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Abstract-The design, fabrication, and measurement results for a diaphragm-based single crystal silicon sensor element of size 820 µm × 820 µm × 500 µm are presented. The sensor element is designed for in vivo applications with respect to size and measurement range. Moreover, it is optimized for longtime operation in the human body through a built-in protection preventing biofouling on the piezoresistors. The sensitivity is about 20 mV/V for a change from 500 to 1500 mbar absolute pressure. This result is comparable to conventional sized micromachined pressure sensors. The output signal is not found to be influenced by exposure to 60 °C for three hours, a normal temperature load for a typical sterilization process for medical devices (Ethylene Oxide Sterilization). The hysteresis is low; < 0.25% of full scale output signal. The sensor element withstands an overload pressure of 3000 mbar absolute pressure. Observed decrease in the output signal with temperatures and observed nonlinearity can easily be handled by traditional electronic compensation techniques.

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High-density through-wafer interconnects are of great interest for fabricating real 3D microsystems. A complete solution for realizing through-wafer interconnects is presented. The proposed solution is believed to be cost effective and easy to integrate in a device process flow. A deep reactive ion etch process was developed to etch 20 × 20 µm2 via holes through 300 µm thick silicon wafers. Thermal oxide is used to insulate the vias from the bulk silicon and heavily doped polysilicon is used as the conductor. Aluminum metallization is provided on both sides of the wafer. The electrical resistance of a single through-wafer via is close to 30 Ω.

Sensitive and selective gas measurements are crucial for a large variety of applications. This paper describes the manufacturing and characterization of a photoacoustic gas sensor system. The system is based on a pressure sensor element with a sensitivity of 10 V/V/Pa. To demonstrate and evaluate the concept, 12 prototypes for measuring CO 2 have been manufactured and characterized. Detection limits ranging from 92 ppm to below 6 ppm CO 2 were obtained with a path length of 10 cm, depending on the measurement time and photoacoustic cell design. Measurements showed no cross-sensitivity towards CO, CH 4 , or humidity in any of the sensors. The temperature drift of the uncompensated raw signal of two sensor designs was below 117 ppm CO 2 in the range from 25 C to 50 C.Karl-Heinz Suphan began his career in 1981 as Engineer for R&D of hybrid circuits. In 1992, he joined Micro-Hybrid Electronic GmbH, Hermsdorf, Germany, and realized different projects in special applications of hybrid thickfilm technology. In 2000 he became a Senior Project Manager R&D. In this role, he is responsible for customer specific developments and technological projects.Dag T. Wang received the Ph.D. degree from the Norwegian University of Science and Technology in 1997 for work on disorder in semiconductors.He is currently a Chief Scientist at the Department of Microsystems and Nanotechnology at SINTEF, Oslo, Norway, specializing in design and fabrication of MEMS-based sensors. fields of expertise are within microsystem technology (MST), MEMS design with a special focus on gas sensor, bioMEMS, and fingerprint sensors. He is currently the CTO of the Norwegian company IDEX ASA supplying fingerprint sensor technology, and he holds a part-time adjunct professor position at NTNU.

Anodic bonding of glass to aluminium may provide a higher degree of freedom in device design. In this paper, a systematic variation of the bonding parameters for the aluminium-glass bond is presented. Hermetic seals with strengths of 18.0 MPa can be achieved using a 50-100-nm-thick bonding aluminium layer, and bonding at 300-400°C applying a voltage of 1,000-1,500 V for 20 min. With these parameters, bond yields above 95.1% were obtained on 17 wafers. The bonds survived extensive thermal ageing without significant degradation. The possibility of bonding glass to an aluminium layer with buried, electrically isolated conductors underneath is also demonstrated.

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