By Hank Hogan
SCOTTSDALE, Ariz.—For years, researchers developing microelectromechanical systems (MEMS) have demonstrated working contraptions smaller than a grain of sand—work that has garnered more than just an academic interest.
Now, the technology of tiny moving parts is poised to have a substantial and growing impact on the contamination control market. In-Stat/MDR, a market research firm here, is releasing a new study that shows big growth in small machines.
“On a unit basis, 2002 to 2007, the compound annual growth is estimated at 29.2 percent,” says Marlene Bourne, a senior analyst at In-Stat and author of the study. “From a revenue perspective, the compound annual growth rate is 16 percent.”
Analog Devices (Norwood, Mass.) claims to have shipped more than 100 million MEMS accelerometers, just one type in .a MEMS array that includes micromachined gyros, pressure sensors, ink jet nozzles and micromirrors.
Bourne notes, however, that the total MEMS market is still fairly small. The semiconductor industry generates more than $150 billion in annual revenue. The same can't be said of MEMS.
“In terms of revenues in 2002, we're looking at $3.7 billion. In 2007, at $7.9 billion,” comments Bourne.
According to industry participants, much of MEMS technology, processing, and contamination control is derived from semiconductors. There are, however, crucial differences—movement, materials amd size—that bear on MEMS as a consumer of contamination control products and services.
The first difference is that MEMS devices, or key parts of the devices, move. This means that a MEMS product, unlike an immobile integrated circuit, can't simply be coated with a final passivation layer to protect it from the elements.
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For example, The Omron Corp. (Kyoto, Japan) has just released a new flow controller built with its proprietary MEMS technology.(Figure 1). That enables the company to produce a device one-seventh the size of others in its class. But the mechanical nature of MEMS devices requires special contamination control techniques in manufacturing.
“Because of the moving parts, packaging technology built on environment-enduring sealing technology is most important,” says Tomonori Seki, a senior research engineer at Omron's MEMS group advanced device laboratory.
As for materials differences, MEMS devices may make use of gold or other constituents that are deadly to standard semiconductor processing. The typical practice is to isolate MEMS tools, either within a larger semiconductor fabrication line or in a completely separate facility. Careful design of the manufacturing flow, notes Seki, prevents material cross-contamination problems. As attempts to incorporate MEMS in semiconductor manufacturing continue, the materials issue will remain a concern.
On the other hand, with regard to size, MEMS processing is actually more forgiving than that of semiconductors—and that could mean renewed life for old cleanrooms.
Surface Technology Systems plc (Newport, U.K.) makes tools, such as its Pro family of etch and deposition equipment, for MEMS manufacturing. Stuart Watcham, director of marketing at STS, notes that many MEMS processes take place in ISO Class 6 or Class 7 cleanrooms.
“MEMS are larger devices [than semiconductors] and can tolerate being manufactured in slightly lower levels of cleanliness in terms of cleanrooms,” Watcham adds.