SCREEN PRINTING - A TECHNOLOGY FOR THE BATCH FABRICATION OF INTEGRATED CHEMICAL-SENSOR ARRAYS

The commercialization of integrated chemical sensors has been slowed b y the difficulty of device encapsulation and membrane application. For reasons of both cost and reproducibility, the sensor-specific structu res should be mass fabricated, as are the microelectronics. The challe nge lies in merging the standard semiconductor process sequence with t he non-standard steps used to form the transducers. We demonstrate tha t screen printing can be used to partition the fabrication into two di stinct sequences, semiconductor processing and sensor-specific steps. This simplifies process development and evolution, and makes semicondu ctor foundry services available for manufacturing sensors. After conve ntional semiconductor processing, our wafers have silver epoxy contact s screen printed on the aluminum sensor pads; the silver forms a stabl e chemical interface to the membranes, and the epoxy makes a strong ph ysical bond to them. Next, the polymeric membranes are applied and pat terned with screen printing. Membranes of different compositions can b e deposited on the various sites of a multisensor chip by simply repea ting the screen print/cure cycle. We show that the electrochemical per formance of mass-fabricated passive and active sensor arrays is compar able to that of conventional liquid-junction ion-selective electrodes.