Chemical multi-sensor arrays for liquids monolithic integration using microelectronic technology

The need for chemical sensor systems is expanding rapidly. By employing an array format the sensor systems with different sensor materials might be more generic and also more universal in their applications. The peculiarity of such array-based systems is that utilizing already available signal processing schemes and pattern recognition methods, it is possible to characterize an analytical sample as a whole. This means that a sensor array development should be application driven and sensitive materials, as well as types of transducers comprising the array, should be considered for each application. Microelectronic technology has large experience in fabrication of chemical sensors based on ion-selective field effect transistors (ISFET) and other types of transducers, like amperometric or conductimetric, utilising thin film technology. Though large ISFETs arrays have been reported (T. Yeow et al. Sensors and Actuators B 44 (1997) 434-440) they are produced on the same silicon substrate that prevents simultaneous measurements of all the devices. To resolve this problem complementary metal-oxide semiconductor (CMOS) technology was proposed to isolate individual ISFETs by a p-n junction (S. Martinoia et al. Biosensors and Bioelectronics 16 (2001) 1043-1050); but this results in high leakage currents and cross-talking of sensors that shows that they must be isolated. The latest achievements in microelectronic micromachining gave rise to production of new starting materials like BESOI (silicon on insulator) that can be used as a base for the development of a liquid multi-sensor array containing different types of chemical and physical sensors and that permit to integrate NMOS and thin film technologies.