Martin Lim

Versatile CMOS-MEMS integrated piezoelectric platform

We present the extension of the InvenSense fabrication platform to piezoelectric transduction. The newly proposed CMOS-MEMS Integrated Piezoelectric Platform inherits the wafer bonding advantages of its predecessor, leverages existing semiconductor infrastructure, and is applicable to a wide range of applications.

Monolithic 591×438 DPI ultrasonic fingerprint sensor

This paper presents a 591×438 DPI ultrasonic fingerprint sensor. The sensor is based on a piezoelectric micromachined ultrasonic transducer (PMUT) array that is bonded at wafer-level to complementary metal oxide semiconductor (CMOS) signal processing electronics to produce a pulse-echo ultrasonic imager on a chip. To meet the 500 DPI standard for consumer fingerprint sensors, the PMUT pitch was reduced by approximately a factor of two relative to an earlier design. We conducted a systematic design study of the individual PMUT and array to achieve this scaling while maintaining a high fill-factor. The resulting 110×56 PMUT array, composed of 30×43μm2 rectangular PMUTs achieved a 51.7% fill-factor, three times greater than that of the previous design. Together with the custom CMOS ASIC, the sensor achieves 2 μV/Pa sensitivity, 13 kPa pressure output, 75μm lateral resolution, and 150μm axial resolution in a 4.6 mm × 3.2 mm image.

11.2 3D ultrasonic fingerprint sensor-on-a-chip

The increasing popularity of mobile devices such as smart phones in applications including smart payments and personal health sets a pressing need for improved security without compromised ease of use. Fingerprint recognition has emerged as a particularly attractive option. Unfortunately, present capacitive solutions suffer from poor accuracy in the presence of contamination such as perspiration, and in addition are easily compromised, e.g., with fingerprints recovered from the device surface.

A 6×5×4mm 3 general purpose audio sensor node with a 4.7μW audio processing IC

We present a complete, fully functional energy-autonomous audio sensor node with 6×5×4mm3 form factor. The system uses a new audio processing IC integrated with a MEMS microphone, general purpose 32-bit processor, 8Mb Flash, RF transceiver with custom 3D antenna, PV cells for energy harvesting and battery. The 4.7μW audio processing IC performs audio acquisition with 4–32× compression. The complete stand-alone system achieves 38mins of speech recording and energy-autonomous operation in room light.

The age of sensors - How MEMS sensors will enable the next wave of new products.

This paper covers a brief history of MEMS and the current status of mainstream MEMS sensors, then goes on to discuss how the availability of these low cost ubiquitous sensors is enabling several major market inflections. These inflections often require complete ecosystems to be developed, from unique technologies that enable new capabilities at the component level, to disruptive new services for end customers. However, value is disproportionally captured by companies supplying the end service, and not by those supplying the core fundamental components. The fact that relatively low cost “commodity” parts can enable these inflections and help create massive new value underlines the challenges being faced by many semiconductor companies. To drive growth, component suppliers need to find a way to capture more value from the inflections they enable.