: Eichholz, J.; Langerbein, A.; Manoli, Y.; Mokwa, W.; Kersjes, R.A.

Abstract
Invasive measurements of physical parameters in blood are very important for the intensive care. The integrated flow sensors presented here has been developed as a part of an "intelligent catheter" for measuring certain blood parameters. The sensor is based on the principles of hot-film anemometry. The temperature difference on a chip is measured by two diodes. One diode is heated by means of a polysilicon resistor in close proximity. This diode is (for thermal insulation) placed on a 5 mym x 260 mym x 260 mym silicon membrane. For the membrane formation the implanted oxide layer of SIMOX substrates (Separation by Implanted Oxygen) was used as a stop for backside etching. This technique allows batch processing and is compatible with a standard CMOS process. In addition, electronic CMOS devices can be mounted directly into the membrane. Switched capacitor circuits are used for sensor read-out electronics.