A MATTER OF IP PROTECTION
As more companies try to enter the field, the issue of intellectual property (IP) protection looms larger, forcing established silicon MEMS microphone manufacturers to aggressively protect their patents with litigation. Court suits and rulings have been forthcoming. For example, the International Trade Commission (ITC) is in the process of making a final determination as to whether MEMSTech has infringed on Knowles Acoustics’ packaging patents.
“IP protection is an important issue that companies like us and Knowles Acoustics are trying to uphold,” says Marcie Weinstein, Akustica’s director of strategic marketing. “We have not licensed our CMOS MEMS or MEMS microphone IP to anyone.”
A few years ago, Akustica and Knowles Acoustics entered into a cross-licensing agreement. It gave each company the freedom to pursue the development, manufacturing, and delivery of MEMS microphones.
Knowles also filed an IP complaint with the ITC against AAC Acoustic Technologies in 2006. According to AAC’s Web site, the ITC denied Knowles’ motion for a preliminary injunction that bars AAC Acoustics from producing silicon MEMS microphones. Subsequently, the two companies resolved their differences and entered into a worldwide cross-licensing agreement. Cross-licensing agreements have also been reached between Pulse Engineering’s Sonion MEMS Division and Akustica.
CAVEAT EMPOTR
One thing should be clear for engineers looking to incorporate a silicon MEMS microphone in their designs: Most of these device manufacturers aren’t very forthcoming about providing “complete” specifications. Some offer product brief sheets. Others provide a few “highlight” performance specifications. Many don’t even have complete datasheets, if they have any datasheets at all. There’s a game of “specsmanship” going on that can use a lot of clarification.
Once many of these strategic relationships settle down, things should become clearer, and full and explicit datasheets will become the norm. Looking forward, it’s conceivable that more than one sensor function can be combined on the same MEMS chip holding the microphone transducer element, providing reduced packaging, testing, and overall processing costs.
A silicon MEMS microphone may yet be combined with an accelerometer in, say, a mobile phone. Or, multiple chips can be combined within one package. Smart 3D packaging approaches that use through silicon vias (TSVs) for interconnects may facilitate all of these developments.
Akustica demonstrated that MEMS inertial and RF functions can be manufactured on the same process being used to massproduce silicon MEMS microphones. The company has shown that a dual-axis accelerometer (a three-axis version is in development) can be made, as well as a capacitive membrane switch for tunable components and filters.