Page 18

EETE SEP 2015

semiconductors 3D fingerprint scanner beats Apple’s By R. Colin Johnson Password security is already becoming a thing of the past with biometrics taking their place. For instance, fingerprint identification is being built-in to every new Apple mobile device, thus forcing the rest of the herd to follow. Even retinal scanners are becoming common in corporate settings, when in the past their expense was only justified by high-security areas like An ultrasonic fingerprint sensor on a board here measures a three-dimensional (3D) volumetric image of the finger’s surface and the tissues beneath--making it near impossible to defeat. (Source: University of California). the White House, the Central Intelligence Agency (CIA) and the National Security Agency (NSA). Now, however, academic researchers sick-and-tired of memorizing long passwords and bolstered by the fact that even Captcha is no longer secure, have invented a 3-D fingerprint scanner that is not only immune to false-negatives due to oil or moisture on the skin, but even looks beneath the surface of the skin, to create an ultra-secure identification system that could make passwords a thing of the past. “In terms of robustness, the ultrasound sensor is less prone to errors due to dry/wet/oily fingers since it can image the dermis (beneath the surface) rather than just the epidermis,” Professor David Horsley (University of California Davis) told EE Times. He is also co-director of the Berkeley Sensor and Actuator Center, along with co-director professor Bernhard Boser at the University of California at Berkeley. “Secondly, conducting fingerprint recognition from 3D features makes these images harder to spoof, since you need to create a 3D model of the finger to reproduce them.” Today a determined hacker can lift your fingerprints from any glass you touch, using the same methods that the police do to identify criminals, making it relatively easy to reproduce that image of a 2D fingerprint and spoof a device protected that way. Not so with a 3D fingerprint that looks beneath the skin with ultrasonic microelectromechanical system (MEMS) sensor. “With a 3D fingerprint, the subsurface features are private,” Horsley told us. To prove the concept, Horsley’s research team collaborated with Invensense Inc. (San Jose, California), using Invensense to fabricate the device using its Invensense shuttle service which gives MEMS developers access to its patented MEMS-on- CMOS Nasiri fabrication toolkit. “Invensense provided the fabrication service. We used a modified version of their NF Shuttle which is a multi-project wafer (MPW) service,” Horsley told us. “They also provided funding to our students through a collaboration membership at our research center, the Berkeley Sensor and Actuator Center (BSAC).” The project built on the Berkeley Sensor and Actuator Center’s previous success with piezoelectric micromachined ultrasonic transducers (PMUTs) from which it spun out the commercial The various layers, vias and other structures that make the 3D microelectromechanical system (MEMS) fingerprint detector to its underlying CMOS ASIC. (Source: University of California). company Chirp Microsystems Inc. (Berkeley, California). Using its MEMS-based PMUTs to analyze the returning ultrasonic echoes, the Berkeley Sensor and Actuator Center was able to fabricate the 3D fingerprint scanner prototypes on an Invensense wafer whose Nasiri process bonds the MEMS wafer to the ASIC wafer to seal the former from contamination. Currently the project is still in the research stage, but a second prototype that improves the performance of the first generation device is taking the project closer to commercialization. “We’re testing a 2nd generation chip that is closer to the commercial requirements. I expect we’ll have a new announcement this fall,” Horsley told us. Horsley also thinks the technology has medical applications in imaging for personal health monitoring. And since the PMUTs are so well matched, they could also be used in arrays. A scanning electron microscope (SEM) image show the integration of the MEMS layers with the underlying CMOS electronics. (Source: University of California). 16 Electronic Engineering Times Europe September 2015 www.electronics-eetimes.com


EETE SEP 2015
To see the actual publication please follow the link above