MEMS, Microfluidics and Microsystems Executive Review: A Universal CMOS MEMS Process?

Unlike the semiconductor industry, MEMS devices have been traditionally manufactured using a variety of highly-specialized processes geared for each specific device. This variety of MEMS fabrication processes has contributed to higher commercialization costs and longer times to market. While there are established MEMS processes such as Sandia’s SUMMiT and Microfabrica’s EFAB, a startup company Akustica is now promoting its CMOS MEMS process as a possible industry standard for monolithic CMOS MEMS devices. Akustica has focused on MEMS based microphones thus far, but the company claims that its process is versatile and can also be used to make monolithic RF and inertial MEMS products. We recently spoke with Akustica’s CTO Ken Gabriel.

MEMS Investor Journal: How does Akustica differentiate CMOS MEMS from other MEMS platforms that claim to be CMOS MEMS platforms?

Ken Gabriel: CMOS MEMS is a technological breakthrough in monolithic transducers. The uniqueness of Akustica’s CMOS MEMS technology as compared to other integrated MEMS fabrication processes that are described as "CMOS-compatible" is that CMOS MEMS structures are not fabricated in thin films on top of CMOS, but instead are fabricated in the CMOS as part of the CMOS process itself using the metal-dielectric layers that are deposited during the standard processing flow as the structural materials. Fundamentally, CMOS MEMS is CMOS. The metal dielectric layers that comprise the mechanical MEMS structures are the same layers that form the electronic circuits. These circuits are integrated with the MEMS structures and are typically located only tens of microns from the MEMS structures.

MEMS Investor Journal: What are the main limitations of your CMOS MEMS process?

Ken Gabriel: Frankly, we do not see any limitations. There are unique integration challenges which we've overcome, and as a result, CMOS MEMS has proven to meet or exceed customer expectations for product performance, reliability and cost.

Our difficulty is not with specific products; rather it is selecting from the wide variety of products we can pursue on the platform. At present, Akustica has chosen to pursue microphones rather than inertial or RF MEMS.

MEMS Investor Journal: Where has the Akustica CMOS MEMS platform been applied thus far? Where are the digital microphones being designed in?

Ken Gabriel: Laptop PC makers have been very enthusiastic to deploy Akustica digital microphones in their voice over IP platforms to dramatically improve voice-input quality. We have announced a few platforms with Fujitsu, a recognized innovator in the PC OEM market. There are many more to follow this year as all PC makers prepare new platforms for Intel's Centrino Pro launch.

MEMS Investor Journal: Why are they being designed in?

Ken Gabriel: For three main reasons - RFI/EMI Immunity, small size and guaranteed uniformity.

MEMS Investor Journal: What are the top three objections which you are hearing from your customers?

Ken Gabriel: The main objection we hear continues to be skepticism since MEMS have never been made using only the metal layers within a standard CMOS wafer. We can understand this source of doubt since MEMS devices have historically been manufactured using captive processes in MEMS-specific foundries. However, once customers understand our technology and see that we can actually achieve this, it no longer becomes an objection.

MEMS Investor Journal: What other application areas, beyond silicon microphones, is Akustica targeting with CMOS MEMS?

Ken Gabriel: We continue to develop next-generation acoustic, inertial and RF products. Prototype accelerometers have been demonstrated using the exact same CMOS MEMS process and supply chain.

MEMS Investor Journal: What does CMOS MEMS bring to each of these application areas? How will Akustica CMOS MEMS devices compare to existing devices?

Ken Gabriel: The benefits of CMOS MEMS are apparent, regardless of application. Consumer markets by definition are fast-moving and cost-sensitive. By leveraging the global semiconductor foundry infrastructure and readily available design tools and models, CMOS MEMS can move just as quickly to integrate multiple functions on a single chip for maximum cost-effectiveness.

MEMS Investor Journal: When does Akustica expect to roll out CMOS MEMS devices targeting these markets?

Ken Gabriel: It’s too soon for me to say. We are in the early phases of exploring and evaluating additional market entry partnerships.

MEMS Investor Journal: How is Akustica differentiating its MEMS microphones from competitors such as Knowles Acoustics and Sonion MEMS?

Ken Gabriel: The digital chip Akustica unveiled in February last year is the first (and still the only) single-chip MEMS microphone on the market. Our microphones put a transducer and all the necessary signal processing and other features into a single chip. This ultimately gives us a performance and size advantage, and provides manufacturing advantages as well.

MEMS Investor Journal: Some have claimed that Akustica's MEMS microphones are more expensive than competitive products. Could you please comment on that?

Ken Gabriel: The fact that customers are buying so many of our microphones validates the importance of performance over price. It is also true that in quantity, our microphones are competitively priced with alternate solutions.

MEMS Investor Journal: Which specific aspects of performance do you mean?

Ken Gabriel: Our single-chip microphones enable a superior system signal-to-noise ratio vs. alternative solutions. This translates into more realistic-sounding voice conversations and higher clarity in the voice input, regardless of the RF/electromagnetic environment. The enhanced quality of the voice input signal provides both a superior sounding system for VoIP applications as well as an improvement in speech recognition accuracy for voice-controlled applications.

MEMS Investor Journal: Infineon recently introduced its own MEMS microphone. What are your thoughts?

Ken Gabriel: Many companies have announced MEMS microphones, only a few have been verified to be manufacturable.

MEMS Investor Journal: Is Akustica planning to do another round of VC financing soon?

Ken Gabriel: As a privately held company, we do not speculate about future financing.

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Dr. Ken Gabriel is recognized worldwide as the architect of the MEMS industry. In 1985, Dr. Gabriel pioneered the MEMS field and led the development of IC-based MEMS while working at AT&T Bell Labs. Prior to co-founding Akustica, he served as Professor of Electrical & Computer Engineering at Carnegie Mellon University’s Robotics Institute.

Dr. Gabriel spent five years with DARPA, where he started and managed their MEMS program as Director of the Electronics Technology Office and was responsible for roughly half of the U.S. Government’s electronics technology investments. He has also been a visiting professor for the Institute of Industrial Science at the University of Tokyo, heading joint research projects with IBM, Toyota and Ricoh, as well as a visiting scientist at the Naval Research Laboratory.

He has helped found two other successful technology companies and serves on advisory boards for three others.

Dr. Gabriel holds an S.M. and Ph.D. in Electrical Engineering and Computer Science from MIT.