Screen printing: a technology for the batch fabrication of integrated chemical-sensor arrays

Abstract

The commercialization of integrated chemical sensor has been slowed by the difficulty of device encapsulation and membrane application. For reasons of both cost and reproducibility, the sensor-specific structures should be mass fabricated, as are the microelectronics. The challenge lies in merging the standard semiconductor process sequence with the non-standard steps used to form the transducers. We demonstrate that screen printing can be used to partition the fabrication into two distinct sequences, semiconductor processing and sensor-specific steps. This simplifies process development and evolution, and makes semiconductor foundry services available for manufacturing sensors. After conventional semiconductor processing, our wafers have silver epoxy contacts screen printed on the aluminum sensor pads; the silver forms a stable chemical interface to the membranes, and the epoxy makes a strong physical bond to them. Next, the polymeric membranes are applied and patterned with screen printing. Membranes of different compositions can be deposited on the various sites of a multisensor chip by simply repeating the screen print/cure cycle. We show that the electrochemical performance of mass-fabricated passive and active sensor arrays is comparable to that of conventional liquid-junction ion-selective electrodes.