundry effort, also adopted by TSMC, indicates the maturation of the MEMS industry from an early focus on highvolume actuator products, such as inkjet printer heads, to a wealth of sensor products serving automotive, consumer product and communication markets. In fact, the smaller volumes and balkanization of device types in newer markets has skewed the ranking of manufacturers in the MEMS Top Ten compiled by iSuppli’s WTC. HP, dominant in the printer world, remains in the number two slot, exceeded only by Texas Instruments (in the lead due in part to its heavy digital micromirror presence), and followed by Canon and Robert Bosch. But if diversity of product type were taken into account, Freescale, Analog Devices, Avago Technologies and other players would get wider recognition. Surface MEMS manufacturing, in which thin-film micromachined layers are added to an existing semiconductor, is more ripe for commoditization than bulk MEMS, though both manufacturing environments may be ready for foundry businesses, according to Chris Magnella, director of operations for Freescale’s Oak Hill fab. Freescale’s Austin MEMS business was intended as a dual-source operation for automotive MEMS produced in its Japan fab. But as the manufacturing line was ramped up in Texas, Magnella said, it became clear that a better strategy would involve bringing up consumer products first in the Austin fab, due to the greater need for zero-defect manufacturing in automotive applications such as tire pressure sensors and electronic stability control accelerometers. As product developers within Freescale started considering the diversity of W accelerometer and motion-sensing products that could be offered for consumer markets, the thought of offering some fab capacity for foundry services started to make more sense. Four drivers “We identified four drivers for moving to MEMS foundry,” Magnella said. “First and most obvious, it’s a good business.” “Second, we learn a lot from the diversity of materials and process methods we get to work with.” “Third, our menu of offerings can grow over time, particularly when we add the capabilities of our Chandler wafer backend processing operation to our Oak Hill business.” “And fourth, the talents we offer to outside customers line up very nicely with our internal product development plans.” As players with standard MEMS products move into foundry services, they must compete against dedicated foundry businesses from players like Innovative Micro Technology (Santa Barbara, Calif.), Asia Pacific Microsystems (Hsinchu, Taiwan), and Dalsa Semiconductor (Waterloo, Ontario). WTC-iSuppli reports a significant degree of “hidden” foundry services as well — for example, STMicroelectronics produces as much as half of HP’s inkjet printer components, and Sony serves as a foundry for Knowles Electronics, a leading producer of silicon microphones. Market size TSMC has estimated the global MEMS market for commodity and captive devices will hit $7.3 billion this year, based on Yole Developpements’ projection of a global MEMS market of $8.8 billion in 2012. Of this total, less than $200 million is realized in foundry as traditionally defined, but Magenella said this could change quickly in the next year or two. This year, total sensor sales exceeded actuator sales for the first time. As consumer and mobile-phone applications begin to overtake the printer head and micromirror business, Magnella predicted there will not be a single “killer app” in the accelerometer field that racks up very high volumes, but a wide array of niche products realizing moderate volumes. That kind of market can be well-served by foundries, he said. Freescale has pioneered its own device structure intellectual property (IP), such as high-aspect-ratio devices to improve accelerometer sensitivity. The company has comfortably integrated unique IP from outsiders into surface machining on its CMOS process, and already has completed MEMS-over-IC designs with one major customer. Manufacturing challenges Difficulties in implementing MEMS components thus far have not been encountered in device structure or film deposition, Magnella said, but only in something as mundane as bowing and stress on the wafer itself. Because the surface is micromachined before the wafer is separated into separate dice, mechanical stress on the wafer often is the toughest challenge on the manufacturing line. Conventional wisdom would suggest that consumer MEMS products have to follow more brutal average selling price trends than automotive devices, but it’s not necessarily so, Magnella said. Since the collapse in auto sales due to high gas prices, MEMS accelerometers in automobiles have faced as tough a pricing environment as any consumer product. The issue for Freescale and others in medium-volume foundry applications then becomes one of manufacturing devices inexpensively enough to meet end-product pricing goals, while taking into account that manufacturing volumes may never hit those realized for hearing aids or inkjet printer heads. “In five years, the experience base will be there for two-poly MEMS in the accelerometer world, for stacked MEMS on ICs, and living with price constraints will seem the most natural thing in the world,” Magnella said. “But MEMS foundries have to go through the same learning curve that digital CMOS foundries did.” “The nice thing is that we don’t have to push feature sizes of the semiconductor process.” Reprinted courtesy of EE Times Microwave Engineering Europe ● November 2008 ● www.mwee.com http://www.mwee.com
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