Electronic Design

Biometrics Boost Security

Through the employment of biometric sensors for user ID and authentication, secure applications like ATMs are entering a new age. A computer mouse is already available with an integrated fingerprint sensor. Today, two different fingerprint sensors are on the market: the TCVS1A from STMicroelectronics and the Fingertip Sensor from Infineon Technologies AG. Both chips work with CMOS capacitive active pixel-sensing technologies.

While the TCVS1A sensor has a size of 12.8 by 18.0 mm, the Fingertip Sensor is 11.1 by 14.3 mm. STMicroelectronics' 256- by 36-pixel array offers an image resolution of 508 dots/in. Infineon's sensor has an active area of 224 by 288 pixels and a resolution of 513 dots/in. The TCVS1A chip needs 20 mA in the active mode, 7 mA in the standby mode, and 1 mA in the sleep mode. The Fingertip Sensor consumes 50 mW in the operating mode and less than 5 mW in the sleep mode. Furthermore, both companies provide evaluation and software development kits.

In addition, the Fingertip Sensor is ESD-protected up to 12 kV. A next-generation chip, which the company expects to be 10µm thin, will survive up to 50 kV. "Such a chip allows it to be bent and placed on a chipcard, even though the chip is bigger than 25 mm2," explains Ulrich Haman of Infineon.

Available silicon chips, like those mentioned here, can be integrated into final products. Other biometric sensors, such as iris-recognition chips or DNA-sensing devices, are undergoing development too.

Furthermore, polymer-based CHEMFETs (ion-sensing FETs or ISFETs) are under development at IMEC in Belgium. For example, this company has developed organic semiconductors that allow the realization of proton-sensing FETs—a perfect solution for ph sensing (see the figure). But, one problem with this type of sensor is its drift characteristics. "We will have good prototypes in about three years," projects Andrew Campitelli of IMEC's biosensors group. "From a technology point of view, volume products can be available in five to ten years from now. Biosensors also can provide the kickoff for molecular-based electronics," Campitelli adds.

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